WOT Shifting Issue at Drag Strip
 

I mentioned this in another thread, but I wanted to create a separate one since it seems to be a real issue based on another thread that popped up in the W211 forum. At first I thought it might be low fuel or trans adaptation related but am now having doubts.

Basically, the issue is that on several of my passes at the dragstrip power cut out for a a couple seconds near redline then suddenly came back on on the 1-2 and 2-3 upshifts. I was in S mode each time with the traction control fully turned off. It was very annoying to say the least and I'm sure the jerkiness was very noticeable from an onlookers perspective.

A lot of the W211 guys mention the same issue in the below thread, and suspect it may be tune related. Jerry from Eurocharged is looking into it and plans to report back to the group.

https://mbworld.org/forums/w211-amg/...nd-passes.html

Any thoughts or similar experiences out there?

Yes

Any idea what the cause may be?

I think it could be a combination of things, mthis stated in the other post about the adaptation, my opinion is that the car is simply over reving, if you power break the luanch it seems to do it much more, next time try launching without power breaking, the combination of additional power sticky track seem to make this happen, it happens almost everytime I go down the track in s mode

I've had it happen too. Does manual shifting help?

i think this is what happened to me once also... it startled me when it happened... happened at the top of 1 going into 2... it was a split second... and my friend actually got it on video... it happened just that one time and i only made about 2 more passes afterward and it didn't happen... i also probably made about 10 passes before it happened and it only happened that one time... traction off / S mode

i made a post about it a while back but i guess since it was buried in my old thread it didn't get much attention

https://mbworld.org/forums/c63-amg-w...ml#post5002479

http://www.youtube.com/watch?v=kyjwXUdIfwk happens at about the 31 second mark, you can see the car jerk

so far from all the people posting, it doesn't seem to be tune related... since there are a mix of tunes... and even a mix of motors... 63 and 55

I've had this happen to me as well when letting the car shift in S mode from 1-2...out of 100 or so passes, it's only happen twice that I can recall but was disconcerting nonetheless.

I know exactly what the problem is, my car used to do it all the time on the 2-3 shift. There are several things causing this.

....no be honest with me, are you spraying the car? I'm not saying it only happens when you spray but it ALWAYS happened to me when I sprayed and when I wasn't spraying it would happen about 50% of the time.

Take a look at this video, no nitrous with SC. Is this what your car is doing?

http://www.youtube.com/watch?v=RUl4Nnpk7Ko

It's not an over reving issue, I have raised my rev limiter an additional 300 rpm and lowered it 300 rpm lower than stock to verify, it's not a rev or rev limiter issue. i might also add that it happens in normal and dyno mode so it is not torque limiting related or ESP related.

no spray for me

I was not inferring that you or the OP was, I was just pointing out hat it happened close to 100% of the time when I was spraying. Does anyone know if this happens to Keiths car? Since I removed my nitrous sytem and have been running the blower it happens about half the time. It does not happen on the street(never happened even once on the street) and only happens on the drag strip.

At one point we thought it was related to differences in tires sizes I was running and the electronics "hiccupping" because yaw sensors or some other sensors might be kicking in and cutting power due to significant differences in circumferences of my front and rear tires but since it also happens in dyno mode we threw that theory out the window. We think the car is cutting power when the trans clutch packs slip, that's the only theory we can come up with.

i couldn't tell where it happened in your vid... but that was a pretty awesome run... and what the hell was up with that truck...

The issue with my car is way more pronounced than what the video shows. It literally feels like the rev limiter is hit and power fully cuts out for about 1 second, then suddenly comes back on and jerks you back.

Watch my head, it snaps forward when the power gets cut for a split second, it just looks like a hard shift but compare that shift to the other upshifts.

The S-10 pick-up was gutted, tubbed with a blown big block and a 250 shot. That was actually a slow pass for the truck, I lined up against him later that afternoon and he went almost a second quicker than the one shown in this vid on the spray.

My issue lasts longer than a split second. As one of the W211 guys described it, the effect from an onlooker perspective suggests I have a manual transmission and missed a gear.

How about these vids? I know exactly what you are describing. It is not rev limiter ralated. I tuned my ECU over a span of 600rpm in 100rpm incriments from 300rpm below stock readline to 300rpm above stock redline and it happened every time. Trust me it's not your revs, rev limiter or anything related.

http://www.youtube.com/watch?v=ZALHV5YqoQE

http://www.youtube.com/watch?v=6cNfOVk8PvE

http://www.youtube.com/watch?v=EMxIZGUf8-Y

Also of note, we have NEVER been able to duplicate it on a dyno. Liek I said it is a drag strip, drag tire/DR only issue, at least in my case.

The first and third videos show the event much better, but my power cutout still seems to last a bit longer.

maybe it is tune related :nix:

I also emailed Cory at Kleemann and one of his theories is that the issue stems from a tranny protective feature that intervenes when the tranny temperature is to high or too cold. My car definitely sat for a while waiting in the staging lanes on the last couple of runs where I experienced the issue, so maybe the tranny was still too cold at the time of runs.

Doesn't seem to be, as lots of people chiming in with a similar issue have tunes from all the popular vendors.

It is not temp related because it happens to mine regardless of if I was hot lapping or the car sat for 2 hrs between runs. It is tranny related, it could be a self protective measure but I would think it would happen more if 1-2 than in 2-3 becuase the torque in a 1-2 shift is more severe than in a 2-3 shift and mine only happened in the 2-3 shifts regularly, it has only happened maybe 3 times in my 1-2 shift. We think it is clutch pack related and we will be able to verify that in about a week once I get my new Weistec trans out on the drag strip.

Exactly, this has happened to me with Powerchip tune(2 versions), MHP tune (which could have just been a stolen PC tune) and a Weistec tune. It is not tune/tuner related. I know of a person with a Renntech tune that has the same problem.

I just really hope my car doesn't do this at the Airstrip event this Saturday! It shouldn't since the issue has only happened to me at the drag strip, never on a WOT roll-on run.

Sweet, you're going to be there at the Airstrip Attack? I will be there. It should not happen at the event, it is a rolling start and you should already be in 2nd gear. Are you running DR's or street tires at the event? I am going to experiment with both set-ups, but since I could spin my street tires up to over 100mph back in October and now I have added an additional 150+whp I think the DR's are going to be the way to go. I'm just not sure about the skinnies up front at 200mph :eek: