hey guys, I have a new adjustable fuel pressure regulator from holley and a fuel pressure gauge inside of the trans am. Was wondering what a good roundabout fuel pressure would be on a 350 with stock injectors, free flowing exhaust system, ram air, cam and upgraded chip? thanks

 

Try 47 as a starting point, w/o vacuum that is.

 

sorry I am still young and ask stupid questions...what do you mean by w/o vacuum? thanks

 

He means measuring the fuel press with the fuel press regulator vacuum hose disconnected (and plugged). Disconnecting the vacuum line makes fuel press rise by 4 to 6 psi. With the vacuum line connected, it should be close to 43 psi.

 

thanks that helps out alot, I was pretty sure the regulator was messed up as it would be around 30 psi when first started and after a couple hours gradually move up to 60! then it would smell way to rich and smoke and all, thanks!

 

43.5 line off is the best setting for stock.

For temp fixes or if you are into your own prom tuning, experimenting with pressure can be of some benfit.

later
Jeremy

 

Mine TPI smells gas and when i last checked the PSI was fairly low. But shouldnt it smell more and run richer if i increse the pressure?


thanks,

Sam

 

If you increase fuel press, it will run richer in open loop. Once in closed loop, the ECM will keep the mixture at 14.7 to 1 provided the O2 sensor is working properly and the BLMs have not reached their limit.

 

alright, well I am looking at getting new injectors anyways as well to accomodate for the custom chip that Im putting on the t/a. I have heard ford rates different fuel flow settings? if I put 24lb injectors on with a tuned chip then what should my fuel pressure be at? probably lower than the 43 without the line because stock was 22lb and these are 24's? thanks guys!

 

So whats the point of an AFPR?

 

good point..... that doesnt make sense to me either

hey i know this is off topic, but i just checked out the pictures of IROCThe5.7L's camaro and theres a pic of it in a gas tank, the prices are like 1.50 a gallon lmfao. how long ago was taht????

 

anybody have an answer to my question? haha

 

With a custom chip, you can lie to the ECM telling it the injs are smaller or larger than their actual size.

If you want to run lower-than-stock fuel press, you tell the ecm that the injs are smaller than they really are. The ecm will hold them open longer so you wind up with the right amount of fuel.

If you want to run higher-then-stock fuel press, you do the opposite.
(On my chip I have the fuel inj size set to 26.5 lbs even though I actually have 24 lb inj installed)

The correct inj size on the chip is found by trial and error. You set the inj size, drive the car, note where the BLMs are at, modify the fuel inj size (on the chip), drive the car, note the BLMs, make another inj size adj, drive the car, and so on. If you adjust the fuel press a significant amount, you'll need to start the process all over again.

Some people (myself included) like to run their fuel press a little higher than stock to improve fuel atomization. There are limits however. Running fuel press over 50 psi (on a tpi car) is really hard on the fuel pump.

Replacing the 22lb injs with 24 lb injs will make the eng recieve more fuel than the ecm planned for. By adjusting the fuel press down you can make the eng recieve the correct amount of fuel, but lowering fuel press will effect the fuel atomization. That's why you need a custom chip when installing larger injs.

The BLMs are commonly misunderstood. Here's a link to a post I responded to that explains it a little better and gives some additional info on ECM tuning theory.
https://www.thirdgen.org/forums/diy-...now-werid.html

The purpose of the AFPR is just to give you another **** to turn for tuning.