Underdrive pulleys
Senior Member
Joined: Sep 2006
Posts: 329
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e55
The FI pulleys are technically not underdrive pulleys, they are overboost pulleys. the make pulley groove that runs all the accessories is stock diameter and the extra pulley groove that runs the supercharger belt is "overdriven" to help speed up the supercharger speed (aka more boost). There is also a stock diameter crank pulley made by AMS for the E55 cars for alot less. Each has their advantage & disadvantage just matters what you want.
For the NA 55s, the only option you have basically is stock diameter AMS crank pulley, Ev*sport accessory system pulleys, and headers (Renntech is one for $4500, and supposedly AMS is coming out with a much more affordable set soon). The X-pipe is also a great mod for the SLK55 (very similar to the X-pipe on the old W210 E55s, b/c both systems do not merge so the X-pipe helps w/ good scavenging effects). Anything else won't really net you much gain (like air filters, really only for sound).
You could do fan delete as well although its not very common for the AMG guys, but bmw guys do it all the time (lower thermostat + lower fan switch + fan removal = a few nice ponies and alot freer revving engine).
For the NA 55s, the only option you have basically is stock diameter AMS crank pulley, Ev*sport accessory system pulleys, and headers (Renntech is one for $4500, and supposedly AMS is coming out with a much more affordable set soon). The X-pipe is also a great mod for the SLK55 (very similar to the X-pipe on the old W210 E55s, b/c both systems do not merge so the X-pipe helps w/ good scavenging effects). Anything else won't really net you much gain (like air filters, really only for sound).
You could do fan delete as well although its not very common for the AMG guys, but bmw guys do it all the time (lower thermostat + lower fan switch + fan removal = a few nice ponies and alot freer revving engine).
Last edited by E55 PWR; Nov 22, 2007 at 11:09 PM.
