[Thlad]

Is there any way to change ur air/fuel ratio other than a tune??

[jussagt]

Unfortunately no there is not. Essentially when you add a bigger MAF & Bigger Injectors.. the engine is getting more Air & Fuel but the computer used to the stock tune (Air/Fuel Ratio) so their for you need to have the computer re-tuned to the new mods and correctly adjusted.

Our cars are pretty hard to tune do to the new computer they put in the cars but their is a nice program / setup for the Do-It-Yourselfs. Its Moates Quarter Horse. Very nice program, and an excellent price. Out the door with everything you need is right around $350-400 compared to the $700 Anderson PMS system that lacks a few features the Q.H. program has.

[Trick Tuners]

The QH is a sweet DIY option, but it is probably "over the heads" of the non tech savvy guys. You can use fuel pressure as a hack way of altering the AFR, but the question is why do you need to change it?

[Thlad]

its way to rich since i put the bigger injectors in. i figured the mas would fix it... it did help but i can still smell it when im idling at a light

[Trick Tuners]

You can use the fuel pressure as a hack way to get everything back in line. Take the stock injector #/hr rate over the new #/hr rate and then multiply that by 39 to get your new psi.

Ex. 19/24= 0.792
0.792x 39psi = 30.9psi.

So set the FPR to 30.9 psi and it should get you close. This will "work" as long as you don't go wild with the injector size. Tuning is always a better option because the fuel atomizes better at higher psi. I would try not to ever go lower than about 30 psi.

You should also read this for info on closed loop fuel control by the stock 02 sensors.
Open and Closed loop Fueling and Fuel Trims - Trick Tuners Forums
The stock sensors can deal with up to about 25% correction for all part throttle AFR calculations. Once you get past that limit it will ignore the maf and run off the stock tables (so it will be even richer!).

[Thlad]

Ok thanks a lot for the info!!

[mustangbrad94gt]

yeah, what trick tuners said, also clocking maf will help on idle too

[ryanw]

Originally Posted by Trick Tuners You can use the fuel pressure as a hack way to get everything back in line. Take the stock injector #/hr rate over the new #/hr rate and then multiply that by 39 to get your new psi. Ex. 19/24= 0.792 0.792x 39psi = 30.9psi. So set the FPR to 30.9 psi and it should get you close. This will "work" as long as you don't go wild with the injector size. Tuning is always a better option because the fuel atomizes better at higher psi. I would try not to ever go lower than about 30 psi. You should also read this for info on closed loop fuel control by the stock 02 sensors. Open and Closed loop Fueling and Fuel Trims - Trick Tuners Forums The stock sensors can deal with up to about 25% correction for all part throttle AFR calculations. Once you get past that limit it will ignore the maf and run off the stock tables (so it will be even richer!).

Thats some good info thanks. does that change at all whem you install a bigger fuel pump ? and would you say that lowering your fuel pressure is only needed if injectors is your only mod

[Trick Tuners]

Originally Posted by ryanw Thats some good info thanks. does that change at all whem you install a bigger fuel pump ? and would you say that lowering your fuel pressure is only needed if injectors is your only mod

The fuel pump does not matter until you go so big that the return line is not big enough and the pressure will start to creep up. Like I said before, tweaking the fuel pressure is a hack and is not ideal. There is no point on adding injectors if they are your only mod. Injectors will never ever add even 1hp unless the ones you are currently using are causing a lean condition from being maxed out.

[ryanw]

Originally Posted by Trick Tuners The fuel pump does not matter until you go so big that the return line is not big enough and the pressure will start to creep up. Like I said before, tweaking the fuel pressure is a hack and is not ideal. There is no point on adding injectors if they are your only mod. Injectors will never ever add even 1hp unless the ones you are currently using are causing a lean condition from being maxed out.

I understand. i have full exhaust from headers catted x pipe through to the tail pipes so its about as free flowing as its going to get, ported cobra intake, 75mm mass, 70mmTb 24lb injectors, 255lph fuel pump and i had some dart heads that i never ended up installing and sold. any ways the 19lb injectors and stock mass air are long gone so theres no going back. and i do smell fuel in the exhaust. but i still pass smog. and seems to run fine. do you think i should dial down my fuel pressure ?

[Trick Tuners]

Thats up to you. Personally i would retune it, but that is easy for me to say and do!

[ryanw]

Originally Posted by Trick Tuners Thats up to you. Personally i would retune it, but that is easy for me to say and do!

I cant return the mass air and injectors there like 10 years old now lol

[JakeM]

Retune, not return.

[ryanw]

shouldnt the o2 sencors compensate for a rich fuel mixture ?

[ryanw]

Originally Posted by JakeM Retune, not return.

Ha ha i guess i should read better lol

[Trick Tuners]

Originally Posted by ryanw shouldnt the o2 sencors compensate for a rich fuel mixture ?

Only at part throttle, not at WOT.