Weird car (A/F ratio) question

[Jeff V.]

Ok. WTF is up with my car.

It runs super rich at cold start, but at hot start, it wants to run so lean it almost dies. I've got a MAFT, 3.75" screened GM MAF (early Z06 MAF) and Emanage blue. WTF do I do to compensate for this?

[Jeremy C]

Just a thought, but does the e-man have a cold-start enrichment setting? Maybe it's a bit too high.

[Jeff V.]

MAFT has it.

Think about it....colder temps, less atomization....should be lean. Hotter temps, better vapor, should be running closer to spec.

Instead it's the opposite. WTF.

Should you be on a CoH taskforce or something?

[Monochrome]

Do you still have the FPR sollinoid hooked up?

[DCIV]

recheck your maft settings for the gm mas.


Coop

[Jeff V.]

Do you still have the FPR sollinoid hooked up?

I unhooked that a while ago.

recheck your maft settings for the gm mas.

Wouldn't do me much good. I'm running it in a blow-thru configuration. Even TurboBob said the settings are only valid for draw-thru. I've got the knobs turned somewhere on the DSM side of the setting chart. That was the only way I could get it to idle at all.

If I had temperature based (intake air and coolant) feedback I could probably tune this out. But I'd need a standalone or Emanage Ultimate for that.

[DCIV]

[quote=""Gatecrasher""]
Wouldn't do me much good. I'm running it in a blow-thru configuration. Even TurboBob said the settings are only valid for draw-thru. I've got the knobs turned somewhere on the DSM side of the setting chart. That was the only way I could get it to idle at all.

[/quote]

if I understand you correctly then you are telling me that messing the knobs do make a diff, even though turbobob said they arnt. If you had to change them to get the car to idle then they do change stuff. I wouldnt know what you would change it to...but it seems like it would make a diff. Also do you have your cats in?


Coop

[Jeff V.]

Oh no, they do make a difference. I'm just saying that the actual settings and what they mean are gibberish when compared to the configuration chart in the users manual.

I tried to get the MAFT to a sort of baseline zeroed out state, and then tune everything from the Emanage. Working with the laptop while driving is a hell of a lot better than pulling over every few hundred yards, popping the hood, and twisting knobs on the MAFT

I think what I really need to do is put the 360cc injectors back in, and try to get the car to run more like a stock one. Try to get it to a known-good state. Then I can go back to the 550s and start aiming for more boost.

We'll see. I'm gonna go try a few things today.

[vr4]

cold starts are supposed to be rich because the fuel doesnt flash off as readily so you need more of it.

[Jeff V.]

Right. I get that, though 10.x:1 seems a bit too rich. I'm more concerned with the super lean 17+ hot restarts. The car barely wants to run and usually will die if I don't hold the throttle open for a minute or two until it comes out of closed loop.

Something else I've noticed. Hot or cold, it'll start and try to run at 500-600 rpm. On a cold start, it should start and run at 1200 or better to get the engine up to temp.

Once the engine is at temp and has been driven for a bit, it idles at a near perfect 750 rpm and 14.5-15.5 afr.


Cats are all gone, btw.

[vr4]

[quote=""Gatecrasher""]Right. I get that, though 10.x:1 seems a bit too rich. I'm more concerned with the super lean 17+ hot restarts. The car barely wants to run and usually will die if I don't hold the throttle open for a minute or two until it comes out of closed loop.

Something else I've noticed. Hot or cold, it'll start and try to run at 500-600 rpm. On a cold start, it should start and run at 1200 or better to get the engine up to temp.

Once the engine is at temp and has been driven for a bit, it idles at a near perfect 750 rpm and 14.5-15.5 afr.


Cats are all gone, btw.[/quote]



my 91 did that at hot starts but i didnt have a WB to see what AF was. i never did put the FPR solenoid back in to see if it helped.

[Monochrome]

[quote=""vr4""]cold starts are supposed to be rich because the fuel doesnt flash off as readily so you need more of it.[/quote]

I'd assume the ECU doesn't use the O2 sensors to correct the a/f ratio until they are warmed up and just uses a preset program. If that were the case, then the mitsu engineers probably made it a little richer than need be sos to help atomization.

This would only get amplified when larger injectors are installed. If such were the case, I wonder how difficult it would be to code a startup map which would only be effective when coolant temps are below a certain degree. Definitely something to throw out there to the designers of all the piggybacks.

As for Gates startup issues. You could try hooking the FPR sollinoid back up or get used to holding the throttle open while you start the car.

[Jeff V.]

It's embarrassing when you get in the car (like I just did at the gas station) and the car is sitting there revving up and down, even though you're trying to hold it at a steady RPM.

"Why is that asshole in the sports car sitting there gunning his engine at a gas pump?"

[JagdStealth]

[quote=""Monochrome""]I'd assume the ECU doesn't use the O2 sensors to correct the a/f ratio until they are warmed up and just uses a preset program. [/quote]

That's how it worked on a couple of Nissan's I worked on with big injectors and emangage, although the problems don't sound as bad as yours. It was very rich on cold starts (not a big deal unless you like to sit in your garage) and lean on hot starts, but it was never lean enough to cause the car to stall, just idle a bit rough.

Talking to greddy Japan they said that was normal...at least with the RB25s I was working with.

[Hans_GZP]

My 98 does the same thing with the aem ems. You have to rev it a few times on hot starts to keep it running. It's not just you with that problem haha. I just deal with it. But yea, mine will idle at 700 rpms no matter if it's cold or hot. Cold starts it idles a little rich, but not by much and when it's warm it likes to idle lean until you drive it a bit... then it will idle only slightly lean.