GT2871 USERS. SR motor

[jspaeth]

Originally Posted by slider2828

JSPAETH

I have the same setup but step 1's 264 HKS. Fully built top and bottom... I just run a stock FPR, which definitely works fine. No reason to run an adjustable if you are just going to adjust it to stock. I get about 8PSI at 900RPM on my SR tuned by steve shadows. Now I didn't get 370HP I got about 330 at 17PSI which is a lot for me on a dynodynamics. Stock intake mani, stock exhaust mani on a .84 2871R.

One thing you ARE doing wrong is comparing injector size to the power you make. Really? Come on you know better than that. Power is based on tune, independent on injector size. I ran my DW 600cc's at 330 and it was about 80% and now I am on NISMO/HKS 740's and I think about high 60's to 70%...

BUt really its all in the tune. Put on that stock fpr and see if you have the same problem. The Stock FPR can be used up towards 450WHP... I would trust IT...

Right now you have WAYYY too many variables to tune. You don't trust your setup, so its all hit and miss.... so really just go back to stock FPR. Test on your dyno. Steady state, tune it, check your plugs, and then watch your knock.... Seems like you are rushing things a little....

Thanks for an input. Car is tuned by an expert ....Jeff Evans....CodyAce can vouch for that.

There really aren't "too many" variables.

I am running an Aeromotive FPR set to 43 psi base pressure.

I am running 740 cc injectors.

I AM comparing injector size to power, bc aside from some minor "slop" in guessing the BSFC, you should be able to calculate a theoretical required amount of fuel based upon injector size and duty.

Like I said (and you validated with your post), most people making 350-370 whp with 740 cc injectors are using NOWHERE NEAR 90% of their injector duty.

My car runs well, the tune is pretty good, and the AFRs are not unreasonable (slightly rich 10.5-11 under full boost).

Nothing seems WRONG with the car, except for the fact that it just is unexplainable why so much injector duty is being required for the AFRs and power level and injector size combination I have.


EDIT:

BTW my 370 whp on dynapack is likely slightly lower on Dyno dynamics, maybe like 340 or 350 I would guess. But still, you said for an (almost) identical amount of power, you were requiring only ~70% injector duty with 740s.

Now, if my tune IS too rich, and I were to make it say 11.5-12 AFR at full boost, I think this might bring the MAX injector duties down some, but not 20% from 90% that I am seeing to the 70% you are seeing.

You say power is based on tune, but given a perfect tune and reasonable AFRs, you should again be able to CALCULATE how much fuel you require for an engine to put out XXX whp.


AGAIN, the car runs fine, the tune is good, there are no PROBLEMS. ......it's just sketchy that my duties are so high.


J