9000th01ss

iTrader: (10)

I have a Racetronics pump and wiring kit in my car.
The engine is stock.
It gets from 64 to 61 psi at the rail at idle.
It also seems to run rich, the LTFT's never go positive.
They average 0 to -14 and the STFT's I've seen at +5 to -43
At what psi increase do you need to adjust the tune?

otherwhitemeat

iTrader: (3)

Any change in fuel pressure can make a massive change it tune.....in other words put it back to where it was.....one of the only reasons to change fuel pressure is to compensate for injector cycle duty and from the sounds of it you are not able to change your own tune so make sure it is at the stock setting till someone can tune it for you......and that would explain your rich condition too...

9000th01ss

iTrader: (10)

I can tune it, I've had HPTuners since 2004.
See heres the problem, I've asked this question several times.
I got the car as a roller and it had the pump. I said I was going to take it out and Racetronics got on here and said thats a dumb idea, it'll work fine with a stock engine and stock tune.
There is no adjusting it, it's meant to replace the stock fuel pump and thats it, no other regulator required. According to racetronics no tuning required. The benefit is that it gets increased voltage with the wiring harness and it can be hooked up to a MSD box to increase the voltage to increase pump output for nitrous use.
According to other people here it's like one third says tune and two thirds says not.
I've been posting the question asking why my LTFT's are never positive and so far every reply I get is the opposite of the other so I have no idea what to do.
If tuning is the answer do I tune IFR? or VE and MAF? or all or neither.

I've spent literally all day searching this and can't find anything, one site says do this and the other says don't, etc.

It seems like something that would be common knowledge yet I can't find a straight answer.

I can't back down on fuel pressure so what do I do with the tune?

9000th01ss

iTrader: (10)

I have been helped by one guy in the PCM forum and he said make the numbers bigger in the IFR table. He gave me specific numbers. It seems like that would make it more rich. Been waiting for him to get back to me on that. I haven't had a chance to put it in a tune yet.
To make it lean with higher FP do I make the IFR numbers higher or lower?

otherwhitemeat

iTrader: (3)

wow..that sux. I'm used to tuning on a F.A.S.T. unit.....so not sure which way the #'s should go... anyway your LTFT ideally should be close to zero...that means your ECU isn't seeing a reason to add fuel all the time.....and your STFT is probably ok adding or pulling 5-20%.....which it might be doing now at idle or WOT. Do know that some ECU will relearn the LTFT and put your car in a different part of the map.....may have to disconnect power to reset???? not sure??? so how much of a % is your LTFT pulling? and what about the short term fuel trim "STFT", what is it doing?

MeentSS02

iTrader: (11)

Welp...here's the problem. The PCM has no way of monitoring or knowing what your fuel pressure is. You are above the base 58 psi operating pressure, and are seeing the reasonable effects of that.

Adjusting your IFR table is the correct way to go here...you just need to make sure it shows the right flow rate based on 61-64 psi (you'll have to pick a value in there) instead of the stock 58 psi.

Racetronix, in this case, is wrong...any difference in fuel pressure from stock can't be monitored, and will cause you to run rich. It's just how the system works...and Racetronix pumps installed with the stock, in-tank regulator are known to cause a pressure increase at the rails.

9000th01ss

iTrader: (10)

in my first post

9000th01ss

iTrader: (10)

From HPTuners.
From here

I guess it's time to shut the computer off and consider the internet and forums useless. What am I supposed to do with all this conflicting info?

odd boy

Cool down boss,

In theory, when the pressure increases the flow rate of an injector will increase too. Therefore, it should be tuned. Let's have a simple i.e:

42 lb/hr Injector rated at 43.5 psi gives 48.49 lb/hr at the rail pressure of 58 psi,

If we increase the pressure to 60psi the injector will give 49.33lb/hr,

If we keep increasing the pressure to 70 psi the injector will give 53.27 lb/hr.

So in conclusion : tune makes things work right, but it won't be that necessary for very very minor change. Similarly, minor pressure change won't make big big change in L/STFT.

I think ur problem is not with the pressure the change in pressure is minor, the problem could be something else like O2 sensor needs to be replaced,...etc

MeentSS02

iTrader: (11)

The above is correct, but I'm not sure what constitutes a minor pressure change versus a major one. Getting the tune back in line through the IFR table is a start, but as mentioned, it could be caused by other factors as well. Start with adjusting the IFR table, and see where that leaves you.

9000th01ss

iTrader: (10)

So you're saying adjust the IFR table for the fuel pressure I have now. If that puts things in line I'm ok, if not then look into component problems? (sensors, etc)
I just don't want to cover up a failing maf or O2 by trying to tune it.

odd boy

9000th01ss,

I did quick calc for you. When u look at it u will find that the difference is around 10%, which isn't a minor change. I think u can go with the tune part. I am really keen to see ur result.

9000th01ss

iTrader: (10)

I appreciate your efforts.
There seems to be a problem with the old numbers, I guess you added 10% to what you have listed as old numbers, but I don't know where you got those old numbers from, they are not mine.

These are my numbers 28.70851 28.89453 29.08055 29.26656 29.45258 29.57659 29.76260 29.94862 30.13464 30.25865 30.44466 30.63068 30.81670 30.94071 31.12672 31.31274 31.43675

odd boy

I got them from a Camaro 99' "stock car", I didn't add 10%, I calculated the flow rate of stock injectors but with a real pressure equal to 64 psig. I revised it for you and the diff came down!!!!!!

9000th01ss

iTrader: (10)

Well Thanks, I'll give it a shot.

I'm really leaning towards a component failure at this point. (or starting to fail)
I have the same problem posted on HPTuners site and it was pointed out that there is no reason (tune wise or FP wise) that my stft's dipped to -43 for a few seconds during one run I was logging.
This guy on HPTuners site could probably tell me where to look, but he just can't type more than two sentences at a time so theres that. He said it might be an O2 going or something else.

Old Geezer

iTrader: (3)

Do we know for sure, that the pressure gauge is correct? [If not, then just maybe there is some other problem??]
I test the small, rail mtd gauges against the master gauge on my inj bench.. Some are as much as 7psi off. Recently, i've tested only 2, that were within 1 psi...

9000th01ss

iTrader: (10)

I am an HVAC/R tech. A gauge set for testing freon plugs right into the fuel rail, but instead of contaminating my whole gauge set I've taken a 1/8 npt female to 1/4 flare adapter and used it on a spare gauge. I have literally 15+ gauges for measuring not only gas but liquid as well.

And when I plug my FP tester into my other car with the stock pump it reads dead on 58 psi.
I've even tee'd several gauges together to get a comparison and they are all close. They also have a zero adjustment to bring them back to 0.

odd boy

Just to prove that the problem is not with pump/injectors, run the car on open loop and see what BEN's you will get. If they are okay, that means the tune should be okay too in the CL.

9000th01ss

iTrader: (10)

Well from what I gather the fuel trims swinging from 0 to-14 is just the VCM doing it's job (despite the several, possibly hundred of write ups I've read that say they should swing ideally +/-4)

I'm starting to think there is a problem other than FP, I get occasional dips in the stft down to -43 and it's not DFCO, the pro on hpt's board just says that could be a problem elsewhere *i'm just not going to tell you why i think that or where to start looking or anything*
I guess my post count on that forum is too low or something.

What does BEN stand for? I looked on here, google, hpt acronyms list....

odd boy

This is what we use in efilive which is the actual AFR/commanded AFR, so it is the correction factor. hp tuners call it AFR error (table no 7).