Running lean under acceleration... ???

I have been dealing with this problem for quite awhile now. I actually have made about 4 new maps since I noticed the problem and I still have yet to figure it out. I am really curious to why it is happening as I have the car partially tuned.

Notice the picture below in the shaded area. The GREEN line is my throttle position and the bottom two lines are my AFR readings (ORANGE is the set point and BLUE is actual). Notice how when I start the throttle that the car is running super lean and then it finally richens up. I have tried a number of things including adding more fuel and adding more acceleration enrichment. Still nothing.

id help you out but all i have ever worked with and know fairly well is carbeurators sorry man.

That would sure make my life a heck of alot easier.

haha it does but it always makes life a little bit more expensive in the long run with all those tanks of gas.

ive noticed that a leaner acceleration is not really that bad. at one time, i had mine tuned for highway travel and it would idle at about14.3 a/f, then as i accelerated it would sometimes spike as high as 18 a/f, but it didn't seem to have any real adverse affects on anything except my conscience... i think alittle lean under part throttle is probably okay, just as long as it's not going lean under boosted acceleration ya know.

That is what I was kind of thinking, but I put a post up on the Autronic forums to see if someone can help out. There is an acceleration enrichment table and I am hoping someone can help. I have tried a few different values in the table and there is no difference.

actual a/f ratio while meerly just cruising around isn't important unless you are having issues. heating up, fowling plugs, stumbling and coughing all would lead me to beleive that the cruise tune is off, but beings that your setup works and isn't giving you fitts, then i would think its just one of the non-dyer issues.

My car runs in openloop 24/7. I actually have to turn the closedloop/open highway on.

oh fuck now you lost me completely haha

that graph is really annoying to read... i don't know enough bout ur setup either. nor do i know alot bout subaru tuning and comman / rare problems that would cause this kind of leaning out. i wish i did tho. so i'm just gonna blurt a few things out...

not sure what size fuel injectors your're running but it looks like when u hammer the throttle it leans out then cures itself after... how's the condition of ur fuel system in general? maybe for that one split second a weak injector isn't spraying enough fuel? or the the fuel pump? prob a long shot but you never know?

you idle smooth still? i had problems with my honda bouncing alot and it turned out to be the throttle position sensor. it would bounce a lil bit in the air to fuel read out under acceleration from what we were telling it too. lean for a sec then correct itself.

just looks like to me like something is lagging somewhere? i don't know enough with how the different sensors for fuel and air interact on subaru's either.

so really i'm prob not being a help at all haha

Hey Mike. For one..... it's hard to read that graph. Not high enough resolution being a snap shot to really see it. But it looks like you're throttle enrichment is working.... You get a good spike there after TP tip in. I would say almost too much.
Are you running any HO2 sensors? or just your wide band? Even a wide band doesn't respond immediately. There is a little bit of lag there... although less then a second... still a lag.
I'm not understanding your open/closed loop problem. Do you maybe have it set for manual operation? Is there a link with that for the warm up enrichment?

And finally..... tuning by A/F ratio is not ideal... but you should know that. You really need to get an EGT preturbo on that thing. preferably an EGT per cylinder.... but who has that type of money.... oh wait. I'm talking to Mike... nevermind. lol go ahead order up 4 EGT sensors and get them installed.

Does the Autronic have Tip in maps? I know you can typically adjust the Tip in timing but Motec and Haltech are the only units I have been able to do so with fuel as well. Do you feel any adverse stumbles or anything? Its very common to have a lean situation with Map sensors as you reach the boost threshold. If you don't feel anything and can't adjust Tip in adjustments you can also try adjusting your timing around tip in. Depending on how the combustion is right at the change from vacuum/boost you can get crazy readings from a wideband. The biggest being that if you get a small misfire it will read as lean, and a lot of cars even stock cars will go lean right as you press the pedal causing lean misfires which read even leaner on a wideband then they truly are, especially going from really low throttle to WOT. IF you are out and about this week swing by the office and take me for a ride.

how is the fuel pressure when you are accelerating? fuel pump might be trying to catch up.

I cannot see the fuel pressure as my gauge is connected to my FPR. I dont think I would be having fueling problems as I have an A1000, but you never know.

I actually just tried a different injector driver and it help a little bit. Notice the graph on top is the new NISMO driver and the delay is only 200rpm vs. the custom injector driver I got from Autronic which has a 300rpm delay. I am going to run with the NISMO driver for now and get a complete tune done and go from there I suppose, unless someone on the Autronic Forum can point me in the right direction.

Toward the end of the top datalog I was just feathering the throttle to show what is happening.

Put a post up on the EFI forums trying to figure out what is going on and it seems as though no one is able to help. I have called my Autronic dealer and I also have a post on the Autronic forums and it looks like this one I will have to figure out myself.

injector duty staying consitsistent when under wot? maybe one is a split second lazy? try data loggin injector duty

Injector duty is near nothing. I believe it is around 8% or so.

injector pulse the same for all 4 i would log that, what did the efi fourms tell you?

You gonna swing by the office this week? I'd love to see what it feels like. Any chance the timing is too low in that load area and causing a misfire?

I think everything is going to be fine. I have most of it figured out now and I am hoping the rest of it will tune itself out. I had the idea of actually putting more fuel toward the no load sites and now it seems like the leaning out is almost gone. Hope to have it better later this week.

any updates Mike?

Have not really been out tuning as of late, been pretty crappy weather. I will more than likely just wait till Lewistown and get some logs where I can actually be going over 120.

I have decided to not be worried about it. The lean parts are only for a split second and there is no way I would be able to enter boost at any RPM site that fast. I will just autotune as usual and go from there. Lewistown is going to be very sweet this year.

DoodieHead [ADMIN] wrote:

The lean parts are only for a split second and there is no way I would be able to enter boost at any RPM site that fast.

should be fine, unless leaning under boost.

Agreed, I plan on fine-tuning my setup in Lewistown also. I would feel much more comfortable doing pulls and logs on a closed track rather than on an open stretch of road.