On the X forums they are playing with the Closed Loop-LT Trim Control. It was discovered that if we lower the Hz value in the Mid -> High and High -> Mid to around 350 that closed loop WOT pulls are not affected by O2 feedback. The result is that the car at WOT will run about 1 full point leaner.

The idea behind this is that the LT Trim control affects MAF Hz areas for LTFT adjustments. Since the LTFT High never adjusts because STFT will go to 0 as soon as WOT is achieved, thus LTFT never adjusts but somehow the AFR is affected by about a full point.

By lowering the Mid and High change over points we essentiall eliminate this affect. Thus the car tries more to follow the Fuel table.

Absolutly wonderful way to get more consistant pulls for AFR tuning.

The question remains if Lean Spool is still available and active.

Paul

 

The 8/9 WOT aren't effected by Fuel trims like the Evo 10 though

The 10 does not "run a full point leaner" with this tweak. If you tuned the car with the fuel trims wack then yes it will either lean out or richen up (depending on which way the fuel trims where wack) when you do this mod. However, if the car was tuned with good trims (as close to zero as possible) then it will not change the WOT fueling just by doing this mod.

2008 Evo 10 does not have lean spool on

2010 does

2009+ Ralliart does

- Bryan

 

My trims are both less than -5% and STFT is usually around +/- 2% so my trims are pretty good. I logged a consistant 1 point leaner with doing this.

My car is an VIII.

Please explain furter.

Thanks.

 

I do not see that happen with the 10's when doing this mod/tweak.

I have yet to do it on the 8/9 because I do not see the LTFT affecting WOT fueling at all like it does on the 10's.

It's interesting that you see 1 point leaner by doing this mod on a 8.

- bryan

 

Fuel is affected by Lean spool and "other" ways....thus, we never see the same o2 value from a WB as we do from what is in the fuel tables. These "other" ways are being discovered. The LT trim very well could be one of them.

I apologize if I didn't get everything exact from the X forums. I tried to remember everything i read a couple days ago.

The theory is pretty legit though.

By making this tweek...one less thing is messing with the values in the fuel table and the car tries to run more true to them. At least in my case anyway.

I do still have LS enabled. I am still about a point and a half away from my values posted in my fuel tables. I will test eventually if disabeling LS and doing this tweek will result in closer to fuel table O2 readings.

 

I wonder if it's another 03-04 difference like the WGDC differences.

Interesting finding on your car. Do you have a log of before/after AFR with *just* doing this mod?

Since you have LS still on, I wonder if the LTFT effects that operation?

It's standard practice for me to always turn LS off so that could be why I never see LTFT's effecting WOT on 8/9's.

- Bryan

 

Unfortunatley, I did do other things to my ROM when I made this tweek. mostly in the idle areas. I can, hopefully do a few pulls this week with the tweek applied and not.

The cold air here makes for big inconsistancies in pulls anyhow.

Heck, this could be a fluke of weather. I did the pull in 40 degree air early in the AM before the sun was up. But my boost was consistant as always so who knows.

 

This was found by mrfred last week through dissassembly. The LTFT high is locked at 128 on the evo.

https://www.evolutionm.net/forums/ec...l-options.html
Post 95

 

Explain in a little better detail please. What does this mean?

 

If you are over 1597 Hz, Fuel Trims have zero effect.

 

It's pretty well explained in that thread, but if you are above the mid-high LTFT transition point, the high trim is set to 128, which effectively sets it to a multiplier of 1 and has no effect on fueling.

Changing the transition point to a lower frequency should have the added effect of eliminating fuel trims from WOT fuel control while at moderate loads. A stock car after all pretty much stays under 1600Hz and thus the Mid fuel trim will affect all fueling conditions on a stock-ish car.

 

Thanks for the clarification.....I thought I was on the right track with this thread.

 

Mrfred posted that LTFT mid do affect open loop fueling on Evo VIII/IX. Anyway have the address for the Closed loop - LT Trim Control table on the 96530006 ROM?

 

Mrfred posted that LTFT mid does affect open loop fueling on Evo VIII/IX. Anyway have the address for the Closed loop - LT Trim Control table on the 96530006 ROM?

 

Yes, it looks like it, if the car is slow and under 1597 Hz.

- Bryan