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E12, E28, E34, E39, E60General discussion and technical help for all year 5 series cars.
Underdrive pulleys do exactly that...they underdrive the crank pulley. It is like using the smallest sprocket between the pedals of a ten speed bike. Easier to turn, therefore freeing up horsepower.
The trade off... all other things being equal... is that now you are driving the belt slower per each revolution of the pulley, so you need to use slightly bigger pulleys on the waterpump and alternator, or you will underdrive them at idle and risk not charging and overheating Unless you live in a climate that constantly stresses the alternator or cooling system, I don't think there is a down side
Umnitza now provides a mechanic to install all parts ordered right in the box! It's their new "Total customer service program" that will eliminate all the haters and keep incompetents from breaking **** and blaming the vendor! When you are all set simply call INS and they will pick him up free of charge.
Your Ride: `00 540i6 Alpine White, `96 740iL Aspen Silber
that's what i was saying they make them for the m50 engine and others they put into the e36 but they never put the m30 in any other cars but the 5 and 7. these are not looked at as much in the tuner market so they don't make as much on the production scale in terms of performance parts.