[the ambush]

Originally Posted by spongebobnopants

I called Cobb and they said it was normal.

normal it was designed to be like that ??
then why not design it correctly

[XPT Tuning]

The car is actually pulling a lot of timing in that area, I notice it most on Sport Sharp. I logged a constant "tip-in" timing pull in this area which is completely un-necessary. I plan on fixing this in my map release.

[spongebobnopants]

Not to sound stupid here, but doesn't timing go down when boost goes up? ESP at WOT. Did you happen to log the knock sensor?

[XPT Tuning]

Originally Posted by spongebobnopants

Not to sound stupid here, but doesn't timing go down when boost goes up? ESP at WOT. Did you happen to log the knock sensor?

The red line in the graph is boost. As you can see the boost never even got to 0psi. Knock sensor was not logged as my definitions are limited at this time.

[KJ1225]

I have the AP with Perrin 91 octane Stage 1 map and I have the "stumble" at that rpm range also, I'm puzzled.

[XPT Tuning]

Originally Posted by KJ1225

I have the AP with Perrin 91 octane Stage 1 map and I have the "stumble" at that rpm range also, I'm puzzled.

Do you have RACE Tuner? If so I have a pretty good idea of how to resolve the issue. I'm not sure that you can edit the Perrin map but My suggestion involves the logic change between Ignition Timing maps A/C and B/D.

[KJ1225]

Race Tuner? is that the software that you can download off Cobb's site?

[sponaugle]

Originally Posted by KJ1225

I have the AP with Perrin 91 octane Stage 1 map and I have the "stumble" at that rpm range also, I'm puzzled.

Both Jeff (Perrin) and I have been working on this 'stumble' for some time. It is slight on the stage 1/2 cars, but much more noticable on some stage 4 (larger injector) cars. We think we know the source of the problem (and it isn't just related to AVCS or timing), but we need to test a few things to confirm. Once I know what the fix is, I'll let you guys know. It might involve a few maps that are not yet exposed, but that is being worked on.

Cheers,

Jeff

[spongebobnopants]

Originally Posted by sponaugle

Both Jeff (Perrin) and I have been working on this 'stumble' for some time. It is slight on the stage 1/2 cars, but much more noticable on some stage 4 (larger injector) cars. We think we know the source of the problem (and it isn't just related to AVCS or timing), but we need to test a few things to confirm. Once I know what the fix is, I'll let you guys know. It might involve a few maps that are not yet exposed, but that is being worked on.

Cheers,

Jeff

IIRC, I really did not notice this at all on stage 1, but as soon as I went stage two it was evident. My guess has been that there is a safety parameter that is kicking in. FWIW, I do remember reading something that S and SI would be dissabled until the car is warm but I have never seen that nor have I had the car in extreme cold. The issue is more noticable when the car has not had ample time to warm up.

I have been tempted to load stage 1 SW back on my car and see if its still there with the DP, but I'm not sure how safe that is.

[XPT Tuning]

I'm still hunting down the root problem here. It has surfaced again even with a clean Stage 1 tune. I am now pinpointing it down towards here. I'll give it a shot shortly and see. Engine Load Compensation.

[Colombo]

I've played around trying to see where the problem is and it only shows up in I and S modes. S# isn't noticeable.

I'm running Cobb 1.01 stage1 93oct map.

[k38s]

Yea I had the 26-2700 stumble with my stock map. Had it with my Cobb stage 1 and 2 maps and I got it with my protune Other than that my car runs smooth as silk and just keeps on pulling. It stumbles hardest when it is cold and on partial throttle. Less at other times but it is almost always there if I am looking for it.

[XPT Tuning]

I was able to remove the stumble yesterday with a combination of modifications. I am putting the Engine Load compensation back into the map to determine if it was part of the issue.

[Colombo]

Well done!

[XPT Tuning]

I added the engine load compensation back and the stumble reappeared. It appears mostly related to the engine load compensation. The rest was in the timing map at low RPM and the Exhaust Cam mapping at low rpm when moving from a stop or under 0psi.