05CL55

Anybody else notice theat MBUSA has a new horsepower rating for the SLK55???

Wonder what they're up to???

CP1

Here's what the site says:

Serious rush. With more than 360 horsepower pumping from its V-8 engine and a 7-speed automatic transmission, this roadster provides serious sports car thrills in true AMG style.
AMG-built 5.5L SOHC 24-valve V8 engine - 355 hp @ 5,750 rpm

silk32

hmm weird. Also have you noticed that the C55 has the same engine (if i'm not mistaken) as the slk55 and the c55 produced more hp?

might seem a little dumb but i wonder if it has anything to do with the computer? or if you could swap a c55 computer to the slk55 and get a boost?

Shark

Perhaps it might have to do with minor differences in the exhaust system.

HarryH

I think the difference is that in Europe the horsepower rating is calculated differently than here in the U.S. In Europe the horsepower rating is around 360 while here in the U.S. the rating is 355. But the output is the same, just different methods of measurement. Sort of like liters and gallons.

Yellow R1

Correct. The SLK's exhaust is slightly more restrictive (due to its shorter wheelbase - its not as "straight" as its larger AMG bretheren).

The Hp rating difference is not due to Europe having a different measuring system (or all Hp ratings would be different between the US & Europe on all cars AND there would also be a difference in the other 5.5L US based AMG cars vs thier Euro AMG cousins - it would not be limited only to the SLK55 - the Hp delta would be present in the other AMG cars).

-Matt

steve-p

The USA uses SAE Net Horsepower, Europe uses DIN (70020) horsepower. They are different measuring systems with a difference factor of 1.0139. More here:

http://neptune.spacebears.com/opine/horsepwr.html

At lower numbers, they are very similar. By the time you get to 360, the difference is starting to show. The UK generally uses BHP which is the same as SAE Net. Hence we also have 360bhp, but the magazines have been getting confused recently and have been publishing a mixture of 355 and 360 figures.

silk32

interesting. Thanks for the explanation. Learn something new every day.

fredfromny

I think that you are right-they are tuned differently. Because they both share the same platform I don't think it is the engine bay fitment.The length of the exhaust has little to do with this because a shorter exhaust is actually less restrictive.
I think that because the car is in a different segment than the roadster the emissions or EPA mileage standards may be less restrictive in the larger car. This also occurs in the Audi A4 3.2 engine which is rated at 255HP while the TT is only rated at 250 HP.
Swapped ECU's should be the same part number, though.

Yellow R1

No, its the exhaust (length has nothing to do with it, its how restrictive the system is). AMG uses the same ECU (and A/F mapping) for all their N/A 5.5L powerplants. I read this exhaust to power output for the SLK55 about 6 months ago - I forget which article (ie why was it a slightly down on Hp).
Trust me, I drive a mid 11 sec car every day. Nobody is going to notice a miniscule 7 Hp (at the flywheel) drop in power. Its too small to notice & besides, the SLK55 weighs less than the N/A AMG sedans which offsets this small drop in power. Its just plain insignificant.

See ya,
-Matt