JYO

If I set cruise at 80 MPH my tach reads 2800 RPM

at 70 MPH it reads 2500.

This seems too high compared to a 3.5L Honda Odyssey V6 (2200 and 2000 RPM respectiveley) or to my E320 V6. Almost seems like it needs an extra gear for highway driving. I have checked it on "comfort" and "sport" modes.

Is this just the way the transmission is tuned to operate?

Nachtsturm

I want to say I am at around 2400 at 80. I'll pay attention when I'm on the highway next trip.

ashutt

Read mine today at 2510 at 80 mph so 2500 looks like about the right number to be at.

JYO

at 80MPH I'm at 2800.

2500 at 70MPH.

we have same engine but I guess transmission is different. I still think mine runs higher than it should at 80MPH. I guess as long as there is no overheating I think the engine itself can withstand the revs. But it makes makes me a little reluctant to take a long distance trip.

neilbo75

Last weekend I did a cross-country drive on one of France's autoroutes. The legal speed limit is 130 km = 81 mph. I up it a bit (no more - too many robots!) to 134 = 83 mph and set cruise control. The tach dozes at about 2650.

MarcusF

The fifth gear ratio in a W208 CLK55 is the same as a CLK430. The CLK55 has a 2.82 final drive, versus the 430's 2.87. That's less than a 2% difference, so this is very close to what you should see.

JYO

Thanks Marcus. Would the 55 engine in the W209 be any different. Does the transmission play much of a part in this? When did the AMG Speedshift start?

MarcusF

The W209 CLK55 has higher compression, but the differences between the two engines are minor.

If I understand the question, the transmission is the largest deciding factor in determining engine speed at road speed.

All AMG CLKs were equipped with SpeedShift. If you’re asking when SpeedShift itself was initially released, I don’t know.

JYO

Or when did the 7 sp auto come out? only on the CLK63's? i wonder what it revs at?

from all the replies i'd say my engine is working harder at 70-80 mph than most AMGs, however most replies have been from W208s ( I still love that body style!).

MarcusF

Sorry, for some reason, I thought you had a W208. The final drive in a W209 CLK55 is 3.06, not 2.82 (W208 CLK55)

The CLK63 has a different final ratio and completely different transmission ratios. I think you’re interested in the overall ratios. The overall ratios in the 63 are (1) 11.60, (2) 7.58, (3) 5.09, (4) 3.63, (5) 2.65, (6) 2.17, and (7) 1.93.

The overall ratios on a W209 CLK55 are (1) 10.98 (2) 6.70, (3) 4.31, (4) 3.06, and (5) 2.54

In a W208 CLK55, they are (1) 10.12 (2) 6.17, (3) 3.98, (4) 2.82, and (5) 2.34

Per my notes, the CLK63 is loafing at 2260 RPM at 80 MPH. The W208 CLK55 should be at 2670. Due to the W209 gearing (which may have been changed for the weight), it has an 8.5% penalty. According to my calculator (I don't have any RPM/speed notes from W209 AMG tests), that puts the W209 CLK55 RPM at 2898. Making your tach a little low. If you had gearing that brought the revs down to 2500, you’d pay a cost in acceleration.

Pauljay

Hi MarcusF.

A quick question for you.

I've got a 430 CLK with a 55 N/A AMG engine conversion running 430 gearing. At 3000 revs the car sits at 96 mph in 5th.

I was thinking of doing the W210 320 diff conversion with the final gearing of 3.07. What would that do for my acceleration and highway cruising figures?

I haven't done it because I think the gearing may be too low giving a much higher consumption of fuel.

What's your input please.

MarcusF

I think

1. If traction isn’t an issue, the car will accelerate faster.
2. If you’ve currently got a stock CLK430 final ratio, and at 96 MPH the engine is turning at 3,000 RPM, with a 3.07 it will be turning 3209 PRM. Or, with a 3.07 at 3,000 RPM the car will be traveling 84 MPH, rather than 90.
3. You will burn more gas. Although compared to what you’ve probably already spent . . . .

What kind of headers are you running?

JYO

wow. good stuff Marcus.

I do run 2800 at 80MPH so that's pretty close to what you calculated. I'll check it again and see if it might be closer to your figure.

Not that I want to lose acceleration but I wouldn't mind if the Comfort mode on transmission would allow it to rev less at 80MPH when cruising on a long trip. It would make for quieter drive and better fuel econ.

phoung

about 2450, i always thought are 5th gear was a lil short

neilbo75

Good stuff as always. Wow, I didn't realise the 209s were geared that differently. Did that penalize gas mileage as measured by the EPA or other testers? The gearing and the extra weight would make me think so.

Pauljay

Thanks Marcus!

You sure know your stuff.

I'm running stock headers at the moment. Being a right hand drive car space is limited on the left (facing the engine) I'm told. Still trying to find some one to make some.

JYO

I measured 3100 at 90MPH today.

CharlyE500

Reviving a old thread. Just got a W208 CLK55 and when cruising 60MPH rpm is about 2100 and 70MPH about 2400/2500
Is this normal ? My E55 RPM is way lower.... i think 70MPH is about 2100 or 2200RPM but CLK55 is about 200/300RPM higher. Is this normal ?