Quote:
Originally Posted by Dragoneye
So...it's an alternative efficiency gauge?
I'm still confused where the 150.8 came from... But this BMEP...or the cylinder pressures during combustion...can tell us which engine is really the 'best'...hmm..
LLT:
BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT
BMEP = 150.8 x 273 / 219.6
BMEP = 187.5psi
LS3 (Camaro):
BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT
BMEP = 150.8 x 408 / 378.3
BMEP = 162.6psi
So...according to all this, the LLT is notably more efficient at making power than the LS3...
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The 150.8 is a conversion factor. Once you input all the various factors, that is what the equation reduces to, so it is just a scale factor. The calculation you did shows what you might guess, that a 3.6L motor with 273 ftlbs of torque is more efficient than a 6.2l motor with 408 ftlbs of torque. Also remember that the peak torque on the LLT is at 5200rpm whereas on the LS3 it is at 4500 rpm, so the LS3 gives you a more user-friendly power band.
My post was really to show that 2v pushrod technology is just as capable as all the fancy tecnology they use for Indy cars. In other words, the LS3 is running at a relatively low state of tune compared to the LLT. Given a similar state of tune for the LS3-the BMEP will easily reach those numbers shown for the LLT-or about 470 ft lbs of torque at 187psi. Interestingly enough, the GM hot cam motor makes 475 ftlbs of torque at 4500 rpm...
LS3 for the MFW
But no disrespect to the LLT either, it is a nice setup.