Hitting a "wall" MAF HZ dropps to zero

[realspeeddan]

2005 Corvette, Vortech supercharger.
GT500 Ford injectors, Boost-a-pump.


When the engine reaches ~4700 rpm at WOT the AFR jumps from 11.0 to 15.5 then leans out off the scale and the car feels like it is hitting fuel-cut rev limiter.

MAF Hz flat-lines (instead of climbing) for a fraction of a second and then drops to 0 Hz.

TPS stays at 88% (WOT) and my analog boost recorder shows boost continuing to climb. The car will rev past 6000 rpm at half throttle with no problem. Fuel pressure holds steady at 58 psi.

I tried a new MAF with the same results.



Datalog and tune file attached. What am I missing?

(Wideband is not connected to the datalogger so ignore those numbers)

[tpy2kws6]

I think it might be that you're reaching the limit of the MAF table. Perhaps one of the custom os's would help you. I'm sure one of the more experienced guys will chime in.

[realspeeddan]

With the new MAF in this datalog we were at about 11,300 hz when the problem started.

With the original MAF on some of the runs the problem started as low as 10,400hz.

I tuned a 2006 vortech/covette with a very similar combination of parts a few months ago that went to 12,600 Hz and did not have this problem. Is the 2005 computer that different?

[Bill@HPTuners]

Yup, that is what the maf patch is for under the OS tab

And yes the 2005 pcm is very different from the 2006.

[realspeeddan]

Yup, that is what the maf patch is for under the OS tab

And yes the 2005 pcm is very different from the 2006.

So I go to the OS tab and change the pulldown MAF Freq Patch from "unpatched" to "Patched" ?

Thanks for the help.

[vette_c6]

go to the OS in your file
u will have the maf patch
you can get it up to 15000
but if you are not going to get bigger maf
better to go to SD Mode
tune your car on maf and Run it SD on WOT

[5_Liter_Eater]

Make sure you do a "write entire" after you apply the patch.

[realspeeddan]

Patch fixed it. Hitting 12,600 Hz peak and responding normally now.

Thanks again.

Now the new challange is it is hitting 511 g/sec @ 5500+ rpm. Looks like I will have to
scale the tune.

[vette_c6]

2 days ago i was Trying to Tune a Car with 2 tuners ( they were teaching me )
the car was 05 c6 SD mode 2bar
it was running 11 pounds of post on P1SC
i've been asked to tune it on maf but the problem was the BLow-off valve was to close to the maf
so i couldnt because the reading wasnt accurate ,, it was really worth to see ho much post this patch will allow you to carry

but i hope you do it and send us a scan to see


you are having a knock on fram 42

i can see in your primary table that in this frame your AFR 10.9

your commanded AFR is 10.9 something like that ,, and your AFR in your Wideband is 10.9 your timing is not high its low ,, you r having knock ,, are you sure your wideband is working ? becasue even when you release the throttle your AFR is the same

[realspeeddan]

(Wideband is not connected to the datalogger so ignore those numbers)

See original post. Wideband was connected to the dyno on this pull.

This tune is nowhere near finished. I was just trying to make one pull to 6500 rpm to confirm if we had enough injector. Also, several limiters, codes and torque limits were raised or shut off in the process of trying to figure out why I was hitting a wall at 4700 rpm. Now I have to go back and reset those things.

[vette_c6]

sorry i didnt see that ,,
how many pound of boost are you running ?