Car ran a good time but I have a odd flat spot

[69lt1bird]

I took the car to the strip yesterday, ran on DR's for the first time. Great time, my best ET and MPH. The log is a 11.67 @ 114.92 run, I also ran a 11.70 @ 116.

Now the issue, I have a flat spot in the RPM's, the attached logs show it, the car has great 1/8 mph (avg 97 mph) but it is not gaining enough up top and it only goes through the traps at about 5700-5800 rpm's.

My MAF is jagged, always has been. It seems to be the same issue I felt and heard on a dyno run last year. Frame 214 is the start of the issue, if the rpm's progressed on the upward trend, I would shift a bit sooner and run third gear longer and get the rpm's up higher.

Any suggestions?

[Cantalope Kid]

Copy of tune and config. used showing wideband data?

[69lt1bird]

You would think I would know better. Here are the files.

I made 8 passes and they all have the same issue in the same spot. I am leaning more towards perhaps a torque converter issue than anything in the tune but who knows.

Thanks

[ElecTech]

Are you running an open element air filter real close to the MAF and TB? I usually see MAF signals like that with open filter setups without any intake piping, like the Street & Performance MAF set-ups.


The "flat spot" looks to me like its not really flat. If you look at it in full screen with the the graph zoomed in it has an "arc" to it (in all gears and the RPM reflects it. To me it looks like a flair of some sort and my guess would be TQ converter flair. I know your TCI is supposed to be a 3500 but it looks to me like its not really holding until about 5500 rpm.

EDIT: didn't read your second post very well, but looks like I agree with the converter.

[69lt1bird]

The intake system is pretty simple.

6"x9" 4" flange K & N filter in the wheelwell. I have a closeout panel to keep the engine heat from getting to it.

That is connect to 12" long 4" dia. aluminum tube followed by the MAF, another 12" x 4" tube to a smooth 90* elbow to the 90mm TB.

Very smooth, very simple design. I have tried another MAF and it is the same. The air should be straightened out pretty good by the time it hits the MAF but who knows.

[69lt1bird]

Elec Tech, good call.

I logged some data last night and found what is happening.

The torque converter clutch is functioning properly. It has a flare at that RPM range that is causing the issue. I did some research and made some changes with HP Tuners to see if I can clean that up. The log showed the trans pressure to be lower in second gear than in 1 and 3 and a table in HP Tuners matched the difference in readings. I adjusted the pressure and tweaked the force motor table.
I will try to drive again tonight and see what happens.