General Weird Fuel trims! 140%

[tyhoppy]

Ok. I've got a walbro 255, with an aeromotive fpr, set at 38 my Hi and Low Fuel trims are at 140% I have no idea what to do to correct this other than increase fuel pressure. Also I am gettin tons of knock... I'm pretty sure it's phantom knock. not sure if this would make the trims like this, or if I need to increase fuel pressure or what. The ecu is out of a 93 manual, and the injectors are the ones with openings on the bottom like a figure eight, I believe from a 2g. Any help is appreciated!! Thanks. -Tyler

 

[daren_p]

I haven't worked with a 1g & a logger setup but if the trims work the same way they do for a 2g with Dsmlink (not sure why they wouldn't) but a positive trim means the car is running lean, so the ecu has to add fuel, this is why its a positive value. I believe 140% is the max value the ecu can add for a 1g. This probably explains your knock.

If you want to get the proper amount of fuel out of those what you think are 2g injectors, you should probably bump the base fuel pressure up to 43.5 psi. This is set with the vacuum line to the FPR unhooked & plugged.

 

[tyhoppy]

I was confused on the fuel pressure thing. because the 1g is suposed to be set to 38, wouldn't a 450cc injector from a 1g use the same fuel pressure as a 450cc 2g injector in a 1g, because the computer controls fuel?

 

[daren_p]

This I'm not to sure of, need someone with 1g experience to chime in. I do know some 1g guys bump up their fuel pressure to match the 2g 43.5 psi, which is the industry standard test pressure. This way they get the amount of flow the injectors are rated at (well most injectors, some companies cheat & rated at higher base pressure). But according to your trim you are max lean, so I think I'd be trying to bump up my base pressure.

 

[tyhoppy]

Thanks alot. Hopefully someone can chime in and assist us on this.

 

[steve]

This I'm not to sure of, need someone with 1g experience to chime in. I do know some 1g guys bump up their fuel pressure to match the 2g 43.5 psi,

The stock ECU is tuned for 450cc injectors running at 38 psi base fuel pressure. If you change the pressure you are effectively changing the injector size. The fact that they injectors are from a 2G doesn't matter any more than if they were from a RX7.

I get another gauge and reset my base fuel pressure. I'd also make sure that the pressure tracked changes at the reference port so that the difference between the measured pressure and the reference was always equal to the base.

I'd also run a boost leak check to make sure ther wasn't any way for air to bypass whatever air metering device your using. Usually this would cause trims to be > 100% on the low trims and <100% on the high due the the air leaking in under vacuum and out under boost but it's still something to make sure of.

Steve

 

[tyhoppy]

So. i could be sucking air somewhere between my stock MAS and the turbo?

 

[steve]

That's one small possibility.
The more likely one ATM bases on the data you've provided is your actual fuel pressure isn't what you think it is.
How old is your O2 sensor?

Steve

 

[tyhoppy]

not sure how old. but it looks fairly new. and it is a bosch...

 

[steve]

and it is a bosch...

You say that like it's a good thing. The factory part is a NTK sensor.

 

[tyhoppy]

no. i say it like it's a statement. It's hard to show emotion with written text. it was an after thought, so stated at the end...