6801

just wondering stock fuel pressure is 43 with vacume unpluged. if im a little lean and raise the pressure to 45 or 46 would it richin things up a little or would it cause problems.

RamAir95TA

iTrader: (2)

Raising the fuel pressure will only help in the short-term. Sounds like your fuel pressure is just fine.

ss.slp.ls1

iTrader: (36)

The computer will just compensate by reducing the injector pulse width. You need to ask yourself why you are a running lean, not try to put a band aid on the problem.

6801

thats what i was asuuming.

boosted LT1

iTrader: (3)

YES increasing fuel pressure without changing the tune WILL richen the cars AFR.

It is the same as putting larger injectors into a car.

Changing a 24 injector's fuel pressure from 43 to 46 lbs increases the injectors flow by ~3% verify that at http://www.csgnetwork.com/fiflowcalc.html

43 psi fuel pressure with vacuum line off is not normal pressure. What is your pressure with vacuum line connected?

Good luck

RamAir95TA

iTrader: (2)

Increasing fuel pressure will only change the AFR in the short term. The PCM will just adjust the injector pulsewidth to compensate. It is not a permanent fix.

boosted LT1

iTrader: (3)

You have never tuned a car, if you did you would know better. If you were right how would you make changes that the PCM wouldn't 'compensate' for?

If you don't believe me try it, use datamaster and increase fuel pressure. Increasing the fuel pressure is the same as making the injectors SMALLER in the tune which RICHENS the AFR.

I have been doing this a LONG time. But don't believe me verify and report back.

Good luck

ss.slp.ls1

iTrader: (36)

According to what you say, front o2 sensors are a gimmick because they don't actually monitor the A/F ratio which the PCM interprets and adjusts the fuel trims accordingly...

RamAir95TA

iTrader: (2)

Notice I said short term. I'm not a tuner by any means, but reducing fuel pressure to lean out the motor only helps in the SHORT TERM.

Read:

http://www.ws6.com/mod-7.htm

boosted LT1

iTrader: (3)

Where did you get that? I stated when you change the fuel pressure the AFR will change proportionally with the fuel pressure change.

Do you own Datamaster and Tunercats? If you do take your cable, and change the injector size in your tune by 3% and post the file. Drive it for a week if you like it will react like I posted.

With a Real life test you will prove it to yourself and know how it works instead of believing something that is wrong.

Ask yourself if you are right how do cars run lean as the fuel pressure drops? Why doesn't the PCM 'compensate' to say 8 or 10% of injector size change?

Good luck

RamAir95TA

iTrader: (2)

If lowering the fuel pressure helps so much, then why doesn't everyone use an AFPR?

boosted LT1

iTrader: (3)

I KNOW what you said and what you said is WRONG! Period, verify it like I said there must be one person on here with proper tools!

Change the injector size it will perform exactly like I said.

This is why I ignore most posts on here I correct a small % of what is obviously wrong on here because it just isnt worth my time.

It takes WAY too long because people here hold on to beliefs from what they partly read and didn't understand.

Good luck

RamAir95TA

iTrader: (2)

I've discussed this with several tuners (tuners that actually get paid to tune other people's cars and are quite successful at it) over the years, and they all agree that the following paragraph is true. Tell me why it's wrong...I'm all about learning new things.

After lowering fuel pressure to achieve a better air/fuel ratio, the computer sees this at part throttle and adds injector pulsewidth to compensate. Basically, horsepower fell back off to where I started from. While normal trains of thought tell us that since O2 values are not measured during wide open throttle, that fuel pressure should have a long lasting effect here. Actually, it does not. The computer uses the last known long term fuel trim integer at WOT, which is to add fuel since at part throttle it has adjusted for being too lean.

boosted LT1

iTrader: (3)

OMFG

That is hilarious! He doesn't have the ability to read o2's but you are using what he posted?

At BEST he signs his name with an X and works in spurts and that is not the type expert anyone else will believe...

PERFORM tests like I said there are many errant sites on line VERIFY for yourself then post back!

I am sure you and your buddies can fill the page but instead why not perform a test and LEARN. Your choice been there done that. Been fun but gotta go

Good luck

Puck

iTrader: (17)

The fuel pressure should not be toyed with on a stockish car as a way to tune the car. If you are running a little lean, you need to find out why and check the pump or regulator.

That being said, the PCM can only compensate the AF a certain amount in either way. I want to say single digit percents, but do not remember the exact number.

Adjusting the fuel pressure can have some benefits - a smaller injector with higher fuel pressure maintaining a more normal pulsewidth will have a much better spray pattern then a large injector with low pressure that is still struggling to maintain an excessively short pulsewidth.

In this case though, find out the real problem and leave the fuel pressure alone.

boosted LT1

iTrader: (3)

He originally asked:

I responded


YES...

I never said use the fuel pressure to correct his problem

When you find his fuel pressure with vacuum connected Puck or whomever can direct him to find the pump, filter, line, injector or whatever problem he has.

Good luck