Does resetting the stock ecu have any effect on a utec equipped cars performance. In other words. if i reset my computer will the car run different.
Its utec version 4.2 btw. i understand utec takes full control over 25% throttle and above a certain load point. And since fueling is maf dependent. If i increase the boost the car wouldnt run leaner assuming its still under the max map scale of 100 load site. Default settings are 18 ps at 100% i read. Enlighten a me please :)

Firstly, If you have open loop fueling enabled the utec will switch to its embeded fueling map. After 25% tps.

Boost timing and fuel does not get affect until 60% tps (default) plus other preprogrammed conditions in the parameters. If all conditions are met then the utec will take full control of everything.


If you hitting above 18 psi you may or may not run lean int he 100% column.

Say you maf voltage at 18 psi is 4.5 volts (100% load) and you add 5% of fuel in the 100 load columns. Then the applied(modified) voltage to the ECU will be 4.7 volts


Now say you run 20 psi at 4.7 volts (100% load column). With out modifying the fuel map you the applied(modifed) voltage to the ECU will be 4.9 volts.

You are still adding 5% fuel. in the same load sites. Now this doesnt mean u are necessarly runing lean, or rich its just relly unknown unless u get a wideband.


I tune for the 90% load column and the 100% load column is a back up/safety column just in case I hit more then 20 psi. I did this by simply changing my map scale to 22 psi.

Keep in mind you cant run the same timing at 18 and 20 psi theres a big difference and will prbably knock this is why i have te 100% column as a back up.

interesting.. so you are saying one should scale map so 100 percent load is more than the max boost you are planning to run. So changing the max boost is not gonna affect the afr as long as its not going over 100 percent load correct?

Now what about the stock ECU fuel-trims; I’ve always wondered this too?

When you reset the ECU, the short & long term fuel trims are also reset and re-learned by the ECU correct(?). This takes a short period of time to occur where the ECU is re-learning the trims which will eventually setting at the +/- 2% realm where the injectors were scaled from. So theoretically if you go out and get on the throttle following an ECU reset, and the ST/LT fuel trims are not yet re-learned, won’t the UTEC be changing the fueling in open-loop to the static values assigned in your fuel map which would be cutting or adding fuel incorrectly due to the inaccurate fuel trims not yet learned?

Or am I totally off? :confused:

from how i understand it. if you have version 4.2 or newer and enabled open loop fueling. the fueling is 100% standalone from the stock ecu once it enters open loop. It doesnt use the ecu's reading for reference and it have its own base fuel map in the utec. correct me if i'm wrong. so therefore the stock ecu fuel trims wont have any affect on how the car runs once it enters open loop but idle and part throttle conditions might be still affected because its controlled by the ecu.

from how i understand it. if you have version 4.2 or newer and enabled open loop fueling. the fueling is 100% standalone from the stock ecu once it enters open loop. It doesnt use the ecu's reading for reference and it have its own base fuel map in the utec. correct me if i'm wrong. so therefore the stock ecu fuel trims wont have any affect on how the car runs once it enters open loop but idle and part throttle conditions might be still affected because its controlled by the ecu.

Yep this is exactly how i understood it when i read the utec manual.