Woodstoc

I have a question I haven't been able to find an answer to yet. If you load a custom tune, would the ECM modify it based upon the sensors in the car. If so, why would a custom tune be used to begin with? It would seem that the ECM would always, over time, modify the fuel trims, regardless of minor changes to the car such as headers and CAI for optimum condition.

Unless the custom tune locks this capability out? I have the InTune 93 Octane loaded for about 4 months prior to my headers install with cats, I did this weekend, and am wondering whether a custom tune will round the car out, or will the ECM adjust itself. The car runs fine, with a lot more power, and no CEL yet, but I've only put about 10 miles on it so far.

Thanks, and a Happy Holiday weekend to my fellow vette lovers!

Freak3150

The computer will still adjust, but a tune is a good idea. The tune is the foundation, its always going to try to hit those numbers, so the closer you are to that, the less the computer has to adjust (depending on mods it may not be able to cope). Some things will only go one way, like timing for instance, it will drop below what the tune is calling for, due to knock retard, but it won't go up. So a tune can have raised timing that the stock tune will never see in a given situation.

Obviously this is a very simplistic explanation, and in the real world it's more complicated, but hopefully this will give you the basic idea behind a tune.

jsucraig

Freak3150,
I love your AVATAR!

Freak3150

Lol, thanks. I use mobile a lot so I forget it's there.

jsucraig

I sent you a PM.

Mike's LS3

The ECM only adjusts in closed loop (limited to + or - 25%), part throttle cruising. When the ECM goes into open loop, WOT, the power enrichment values are programmed in the tune. Adding headers will most likely lean out your A/F ratio throughout the rpm range. A custom tune will benefit the entire rpm range by rescaling the MAF to bring fuel trims at closed loop to desired levels and adjust PE values for proper A/F ratio in open loop.

Woodstoc

That makes sense Mike, thank you. A limited window and scale. I'll be contacting Monte Carlo SS about a custom tune to finish this install off.

Mike's LS3

Lew will do a nice custom Diablew tune for you

jim2092

Exactly.