TitaniumTT's I hope I make it to DGRR '09 Build

[NoDOHC]

Quote:

Where did all of those numbers come from?

I am so sorry, I never explained a thing.

You said that you are at sea level. Thus atmospheric pressure is 14.8 psi.

You said that you were running 11.5 psi of boost. This means that your intake manifold pressure was 14.8 (atmosphere) + 11.5 (boost) or 26.3 psia.

I was running about 14.5 psia at 6700 rpm (800 ft of altitude, no turbo).

A rule of thumb for diesel engines is that the torque boosted = the naturally aspirated torque X the boost ratio (absolute manifold pressure ratio). Diesel engines all run lean of stoic and the AFR is basically the same for turbo and NA.

Thus, if a diesel engine made 159 Wlb-ft at 800 ft elevation Naturally aspirated, it would make 159*(14.8+11.5)/14.5 or 288 lb-ft of torque at 11.5 psi boost and sea level.

I was thrilled to discover that your engine made 283 Wlb-ft of torque at 11.5 psi, as that is very close to that rule of thumb. (Obviously, the rule of thumb is seldom true for gasoline engines due to the excessively rich fuel mixes that must be run for a reliable turbo setup). I always theorized that if the AFR were the same on a boosted engine as it was on a NA engine, the ratio would work out (and it did).

Now unfortunately, You have a better compression ratio (which helps your power) and a better intake manifold, so there is a good chance that I will not see these improvements when I turbocharge my engine. But I really do intend to run at 13.0:1 AFR at 14.5 psi boost and I am relying on my intercooler, my low compression ratio and my ultra-polished combustion chambers to save me from detonation.

First I must experiment with the effects of compression ratio on a NA engine before I put the 8.2:1 rotors back in and install the turbo.