From first to second only. If you guys remember, i was having issues at the track with the car short shifting on 90% of my runs. Many mentioned it was because of the lack of traction which makes sense. However i have done some spirited driving and even without the traction light blinking it short shifts. 100 percent of the time. i even took traction control off and left it in 1st on manual mode without taping the shifter (someone recommended it) and it still shifts from 5600-5800. No matter what i do it will ALWAYS shift at that rpm. and yes i have traction. is it true a tune can fix this? Seems like its the only way to go. anybody have it set above 6000?

 

well, I was about to ask if you had a tune, and I see you haven't...it's the only way to fix it...bump her to 6200...

 

I agree with Doc. This was one of the first things I noticed after the tune.

 

Yes my tune bumps mine to 6250 and I've been able to show it with a datalog.

 

I read an article a year or more ago that stated the max rpm for our engines is 6400, but I cant find the article to confirm it. Members here seem to set the rpm limit at 6200-6300 rpm.
I just found this interesting comparo of a c32 to a c55 with engine specs......c32 max rpm was 6,220 for 1 minute. Interesting.

This article also mentioned that the c55 has a "manual" mode added to the transmission electronics that allows it to hold whatever gear you select. This would be a nice add on feature to the Xfire!

Mercedes-Benz Specification Site C32 / C55 comparison - Marcus Fitzhugh

Cheers,
KrzyFast

 

hmmm. Thanks. just another reason to get the tune... id say most of the time shaved off the quarter mile with a tune has to come from this feature. no doubt there will be extra power there but if you still shifted at 5800 the gains wouldnt be as significant.

 

Well, not quite so fast there... mine's tuned and it shifts early too. I still don't know why. So there's no guarantee that a tune will fix it. Now, of course, there is one guarantee, without a tune, it will always shift at 5600-5800.

 

Well, Tommy, if the boys at US41 would have paid attn to you when you asked them to check your tune, it would be shifting correctly today.....that is why your times aren't where they need to be....there is a flaw in that tune...it took several passes down the track to get the roadster where we wanted it....and that is how I will tune the coupe as soon as I am ready....

 

Well, I think I'm on the slow-as-she-goes plan for a while.

Once get the SRT-6 paid for, I'll have an extra $500 a month to spend on go-fast parts. I think when that happens, I'll drop my car off in Detroit and tell Rob to call me when it's "just right".

 

I emailed InMotion about having my rev limited (increased) and apparently the tuner cannot adjust this, they said the best option is to get an authorized dealer e.g. Mercedes to reflash/recode the transmission controller.

By the way I already have the custom tune from them. So i don't know if this is them being honest or just trying to brush me off.

 

Well, I find that interesting since before my LET tune it shifted at 5800, after the tune, it shifts at 6200...I think I am in trouble as to finding a good tuner....maybe I need to put out a BOLO on Wayne...he did me well on the roadster

 

Anyone looked at a Dyno curve to see what you get by shifting at 6000 - 6200 vs 5600-5800? If it's falling off after 5800, you don't gain anything by upping the shift point.

 

really...........

 

Not true. Check out my dyno chart:
Message - CrossfireForum.org Gallery

The HP is still climbing. Torque is slowly tapering off, but it is gradual at that point. Sure it's not huge gains between 5800 and 6200, but it is more time that you're "in the zone" making max power and lots of torque.

 

LET's tunes are from Powerchip...they were going to do a full custom dyno tune on my car over 2 days for $1300...seemed expensive but i may have come out of it with an 11 second SRT and the smile on my face would have outweighed the hole in my wallet.

 

I like to tune the car at the track with track numbers...dyno can get you close, but I am just old school, and like to do the track hands on kind of thing...hopefully we can find a way to do that...but, unless someone can produce that, I am screwed...I don't want a canned tune on the coupe...

 

OK, if I had one I would probably know the answer but reading through this thread made me curious.

Stock does it shift by 5800 in every shift? As in 1-2, 2-3, 3-4, etc? I ask because if every single shift point is set below 6000 stock then how did Chrysler get away with marketing the HP numbers as:

330 bhp @ 6100 rpm


If the engine never sees 6100RPM one would think they couldnt advertise that as the peak HP?

 

How does any of the car manufacturer get by with it? They do as they want....I have seen more than 6200 out of the roadster, and I have seen 6000 out of the stock coupe...when you do a tune all the parameters are looked at, but not all can be changed...I believe with more boost, comes more hp, comes quicker response, which create the peak rev...it doesn't sustain that rpm, but bounces off of it...just like a speed limiter will breifly hit 160, but sustain 158....can you say you went 160, even for a moment...yes...but you can't sustain it...same goes for rpms...but in the car's case, it is shifting at that point, so it is still accellerating, still gaining hp....and I also believe all cars aren't the same...some do better than others...

 

Not possible for what I said to not be true. It was a question and an "IF" statement. I had no idea what the dyno chart looked like, that's why I was asking.

 

When it shifts at 5800, what do the RPM's drop to?
Is the automatic a 6 speed?

A related, but different observation/question;
Mine is a manual. I'm surprised there isn't a taller gear in 6th - more like an overdrive. I spend a lot of time on the highway in 6h, at something over 4000 RMP's quite often. On the street, wouldn't the car benefit from a taller 6th gear? Is it a mod an experienced tranny guy could make?