Vardar

Hello guys, I took my C43 for a highway ride for the first time today. Making the story short; rpm was 3000 at 80 mph? Isn't it little high? Eventhough it is a very quiet engine, I could kinda hear it screaming. I wanted your input on this please. If you drive that speed would you please let me know? Mercedes Dealer ADVISER told me that it was kinda high, i shoud have stopped by to get it checked (typical).

But when I stop and drive I can see and feel that it shifts 5 gears. I will sleep better tonight if this 80mph at 3000rpm is normal. Cause when I hit the pedal little more, it still flies without downshifting.
Thank you

NitrogenBalance

Yes, that is normal. Or at least my car spins the same at 80mph, seems to me that my car is smack dab on 3000rpm at 80mph.

So according to my car your fine, if not we have the same problem. LOL

However, not too long ago I had my car up to 140mph and it didn't seem to be screaming or maxxed out. It actually achieved the speed pretty easy. So maybe 5th is a big ol' gear as 140mph is almost twice that of 80mph and the rpms didn't climb to much to achieve that speed. I've heard they will hit 168 with the V max limiter shut off, ECU mods can do this.

I think your ok, on a side note, my 99' W202 kompressor was right at 3000rpm while cruising at 80mph.

e320newbie

i love when she screams hehe, scares the fu ck out of people haha

tran2112

It's hard to hear anything when you're driving at the speed of sound!

Vardar

come on guys! Excep nitro, no one is answering this serious. Is it the same with your vehicles (3000rpm at 80mph?) It has to be stock C43 though.

thank you

blume

my 4x4 truck pulling a trailer with jeep on board spins 2600 @ 80mph if that helps... if not, sorry.

NitrogenBalance

It's normal bro, don't worry at all. It's actually nice cause at that RPM your about half way through the power so you've got some decent excelleration from 80mph. 90% of the cars on the road you wouldn't notice if you floored them at 80mph. The C43 actually pulls away from 80 pretty well.

P.S.

I'm having the kleemann ECU done at some point before spring(been sayin this all winter) and that should put my limiter around 168mph. Plan on getting a video shot of a high speed run around 160 if I can get enough room.

bootsy

My C320 runs the same at 80mph w/plenty of pull. I think it's normal. -Raleigh

e harmon

Short answer: yes.

Long answer:

Engine RPM at a given speed is a function of gearing, and other than slight changes in wheel diameter, I can't think of any popular modifications that affect this. Intake, exhaust, new plug wires, braking hardware, even forced induction or a limited slip differential--none of these would affect the RPM an engine turns at 80mph. Therefore, even if you hear from someone who has modified their car, there is a good chance the comparison is still valid, as long as it is in fact an identical model.

Aside from a false tachometer reading, here are two likely ways in which your car would be turning a higher than normal RPM at 80mph: the diameter of the tires is smaller than it should be, or the car's transmission is not successfully shifting into its highest gear. I'm assuming that you would be able to verify the correct rolling diameter based on tire specs, so here is an idea regarding the second scenario.

A simple experiment. (1) Drive 80 mph with the transmission in "D". Note engine rpm. (2) Drive 80 mph with the transmission in "4". Note engine rpm. (3) If engine RPM was lower in step 1 than in step 2, your car is probably succesfully shifting into 5th gear, and you are probably okay.

Enjoy the ride.

Regards,

e harmon

Vardar

RPM goes to 3500 at 4th gear @80mph, and at overdrive it is at 3000rpm, So I guess with you guys' help, I will be sleeping better......

Thank you kindly!

StapleGun

Yep...that sounds about right

Vardar

Wow thats a really wide gear!, I noted that when I hit the gas @ 80mph, C43 flies without downshifting. This is extraordinary to me....




[QUOTE=So maybe 5th is a big ol' gear as 140mph is almost twice that of 80mph and the rpms didn't climb to much to achieve that speed. [/QUOTE]