I've got a friend of a friend with a Evo IX GSR he got from Japan with 20k miles. He has the usual exhaust, decat, air filter, walbro mods. His romid is 88570008.

When he brought the car to me for a tune after he installed his AEM wideband. His car idled fine, AFR's right around 14.7. LTFT was like 1 or 2%. We did a quick 3rd gear pull and on boost the car was in the 14's! I was like woah and stopped him at 5k rpm.

I loaded a stock GSR romid in, and again the same thing! 14's on boost. I added A LOT of fuel on boost to the fuel map, like about 2.5 points across the board. We did another pull and it was better and dipping to 11's on boost.

I told him I thought he must have a fueling issue.. because stock injectors, stock maf, stock turbo, etc should never yield 14's on boost. He replaced his fuel pump and it did not fix the issue. My next suggestion was the fuel presssure regulator. He hasn't tried swapping this yet.

Do you guys have any ideas? I'm really stumped on this.

 

I also thought maybe the pump wasn't switching to high mode perhaps. They checked the voltage at the fuel pump housing and said it was 12 high 13 low. So that tells me it was in high mode for sure.

 

What intake is he using? That could be the issue.

 

I have been having similar issues with a car. Where is the WB sensor mounted?

We haven't tried swapping the pump yet but that is coming soon. hopefully the regulator is to blame.

 

Wideband is mounted in downpipe.

Here is what I had to do with his fuel map just to get the car to go rich of stoich on boost:

 

yup, i had to do the same thing. In cells with 7.x i was getting 12.8 afrs. very interested to see if you fix it first.

 

What is interesting as well is I added a ton of fuel after 100 load or so, and if you notice from the log, as the car comes on boost, the afr goes rich, then goes lean as much as 13 high / 14 afr at 3500 rpm 150 load. Then it goes rich again. So I added a ton of fuel, and there was still this lean spot at 3500 rpm.

I thought at first this lean spot was lean spool trimming, but I'm starting to think now that it might be something else, like whatever is causing the problem sort of fluctuating (like a bad regulator). Very strange. I'm leaning towards fuel pressure regulator but I really need your guys help brainstorming other possible ideas.

 

yup SAME thing happened to me. AFRs had a cavern of rich then went lean by redline. It was the weirdest thing ever which is why i suspected a flaky pump. I also thought lean spool but it was disabled so who knows.

I am still going to try the pump first and if not the regulator. Could also be the MAF.

 

why is his load so low?? also why is his IDC so low?

 

The load is 160 at 5000 rpm at 10 psi and 47% IDC. That is actually a high IDC for that state. And also I thought 160 load at 10 psi sounded about right to me. What load would you expect?

 

I am also guessing its the fuel pressure regulator. I had the same problem with a friend's evo6, it had an aftermarket regulator (sard, I think) and had the exact same problem. When switched back to the stock one, the afr became rock solid as it should have been.

Is the car on stock FPR?

 

The car i am working on has stock regulator.

 

sorry did not know of the boost

then its pretty clear u have a fuelling problem - pump, lines, filter or regulator

OR

a WB problem.

 

is there a inline filter on it? check its not blocked.

 

I know its not WB. Car i was working on was showing issues on both the Dyno's innovate and the owners AEM.

Hopefully for me it is just the pump.