Intake manifold vacuum\fuel pressure problem

[progman]

I bought a Nismo fuel pressure regulator for my ca. I set it at 34 psi at idle. But my car runs very rich. (black smoke and a black coated rear bumper after awhile) So i figured I might have set it wrong.

So I set the fuel pressure to 43 with the vacuum line detached. It seems to run fine but very rich at idle.

The reason I set it at 43 without the vacuum was because I only have 16 psi of vacuum (my friend has 25) at idle.

what should the vacuum be at idle on a stock setup?

I thought if i set my fuel pressure to 34 at 16 psi of vacuum then 0 psi vacuum would only be around 38 psi (which it was). So i set it at 43 with the vacuum line detached so that IF my idle vacuum was 25 then the fuel pressure would be ~34 which would be correct. but...

16 vacuum = 38PSI0 vacuum = 43PSIthen ... 3.4 vacuums = 1 PSI

25 vacuum = 36.2 PSI ???? this doesn't add up. is it not linear?

I noticed a few things:

If I'm not at idle my A/F ratio stays between 11-14:1 (It needs tuned real bad) which seems ok. but at idle it reads ~10:1

My oxygen sensor is hooked up. I haven't checked yet (will do tomorrow) to see if the ECU temp sensor is working (the one that plugs into pin 28 and 30 on the ECU). would this cause it to act like that?

My friend thinks I have a vacuum leak somewhere. But i have no problems boosting. Wouldn't a vacuum leak turn into a boost leak under boost?

What do you guy think is going on? Sound like a vacuum leak?

Why would we fuel pressure be ~34 at idle but only ~38 with out the vacuum line attached? (it should be ~43).

Or the other way around ~43 at 0 psi and ~38 at idle... whats wrong?

I have stock injectors and a ka sohc maf. I have a fmic if that make any difference. I checked all my vacuum lines with the diagram in the stickies.

[float_6969]

Have you searched? This has been covered multiple times. It's also covered in the FSM. No worries, I'll cover it again...

With the car off have a friend turn the ignition to the RUN position but don't start it. Note the fuel pressure. If it's not at 36/37psi, then adjust your FPR up or down accordingly. Have the freind turn the ignition off and then on again, repeat until you hit that range. Don't try to set the fuel pressure with the car running, it's impossible. If you don't have a friend to help, you can also remove the cover on the black plastic fuse/relay cover near the battery. There you should find a green relay labeld Fuel Pump (you'll have to look at the top of the cover to figure out which is which). There are 2 tabs holding it in. You'll need to depress them and then remove the relay. then you will find that there are 4 prongs underneath. 2 close together and 2 farther apart. Make a jumper (a peice of wire with both ends stripped) and place it into the two female prongs that are closest together. Now turn the ignition swith to the run posistion and the fueld pump should run constantly. Adjust the fuel pressure to 36/37psi w/o the car running. Reinstall fuel pump relay, cover, and start car. All should now be OK.

[progman]

Thanks float.

*KISS*

[float_6969]

NP, but lets keep the male on male kissing to a minimum please!

[rico05]

Don't feel bad, Ryan had to hold my hand through the procedure as well. Tricky bugger it is to set!!!

And don't you be kissin Ryan. I'M his stalker

[progman]

Male on Male kissing??

anyways.. So my friend and I set the fuel pressure to ~36 with the pump on. (It was ~43). I didn't notice a difference at all. I still have all the problems.

My friend made the pump turn on with the key an kept doing that until it was set. I think I did it correctly.

My friend was revving the motor and we could hear what sounded like air leaking some where (near the turbo). But we could only hear it while the car was slowly revving or just after letting off the throttle. (This is not the waste gate noise)

This is my boost gauge when you let off the gas:

0 psi drops to 23 psi

we hear the leaking noise

then I have 17 psi

I think something is wrong.

[float_6969]

Male on Male kissing??

Are not not a male? No offense if you're not, it's just that your Screen Name is "Progman" and your profile say's your name is Benjamin.

My friend was revving the motor and we could hear what sounded like air leaking some where (near the turbo). But we could only hear it while the car was slowly revving or just after letting off the throttle. (This is not the waste gate noise)

This is my boost gauge when you let off the gas:

0 psi drops to 23 psi

we hear the leaking noise

then I have 17 psi

I think something is wrong.

Do you mean 0psi drops to 23 in of Hg or cm of Hg?

Regardless, yes, you will have more vaccuum when the motor is reved up and then the throttle is closed. If you're turning the motor at 3K RPM and close the throttle it takes a little bit for the RPMS to drop to idle and during the time the vaccum is going to be high.

The car should be rich at idle. This is normal, although I think 10:1 is a bit rich when the motor is at NOT. Mine is at about 11:1 at idle at NOT. It may get as rich as 10.5:1 when it's cold and I first start it.

What exactly is the problem that you're experienceing, just being rich at idle, or does the car run poorly?

A vac leak on a MAF system will make the car run lean under vaccum and rich under boost....

[progman]

Well, perhaps it's not a leak. but even if im on the highway with 15% throttle It will be about 10:1 when running 3000rpms and more like 11:1 at 4000rpm

If i adjust my safc for 3000rpm then it will run very very lean when im at 3000rpm and not on the highway.

This is also very related. I tried to adjust my car with the safc but 3000rpm in first gear was a different a/f ratio than 3000rpm in second gear.

When tuning should it matter what gear i'm in? because this wouldn't make sense to me.

I have searched on google briefly about tuning cars i saw a few small guides for the safc nothing very good. do you have any resources that you already know of. even if it's a book that would be good.