MAF Frq vs. G/sec at WOT

[PRAY]

I have been breaking in my new motor and trying to get idle, low rpm surging and WOT under control. What I am noticing now at WOT on the street is that my MAF G/S don't match my Frq/Hz at WOT. An example being my MAF F/H says 9,400 but my G/S in the scale says 485 but the log says only 422. The other extreme example of this is at 8958hz it is reading 489gs in the lof when the scale reads 351. Can someone explain what is going on. I don't have my WB hooked up right now to get the actual AFR for both readings. Maybe posting a screen shot could help explain what I am talking about. At normal driving and idle it matches.

[swingtan]

Which gm/Sec PID are you looking at?

Can you post the current tune?

[PRAY]

Maffreq2. It is an E67 in an 07' CTS-V. I will try to post the tune in the morning. I am running an LS7 MAF card as well. It is giving me fits. Car runs great in CLSD. Once I turn the MAF back on here comes the bucking. I have tried everything in all of the stickies. I had the injector timing advanced to match the cam and things were not that bad. Then I put it back to stock and the fuel leveled out with the maf on it just about rattles your teeth out. So, in the morning I am going back to SD with the injector timing stock to see what happens.

[swingtan]

I can think of a couple of things....

[list=1][*]Charge temp blending may be altering the calculated value. Maybe.... maybe not. [*]Given things seem right in SD mode, you may be getting reverberation in the intake pipe. Again, a long shot....
[list]

You could lave the MAF in place and just set it to fail in the tune, then see if the values match up. You can still record MAFFREQ2 when in SD mode, if you set the MAF to fail at a very low frequency.

Simon.

[joecar]

Post log file.

[PRAY]

Brett.tun 427MAF14.efi Here is the current MAF tune and the log. The WOT pull is around the 16 minute mark.

[PRAY]

I only fail the MAF and leave it in place when I go SD. I also turn off DFCO and CFCO to ensure I get the VVE table correct. So I ran it that way this morning and all my LTFT's were within +/- 3. Most under that. Car drove almost like stock for a car with 21* of overlap. It was wonderful. I am going to keep it in SD and turn DFCO/CFCO back on to see if that effects anything. It is doesn't, then I will turn the MAF back on and see what happens. Those are the only two things I change on the tune going from SD to MAF.

Just so the tune makes sense. I dropped in a LS3 427 and ported the heads, intake, headers with stock cat back and did a custom CAI with the LS7 MAF. The cam is a LSL/HUC 243/251 113+4 21* of overlap. MN12 car with 3.73's.

[PRAY]

427SD9.efi So this is a WOT in SD. If I look at it over all the car went beast mode. The MAFFRQ and G/S still don't match up but the AppCylDMA stayed high along with the MAFFRQ and the G/S maxes out at 511 instead of like the last on with the MAF where all that data noses over at 6,400 or so. The pull is at 8:26:25 in the log. It actually spun for a sec in 3rd on the launch and traction control kicked in which it has never done. It was colder this morning but I will have to go back and look at by how much.

Adding back in the DFCO/CFCO it didn't seem to work in SD mode. Does it only work with the MAF turned on? Car still drove great but was a little leaner. Still idling at 0 to -1 but was leaner at cruise by about 2-4. I hate how you have to manipulate this VVE table now. Minor corrections are about impossible if you have rich and lean conditions that span only a couple hundred rpm. The car seems to hate 5th gear for some reason. I think I have it narrowed down to my coast down spark table. Once timing drops out at light throttle or backing off the throttle to around 27* and below the buck fest happens. I think if I can get that worked out I will be good. All the other gears are money. Maybe I can mess with the Idle Air in 5th. I just know that as soon as I hook the MAF back up I am going to want to blow the car up. This MAF set up did the same thing in my cammed TBSS. When I went back to the stock 85mm MAF it drove like a dream. That car was an Auto with a much smaller cam but was comparative to this new set up as per overlap to cubes.

[statesman]

I don't think your MAF is working properly. Your Freq/Hz numbers are all over the place.

[PRAY]

I didn't either but I swapped MAF sensors and all of the wiring around thinking I messed something up with the swap. Everything is correct. The only thing I can think is that I need a different air filter with a velocity stack or perhaps I can find some honey comb to put in there to act as a flow straightener. It definitely does not act right. I can't find it in the tune either.