SBC TPI 383 ways to reduce torque

[sanderson231]

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.

What I read is that the 92 and earlier ZF6's were German made and rated for 450 ft-lbs. GM licensed the design and in 1993 began making their own. They changed the design of some of the helical gears to lessen gear noise and then rating dropped to 400 ft-lbs.

I also came across a thread where corvette owners were successfully drag racing with the Dana 44 differential and laying down some low 60 ft times. Not sure is you have Dana 36 or the Dana 44 but the 44 sounds strong. I did find info that said the 1993 and later Dana 44's were somewhat stronger.

I think you are being overly paranoid about breaking stuff. Install a good clutch and drive the car. If something breaks upgrade it.

[sanderson231]

C beam upgrade:

https://www.corvetteactioncenter.com...e-beam-plates/

[nilak]

thank you

[1project2many]

This generation of Corvette is traction limited. IME that's going to save the rear axle and transmission. You can reduce the engine torque at a given throttle angle using the tuning methods suggested, by reducing spark advance and delaying or eliminating power enrichment. Eliminating or delaying the onset of power enrichment also reduces fuel consumption. Setting knock retard to quickly reduce spark advance at the start of knock while decreasing the rate at which spark advance is returned to normal is a quick way to pull spark advance without spending large amounts of time re-working the main spark table.

Final drive ratio really is a huge player here. Final drive ratio will determine cruise rpm. Numerically higher or lower FDR will move the engine to an RPM that is below or above peak torque production at a given speed. Numerically higher FDR allows faster acceleration which reduces the amount of time high torque must be applied to the drivetrain. Numerically higher FDR reduces the amount of torque applied to the transmission to result in acceleration. Numerically higher FDR combined with tires selected for acceptable but not excellent traction trains the driver not to apply too much throttle. Mechanically, larger diameter throttle cam and / or altered throttle pedal pivot point will change the ratio of pedal movement to throttle angle change. Changing the relationship so more pedal movement is required per degree of throttle change will allow better control of torque. Many drivers truly appreciate a high torque engine operated by a consistent and easy to control throttle. Many drivetrains live a long and happy life if the car is configured so the driver has more ability to control how much torque is produced.

[steveo]

pedal vs throttle angle is an interesting point to debate. what actually happens when you modify the pedal to throttle plate linkage is there is a very advanced closed loop controller on the other side of the pedal - the driver. the driver takes the input of the desired speed and produces a pedal output and has a neurological response rate that adapts and remembers. i have logged throttle inputs and outputs while modifying drive by wire throttle maps and found the driver naturally compensates to achieve the desired output totally in spite of the linkage over time. in other words, no matter what throttle angle is produced by the pedal, the driver will learn and compensate, and you can't really de-tune an engine with ratios or plate sizes or drive by wire mapping outside of a linear response, for the same reason you can't change the AFR of a closed loop narrowband engine - the controller will just throw your changes out and you are just making things harder for the controller.

[nilak]

I've did a several tests on my new 383. The engine has a 1205 head ports size, ported lower base and ported runners from Edelbrock, ported stock upper plenum, but stock exhaust manifold with racing preconverters and straight trough downpipe and straight through muffler (detachable plugs for noise reduction in town).
I watched some comparisons between different intakes and engines, collected the data and I've made some estimations. The estimated gross power (no accessories and racing headers) would be 434HP@4500rpm which is higher than the builder dyno test on carburettor that is 424@5000rpm. The max net Hp sould be 380HP@4500Rpm; and 657Nm@3800rpm, taking into account the muffler restriction - 5% reduction in power. However, the guys that tested the car, maniflod vs headers probably had a better suited manifold, probably better then mine and in an engine that made 357Hp with good headers. After that, I've decided to make an estimation based on VE and injector BPW as well. I've set a formula in TunerPro that shows instant POWER based on BPW and it shows me 270Hp@3750rpm. Based on VE, by comparing stock charts and stock tune, I got 293@4700rpm and 490Nm@3500rpm. However, when I did some laps on a race track, I pushed it up to 3200 where it would go lean, but still, the telemetry showed it was slightly faster than the stock l98 that was reved to 5000. The spark advance was set to 32* and cut by knock sensor (possibly too sensitive or due to lean mixture 13.2:1) to 29*. So I would say, I should expect around 320 peak HP on the dyno after I finalise the tuning, and at this time. I don't see reasons to need torque reduction spark advance curve. The torque curve is only around 20% higher than stock, and when I drive it, it feels faster, I would say 20% seems close to what it feels like. It pulls hard and spins the wheels much easier but the l98 is not bad either.
VE.jpg
comp.jpg

[nilak]

I've did a several tests on my new 383. The engine has a 1205 head ports size, ported lower base and ported runners from Edelbrock, ported stock upper plenum, but stock exhaust manifold with racing preconverters and straight trough downpipe and straight through muffler (detachable plugs for noise reduction in town).
I watched some comparisons between different intakes and engines, collected the data and I've made some estimations. The estimated gross power (no accessories and racing headers) would be 434HP@4500rpm which is higher than the builder dyno test on carburettor that is 424@5000rpm. The max net Hp sould be 380HP@4500Rpm; and 657Nm@3800rpm, taking into account the muffler restriction - 5% reduction in power. However, the guys that tested the car, maniflod vs headers probably had a better suited manifold, probably better then mine and in an engine that made 357Hp with good headers. After that, I've decided to make an estimation based on VE and injector BPW as well. I've set a formula in TunerPro that shows instant POWER based on BPW and it shows me 270Hp@3750rpm. Based on VE, by comparing stock charts and stock tune, I got 293@4700rpm and 490Nm@3500rpm. However, when I did some laps on a race track, I pushed it up to 3200 where it would go lean, but still, the telemetry showed it was slightly faster than the stock l98 that was reved to 5000. The spark advance was set to 32* and cut by knock sensor (possibly too sensitive or due to lean mixture 13.2:1) to 29*. So I would say, I should expect around 320 peak HP on the dyno after I finalise the tuning, and at this time. I don't see reasons to need torque reduction spark advance curve. The torque curve is only around 20% higher than stock, and when I drive it, it feels faster, I would say 20% seems close to what it feels like. It pulls hard and spins the wheels much easier but the l98 is not bad either.
VE.jpg
comp.jpg