Resetting ECU Periodically for Better Drivability

[DrewA]

I notice that when I reset the ECU by pulling the clock fuse the car seems "peppier" by a seat of the pants feel. Almost as if it was breathing better. I never get a CEL and the light does work.


It stays this ways for several months then the performance seems to go off. Is the ECU learning from my bad driving habits or am I dreaming?

Anyone else experience this?

This is on a 91 NSX, no mods, 80,000mi, driven daily a couple of miles back and forth to work and sometimes briskly on weekends.

Drew Altemara

 

[Larry Bastanza]

Hi Drew,

When you "reset" the ECU you are flushing the "Fuel Trim" data. the ECU does learn and adapt as it learns. Although somewhat speculative (since I personally did not program the ECU), I beleive the "Fuel Trim" algorithm will work more on an "emissions minded" basis.

So resetting the Fuel Trim, and running on the "base fuel map" most likely richens it up a bit, giving you the results you experience.

My $.02,

Regards,
LarryB

 

[stuntman]

Hi Drew,

When you "reset" the ECU you are flushing the "Fuel Trim" data. the ECU does learn and adapt as it learns. Although somewhat speculative (since I personally did not program the ECU), I beleive the "Fuel Trim" algorithm will work more on an "emissions minded" basis.

So resetting the Fuel Trim, and running on the "base fuel map" most likely richens it up a bit, giving you the results you experience.

My $.02,

Regards,
LarryB

Larry,

Sport Compact Car (I believe) did an air intake test on a few cars. They dynoed the cars after thousands of street miles, hard-reset the ECU by unplugging the battery, re-dynoed it and most made 2-5whp gains. According to that article it said that daily driving caused the ECU to become richer and by resetting the ECU, the leaner 'learned aggressive behavior' made it leaner and made more power over the factory 'learned' rich setting (for motor longevity/safety).


0.02 fwiw

 

[RON98]

is the rich condition from the o2 sensor getting less responsive with age?

did they specify in the article as to reasons why?
with hundreds of hours in R&D for the tuning and today engine building standards, they should have the engine dialed in spot on. also anyone know the % change that most mfgs allow the O2 sensor to adjust over fuel trim?

i don't use o2 sensor feedback on my tuned cars. Once it dialed in, i forget about unless i see need to readjust on the wideband. Sometimes ecu's do silly stuff with the aid of the o2 sensor esp if using mixed fuels O2 sensor is on the way out. On customers car's its +-3% unless they ask for something different.

 

[stuntman]

is the rich condition from the o2 sensor getting less responsive with age?

did they specify in the article as to reasons why?
with hundreds of hours in R&D for the tuning and today engine building standards, they should have the engine dialed in spot on. also anyone know the % change that most mfgs allow the O2 sensor to adjust over fuel trim?

i don't use o2 sensor feedback on my tuned cars. Once it dialed in, i forget about unless i see need to readjust on the wideband. Sometimes ecu's do silly stuff with the aid of the o2 sensor esp if using mixed fuels O2 sensor is on the way out. On customers car's its +-3% unless they ask for something different.

It was a new STI, G35 I believe, and I forget what else.

...not sure, seems like relatively new cars

RON: so how do you deal with altitude changes if someone drives up in the mountains? Do you stay closed-loop?

 

[RON98]

It was a new STI, G35 I believe, and I forget what else.

...not sure, seems like relatively new cars

RON: so how do you deal with altitude changes if someone drives up in the mountains? Do you stay closed-loop?

hum... maybe they get it close and just let the ecu take over

Hi Stunt,

this is on my own cars, keep that in mind. I have had wideband o2 sensor go bad on my quickly which changed my fuel trims.

Once the engine mapped, there is no need to go back and change it again unless there are changes to the VE in the motor. All other variable can be accounted for by fuel trim adjustments which are tuned while on the dyno and input according to calculations. If you steady state map the complete motor, it takes care of itself.

i also take off the factory sensors and change my cars over to speed density which in itself accounts for density of the incoming air. there is still debate over barometer corrections with speed density but i never had to use it.

another thing, because i run mixed fuels, high boost and rich, it takes a toll on the o2 sensors. I cant afford keep buying them. Once the car is dialed in. I either remove the o2 sensor all together or just keep it in there to monitor then take it out. i put it back in once in a while to watch

 

[DrewA]

Interesting replies.

I wonder if this is more noticable on older cars like mine that are driven only a couple of miles to/from work? I wonder if as the catalyst ages and soots up it becomes a little less active and the O2 signals the ECU to lean it up a bit but not enough to throw a CEL?

Thanks gentlemen.

Drew Altemara

 

[Daedalus]

What I was always taught is in line with the SCC article's findings...that a richer burn creates less power, since the combustion gasses don't get as hot and thus expand less.

 

[RON98]

yes richer makes less power.

BUT its above a certain range.

between 10.5 and 12.5 ( maybe 11-12.5 somewhere in that range) there is not much change in power. I learned this at EFI U. The change in power is minimal. I can run the car on the dyno at 11 or 13 afr, it does not make any different in steady state tuning with out timing adjustment.

if the car they tested is a newer car, then the o2 sensor should be in good condition.