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"...
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
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"...
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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