amurray

I have a '02 C240 w/ ~200k miles, AT. I have recently noticed that at highway speeds (>50MPH) the RPMs seems higher than normal & under normal acceleration on highway once I take my foot off the gas the car slows down quickly (10 MPH in a couple seconds). Here are some RPMs/speeds
60 MPH - 2700 RPM
70 MPH - 3000 RPM
80 MPH - 3300 RPM

I have had it looked at by the dealership twice & they said it shifts fine. Are these typical numbers for this car? I am always in the 'D' don't use the manual shifting mode.

Thanks in advance
Andy

HellsAngel

if you want i can test my rpms at those speeds, but i have a c 320..
wait for someone with a 240 to confirm

BigBodyBenzC240

I have an 02 C240 but I have a few mods done so I think my results will vary from yours. I can check but it wont be until tonight or tomorrow for the results.

LILBENZ230

My C230K is about 1000rpm per 25mph. So at 75mph cruise it's turning 3,000rpm.

amurray

I'd appreciate it if you both would test & let me know. I did another road test & had it at about 60MPH in the manual 4 gear & then shifted it to 'D' & it did shift fine. It just feels like it is running at higher RPMs & does not coast at all.

I am not much of a car guy, just trying to either accept the dealer's suggestion that its fine or get more info on what to have checked.

Thanks
Andy

LILBENZ230

I think your car is fine. My car is at 2,000rpm in 5th at 50mph and 3,000rpm in 5th at 75mph and 4,000rpm in 5th at 100mph

amurray

Matt,

Thanks for the quick reply. Maybe I just never noticed it before. I am glad its not a transmission problem, that's for sure.

Andy

Mu9enx

Mine is weird, at 80, depending on things, I've had it at 3200rpm, and at other times, at 3000 flat. But I think, from my experience, it always changes when I reset the throttle. After a week or so, it would adapt to my driving style.

LILBENZ230

Speed @ RPMs should not be affected by throttle reset. I can see it changing if you change rim sizes, but otherwise it should be consistent.

Mu9enx

That's what I thought too. But this occurred when I had my Brabus reps on. It would change whenever I did a throttle reset, no lie. It was something that kept on bugging me too. Maybe my tach is f cking up.

holycaoAMG

I think our engines rev noticably high at highway speeds compaired to others. I know Hondas [with 5 speed autos] cruising ~80mph barely gets up to 3k rpm like ours. This obviously isnt a problem for newer MB's anymore as they are now using the 7G tranny.

DarthBudice

At 70MPH in 5th, my engine spins right at 3,000 RPM.
I've noticed my fuel usage starts to noticeably increase above 3,000 RPM,
but boy is she happy to purr that fast (and above) for hours and hours!

I make frequent 300 mile interstate trips (1 way) and have never been more
pleased with a vehicle's driving performance. Electronics OTOH, not so much.

Happy driving...

AdidasC230

I have a 2.5L M272 6 with a 6 speed manual and at 75 Im doing 2800Rpms 80 3K

victorb623

Thats normal. I have a 2002 c240 2.6L v6 automatic. same speed at the rpm you stated

glocati

Agreed. Exactly what my 04 C240 pulls RPM wise at those speeds.

Glyn M Ruck

Confirm correct & slows down because the torque converter is locked up so you are running against compression - no coasting. This is correct.

Mu - you might be seeing this because of your glycol problem & the tranny misbehaving.

amurray

Thanks to all for the replies. I am glad to see these are normal numbers. Not sure why after 7 years I am just noticing it, but I'll chalk that up to an operator issue.

Glyn, can you explain more why the torque converter would be the explanation for no coasting. I am not a car guy, so this maybe basic knowledge for others.


Andy

victorb623

dont forget to change the fluid and filter in the tranny =)

Glyn M Ruck

Sure - Old auto boxes had the engine coupled to the auto gearbox via a torque converter (think American - GM Trimatic or Chrysler Torqueflight). These fluid flywheels allowed large amounts of slip for smoothness & the GBs had crude hydraulic control. When you lifted off the gas the car virtually freewheeled so you had little or no braking effect from the engine because there was no direct lock up between it & the transmission. This set up was smooth (slush box) but hopelessly inefficient with huge power loss (energy loss) through the transmission mainly due to TC slip.

Modern electronically controlled Auto boxes like your car has, have a set of lock up clutches on the torque converter which are locked up from just after pull away until just before you stop. So the engine is direct coupled to the transmission similar to a manual car. This is comparatively efficient as there is no longer any slip via the torque converter.

So when you lift off the throttle you are running against full engine compression just like a manual car and will slow down due the braking effect of the engine.

Hope I have explained clearly enough.

amurray

Thanks Glyn that makes sense.

Andy

slammer111

My 2003 C230 gets 3000 @ 120km/h, which is exactly 70kph. Sounds normal.

What they should've done imo is gotten rid of that stupid S/W switch and made 1st gear S the same ratio as our current 1st gear W. I think I've used that 1S gear maybe 20 times since I bought the car, to impress friends in a parking lot. That gear is so short it's useless.

LILBENZ230

So on the pre-facelift cars the S/W switch changed ratios? On my car it is C/S and C makes it start off in 2nd and shift earlier.

slammer111

^ Yeah, for 2002-2003 it's Summer/Winter, and for 2004+ it's Sport/Comfort. We have the exact same button with different lettering. 1st gear is so useless on this car. They could've made our current 2nd gears the real 1st gear, so that our 5th gear would have much lower RPM on the highway.

Of course this can be easily done with a rear differential mod, but the cost would outweigh the savings unless you drove on highways regularly.

Does anybody here use S regularly in their W203?

LILBENZ230

Okay I knew that the pre-2004 cars had S/W instead of S/C, but I didn't know the function was different. I always use S mode in my C230, starting off in 1st and shifting through all 5 gears. At WOT, 1st gear seems short. Or am I misunderstanding this?

slammer111

No, the functions are identical. They just changed the lettering on the button.

Shorter gear = higher revs at a given speed. Therefore, the 1st gear is stupidly shortfor this car.

I've never understood why car manufacturers didn't just spread out the gear ratios more to improve fuel efficiency. Most cars cruise at much higher RPMs than needed. Nobody needs 3000rpm if you're not passing anyone; that's what downshifting is for. They finally got it right with 7G-Tronic.