Well I took her out for a drive after 3 weeks of hybernation and I noticed my injector duty was at 96% under boost ( 15 psi ). I know this isn't a good thing but how do I fix it ?

Here is the setup for you guru's that can help out

850/1600 cc injectors and resistors (4 of them )
KG parts fuel rails with -8 lines
Aeromotive FPR set at 32 psi under idle ( vacum line detached )
"Supra" fuel pump
Greddy Elbow
Front mount IC
Garrett 70-1 front w/ .84 rear
3" exhaust
Pettit streetported motor
Rotary Works TB ( installed after tune )

PFC was tuned by Steve back in December of 2009.

Any suggestions are greatly appreciated.

 

what were the AFR's? I had an issue like this years back running 550-1680's and it ended up being way rich up top with 19psi. Pulled some fuel and got it back in the high 80's.

But with your combo and only 15 psi that seems very odd. Have a log of that pull?

 

AFR's are between 11.3 and 10.8 under boost according to my gauge.
No log.. I am gonna get with a friend of mine that has a datalogger to see if we can pull some usefull info.

Thanks

 

Agreed, something isn't right. You would be flowing about 4700cc/min which would be about 25psi manifold pressure at 7500 rpm fully loaded to be at AFR 11 (approximation). Unless fuel pressure is low there seems to be a problem with instrumentation or you are pouring raw fuel down the pipe and fouling plugs. I assume you are obtaining the data from the commander..... You might want to switch to the graph mode and plot the duty to see it this is really happening.

Here is mine flowing 2520 cc/min at 14.4 PSI at 6000 RPM fully loaded and with an AFR of 11.20; note injector duty is 90%.

 

No fouled plugs.
I think the boost may have creeped up to about 17 or 18 psi and that may be the problem.

I will try the graph mode and datalog some info to see.

Thanks for the input guys...

 

Why do you have it set that low? Ive always thought it should be set at 38-40psi with no vac, and you should be at around 32-34 at idle with the vac line attached. What fuel pressure are you seeing at idle when you attach the vac line?

 

32psi is frickin low. That's lower than stock... I think stock is 36 or 38. I run my 720/1680 at 43.5psi (3 bar) which is a very common fuel pressure on other cars. I see 85% duty cycle with 11.0:1 AFR at 16.5psi on T04R turbo (similar to Aspec 500R).

 

Fuel pressure if accurate would be the main contributor, however, why would the tuner set it up that way? If it was tuned at the higher (correct) pressure the problem would be a lean condition due to fuel pressure dropping off. Did you have the car tuned on a dyno so the higher pressuure/rpm ranges could be evaluated?

 

I agree that your base fuel pressure with the engine idling should be at min 38+ psi. I use 40psi because it is easier to add boost to 40 when I read my fuel pressure gauge under boost.

You could also rewire your fuel pump if not already done as the stock wiring drops about 2 volts which is a large power drop.

 

It was set by Steve when it was on the Dyno.
I had it set to 36 and he lowered it before tuning. (mechanical gauge on the FPR )
I am going to pull her out of the garage tonite and warm her up to check the fuel pressure with and without the vac line.

Thanks again for the tips

 

OK... here is an update.

Changed to a Prosport electric fuel gauge in the car and got 50psi readings at idle with NO vacum on it. WTF

Reset the idle pressure to 40 psi then added the vacum line and it dropped to 34psi.
Reset the boost controller down 2lbs

Took her out for a quick blast and the Inj Duty only got to 80.3%
and the boost was at 1.13 bar...

Looks to be ALOT better. I may up the boost 1 lb more and call it a day. I am gonna have to wait till tomorrow cause it started raining when I got back in the driveway.

Thanks to everyone's input so far, we may have it right where it's suppose to be.

 

very cool - it's usually the simplest of things.... Send some of that rain up here to central Fl.