Leaning out the a/f

dzx · Post by **dzx** » Tue Oct 25, 2005 1:38 am

How big of a diff. will it make when i switch the tubing on the maf from 2.5in to 3in diameter piping? Right now my car is running really rich even with the fuel set back as far as i can get it. It mostly just bogs down at w.o.t. then fights through it.

sammydafish · Post by **sammydafish** » Thu Oct 27, 2005 3:07 pm

how is part throttle driving? I dunno what your mods are, but you might just have a bad O2. My O2 overheats on the highway sometimes and dies, the ECU thinks it's lean all the time so it richens it up as much as it can. The thing actualy runs better it it decides to throw a MIL and run in limp mode.

If you're talking about putting the AFM electronics in a larger tube, then it's simply a matter of increased calibrated area. A 2.5" tube has an area of 4.9" (Pi*r^2), a 3" tube is 7.06" or a 44% increase in area. Now this doesn't directly relate to a 44% increase in flow, but it's close enough to guess.

dzx · Post by **dzx** » Thu Oct 27, 2005 10:53 pm

Interesting, I'm still not sure what problem is. I'm hoping that its just the MAF getting maxed out and sending my 550cc injectors to 100% idc but i'm not sure. I think i'm going to spend this weekend trying to smooth things out in my engine bay.

DeusExMachina · Post by **DeusExMachina** » Mon Oct 31, 2005 3:22 pm

Ever have any luck with this?

My car is now running 9.6 AFR (or richer) under boost, lift throttle, etc.

There's no vac leaks, I had a MAF code and I replaced it with a spare, now I have a TPS code but my TPS has good signal. Its really driving me insane.

dzx · Post by **dzx** » Mon Oct 31, 2005 6:11 pm

I'm still waiting for my piping to arrive.

mhrallyteam · Post by **mhrallyteam** » Tue Nov 01, 2005 6:15 am

I've put a straight thru muffler on mine and noticed a LOT of backfires, mostly at part throttle. I would like to find an efficient way to lean it out just a bit.

But at least too rich ain't too dangerous

dzx · Post by **dzx** » Tue Nov 01, 2005 10:52 pm

Yeh, except you run the risk of fouling the plugs. I know I don't want to pay for another set of NGK Iridium plugs.

It mostly just annoys me. When I was racing that srt 4 a couple days ago, we killed them all the way through second gear. Then hit third gear where it bogged down and they started to catch back up.

BAC5.2 · Post by **BAC5.2** » Tue Nov 01, 2005 10:57 pm

What is the accuracy of your fuel tuning software?

Most reduce the injector pulse by .1 millisecond.

Well, every .1ms increase or decrease is a 50% flow increase or decrease. That's why HUGE injectors suck at idling.

If you flow 300cc's of fuel at 1.5ms, at 1.6ms your flowing 450cc's of fuel. And the change from 1.5ms to 1.6ms is something you need to define.

I don't think an SAFC really allows you to work so finely with how and where the jump in injector pulse width happens, does it?

sammydafish · Post by **sammydafish** » Wed Nov 02, 2005 9:31 pm

for those of you who have backfires and rich running at part throttle, replace your O2. Unless your injector/pressure combo is grossly different from stock the ECU should be able to compensate in closed loop mode and still run you at a nice 14.7 afr. I run about 42psi Fuel pressure on the stock injectors and it works out great under closed loop, but alows for the fueling I need when the boost comes on. So far I've been lucky, it sticks it right about 12:1 at WOT with no piggy backs. Now that it's cooler I'm going to start turnig up the boost though. We'll see what happend then

mhrallyteam · Post by **mhrallyteam** » Thu Nov 03, 2005 1:42 am

My O2 sensor is brand new, i replaced it 4 months ago! I'll try some new plugs, maybe colder range.

By the way, i'm running a 2.0l block with 2.2l injectors and ecu. maybe i'm to rich at idle, since it's 10% fuel scheduling at idle. But it idles fine, well... i just don't know

ej22t · Post by **ej22t** » Fri Nov 04, 2005 8:04 am

I am running the same setting as your turbo.
But my idle is stay above 1000rpm. and I know the car is running too rich too since everytime when I after start the car, I could smell fuel.
I know my coolant temp. sensor has problem (I put an new one on already) but the car could boost over 16psi without any problem.
If there are any way to lower the A/F ratio it will be a great help.

Ben

dzx · Post by **dzx** » Fri Nov 04, 2005 6:01 pm

my car lets out a weak backfire when i get home and shut it off. Makes more of a low whump sound.

dzx · Post by **dzx** » Sat Jan 28, 2006 8:40 am

Alright, I ran the plastic JEC's MAF for a while and I finally changed it back to the original aluminum MAF from my SS. For the first time since I got the car, the CEL is off. I happened to hook up the charcoal canister and other things but the main thing is, my car really did not like the JEC's sensor being on it.

vrg3 · Post by **vrg3** » Sat Jan 28, 2006 2:38 pm

If it was throwing a code 49, you can trick it into thinking the aluminum sensor is on. This could screw up more stuff than it solves, but Doug's doing it. You ground the blue wire going to the MAF sensor.

douglas vincent · Post by **douglas vincent** » Sat Jan 28, 2006 7:10 pm

Yeah, grounding the blue wire does work to get the CEL to turn off.

The Jecs MAF reads 4.6 instead of 5 at the same max airflow (for me).

dzx · Post by **dzx** » Sun Jan 29, 2006 3:16 am

I'm getting rid of the maf completely next week so it doesn't make too big of a difference to me. However i noticed today that the clutch doesn't like to disengage so I had to drive the car home without a clutch. I think the fork is bent or maybe something wrong with the clutch itself. This sucks cause i spent the day snowboarding and I'm barely able to move now, i know tomorrow is going to be worse and i need the car mobile again by monday.

NICO · Post by **NICO** » Thu Feb 09, 2006 11:23 am

my car runs dead on 14.0 afr at 700rpms idle. thats with 550cc sti injectors not tuned. you guys got to start playing with idle speed control sensor and the screew.

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Leaning out the a/f

Leaning out the a/f