(X) or (H) PIPE

[grumpyvette]

INSTALLING AN (X) PIPE IN THE EXHAUST ON A DUAL EXHAUST CAR

Magnaflow sells them in stainless:
https://www.magnaflow.com/products?partNumber=10782

Dynomax (aluminized):
Dynomax 88328: X-Pipe Outer diameter: 3" | JEGS

Flowtech (aluminized):
Flowtech 53621: FlowTech Exhaust X-Pipe 3" | JEGS
http://pypesexhaust.com/p-13194-dyno-tests.html

https://www.summitracing.com/parts/sum-640701

https://www.summitracing.com/parts/cse-14173

just having your own MIG or better yet TIG welder,
and having learned the skills to use it correctly,
can save you hundreds of dollars in EVERY ,
exhaust system install

adding an anti-reversion baffle to a 18"-24" longer collector on open headers with the internal pipe about 1/2 the collector length tends to help scavenging on some engines, no header will function to full efficiency with any significant back pressure so take the effort to accurately measure any restriction to exhaust flow AT your upper rpm range of your engines power band and be darn sure its not choking your power curve.

http://www.wallaceracing.com/intake-runner-length.php

http://www.bgsoflex.com/intakeln.html

http://www.velocity-of-sound.com/velocity_of_sound/calculator3.htm

http://www.velocity-of-sound.com/velocity_of_sound/velocity_stacks.htm

http://www.swartzracingmanifolds.com/tech/index.htm


Hot rod (oct. 2000)

355 SBC
9:1
trickflow alum heads
2.02''/1.06'' valves
comp magnum 286 hyd. cam (236/236 deg @ .050'', .490''/.490'' lift, 110 lsa)
edelbrock performer rpm intake
demon 750 cfm carb
3'' dual pipes
flowmaster "big block" mufflers
hooker 1-5/8'' long tube headers

Headers Headers with X-pipe
RPM HP TQ RPM HP TQ HP gain TQ gain

3000 219.8 384.7 3000 231.2 404.7 11.4 20.0
3100 224.5 380.4 3100 235.3 398.7 10.8 18.3
3200 229.7 377.0 3200 242.6 398.2 12.9 21.2
3300 234.6 373.4 3300 252.0 401.0 17.4 27.6
3400 240.1 370.9 3400 262.1 404.9 22.0 34.0
3500 246.5 370.0 3500 271.2 406.9 24.7 36.9
3600 255.5 372.8 3600 280.5 409.3 25.0 36.5
3700 269.1 381.9 3700 290.3 412.1 21.2 30.2
3800 283.8 392.3 3800 300.3 415.0 16.5 22.7
3900 295.5 397.9 3900 308.6 415.6 13.1 17.7
4000 307.6 403.9 4000 317.4 416.7 9.8 12.8
4100 320.7 410.8 4100 326.9 418.8 6.2 8.0
4200 332.6 415.9 4200 337.0 421.4 4.4 5.5
4300 343.5 419.5 4300 345.7 422.2 2.2 2.7
4400 351.8 419.9 4400 352.9 421.2 1.1 1.3
4500 358.7 418.7 4500 358.7 418.7 0 0
4600 362.5 413.9 4600 363.7 415.2 1.2 1.3
4700 367.1 410.3 4700 369.5 412.9 2.4 2.6
4800 371.2 406.2 4800 375.8 411.1 4.6 4.9
4900 374.8 401.7 4900 380.1 407.4 5.3 5.7
5000 376.7 395.7 5000 381.8 401.1 5.1 5.4
5100 378.2 389.5 5100 381.1 392.5 2.9 3.0
5200 380.8 384.6 5200 381.5 385.3 0.7 0.7
5300 383.8 380.4 5300 384.0 380.5 0.2 0.1
5400 387.0 376.4 5400 387.7 377.0 0.7 1.4
5500 390.0 372.4 5500 391.9 374.3 1.9 1.9
5600 394.8 370.3 5600 395.6 371.0 0.8 0.7
5700 397.2 366.0 5700 400.0 368.6 2.8 2.6
5800 397.1 359.6 5800 402.9 364.9 5.8 5.3
5900 393.3 350.1 5900 401.2 357.2 7.9 7.1
6000 388.0 339.6 6000 394.8 345.6 6.8 6.0



peak HP gain 25.0 @ 3600 rpm
peak TQ gain 36.9 @ 3500 rpm

AVG. HP from 3000-6000 rpm 7.99
AVG. TQ from 3000-6000 rpm 11.1

AVG. HP from 3000-4500 rpm 25.8
AVG. TQ from 3000-4500 rpm 17.2
71RS/SS396
exhaust gas flow is never constant it comes in pulses that vary in pressure , some what in volume and ignition timing changes or duration as the rpms change, thus the ideal cross sectional area required in the exhaust header and exhaust pipe,
for a given engine displacement and rpm also varies
your also dealing in most cases with an un-equalized firing order where each cylinder bank does not always alternate equally.
thus two properly sized exhaust headers blending and flowing into an x-pipe to dual exhaust beyond will generally provide a slight improvement over a single merged exhaust.
two blended exhaust paths of total equal cross-sectional area at least, in theory, allow for maintaining a marginally higher gas flow speed increasing cylinder scavenging energy

http://garage.grumpysperformance.com/index.php?threads/calculating-required-exhaust-pipe-size.11552/
http://garage.grumpysperformance.com/index.php?threads/x-or-h-pipe.1503/
http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/
http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/
http://garage.grumpysperformance.co...-03-12-with-wave-action-analysis.15764/page-2

theres a good deal of info here in the sub links that might help, including some dyno results
btw, learning to welds , a bit like GREAT SEX, if youve never been involved you don,t see the advantages but once you are, you wonder how you could ever have gone without having constant access!
(and an exhaust system is a great place to learn)

These three circles illustrate the difference in internal square-inch area between 2.25-, 2.50-, and 3-inch exhaust pipes. Weâve calculated the area based on a wall thickness of 0.065. The 2.25-inch pipe has a flow area of 3.80 square inches, a 2.5-inch system increases the area 25 percent to 4.7 square inches, and a 3-inch pipe pumps the area up to 6.8 square inches.

Understand the different concepts ,adding an (X) pipe effectively doubles the exhaust cross sectional area , as your effectively allowing both sides of the dual exhaust to carry only half the flow that the single side of the exhaust can flow, this is cutting the resistance to exhaust flow restriction nearly in half and increases scavenging, this blends and smooths the exhaust flow, remember you get a pulse of exhaust every 90 degrees of engine rotation,
Since V8’s fire unevenly, exhaust exits in pulses rather than a steady flow. While one pipe is filled with pressure the other pipe is at far less , or lower pressure, or relatively low pressure.
but the connecting of the two pipes in a Siamese pattern with an (X) pipe allows pressure to be released to and equalize to the other side, this instantly doubles the exhaust cross section and blends the pulse,and reduces flow restriction,. This action allows the exhaust to pass through the pipe quicker and this better ‘breathing’ increases horsepower, but it also effectively extends the low pressure at the other exhaust ports if the length is correctly calculated or tuned. THUS a properly set up exhaust can SCAVENGE the cylinders increasing intake flow efficiency significantly.
the "drone, sound you hear with some exhaust systems " has a great deal too do with muffler PLACEMENT and pipe diameter,and distance from the header collectors and use of an (X) pipe or (h) PIPE placement ,AND MUFFLER DESIGN USED, all of those factors will effect the rpm level or frequency that "DRONE" may occur at with almost any exhaust, ADDING AN (x) PIPE OR ADDING A SECOND (x) PIPE OR MOVING ITS LOCATION OR ADDING LENGTH TO THE TAIL PIPE CAN OFTEN REDUCE OR ELIMINATE THE DRONE IN AN OBJECTIONABLE RPM RANGE

Id also point out that cam timing matched to the exhaust scavenging has a huge effect on potential intake flow rates

HERES A GOOD EXAMPLE OF A CUSTOM FABRICATED EXHAUST

looks like a well done job CONGRATS!
heres a video of it,running
http://www.youtube.com/watch?v=EGqRfsqf ... e=youtu.be

If your looking to reduce noise installing several x-pipes in series, blends and reduces the exhaust pulse strength,yes Im sure it could, if theres enough physical real estate under the car, or truck ,available to allow it to be installed,
but I found a full length 3" exhaust with just two 3" X-pipes mounted as close as you can get them too the header collectors

x-pipes like this in series and, two 3" inlet and dual outlet ,
mount the mufflers as far back as you can and be sure to have the tail pipes exit past the cars bumper and point back and downward at about a 45 degree exit

low flow restriction mufflers does a reasonably good job at reducing the sound levels

that adding just two, 3" x-pipes in close series does make a significant difference in noise levels , is well proven, if you could fit 3 that would certainly not hurt.

http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/

spacing, of the second (X) cross over in a dual (X) 3" exhaust, is generally not extremely critical,
but I generally try hard to get it in the 18"-to-22" range as I found that seems to work best,
obviously under the car clearance effects your options

DUAL X-PIPES TEND TO RESULT IN MORE EFFECTIVE CYLINDER SCAVENGING,BY BLENDING EXHAUST PULSE DURATION, AND A BROADER TORQUE CURVE AND MELLOWER EXHAUST TONE
I did dual x pipes similar too this picture , on four different muscle cars and corvettes so far with good results,it tends to mellow the tone noticeably

http://www.hotrod.com/how-to/engine...y-horsepower-but-which-is-best-for-your-ride/

http://www.summitracing.com/parts/sum-642030

http://garage.grumpysperformance.co...or-tube-to-reduce-stop-drone.7590/#post-25712

http://static.summitracing.com/global/images/instructions/sum-642025.pdf
one more in an endless list of reasons you NEED a good MIG or TIG WELDER
in an ideal set up the exhaust system beyond the header collectors has a very low restriction to flow, and there will be an (X) pipe to effectively double the exhaust cross sectional area to significantly lower resistance to exhaust flow restriction still further, to increase the header,s ability to scavenge the cylinders efficiently in the intended power & rpm band, keep in mind your goal is or should be in most cases to maximize the torque in the intended rpm range that your engine combo produces.
every change you make, or part you select either enhances or restricted the engine power potential, at some point in the power band[/b]

WATCH THIS VIDEO
http://www.youtube.com/watch?v=yMyKv_P8 ... re=related

viewtopic.php?f=60&t=77

http://www.circletrack.com/enginetech/c ... ewall.html

viewtopic.php?f=60&t=1594

http://www.spintechmufflers.com/x-pipes ... t_139.html

http://www.carcraft.com/techarticles/ex ... index.html

http://www.pontiacstreetperformance.com ... haust.html

viewtopic.php?f=60&t=72

viewtopic.php?f=56&t=1166

http://metalgeek.com/static/cope.pcgi

http://www.pontiacstreetperformance.com ... haust.html

viewtopic.php?f=56&t=1503

a simple basic exhaust system like these 3" pipes bolted to the header collectors, and leading too an (X) pipe and dual 3" or -3.5" dual mufflers can produce excellent results if you have room under the car

an (x) pipe effectively reduces the flow restriction by increasing the cross sectional area of the exhaust system, and by BLENDING the individual exhaust pulses,remember a cylinder fires every 90 degrees of engine rotation, meaning the pressure and volume in the exhaust comes down the exhaust in pressure waves, thus an (x) pipe splitting and blending the pulse pressure wave is effectively reducing the strength and noise levels, as the gasses rapidly expand to double the previous pipe cross sectional area, and by reducing the pressure, velocity and resistance to flow in each side of a dual exhaust, an (H) is LESS effective , because it doesn,t blend the exhaust pulse it only allows the pressure to equalize to some extent, between the two sides of the engine, but its not nearly as efficient at reducing the pressure difference but its still an improvement over having no connection between cylinder banks, it should be obvious that having a PROPERLY tuned exhaust header mounted between the cylinder heads and (X) pipe and exhaust pipe sizes matching the displacement and intended rpm range of the engine will increase cylinder scavenging

http://www.pontiacstreetperformance.com ... aust3.html

SHORT H PIPES LIKE THIS ONE ABOVE that are full pipe diameter are FAR more effective than longer cross over versions, (LIKE THE LONGER H-PIPE BELOW)but they still don,t blend the exhaust gas pulse inertia nearly as effectively as a true (X PIPE)

http://www.mustang50magazine.com/techar ... index.html

http://www.automedia.com/Exhaust_XPipes/pht20011101xp/1

http://www.superchevy.com/technical/eng ... index.html

http://www.boyleworks.com/ta400/psp/exhaust3.html

viewtopic.php?f=56&t=495

http://www.burnsstainless.com/crossoversmain.aspx

there are mufflers with internal x pipe designs

placing two 3" x pipes in sequence seems to work well at both mellowing the exhaust note, and increasing the exhaust scavenging of the cylinders as it blends and smooths out the exhaust flow by allowing the individual cylinder pulse strength to dissipate rapidly, the first (x) reduces flow restriction, the second allows the exhaust pulse to run into itself further disrupting the individual pulse strength


READ THRU ALL THE SUB LINKED INFO IN THIS THREAD ALSO

viewtopic.php?f=56&t=185&p=219#p219

http://home.flash.net/~ivc1/cobra/xpipes.html

keep in mind installing an (X) almost increases the effective cross sectional area,of the dual exhaust ,to double what it had been behind a single header collector, by doubling the area that the exhaust flow sees, dropping the restriction to flow almost in half

buy this TOOL and custom fit the (X) INTO YOUR EXHAUST SYSTEM youll want to use a decent welder but its fast and a no-brainer AS LONG AS YOU REMEMBER TO CAREFULLY MEASURE BOTH THE (X) AND THE PROPOSED OPENING TO BE CUT,BEFORE CUTTING AND HAVE THE (X) BE A BIT LONGER THAN THE OPENING BETWEEN THE OLD PIPE WHERE ITS INSTALLED FOR AN OVERLAP NOT A BUTT WELD

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?function=Search

ITEM 37354-9VGA

$10.99 YOU CAN,T AFFORD NOT TO HAVE THIS TOOL IF YOU DO EXHAUST PIPE MODS, PERSONALLY I LIKE AN OXY-ACETOLENE TORCH FOR THIS TYPE WELD BUT ALMOST ANY WELDER WILL WORK, this is one area those little 110 volt migs are great for!

http://www.autoanything.com/exhausts-mufflers/69A2672A0A0.aspx

http://store.summitracing.com/partdetail.asp?autofilter=1&part=MPE-10792&N=700+115&autoview=sku

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HED-18830&N=700+115&autoview=sku

http://www.edelbrock.com/automotive_new ... ipes.shtml

WHY INSTALL AN (X)???
The lower your restriction to exhaust flow the better, past the headers collectors
An (X) basically allows BOTH sides of your exhaust system to share and split the exhaust flow, a 3” pipe has approximately a 7 sq inch cross section, splitting the flow doubles the area and tends to reduce the back pressure a good deal as your now using 14 sq inches vs 7” to allow the gases to both expand and cool, remember as hot exhaust gases cool the volume shrinks, and an added benefit is a mellower exhaust tone.
exhaust flow is NOT constant its in pulsed slugs as the piston on the exhaust stroke and the high pressure in the cylinder try to rapidly exit the cylinder of the previously burn fuel/air mix, if the headers are designed correctly the previous rapidly exiting mass tends to drag the next intake charge into the cylinder and a small percentage out the exhaust, thus clearing and filling the cylinder for the next compression stroke.
yes I strongly advise upgrading a corvettes exhaust on a performance build to 3" from the header collectors and back!most guys I talk and deal with,seem to think that slapping a set of headers on their car is all that's required to boost performance....ANY HEADERS! ...and they fail to realize that both the header design and the exhaust system behind them require a good deal of thought if you want the maximum benefits, and that simply hooking a restrictive exhaust system to the collectors on the best headers will negate most of their potential benefits.
most commercial headers are designed mostly for ease of manufacturing and ease of installation,little thought goes into maximizing the cylinder scavenging which is their main function.
your fooling yourself if you think headers will provide a big boost in hp/tq without the low restriction exhaust behind them,and in most cases that requires a larger diam. exhaust system and adding an (X) to the system and extending the header collectors at their full diam. up till at least the exit of the (X) so the twin exhaust pipes cross sectional area can provide that reduced restriction to flow, rather than the reducers many guys install to the collector exits to adapt them to the stock exhaust system.

With an 'X' type crossover arrangement, design ( the angle of convergence, tubing cross sectional size, volume, or area where they converge) and placement or distance from the header collectors are very important. If possible, an 'X' type crossover should be placed at the exact point in the system (measured length) that you would terminate tuned collector length in an open header system having no mufflers nor tailpipes, as the correctly sized (x) provides a sudden reduction in restriction similar to having open header collectors exit to the open air in some respects

heres a great example of really crappy quality install, done by a muffler shop ,and one reason an (H) pipe that is not installed correctly will tend to have a rather bad reputation, as too equalizing the exhaust flow rates or pressure, keep in mind at higher rpms you might easily have 50 exhaust pulses per second, making an (H) pipe all but useless,, especially if the connecting passage is far smaller than the pipe diameter, while a properly installed (X) pipe blends the pulses very efficiently

(H) PIPE

example of a well laid out exhaust (MELROSE)

on most SBC or LS based high performance engines of at least 350 cubic inches, designed to exceed 400 hp, the GREEN ARROW primaries should be 1 3/4" and at least 33 -38" long the RED ARROW or exhaust will usually perform well with a 3" diameter

if you look closely youll see the major difference is how easily exhaust flow pulses can move into the adjacent pipe to balance flow, the (H) pipe requires two 90 degree turns while the (X) pipe can easily balance with only part of a pulse expanding as it passes the (X) PIPE) merge point, the ease in balancing pressure, and reducing restriction greatly favors the (X PIPE DESIGN)

notice the X pipe design has several variations, the type above is more effective than the type below at blending and equalizing the pulse volume from either side but even the more restrictive version below still works well.

heres a good example showing why an (X) pipe is very efficient at equalizing and blending exhaust pulse flow rates

Heres a fairly standard (H) pipe exhaust lay out (above)
one lesson most guys don,t usually learn right away, that I constantly try to point out is that buying a few CAREFULLY SELECTED,QUALITY COMPONENTS usually is a far better route to take when building an engine than buying a greater number of lower quality components, like a decent roller cam, heads and a good low restriction exhaust

but even that system could be hurt if you slap restrictive mufflers on it

bjhines posted these and their good examples
looking thru an (X) pipe

mocking it up, this type of (X) pipe generally provides a noticeable reduction in the restriction to flow that helps hp

http://www.fordmuscle.com/archives/2000 ... ndex.shtml

1. 
   
   
   
   
   
   
   h-pipes are no where near as efficient or effective at equalizing or reducing individual, bank to bank exhaust pulse strength,or reducing the restriction to exhaust flow, as a similarly placed (X-pipe )
   if you have the room two (X-PIPES in sequence have been repeatedly been tested,
   and repeatedly found to provide a minor but measurably better result in increasing cylinder scavenging and a mellower exhaust sound
   your not going to see any huge gains from either configuration, but a single (X-pipe generally produces a bit better and a wider torque curve ,
   and two x-pipes in series is not all that rare recently even on the higher end performance cars
   
   

"X Versus H
It's long been known that connecting the two sides of a dual exhaust system, shortly after the headers, increases power and reduces sound. However in a traditional "H" pipe,its mostly, only sound and pressure waves that cross through the connection. most of the Gasses take the route of lowest pressure, which is straight out the pipe, rather than making a 90 degree turn in to the H.
Indy and Nascar teams have been using "X" type crossovers for quite some time. In an "X" pipe the gasses from both cylinder banks actually pass through a common area. This not only provides the benefits of some sound wave cancellation, but also increases the scavenging effect, helping draw out spent charge from the combustion chamber.
So how much of an increase does an X gain over an H? It's hard to say, especially considering that every combination will yield varying gains. In theory an X will work better as rpms go up. Considering the Flowtech X-Terminator pieces are priced under $50; you're much better off getting that, rather than having a shop fab up a crude 'H' piece."


viewtopic.php?f=79&t=497

viewtopic.php?f=56&t=1730

read thru ALL the sub linked info in this thread, and ITS SUB LINKED THREADS
its not at all rare for a swap from 2.5"-to-3" exhaust on a sbc or mild bbc or from 3"-to-3.5" on a radical big block to add 5-15hp,OR MORE, depending on the restriction that was removed behind the collectors or exhaust manifolds, back pressure reduces the effectiveness of the exhaust cylinder scavenging, and once you tune the engine to take full advantage of that reduced restriction and better cylinder scavenging factor you get the full benefits that the reduced back pressure tends to provide.
keep in mind the lower rpm TORQUE LOSS thats occasionally reported is FREQUENTLY a tuning issue as the more effective scavenging tends to lean out the effective fuel/air ratio
what most guys don,t understand is that your results will depend to some degree on the cam timing and engine displacement, intake runner design, and the rpm range the engines run in,its the length and diameter. of the header collectors ,entering the point where the (X) or (H) is located AND the flow restriction in the exhaust system in the collectors and primaries that will effect the cylinder scavenging,and the restriction to exhaust flow rates BEYOND that point, that the mufflers provide that will effect the results, and some those factors will change as the rpms increase.
HAVING the ability to test the vacuum or back-pressure, at the x or h pipe and beyond, will usually give you some indication of the exhaust system efficiency, what your trying to do, in most cases is increase the volumetric efficiency of the engine thru more effectively scavenging the cylinder in your intended power band, by reducing the exhaust system back pressure at and beyond the (H) or (X) pipe by splitting high pressure pulsed flow from each collector into the lower restriction , blended flow into two exhaust, pipes sharing the flow which at least in theory cuts the restriction, past that point noticeably.
if you can increase the rpm range, that the cylinder scavenge effectively at, with a low restriction beyond the tuned collectors, thru higher volumetric efficiency in the upper rpm band, power tends to increase

viewtopic.php?f=56&t=495

http://www.superchevy.com/how-to/ex...y-horsepower-but-which-is-best-for-your-ride/

viewtopic.php?f=56&t=1730

viewtopic.php?f=56&t=789

http://garage.grumpysperformance.co...-descriptions-dont-tell-you.12357/#post-61139

here above is a rather typical (X) pipe, the exhaust pressure pulse splits its flow and significantly reduces back pressure as the pulse enters the (X) as its effective cross sectional area almost DOUBLES , dropping that back pressure almost in half at that point, which usually increases cylinder scavenging potential of tuned headers, and increasing higher rpm power if used, and usually reducing noise as the frequency is disrupted, inducing a mellower tone.

EXHAUST flow is not at a constant pressure, its in pressure waves
an (X) and to a lesser extent an (H) pipe in an exhaust doesn,t BALANCE the flow, it effectively DOUBLES the area each separate PULSE of high pressure exhaust, in each cylinder, sees as its dumped into the collectors,each pulse in the header primaries introduces a high pressure wave into the collector as it enters the collector and introduces a low pressure reflective wave back up the header primary, if the size and length are correctly calculated that negative pressure reaches the exhaust port at time the exhaust valve from the next following exhaust cycle exits the cylinder to increase the scavenging of the cylinder ,helping to draw more of the intake charge from the intake runners during the overlap period and into the cylinder to increase volumetric efficiency in the intended rpm band.
in a correctly designed system the header collectors feed directly into the junction of the (X),or (H)at the same diam. as the collector diam., and only after the junction point is the exhaust pipe diam. reduced (IF THEN)
remember the goal is to increase the cylinder scavenging to increase the volumetric efficiency and thus extend the torque curve, by reducing back pressure and increasing the length and strength of the negative pressure wave that helps scavenge the cylinders, and that pulse helps draw in the intake runner charge of fresh f/a charge, as its fast exiting inertia drags the intake charge along with it.
in fact its not unusual for a correctly designed exhaust with a matched cam timing to draw a small percentage of the intake charge thru the intake and out thru the exhaust valve as the piston descends on the intake stroke during the cams overlap period.
The idea behind an exhaust header is to eliminate the exhaust manifold's back pressure. Instead of a common manifold that all of the cylinders share, each cylinder gets its own exhaust pipe. These pipes come together in a larger pipe called the collector. The individual pipes are cut and bent so that each one is the same or nearly the same length as the others. By making them the same length, it tends too guarantee that each cylinder's exhaust gases arrive in the collector spaced out equally so there is little or no effective back pressure restricting flow generated by the cylinders sharing the collector.

theres a great deal of info on the site about selecting or building headers, but one major factor is that a NON-RESTRICTIVE exhaust system MUST be installed with ANY HEADERS to allow them to work correctly. for headers to work correctly they require an exhaust pulse to allow its inertial energy to drag the following charge along with it out the exhaust.
if you can,t visualize that it might help to find a 3 ft long section of 2.5" pvc pipe and wrap a bit of tape around a full coke can so it slides easily thru the PVC, pipe but fills its interior diam., now place the pipe horizontally insert the coke can and drop the opposite end strait down while you hold your hand over the end the coke can was inserted into, as the mass of the coke can falls you'll feel air dragged with it , the same basic thing happens with an exhaust pulse, its mass is far less but its traveling much much faster, and depending on the rpm and displacement it does generate significant energy that can be used to draw the next intake runners charge into the cylinder as it draws out the next exhaust charge during the cams overlap duration (LOOK INTO CAM TIMING)
keep in mind the LENGTH of the header tube effects the rpm levels and energy transferred as it takes time for that mass of hot exhaust gas to travel thru the primary tube, naturally a longer distance tends to require a longer time and the longer duration tends to impart a longer and stronger negative pressure wave to assist the next pulse IF ITS TIMED CORRECTLY and the header primary tube is the correct diam. and length for the engines displacement,compression, cam timing, and several other factors, but again, it works far more effectively if the exhaust system is a low restriction design that doesn,t reduce the scavenging effect of the pulse waves, and the tubing is long enough to work effectively

viewtopic.php?f=52&t=1070

viewtopic.php?f=52&t=333

viewtopic.php?f=52&t=480

viewtopic.php?f=56&t=352

viewtopic.php?f=56&t=1166

http://www.slowgt.com/Calc2.htm#Header

http://www.bgsoflex.com/auto.html

these threads might help

http://www.pontiacracing.net/js_header_length1.htm

 

[grumpyvette]

ISKY CAMS POSTED THIS RELATED INFO

http://ocdspeed.com/product/x-pipe-universal-2-25/

Longer Exhaust Duration: Is this really necessary?

Most stock camshafts from American production V8, V6 and 4 cylinder engines manufactured today are ground with the longer exhaust lobe duration. Or, another way of looking at this is that they are ground with shorter intake durations! The former embraces the viewpoint that either the Exhaust Ports or Exhaust Pipe system is somewhat restrictive, and is in need of an assist. The latter suggests that the intake system is rather efficient and cam timing can be trimmed back a bit with out much sacrifice in power, in order to maximize throttle response and cruising efficiency.

Take your pick here. There is no absolutely correct viewpoint - because both are probably true! In a stock engine running at conservative RPM levels, for the sake of overall efficiency, fuel economy and a quiet smooth running engine, this staggering of intake and exhaust duration is quite common and appropriate.

However, High Performance is another thing entirely. Change one factor, let's say in this case, the exhaust system (installing headers and larger pipes) and you have just negated in most cases, the need for that longer exhaust lobe. Now couple this change with a different intake system and camshaft and you have really scrambled the equation. But, wait just a moment. Why is it that so many people (racers & cam grinders alike) insist on running a cam with longer exhaust duration regardless of what equipment is employed? The answer is "habit". Most of them have been somewhat successful in doing it their way and will probably never change unless virtually forced by circumstances to do so.

Before we go any further however let's review what it actually is we are trying to do with an engine when we attempt to make more power. Our best result comes when we are cognizant of the fact that an engine is basically an air pump. We pump it in and out (although in a different form) and we have problems when one side or the other is restricted. Balance or the equilibrium or flow should be our objective, unless of course we are not trying to make more horsepower!

Example #1 (Oval track racing) Here, I have often observed that the most experienced drivers are those who are most likely to run a single pattern (equal on intake and exhaust duration) cam. Why? Because such cams always, I repeat always make more torque! These veterans have a more educated foot and greater experience in feathering the throttle in the corners. They can therefore, utilize the benefit of added torque, in the lower to mid RPM range, to their advantage.

Their counterparts, the younger drivers on the circuit, generally are not as experienced and may at times actually get "crossed up" in the corners especially with a lighter car or when they are learning the ropes. In their case, a longer exhaust duration is often the more appropriate choice. It will often help them to drive better, more "flat footed" if you will, without consequence. But please for the sake of accuracy, let us be truthful. The benefit comes from an actual bleeding off of low to mid range torque, which is always what happens when Exh. Duration is lengthened, not from any improvement. The improvement, (if any) would come because of an improvement in scavenging at the extreme upper end of the power curve and would usually be marginal at best. Yet the so-called "extra power" potential of a longer Exh. Duration cam is most often why they are touted - power most people are backing away from at the end of the strait away!

Example #2 (Drag Racing) At the drag strip it's a little different and I feel more honest. Here, racers have long enjoyed longer exhaust and longer durations across the board (If I may add specifically for the purpose of "killing" low-end torque) to keep the tires from too easily breaking lose. This has been successful and sometimes actually results in a slight increase in top end power - something you can actually use in drag racing since it is a full throttle endeavor through the lights. Keep in mind here though, it's quite possible that a longer duration cam overall would have done just as well or better. In other words if you needed that longer exhaust for top end, perhaps the intake could have benefited from such a lengthening as well.

One of my favorite expressions is how "The Drag Racing mentality has infiltrated the ranks of Oval Track". Many have crossed over and made the switch in the past 10-15 years and some have brought their preconceived notions about how to cam an engine with them. A few may actually read these concepts and if they do so will at least come away with a better understanding of what they are doing. On the other hand they also could find that this information might actually help their cars to run just a bit faster!

 

[grumpyvette]

Intake Restriction and Over Scavenging: "Waste not...Want not!"

It is certainly an over simplification to make the statement "that which is not wasted, should be inducted". However, in the case of restricted intake systems and in particular 2-BBL carb rules, it is not far off the mark. Engines with such restrictions are "choked off" to the point where they will not run much past 6500 RPM (if even that high) without dropping off sharply in power. You might have trouble running very fast yourself if someone had your windpipe choked down to say 50 or 60% of it's normal capacity. Under such conditions, would you volunteer to give blood at the Red Cross? Of course not, but without knowing so, racers often do the equivalent with their engines by running a camshaft better suited for a 4-BBL class! How So?

If you'll recall in last months tech tip: "Longer Exhaust Duration: Is This Really Necessary?" I discussed how, through habit, many racers and cam grinders alike are predisposed to running camshafts with longer exhaust durations, whether they need to or not! Well, in the case of restricted intake applications, if there was ever a situation in which you'd want to avoid the longer exhaust "trap" it's here! Especially the 8, 10, 12 or even longer degree spreads, I often discover people employing.

Use such a cam at you own risk - and don't be surprised to find that your exhaust temperatures are unusually high. Your headers in fact may even glow cherry red. There is a very good reason for this. Raw (unburned) fuel is burning "late" or in the pipe (header/manifold). You may have a good equilibrium of flow going here but there is just one problem. Much of what should be inducted into the cylinder is being scavenged out the exhaust! You see, although back pressure in an exhaust system can be restrictive, the only thing that could be even worse is a reduction of it to the point where you are now, in effect pulling a vacuum. In the case of an intake restriction, very slight back pressure is preferable to avoid "over scavenging".

Yes, Yes I know. You are probably thinking "what's wrong with a little scavenging?". Well, nothing if you can afford it. But with intake restrictions (either small 2-BBL carbs and/or restrictor plates) you must be very careful. You already have reduced intake potential and therefore simply cannot be cavalier about valve overlap and scavenging or you'll be way down on power and have those nice bright cherry red pipes to show for it! Case in Point: One racer who called me was in this exact situation and was running, not surprisingly, a 14 Degree longer exhaust duration. It was Friday afternoon and he needed a cam the next day for the last "points race" of the season and UPS had already picked up at Isky. "Too Bad" I said, "You don't have a set of those low ratio break-in rocker arms because they could really help in this case". " I do have some" he said "but they are only 1.2:1 ratio - is that okay?" I told him to use them (on his exhaust valves only of course) and he finished the race 2nd having come from the back of the pack. Later we made him the right cam so he could avoid this make shift approach.

Unfortunately, the symptoms are not always as obvious as in this case to allow for a speedy diagnosis. Also, it's not only longer exhaust duration that causes the problem. Although it is usually the primary offender, it is often coupled with too close a lobe separation angle of say 104 Degrees. A widening to 106 Degrees or preferably 108 Degrees (some go even wider) is usually prudent.

I am not absolutely dead set against a slightly longer exhaust duration in these cases as a 2-4 Degree longer exhaust lobe is permissible under some circumstances (if your running a completely stock exhaust system including mufflers for example). Each case is different, depending upon the equipment employed. I might even recommend shorter exhaust duration to some; if I feel they have "overdone" their exhaust ports and or exhaust system a bit. What matters is the end result and if you're out of balance on one side simply employ what I call the "Great Law of Compensation" to bring you back to that equilibrium of flow.

So, how can you tell if you may need to make some of these changes in your camshaft? Well, short of trying a lower exhaust rocker arm ratio, you can increase exhaust valve lash .004" - .008" temporarily to see if there is any improvement. You can also try and increase restriction (smaller headers or pipes, or in the case of open headers a longer collector) and simply observe the results. Remember, "One test is worth a thousand expert opinions". Keep this old axiom in your "tool box" and you'll be ahead of the game. How do you think Smokey's shop got to be "The best Damn Garage in Town" anyway? Yes, he had those country smarts, but his experiences in racing and his willingness to test are legendary!


Hot rod (oct. 2000)

355 SBC
9:1
trickflow alum heads
2.02''/1.06'' valves
comp magnum 286 hyd. cam (236/236 deg @ .050'', .490''/.490'' lift, 110 lsa)
edelbrock performer rpm intake
demon 750 cfm carb
3'' dual pipes
flowmaster "big block" mufflers
hooker 1-5/8'' long tube headers

Headers Headers with X-pipe
RPM HP TQ RPM HP TQ HP gain TQ gain

3000 219.8 384.7 3000 231.2 404.7 11.4 20.0
3100 224.5 380.4 3100 235.3 398.7 10.8 18.3
3200 229.7 377.0 3200 242.6 398.2 12.9 21.2
3300 234.6 373.4 3300 252.0 401.0 17.4 27.6
3400 240.1 370.9 3400 262.1 404.9 22.0 34.0
3500 246.5 370.0 3500 271.2 406.9 24.7 36.9
3600 255.5 372.8 3600 280.5 409.3 25.0 36.5
3700 269.1 381.9 3700 290.3 412.1 21.2 30.2
3800 283.8 392.3 3800 300.3 415.0 16.5 22.7
3900 295.5 397.9 3900 308.6 415.6 13.1 17.7
4000 307.6 403.9 4000 317.4 416.7 9.8 12.8
4100 320.7 410.8 4100 326.9 418.8 6.2 8.0
4200 332.6 415.9 4200 337.0 421.4 4.4 5.5
4300 343.5 419.5 4300 345.7 422.2 2.2 2.7
4400 351.8 419.9 4400 352.9 421.2 1.1 1.3
4500 358.7 418.7 4500 358.7 418.7 0 0
4600 362.5 413.9 4600 363.7 415.2 1.2 1.3
4700 367.1 410.3 4700 369.5 412.9 2.4 2.6
4800 371.2 406.2 4800 375.8 411.1 4.6 4.9
4900 374.8 401.7 4900 380.1 407.4 5.3 5.7
5000 376.7 395.7 5000 381.8 401.1 5.1 5.4
5100 378.2 389.5 5100 381.1 392.5 2.9 3.0
5200 380.8 384.6 5200 381.5 385.3 0.7 0.7
5300 383.8 380.4 5300 384.0 380.5 0.2 0.1
5400 387.0 376.4 5400 387.7 377.0 0.7 1.4
5500 390.0 372.4 5500 391.9 374.3 1.9 1.9
5600 394.8 370.3 5600 395.6 371.0 0.8 0.7
5700 397.2 366.0 5700 400.0 368.6 2.8 2.6
5800 397.1 359.6 5800 402.9 364.9 5.8 5.3
5900 393.3 350.1 5900 401.2 357.2 7.9 7.1
6000 388.0 339.6 6000 394.8 345.6 6.8 6.0



peak HP gain 25.0 @ 3600 rpm
peak TQ gain 36.9 @ 3500 rpm

AVG. HP from 3000-6000 rpm 7.99
AVG. TQ from 3000-6000 rpm 11.1

AVG. HP from 3000-4500 rpm 25.8
AVG. TQ from 3000-4500 rpm 17.2

http://garage.grumpysperformance.co...lsa-effects-your-compression-torque-dcr.1070/

more numbers for ya'll who like numbers.

All tests via an independent lab
All tests @ 15” wc

2 “ Straight Pipe 283 CFM
2 ¼ “ Straight Pipe 365 CFM
2 ½ “ Straight Pipe 521 CFM

2 ¼” Typical Bent tailpipe 268 CFM
2 ½” Typical Bent Tailpipe 417 CFM

2 ¼” Inlet/Outlet_ Glass Pack Tips- No Louvers- Smooth 274 CFM
2 ¼” Inlet/Outlet- Glass Pack Tips-Louvered 133 CFM
Same as above set for reverse flow 141 CFM
2 ¼” Cherry Bomb 239 CFM
2 ½” Cherry Bomb 294 CFM

2 ½” Inlet/Outlet Dynomax Super Turbo 278 CFM
2 ½” Inlet/Outlet Ultraflow Bullet 512 CFM
2 ½” Inlet/Outlet Gibson Superflow 267 CFM
2 ½” Inlet/Outlet Flowmaster ( 2 Chamber) 249 CFM
2 ½” Inlet Outlet Flowmaster ( 3 Chamber) 229 CFM
2 ¼” Inlet/Outlet Thrush CVX 260 CFM
2 ½” Inlet/Outlet Maremount Cherry Bomb 298 CFM
2 ½” Inlet/Outlet Hooker Aero Chamber 324 CFM
2 ½” Inlet/Outlet Hooker Max Flow 521 CFM
2 ½” Inlet/Outlet Borla Turbo 373 CFM
2 1/2" Inlet/Outlet Magnaflow 284 CFM

http://www.pontiacstreetperformance.com/psp/exhaust.html

Standard OEM 2 ¼” Inlet/Outlet 138-152 CFM
Standard OEM 2 ½” Inlet/Outlet 161-197 CFM

this may provide some perspective when designing your exhaust setups and choosing muflers.

 

[grumpyvette]

heres a good VISUAL shot to show why an (X) pipe is far less restrictive to balanced/ blended flow

BTW on my last BIG BLOCK C4 swap I had TWO 3" (X) pipes and got a bit creative and well built a DUAL (X) exhaust that was similar to this PICTURE BELOW. the result was a rather unique exhaust tone, a nice smooth rumble note in the sound and a very nice smooth low and mid rpm torque curve, now Im not sure if the exhaust mod added or subtracted from the power curve because I didn,t try it with a different exhaust config. but I got the strong impression that it helped, I know it made the sound distinctive and more mellow, bye having the exhaust pulse blending twice the scavenging effect in the cylinders seemed to noticeably increase efficiency, keep in mind the benefit of an (X) pipe is your effectively doubling the flow area and cutting the pulse strength into two roughly equal pulses, a second (x) allows those pulse to collide, further reducing potential noise and further smoothing flow in each pipe

http://www.jegs.com/i/Hooker-Headers/52 ... oreDetails

http://ocdspeed.com/product/x-pipe-universal-2-25/
The melrose exhaust is a very well designed system, and keep in mind the exhaust gasses travel to the rear and pass through the (X) pipe they dissipate HEAT and loose some pressure and volume as a result, the (X) tends to mellow the growl slightly also, thus the two exhaust pipes past the (X) pipe share the split flow ,thats now sharing twice the original exhaust cross sectional area, at a reduced restriction, if I had the cash available thats the route ID suggest going , then you just need a decent quality, low flow restriction set of mufflers, added to the exhaust
one of the better current c4 corvette exhaust system designs is made by www.melrosecorvette.com


when selecting an exhaust you can refer to the linked info for sizes, but
']a basic exhaust laided out similar to these pictures above with headers feeding 3" exhaust and an (X) pipe tends to provide excellent results, on most cars if matched to low restriction mufflers,keep in mind the idea is to reduce flow restriction and increase cylinder scavenging, thru the design.
']just remember the main goal is improved cylinder scavenging and low restriction to flow while reducing the noise level, in roughly that order but obviously theres compromises that are made due to clearances and noise ordinances
']a well thought thru design on an (X) pipe and cut outs
']keep in mind headers loose a great deal of their potential horsepower gains if there matched up to a restrictive exhaust
']
']
']
']
']
']btw adding an (H) pipe
']
']
http://www.jegs.com/i/Flowmaster/389/15921/10002/-1

']the question often comes up about use of mandrel bends vs crimp bent exhaust pipes, in designing an exhaust system, well it should be noted that its the cross sectional area much more than the shape of the pipe thats the more important factor, while its true that mandrel bends do maintain a more consistent cross sectional area, simply selecting a slightly larger diameter non-mandrel bent exhaust pipe size with its larger cross section can frequently be the less expensive route. as long as you've got an (X) pipe in the system and the tail pipes are nominally the same diameter IE lets say 2.5" or 3" the type of bend at that point will be all but meaningless due to the fact that by that point the exhaust pulse strength and velocity has been significantly reduced thru cooling distance, the effect of the (X) pipe splitting the pulse,and the lack of significant restriction.
']every test Ive ever seen shows that an (x) pipe mounted near the header collectors and mandrel bends on collectors do help flow, but youve effectively almost doubled the cross sectional area after the (x)and because the engine fires every 90 degrees the pulse of exhaust past the (x) is significantly reduced in exhaust pressure, your exhaust will normally require an exhaust pipe that will handle the flow based on the engines air flow rate and horse power
']you can use the info posted
']
']
']
']
']knowing a few constants in engine pressure and flow helps
']
']an engine usually requires approximately 2.257 cubic feet per minute per horsepower to maximize intake flow and exhaust flow at about 115 cfm per square inch
']
']so assuming your building a 500 hp engine / 2 (divided by 2 as there's normally two header collectors on a v8) we have 250hp per header collector, (open header collectors) multiply that by 2.257 cfm and you see you need 565 cfm and divide that by 115/square inches and we see we need a 4.9 square inch minimum exhaust collector pipe, per side (open header collectors).
']
']as a cross check 500hp /8=1129/8=142 hp per header primary , 2.257 x 142/115=2.76 sq inches 0r a header primary a bit larger than 1 3/4 and smaller than 2" or a 1 7/8 to maximize peak hp, per header primary, but keep in mind you'll spend most of your time below peak rpms so a slightly smaller 1 3/4" primary on a street strip engine that sacrifices a bit of peak hp for better mid rpm torque makes sense, and once you install longer exhaust pipes and mufflers you'll need to steep up the exhaust pipe size cross section past the header collectors or they will tend to be restrictive at the minimum size the formula predicts
']
viewtopic.php?f=56&t=1730&p=5392#p5392
http://www.grumpysperformance.com/.1280.1280.JPG[/img]
viewtopic.php?f=56&t=495
http://www.grumpysperformance.com/.1280.1280.JPG[/img]
viewtopic.php?f=56&t=1503

']
']
']just in front of the muffler entrance point can slightly further reduce noise and mellow the tone
']
']related info
']
viewtopic.php?f=56&t=1303
http://www.grumpysperformance.com/.1280.1280.JPG[/img]
viewtopic.php?f=56&t=495
http://www.grumpysperformance.com/.1280.1280.JPG[/img]
http://www.boyleworks.com/ta400/psp/exhaust3.html
http://www.grumpysperformance.com/.1280.1280.JPG[/img]
http://www.boyleworks.com/ta400/psp/exhaust.html

 

[grumpyvette]

http://www.wholesalemarine.com/p/MOE-02 ... nQod21jA7Q

spraying a corrosion reducing spray on your exhaust system welds with zinc chromate spray tends to significantly reduce the formation of rust on welds, this tends to extend your exhaust system life expectancy and is highly recommended after welding even on stainless exhaust welds.
IF YOUR WELDING STAINLESS USE A MINIMUM 16GA 18 GA is too THIN, FOR STAINLESS HEADERS OR EXHAUST PIPE, AND DON,T FORGET TO PURGE THE BACK GAS WHEN WELDING , and 321 is superior to 304 stainless
it would be difficult to over stress how important having the correct tools and the skill to use them are on modifying parts, frankly I can,t imaging a shop without some basics like a couple welders and a drill press and a belt sander, air compressor
and die grinders etc.

 

[grumpyvette]

Hey guys,

Have a '76 daily driver, approx 250k in 7 years. Only has Custom Image 1 7/8" headers and Edelbrock Performer RPM Air gap intake. Waiting to install Procharger later.

I recently had a true dual 3" exhaust made, no mufflers or cats. It was very loud, just what I wanted in sound. I had always read about X-pipes and such quieting exhaust a bit, but sound clips on YouTube made it seem very minor.

I was surprised when I started up the car after the X-pipe install. I used a Flowtech unit. Start up wasn't drastic, but all drone was gone. Can easily have a conversation inside now.

The sound is MUCH quieter.. Inside it is like a Corolla (seriously..) Outside it is no longer deafening as it was before, but the tone is deeper. It also sounds like it is revving much higher than it really is. 3500 RPM sounds like 5500.

I'm still waiting to see if I like it as much or not. No popping on decel, brap brap sound..

The main thing holding me back from removing it is the fact that it drives SO much better. Kick in the pants feel. Definitely more torque.

I'd liken the true dual to a Harley in loudness.. X-pipe not sure in loudness yet, but it isn't deafening in the least, even revving in underpasses.

Maybe it will grow on me more. Thinking of trying a different style of X-pipe as well, like the Magnaflow Tru-X. The Flowtech unit is similar to the Dr. Gas, NASCAR looking.

I'll upload videos soon. Unfortunately I never did a rev video with true duals, but have an idle one.

ADDING the (X) pipe reduces the EXHAUST flow restriction,by effectively doubling the internal pipe cross sectional area, and tends to INCREASE the cylinder scavenging efficiency,by blending the pulses effectively extending the low pressure scavenging the cylinders, plus it tends to mute, and smooth out and lower the noise levels and tone

http://garage.grumpysperformance.com/index.php?threads/c3-muffler.7806/#post-35279

https://www.holley.com/types/Maximum_Flow.asp

http://www.dynomax.com/mufflers?muffler ... ameter=171

http://www.jegs.com/p/Flowmaster/Flowma ... Ntt=744765

http://www.summitracing.com/parts/wlk-1 ... 7AodgW4AYg

http://www.summitracing.com/parts/sum-638270

http://www.summitracing.com/parts/pye-mvr70

I don,t know the size mufflers used ,theres dozens of similar ones sold by several manufacturers

 

[grumpyvette]

CORSA came out with a more efficient DUAL (X) PIPE exhaust and headers for the c7 corvettes, the increased scavenging effect of dual (X) pipes is something I've promoted for decades
MY c4 vettes exhaust looks similar to this

INSTALLING AN (X) PIPE IN THE EXHAUST ON A DUAL EXHAUST CAR

keep in mind that a properly designed exhaust system and headers goes a very long way towards increasing the efficiency of the intake manifold and head flow , and remember that the better the heads and the more effective the exhaust scavenging the less duration the cam used will require!
what goes in, needs to flow out with near zero flow restriction
Ive always been amazed at the number of guys who think the only options they have in components , they can use on a car, involve buying and installing parts listed in a catalog.
adding a dual (X) to the exhaust system has proven to reduce the decibel level and spread the torque curve on several corvettes, Ive done that mod to the exhaust on,as it tends to increase the cylinder scavenging efficiency,and reduce the exhaust back pressure, and I read that modifying headers in a similar manor is worth .05 seconds on several cars, so don,t think a bit of thinking outside the box as they say won,t pay off in a bit more power or power over a wider rpm band.

http://www.pfyc.com/pc/C75003/C7EXH/Cor ... ngray.html

http://www.pfyc.com/pc/C75005/C7EXH/Koo ... ngray.html

heres the new corvette dual (x) pipe

 

[philly]

oh thats fancy! sounds incredible by the way on the c7

 

[grumpyvette]

http://www.hotrod.com/how-to/engine...y-horsepower-but-which-is-best-for-your-ride/

Equalizing Flow

Balancing the exhaust pressure from bank to bank is just one of the many ways an X- or H-pipe improves overall exhaust flow. With a conservative factory camshaft, the exhaust seemingly flows out the tailpipe in one continuous stream. In reality, however, exhaust waves travel in pulses, which become much more noticeable as camshaft duration increases. Consequently, reducing the detrimental effects of these pulses can positively impact horsepower and torque. “A balance pipe serves two distinct functions. First off, it takes the left and right banks of an engine’s exhaust and provides a crossover point to equalize flow from side to side,” Blane Burnett of Hooker Headers explains. “Secondly, balance pipes smooth out uneven exhaust pulses. Any given engine generates low- and high-pressure exhaust pulses due to the effects of the firing order. As these low and high pulses move downstream through the exhaust piping, they travel at different speeds. Having an exhaust crossover helps draw these pulses out into a more balanced pattern, which ultimately improves engine output. A nice side benefit is that crossovers also decrease in-cabin exhaust drone.”



X vs. H

Although X- and H-pipes perform extremely well for a minimal investment in time and money, both offer unique properties that make one more suitable than the other depending on the application. “The two biggest differences between an X- and an H-pipe are sound and power. Generally, the X-pipe will deliver a more high-pitched exhaust note, making a car sound more exotic, whereas an H-pipe gives a deeper tone with more of a traditional hot rod sound,” says George Rumore of Stainless Works. “As for the difference in power gain between the two, it is very minimal. The X-pipe will usually make anywhere from two to four more horsepower than an H-pipe. The slight horsepower difference comes from the way the X-pipe creates a venturi effect, which helps pull the exhaust gases out of the cylinder faster. Overall, the main difference is sound rather than performance, meaning there are no pros or cons. It’s simply a matter of personal preference.”



In addition to differences in sound and horsepower, both X- and H-pipes affect different parts of the powerband as well. According to PerTronix’s Don Lindfors, the basic configuration of both styles of crossovers lend a clue as to why this is the case. “An H-pipe tends to make more of a difference at lower rpm, while-X pipes will increase power more at higher rpm. As you can imagine, just by looking at each configuration, in the H-pipe the exhaust has to make a sharp 90-degree turn, while the X-pipe offers a smoother transition,” he says. “The X-pipe creates much more of a scavenging effect. That said, it is important to prevent the X-pipe from necking down too small or flow can be hampered. Both an X- and an H-pipe will smooth out the separated sound of the cylinders, while an X-pipe tends to blend all eight cylinders together more.”

For all-out power, X-pipes seem to be the winner, but H-pipes boast several advantages as well. “H-pipes typically offer increased backpressure compared to an X-pipe, which nets an increase in low-end torque. They are also more tunable because they offer more options in terms of the length of the crossover, the diameter of the tube, and the size and location of the transfer hole,” Blane Burnett explains. “As a simpler design that takes up less space, H-pipes have more options as to where on the exhaust system the crossover section can be placed. While performance is a large consideration when designing an exhaust system, vehicle packaging is also a huge factor. Depending on the application, an X- or an H-pipe might suit the chassis better, but an H-pipe certainly offers more options as to where it can be placed.”

my exhaust pipe expander needs to be sprayed with oil and tightened and loosened several times, to expand 3" exhaust pipe enough to allow a second 3" exhaust pipe to slide inside the first, but it will get the job done eventually so while its not ideal it is functional and DIRT CHEAP, compared to a decent professional grade tool.


something like this might be better, but remember the tool surface must slide easily so the inner pipe surface and tool must be kept well lubricated
http://www.etoolcart.com/e-zpipeshaperlarge.aspx

http://www.etoolcart.com/pipe-stretcher-kit.aspx

http://www.mytoolsforyou.com/automotive-tools/MTC-71650.html

http://www.aliexpress.com/store/pro...OPPER-STRONG-PACKING/532410_32283853201.html#!

http://www.amazon.com/Generic-Hydraulic-Expander-Expanding-Swaging/dp/B00M537NJ6

 

[87vette81big]

I am a Single Pattern Isky Guy Grumpy.
FOR SURE.

Hardcore is getting shafted....

I just don't like the sound of X pipes.
TOO QUIET.
UNDERSTAND THE THEORY WHY IT HELPS.

RACE CAR LOUD.
OLD SCHOOL STILL.

 

[87vette81big]

The Steel Warbirds have Dual 2-3/4" Exhaust Pipes Grumpy.
According to the charts above it should only support 566 HP.
707 Advertised Hp. 780 Hp estimated actual.
Why does it not Add up ?

 

[Grumpy]

Dual 2-3/4" Exhaust Pipes Grumpy.
According to the charts above it should only support 566 HP.
707 Advertised Hp. 780 Hp estimated actual.
Why does it not Add up

the CHART refers to NON-SUPERCHARGED engines, and their potential flow characteristics, supercharging changes the dynamic by effectively FORCING higher flow under higher pressures,normal atmospheric pressure entering the carburetor venturies seldom exceeds about 14 psi , add 12 psi of boost and your almost doubling the potential flow rates.
the charts are correct, but don,t take into account the higher pressure of a supercharged applicat1on

 

[87vette81big]

Something is not right Grumpy.
I have been around many 5.0 Supercharged street and race cars.

 

[philly]

to say an exhaust only supports 500hp does not mean that you cannot make 501 hp with that diameter piping....it usuallt means at that power level the exhaust is robbing power.... so if you really wanna see a hellcat wake up, put dual 3.5" exhaust on with headers and no cats and see what happens.

 

[87vette81big]

Too small Phil N/A & Supercharged @ CID Of Hellcat Hemi from my experience .
THE TUBING SIZE CHART IS CORRECT.
CAN FUDGE SOME.
100 HP MORE BOOSTED TWIN PIPES DUAL EXHAUST.

WARBIRDS ARE IN SAME HP AREA AS MY T/A ......My Hunches.

 

[Grumpy]

I got asked why I suggested use of an X pipe

well lets look at the math a bit, exhaust pulse mass exits the engine, in a high pressure pulse as the exhaust valve opens, the piston pushes the exhaust gases trapped in the cylinder up and out and the fast moving mass inertial tends to drag in the following intake runner charge during the over lap period when both valves are momentarily open at the same time.
knowing a few constants in engine pressure and flow helps

an engine usually requires approximately 2.25 cubic feet per minute per horsepower to maximize intake flow and exhaust flow starts to become restrictive at about 115 cfm per square inch


its a rule of thumb or rough guide on the expected combined potential max exhaust port flow rates of the exhaust taken from an observed average of hundreds of recorded dyno results, and not taking into account any flow loss or restriction,and calculating some heat expansion ,its basically worthless except as a way to figuring what size exhaust pipe size thats likely to work, or what size will be restrictive to flow.


I've always preferred the side exhaust header /muffler design on the C3 corvettes,and A.C. COBRAS,

,(like these picture's shows them) my B.I.L well remembers my 1968 BBC corvette so he has installed those hooker side pipes on his 1974 BBC corvette

and on my 1968 corvette the car was slower by almost 2 tenths with the standard comp plus hooker under frame headers,
( I tried them because they potentially saved weight,
(obviously that was with the internal muffler inserts removed from the side pipes while racing)
but the under the car mufflers added too under the car headers total, weight,
are HEAVIER than the side pipes when the whole exhaust system is installed
if you do the required math calculations , you,ll find that most commercial headers are using primary tube length that are too short to be ideal,
as this simplifies manufacture and CLEARANCE ISSUES AND REDUCES MANUFACTURING COSTS.
(the headers with side exhaust design, are closer too the ideal)

related info

http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/

http://garage.grumpysperformance.com/index.php?threads/calculating-required-exhaust-pipe-size.11552/
viewtopic.php?f=52&t=322

so assuming your building a 500 hp engine / 2 (divided by 2 as there's normally two header collectors on a v8) we have 250hp per header collector, (open header collectors) multiply that by 2.25 cfm and you see you need 562 cfm and divide that by 115/square inches and we see we need a 4.9 square inch minimum exhaust collector pipe, per side (open header collectors).
BUT NOW CONSIDER THE FACT THAT THAT INTAKE RUNNER FLOW MASS WAS MIXED WITH FUEL, BURNT and in the process jumped in temperature easily 900F plus

Engine Exhaust Flow Rate Calculation Exhaust flow rate may be calculated using the following formula. Exhaust temperature and intake airflow rate must be determined to calculate the exhaust flow rate. Exhaust temperature and manufacturers maximum backpressure may be approximated using the chart below.
Engine Maximum Engine Type Temperature Backpressure Diesel 2-Cycle Naturally Aspirated = 900ºF 4" Hg Diesel 2-Cycle Turbo = 750ºF 3" Hg Diesel 4-Cycle Naturally Aspirated = 1000ºF 3" Hg Diesel 4-Cycle Turbo = 900ºF 3" Hg Gasoline (all types) = 1200ºF 4" Hg

http://www.asia.donaldson.com/en/exhaust/support/datalibrary/1053747.pdf
Engine Airflow Calculations CFM intake rate is available from the engine manufacturer. If CFM specifications are not available, use the volumetric efficiency calculation. A simple calculation for cfm is to multiple the horsepower of your engine by 2.5. 2-Cycle Engine Airflow Calculation 4-Cycle Engine Airflow Calculation ( ) Engine Size (CID) x RPM 3456 x Volumetric Efficiency = Intake Airflow (CFM)

you can do the calculations but with about 600 psi and maybe an average temperature of 900F theres zero question the cfm entering the cylinder is far less than the exhaust volume produces

UNLESS you match ANY header with a TRUE low restriction exhaust its can NOT possibly work to NEAR its FULL potential, headers are designed to SCAVENGE the cylinders of oil burnt exhaust gases and INCREASE the percentage of fresh fuel air mix, if theres any significant back pressure beyond the header collectors that cuts the headers efficiency way down

http://forum.grumpysperformance.com/viewtopic.php?f=56&t=1730&sid=1b00d3d9124b785ebda3c61b4c630b12

the simple fact is that having an X-pipe effectively DOUBLES the cross sectional area of the exhaust flow past the point of the exhaust pipe X-pipe thus dropping the pressure in about 1/2 PLUS blending the flow,which tends to prolong the cylinder scavenging duration,reduce back pressure,and adding a second (X) tends to further extend the cylinder scavenging by blending and lengthening the pulse duration,s effect on the individual header primary tubes and MELLOWING the exhaust note still further as sound waves impacting each other tend to cancel each other out some what.

if you prefer the old muscle car exhaust note and rumble true dual exhaust pipes without an (X) pipe and a high compression engine matched to a tight LCA on a cam will produce the results your looking for, but in the last 50-60 years science has advanced , and extensive testing has proven,(and its been proven repeatedly) that a carefully designed exhaust with one or two (X) pipes that blend the exhaust pulses, and extend the cylinder scavenging potential of the exhaust has a very measurable advantage in making more power.

 

[87vette81big]

I would have to hear another 455/462 Pontiac Big Block Race Cammed and High Compressuon Grumpy.
If it gets quiet and no Deafing Roar I won't like it.
Everything X-pipe I have heard I don't really like the sound.

 

[Grumpy]

lets say we in theory build a 454/455 engine and spin it at 6500rpm, thats 855 cubic feet of air moving into the carburetor and even more exhaust volume. (if we ignore the heat expansion, and just use the 855 cubic feet figure)
and use a 3" exhaust pipe on each bank thats 428 cubic feet of exhaust per minute traveling thru a roughly 7 square inch area per minute, or 73958 cubic inches of exhaust /or 105654 inches per minute, thats 8804 feet per minute or well over 100 miles per hour in exhaust flow speed(remember thats assuming cold exhaust, its really higher as exhaust volume and heat has actually increased, its this fast moving gas that provides the inertial energy that allow correctly designed headers to scavenge so effectively, and why a properly located (X) pipe can reduce the restriction to flow and prolong the exhaust scavenging or low pressure at the exhaust ports.

http://www.superchevy.com/how-to/ex...y-horsepower-but-which-is-best-for-your-ride/

http://www.hotrod.com/news/1312-news-racing-around/

WATCH THIS VIDEO

 

[Indycars]

Cool demonstration .... I like!

 

[Grumpy]

Exhaust X-Pipes



This simple mod nets more power and great sound

Leonard Emanuelson / autoMedia.com






It's a proven fact that joining the exhaust pipes of multi-cylinder engines improves power and torque over a broad rpm range. A "tuned" set of exhaust headers (with pipes of calculated diameter and length) actually assists sequential firing cylinders to scavenge spent exhaust gases, making room in the cylinder for an undiluted, fresh charge of fuel and air. The velocity of exhaust gases in one header tube causes a low-pressure area in an adjacent tube, literally sucking the exhaust out of that cylinder. The more cylinders, the greater the effect. The late and great Smokey Yunick built several eight-into-one header collector systems that showed increased power on the dyno. Unfortunately, such a system is virtually impossible to package on a typical sedan type of vehicle.

Early H-Pipes
That which works with headers also works downstream with dual-exhaust systems. Unconnected dual exhausts on V-8-powered vehicles act as two independent four-cylinder engines and exhaust systems—and we all know what four-cylinder engines sound like. Back in the '60s, performance engineers at the Big Three car companies discovered that running a balance tube between the two branches of the exhaust system (subsequently called an H-pipe) would broaden the torque curve as well as cut down the interior noise caused by resonance in the exhaust system.




Fast-forward 30 years to the '90s, where a revolutionary development in exhaust technology has taken the balance-tube H-pipe to the next level. Instead of connecting the branches of a dual-exhaust system with a restrictive 90-degree connection, the X-pipe union simply flows the two branches together without changing the direction of exhaust flow, and one side can easily draw from the other for a sizeable reduction in back pressure.


Many companies are now producing X-pipes for most popular performance cars. They are typically available in off-road versions (without catalytic converters) or as 50-state legal models with proper emissions equipment. Most are designed as simple bolt-ons that require less than an hour to install with basic hand tools.


For those who have vehicles where no X-pipe is available, a custom X-pipe can be made by any competent muffler shop by purchasing the X-pipe union and bending up some exhaust tubing to make it fit. If you are fabricating your own X-pipe, a tip is to place the X-pipe union as far to the rear of the car as physically possible—it will make more power that way.[\quote]


More HP
What can you expect from this modification? A major performance-car magazine did a test on a 350 small-block Chevy engine and the results were fairly spectacular. Torque at 3,000 rpm jumped by 20 lb.-ft. and horsepower increased by 13. These are increases in the useable part of the rpm range and should not only result in quicker acceleration but better fuel economy as well.


What we haven't commented on is the sound. Connecting the branches of the dual exhaust in this manner makes for the sweetest-sounding V-8 you can imagine. Instead of hearing the firing impulses of two disconnected four-cylinder engines, you hear all eight cylinders out of each pipe. What a difference