SBC TPI 383 ways to reduce torque

[steveo]

let me ask the question in a way that makes more sense

"how do i reduce the volumetric efficiency of an engine within a certain powerband"

assuming the bore/stroke is already selected the following things affect volumetric efficiency in specific ranges (without affecting it across the board like a restrictor plate)

- camshaft profile (huge effect)
- ignition timing (medium effect)
- scavenging from exhaust configuration (small effect)
- intake runner length (small effect)

so yeah by that logic you probably want a different cam to achieve this goal that i don't agree with

How safe is to block the acceleration enrichment since less fuel means less cooling effect through evaporation of the fuel?

the cooling effect is small and needs to be proportioned against ignition timing to avoid knock. it's really hard to blow up an n/a engine even under heavy load unless you go really lean.

[nilak]

Thank you, The cam profile with a carburettor setup has 468lbft @4000rpm, and 400lbft@5500 420hp495”/.502” Lift, 220°/224° Duration @ .050”, 112 LSA, a different option they tested is 450hp[/B]: .510”/.521” Lift, 231°/236° Duration @ .050”, 111 LSA with 488lbft @4000. So the first cam seems good. I don’t know if it’s worth looking for a different cam with flatter curve, if that’s even possible. The TPI will probably make it worse. I can use large runners, these will raise the torque by like 40lbft everywhere according to a test I’ve seen. Probably they won’t be able to produce as much power as the carburettor configuration which has a smoother flow. I’ve seen test with as much as 80lbft reduction when using 11 degrees of total advance but for that I plan to install and EGT. I already have 1 extra slot for AFR and 2 more at the front of the preconverters (these are 100CPSI metallic).