Truth About Pulleys

[Deep]

Its a long read, but interesting. http://www.dinanbmw.com/html/danger_of_power_pulleys.htm


In a nutshell, often pulleys are not balanced correctly or sized appropriately for the motor. This will eventually lead to bearing failure and consequent engine death or overheating/charging problems.

[Sifu]

Good post, I should have known that there was a lil' product placement at the end.

[Deep]

Fuck, I'm glad somebody enjoyed it. :roll:

[Sifu]

Naw, for real! I always thought that lighter pulleys were a good choice to use since lightweight equals less resistence. I'll send this out to all my friends who claim that they make "mad" power from their pulleys. I'm wondering what the BEST way to address pulleys are now?

[fatredcircle]

then again, every aftermarket product that helps you increase hp on ur engine or even suspension stuff increases your performance, but decreases ur durability of ur engine/car

thats why they rebuild engines and chassis in all the racing leagues

[smokey8890]

thanx deep! I was really going to get them pulleys for my ride. but 2-3 more hp ain't worth my engine.

[ajnoe3]

I was thinking about ordering custom pulleys for my car, but now I know the truth. My engine is allready unreliable, no need to make it worse!
Thanks!

[1owner]

Just remember that it is a compromise that engineers settle on. Are you running just one race or season vs. many years of service. You can run them but be aware of the downside.

[DaksGT]

Thats bullshit, depending on how stout the motor is, look how many b series motors run pulleys and no problems? Look how many zz blocks also run pulleys and no problems, me being one of them.

[NiXX]

Although many 'claim' lightweight pulleys release more HP with less rotational mass, it really doesn't. It has been dyno proven with many different cars that you won't gain HP.
Lightweight pulleys WILL make your car rev up a little faster due to less mass, but it will also make your revs fall faster too. It also gives your engine a better 'bling' factor, but otherwise it really doesn't do much.

[Flashmn]

Well, getting an ultra-light flywheel would be even worse. but yeah, pulleys are mostly for looks, trying to get ~2hp more out of your engine with pulleys is just ridiculous even in a race 2hp wont even be noticed.

[gzus13]

Actually, DaksGT, it's not bullsh*t. I've heard the same thing from more than one source, including Sport Compact Car Magazine, which is probably the most respected mag in the industry. Especially with forced induction, pulleys can be a idea. Take it from a mechanical engineer and a lot of people that know a lot more than you do.

[Ratko]

just watch out you BMW owners, a lightened flywheel and pully could blow your engine

[Artsi]

In case we're building up a street car that sees a fair share of track work, it pays off to alter pulley relationships.

If car in question is tuned to reach noticeably higher rpm's than what it did in stock trim, we should alter pulley diameters. Water pumps for example will start to cavitate at high rpm's, nor is altenator really that keen on running extended periods at very high rpm's. Waterpump cavitation can/will lead into overheating. If not complete overheating, at least chances of having localised boiling in cylinder head is greatly increased. This can easily lead into head gasket giving in at some particular corner - usually close to exhaust valves.
Most of the time people will not stop to think why gasket blew up. They just replace it and keep on going.

I've kept my crank pulley stock, just made w-pump and altenator pulleys 25% to 30% larger in circumfence.
This will neatly cancel out lower rpm level performance of said accessories if car has a higher ratio rear diff installed. That makes engine to run at higher rpm's at all times when comparing over to stock setup.



Stated changes are to enhance modified engine long livety - not power output.

-Artsi