What is the difference between the R171 SLK55 v R172 SLK55. The R171 has 355hp and the R172 has 415hp. Are they the same engine or are the completely different?

 

Both are really great brides, with much different platform indeed,,

A) 04-11 "R171 SLK55"
N/A [M113], (5,439 cc) = bore stroke (98mm × 90.5mm), [11.0:2] Compression Ratio, >> 510Nm/{355hp}

B) 12-16 "R172 SLK55"
N/A [M152], (5,461 cc) = bore stroke (97mm × 92mm), [12.6:1] Compression Ratio, >> 540Nm/{415hp}

-;-ZAYED-;-

 

I’ve got a 171 and drove a 172 recently. The 172 is better; it’s better damped, the gear box, although not an MCT, is super quick. It’s luxurious,, accomplished, comfortable and has a somewhat muted burble. Apparently they’re better on fuel too, but this R172 averaged 10 mpg on the test drive. Yikes.

So it’s a much better car than the R171. But the R171 has more soul. There’s no stop start. The gearbox feels like it’s straining on a leash and wants to take off. It fizzes, shakes, rumbles and goes like stink, probably not as fast as the R172 but it sounds faster. The R171 is more analogue.

For a daily driven car, the R172 would be my choice. For an occasional car I’d go with the R171.

 

171 has the M113 5.4

172 has the new M152. Same displacement, more power, less aftermarket support.

Cars are very different experiences.