Hi all,
Bit of an odd one, just wanted to ask how best to limit the torque output via the engine mapping, the basis of this question is owing to the torque limit on my transmission - basically looking to limit peak torque in certain scenarios. I will be getting my forged engine fully mapped on a rolling road but just wanted to ask the question now.
Basically my forged engine will have the capacity to have a higher torque output than my upgraded gearbox is rated to, I know that my gearbox can cope with slightly more than its rated torque but am looking at how to limit peak torque when needed - a bit like an engine rev limiter.
I am guessing I should be able to limit the torque by pulling timing out in certain cells at certain boost levels using a 3D table?
Eg:
7 psi - no adjustment
14 psi - no adjustment
21 psi - some adjustment
28 psi - more adjustment
For my build, here are my limits (to give everyone an idea):
1.8 Litre engine
Forged rods and pistons (9.5:1 compression)
Supertech valvetrain rated to 8,500rpm
CSS strengthened block able to cope with around 600bhp
Stock gearbox with upgraded 3rd and 4th gears - rated to 295ft/lbs although have chatted to someone who ran 365 ft/lbs through them
Now, a stock engine with a low boost turbo (7psi) makes around 220 bhp and 185 ft/lb torque, and probably around 250bhp and 200ft/lbs at 12 psi, have seen figures for a forged engine making around 420bhp and the 365 ft/lbs at 35 psi on a GT3071 turbo, I am looking at an EFR 6758 for my build which should flow well at lower boost but not run out of legs at the top end.
Is anyone able to guesstimate the sort of torque I should be expecting? I think I should be ok with a bar of boost in terms of torque but anything more I think I might need to run a limit of some sort to keep it around the 300ft/lb mark - basically looking to make the most power I can (as the rest of the engine can make it). I have also seen these engine make around 500bhp at 7,500 rpm and 28psi on a 6262 but the peak torque is probably at around 460 ft/lbs - tad much!
Plan for my build is an 11 second 1/4 mile car but daily driven - plan to run full power at the drag strip then drop boost pressure to a lot lower for the road - basically looking to make sure that the gearbox holds ok for the couple of drag runs to prove it can run the time but then turn it down at all other times.
Sorry - was a bit of a long post but was just wondering what everyone suggests.
