gideon

hey guys, i recently got my car dynoed with a mustang dyno. it put out 313 hp & 330 torque. but the a/f ratio started at 14:1 and went to 17:1 at wot. im using 24lb injectors & my fuel pressure is at 43 psi. any ideas on how to get the a/f ratio down between 12-13??

PRO50SC

What was the pressure at wot? Did you have a gauge connected? What did the tuner say?

gideon

not sure did not have a gauge hooked up to it. the guys at the shop said to put 30lb injectors on it and get a tune (chip). but i thought for sure 24lb injectors would be plenty for 300 horse.

PRO50SC

24's should be plenty. Maybe find another tuner.

gideon

if 24's are enough then whats causing it to go lean? i have a 255 pump so its not that. im going to try and up the fuel pressure i think with an adjustable regulator. not sure whats causing it.

5.0kid

sounds like your tuner needs to have longer pulses for the injector, so that they stay open longer and deliver more fuel

gideon

i havent got it tuned yet. i was hoping to fix the problem without getting it tuned. looks like i will have to tune it to fix the problem. didnt think fuel would be an issue with 24lb injectors & a 255 pump.

5.0kid

it shouldnt be an issue sounds more like a tuning issue in the amount of pulse width in the tune, i bet if they were to stay open longer u wouldnt have a problem.

Derf00

+1
The pressure seems a little Low. Both the stang (08 GT) and the wife's Escape (06 escape that uses the same 24lb injectors as the stang (yes it's true) run at about 45-46 idle and 55ish at WOT (I say ish because I was watching the road at that point ).

I'm not as familiar with pre OBDII injection systems but I believe they (OBDI and II) have both ST (short term) and LT (long term) FT (fuel trim). See if your tuner can view what they are during the dyno.

Fuel trim is the duration of your injectors. A positive value means the car is adding fuel by pulsing the injector longer, meaning it's trying to correct a lean condition. A negative value, means a shorter pulse, meaning trying to lean it out.

A Bank is a bank of cylinders Bank 1 = side where cylinder 1 is located, Bank 2 = other side.
Banks 1 and 2 LTFT should be no further apart than +/- 5% on their correction value accross the board. In other words, if Bank 1 is +2.5 and Bank 2 is reading -2.5 thats the outer limit. Anything beyond that and you could be looking at a plugged injector or other items. If the battery was recently disconnected this data is less reliable because LTFT is an accumulation over time.

For LTFT '0' for both banks 1 and 2 is ideal but again +/-5% of each other is fine

STFT shouldn't swing more than +/-15% under most conditions and should never be constant.

If both banks jump higher than 10 - 15 points your system is being starved at that moment. Either your pressure is low or you have clogged injectors.

gideon

how do i check the injectors to see if they are clogged?