My curiousity on this subject is very high and I thought I would post to find out the real facts. My brother has an '05 STi with a piggyback. He got it tuned about a month ago. In the beginning, it ran fine, A/F ration perfect. It used to run rich before his tune. Recently, his car has started to run rich again and he said he has noticed some power loss and the car choking itself out due to excess fuel. Evidently, he contacted the tuner and they said that with a piggyback, eventually the tune will disappear if you drive hard and keep the RPMs high. So, basically, he is losing his tune due to the piggyback and utilizing the power he gained from it.

Is this true? If so, what can he do to alleviate the problem?

Also, my EVO is completely stock and I was thinking about moddifying it. If I do stuff to it and get it tuned with a flash, do EVOs do this as well, lose the tune? I know there is a difference between a piggyback and flash, but I want to know if this will happen to my EVO as well if I get a flash when I get it tuned.

Thank you for any help or advice you can give me.

 

Unless the piggyback lost the settings, it shouldn't lose the tune.

If you get the stock EVO ECU tuned, it will not loose the tune.

weather/altitude changes etc.. can have some effect but if the tune was made right it should be a non issue.

 

The only similar thing I've seen with the Evo ECU is the AFR changing due excessive fuel trims. This can be compensated for with injector scaling and MAF correction and, in most cases, the effect these trims have on open loop fueling is minimal.

There is also more to a tune than the AFR. Other settings modified by the tune will not fluctuate like the AFR will.

 

Bad gas? High elevation?
In other words find out what's changed since the tune/piggyback install...

 

the thing is, nothing has changed at all

he has not put any new mods or anything on his STi

 

something changed...weather, boost leaks, any number of things.

 

So, basically, the tune should not be lost just because he has a piggyback and running the car hard? It has to be another problem?

 

correct

 

Thank you so much. I appreciate all the help. I guess the next step is to take it back to the tuner for diagnostic work.

 

Thank you so much. I appreciate all the help. I guess the next step is to take it back to the tuner for diagnostic work.

 

you're welcome and good luck

 

Do EVOs have piggybacks like the STi or do EVO owners only flash the ECU?

 

you can run a piggy back on top of the stock ECU but it's pointless since the stock ECU can be flashed to take advantage of full control of the fuel/timing etc..

 

Thank you so much again.