Seraph

I am considering changing my alternator, stearing and crank pully for lighter ones. Companies like Zerosports and Go-Fast-Bits have these and claim up to 9KW power increase at the wheel.

Please tell me your experience as my country does not have any 4wheel dynos and there is no way for me to verify this claim.

Also, any pitfalls lightening the pullys?

Thanks!

brickboy

I have seen dyno tests in a magazine of a lightened pulley set on a Honda Prelude, which gave an extra 6-7bhp if I remember. No experience with Subarus, though

ian/555

Try the US i-club,
as I have seen a few of them posting about doing this mod on there own car's

Pete Croney

Changing these may make a *very* slight improvement in torque but I would be amazed to any increase in top end BHP.

The steering and alternator wheels are so light anyway, I can't see the advatage. The crank pulley is a bit of a lump of iron, but its diameter is not really large enough to have any major effect.

If you were going to do anything about weight reduction of the engines moving parts, I would suggest a light weight flywheel as the first move.

NDT

Lighter pulleys might have some kind of flywheel effect - ie slightly quicker acceleration - but it's hard to see how they increase power?
Are they better aerodynamically or do they use a different profile where the belt sits for lower drag?

pat

Simply lightening a pulley will not gain any extra BHP, that's impossible. What it might do is to alter the transient nature of the engine, since there is lower mass, therefore lower inertia and hence it is easier to spool up quicker, much in the same way as a lighter flywheel will make the engine more responsive but it won't affect engine output.

What might make a difference, though, is if the design is altered in such a way as to either reduce frictional losses or by changing the pulley sizes such that the alternator or power steering pump are rotating slower in relation to the crank. Certainly at high RPM the power steering pump is literally just wasting energy....

What might also be interesting to do is to alter the design of the water pump such that it doesn't take 20 odd BHP to drive it at high speeds, and possibly cause cavitation. Electric water pumps must surely give better gains than light pulleys?

Cheers,

Pat.

Seraph

To clarify, the lighten pullys I refer to not only is light weight but also have smaller diameters.

Advise please.