At idle?

Same under load?

I did a quick search and saw something about fuel pressure at idel should be 3 bar but what is 3 bar?

I have a LR FP gauge at the end of the rail I am using to read the pressure and right now at idle its about 28psi.

 

3 bar is about 42-45psi. Hmm, 28psi sounds very low to me.

 

yikes!! I am way under that...........hmmmm

 

OK I found this link from Clarks Garage and it says FP at idle should be 29pis +/- 3psi. I wonder if I need to increase that for the 55# injectors?

http://www.clarks-garage.com/shop-manual/fuel-01.htm

 

I think it's 3 Bar static. (around 43.5 psi). Under boost, you just add the boost pressure... ie, 1 Bar of boost... 4 Bar fuel pressure (58 psi).

At idle, you are under vacuum. Depending on the condition of your engine and lines, you are probably pretty close to where you should be.

 

As long as you don't get 28 underload, you're good.

 

Most aftermarket chips are setup for 3 Bar. If your chips are set up for 55# injectors, no need to adjust FP... ie, 3 Bar static.

 

Oh boy....this thread is going awry quickly.

1. There are 2 commonly used static fuel pressure settings on the 951, 2.5 bar and 3 bar.
2. These settings are defined at atmospheric pressure - which means a 2.5 bar regulator will give you about 36.25 psi at the rail WITH THE VACUUM HOSE REMOVED.
3.WITH VAC SIGNAL INSTALLED AT IDLE, the regulator will restrict the pressure down a corresponding 1:1 ratio with ACTUAL vacuum produced at you idle speed. So if you have a 2.5 regulator and 8.25 psi vacuum, your idle pressure will be 28 psi.
4. At 1 bar boost, your regulator will produce atmospheric pressure (14.7)
PLUS the boostpressure to compensate - total is 14.7 + 14.5
5. The regulator that you choose will be determined 100% by the software - NOTHING ELSE.

 

sheesh...........now Im confused.........I have an AFPR............does this matter?

 

I noticed you have Russell's chips... my understanding is they are mapped for 3 bar fuel pressure, but you can check with him. This would mean that at atmospheric pressure (zero boost, zero vacuum), your fuel pressure gauge should read 43.5 psi.

As suggested, you can unplug the vacuum line to check this.

At idle, the Wokshop Manual says your fuel pressure should be around 2 Bar (29 psi) so maybe you only have a stock FPR (ie 2.5 Bar).

 

What Special Tool is saying is this...

Call up whoever it is that made your chips, ask what fuel pressure to run. Then set it and leave it.

 

Thanks.......I guess that was the meaning of point 5 from ST's post............I'll check with Russell............

 

I have a inline gauge installed and I have mine set at the 42 or 47 I cant remember BUT you check it with the FPR unplugged if I remember right, then plug it back in, so it may read lower after plugged back in, I have a maf and 55 injectors also.