Excessivly lean Idle? (18-19:1 AFR's?)

[forcefed86]

I’ve been trying to get my car to idle decently since day one. Fought it with the factory ECM and now I use a SD Ostrich setup to tune. Seems to be a never ending battle. Recently did a HG job and blocked off the IAC and the FIAV completely . Blocked all my coolant lines etc. Recently (pretty much by accident) I found my idle seems much better (pulls the most vac and is the most stabile) At 18:1-19:1 AFR!?

With the car fully warm I’d always s kept my AFR’s around 13:1 and 10* of timing. I’d pull around 16inhg this way at 1200-1300rpm. If I moved timing or the mixture up or down from there I’d get less vac and a more erratic idle. Idle was never rock soild and would always bounce around. So recently I was playing around tuning the cars idle and accidently made what I thought was to large of a change to the idel cells. AFR’s jumped to 18.5-19:1 and the car smoothed out massively. Vac dropped to 19-19.5. The car idles great (once warmed up) at these lean mixtures. WB02 is an innovate unit with a self test/calibration. It seems to be spot on.

Anyone else idling this lean? Just doesn’t make sense to me

 

[Archer Fabrications]

Are you on speed density? If so raise your VE in your idle zone of the map.

 

[forcefed86]

Are you on speed density? If so raise your VE in your idle zone of the map.

Not sure I'm following you... Yes I use speed density, and I know how to use/tune with it.

The car idles best this way for some reason. I'm not trying to richen it up. Just thought it was weird and wondered where other 4g63's like to idle AFR wise. And if anyone had a theory as to why my setup seems to like such lean mixtures at idle.

 

[MY1GDSM]

What Kind of timing are you seeing at that AFR now? might just be hitting different load cells changing the ARF so drastically 5 or so points then before an hitting some load cells with higher timing. Had to say with out a log or knowing what your maps looks like
Is this on gas e85 what fuel? you obviously are not putting a load on the motor at idle and the ARF is gonna be fine there. though probably not Idle for emissions

The only thing you are doing is raising the NOx level by leaning it out or raising the timing. I personally run quite a bit of timing at Idle compared to what is "stock" for a mitsu and never have any issues with the AFR's being erratic. But I lock things in closed loop as well (most the time) and run leaner as well then 14.7 most the time...
I'd just see be sure that you don't have an exhaust leak that the Wideband has been free-air calibrated and Run what ever combo of ARF and timing the car seems to respond overall best too

I'd rather be if with-out a choice, At that lean AFR at Idle then 13:1 and that low of timing :/

 

[forcefed86]

Good point on the exh leak that would make sense. I had been running an open dump so I doubt I'd notice.

Yes, E85 fuel. (e70 winter blend currently) Timing hasn’t changed, I have 500-1700rpm blocked out at 10* for all loads. I’m not worried about it hurting anything, I was just surprised it would run at all. Even more surprised it idles much cleaner and pulls more vac. I’m open loop at idle as well, jumps into closed loop above 1700 rpm and back out at 4k. I have lean cruise around 16.0. Seems to be happy there.

I had always hunted for the highest vac at 13-14ish AFR. I tried adjusting timing from 5* to 22*. 10* ended up pulling the best vac at my previous AFR’s. After I find the exhaust leak I’m sure I have, I’ll have to play with timing again to find the happy point.

Luckily no emissions here in KS.

-thks!

 

[MY1GDSM]

Sounds like to have a handle on things, But I'd try out a bit higher timing again between that range after you see if you have a leak on a bit leaner AFR bet you pick up some more vacuum and the car recovers better when getting put under a load or coming to a stop etc.