I believe you're correct. During the dyno run there was considerable
conversation with those present, and my tuner quickly showed me the
HP Tuner screen showing the LTFT deviations. They probably were +.
I'm trying to remember the color code to help - purple?
The REAL POINT is that screen removal dictates a retune. However,the
initial pull showed a severe lean condition ?(A/F 15.8/1 and leaner) as we
increased RPM. Don't ask me to comment on corrective strokes
to the tables, especially using HP Tuners. I was familiar enough with LS1 Edit on my blown C5, but am quite ignorant of LS2 program changes - and there are a few. I did find out that the LS2 program is very sensitive to ignition timing changes - different program schemes as
compared to LS1. My tune is quite conservative given knock sensor
sensitvity setting and 93 octane fuel.

 

spin, you are i are saying the same thing, i am not doubting the maf does read the increase in airflow. the big question is does it read or in your words "prediction" correctly? obviously it doesn't, that is why the st/ltft are off and requires a rewritte in software / tune, if you removed the screen. wouldn't you agree? isn't this the same reason when you removed screen on your c5 you have to use the Z06 MAF table for the driveability? since the maf can't read (my word) / predict (your word) correctly with the previous software (stock tune). thanks

 

how easy is it to take the ls2 maf screen off? can it be put back? curious to see if any one has done a before and after data logging on just taking out the screen? thanks

 

I found this link on MAF screen removal, not sure what to think, but I probably won't be messing with it.


http://www.gmtips.com/3rd-degree/dox...maf-screen.htm

 

you can take it out but its not going back in..Lol...

 

I'll buy that.

 

true, getting it out (from the backside) is easy, putting it back aint. you can, however, experiment with your own 'custom screen(s)' if you want. you can 'fashion' a screen(s) to assist in creating (or attempting too) a more laminair airflow through the maf. you can add screen(s) to the intake duct (maf connection end).

 

This makes sense to me

 

Fritz Kayl (Katech Co-Founder, C5R, Lemans etc.) says descreening the MAF on an LS1/LS6 increases airflow and horsepower on a dyno. You can verify this by viewing Katech's GEN III Seminar tapes, here's a link to purchase.......or you can take my word
->http://www.katechengines.com/street_...tail.php?id=37

 

This is what you base your opinion on? Why did they remove it for the C5 Z06? You keep dodging that one.

 

Running in speed density soley uses the VE table. It reverts to the VE table when the MAF fails.

 

Only in closed loop the LTFT's go lean, the PCM dumps that percentage more fuel which causes a rich condition at WOT.

 

It does and that is why the Z06 MAF table doesnt match the stock one in the C5. The catch here is that the changes are very small and no where near something you can feel.

It doesnt predict so much as quantify that you agree this much air is assigned to this MAF frequency. When tuning you can scale the PCM differently to get LTFT's in line. It can be done by the VE table with all else turned off, scale the MAF higher to richen the LTFT's or lower the values in the injector flow rate. It is a marriage of making the different tables go together to create a a/f performance that works. You can tell the car it has bigger injectors and it dumps less while telling the MAF it is seeing more air. Both accomplish the same thing.

When VE tuning, you remove the MAF by causing it to fail the frequency test and then tune fueling by the VE table. When you eventually switch back on the MAF it then gets scaled to get back to stoic. In this type of tune the injector flow rate is set to command a 1.13 or 13:1 A/F at WOT so that becomes a constant too. You set the VE table then that is a constant and last is the MAF which is specific to your car and its mods. If people only tuned this way then they could perfectly tune in the aftermarket Granitelli MAF's, screenless MAF's, or bigger ones of a completely different design such as Lingenfelter's new 100mm unit.

Like most mods, simple changes have been clasified too fast by "professionals" as a waste of money or a mistake because "GM didnt engineer it that way". The truth is that anything you do affects volumetric efficiency and therefore throws off a tune. Like I always said, hole or no hole, I can tune any throttle body. You simply must take into account the increased airflow on that table at that load and RPM.

And for the record just because GM didnt design the LS2 with a different cam doesnt make that mod a bad one. Can you tune???

 

i do agree that all manufactures will use interchangeable parts when they build cars. i just wish they had grab the maf from c5z or c6z when building the c6, if would have put this debate about screen or screenless to rest.

 

I am not the engineer that decided the screen was needed, you should ask him or her why it is there.

 

OK but in closed loop the LTFT table entires are not constant for every RPM, MAP, and IAT. So which one is used at WOT? On an 06 I thought that fuel delivery was based on the commanded ARF which was dependent on the RPM.

 

And the same engineer removed it on the C5 Z06....so I guess when labor is involved on the high performance model, it gets removed. It being on the LS2 is because they didnt do the labor to remove it. It was cheaper to keep it.....like the ex.

 

Dayum good question and a dayum good answer: whatever it locks at when you floor it. If it locks positive, it dumps fuel so when tuning you want non-positive LTFT's. If it lock at zero or negative it dumps the A/F commanded amount.

 

Alright, sounds reasonable. That's the way it was when tuning a pre-OBDII LT1.

That being the case it does make sense to LTFT calibrate the MAF, screen or no screen, such that a "0" LTFT is had prior to going into WOT. Would you agree?

Rob

 

That is the general premise for basic tunes. Zero LTFT's then use a wideband for WOT to tune the PE mode. In a speed density tune you log the VE table by wideband O2 error percent and get the table in line with commanded values then you put the MAF back in and get it back to zero or as close as you can get. -3 to 0 is most common.