I read this article in this month's Chevy High Performance. It's a good read for those novice tuners or for those just starting out. I hope there's more where this came from.

http://chevyhiperformance.com/techarticles/0508ch_obd/

Learn it, know it, live it.

 

Thanks!

 

i would do the HP tuners if i was not so afrade of screwing up the pcm.
drilling the carb, changing the jets, any thing to make it work faster or dump more fuel, upgrade the distributer, setting the timing, increase spark, no problem.
now that it is all done by a computer it is almost beyond me,
everything i know how to do is just not needed any more.

 

awesome... i'll put that to some use.

one question...

under General Fuel System Adjustment,
"For example, if your average LTrim is eight, this means the PCM is adding 8 percent more fuel. So try scaling the entire MAF table by 1.08..."

where did they get this 1.08 number? whats its significance?

 

Wish I could answer that, but I haven't got into my fuel trim settings yet.

Have to find a good day I can spend logging and driving around.

 

That would simply mean the baseline is 1.00 and 8 percent (.08) increase would be 1.08. If you multiply any number by 1.08 the result is an 8 percent increase.

 

If you can tune a carb, then tuning efi shouldn't be all that hard for you. I grew up and I am still, playing with carbs and when I read about how its done with efi, its all the same. Its generally the same process, just instead of screw drivers and wrenches, its done with the stroke of the keyboard.

 

oh.. duh... awesome.. thanks!

i just need to go buy a card so i can hook the laptop upto my truck.

 

This is awesome for the rookies. That includes me!!

But I have one question for the professionals. If you are seeing a +8 on your LT trims (meaning that you are adding fuel because of a lean condition), and then go to your MAF settings and adjust it by 1.08 would'nt that make your LT trims increase since you are adding more air, thus making it leaner??? I am confused on this one

 

If you multiply the MAF readings by 1.08, you're not adding more air, your just telling the computer its seeing more air than it thinks it is. Your re-calibrating the MAF signal vs. its output frequency. Hence the lean condition. Does that make sense. Why on earth the computer won't adjust is freakin' stupid but thats the way it goes.

For example lets say you have a factory tune, and you put a nice phat cam in the engine. Cool! But the factory tune and MAF have been designed to work for a certain amount of air and fuel. With the cam you're adding more air so you can burn more fuel. The MAF hasn't been calibrated to work with the higher airflow rates its seeing. So you use the O2 sensors output signal (L trims), and adjust the MAF accordingly. This in turn fattens up the mixture and tunes the engine.

This is just my take on it. This is so similar to carbs its almost scary.