RoadSpike

iTrader: (5)

Well its hot outside and I tend to use my AC alot and the low RPM leaning out thing was really starting to bother me. So for the safety of my engine which i don't want to run leaner than 15AFR when at load I've come up with a really interesting solution to the problem the SD cars seem to have leaning out at higher loads and lower rpm

500-1500rpm is what i'm covering here.

First thing to do is remove any other patches you did to the car such as modifying the fuel table to compensate by setting them to the right 14.7 AFR values.

The solution was to set the RPM VE tables to 95,96,100,100 for the first 4 entries. This stopped the car from running stupid lean at higher load but gave me a rich condition.

Since my car idles at a steady 31hz airflow, which can be logged. I decided to mess with maf scaling a bit and got a fix going. Simply what i did was change the 25 hz entry to 35 hz to basically to cover just above idle range and changed the maf scaling accordingly.

Next I went into Maf Compensation and lowered the now 15 and 35hz ranges to about 84% compensation removing the rich condition. Flipping my AC on and off at this point made the car go slightly lean but not super lean like before. I found for my personal car the AC ramps airflow hz to about 50hz which gracefully is in the maf hz side bar already so i set it from 99% or so to 101% and now have a really stable AFR.

I can get some pictures later

l2r99gst

iTrader: (2)

As long as your fuel trims weren't way off to start with, this method, in the long run unfortunately won't do much I don't think. The reason is because whatever changes you make to closed loop fueling will eventually be reflected in the long term fuel trims, basically putting you back to where you started.

But, that's why I always stress to make sure that your VE tables are setup properly in the first place. I mean by creating a 3D chart and covering as many load/RPM ranges as possible. A good thing to do is to chart your selected LTFT+STFT and make a 3D chart of that. That will show you exactly where your closed loop fueling issues (lean and rich) are at. Then, either the VE tables and/or maf tables can be used to fine tune those specific areas (hard to target specific areas without a 3D VE map, but it can be done with some clever adjustments...or just use the maf tables at that point).

RoadSpike

iTrader: (5)

That would be right if i used closed loop at all which I don't.

Definitely agree the best way is RPM VE logging. My main issue was when logging the rpm VE I got a range from 65% all the way to 96% in those ranges. I've just now stumbled on a way to emulate that range using maf compensation in a somewhat clever manner is all.

SD in general for idle seems to be simply a compromise between idle stability and driving perfection. Hopefully tweaks like these will make it easier on people.

l2r99gst

iTrader: (2)

Yes, what I stated is only if closed loop is enabled. If you are running open loop full time, then fuel trims have no effect.

Out of curiosity though, why are you not running closed loop fueling. STFT can help rapdily adjust fueling to accomodate for changes in fuel needs, whereas running open loop you get no correction. Have you tried simply using closed loop...maybe that will cure your problem?

I see a few people that disabled closed loop and I'm just curious why. I think closed loop fueling is much better in eliminating pesky little issues like this rather than trying to nail down an open loop tune with so many variables.

RoadSpike

iTrader: (5)

I have basically disabled it for anything other than the lowest level load and idle. Soon as the AC kicks in the load is higher than its set and it moves into open loop.

The point for me is open loop lets me know exactly how well the tune is setup rather than relying on the computer to adjust the fuel. If i leave it in closed loop forever it would simply run too rich at one point and too lean at the next point because the tune isn't setup right at those loads.

I may consider putting closed loop back to normal now that my low rpm issues are worked out. Don't need the computer constantly fighting the tune they should work together. Hope that makes sense.

95630706

Is this something I can do post SD conversion? Can you point me in the direction of a thread on how to do this is, and what to log?

Many thanks.

03whitegsr

iTrader: (8)

I did something similar to this, although I tuned the SD settings to provide a good idle AFR and then richened up the 50Hz-125Hz range to help with the lean issue around 1500 RPM. It helped some, but didn't solve enough of the issue for it to not **** me off on a daily basis.

Looking back on it, I like tuning the VE stuff for good driveability and then using the MAF table to adjust idle like you did since idle will really only take place at 1 or 2 HZ values.

I still believe there is some kind of additional correction kicking in that the SD patch doesn't deal well with though that is causing the lean issue.

RoadSpike

iTrader: (5)

Essentially make the car run open loop and compare your desired AFR to actual WB AFR and see how much fuel needs to be added.

RoadSpike

iTrader: (5)

I think its simply a matter that at these low rpm the gradient values for airflow hz doesn't match up with the SD calculation. Its probably a small curve at the beginning of the sensor then smooths out to a nice flat ramp up later. It seem that even Mitsubishi had to deal with it in a similar fashion however not to the extent a forced smooth linear plot is making us face.

l2r99gst

iTrader: (2)

^^This

or

Log selected LTFT and STFT. Make a 3D chart or selected LTFT+STFT for map vs RPM. This will show you where and how much (what percentage) that closed loop is adjusting your fueling.

I don't have time to dig up the old threads, but there are charts that I think jcsbanks and I both have posted in the original SD thread by jcsbanks.