Intake Wave Tuning & Long-Runner Intakes: Is taking advantage of the 2nd reflected wave possible?

NewbVetteGuy

Well-Known Member
I've got a huge collection of long-runner engine combos and dyno results that I'm going to start going through and posting here, specifically looking at the issue of whether it's possible / plausible to take advantage of not just the 3rd reflected wave, but the more powerful 2nd reflected wave in a high flowing TPI style intake.

I've definitely noticed some of the super ported out / highly modified TPI intakes starting to show the formation of a 2nd torque peak at around 6,000 RPM, and that highly correlates to the intake wave tuning formulas / charts... These high flowing head + long-runner intakes like the FIRST Fuel Injection intake, when a part of a total COMBO designed to make power to 6,000 or just beyond it, have enough airflow to keep making power this high in the RPM band, and then you get the even stronger +10% pressure 2nd reflected wave showing up.

-The Richard Holdener TPI testing dyno charts clearly show that 2nd peak forming towards the end. I'm hoping to figure out the total runner length on a few of the combos that I have dyno graphs for and calculate when it's expected that the system will start picking up that 2nd wave. (I really THINK that this is what's responsible for those 2nd higher RPM peaks, but I want to look into it more.)

Today is a pretty busy day for me, but I should be able to make a little progress on this later today, if not, tomorrow.
IF anyone has reliable info on the total runner length (entry to valve) for common TPI intake combos, that would DEFINITELY be useful. I know I've got this saved somewhere, but right now I just vaguely remember OEM TPI being 21"-22", but a quick search had some sources claiming as much as 24"...


TPI Wave Tuning Harmonics MAdBill SpeedTalk.jpg
And full-disclosure on my thinking / hope: I'm HOPING that the data will show that some of these high flowing long-runner combos ARE just starting to see the beginning of the 2nd reflected wave and that it's possible for the RPM limits of a modern well-designed long-runner engine to continue to build power even a bit higher into the RPM range as it picks up the stronger 2nd harmonic. (Ex: My FIRST intake has a runner length of 14.25" + my Profiler head's intake port length of 5" = 19.25"; I think many SBC heads have a 5.5" intake port length so they'd end up at 19.75" total runner length. -According to the reflected wave calculations these should start picking up the 10% pulse strength reflected wave around 5,900 RPM or so, but the 2nd wave is much more broad in RPM vs. the 3rd wave and for 20" runners carries to over 7,000 RPM. (I'm not proposing build a TPI engine with a cam designed to peak @ 7,000 RPM, but if you can get power to carry to 6,500 RPM and be in the "meat" of the 2nd reflected wave's +10% pressure "super charging", it would really help a good long-runner combo's peak power AND average power.

-It just seems like "uncharted waters", so I'm largely drawn to it.

I know the history and folk-lore with people trying to get more power out of the terrible flowing OEM GM TPI intakes by just installing high duration dual-plane style cams on them and then getting neither the great mid-range torque out of a TPI NOR any high RPM performance out of it (because 350 cubic inches is airflow limited in a stock TPI @ 4,500 RPM) and then TPI engine combos moving towards much lower durations and power peaks and focusing on increased airflow and lift (the Lingenfelter long-runner recipes showed how to make power with good TPI combos pretty clearly, IMO), BUT now we've got bolt on TPI style intakes that flow 294 CFM on the "weak" runners and 205cc heads making +300 CFM and we can support the AIRFLOW to move long-runner engine combos up in RPM and I think we're seeing some of these combos just starting to touch the bottom of the RPM range where the even stronger 2nd reflected wave becomes a factor, and I feel like there's a possibility that one of this high flowing TPI engines might actually be able to keep making power to 6,500 WITH IT'S LONG RUNNERS. (No siamesed runners to hack the runner length shorter; the longer runners actually help bring the 2nd wave in at a lower RPM.)

-I AM well aware of the incredible experiments that user 1989GTATransAm did and documented on the ThirdGen and Speed-Talk forums and that he DID manage to clearly benefit from the 2nd reflected wave, BUT he did it with shorter runners and insane amount of effort and labor and the reflected wave math says that picking up the 2nd reflected wave is not only possible with the longer runners, but actually happens at a lower RPM with them. I think the idea of taking advantage of the 2nd reflected wave with something like a bolt-on FIRST intake and just super flowing heads and a bit more duration might bring 6,500 RPM and near 500 HP to a pretty simple "bolt together" "TPI-style intake" combo. (That would be the ultimate dream outcome, IMO.)

-This is my theory and I'm trying to see if the data supports it... A crazy wild goose chase / pipe dream, maybe, but I figure I'm likely to learn something even if this doesn't pan out the way that I'm hoping.




Adam
 
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here's a couple cents worth of experience that might help,
every choice you make in components you select in your engine build is a compromise in some or several areas,
concerning power/durability/engine power band etc.
as many of the older guys I used to race with and engine build for over several decades back,
may remember,
I was and am a very firm believer in crower/kinsler mechanical fuel injection,
I had a maroon 4 speed 13.7:1 compression ratio,496 BBC 1968 vette,
but it looked rather similar to this, corvette picture below, with the stack injection,
images

and had more power than I could use even with only a high compression 496 BBC.
I had used several tunnel ram/ carb intakes with good results,
but eventually I swapped to CROWER mechanical fuel injection, on my BBC engine, it was an interesting learning process,
by ID say mechanical fuel injection was a huge step up in power over anything a tunnel ram could provide back in the mid 1970s
CrowerInjectorsa.jpg


MY corvette was dark maroon but it looked similar to this corvette with the crower injection sticking through the hood
78CrowerFI1.jpg


it had the great advantage of having easily replaced and adjustable length individual intake runner lengths
longer stacks tend to lower the power bands rpm range,
thus you can use the easily swapped stack length to help tune the power band.
your going to be trying to match and balance the exhaust header scavenging,
which is several times stronger than the intake runner pulse strength in a properly designed engine,
and remember stack injection is already far more
effective at cylinder filling efficiency than any tunnel ram or carb intake design,
as there's usually a much longer and
straighter column of air stacked over the individual intake valve
in many designs double or triple the column of the typical tunnel ram runner design in a stack injector manifold

portmatchtunnel.jpg


keep in mind many EFI intakes are updated versions if the basic tunnel-ram intake design offering superior dry air flow and a direct injector shot of a high pressure mist of fuel aimed at the back of the intake valve
and cam timing to the intake runner reversion pulse strength. within a similar power band.
in my case I was trying to boost power in the 4500rpm-6500rpm range

get those factors close to correctly matched to the same power band/rpm range.
, and each enhances the effect of the other components efficiency,
you will notice the improved power band in both engine sound and the seat of the pants response,
(obviously in MPH in the time slips)

ET has more to do with your ability to launch and shift, and suspension/traction, issues.
but a noticeable boost in peak rpm is generally indicating better peak and mid rpm power

obviously having the intake runner pressure wave impacting the back of the intake valve at or close to the same time as the maximum negative pressure wave in the header scavenging wave hitting the open exhaust valve is being mostly controlled by cam timing and to some extent the engines displacement and size and length of the headers.
what I found rather rapidly that was the addition of a 18"-22" extension to the header collector on the open headers, on my corvettes side exhaust and use of longer tubes on my crower stack injector intake aided the power/torque curve noticeably in the seat of the pants feel you got in the car,
it was very obvious once you hit about 3900-4200 rpm and it just pulled harder especially from about 4500rpm through to maybe 6100rpm, with the cam I ran.
CROWER no longer sells the exact cam I used but it was very similar to the current
#01486

ram tubes in various lengths can be ordered from several suppliers, obviously you are limited to the port/runner cross sectional area of the intake manifold design you purchase, and that will limit your peak power in some cases
Ramtube_Trad-PT-e1486673542449.jpg


kinslert2.jpg

Cylinder-Pressure-lLrg.gif


AS your displacement per cylinder increases the effective valve size per cubic inch decreases so you need a slightly tighter LSA and these charts should help.

exhaustpressure.jpg



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if your building an engine to race , your choices are a bit less complicated than building an engine for street/strip use!
you really don't generally care about maximizing fuel mileage, or having the engine idle smoothly, nor are you generally being concerned with being stuck in traffic with the air conditioning on, or only having access to lower quality/low octane fuel.
with a race engine, build,
you select the intended rpm range, maximize the compression ratio, to use the best high octane fuel, available,
and gear the drive train to operate in or near the peak torque and peak power/rpm range.

you select cam duration LSA and port size to maximize power/torque and are much less concerned with lower rpm idle characteristics.






 
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The "First batch" is just looking at the old WestTech dyno runs from what I believe to be the "10 Time the Torque" article, reinterpreted and displayed by Richard Holdener (I'm going to go pull the charts from the 10x the torque article to see if they show some of the torque out higher in RPM beyond 6,100 because Richard seemed to cut the torque graphs off @ 6,100 even though for the longer runner intakes they ran the dyno up to 6,400 RPM.

These tests were on a 10ish:1 CR 383 with AFR 195c heads and a Comp hyd roller 288HR.

#1 Factory TPI:
Note that this engine has a 2nd torque peak that starts showing up at 6,100 RPM; this appears to be in the "meat" of the 2nd harmonic wave in a stock-length TPI runner -is it from increased cylinder filling from the +10% pressure 2nd harmonic wave? or some dyno anomaly?
1 383 AFR head stock TPI intake.png

#2 Edelbrock TPI system (stock runner length, just bigger ID for more airflow):
I'm not interested in tracking the increase in power here; that's well covered in the video and the 10x the torque article, but any rising torque as we get into the 2nd reflected wave RPMs for the intake, and we again see an upwards "tick" in the torque @6,100 RPM. (I SO wish this went further out beyond 6,100 rpm...)
2 383 AFR head Edelbrock TPI.png

#3: Extrude Honed TPI base + TPIS big runners & Throttle body (OEM runner length)
Torque starts moving back up at 6,100 RPM again
3 383 afr head extrude honed tpi TPIS bit runners and throttle body.png

#4 TPIS full system: Lower intake, runners, bigger throttle body -same OEM runner length:
Same bump in torque at 6,100 rpm..
4 383 AFR head TPIS full system.png

#5 AZ Speed and Marine Siamesed Runner "TPI" system - This one has shorter runners which would increase the RPM at which the 2nd wave becomes a factor.
This one the dyno clearly ran out to at least 6,200 RPM per the hp graph, but the torque gets cut off even for the shorter runners to end at the same RPM as the original TPI test, unfortunately... .What I REALLY want to see is these things run further out but I understand why someone would cut a TPI off sooner.

There is NOT the upward torque spike @ 6,100 like with the OEM length systems, though..
5 383 AFR head AZ Speed and Marine shorter runners.png

#6 SLP T-Ram: Another shorter runner alternative
DYNO run to 6,200 RPM again and no 2nd torque peak; no upward bump in torque
6 383 AFR head SLP TRam shorter runners.png




Next I want to go pull up a bunch of the other dyno graphs that I have for long-runner engine combos and try to see if these 2nd torque peaks start showing up on them in the range that the wave tuning calculations expect to see a +10% pressure increase from the 2nd reflected wave or not... HOPING that someone actually continues the dyno beyond 6,100 just to be able to look for any later RPM torque bumps.

I'll end up posting 1989GTA Trans Am's dyno of his shorter runner build where the 2nd wave definitely shows up to the party; his was a wheel dyno, if my memory isn't complete junk.
 
first, thank you for posting clear dyno charts, as it obviously helps illustrate your question!
yeah, obviously it looks like that second wave may be helping the cylinder fill efficiency,
what goes in, needs to go out, and in the process its heated rapidly expanded,
and in the process, its rapidly heated, and exits under high pressure,
remember, the inertia of the exhaust has far higher energy than the average 14. lbs of external outside air pressure.
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exhaustpressure.jpg



EXFLOWZ4.jpg



Id point out I think part of the reason the dyno charts are limited to about 6200 rpm,
is the result of both the potential loss of valve train stability, with a hydraulic roller sbc valve train,
and the potential limits on safe piston speeds to longer term durability.
Id also point out that in most cases the stock cars exhaust system will not allow the exhaust flow.
and enhanced cylinder scavenging, required to,
allow the extended intake flow rates to become a useable factor in the engines power curve
then of course port stall speed as the ports cross sectional area will limit the air flow entering the cylinder
in most cases that intake port cross sectional area or the exhaust port flow will stall,
limiting and higher rpm power gains.

on a 383 SBC your port must be at least 2.17 sq inches minimum,
and at about 2.45 sq inches your maxing out the potential flow at 6200 rpm
if your current intake runner or port size in the heads is not at least 2.45 sq inches or greater your reaching port stall
ideally you'll want about 3.0-3.2 sq inches on that intake runner and port size if you want to push rpms/power and match the intake flow are to feed the cylinders at lets say 7000 rpm

a 2.02 intake valve and its curtain area limits you to about a 3.3 sq inch port size if max effective, non-supercharged air flow is to be maintained
porting+valve_area.jpg

Id point out I think part of the reason the dyno charts are limited to about 6200 rpm,
is the result of both the potential loss of valve train stability, with a hydraulic roller sbc valve train,
and the potential limits on safe piston speeds to longer term durability.
Id also point out that in most cases the stock cars exhaust system will not allow the exhaust flow.
and enhanced cylinder scavenging, required to,
allow the extended intake flow rates to become a useable factor in the engines power curve
then of course port stall speed as the ports cross sectional area will limit the air flow entering the cylinder
in most cases that intake port cross sectional area or the exhaust port flow will stall,
limiting and higher rpm power gains.

on a 383 SBC your port must be at least 2.17 sq inches minimum,
and at about 2.45 sq inches your maxing out the potential flow at 6200 rpm
if your current intake runner or port size in the heads is not at least 2.45 sq inches or greater your reaching port stall
ideally you'll want about 3.0-3.2 sq inches on that intake runner and port size if you want to push rpms/power and match the intake flow are to feed the cylinders at lets say 7000 rpm

Stan Weiss' - Automotive Performance Software / Interactive JavaScript to Calculate an Engine's Port Limiting Velocity

JavaScript Calculators designed for the auto enthusiast. Which will do math for YOU. Interactive JavaScript to Calculate an Engine's Port Limiting Velocity
users.erols.com

bits of 383 info

as too costs involved here's one SBC 383 builds partial cost list, which may help you remember some of the costs your more than likely over looking the fact is this engine building remains mostly well understood and known science, a teachable skill, (for anyone willing to learn what works with a...
garage.grumpysperformance.com

unshrouding valves, and polishing combustion chambers

yea it would be nice to come up with the cash to do some amazing build but ultimately as is so often the case the finances arent there. gotta work with what we got i guess...
garage.grumpysperformance.com

tumble and swirl, quench & squish

I could fill chapters on these subjects, but its basically not something the average engine builder assembling off the shelf parts needs to be overly concerned with other than to understand the potential power may change due to the parts selected and the careful assembly and measurement during...
garage.grumpysperformance.com

multi-angle valve job related

for a valve to function correctly it needs to both seal completely when seated against the head and allow efficient flow between the valve seat and underside of the valve as it lifts off its seat, the curtain area( that's BASICALLY, the distance the valve is off its seat times the valve...
garage.grumpysperformance.com

Air Velocity Speed Limit: Max Velocity Heads + Tuned Intake = Turbulence?

Here's a question I've been pondering; it has 2 constituent parts/ ideas that come together to make the question possible so bear with me: 1. Modern SBC "Street" heads like the AFRs and Profilers have been laser-focused on keeping air speeds up and maximizing airflow velocity to improve torque...
garage.grumpysperformance.com

COMMON SBC INTAKE PORTS
felpro # 1204=Port Size: 1.23" x 1.99"=2.448 sq inches

felpro # 1205=Port Size: 1.28" x 2.09"=2.67 sq inches

felpro # 1206=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1207=Port Size: 1.38" x 2.28"=3.146 sq inches

felpro # 1209=Port Size: 1.38" x 2.38"=3.28 sq inches

felpro # 1255 VORTEC=Port Size: 1.08" x 2.16"-2.33 sq inches

felpro # 1263=Port Size: 1.31" x 2.02"=2.65 sq inches

felpro # 1266=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1284 LT1=Port Size: 1.25 x 2.04''=2.55 sq inches

felpro # 1289 FASTBURN=Port Size: 1.30" x 2.31" 3.00 sq inches

http://users.erols.com/srweiss/calccsa.htm

http://garage.grumpysperformance.co...-calculators-and-basic-math.10705/#post-50173

http://garage.grumpysperformance.com/index.php?threads/port-and-runner-math.148/#post-34936

http://garage.grumpysperformance.co...at-angles-and-air-flow.8460/page-2#post-33298

http://garage.grumpysperformance.co...build-the-engine-to-match-the-cam-specs.11764

https://mechanics.stackexchange.com...runner-length-effect-the-power-curve-of-a-car

https://www.musclecardiy.com/performance/induction-math-high-performance-engines/

calculate horse power from intake port flow rates
http://www.wallaceracing.com/calcafhp.php

http://www.wallaceracing.com/calchpaf.php

http://www.wallaceracing.com/ca-calc.php

http://www.wallaceracing.com/max-rpm.php

http://www.wallaceracing.com/lpv.php

http://www.wallaceracing.com/chokepoint.php

http://www.wallaceracing.com/chokepoint-rpm.php

port speeds and area

I CAN,T EVEN TELL YOU HOW INSANE SOME CONVERSATIONS I HAVE SEEN GUYS GET EVOLVED IN ARE! GUYS TELL YOU A 210CC air flow research HEADS GOING TO ABSOLUTELY KILL Torque ON A 383 BUT ITS FINE FOR A 400 SBC, WHAT TOTAL b.s, your cylinder heads port size needs to be selected with both displacement...
garage.grumpysperformance.com







 
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Thanks Grumpy.

I'm going to talk through one other subject that's come up for me that I haven't really had anyone else to bounce it off of just to see if I'm making a mistake somewhere:

I'll eventually make it back to here with more dyno graphs and comparisons to the 2nd wave, but I took a look at Stan Weiss's MPCSA calculator and I might be using it wrong, but I'm finding that it gets really close but not exactly the results at Chad Speier's formula documented here:


Chad Speier formulas for estimating required intake port volumes for a given engine size and desired HP Peak RPM:
#1 Intake Min CSA Required for Engine Size & RPM:

Chad seems to use: MIN CSA = (bore x bore x stroke x RPM x .00353) / 613.8 (.55 MACH x 1116 fps)

He explains that he's "set" .55 Mach or 613.8 as his desired max FPS for a given head on a given cubic inch engine at the max desired RPM, because he finds that that's the "speed limit" for the type of ports that he works on so we see that in the formula that he uses as a constant, but it's actually a variable. (23 deg SBC stuff, mostly.)


Although I've found the Min CSA on SOME common heads on the internet (AFR is one of the few MFGRs that just lists the Min CSA of every head), the majority of the time I can't find the MIN CSA spec.

Chad explained that you can either MEASURE the min CSA of the head, OR if you have the port centerline length, it's really easy to convert from min CSA to the port volume using another formula:

#2 Converting Min CSA to Port Volume in CC:
Min CSA to Port Volume in CCs:
Port Volume in CCs= Min CSA * Port Length * 16.387

He then provides an even cruder, but more accessible and probably "good enough" shortcut, since many SBC heads have an intake port centerline length close to 5.45", so we can just use:

Min CSA to Port Volume in CCs (for 23 deg SBC heads):
Port Volume in CCs (SBCs)= Min CSA * 5.45 * 16.387 -> I've played with this looking at the advertised min CSA and port volume of a few SBC heads and it seems to under estimate the port volume for some reason, but I'm not clear on why. [Edit] Duh, it's because this formula should be using the AVG CSA, not the min CSA.



Two Examples:
Example One: SBC 350 with a desired 6,000 RPM HP Peak:
MIN CSA = (bore x bore x stroke x RPM x .00353) / 613.8
(4.0" * 4.0" * 3.48" * 6,000 RPM * .00353) /613.8
1,179.3 / 613.8 = 1.92" Min CSA to avoid going over 613.8 FPS at the choke

Port Volume in CCs (SBCs) = 1.92" min csa * 5.45" * 16.387
Port Volume in CCs = 171.5cc

-> If I use Stan Weiss's tool for a 350 @ 6,000 RPM and a port limiting velocity of 613.8, it says that the Min CSA should be 1.925" (really close)

I was super confused at why the min CSA to port volume estimate formula seems to always underestimate port volumes vs. actual heads that you see (they're always slightly larger), and it finally dawned on me that the only way to calculate volume is with the AVERAGE CSA * the port length, so this is clearly a short cut. And additionally of course the head MFGRs have to enlarge the port towards the entry to the next largest gasket size for standardization and to get some taper on the way to the pinch.

I've also heard that really good heads can actually sustain higher max velocity before going turbulent. (AFR 180cc heads don't stop making power @ 6,000 RPM on a 350 even though the formula says they're reaching 613.8 fps at the choke.

If 172cc or there about of intake port volume is what's required for a typical 350 SBC to reach a peak of 6,000 RPM, then it makes sense than that the typical 180 - 185cc head is designed to carry a little bit beyond 6,000 RPM on a 350. (No surprises so far, except for the weird #'s from the AFR head).


Example Two: SBC 383 @ 6,000 RPM HP Peak:
Min CSA= (4.03" x 4.03" x 3.75" x 6,000 RPM x 0.00353) / 613.8
4.03*4.03*3.75*6,000=365,420.2 365,420.2*0.00353=1,289.9 1,289.9/613.8=2.1" min CSA

Port Volume in CCs = 2.1" * 5.45 * 16.387 = 187.5cc
->Again makes sense as we normally see 190cc-195cc heads often recommended for these <6,000 RPM 383s.

The AFR 195 Comp lists a 2.1" min CSA; the Profiler 195cc head has a 2.15" min CSA per Chad Speier, so both seem sized perfectly for a street 383, with the port speeds a tiny bit faster on the AFR (no surprises there...).




A different approach to estimating port speed at the port's choke point:
Port Speed in FPS = (CFM * 2.4) / CSA

I like the simplicity of this one, just looking at how much air is flowing through a port and then adjusting for the size of the port at it's smallest. This is where it becomes clear that the efficient ports that flow a ton vs. their min CSA are, of course higher velocity.

This seems to only work if the actual depression is 28" of water exactly; not sure what to do with that, so I'll "park" it.


Profiler 195cc Head port speed #'s (2.15" min CSA)
.200" lift, intake 145 CFM
.400" lift, intake 254 CFM
.600" lift, intake 274 CFM

If the cam's intake lobe reaches a max lift of .600" lift, then:
(274 CFM * 2.4) / 2.15" = 305.8 FPS


Profiler 210cc Head Port Speed #'s (2.19" min CSA)
.200" lift, intake 145 CFM
.400" lift, intake 258 CFM
.600" lift, intake 285 CFM

If the cam's intake lobe reaches a max lift of .600" lift then:
(285 CFM * 2.4) / 2.19" = 312.3 FPS

<---This seems odd, but because the 210cc head flows more for a given CSA vs. the 195cc head, it seems that you'd actually have more velocity through the port with the larger 210cc head...


I did this for a bunch of heads and compared to the AFR heads, which had the best CFM per min CSA of any head I looked at, so had the highest velocity numbers (although it seems that I've lost that data and don't feel like generating it again right now.)


Chad Speier Racing's new CNC 205cc S Factor Head for Giggles, because I know he's a "high velocity" guy and because he actually gives out flow and min and avg CSA data (2.03 min CSA; 2.35" AVG CSA)

.200" lift, intake 147 CFM
.400" lift, intake 256 CFM
.600" lift, intake 303 CFM

At .600" lift (and with 28" of depression across the valve):
(303 CFM * 2.4) / 2.03" = 358.2 FPS!
--Head said "Airspeeds on the faster side for drivability!"

And because Chad gives the EXACT intake centerline length of his head of 5.33, I can actually use the avg CSA and port centerline formula to convert accurately between avg CSA and intake port volume accurately for once!

2.35*5.33*16.387= 2.05.3cc.



I've enjoyed playing with some engine math, anyway.
I went so far as generating the valve curtain area and then looking at the speed of the airflow through the port choke point vs. the airflow through valve curtain area for every .100" lift and then looking at when the valve finally opens enough that the max velocity moves from the valve curtain to the port, and then doing it again with a bigger intake valve. Time consuming geeky fun! ;-)


Adam
 
ID point out that runner air mass & charge inertia stacking up behind the intake valve is at least partly influenced by the length and cross sectional area, in the same way that header primary length & cross sectional has an effect on the DRAW, or negative pressure wave that helps draw in the next intake charge during valve overlap, thats one factor that tends to make the use of tighter LSA, in cams used with stack injection, and use of open headers with a longer effective header collector length, have a wider torque curve in my experience.
its also a factor in why larger diameter cross sectional area , moves the effective torque curve higher in the rpm range and why running a bit richer fuel air ratio tends to run a bit better using stack injection or tunnel ram intakes and to a lesser extent single plane vs dual plane intakes.
that longer and effectively greater mass of intake charge and matching mass of exhaust gasses, have a combined and effectively complimentary effect at higher rpms during that period of valve timing OVERLAP, that greatly adds to cylinder scavenging, as it helps remove spent /burnt exhaust gases, and once the exhaust valve seats the inertia ram effect helps stack a bit more volume of intake charge into the cylinder.
you can feel this and see it in dyno graphs if you compare a stack injection and properly matched header with a tight LSA cam in a high compression engine, vs the basically similar combo with a single plane intake , where you see a marked loss of power in the single plane intake vs the stack injection on what would otherwise be almost identical engine combos, where the shorter and lesser intake charge mass just can't match the cylinder scavenging efficiency, at stacking more intake mass of F/A or scavenging the exhaust as effectively.
I've always rather been amused at the reaction I've seen when I suggest stack injection or a properly tuned tunnel ram intake and a tighter LSA cam, may noticeably boost the engine power band, most guys just don't think there's potentially that much power to be gained, with the swap, and seem shocked and pleasantly surprised with the difference in seat of the pants acceleration/torque they can feel.
I know that the difference when I ran crower stack injection was an instant 3 tenths faster and several extra MPH in the lights
just swapping intakes styles (dominator/single plane vs crower stack injection) on my 13.7:1 COMPRESSION RATIO, 496 BBC
FAST_bbcdc_weldon-1024x825.jpg

CROWER no longer sells the exact cam I used but it was very similar to the current
#01486

Chevrolet Mechanical Roller Camshaft - Camshafts

Chevy 396-454 Roller 8620 Steel Billet Camshaft
www.crower.com
www.crower.com


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exhaustpressure.jpg




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He then provides an even cruder, but more accessible and probably "good enough" shortcut, since many SBC heads have an intake port centerline length close to 5.45", so we can just use:
I can confirm that dimension. When designing headers with the software called Pipemax, it wants the length of the centerline for both intake and exhaust. Using a pretty accurate method used by Larry Meaux (Author of Pipemax) for determining the CL, I also came up with 5.45 inches for the intake in my Brodix IK200 heads.


An interesting fact that the Edelbrock dual plane Air Gap 7501 has the same port length on cylinder #5 of 5.45 inches.
 
Using a pretty accurate method used by Larry Meaux (Author of Pipemax) for determining the CL, I also came up with 5.45 inches for the intake in my Brodix IK200 heads.
What's this pretty accurate method?

Run a string / wire through the center of the port and then just measure the length, or are you doing math on the poured port volume and the average CSA to calculate the port length?

(I've got a single PC license of the previous version of Pipemax, but I'm considering buying a "proper" 3 PC copy of the newest version; I just get a new computer every 2 1/2 years from work, which makes my licenses expire faster than most people....)

Adam
 
Using some 1/8" wide masking tape run a strip along the short side and also the long side. Mark them at each end, then remove them, lay them out straight and measure. Take the average of the two to get the centerline length.

All the pics and more are contained in the link below:
The title says Dynomation, but I ended up using Pipemax 4.5 and/or 4.7

FP08_PortRunnerMeasurements01_01593.jpg

FP08_PortRunnerMeasurements02_01597.jpg
FP08_PortRunnerMeasurements03_01599.jpg
FP08_PortRunnerMeasurements04_01603.jpg
 
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Wow. So relatively simple and seems accurate. REALLY great stuff.

I'm only through page 1 but loving your header design using dynomation thread already! (The UI of the new Pipemax is SIGNIFICANTLY different vs. my version.)

Adam
 
Wow. So relatively simple and seems accurate. REALLY great stuff.
Certainly alot easier than my first attempt at forming a wire that would approximate the centerline. I still to this day check the Pipemax forum everyday. It's not very active, but it does have some good stuff. If you are into flow benches, then it good for that also. Larry Meaux always answers any post where he can help. In fact he took my Pipemax file and reworked it to fix somethings that could be better than I had it.

Larry Atherton of DynoSim and Dynomation (Motion Software) is the same way. We have worked together several times on some bugs and he's given me credit in the update file when the new version came out. Which I thought was really nice of him !
 
Larry Atherton of DynoSim and Dynomation (Motion Software) is the same way. We have worked together several times on some bugs and he's given me credit in the update file when the new version came out. Which I thought was really nice of him !
I have his 2015 Small Block Chevy's book and I did NOT know he was the DynoSim / Dynomation guy.

Adam
 
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