Base fuel pressure question

I just installed my afpr and set the pressure with the vacuum hose off to 37 psi. Check the WB and my afris at 10.9 and sometimes 11.2 fluctuates. I have a keydriver chip, and he set it up for my 550cc injectors. I try to take fuel out with the Maft pro and it doesn't help. So I'm thinking of other reasons for this maybe because I got my vacuum source for my MAP sensor off the TB? Or because I tap my FPR vacuum hose for my boost gage and my boost controller? I plan on tapping my intake manifold sometime this week or the next for the MAP and boost controller. But at WOT my afr is right where it should be. So if anyone has any input it would be greatly appreciated.
Thanks, Bryan

 

[fastasleep]

I dont have a whole lot to add, except that unless you told Jeff that you had an adjustable regulator, your chip is set up for the factory 37.5psi, so your 550cc injectors (rated at 43.5psi) are probably flowing around 510cc (or so I have read).

How is your boost gauge, mbc, and fpr all able to use the same boost source?

 

see thats what I thought about the fpr and the profec using the same vacuum source and the boost gage tapped into the bc hose. I need to tap the intake manifold before I do anything else. I should have known better /ubbthreads/images/graemlins/banghead.gif. And I'm not sue if I told him but with that sheet he sent me it says 37 psi afpr.

 

yes thats it. set a higher pressure if you have a 255 pump and afpr. Just make sure you tell the guy programming your chip so the extra cc's will be compensated. You'll gonna need if you'll be boosting high on the e3 16g. I've set mine at 45 psi.

 

Quote:
I just installed my afpr and set the pressure with the vacuum hose off to 37 psi. Check the WB and my afris at 10.9 and sometimes 11.2 fluctuates.



Need more details: WHEN is your A/F 10.9:1? At idle? What exactly is your concern? If your O2's aren't cycling at idle, you are too lean at lower airflows evidently. The O2 should cycle around 14.7:1 whenever you are in closed-loop. The fact that the A/F is dead on at WOT would seem to indicate that your fuel pressure and chip are OK, you just need more fuel at idle, if that is how I understand it. /ubbthreads/images/graemlins/dunno.gif

 

Yes my a/f is 10.9:1 at idle, I'm sorry I forgot to mention that. you think I need more fuel at low airflows?

 

No, I'm sorry, I meant you are too RICH if you are getting 10.9:1 at idle. So, the O2 is probably stuck high, and refusing to oscillate. How much vacuum are you pulling at idle?

 

Yea I knew I was rich at idle, I was trying to take fuel out but it didn't move. I'm pulling between 17 and 18 in. Hg.

 

You're going to need to remove a LOT of fuel to get it down from 11:1 to 14.7:1, like 30% or more.

 

[fastasleep]

REVIVED!

What should my fuel pressure be at idle with the vac line hooked up?

 

[stevep]

Depends on what your vacuum is.

Your fuel pressure should be base + manifold.
At idle where you usually have a vacuum in your manifold the fuel pressure will be lower than base. The rough conversion from inches of hg to psi is 0.5x, so 18 in hg would be -9 psi and the fuel pressure should be about 28psi.

Steve

 

[atc250r]

Quote:
What should my fuel pressure be at idle with the vac line hooked up?



You shouldn't check it that way.

John

 

[fastasleep]

I know John, I just wanted another way to verify it was behaving within normal tolerances.

I moved my regulator from sitting right off the fuel rail with an AN fitting to the firewall with SS line (safety reasons), but now the system doesnt stay pressurized after the car turns off. This would indicate a leak, but I swear it's not.

I read something about teflon'ing the vacuum port and teflon'ing the adjustment screw as they can leak boost and not maintain a 1:1 A/F ratio, but Im not sure if that would explain the system's inability to maintain pressure.

 

[Jason G.]

Aeromotive claims there may be a slight air leakage through the adjustment screw, but it's normal. /ubbthreads/images/graemlins/dunno.gif

 

[atc250r]

The system's inability to maintain pressure is due to one of 3 things:

- Leaking Injector(s)

- Leaking Check Valve In Fuel Pump

- Leaking Check Valve In Return Line

I wouldn't worry too much about it if there isn't any driveability issues. Mine has been like that for as long as I can remember.

John