How long to wait after ECU reset?

[Wurf]

Hey guys,
I just switched out my SRI and put my car back to stock. I did it for an oil change and figured I 'd leave it for awhile.
I disconnected the battery during the swap so the ECU has been reset.

I have been driving the car "normally" since putting the stock airbox in it and wondered how long I really need to wait until I can be confident the ECU has re-learned the stock setup.

I'm curious to compare the stock box to the SRI over a reasonably long period of time. The SRI was on the car for around 3K miles and it took what seemed like a couple weeks before the car seemed to "wake up".

As of now, the car is not nearly as responsive or quick with the stock airbox. With the SRI the tires would just start breaking loose at the top of second gear. With stock airbox - NFW.

Just curious how long you think I should basically torture myself waiting to put the SRI back in the car?

Oh...and I'll be adding the PG TIP when I do it. I have not installed it yet - still sitting new in the box.

Thanks

 

[mazdaspeed32007]

not long. your parameters are ok and all set after a few cycles. x key cycles, so many miles, so much driving in 5th gear, catalyst readings for so many miles.....bunch of stuff that takes a hundred or so miles to complete. give it like 50 miles and youll be set to romp.

 

[Wurf]

Thanks,
Experiment completed I guess. Car is no fun compared to when it has an SRI on it.

 

[destrux]

Did it seem faster right after you reset it, then felt like it went flat after a few drives?

Mine gains 10whp just resetting the ecu... my power actually goes down after I drive for a week and re-dyno it. Comes right back up by a completely predictable 10whp just by resetting the ecu though.

I no longer reset the ecu when changing parts... I do a few half throttle and full throttle runs through the gears on the dyno between taking readings. I get more reliable results.

 

[Wurf]

That's an interesting idea and confirms what I felt with the car.
Also confirms what I felt when I put the car back to stock recently. It ran pretty strong for a few weeks and then sort of lost it's punch a bit later.

I think I'll give that a shot in the spring when I put the SRI back on the car along with my summer wheels and tires. I'm still shopping wheels at this point.

Thanks for the post and the info.

 

[mazdaspeed32007]

you shouldnt reset your ecu and run it hard. the reason your ecu needs time to reset is to determine the values each parameter needs to run at. when you first reset your ecu you havent determined ltft's yet or anything. watch your A/F ratios when you reset, theyll jump all over the place until the car gets a feel for itself.

 

[Mistersix]

could be, you physically adjust to the pull of acceleration. not that the car gets any slower.

the brain can be tricky. its hard to tell the difference sometimes. lol!!!

 

[socks]

Mine gains 10whp just resetting the ecu... my power actually goes down after I drive for a week and re-dyno it. Comes right back up by a completely predictable 10whp just by resetting the ecu though.

you surely cant attribute that to resetting your ecu.

there are a million other variables to take into account. weather, dyno operator, engine temps, etc.

at WOT, the car doesnt use any of the fuel trims to make changes to fueling tables. it goes strictly off Open Loop fuel tables. Which do not change when you reset your ecu.

so basically, at part throttle (in closed loop), you may see a difference in power, but at WOT (Open Loop), you will run identical before and after resetting your ecu.

 

[wassup61]

You need to realize it takes 3-5 drive cycles and 50-100 miles to set readiness and fuel trims to allow proper WOT AFR.

 

[destrux]

I'm not going to pretend I know everything that goes on inside the MS3 ecu (yet), but something is causing a large power gain when I reset the ECU. I know you shouldn't drive the car hard right after an ECU reset, and I normally wouldn't, but this was for the sake of testing exactly what the results of doing this would be. Alot of people install parts and reset the ECU and then revel in the huge power gain. I had a thought that it might be (in part) due to the ECU itself, and not the new part.

I was operating the dyno myself, it's a brand new Dynocom DC1800SZ inertial dyno. It's very repeatable between runs and has built in weather correction.

I brought the car in after a 15 minute drive, strapped it down, set the fans up (one large high volume one in front, one high speed/medium volume strapped right to the TMIC, hood up). Did 3 runs to stabilize temps, with 10 minutes between runs. Did a baseline run, cleared the ECM by disconnecting the battery for a few minutes, then did another run. All runs were 10 mins apart. Power was nearly identical, within 3 whp on the first 4 runs. It improved a bit from the first run to the 4th run due to the ecu "learning" the load of the dyno. The ECU reset run was drastically different. The power curve both changed shape and had a drastically different peak power. The car also sounded deeper and more powerful, and the run took less time than the first run.

Here's the dyno chart of the 4th and 5th runs. I didn't include the warm up runs because they are irrelevant.

The red run is the ECU reset run.

Also of note is that the car came back in on the dyno a month later and put the same baseline numbers down (well, within 5 whp).

 

[mazdaspeed32007]

your ecu needs time to adjust to all the values added up over a period of time. at WOT with an ecu reset your vehicle has no values to base anything off of.

lets say a little boy doesn know the stove is hot....he puts his hand on the stove. BURNED!

he wont do it again....he learned that this isnt the correct thing to do. he adjusts how cautious he is around stoves and becomes aware of how to react around the surface.

i think this is how the ECU reacts. it hasnt had a large selection of parameters to get an average from so it hasnt learned how to adjust to certain situations. sort of like first putting on an intake....then 100 miles later. your power curve is the engine and ecu making adjustments along the way based on driving style, temp, humitity etc...

 

[destrux]

Exactly... if you look at the red dyno line, you can see the ECU freak out and pull timing at 3,750 RPM, most likely due to a knock event.

Again, not something I plan on trying ever again with any car (especially not one I'm still making payments on).

However, the stock ECU base map is still conservative enough that it won't cause a nearly stock car to blow up from a WOT run right after an ECU reset. Most cars have a more conservative base map than what the car will adjust itself to. I remember reading an article in SCC a while back that their Subaru WRX project car lost power after an ECU reset and it took a few hundred miles of highway driving for the ECU to relearn and get the power back. Apparently Mazda went the other way and decided to put a fairly aggressive base map in there. Must have wanted to impress people on the test drive. That would also explain why the sales guy told me to "see what the car can really do". I think he was surprised when that turned out to involve DSC active braking intervention...(drive2)