I have an odd idle AFR problem I'm wondering if anyone has heard of before.

I monitor AFR closely during my daily driving with an AEM gauge. The car at WOT at around 26 psi runs around 11.5, descending to 11.
Part throttle @ around 6-14 it starts leaning out, I let off, or increase load because it starts going north of 13. This gives an uncomfortable feeling of having to go WOT, or less than ~140% load. A difficult task when passing somebody on the highway, and not trying to **** anyone off.

At idle, I have what feels like two "waves"
-The first being the expected STFT "bounce" of about ~.6 AFR.
-The second is a wave with a period of about 6-10 seconds where I've seen my 0.6 "bounce" appear to settle north of 16.0. It goes so lean, the car begins to miss for a second or two, enough to throw a p0300 if it idles for long periods. After these "misfire events" the AFR quickly drops to as low as 11, all of this at idle, and slowly works it's way off the lean side of my gauge again to repeat. It also idles like a big cam muscle car all the time, but I've shrugged this off to the aftermarket cams. It seems to idle at about 800-1,100 rpm.

I've had the car stall, while warmed up, a few times because of this. Once on restart attempt, after a few seconds of crank-no-start, I had to dump the throttle a bit to get it going. It will also seem to do this if it's started, ran for a minute or less, and then restarted.

My Idle LTFT almost always has gone to +12.5% I'm waiting for my cables to come in to verify, but I suspect this is a scaling issue. I had the car flashed to a basemap from a previous E85 tune to get it home, I just wanted to see if anyone else had any thoughts that I did not about it. Idle is really the only odd thing, other than that part throttle in boost 13+ AFR.
-ID1700's (Too big to run on 91 without proper scaling?)
-91 Octane (can't get 93 in Iowa)
-9.5:1 compression, 150 psi

Another thing I wanted to ask was open loop. Is there any danger to running open loop all the time, other than the added responsibility of closely monitoring AFR? I would like to run slightly leaner at cruising loads ~15.5. I've had to start the car cold in temps less than 0C so i'll be paying close attention to enrichment values.
Would the proper way to do this in ECU flash were to increase the closed loop coolant temp to an impossible value?

Thanks in advance.

 

Because I don't know about your current rom, I can't give accurate indication. Did you check the fuel pressure in the situation the issue occurs and the fuel pump and fuel line? Switching between open and closed loops may not be good.

Since it is necessary to make afr follow 14.7 in low load area, closed loop feedback with narrow band o2 is recommended. Open loop cannot follow changes of various factors such as temperature.

As your motor is 2.2L (and a high lift cam?), maf scaling, map based load calc tables must be tuned. Also it is necessary to adjust injector maps for idle. My recommendation is to use a minimally sized injectors and fuel pump which can fuelling at wot (if possible, a multi-hole one).

 

Have you tweaked your low pulse width IPW adder table at all? It's pretty much mandatory with ID1700's. Also assuming you have already done the Min pulse width rom tweak so the injectors are able to idle at lower pulse width?

Here is how I have mine setup. It got rid of all my part throttle issues that where close to the same as what you are describing.

As far as idle. I have S2's and it purrs like a kitten at idle. Basically zero lope. This also has a lot to do with how your mivec tables are tuned.


Idle, this is on E85, but you get the idea

 

It's the AMS spec Kelford cams, I was unable to find the duration or lift due to it being proprietary.
That's good to know about temperature, because I may see days as low as -10F, and as high as 90F in the summer. I'm at 1,300 elevation. Based on your advice, I'll stay with closed loop enabled.
A follow up question though, is it possible to specify a target AFR in closed loop?

I have not dived into the car to see what it has currently. All my cables, including the car are in Iowa. I'm down here in Florida with weeks of spare time, so I've literally read about 300 pages of information regarding evoscan and ecu flash. I took what you gave me just now and read up a bit on it, I'm not quite sure on how to find how much compensation I need at certain voltages.

Since the car was flashed to a basemap from E85, I doubt they spent any extra time with IPW adder. What data should I be looking at, or searching to find how much compensation my car needs? I suppose I could start with what you have, and just go from there.

I had a couple times while the engine is still in closed loop, below 32F bog like hell at part throttle, like pulling the choke on the car while AFR drops to 10. I've had to just barely accelerate to keep it clean.


Thanks for the info, I don't find these challenges annoying at all, but rather exciting to learn and apply.

 

Bryan's post is very useful for you to adjust your injector maps.(it is just for ID1700).

I think it's not possible. Fuel maps like 'High Octane Fuel Map' effects only in open loop.

Tuning for a high lift cam, especially stabilizing the idle range seems difficult.
It might be better getting a (e-)tune by a experienced professional tuner(Bryan is one of them).

 

I would be open to that. I can handle the more basic timing, MAF/Injector scaling, and AFR adjustments. I don't have enough confidence to mess with the MiVec tables, so I would probably opt for that.
This summer I'm going to have Kozmic install some better clutches and a heated sump kit to fight the harsh winters. I'll probably have them tune it along with the clutches and valvebody changes.

The goal I have for the next month is to get it running cleaner and better till I can get it to them in the summer for the power.
They suggested doing the E85 flex tune, but I'm hesitant after reading how difficult it is to do it properly without hammering the bearings to hell, AMS also recommends against it on their engines.
I also NEED a 91 octane map for road trips. Doing an E85 tune even thought he fuel system is ready for it is not something I'm too interested in.

I'd take the 400whp and less stress on the drivetrain over the 600whp.

 

You can have true flex fuel and put in any percentage of Ethanol from pump ethanol to pump gasoline and it interpolates between the two. That way you don't have to worry about the mix at all.

As far as E85 hammering bearings, only if the tune is horrible, but it's not because of E85. I've run E85 and tuned for E85 for over a decade and have never ever had bearing issues. My current build is 640whp on the street and 540whp on track and we recently took a look at my bearings and they look brand new.

Still amazes me how much ignorance there is around Ethanol. (not talking about you)

 

No offense taken, there is a lot of conflicting info about it.

Well hell I never knew the flex tune kit was that versatile, that's fantastic. I'll go that route for sure then, ethanol out here is usually high quality. (understandably being in Iowa, there is a massive ethanol plant 20 minutes west.) I'll just run pump in the winter to keep things warm.

Thanks for your info and experience.

 

threads and a site to read before you modify your rom.

1. new fuel related maps "Low Pulse Width IPW Adder" and other injector maps probably useful for your issue.
2. Flex Fuel testing in TephraXMOD V3 tephra's site About flex fuel feature of TephraXMOD V3. "Injector Scaling and Interpolation" section may be usuful for your case.

 

These "wandering/erratic AFR at idle" posts are rampant and I'm experiencing the same issues. Mine also happen at cruise, but appear to be stable under moderate+ acceleration (open loop I believe). The one thing I'm noticing, but haven't 100% correlated, seems to be ETS intakes. Do you happen to have an ETS intake? It could be this is just because so many people have ETS intakes, but that's something I'm trying to rule out right now.

 

I've determined the condition to be acceptable for the cams and injectors.

I have an ETS intercooler pipe, but that should not matter.
My intake is an AMS 3.5"

At cruise, I can see anything ranging from 13-16, however most of the time it does just fine 14.7 +- 0.5
There is a table you can specify open loop criteria, but I would not see a reason to mess with it.

I don't know the difference between #1 and #2