Extremely lean idle

[parker4]

The cars fuel mods:
Wideband with egt and a boost sensor.
Walbro hp 255 (not rewired).
-8an ss lines from pump to fuel rail.
high flow fuel filter.
aeromotive fpr.
Safc 1 (5 knob).
stock 450cc injectors (850cc sitting in room)
bosch o2 sensor (new)

The turbo is a scm6152e.
2.5 inch exhaust.

The situation:
When I start my car my afr sits around 14.5:1. After about 30 secounds or so the afr's begin to climb steadily untill they reach a mixture of 21:1 which is the highest point that can be read on my wideband. I've completely maxed out my safc to 30+ at 800 and 2400 rpm. My afr will move back down into the 13:1~16:1 area as I fluctuate the rpm's. The car just started so is fairly un-tuned and does not have an eprom ecu. I turned up the fuel pressure from 36psi to about 43psi and noticed that the afr's will stay around a 14:1 mixture a little longer but eventually begin to climb back towards 21:1. I did not do a boost leak test but ran over all the vacume lines and didnt find anything unplugged. My ilde vac is around 21.

I do not plan on making any power right now and that for the turbo's size pushing any amount of boost is just asking for my car to go boom. I do plan on retrofitting the ecu soon, but this is my dd so I need to be able to drive it now.

I dont understand why the car gets so lean at idle. I wouldnt think that at just idle the turbo would be pushing so much more air into the engine that i could'nt tune for it with my safc. So do I keep uping the fuel pressure until I'm a little more incontrol? And if I do that at what point will the injectors begin to fail? Or do I put the 850cc injectors in and hope to be able to tune them with the 5 knob safc?WTF

Thanks in advance for any help.

 

[Spoolin18]

The AFC will not be able 2 handle the 850's. The problem is not the turbo, I hate to ask, but did you go through all the intial setups, such as maf type and so on..

 

[parker4]

the maf is a stock 2g one. I have a gm but no maf translator for now.

Could you explain or give a link explaining what you mean by "intial setups" because I didn't do anything beyond and extra of what needed to be done.

edit... The switches on the back of the safc? Yes they are configured for my car.

 

[Spoolin18]

I'm assuming the afc was bought used..You can go to rre and they show you in better detail than I can, the intial setup.

You have to set several items before you tune with it. I'm not sure on your model, but on the afc 2 you go to etc mode. From there you set the afc up for what type of maf you have, how many cylinders the car is.. I'm not sure your entire problem is the afc though. I would do the intial setup, and go from there.

 

[parker4]

Yah i bought the s-afc used and moved the little blue switches to their correct positions using a website's instructions. Ill recheck the s-afc's settings and re-read what I can do to re-calibrate it for my maf. Maybe theres a shit i need more fluctuation setting but highly doubt it.

The s-afc worked well and was tuneable when I had a 13g and 14b in the car with the same supporting mods.

Any other ideas that I can mess around with, b/c I'm sure this wont be the holy grail to my problems. Would trying to run the 850's even be worth it? I've heard the s-afc wont be able to handle the 850's like you said and thats why they arnt in the car now. As long as its a safe tune I don't really care about its drive ability because ill be doing something about my ecu soon enough. All I've heard is that idle is very very rough when trying to use 850's with an s-afc. I'd rather have a rough idle then a lean car, but if my knowledge is wrong and the whole power band is rough and untuneable they wont be going in.

-Thanks,
Parker

 

[Spoolin18]

Well since you had this afc with your other turbos, then I doubt it is the afc. I would assume it would be rough throughout the entire rpmband, I never used larger than 680"s with the afc. I can't believe no one else is chimming in. I'm a little stumped as to what cause this. It seems odd that the larger turbo would outflow the afc at Idle? As you know there is several risk to running rich, Engine lock is one especialy over time. I seen that done on 850's


Come on guys, lets help this fellow out...

 

[Spoolin18]

An idea Idle is around 14.5+-

A leak after the maf will cause a lean Idle, because air is entering the engine that is not metered with the maf and ECU. I would do a boost leak test first.

 

[Spoolin18]

Sorry, it is 14.7 at idle.

 

[viperlp01]

It might just be the wideband... When you start your car the wideband turns on a self calibrates and then it starts to move. My wideband reads 14.6 then goes to about 16ish ... sometimes it just says lean which is impossible to even run at. Im pretty sure your car wont run if you are leaner than 18.5:1

 

[Spoolin18]

I have seen some run lean at idle, then under boost they would burn 10.5-11, I don't really think it is abnormal for them to run a little lean at idle, I guess maybe your turbo compounded your problem.

Where is your wideband, if its in the downpipe, sometimes a small leak in the exhaust will fool the 02.

I would do a boost leak test, check the piping before the wideband.

 

[Spoolin18]

It might just be the wideband... When you start your car the wideband turns on a self calibrates and then it starts to move. My wideband reads 14.6 then goes to about 16ish ... sometimes it just says lean which is impossible to even run at. Im pretty sure your car wont run if you are leaner than 18.5:1

Good point.

 

[parker4]

The wideband is a zeintronix. My idle egt is around 750 degrees. The o2 bung in the exhaust is a good 4 to 5 feet away from the turbo.

It might just be the wideband... When you start your car the wideband turns on a self calibrates and then it starts to move. My wideband reads 14.6 then goes to about 16ish ... sometimes it just says lean which is impossible to even run at. Im pretty sure your car wont run if you are leaner than 18.5:1

Thats a good idea mabye an exhaust leak. The wideband did work when the 13g and 14b were on. My idles were adjustable from an afr around 10:1~16:1. I did notice that when de-reving the afr's would hit 21:1 right away. I've understood trying to get that to about 19:1 but didnt have anything I could do.

Thanks for the support and help. I'm take a faith drive of about 45 miles if the first few go well. Hopefully I come back with some more info and not a broken car!

 

[parker4]

Well the car drives in the 14:1 digits, so at least I've got that going for me. Actually thinking about it, my down pipe to muffler flange gasket is in need of a replacement, its not horrible but it could be the problem. All was well for a mile.

Its a dsm I'm dealing with so of coarse something breaks... The clutch fork snapped a mile from my house as I was trying to put it in 1st. There was no grinding just a SNAP and the clutch peddle stayed to the floor. Something with the newly installed act 2900. So now I've got a tanny to pull, again!

My dsm tests the limitations to my mind, it sends me on an endurance race of emotions and work always leading from one problem into another. There is no way of counting the amount of troubles I've had to fix with this car. But the smile on my face from whipping around turns, and pulling on $60,000 sport cars make it all worth while. I need a DD

Well off to the old garage.

 

[afsdsm]

An idea Idle is around 14.5+-

A leak after the maf will cause a lean Idle, because air is entering the engine that is not metered with the maf and ECU. I would do a boost leak test first.

a leak after the maf is air that WAS metered, and has leaked off before making it to the engine. That would cause a rich mixture, since the ecu is seeing a larger quanity of air then what the engine is actually getting.

 

[Spoolin18]

You're correct, however a leak after the maf would draw in air, it would suck it in thus it would not be metered. Unlike a boost leak that is forcing out out the leak. I don't believe that was his problem though.