SBC TPI 383 ways to reduce torque

[steveo]

you can absolutely put a built engine behind a tpi intake and make power. it'll always be at its best with a peanut cam and an engine tuned for low end grunt, though. there's a reason GM stopped making intakes like that - they look cool, but they really suck in the real world. this original point of this thread was about reducing low end torque, and low end torque is the only thing the TPI is really good at, although in my experience tuned intake runners are really unpredictable with modified engines.

[Fast355]

you can absolutely put a built engine behind a tpi intake and make power. it'll always be at its best with a peanut cam and an engine tuned for low end grunt, though. there's a reason GM stopped making intakes like that - they look cool, but they really suck in the real world. this original point of this thread was about reducing low end torque, and low end torque is the only thing the TPI is really good at, although in my experience tuned intake runners are really unpredictable with modified engines.

I do not agree at all. No other intake except the belt driven kind will make more mid-range torque. NONE of them!

[steveo]

i've seen then have good mid range VE boost on some engines at not others. i'm willing to bet the cam was the determining factor, since intake closing events are the primary driving force behind a tuned runner like that. the stock LB9/L89 cams really rip in the mid range..

[sanderson231]

I do not agree at all. No other intake except the belt driven kind will make more mid-range torque. NONE of them!

I do not agree at all. No other intake except the belt driven kind will make more mid-range torque. NONE of them!

I watched a couple of the Richard Holdener videos and it is crazy how much peak torque the TPI intake makes. But the problem is that the OP is concerned about too much torque. So that leaves three options; 1) detune the engine to make less torque (and give up HP), 2) drive the car conservatively or 3) use a different intake. I like sports cars that feel like sports cars (Quad 4 in a Pontiac Fiero) so I would select the latter.

There is a lot of reasonable experience in the Fiero World running V-8's and 3800 supercharged engines on a 5 speed, manual transaxle rated for 200 ft-lb. So I think that GM's torque ratings are conservative. I suspect that the 383 the OP has chosen with a TPI intake would be reliable with no other torque management than reasonable use of the right foot.

[nilak]

I watched a couple of the Richard Holdener videos and it is crazy how much peak torque the TPI intake makes. But the problem is that the OP is concerned about too much torque. So that leaves three options; 1) detune the engine to make less torque (and give up HP), 2) drive the car conservatively or 3) use a different intake. I like sports cars that feel like sports cars (Quad 4 in a Pontiac Fiero) so I would select the latter.

There is a lot of reasonable experience in the Fiero World running V-8's and 3800 supercharged engines on a 5 speed, manual transaxle rated for 200 ft-lb. So I think that GM's torque ratings are conservative. I suspect that the 383 the OP has chosen with a TPI intake would be reliable with no other torque management than reasonable use of the right foot.

The car is registered as historical, I have no idea what kind of checking they will do for the next inspections so it’s safer to stick with the stock intake.
I can apply appropriate throttle and that will be more efficient and safer for the engine but I don’t know how consistent can I be. The engine can produce high torque even at a small opening of the flap, but It should be that hard

[steveo]

the logic still seems weird to me. you could choose any engine in the world, you went and chose one that you feel is way too powerful, and you want to repair that error electronically to make exactly the powerband you want.

it's possible to get close by making your ignition and AFR totally incorrect (a purposefully bad tune) but considering there is a gigantic lobe filled rod that contains most of the actual parameters controlling your powerband, if you really want to reduce low end torque and increase high end power, and the bore and stroke must remain the same, the correct parameter to modify is the cam

are you sure you can't just spend the extra time and money beefing a few things up to handle the power?

[sanderson231]

I just looked up specs on 1991 ZF6 transmission and it is rated for 450 ft-lbs. Not sure what the clutch and rear end is good for but doubt that the transmission is too weak unless you like to rev to 3000 rpm and drop the clutch.

[nilak]

I’ve watched this presentation youtu.be/E0yZdLkpvR0 some while ago and these guys did some extensive research on this transmission. They say it can handle even 475lbft although it’s rated by the manufacturer dor a lower torque (I think 400lbft). But taking into account it’s now over 30 years old and 130k miles, I thought something like 400lbft would be better for reliability. Anyway 12% over 400lbft does seem a huge step, it could be safe.
Another problem can be the the C beam, but that basically depends on the output torque not input (engine) torque and I think can be a problem if you use drag tires even with std engine, 1&2 gears can generate enough torque up to race tires traction break up.