MB-BOB

I floored my C320 on the entrance ramp to a freeway recently. The auto kicked down correctly and the car took off. The second to third gear shift was interesting... The tachometer says redline at 6000 rpm, but the transmission shifted at about 6200. Whoa!

No complaints from the car, but MB-BOB sweated that last 200 rpm (.2 secs) wondering when it was going to shift. I'm wondering if the tach is that accurate at max revs. Any ideas? Opinions? Observations?

pokerFACE

I think the true redline (per manual) is 6200rpm.. at least that's what I remember for my C240..

Many moons ago we also wondered if the TouchShift was set to 1, would it upshift automatically at redline or would it hit a revlimiter? Nobody has been brave enough to try yet (and I am NOT volunteering!! :p)

viper

Seeing as your engine suffered no ill-effects I would say that the accuracy of the tach is suspect. Or you are really lucky.

levelr123g

i wouldnt worry about it. that engine will spin another 1000 rpm most likely b4 any damage starts to occur. dont worry the computer will not let it reach that stage. the engineers would not design a redline so close to the actual breaking point of an engine.

MB-BOB

Ah, that would explain it!!! I'll check my manual myself. If it's truly 6200, I will rest easy.

And no, I'm not volunteering, either. LOL!

mctwin2kman

Mine will not kick in the rev limiter until 6200 RPM and the specs state 6200 RPM redline but my tach is red after 6000 so the tach looks to be just marked that way. Maybe for safety sake to make people shift lower with the standard. But mine seems fine and the rev limiter does kick in at the redline the specs state. Just the tach is marked lower. I was wondering that same thing an hour ago.

MB-BOB

I think your assessment is right on the money, mctwin2kman. (MB-BOB breathing easier).

Matt230K

Yes, it does automatically upshift. It will do it in every gear starting with the touchshift in 1. I have tried, just not with my car. It's a manual. But you can try it with yours. Even if it did hit the rev limiter, you're not causing any harm. That is there so you don't cause harm. It's just redline, except you're holding it a bit longer.

mctwin2kman

Yeah I hit the limiter twice today. The sand on the road caused me to accelerate harder than I had thought. That and the cold weather giving the intercooler a little more help seems to have added some power to my baby. Yeah it sucks having them Pirelli P-Zero's on there in the sand but my baby is hauling some serious but in the 20 degree weather.

jswedberg

Well, I have to say I have done it. I don't think that the fact that I have SpeedShift makes a difference.

If you put the transmission in "1", it will shifft at redline in every gear.

This is obviously most useful from a start, but if you are goofy enough to shift into "1" at speed (which I have NOT done - I did previously drive a manual, after all, and some things just aren't done!) it will not blow anything up. Supposedly.

In fact I am not sure how you can ever hit the rev limiter with an MB auto transmssion. The trannie is just TOO SMART.

Matt230K

I'm thinking that not all touchshift cars will upshift automatically. I was in a 2001 CLK430 last week, and as I was waiting to turn left out of the lot, I must have been leaning on the shifter, although it's hard to do without noticing, I tried it later. Anyway, somehow it was in 1 and I didn't notice. When I pulled out hard into traffic, I hit the rev limiter in 1st and started wiggling the back end in the salt on the road. But it didn't upshift. I don't know if I lifted too soon when I noticed it or what, but I had to shift it up myself.

revstriker

My car shifts at 6200 also.

I have also tried this by putting the shift in 1 from a stop and not shifting. The car shifts automatically at 6200.

If you pull the shift (downshift) and hold it there while you are driving, it will only shift down to the lowest possible gear for the speed of the car/engine. I use this on the highway all of the time to pass (when I want to have fun). I don't think it's possible to shift down to 1st if your traveling too fast.

zpeed

I did hit the Rev-limiter more than once when I just have a car. I use to have a Turbo car which has a longer gear and the tranny on my C240 are so short compare to my old car.

Outland

The stock valve springs are designed to float before the engine can wind to an RPM were it would suffer catastrophic damage...and the ECU would shut off the fuel or go into full retard long before then anyway.

Beat the snot out of it I say!

jswedberg

I do seem to recall previous transmissions (for instance our ML tranny) are not so smart - it WILL allow you to shift down too far.

Don't really want to try it, though.

FrankW

the tach on the dash shows 6k redline, but the real redline is at 6200 rpm. This is true for the C32 btw. Don't know if it applies to 320/240

FrankW

the speedshift will not allow you to downshift if the rpm and speed is too high for the gear. I've already tried it on the freeway. It will only downshift to the lowest "possible" gear.

viper

Oh sure. Lets try it on your car just to check.

Outland

Youre not going to hurt the motor....in most motors, the power will fall off dramatically at some point past the power peak...usually its a result of lack of breathing capacity- spinning it any faster does no good because the engine can't get air in and out fast enough to keep up with the RPM's. Often times the redline is near or slightly beyond that point. The reason you wind out past the power peak is so that when you shift to the next gear up, you "land" farther up the power band.

The redlines are far from where the damage occurs. A little beyond won't hurt. A motor accellerating under load is stronger than a motor reving in neutral - with no load on it..that can do some damage. The real damage occurs when you down shift from say 5th to 2nd, and wind 10K up on the motor...that will destroy stuff in a hurry.

jswedberg

(I meant the ML transmission)

jswedberg

I know for a fact that this is not true for all cars (but maybe all Mercedes). My Porsche 993 did not have the clearances, for instance. If you missed a downshift (thus circumventing the rev limiter) you could seriously damage the engine.

A Bad Thing.