bigSS

Did my first dyno runs up at Speed Inc. the other day. Happy with the numbers, but i'm running lean and getting knock retard.

Jim tuned the car N/A, and got 368rwhp. No knock retard of course.

Then we decided to try the bottle. Went with the 150 jets (62 n20, 33 fuel). Numbers were 494 rwhp and 545 rwtq. I was happy with that, but jim told me that I was getting 7 degrees knock retard and it was running very lean on the lower to middle end (15:1 or so) but richening up to around 13.5:1 on the top end. He figured we were just running outa fuel.... but I have a racetronix in tank fuel pump, so we eliminated that.

So we put in a larger fuel jet (38) and went at it again. Well, that added 55 ft lbs of torque.... taking the number to 494rwhp and 600.2 rwtq!! I was very happy with that, but then he told me I was STILL getting 5 degrees knock retard and still lean from around 3800rpm to about 4800rpm, but the upper end was good.

I'll post the graph later... but I need help figuring out what the problem might be. Here are some details.

-1000psi bottle pressure... dyno run started w/ nitrous engaged at 3800rpm.
-increasing the fuel jet size from 33 to 38 decreased knock retard by 2 degrees and added 55rwtq.
-1/8 tank 93 octane w/ 3 gallons 106 unleaded
-no idea what fuel pressure is
-also, car looses fuel pressure when cold (did this before the fuel pump)

Not sure what that problem is! Any ideas are appreciated!

Draco

You might be spiking lean at the start due to the returnless fuel rail setup. The regulator is near the tank, and thus doesnt see the pressure drop as quickly as it would if it were on the rail like the 97-98s have it. Some people have done this conversion and eliminated the lean spike.

What is your timing under nitrous use? For a 150 shot I would try to pull 6* for timing around 22-23. This will be safer and may also hit harder due to the faster burn rates with nitrous use. I pull 6* using a home made timing tricker for my dual stage 175 shot.

I would also shoot for an AFR in the high 11's or low 12's once you get the lean spike sorted out. I personally run low 11 AFR to be as safe as possible.

bigSS

Thanks Draco, anyone else?

koolrayz

iTrader: (26)

an aftermarket fuel regulator aeromotive#13109 like the one i installed will help
http://cofba.org/users/koolrayz/2004_0503_115648AA.JPG
http://cofba.org/users/koolrayz/2004_0503_115537AA.JPG
http://cofba.org/users/koolrayz/2004_0503_115838AA.JPG

Racetronix

iTrader: (2)

Placing the FPR at the back of the car is incorrect.
The FPR should be rail mounted to address the problem with the factory returnless system.

Please see these threads:

https://ls1tech.com/forums/fueling-injection/127433-those-running-dual-fuel-pumps.html

https://ls1tech.com/forums/fueling-injection/177066-boost-pump-simple-wiring-question.html

Before you go to this trouble check your FP with a gauge. This should have been done during the tuning process.