Stopping the fuel trims affecting WOT fueling
unless your car is from the planet Jupiter, the PCM is not going to look at fuel trim during WOT, on a scan tool fuel trim numbers are going to change, but the PCM is not worried about where the FT is at. The last time i checked fuel trim is used for fuel correction based off multiple PCM input sensors only during closed loop operation. Modded or not i hope to God your computer is not making corrections on fuel trim at WOT. You obviously are obilvious to open/closed loop operation. During open loop your computer ignores o2 sensor input, i dont give a damn what you say. Why do you think a car runs in open loop when the car is cold?? Because a cold car needs a Richer A/F ratio and it does NOT want the o2 sensor to pick up on it and make a fuel correction. Same crap during WOT when you go WOT you go lean at first but then a very rich A/F ratio, you do not want the PCM to correct that either so the PCM does not look at the o2. No o2 sensor = no fuel correction. and first post or post 23902392032039 who gives a ****. So instead of flaming me and tearing me apart, just tell me where you get the idea that your car still looks at FT during WOT. if your car really did look at FT during WOT you would not be doin this "mod" you would be callin up the lemon law hotline cause your car would be running like absolute garbage.
Thanks
- Bryan
CamaroPower... look at it from a scientific point of view 
https://www.evolutionm.net/forums/ev...trims-afr.html
Unless you can show us evidence otherwise, the point was argued and has been established. We see it, so you should too.
For the record, I'm not sure if it was whitespace, language, or something else... but you came off pretty bad and like your ish didn't stink.
Welcome aboard, hopefully you can provide something helpful in the future
https://www.evolutionm.net/forums/ev...trims-afr.htmlUnless you can show us evidence otherwise, the point was argued and has been established. We see it, so you should too.
For the record, I'm not sure if it was whitespace, language, or something else... but you came off pretty bad and like your ish didn't stink.
Welcome aboard, hopefully you can provide something helpful in the future
Evolving Member
Joined: May 2008
Posts: 194
Likes: 0
From: Oxnard, CA
unless your car is from the planet Jupiter, the PCM is not going to look at fuel trim during WOT, on a scan tool fuel trim numbers are going to change, but the PCM is not worried about where the FT is at. The last time i checked fuel trim is used for fuel correction based off multiple PCM input sensors only during closed loop operation. Modded or not i hope to God your computer is not making corrections on fuel trim at WOT. You obviously are obilvious to open/closed loop operation. During open loop your computer ignores o2 sensor input, i dont give a damn what you say. Why do you think a car runs in open loop when the car is cold?? Because a cold car needs a Richer A/F ratio and it does NOT want the o2 sensor to pick up on it and make a fuel correction. Same crap during WOT when you go WOT you go lean at first but then a very rich A/F ratio, you do not want the PCM to correct that either so the PCM does not look at the o2. No o2 sensor = no fuel correction. and first post or post 23902392032039 who gives a ****. So instead of flaming me and tearing me apart, just tell me where you get the idea that your car still looks at FT during WOT. if your car really did look at FT during WOT you would not be doin this "mod" you would be callin up the lemon law hotline cause your car would be running like absolute garbage.
Which is why the thread was started
R
Thread Starter
Joined: Feb 2007
Posts: 9,486
Likes: 67
From: Melbourne, Australia
regardless of how the st and lt fuel trims are affected...during WOT operation the computer goes into open loop operation which means it is ignoring the o2 sensor and IS NOT GOING TO MAKE A ST/LT FUEL TRIM CORRECTION if your car runs like **** during WOT operation either your car is not coming out of closed loop operation like it should or you have a fuel delivery problem that is restricting fuel under serious load conditions. There is no reason to change your fuel trims for performance.
Newbie
Joined: Jun 2010
Posts: 3
Likes: 0
Well, i do not understand why it affects WOT but i guess it does on these cars. Now why did they make them that way? can anyone tell me? I'm not trying to be a jerk or anything i just wanted to know why and see if i could make a good argument haha, but i just didn't think it could happen like that, everything i said was true. just not on these cars?
Thread Starter
Joined: Feb 2007
Posts: 9,486
Likes: 67
From: Melbourne, Australia
Because thats how mitsu have it setup (by design or not)
I assume that mitsu thought that having the mid trim affecting WOT would fix up some of the problems with changing fuels/climates.
In reality for a tuned car it causes more problems than it fixes.
For a default ROM the High Trim starts becoming active at about 1593.75 MafHz, which is pretty high, I cant tell you exactly, but its probably about 5000rpm/250load
So up until that point the ECU uses the Mid Trim when doing fuel calculations.
What this mod does it move the point at which the High Trim becomes active down to about 140load/2500rpmish.
Couple that with the fact that you are in openloop after 140load means that the High Trim should never move off ZERO, thus the ECU applies a ZERO correction to the fuel calculation.
We could bin the trims properly, ie make the High come in at about 200 MafHz, but I still think there would be a large deviation in the High Trim (ie more than a couple of %).
I assume that mitsu thought that having the mid trim affecting WOT would fix up some of the problems with changing fuels/climates.
In reality for a tuned car it causes more problems than it fixes.
For a default ROM the High Trim starts becoming active at about 1593.75 MafHz, which is pretty high, I cant tell you exactly, but its probably about 5000rpm/250load
So up until that point the ECU uses the Mid Trim when doing fuel calculations.
What this mod does it move the point at which the High Trim becomes active down to about 140load/2500rpmish.
Couple that with the fact that you are in openloop after 140load means that the High Trim should never move off ZERO, thus the ECU applies a ZERO correction to the fuel calculation.
We could bin the trims properly, ie make the High come in at about 200 MafHz, but I still think there would be a large deviation in the High Trim (ie more than a couple of %).
Well, i do not understand why it affects WOT but i guess it does on these cars. Now why did they make them that way? can anyone tell me? I'm not trying to be a jerk or anything i just wanted to know why and see if i could make a good argument haha, but i just didn't think it could happen like that, everything i said was true. just not on these cars?
A lot of Evo owners used to think that the Fuel Trims do not affect WOT operations. I stumbled on it in my Evo 9 and then with an Evo 10. Now it is well established that the trims do indeed add/subtract fuel during WOT operation.
I know for sure that Subarus and Evos do this. There should be other cars like this out there.
regardless of how the st and lt fuel trims are affected...during WOT operation the computer goes into open loop operation which means it is ignoring the o2 sensor and IS NOT GOING TO MAKE A ST/LT FUEL TRIM CORRECTION if your car runs like **** during WOT operation either your car is not coming out of closed loop operation like it should or you have a fuel delivery problem that is restricting fuel under serious load conditions. There is no reason to change your fuel trims for performance.
unless your car is from the planet Jupiter, the PCM is not going to look at fuel trim during WOT, on a scan tool fuel trim numbers are going to change, but the PCM is not worried about where the FT is at. The last time i checked fuel trim is used for fuel correction based off multiple PCM input sensors only during closed loop operation. Modded or not i hope to God your computer is not making corrections on fuel trim at WOT. You obviously are obilvious to open/closed loop operation. During open loop your computer ignores o2 sensor input, i dont give a damn what you say. Why do you think a car runs in open loop when the car is cold?? Because a cold car needs a Richer A/F ratio and it does NOT want the o2 sensor to pick up on it and make a fuel correction. Same crap during WOT when you go WOT you go lean at first but then a very rich A/F ratio, you do not want the PCM to correct that either so the PCM does not look at the o2. No o2 sensor = no fuel correction. and first post or post 23902392032039 who gives a ****. So instead of flaming me and tearing me apart, just tell me where you get the idea that your car still looks at FT during WOT. if your car really did look at FT during WOT you would not be doin this "mod" you would be callin up the lemon law hotline cause your car would be running like absolute garbage.
Well, i do not understand why it affects WOT but i guess it does on these cars. Now why did they make them that way? can anyone tell me? I'm not trying to be a jerk or anything i just wanted to know why and see if i could make a good argument haha, but i just didn't think it could happen like that, everything i said was true. just not on these cars?
I believe the reason for LTFT affecting WOT is for safety. Lets assume we are on the stock tune, like Tephra said, a tuned car is a different animal.
Now, if someone does something to their car (like adding an intake), and it starts to run really lean during closed loop, the ECU will add a bunch of fuel. Lets assume the trims are sitting at +15%. Now when you get heavy on the throttle, the ECU will add a lot more fuel into the mix, because it is assuming that you will run lean in Open Loop too. Smart for the stock tune.
But here we are tuning our cars to run at an AFR that is right where we want it. Not .2 AFR richer, and not .2 AFR leaner. We want it exactly where we set it. So we disable the ECU from changing things on us.
Now, if someone does something to their car (like adding an intake), and it starts to run really lean during closed loop, the ECU will add a bunch of fuel. Lets assume the trims are sitting at +15%. Now when you get heavy on the throttle, the ECU will add a lot more fuel into the mix, because it is assuming that you will run lean in Open Loop too. Smart for the stock tune.
But here we are tuning our cars to run at an AFR that is right where we want it. Not .2 AFR richer, and not .2 AFR leaner. We want it exactly where we set it. So we disable the ECU from changing things on us.
Evolving Member
Joined: Jan 2009
Posts: 150
Likes: 0
From: Singapore
You can get the right address from MUT, 0E.