CorkSports Mazda 2 Dyno

[Gravity]

Agreed the pulley was an excellent part. I noticed a definite difference in butt dyne with the pulley installed. Very noticeable difference in throttle response and clutch engagement.

Forgive my scepticism but my first pulley was installed at a shop thats been around in this city longer than i've been alive, and the second (obviously redesigned) pulley was installed by my dealer (who are normally exceptionally on the ball about things and very likely torque parts to service manual spec) I would have my doubts that over torquing was the primary failure mode given that both my parts failed in precisely the same way. Same engine code, same noise, same trigger wheel separation. It stretches my credibility somewhat that two qualified shops would bugger the torque spec badly enough to cause failure.

 

[AN7]

Agreed the pulley was an excellent part. I noticed a definite difference in butt dyne with the pulley installed. Very noticeable difference in throttle response and clutch engagement.

I believe that was more like a placebo effect the difference that you noticed. Consider that you took off from the pulley less than a kilo but on the other end you have more that 10kg\s of rotating mass(fly-clutch-plate ++)

plus that, http://en.wikipedia.org/wiki/Harmonic_balancer

 

[xyrth]

If I can see a picture of a damaged one, or even one that shows the back side of the pulley (assumed failure point) I can tell you what is going on.

Over torquing is incredibly common on crank pulleys - most people use breaker bars and go gorilla tight. And dealership mechanics are there to do the job fast, not always right. That said, a single bolt going over the torque spec shouldn't flex a pulley to failure.

I'd also like to add that 1-2 pounds should make a difference, but is unlikely to be more than 1-2 hp and have any gains felt. I happen to like the dampening effect stock pulleys on all the accessories, so I tend to leave the OEM piece unless I'm going to extremes.