ECU Learning & driver habits

M

MacheteJames

Greenie N00B Member
Greenie Member
Hey guys,

Question for those of you who are savvy on the inner workings of the MS3 ECU. I've had my Speed (mostly bolted, Stratified tuned) for almost 10 years and have been doing a lot of boring driving as of late - kid daycare dropoffs, grocery runs, etc. I have stretches of multiple days where I don't even hit boost. What I've noticed is that after a run of time out of boost, the first time I get into boost, the car does fine, but feels a little soft. Say I do a second shot of boost soon after, though, and everything feels noticeably stronger. The exhaust even seems louder and angrier and there's noticeably more shove. I don't have any logs to back this up yet, but I have a hunch that the ECU has a learn mode that monitors pedal position on a a given drive and has the ability to add fuel and timing as needed within a certain window. If it sees you hooning around, it can add timing, or pull timing if you're largely cruising out of boost. Am I off base with this?
 
MacheteJames said:
Hey guys,

Question for those of you who are savvy on the inner workings of the MS3 ECU. I've had my Speed (mostly bolted, Stratified tuned) for almost 10 years and have been doing a lot of boring driving as of late - kid daycare dropoffs, grocery runs, etc. I have stretches of multiple days where I don't even hit boost. What I've noticed is that after a run of time out of boost, the first time I get into boost, the car does fine, but feels a little soft. Say I do a second shot of boost soon after, though, and everything feels noticeably stronger. The exhaust even seems louder and angrier and there's noticeably more shove. I don't have any logs to back this up yet, but I have a hunch that the ECU has a learn mode that monitors pedal position on a a given drive and has the ability to add fuel and timing as needed within a certain window. If it sees you hooning around, it can add timing, or pull timing if you're largely cruising out of boost. Am I off base with this?
Click to expand...

What spark plugs are you running?
 
Your car learns short term and long term values for fuel trims in order to keep fuel economy and emissions ideal. It doesn't keep track of that during WOT because under WOT you're only there for a limited time.

The ECU wants to keep your fuel trims usually within +/- 10% but 5% is really ideal. Anything over 10-15% and you'd get a Fuel Trim Rich or Lean code.

With that in mind you probably drive the same route on a regular basis and the same regular speeds so you only go into certain cells on the ECU map. The ECU is only changing fuel trims based on the cells it is referencing during drive cycles. It doesn't change anything else across the board. Try driving a little different. Keep the RPMs a little higher or lower than you would but within a safe margin.

I.E. you're cruising at 45mph in 5th gear try doing it in 4th for a while. You'll use a little more gas but the increase in the RPM area will allow the car to monitor the STFT/LTFT values in that area of the map which isnt touched. Then see if you still have that hesitation or issue compared to where you're at now. Or use a higher gear at a lower speed without causing too much load or strain on the engine. That way it fills in the bottom area as well.

But also check over mechanical things stated above, spark plugs, carbon build up, boost leaks, fuel quality etc.
 
MacheteJames said:
These days, Autolite XP5364, stock heat range. I ran ITV-22s step colders for several years before this. Are you thinking that plugs have something to do with it?
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Correct. Plugs can foul and cause inconsistent behavior as you have described. They are also a general maintenance item.

I strongly recommend sticking to the original spark plug supplier for you vehicle and even more with the exact type of plug. I have seen mixing brands cause noticeable issues with performance.

It depends on your modifications and power output, but normally, you need to stick to OEM heat range for spark plugs. This is especially true if you are NOT pushing the car to limits where it struggles with dissipating heat. Colder plugs will foul easier if they aren't properly used.

My recommendation to you: Switch to OEM NGK LTR6IX or step colder if you and/or your tuner have identified that you need that plug heat range.
 
The_big_dill said:
Correct. Plugs can foul and cause inconsistent behavior as you have described. They are also a general maintenance item.

I strongly recommend sticking to the original spark plug supplier for you vehicle and even more with the exact type of plug. I have seen mixing brands cause noticeable issues with performance.

It depends on your modifications and power output, but normally, you need to stick to OEM heat range for spark plugs. This is especially true if you are NOT pushing the car to limits where it struggles with dissipating heat. Colder plugs will foul easier if they aren't properly used.

My recommendation to you: Switch to OEM NGK LTR6IX or step colder if you and/or your tuner have identified that you need that plug heat range.
Click to expand...

I appreciate this reply. I've gone to an 8,000 mile/every 6-7 months replacement schedule because plug degradation is noticeable after that point. FWIW the ITV-22s would foul out even sooner, which is why I stopped using them. Low-intensity daily driving is not kind to step-colder plugs.

Are those NGKs pre-gapped to the recommended .026-.028? I'm always leery of regapping plugs too much, as the change in geometry between the insulator and electrode is a known contributor to a poorer spark. My current Autolites, while dirt cheap, are at something like .035 before I gap them down.
 
MacheteJames said:
I appreciate this reply. I've gone to an 8,000 mile/every 6-7 months replacement schedule because plug degradation is noticeable after that point. FWIW the ITV-22s would foul out even sooner, which is why I stopped using them. Low-intensity daily driving is not kind to step-colder plugs.

Are those NGKs pre-gapped to the recommended .026-.028? I'm always leery of regapping plugs too much, as the change in geometry between the insulator and electrode is a known contributor to a poorer spark. My current Autolites, while dirt cheap, are at something like .035 before I gap them down.
Click to expand...

They are not gapped to that recommendation. I have not seen studies about gapping plugs causing poor spark, in fact, the gap is decreased to improve the spark.

Plugs are not guaranteed to fix your issue, but are a possibility to the symptoms you describe.
 
If you are fouling stock heat range plugs every 8,000 miles you have something wrong with your car
 
I've had a similar issue. put one NGK one step colder plugs and everything was perfect. when i got my stratified tune i told them i had the NGK colder plugs, tried to run Stock heat range plugs and car felt slower. maybe proper combustion has something to do with it? notice difference is what im getting at.
 
MacheteJames said:
Yeah, no. The car's fine. 8-10k miles is within Cobb's expected plug change interval for a modded car as per their Accessport documentation.
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Lmao what!? Dude I've been on the same set of plugs on my modded car for over 2 years with 20k miles put on them. If you were running copper plugs then possibly that could be the case. It's probably a garbage tune or other mechanical issue causing them to foul that quickly.
 
Just because Cobb says something does not mean it's correct. They put out the products and then stopped following the platform or staying current I'm surprised we even got further rpm support for the gen2 on the accessport. 8k is certainly too little should be about 13-20k miles. I'd swap off autolite and go NGK if you're tuned for step colder and running stock heat range that could also play a role.
 
LOL, I've been in this scene for way too long to get piled on like a brownie back on MSF in 2012. Maybe it's the mediocre Autolite plugs that I've been using for the last year, or maybe it's something else. Suffice it to say that I feel a noticeable drop in smoothness at 8-10k miles, I take the plugs out, swap them, and it gets better. Happened on my previous Dizzy tune and still the same on my current Stratified tune. My Speed is mostly a daycare hauler/commuter these days anyway so it's all moot.
 
Awafrican said:
Just because Cobb says something does not mean it's correct. They put out the products and then stopped following the platform or staying current I'm surprised we even got further rpm support for the gen2 on the accessport. 8k is certainly too little should be about 13-20k miles. I'd swap off autolite and go NGK if you're tuned for step colder and running stock heat range that could also play a role.
Click to expand...

Yeah, I am tuned for step colder plugs currently, but as per all recent advice on this forum and elsewhere, I swapped from ITV-22s back to stock heat range plugs because of the mundane driving I was/am doing most of the time. I'll give the NGKs a try for the next round of plugs - haven't run those since my first plug change years ago.
 
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