Understanding GM ecu operation?

[OKGMC4]

Anyone that is familiar with tuning may know...

Is a cold air intake worth the effort? I know in theory cold air is more dense, makes more power, blah blah...but when you google it you come up with conflicting answers. There seems to be an assumed general rule on several threads of a loss of 1% power for an increase of 11 degrees temp at inlet air temp (not counting humidity, air pressure, etc.) But that means on a 300 hp engine you only lose 12 hp when air temp goes up 44 degrees, which seems like a small amount. So...

1.Does the engine actually lose more than that when the MAF registers higher temps? Does the engine pull timing at that point at higher IATs?

I have an air filter right above the engine in a custom box I built and I drove around last night with my OBDII scanner hooked up and watched it. At 55 degrees, when the engine warmed up I read 80-85 IAT moving, and up to 100 degrees sitting still. That would mean I could be losing that 12 or so hp, but you can't feel it on the inaccurate butt dyno. I wondered if I unplugged the MAF so the ecm had no clue what the IAT was and forced speed density mode, would I sense a difference. I did that and drove some more. Absolutely no difference anywhere could be felt. OK, so if it runs the same why do I even need a MAF? I thought it was supposed to help the engine adjust and run right but at the same time I know many people get mafless tunes, so why? I have also read that cold air intakes don't work without a custom tune because the ecm sees the cooler air and adjusts to attain the same air fuel ratio it had before the intake. So...

3. Is it better to run with a MAF or without?
4. Is it true that even something as simple as an air intake could require adjustment?

Also, in the 30 minutes I drove with no MAF plugged in, I recieved no check engine light. Shouldn't that have set off an alarm?

Sorry so long, you just get a ton of conflicting info on the net and it seems like someone who has done any tuning with an LS would know this. I would love to get HPTuners and tune my 5.3, but I don't know jack about the VE charts, or short or long term fuel trims, etc, and I'm afraid to blow things up.

[68GMCCustom]

My guess is you were not to a point that it would make a huge difference. Had the IAT been another 50* higher you probably would have.

Not sure how to answer (not familiar with SD tunes or MAF for that matter - just beginning)....so I took a screen shot of one of the stock files from my TrailBlazerSS...as you can see the higher the temp goes...the more timing the ecm pulls.

[BR3W CITY]

Originally Posted by OKGMC4

Anyone that is familiar with tuning may know...


3. Is it better to run with a MAF or without?

IMO on anything besides a higher power forced induction setup, there isn't much of a reason to run without it (speed density tune). When you start to go past the ability of the MAF and make multiple atmospheres, the SD tune is needed. It allows you to develop the "most" power under the circumstances under which it was tuned....this means that tuning a car for the most power in WI might yield drastically different results in southern AL where the temp and density is going to be drastically different, because you've removed the piece of equipment that used to make the adjusments. Just unplugging the MAF on your regular non-sd tune won't improve anything.
4. Is it true that even something as simple as an air intake could require adjustment?


Theoretically if you were building vehicles to just dyno for max power, yes it could need a change, but realistically that isn't really the case. The changes from a cai are well within the ability of the MAF and PCM to compensate with fuel and timing. [/COLOR]

Also, in the 30 minutes I drove with no MAF plugged in, I recieved no check engine light. Shouldn't that have set off an alarm?

My CEL light didn't work when I first did my swap....you never get a CEL if the light doesn't work

meow in italic red

[Wasted Income]

I don't run ANYTHING except open loop, speed density on my swaps. Boost, or N/A.

First thing I do it take the MAF and throw it in the trash, lol.