Just got myself a new alloy pulley very nice very light but its smaller so I will need to buy shorter belts (which I have already got new standard ones: ) to fit it. My first question is can I just take half the circumference of the original and the circumference of the new one and take that off the length of the belt? Make sence

Also I’ve read a couple of threads where they are saying that the alloy pulley can course damage to the crank as there's no harmonics dampener (is that the rubber bit built into the original pulley) built into it? is this true??

Help?

 

help

 

ANY BODY OUT THERE?

 

The pulley supplier will probably have the part number for the right belts if they know their business.
Why not compare how much over size your existing belts are and try to get a set, comparably shorter. I guess if you do not want to guess you could use a bit of string to get the overall internal circumference.

I have run alloy under driven pulleys for five, perhaps six years on various Subarus two of which have been in my ownership for five or six years and thousands of miles, all without any engine problems.
When the opportunity presents itself I machine the flywheel to around 8Kg so that takes a bit of weight out of the opposite end so that will reduce the torsional strain. I have heard the theory about harmonics and torsional strain etc but as I have seen no firm evidence I conclude it is just another one of these Scooby Myths that pervades this and other boards.
I have never been able to detect any performance benefit but on the basis that every little bit counts and they look nice, I havve been happy fitting under driven lightweight pulleys.

 

If it's a cheap pulley off ebay then you may come across problems.. Pulleys running out and squeaky belts ,

Chris

 

A harmonic (or torsional vibration damper correctly) may be needed on an EJ to prevent damage or it may be just for NVH, I don't know, if its here as a TVD its possible that deleting it could cause crank failure, but this could be only seen under particluar load regimes (usually low engine speed high load), no one here can say it won't as none will have tested over all the likley uses, although most users on here are unlilley to use low speed that often! Lighteneing the flywheel actually increase the likelyhood of a need for a TVD, not reduces it as the extra mass reduces the peak G's seen within the crank. On the flip side Prodrive use them on Group N engines....

A lightweight pulley does not increase horsepower, its reduced inertia means that the engine will accelerate faster which may be seen as a slight bhp increase on a dynamic test.

An under drive pulley does incraese BHP due to reducing the load from the Alternator and PAS (and AC when on) but the actual gain is quite small as most of the time the load (power drawn) from both is controlled and so will just be a higher torque at a lower speed and therefore the same power consumption.

Simon

 

Ok thanks for your input will have to do some more studying!

will give my input once the alloy pulley is on tho.......

 

hiya i have ran mine for 2 years now with no issues

we have a skimmed 7.5kg flywheel as well.......

 

It's on and working! After trying a few belts to get the right size one......


Does look good tho......

maybe better power wise a few other things to sort out first!