Question on a LBZ fuel rail pressure?

[Tarkstoys]

With a stock cp3 and a ad150 lift pump what psi should i be seeing?

[LBZoom]

Personally I don't have a lift pump on my truck...yet... but I would think that the numbers would be somewhere close to what the table shows they should be because of the following...

The truck will regulate pulse and pressure to achieve the desired amount of power so if the lift pump is supplying too much pressure at a particular point then I believe the ECM will command a reduction of pressure from the CP3 or a narrow pulse width to avoid spraying too much fuel.

The lift pump keeps the CP3 from having to work so hard at keeping up with large pulses and to prevent an under pressure condition when you open the pulse up and don't have enough pressure from the CP3 itself. However, i've been able to command a pretty large amount of fuel and still maintain 23-24,000 PSI with just my stock CP3 set up to 180-190mpa, although with a lift pump I probably wouldn't have to set it quite so high to achieve the pressure.

:cheers:

[bballer182]

with a 150 lift pump your should be able to hold 26-27k psi with a 500 -550 hp tune EASILY

[Tarkstoys]

Ok so when loging 5 different runs my frp is 29007 and desired is 26107. Does this seem right?

[bballer182]

Might have too much supply pressure. the lift pump really should put out, or should be regulated to ~15 psi

[Tarkstoys]

The ad150 is not ajustable. Is this bad(for my truck)? With my 530rwhp I burp black smoke at take off but runs with no smoke at WOT all down the track.

[bballer182]

The ad150 is not ajustable. Is this bad(for my truck)? With my 530rwhp I burp black smoke at take off but runs with no smoke at WOT all down the track.

Well depending on how much it does run it can be bad. pretty much all big tunes burp at the line.

[Tarkstoys]

Ok my next question for you is what to do now? I guess run a turn off switch to the AD!

[bballer182]

Well i would say get a fuel pressure gauge and see what it's running.

[Tarkstoys]

On a side note, does this much psi allow me to turn up the pulse for more HP? Would I increase pulse and timing? New to the game.

[bballer182]

If you are holding that much Rail pressure then yeah you have more fuel left to make more power, but you might be out fueling you turbo or tranny.

[Tarkstoys]

Well i would say get a fuel pressure gauge and see what it's running.

Getting one ordered from PPE friday! Man just called Dan! LOL

[Tarkstoys]

I do have a SC4 so that should hold it for now. Turbo is factory though. Last dyno i put down 538 with a bad lift pump. This one seems to works a little better. I would like to try for about 550 plus if possible?

[LBZoom]

Opening the pulse will bring your pressure down some but I don't know about 3,000 psi. I'd say you're about maxed out on the stock turbo. Anytime you increase fuel you have to increase timing and/or boost. Depending on whether or not you've reached your safe limit for timing, you may only be able to add more boost to make up for it. I don't know what the safe limit on timing is for a tune of that caliber perhaps someone else can shine some light on that...

[LBZoom]

Also, you're coming close to maxing out your connecting rods too if I'm not mistaken...

[Tarkstoys]

i'm at 29.8 degrees in timing and 3217mpa (CFP)

[8100 Power]

On a LBZ/LMM. Pistons will go before the rods. I wouldn't worry about those until 650RWHP+.

[JoshH]

Have you modded the regulator or made big changes to table B1015? The actual fuel rail pressure should follow the desired very closely at high load situations. I've seen lift pumps cause problems with rail pressure at idle, but on a big tune at WOT, I have never even heard of someone having this problem. I would look more at tuning before I started messing with the pump.

[LBZoom]

As far as timing goes, I personally used some of nick's advice (vortecfcar) not to use more than 20 degrees below 2800 rpm, even though my truck is stock, and overall I've limited myself to 30 degrees max hopefully just to be safe, and I make up for the rest with added boost. Have you got the problem worked out yet man?

[Tarkstoys]

Went to the track and now getting different reading again??? somethings up, but not sure what! Today not that busy so I'm changing all the fluids in truck and will get some logs done on the street to see whats up. May just be USER ERROR!!!! Got to start some where.