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Stated earlier: 1986 IROC. Flat-top 355, TFS G1 heads, 218/228-110 cam, TH350, 3,000 stall, 3.23 gears, 26x11 ET Streets. Similar weather conditions and same track.
Never had the heads flowed, but best guess going on published and independent testing they flowed in the 230-240/189-200 range at .500, which was right at the cam lift using the 1.6 rockers. Cam was a Comp custom grind (more suited for a shorter runner intake) I had laying around - like most all the parts I used to put that car together.
I'm going to disagree here. The short-runner intake will provide a wider torque and power curve than the TPI-length runners, all else being equal. It is far more suited to wider gear spacing and less use of shifting overall. The TPI intake makes for a peakier engine, since it lops at least 1000rpm off the useful RPM range of any engine. The short-runner intake also provides more average power for the same reason. You're equating short-runner intakes to peaky engines that only make power at very high RPMs, but that is not accurate. A stock L98 made no more torque off idle than the LT1. It only made more torque for a narrow band around it's torque peak, and then the aforementioned cliff took place. The LT1 provided a much broader and flatter torque curve and was equally strong off idle, while extending usefully for an extra 1000rpm.
Just fit a blower, simple way to boost a TPI engine.
more torque and more h/p everywhere, very reliable and the TPI doest choke like naturally aspirated under boost giving you a higher rpm range.
The first step in more seat of the pants performance is long tube headers, then an adjustable fuel pressure regulator.
If you want more go a blower or more cubic inches and go to a miniram intake and new alloy heads for any cam upgrade.
Just fit a blower, simple way to boost a TPI engine.
more torque and more h/p everywhere, very reliable and the TPI doest choke like naturally aspirated under boost giving you a higher rpm range.
The first step in more seat of the pants performance is long tube headers, then an adjustable fuel pressure regulator.
If you want more go a blower or more cubic inches and go to a miniram intake and new alloy heads for any cam upgrade.
While forced induction will give you a little bit more RPM (and a lot more power), the peak power RPM will still be affected by the long runner length of the TPI intake. The blower alone won't raise the peak power RPM by much.
The power output of the engine is also directly related to the shape of the boost curve. As boost isn't linear (even with a centrifugal supercharger) the power gain isn't the same across the RPM range.
Just fit a blower, simple way to boost a TPI engine.
more torque and more h/p everywhere, very reliable and the TPI doest choke like naturally aspirated under boost giving you a higher rpm range.
Boost doesn't extend the RPM range. The curve remains the same shape....just higher numbers.
Boost doesn't extend the RPM range. The curve remains the same shape....just higher numbers.
If all else stays the same, in most cases boost will raise the RPM a bit because it increases the pressure differential from the intake port to the exhaust port. It essentially tricks the engine into thinking it flows better than it really does. I don't know how true that is with a TPI intake though, because of the anti-phase resonance that blocks flow above roughly 4500rpm. It might increase the anti-phase pulse as much as the overall intake pressure, which might cancel out the pressure differential.
If all else stays the same, in most cases boost will raise the RPM a bit because it increases the pressure differential from the intake port to the exhaust port. It essentially tricks the engine into thinking it flows better than it really does. I don't know how true that is with a TPI intake though, because of the anti-phase resonance that blocks flow above roughly 4500rpm. It might increase the anti-phase pulse as much as the overall intake pressure, which might cancel out the pressure differential.
If I had a little more free time (and free play money) , I would run my setup on the same dyno again with the turbocharger to intake piping disconnected. It would be interesting to see how it would affect the overall shape of both the horsepower and torque curves as well as the overall numbers. (Who knows, maybe I'll do just that for the data.) I'm guessing my horsepower peak would drop by a couple hundred RPM.
I'm seriously thinking of ditching the intake setup i currently have for the Miniram. I will have to have the car retuned when I do that and will have it done on the same dyno as the last time. If I do, I'll share the dyno results for that change (with no other changes) as well.
Even though my setup is somewhat unusual, I figure more data made available is very valuable to someone looking at intakes.
Richard Holdner covers this very topic, repeatedly in his vids. Here is a screen shot from a recent vid: 500" caddy is the "low" hp&tq graph...5.5 lbs of boost on the same engine is the "higher" curves. Note the shapes of the NA and boosted curves:
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.
