I need some educated opinions on this car. This Evo 9 used to be a Skunk2 shop car. It had 10K miles on it when it was sold to an acquaintence of mine. It has the following mods:

Tanabe 2.75 dp
RRE Stealth Exhaust
RRE Rally Cat AKA test pipe
K&N drop in

This car was running very lean from the get go. I had to set the load cells that the car was hitting to the richest possible level (7.4 target AFR) inorder to get away with 11.3 AFR by redline. Then I had to pull 2 more degrees more than I usually do on a 9 to eliminate knock.

After the tune, I discover that there is a pinhole leak in the test pipe weld. Now I am thinking that this might have caused the lean condition, but why would this cause knock????

This are the options that I have to fix this car:

1. Fix the leak and re-log and see if you can tune the car like a normal Evo 9. I do not know if this will work or not.

2. Change the stock fuel pump. Could a dying fuel pump cause a lean condition like this? This was a shop car and God knows what Skunk did to it.

3. Change the FPR. I read that a bad fuel pressure regulator could cause a lean condition. Is that correct?

Any other areas I should look for?

Thanks

 

I think you should check all 3.

Yes a bad pump could cause this as well. I would also check the wiring.

 

a leak in the testpipe will not make you run lean.

check the maf scaling, something may be messed up there

 

Seems like a pinhole leak is unlikely to cause a lean condition because the exhaust under positive pressure during a WOT run, so no chance to suck in any air to mess up the reading.

Is there room in the fuel hose just before the fuel rail to insert an pressure gauge?

 

Exhaut leak before WBO2 sensor will likely make it lean at idle but less likely to make it lean under load but depending on where the leak is and the flow it still can.

If it idles at 14.7 but leans out on load I would focus on the fuel supply/delivery as the problem, but the leak neeeds to be fixed anyway so nobody gets drain bamage from the fumes.

 

The car was running at 14.7:1 at idle even with the exhaust leak. I am begining to think that it could be the fuel pump/fpr.

 

I had that/this problem on my car. What I found was that one of the injector o-rings was torn, and was starting to fail. It happened rather quickly, eventually after a few days I could smell the faint smell of gas in the engine bay. When under WOT, the gas was leaking past the injector, causing my fuel pressure to drop. It was making the car leaner and leaner under WOT conditions because of the pressure losses.

I would definately check out the fuel system, possibly even giving it a tear out/rebuild session. I used to work at an aftermarket manufacturer, and jeesus, the stuff we used to do to cars, then turn right around and sell them once we were done with them. If I could ever talk to the people who bought them, the first thing I would tell them is to go over all the sytems and verify all is OK.

I wouldn't put it past the fuel system not being up to snuff.

 

Also, make sure that the boost/vacuum hose going to the FPR isn't torn or leaking. If the FPR can't raise the fuel pressure 1:1 with boost, then you will lean out under load, moreso as the load increases.


Eric

 

Check for fuel leaks at the fuel pump connection. Replace the vacuum line going to the FPR with new line that is rated to hold 30 in/Hg or better.

 

Heh in my case today I discovered a bit accidentally that if i run over 21psi of boost the injectors can't keep up. I still have my stock pump so the walbro is going to go in this weekend

 

I fixed the problem on this car. I talked to Mike Kojima and he immediately told me that it was the MAF and he was right. The car had low load numbers, 225-230 @ peak and the IDC was not increasing much despite all the richening up that I did to the map.

I had a spare MAF that I bought from an Evom member. I swapped it in and logged the car and the problem was fixed. Load numbers climbed to 260 and the AFR was rich since the map was rich.

The car belonged to Skunk2 before it was bought by my acquiantence. That shop deals with Hondas with MAPs. They could not figure out that the car was running lean because of a defective MAF. So they placed a piece of tape on a 1/4-1/3 of the filter to try and make it run rich, but it did not work too well. So they sold the car with a bad MAF. One more reason not to buy a shop car.

When I gained control of fuel, I retuned the map and add more timing. The car made more power than before.