Fuel Pressure.

[06bowtie_guy]

Just looking for some info on this. Let's say I bump it up some. How does the engine allow more pressure? Does the injector just not open as early causing more pressure to build??

Thanks.

[Ritch]

I have an 99 so not sure if its the same. The fuel pressure regulator is entirely manual. Pressure does change but only in relation to eng vac. The regulator returns excess fuel to the tank while maintaining constant on the rails. I think mine runs about 52lbs. If you did increase pressure the injectors won't do anything different, but more fuel would pass for the given amount of time.

[GMPX]

The 'engine' doesn't allow more pressure.
Imagine the tap in your kitchen is an injector, when you open the tap water comes out because of the pressure, by 'increasing' the pressure of the water you will get more coming out when the tap is open the same amount.
When people complain about lack of fuel pressure, in the above scenario it would be like having weak water pressure and no matter how far you open the tap the amount of water is still only a trickle.

Cheers,
Ross

[IdahoRob]

So on the fuel pressure tables, is there anyway to command the CP3 to increase pressure with EFI. PPE dmaximizer raises pump pressure by fooling the voltages(IIRC). People can do it by cutting voltage to the pump manually.

Maybe we can with EFI. It sure helps with power, in my testing, at the track.

[GMPX]

Don't the normal fuel pressure tables allow you to do this anyway? B1001 etc

Cheers,
Ross

[JoshH]

I have not been able to get my desired rail pressure or actual rail pressure to log over 26,000. I don't know if it is a PID problem or if it is actually not going as high as my tune is calling for. It's almost like there is a maximum rail pressure table somewhere that we don't have access to.

[GMPX]

PID is the same one as the previous model Dmax's used, so there should be no issues there, the PID will allow the reported values to go above that if it actually can. If it is not a mechanical limitation it looks like the LBZ ECM strikes again :Eyecrazy:

Cheers,
Ross

[JoshH]

"I fear you are underestimating the sneakiness, sir."

[IdahoRob]

My rail pressure reads over 26k. I've seen it in logs at 27k+ on actual rail pressure on pedal let off. Now desired rail pressure, I've not played with yet, stays at 26k, but I'll try to test this with the B1001, etc.

[JoshH]

Exactly Rob. I should have been more clear. I have seen spikes in the low 27s, but I have tunes that call for rail pressures in the neighborhood of 29,000 and it never even attempts to get there. Desired rail pressure tops out at something like 26,107 PSI.

[Rooky]

Same here

[Racehemi]

PID is the same one as the previous model Dmax's used, so there should be no issues there, the PID will allow the reported values to go above that if it actually can. If it is not a mechanical limitation it looks like the LBZ ECM strikes again :Eyecrazy:

Cheers,
Ross
Desired fuel rail pressure or GM.FRPDES PID is the same as the previous Dmax's however, the actual fuel rail pressure PID appears to have changed to SAE.FRP_C which makes it hard to link the actual FRP to the tuning side. I'm thinking about creating a calculated PID to convert kPa to MPa. Any other ideas?