MAF descreen tuning?

I have sorted through the numerous post on this, and other forums, and I can't find the answer I'm looking for.

I descreened my LS2. The upside is more airflow , but the downsides are many. Now I can hear knock, and the engine is running way too rich. :doh: I thought I had bought a bad tank of gas, but that doesn't seem to be the issue.

Timing is set pretty mild right now, but it's still not running well.

This morning I put the screen back in, and my mileage went up about 3MPG, and the knocking is reduced. :banghead:

I know I need to adjust the MAF tuning to make this work.

Now my question:

How much, and what direction should I change the values in the MAF "Airflow vs. Freq Low", and "Airflow vs. Freq High" to make the descreened MAF work correctly again. :shrug:

Thanks. :usa:

Sorry, I forgot to mention in my post that I have replaced the stock cam with an MTI C2 Custom. I'm still working out the fine tuning for the cam, but I do want the extra airflow that descreening can provide. I'm planning on a cold air intake soon, so the screen will be my biggest obstruction for airflow to the intake.

BTW...Thanks for the excellent resource for all this information!

:worship:

How do you knwo its rich? More air will make it leaners and generally tahts what happends when you descreen it, it may change the airflow patters.

When I had it dynoed it was running @ 10.8 AFR at the tailpipe, and I could smell the fuel in the shop. The timing was also pulled down to 8* according to the scanning module.

The car made almost 50 HP below stock, too.

That was WOT? or it was reading that before the run as well?

You have to first figure if this is really a MAF problem,
or a "my mods mussed up its mind and it's trimming
most bogusly" problem.

This afternoon I will download the C6 Factory tune back into the car, with the idle speed adjusted higher to smooth the idle.

The reading was 10.8 WOT. 10.3 less than WOT. The tail pipe has quite a bit of carbon on it now too, so I know it

Curretly I have the engine back to stock, with the exception of the cam. I'll do some data logging on my way home tonight to see if there is anything else going on. I'll post up the results of the dyno, and config this weekend.

My experience with these new MAFs is that you should leave the screen. Many people are making 700 + RWHP and not touching the MAF. The screens help straighten the airflow as approaches the wire. Taking the screens out lets "unmetered" air enter the motor which is why its probably running like crap.

I have had at least three LS2 cars come in to our shop in which the customers de-screened there MAFs and had bad drivability issues. Replacing the MAF solved the problems.