I went to the dyno this past weekend (I am trying to get the guy to send me the graphs right now), I put down more power but my car was pinging above 5K rpms....the reason being, it was crazy lean. If I recall I went over 12:1 A/F around 4K and around 6K I was approching 16:1 when I clutched it. This was with the 3:1 FMU disc, so I put the 4:1 back in and had the same results just a tiny bit richer (but still way lean), these were the only two FMU discs I had with me so I called it a day after I played with my SAFCII, even when I was adding fuel with my AFC it did not do anything to my A/F. So my question is, is my fuel pressure too low? It was at 25psi for my dyno pulls. I am really confused, I was thinking I could get the car tuned on one of these FMUs. The only thing I have changed since my last dyno is fixing two big boost leaks.
My set up is: 370s,walbro,AEM FPR, base FP set at 25psi, A32 MAF and ECU, 3.125 pulley, PF Throttle Body.

 

anyone have any idea if this if fuel pressure related?

 

Certainly more fuel pressure will lower the afr. But lowering the afr may not cure the problem.

I had serious detonation issues above 6000 rpm after installing my 3" pulley, even when running rich. I didn't have any problems before with a 3.25" pulley. Going with a JWT ecu solved that completely, so I'm inclined to think it is a timing issue when you get above 10 psi or so.

 

could be but my A/F is going up to 16:1, I would like to get that solved first. What fuel pressure were you running on each pulley?

 

Oh, that's right, you did say that. My bad.

Do you know what your fuel pressure and boost pressure are when you start to go lean?

 

not exactly sure...If this guy ever sends my my dyno pulls on email I can give you a better idea. Right now I am running 30psi at base (I turned it up 5 psi to be on the safe side)

 

how much boost and what is your maf voltage?

you may be maxing it out

 

3.125 with CAI set up on a V2 blower (I have an electric boost gauge so I am not sure I trust that thing). I am still on the US manifold and stock rev limiter, so that leads me to believe I am not maxing the MAF out especially since it is going so lean at such a low rmp. As soon as I would punch the gas for my sample it would be right at 11.8:1 (which is about what I was shooting for), then it would fall off the chart below 10:1 ~4K (factory fuel dump?) then come back on in a few hundred rpm and go up in a diaginal line until about 16:1.

--I don't know what my MAF voltage was I never really pay attention to that

 

You need a 6:1 disc.....

A 4:1 with 25psi base fuel pressure doesn't even overtake the stock 1:1 FPR until ~11psi.

Adding fuel with the SAFC wasn't working because your injector duty cycle was max'd.

You sure you have 370cc injectors?

 

BTW, you have a N!!!!CE max~!

 

you can see the max's on the safc by pressing down. if its at 100%, then your sol

 

flow tested from rc at an average of 410cc

I used to have a 6:1 laying around, I need to try to find it again...I really need to mark my FMU disc because I do not know what two of them are. How do you measure the FMU discs?

Also if I use the 6:1 should I drop the fuel pressure back to 25psi? (I am going to test all of this on the dyno but I would like to get an idea of what you guys think will work) the car ran better at idle with 25psi as opposed to 30psi.

So how do you measure the FMU discs?

-I doubt I am maxing the injectors...plenty of people have run 370s with the 3.125 pulley

 

yeah I know how to read it, I was just saying thats something that I do not pay attention to (I know I should, but I am just telling the truth)

 

Using a FMU at all means you are maxing the 370cc.

Your lowering fuel pressure and running too small a disc is your problem. Try and run as high as base fuel pressure as you can without cold start issues and a 6:1. If you can't raise fuel pressure above 30psi or so without cold start issues, you should run a Z32 MAF.

 

370cc injectors should support ~280bhp(238whp)@80%DC or ~350bhp(298whp)@100%DC.

 

I made 298.8 on the 4:1 so that is a good calculation

with the 370 comment(I agree with you) basically I saying with the FMU discs available to us then my injectors were not maxed out in that aspect.

**so how do you measure these FMU discs?

 

But what you're missing is that you're basically running on your FPR 1:1 ratio not FMU ratio, since your 25psi base fuel pressure and the 4:1 doesn't overtake until 10-11psi.

 

But that can be corrected with a 6:1, is what you are saying

 

6:1@25psi base fuel pressure should kick in around 6-7psi, which means it flows more then 370cc(280hp/350bhp). At 10psi, you'll see around 72.5psig which means 446cc per injector and good for 340bhp@80%/425bhp@100%.

 

sounds good...I'll try to get the dyno graphs up tomorrow

-does anyone know how to measure the FMU disc to determine what ratio you have?

 

Here's what I found in an old thread...not sure it's 100% though:

4:1 = 1.59"
6:1 = 1.85"
8:1 = 2.22"
10:1 = 2.47"

 

What Ice is saying is exactly right. Your FMU is doing nothing since your base fuel pressure is so low and your disk is so small. Injectors are maxed out, I had the same thing when I dyno tuned. SAFC could not add fuel becasue I was at 100% duty cyle. I had to go with a bigger disk and take fuel away via the SAFC

 

ok here is the dyno graph...you think a 6:1 will fix that? I am looking to get right around 11.8:1



--these are all third gear pulls...I always dyno in 3rd because I have a GXE which has a speed limiter and I cannot get a full pull in 4th.

 

so will a 6:1 with 25psi base fp fix this? Or do you think I should try running around 30psi?

 

Yes, a 6:1 *SHOULD*, however I think you should run stock fuel pressure by using a Z32 MAF. You're exceeding your A32 MAF anyways(290whp).

 

I wish you would have checked you airflow % and voltage while you were on the dyno.

Maybe you could do a a 3rd gear pull for me on the street and find out if you ARE maxing out your A32 maf.

 

I'll get that taken care of as soon as possible I may be going back to the dyno again on Sat. we will see if I have enough time.

 

I have a 6:1 Disc now, I need to turn my fuel pressure back down to 25 psi, I am going back to the dyno on Sat. so I will report back on Mon., I will try to keep an eye on my MAF voltage as well. Thanks for the help so far.

 

Why do you need to turn your fuel pressure back down(30psi->25psi)?

 

Also, you realize you can find a J30(same as Z32) MAF for ~$50, right?

 

jdmmax had this same problem, till he swapped in a z maf..

 

did you have a chance to check the airflow. To see if you are maxed out. im willing to bet you are maxed out. they say they max out at 280whp to 290whp

 

Yeah I checked it, and the AFC said I was only hitting 93%, My car is still not tuned my MAF is cracked and I wasted a lot of money at the dyno. The car is running much better, I got rid of the 3.5-4k bog....my curve is very smooth now, but the car is back to being stupid rich on a 4:1 disc....something is not right.