Fuel help 42's to small?

[Forcedpower]

I took my new combo to the dyno over the weekend and things didn't go as I hoped. Its a 8.5 to 1 331/AFR 205/ Victor 5.0 and a small s-trim. I have the full Aeromotive fuel system 42lb injectors and a prom-m 83mm mass air.

I could only get 441/433 safely out of it and this is pushing it. The air/fuel was great until about 5200 then it went from 12 to over 14 at 6000. My timing was only 14° with 1/2° on the btm. At first fuel pressure was 40psi so I turned it up to 42 and a/f didn't change much.

Whats going on? Are the 42's just to small or do I have another problem else where? Will try to get the chart scanned in and posted. Thanks for any help.

[itlkick]

The injectors are not too small. What engine managment do you use? Do you have a chip or some other way of modifying your computer?

<edit> re-read your post and saw you have a pro-m meter. Can/do you monitor MAF voltage?

It sound to me like you are maxing your Mass Air Flow (MAF) voltage. Once it reads 5 volts it is "game over man".

[fanglemeister]

A meter calibrated for the 42s shouldn't hit the 4.99v ceiling until > 680hp or 1080cfm, although the max MAF voltage programmed into the oem processor is only 4.78v which is just a hair over 600 hp on that meter, which I suppose if you deduct 15% driveline loss would be a few ticks over 500hp, still more than he hit.

Assuming you are using the aeromotive fuel rails, not Fox rails?

Did you check for any air leaks upstream from the meter that would let in unmetered air? (cracked blower inlet pipe, etc.)

What size and type air filter is on it? If K&N, try cleaning off the MAF sensor with some brake cleaner or some other non-residue spray, a fouled sensor will run lean.

[Forcedpower]

I have the fuel rails that came with the aeromotive kit. I have the fuel line running in the back and out the front of the rails. Not between 6 and 7. No leaks that I can find looked at everything pretty good. The filter is the stock one that cam with the 83mm Looks like a K&N without the oil. Don't have anyway to see mass air voltage the car has all stock electronics.

[itlkick]

Do you have a fuel pressure gauge you can watch when you are making the runs? Does the pressure rise with boost? Does it ever fall off (when it goes lean)?

[Forcedpower]

The dyno I went to wouldn't let you stand close enough to the car to see any of the gauges and the guy doing it wasn't looking. When I drive the car down the road the fuel pressure goes up a couple psi and never drops. I changed the fuel pressure from 40 to 42 and a/f didn't change. Wish I had moved fuel up a lot more but didn't want to keep pushing it.

[itlkick]

What I have seen cause a car to go terribly lean is either a MAF maxing out on voltage or a fuel pump / system that can't keep up. I don't know if either is the case but that is what I have seen.

Good luck!

[Forcedpower]

And both of those things should be good to go. The aeromovie kit and pump has 1900 miles on it. The pump should be able to handle 500rwhp don't you think? Any way to check the mass air without fancy stuff? Thanks for the help guys asked on corral and no one even responed.

[regattacoupe]

Well the only way to be sure is to hook a voltmeter up to the MAF and see what the voltage is when it goes lean. I forget what the plugs on the MAF you use but i think it's the ones on each end of the plug. Whats your A/F in the 3000-4000 range?

[RdRunnr]

When I ran the aeromotive pump, that was my problem. The pump simply could not sustain enough pressure under boost. This is why my car was always lean and blowing hg's with 50# injectors. Switching pumps fixed my problem. I heav heardds lots of similar situations with aeromotives. I do not think they can support 500 rwhp personally, I know others think they can. My experience was mine could not.

[Forcedpower]

Here is my dyno run sorry about the quality but my scanner isn't the best. The red line is 12.8.


Rdrunnr so you think my fuel pump sucks? Me to if it won't handle 500rwhp. What pump did you go to? Is it street friendly?

[RdRunnr]

I went to more of a race car setup (weldon 2025), but for a good street setup I am a big fan of the dual walbro inline setup. A lot of guys here run them so they can share their experiences with you as well as pics of their setups.

[87gtNOS]

you just need more fuel pressure, did you up it to 50 psi and run it? do that, and get the timing right first, then pull a couple pounds of FP per run.

[87gtNOS]

I run a Gss340 pump only! You just need fuel pressure, IMHO!

[MikeyMustang]

I to run only the Gss340 and made 460rwhp with 38#injectors with stock fox rails....i vote for a bad MAF or Bad pump also.....if you have a chip/tweecer/eectuner make sure they change the max maf volts to 4.99


Mike

I run a Gss340 pump only! You just need fuel pressure, IMHO!