running rich at idle

[greenmeanie99]

Im down to fine tuning now my cars idle is rough. I have the idle FP set at -50% and the car is throwing 9 afrs so I cant set the FP any lower. I have 450's and a walbro 255lph pump and a 1:1 fpr on the rail. Any suggestions how to lower the fp.

 

[Slo2gen]

How big is your fuel return line??

 

[BigRand]

so are you now not running that sfmu that is on your modlist. Because that is the only way to get it to run with that setup I believe.

 

[greenmeanie99]

its 1/4'' Advance auto rubber return.

And yes there is an SFMU

 

[VelocitàPaola]

You have a 1:1 on the rail PLUS an S-FMU? I think that's your problem right there. The S-AFC, apparently, will only let you remove so much fuel electronically (PWM), so now you need to start removing fuel mechanically. The 1:1 (I'm assuming it's from a 4G63 if it's on your rail) was probably designed with a static idle fuel pressure in mind (about ~50psi or so). The S-FMU on the other hand will let you adjust the idle fuel pressure lower than that, to decrease fuel, but it can only lower idle fuel pressure as low as the 1:1 is set for.

I say remove the 1:1 and replace it with a disabled '95 FPR, or replace the whole rail with a 96+ unit. You don't need both the 1:1 FPR AND the S-FMU. The only thing that'll suck is that you'll need to re-tune everything since now all your settings in boost will be off. You might even need to jump to a higher disk size inside the S-FMU to compensate. Good luck!

 

[greenmeanie99]

Reccomendations on which disc to use?

Also stupid question how does one tune with an SFMU changing the disc? I already have the smaller black spring in right now which is what I was told to put in.

 

[VelocitàPaola]

I recommend you read this document for the proper usage of the springs, discs, and rings...
http://www.vortechsuperchargers.com/pdf/manuals/superfmuim.pdf

All the information is in there.

Furthermore, here's a little snippet of information as how to tune your S-FMU unit. By adjusting these parameters, you should be able to attain a near stoichiometric AFR in vacuum and in boost.

1.) The main adjusting screw sets the basic static fuel pressure level of the unit. By adjusting the main screw any initial pressure can be set.
2.) The calibration ring and disc are used to set the slope of the fuel pressure increase with increasing boost pressure. Four different diameter rings and discs are included with the SFMU.
3.) The vacuum screw acts like a vacuum regulator. If it is set to give, for example, 5 in hg gauge, the upper chamber of the SFMU will only see 5 in hg even though the engine manifold pressure may drop to 18 in hg at idle. The result of this is the fuel pressure remains constant from idle vacuum up to 5 in hg then the pressure will start to increase.
4.) The optional bleed screw does two things. First, it will lower the slope of the curve set by the calibration ring. So, it can be used to "fine tune" the pressure vs. boost curve. Second, it acts as a damper to "soften" the transitions in the curve.
5.) The boost screw acts in a similar manner as the vacuum screw in that it performs like a pressure regulator. It can be set to limit the maximum fuel pressure. If the screw is set all the way in it will not regulate and the curve will continue to rise as boost increases. If the screw is set to relieve at, say, 10 psig then once that manifold pressure is reached any manifold pressure above that will not increase the fuel pressure.

 

[greenmeanie99]

Well this explains a lot.
I know there is only a screw in the bleed port and not in the other two. I wonder if that has anything to do with how it runs. Ill have to read that and check to see what disc I have.

Also Paul replacing my FPR with a disabled 95 were you referring to a NT or a 4g63?

 

[VelocitàPaola]

Also Paul replacing my FPR with a disabled 95 were you referring to a NT or a 4g63?

A disabled FPR from an '95 N/T.

http://www.2gnt.com/www/corbin/fpr.html

I only say what I did because if you simply remove the FPR you have on there now you'll have a gaping hole at one end of the fuel rail. If you can find a suitable plug that can handle the pressure, that might work too. Or you could possibly use the information in the link above to disable the FPR you have.

 

[greenmeanie99]

Okay so I need to get that new FPR and figure out which disc I have for the boost I want to run I think the 2.72'' diameter looks like the best being I want to run 15psi. As far as setting the Idle FPR I need to get a screw for my boost port and the other port I forget which one it is. Now what do I adjust to lower the fpr to lean it out more.

 

[VelocitàPaola]

Do you mean to lower the idle fuel pressure? That should be the top screw that sets the internal spring pressure.

 

[greenmeanie99]

bleh. yea I mean Idle fuel pressure. Shit I have my SFMU turned upside down so it would fit better now I have to rip it off again. So I should adjust the screw on top, should I mess with the bleed port or the other ports?

 

[greenmeanie99]

Okay so I got a lot of bugs figured out. On my vacuum port on the manifold there was a huge vacuum leak so the BOV never opened. I got a free crushed 1g BOV and found that out. So I put the HKS back on and it sounds awesom. The car idles better and in general runs much better. Now I got to put on my FPR block off on my fuel rail and wire up the SAFC 2 and crank my idle pressure down with the SFMU and were set. 5lbs of boost feels pretty strong with my turbo I can't wait to crank it up.

 

[Slo2gen]

Glad you got it figured out.

 

[VelocitàPaola]

Sounds good, let us know how it goes.