http://www.autolounge.net/calculators/e ... nance.html
viewtopic.php?f=89&t=10341
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
DON,T BE IN A RUSH to start a wholesale swap-out of your current exhaust components, the cure may be a simple minor change to the current systems tendency to vibrate, at its current frequency. that (DRONE) is simply the exhaust pulse frequency,amplified by an exhaust system wide amplification or sympathetic vibration in the exhaust system, IN general , longer length components vibrate at lower frequency's and shorter ones at higher frequency's.
installing an (H) or (X) pipe can either increase or cure the problem as a result of changes in the systems effective length, adding a second (H) or (X) pipe in the system frequently cure the problem, as can swapping to a different muffler or longer tail pipes.
As a general rule youll want to place an (X) pipe as close to the header collector exits as under the car clearances allow , and the mufflers as far to the rear as clearances allow, the (X) pipe allows the exhaust pulse strength to blend and be reduced as it splits into two separate, and roughly pressure balanced paths to exit the car,on some cars a second (x) or (H) balance pipe mounted just before the mufflers helps reduce the drone tendency.
Like a TUNNING FORK, if you change, or add more rubber hanger exhaust system support points and rubber hanger locations on the exhaust or IF YOU change the length , or CHANGE INE INTERNAL LENGTH OF THE PIPES,you change the vibration frequency, if its changed to well above or below the engine exhaust pulse frequency the drone is destroyed or prevented.
http://www.kettering.edu/physics/drusse ... Frame.html
http://www.dynomax.com/ (click on video and watch it)
http://crgis.ndc.nasa.gov/crgis/images/ ... fflers.pdf
MANY people think its caused by the brand of mufflers used or that swapping mufflers will eliminate it, its a frequency related problem, and both exhaust diameter and length effect the frequency it occurs at, exhaust hanger design and placement can effect the frequency and failure to extend the exhaust exit length past the rear of the car also effects the sound level in the car,PLACEMENT OF THE EXHAUST CROSS PIPE "(X) PIPE " has a huge effect on the rpm point you hear the drone
all pipes will have a natural vibration frequency , the shorter it is the higher the frequency, if you can move the frequency of the exhaust system high enough that you rarely reach that natural frequency you eliminate the potential problem, in most cases thats fairly easy to do by placing an (X) or in some cases a (H) pipe as close to the header collectors as possible, thus raising the frequency above your useful RPM range
dynomax recently introduced a valved exhaust muffler that shows some promise as it will reduce any reversion pulse strength
THE dynomax mufflers with the valve have a reputation for rattling like a tin can full of marbles with a radical cam and true dual pipe muffle exhaust, the rattle is the result of individual exhaust pulse flow from individual cylinders reaching and rapidly forcing an opening in the one way exhaust flow gate valve, that opens as the exhaust volume of gas flow hits it and forces it open,then momentarily wanes (is reduced) the gate closed as the spring forced it closed,(SEE PICTURE) resulting in the rattle as the exhaust flow mass is far from consistent.
mounting a dual (X) PIPE tends, to reduce the individual exhaust pulse flow mass and energy, the (X) pipe in front of the muffler tends to greatly reduce the individual pulse strength and velocity by dividing and slowing the flow as the internal cross sectional area rapidly increased and even out the flow as it hits the flow gate, having two in a series works even ore effectively.
viewtopic.php?f=56&t=495
IF you have an exhaust that produces an annoying exhaust drone its basically a result of an exhaust pulse frequency thats amplified as a harmonic frequency that the exhaust system can vibrate at , now if you destroy that pulse frequency ,in that exhaust by altering its physical vibration characteristics, o it vibrates at a frequency above or well below what the engine exhaust produces,or you can change component placement, the exhaust systems tendency to vibrate at that frequency will be altered so you cure the problem and the DRONE, inserting exhaust cones in the system either behind the (X) pipes or in the tail pipes or lengthen the exhaust pipe exit tip length have both proven to reduce or eliminate that tendency to allow the sympathetic frequency or "DRONE"
remember both sides of the exhaust tend to FEED OFF the other side in some designs, so if you for an example put an exhaust cone inside the exhaust pipe in one leg behind the (X) pipe, and the other side in front of the muffler entrance the distances would be significantly altered and the sides would vibrate differently canceling that sympathetic tendency
viewtopic.php?f=56&t=1503
mufflers designed to trap and destroy reversion pulse strength also help
Exhaust noise is the perceived vibration or resonance caused by the high pressure pulse of exhaust gases exiting the engine in strong intermittent pulses that match the engine rpm, you reduce the perceived noise by absorbing or dissipating the strength of the individual pulses and by damping or blending the low and high pressure peaks in the pulse strength, this has been well proven, to be helped by adding an (X) pipe to the exhaust as it doubles the cross sectional area, thus instantly reducing the gas velocity and blends the pulsed thus effectively changing the two exhaust pulse per cylinder bank per rotation into four less intense pulses past the (X) pipe , this also tends to equalize the exhaust flow rates, reduce flow restriction and thus change and in most cases MELLOW or LOWER the strength of each individual pulse by interrupting the original frequency range caused by the engines exhaust pulse strength in the process.
Ive found that mounting DUAL in series (X) pipes has both a slight beneficial increase in exhaust scavenging, and a noise reducing tendency, the use of dual in series (X) pipes, very defiantly changes the rpm range and tone of any exhaust note!
several of my friends have chosen to install those muffler eliminators and obviously each of us has a individual tolerance for noise level and the type of exhaust note or rumble we prefer
I know many of the younger guys seem to like that raspy exhaust sound and I was amazed at how quiet the car actually is with no mufflers at all,just those muffler eliminators, if you run the dual (X) pipes but I think many of us older guys will still find mufflers preferable.
http://www.ecklerscorvette.com/corv...less-steel-quad-zr1-style-tips-1984-1991.html It has a nice rumble at idle.
placing two 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
PLACING A MUFFLER OR RESONATOR LIKE THESE DIRECTLY BEHIND AN (X) PIPE tends to significantly reduce that drone sound and can increase scavenging efficiency in some cases
http://www.summitracing.com/parts/WLK-17554/?rtype=10 ($120)
A simplistic statement goes like this: (from a Monte Carlo forum)
"Drone in the exhaust is due to the engine driving the exhaust system
at its resonant frequency. You can't get rid of it, any length of pipe has
a natural frequency, but you can change the frequency (RPM) it happens at.
Stock exhaust systems are tuned to put the resonant frequencies outside the normal RPM range the engine is run in. Sometimes they add resonators for this purpose.
To raise the resonant frequency of a system, shorten its
length. To do this, you can try tail pipes that exit by the wheel (like
GN's have), or you can try a muffler with a shorter internal flow path. If
you have a true dual system, you can change the natural frequency of the
system dramatically by adding a balance tube. If you can't shorten the
system, then you can add slightly less than one wavelength of pipe. This
will also raise the resonant frequency of the system. The wavelength in a
single converter system (not true dual) is a little less than three feet at
3000 RPM. Shortening the system by a foot or so will move a resonance at
2000 RPM to about 3000 RPM.
To move a resonance, calculate the wavelength at the RPM that gives
the resonance you want to move. Then calculate the wavelength at the RPM you would rather it be at. The difference is the length of pipe you need to add or delete.
Add to lower the RPM, delete to raise it. If you want to raise it but you can't cut any pipe out, then add one wavelength of pipe minus the amount you calculated. This will have the same affect. If you add or subtract a multiple of a wavelength exactly, you will not change the resonant RPM.
Wavelength = 1100 X 60 X 1/RPM X 1/4 X 1/2
or
Wavelength = 8250 / RPM
Wavelength = standing wavelength
1100 = speed of sound in air in feet per second
60 = convert RPM to Revs per second
RPM = RPM
1/4 = four cylender firings per revolution (make this 1/2 for "true
dual")
1/2 = standing wavelength is half the wavelength of a "normal" wave
Submitted by: Richard Kwarciany kwar at FNAL.FNAL.GOV"
THE (X) BY FAR is more effective, the (H) may equalize the pressure to a great extent but the (X) blends and equalizes the flow,
http://www.uucmotorw...etorquemyth.htm
whats the difference?
lets say for the example the exhaust pulse is a quart to water moving at several hundred feet per second, but unlike water it can be compressed,since the exhaust pipe inside diam. is set the length of the pulse or slug of exhaust exiting the engine every 90 degrees of rotation (v8) has inertia/energy/mass, if it passes a right angle low pressure exit point, at first it flows into both routes but as the mass passes the opening a slight negative pressure forms and it reverses and the flow changes, put a vacuum gauge on the (h) and it vibrates, wildly.
install an (X) and the flow from both sources is FORCED to BLEND, line up, equalize and BOTH sections of the up stream flow benefit from the
as each inertia/energy/mass, and slight negative pressure that forms, but its far more equalized.
put another way if one side was pumping out dark green water and one side was pumping clear, an (H) would have dark green exiting one side and light green exiting the other, an (X) would have both sides an equal, slightly lighter green flow .now at low rpms , or with a smaller than ideal pipe diam. thats no big deal, but at high rpms, BOTH the SCAVENGING of the cylinders your trying to enhances and the reduction of the restriction to flow tends to be better with the (X) put a vacuum gauge on the (X) and it vibrates. but not to nearly the same extent, and the changes in pressure reading remain more consistent
DON,T be thinking that either is a mandatory huge improvement, it may or may not help the power, the degree of restriction, displacement, compression ratio, cam timing and the efficiency of the headers has a good deal to do with your results, and sticking restrictive mufflers on past the (X) or (H) can effectively kill most of the potential benefits
viewtopic.php?f=89&t=10341
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
DON,T BE IN A RUSH to start a wholesale swap-out of your current exhaust components, the cure may be a simple minor change to the current systems tendency to vibrate, at its current frequency. that (DRONE) is simply the exhaust pulse frequency,amplified by an exhaust system wide amplification or sympathetic vibration in the exhaust system, IN general , longer length components vibrate at lower frequency's and shorter ones at higher frequency's.
installing an (H) or (X) pipe can either increase or cure the problem as a result of changes in the systems effective length, adding a second (H) or (X) pipe in the system frequently cure the problem, as can swapping to a different muffler or longer tail pipes.
As a general rule youll want to place an (X) pipe as close to the header collector exits as under the car clearances allow , and the mufflers as far to the rear as clearances allow, the (X) pipe allows the exhaust pulse strength to blend and be reduced as it splits into two separate, and roughly pressure balanced paths to exit the car,on some cars a second (x) or (H) balance pipe mounted just before the mufflers helps reduce the drone tendency.
Like a TUNNING FORK, if you change, or add more rubber hanger exhaust system support points and rubber hanger locations on the exhaust or IF YOU change the length , or CHANGE INE INTERNAL LENGTH OF THE PIPES,you change the vibration frequency, if its changed to well above or below the engine exhaust pulse frequency the drone is destroyed or prevented.
http://www.kettering.edu/physics/drusse ... Frame.html
http://www.dynomax.com/ (click on video and watch it)
http://crgis.ndc.nasa.gov/crgis/images/ ... fflers.pdf
Jim Rockford said:Just figured I'd post this up to start a flame war..lol
Muffler Comparision Thread.
The results in HP order:
1.Flowtech Warlock (open) 374.2 hp/ 333.1 tq
2.Bassani Real Street 373.7 hp/ 333.8 tq
3.Hooker Maxflow 373.5 hp/ 333 tq
4.Borla XS 373.3 hp/ 332.6 tq
5.Magnaflow 372.8 hp/ 332.5 tq
6.MAC 372.3 hp / 331.5 tq
7.Flowtech Afterburner 372.3 hp/ 330.1 tq
8.Hooker Aerochamber 372.1 hp/ 330.4 tq
9.Bassani 372 hp/ 333.5 tq
10.Spintech 371.6 hp/ 332.2 tq
11.Edelbrock Performer RPM 370.9 hp / 331.3 tq
12.Borla XR1 370 hp/ 334 tq
13.Flowtech Terminator 369.5 hp / 331.3 tq
14.Dynomax Ultra Flo 369.4 hp/ 333.2 tq
15.Flowmaster 369.4 hp / 331.8 tq
16.Flowtech Warlock 366.3 hp / 325.3 tq
17.No muffs 365.2 hp / 330.1 tq
Sound Off in Quietest to Loudest (Decibels):
1.Borla XS, 80db at idle, 90db at 2,000 rpm, 110db at WOT.
2.Hooker Maxflow, 80db at idle, 90db at 2,000 rpm, 120db at WOT.
3.Magnaflow, 82db at idle, 91 at 2,000 rpm, 114db at WOT.
4.Flowmaster, 82db at idle, 93 at 2,000 rpm, 115db at WOT.
5.Flowtech Warlock, 83db at idle, 92 at 2,000 rpm, 112db at WOT.
6.Dynomax UltraFlo, 83db at idle, 94 at 2,000 rpm, 113db at WOT.
7.Borla XR1, 83db at idle, 96db at 2,000 rpm, 118db at WOT.
8.Bassani Street, 83db at idle, 96db at 2,000 rpm, 120db at WOT.
9.Edelbrock RPM, 84db at idle, 93db at 2,000 rpm, 118db at WOT.
10.Bassani Real Street, 84db at idle, 96db at 2,000 rpm, MAX. (120+db).
11.Flowtech Afterburner, 86db at idle, 94db at 2,000 rpm, 115db at WOT.
12.Flowtech Terminator, 86db at idle, 94db at 2,000 rpm, 119db at WOT.
13.Hooker Aerochamber, 87db at idle, 94db at 2,000 rpm, 114db at WOT.
14.SpinTech, 87db at idle, 97db at 2,000 rpm, 116db at WOT.
15.MAC, 87db at idle, 98db at 2,000 rpm, 119db at WOT.
16.No Muffler, 91db at idle, 103db at 2,000 rpm, MAX. (120+db).
And I have listed here a muffler shootout test done by CAR CRAFT, they show the best bang for the buck, and show the db's
The Mufflers
MAKE MODEL Part No. COST
SUMMIT Turbo 630125 $14.75
THRUSH Magnum Glasspack 24214 $16.50
THRUSH Boss Turbo 17718 $23.95
HOOKER Competition 21006 $25.95
DYNOMAX Super Turbo 17733 $28.50
DYNOMAX Race Magnum 24215 $31.95
HOOKER Super Competition 21106 $35.95
SUMMIT Fully Welded 630325 $38.69
FLOWTECH Afterburner 50322 $39.95
MUFFLER FLOW TEST
MUFFLER Flow at 28-in H20
DynoMax Race Magnum 528.64 cfm
Thrush Magnum Glasspack 507.40 cfm
Summit Fully Welded 343.38 cfm
Flowtech Afterburner 342.20 cfm
DynoMax Super Turbo 333.94 cfm
Hooker Competition 232.46 cfm
Hooker Super Competition 320.96 cfm
Summit Turbo 331.16 cfm
Thrush Boss Turbo 297.36 cfm
MUFFLER Idle dB WOT dB
DynoMax Super Turbo 89 123
DynoMax Race Magnum 94 133
Flowtech Afterburner 92 124
Hooker Competion 92 122
Hooker Super Competion 90 125
Summit Turbo 89 124
Summit Fully Welded 92 125
Thrush Boss Turbo 90 123
Thrush Magnum Glasspack 92 128
DYNO TEST
All mufflers were dyno-tested on a 355-cube SBC with 10.0:1 compression, Air Flow Research 190 aluminum heads, a CompCams 292 hyd. a Victor Jr. intake, a Holley 750-cfm double-pumper, and 1 5/8 Headman headers.
MUFFLER HP TORQUE 2,500-6,000rpm Average
Hooker Competition 397.4 381.1 286.8hp/351.9 lb-ft
Thrush Boss Turbo 407.1 384.9 292.1 hp/357.5 lb-ft
DynoMax Race Magnum 409.5 394.3 298.8 hp/366.9 lb-ft
Flowtech Afterburner 409.7 391.2 294.8 hp/361.7 lb-ft
Thrush Glasspack 409.5 389.8 297.7 hp/365.3 lb-ft
Summit Turbo 411.5 386.3 291.5 hp/357.4 lb-ft
DynoMax Super Turbo 412.7 387.2 292.6 hp/358.6 lb-ft
Hooker Super Comp 413.8 387.2 292.8 hp/359.0 lb-ft
Summit Fully Welded 415.4 390.7 295.6 hp/362.4 lb-ft
i have another test here on my computer but i don't know how to upload it onto this site because it is in a adobe pdf file.
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
Standard OEM 2 ¼” Inlet/Outlet 138-152 CFM
Standard OEM 2 ½” Inlet/Outlet 161-197 CFM
and some real world testing to back up some numbers
http://www.pontiacstreetperformance.com ... haust.html
http://www.mustang50magazine.com/techar ... index.html
"Recommendations:
1. Always use a crossover of one kind or another. Our tests indicate that the X type gives additional improvements over the H type.
2. Mount the mufflers as far to the rear of the chassis as possible. An important characteristic of the exhaust system (behind the headers) is its ability to dissipate heat energy. Heat loss brings with it, gas volume reduction, enabling smaller mufflers and pipes to be used without penalty.
3. Always us the largest case muffler that you can fit under the chassis possible. The larger internal volume allows additional acoustical energy to be absorbed ,dissipated and eliminated.
4. Unless an engine is in the 500+ horsepower level or run at very high RPM, the maximum tailpipe size required for minimal power loss is probably 2.5" diameter. When the exhaust pipes and mufflers drop the temperature significantly, the volume of the exhaust gas is reduced and tailpipe sizes is not as critical.
5. When you must adapt various pipe sizes, always use long tapered cone reducers, such as, those available from Flowmaster. You can also use a crossover that has reduced pipe sizes built into it."
And this get alot of folks in trouble..the back pressure myth.
http://my.prostreetonline.com/forums/sh ... php?t=1639
MANY people think its caused by the brand of mufflers used or that swapping mufflers will eliminate it, its a frequency related problem, and both exhaust diameter and length effect the frequency it occurs at, exhaust hanger design and placement can effect the frequency and failure to extend the exhaust exit length past the rear of the car also effects the sound level in the car,PLACEMENT OF THE EXHAUST CROSS PIPE "(X) PIPE " has a huge effect on the rpm point you hear the drone
all pipes will have a natural vibration frequency , the shorter it is the higher the frequency, if you can move the frequency of the exhaust system high enough that you rarely reach that natural frequency you eliminate the potential problem, in most cases thats fairly easy to do by placing an (X) or in some cases a (H) pipe as close to the header collectors as possible, thus raising the frequency above your useful RPM range
dynomax recently introduced a valved exhaust muffler that shows some promise as it will reduce any reversion pulse strength
THE dynomax mufflers with the valve have a reputation for rattling like a tin can full of marbles with a radical cam and true dual pipe muffle exhaust, the rattle is the result of individual exhaust pulse flow from individual cylinders reaching and rapidly forcing an opening in the one way exhaust flow gate valve, that opens as the exhaust volume of gas flow hits it and forces it open,then momentarily wanes (is reduced) the gate closed as the spring forced it closed,(SEE PICTURE) resulting in the rattle as the exhaust flow mass is far from consistent.
mounting a dual (X) PIPE tends, to reduce the individual exhaust pulse flow mass and energy, the (X) pipe in front of the muffler tends to greatly reduce the individual pulse strength and velocity by dividing and slowing the flow as the internal cross sectional area rapidly increased and even out the flow as it hits the flow gate, having two in a series works even ore effectively.
viewtopic.php?f=56&t=495
IF you have an exhaust that produces an annoying exhaust drone its basically a result of an exhaust pulse frequency thats amplified as a harmonic frequency that the exhaust system can vibrate at , now if you destroy that pulse frequency ,in that exhaust by altering its physical vibration characteristics, o it vibrates at a frequency above or well below what the engine exhaust produces,or you can change component placement, the exhaust systems tendency to vibrate at that frequency will be altered so you cure the problem and the DRONE, inserting exhaust cones in the system either behind the (X) pipes or in the tail pipes or lengthen the exhaust pipe exit tip length have both proven to reduce or eliminate that tendency to allow the sympathetic frequency or "DRONE"
remember both sides of the exhaust tend to FEED OFF the other side in some designs, so if you for an example put an exhaust cone inside the exhaust pipe in one leg behind the (X) pipe, and the other side in front of the muffler entrance the distances would be significantly altered and the sides would vibrate differently canceling that sympathetic tendency
viewtopic.php?f=56&t=1503
mufflers designed to trap and destroy reversion pulse strength also help
Exhaust noise is the perceived vibration or resonance caused by the high pressure pulse of exhaust gases exiting the engine in strong intermittent pulses that match the engine rpm, you reduce the perceived noise by absorbing or dissipating the strength of the individual pulses and by damping or blending the low and high pressure peaks in the pulse strength, this has been well proven, to be helped by adding an (X) pipe to the exhaust as it doubles the cross sectional area, thus instantly reducing the gas velocity and blends the pulsed thus effectively changing the two exhaust pulse per cylinder bank per rotation into four less intense pulses past the (X) pipe , this also tends to equalize the exhaust flow rates, reduce flow restriction and thus change and in most cases MELLOW or LOWER the strength of each individual pulse by interrupting the original frequency range caused by the engines exhaust pulse strength in the process.
Ive found that mounting DUAL in series (X) pipes has both a slight beneficial increase in exhaust scavenging, and a noise reducing tendency, the use of dual in series (X) pipes, very defiantly changes the rpm range and tone of any exhaust note!
several of my friends have chosen to install those muffler eliminators and obviously each of us has a individual tolerance for noise level and the type of exhaust note or rumble we prefer
I know many of the younger guys seem to like that raspy exhaust sound and I was amazed at how quiet the car actually is with no mufflers at all,just those muffler eliminators, if you run the dual (X) pipes but I think many of us older guys will still find mufflers preferable.
http://www.ecklerscorvette.com/corv...less-steel-quad-zr1-style-tips-1984-1991.html It has a nice rumble at idle.
placing two 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
PLACING A MUFFLER OR RESONATOR LIKE THESE DIRECTLY BEHIND AN (X) PIPE tends to significantly reduce that drone sound and can increase scavenging efficiency in some cases
http://www.summitracing.com/parts/WLK-17554/?rtype=10 ($120)
A simplistic statement goes like this: (from a Monte Carlo forum)
"Drone in the exhaust is due to the engine driving the exhaust system
at its resonant frequency. You can't get rid of it, any length of pipe has
a natural frequency, but you can change the frequency (RPM) it happens at.
Stock exhaust systems are tuned to put the resonant frequencies outside the normal RPM range the engine is run in. Sometimes they add resonators for this purpose.
To raise the resonant frequency of a system, shorten its
length. To do this, you can try tail pipes that exit by the wheel (like
GN's have), or you can try a muffler with a shorter internal flow path. If
you have a true dual system, you can change the natural frequency of the
system dramatically by adding a balance tube. If you can't shorten the
system, then you can add slightly less than one wavelength of pipe. This
will also raise the resonant frequency of the system. The wavelength in a
single converter system (not true dual) is a little less than three feet at
3000 RPM. Shortening the system by a foot or so will move a resonance at
2000 RPM to about 3000 RPM.
To move a resonance, calculate the wavelength at the RPM that gives
the resonance you want to move. Then calculate the wavelength at the RPM you would rather it be at. The difference is the length of pipe you need to add or delete.
Add to lower the RPM, delete to raise it. If you want to raise it but you can't cut any pipe out, then add one wavelength of pipe minus the amount you calculated. This will have the same affect. If you add or subtract a multiple of a wavelength exactly, you will not change the resonant RPM.
Wavelength = 1100 X 60 X 1/RPM X 1/4 X 1/2
or
Wavelength = 8250 / RPM
Wavelength = standing wavelength
1100 = speed of sound in air in feet per second
60 = convert RPM to Revs per second
RPM = RPM
1/4 = four cylender firings per revolution (make this 1/2 for "true
dual")
1/2 = standing wavelength is half the wavelength of a "normal" wave
Submitted by: Richard Kwarciany kwar at FNAL.FNAL.GOV"
THE (X) BY FAR is more effective, the (H) may equalize the pressure to a great extent but the (X) blends and equalizes the flow,
http://www.uucmotorw...etorquemyth.htm
whats the difference?
lets say for the example the exhaust pulse is a quart to water moving at several hundred feet per second, but unlike water it can be compressed,since the exhaust pipe inside diam. is set the length of the pulse or slug of exhaust exiting the engine every 90 degrees of rotation (v8) has inertia/energy/mass, if it passes a right angle low pressure exit point, at first it flows into both routes but as the mass passes the opening a slight negative pressure forms and it reverses and the flow changes, put a vacuum gauge on the (h) and it vibrates, wildly.
install an (X) and the flow from both sources is FORCED to BLEND, line up, equalize and BOTH sections of the up stream flow benefit from the
as each inertia/energy/mass, and slight negative pressure that forms, but its far more equalized.
put another way if one side was pumping out dark green water and one side was pumping clear, an (H) would have dark green exiting one side and light green exiting the other, an (X) would have both sides an equal, slightly lighter green flow .now at low rpms , or with a smaller than ideal pipe diam. thats no big deal, but at high rpms, BOTH the SCAVENGING of the cylinders your trying to enhances and the reduction of the restriction to flow tends to be better with the (X) put a vacuum gauge on the (X) and it vibrates. but not to nearly the same extent, and the changes in pressure reading remain more consistent
DON,T be thinking that either is a mandatory huge improvement, it may or may not help the power, the degree of restriction, displacement, compression ratio, cam timing and the efficiency of the headers has a good deal to do with your results, and sticking restrictive mufflers on past the (X) or (H) can effectively kill most of the potential benefits