[flash]

There have been a couple of failures of the Dayco Idler pulley on the driver side at the top. This can be indicated by it making noise.



This is a pulley designed to last 100,000 miles. The cause of the failure is over-tensioning of the belt.



You do not need to tighten the belt as far as you might think. The amount of wrap on the Supercharger is such that not that much tension is needed. Tighten it only until it no longer "tings" against the metal Belt Cover (make sure the Belt Cover is as high as it will go too).



In case you did not know, the sound you hear just over 6k rpm is NOT the belt slipping. That is the air reaching maximum velocity going through the inlet of the Supercharger. That is your indicator to SHIFT. You will not make any more power beyond that point, so there is no point in revving beyond that.

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[Lear35A]

It's easy to understand the inclination to over tighten this belt. The stock belt is tightened to 9.5 on the P9201 tool plus 1 turn. This is really, really tight!

Is it possible that over tightening would cause little bits of rubber to come off the belt as well as damaging the pulley? I have a lot of these little bits all over the left side of the engine. Or would that be an indication of under tightening?

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[flash]

if you have undertightening, you will see it on the boost gauge as a drop in boost.



that sounds more like misalignment. look closely at the belt, and the pulleys, making sure that you have the belt centered on the supercharger, and not all the way in one direction or the other. there should be one open groove on each side. also, did you use the correct spacer on the solo idler pulley? there were two in the kit, because there are two different castings of the unit it bolts into. if you use the wrong one, the belt will rub on the shoulder.

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[Sho968]

I am also glad you're talking about this.



I just finished installation of my kit and breaking in the Rotorex.

My belt cover is all the way to the top, but I hear ping when I decelerate ... so that means I have to tighten some more, right?

My belt is already adjusted to 3/8" deflection at bottom with *MY* thumb push, but that can be subjective.

Do you have any recommendation as to how much static clearance I should see between the top of belt and lower surface of belt cover?

That would give me an extra assurance that I will not be adjusting the belt unnnecessarily and too tight.



Thanks,

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[flash]

we have found that it is very easy to over-tighten the belt and result in burning out a pulley bearing.



bend the belt guard up away from the belt a bit more, taking care not to break it. best to remove it to do this. there is plenty of clearance between it and the hood. it's only there to keep your tie or whatever from getting caught up in there.

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[ds968]

[quote name='flash' timestamp='1373980002' post='145689']. it's only there to keep your tie or whatever from getting caught up in there.[/quote]

Good point... 'cause no self respecting mechanic would work on the car without wearing a suit and tie . ( much like operators of tree chipping machinery, looking sharp is essential, those guys also wear ties :-) ) One needs to be more concerned about the

" whatever " getting caught up in there...so never work on the car while naked. :-) :-)

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[flash]

lol - you would be stunned to see some of the stupid crap i see happen. putting something there to keep things out of harms way just made sense. i did my "due diligence" to prevent mishaps. other designers don't generally pay attention to those kinds of details though. i'm just really anal.

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[Sho968]

Thanks for your reply, guys.



Actually, I was very aware of my lanyard (my work badge), and I do make sure to take it off (I commute with my 968) from my neck when I tinker with the engine before I drive away home.



And I appreciate Flash's anal-ness, now that I know everything running fine, I finally placed the CARB sticker last night, and noticed the sticker is color-coded with the factory emssion placards.

How's that for being anal!? We are generally anal here in the aircraft industry, but sometimes I feel like we could use a little help from Porsche crowd.

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[SanderSchippers]

Hi there guys, my idler pulley has failed. Any idea what the part number is? Would be nice if I could get a similar item in the Netherlands (or Europe), but not counting on it.

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[flash]

Dayco 89095

 

you have to remove .035" from the face with the dots (not the face with the embossed printing)

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[SanderSchippers]

Will do, thanks flash!

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[flash]

correct tension is the key here.  it should be LOOSER than stock, by about 15%.  basically it needs to be as loose as it can be without slipping.  that screech at just over 6k is NOT the belt slipping.

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[MLB]

So, i was just able to get the new tesioner in place and did not crank additional tension on it. But ive never heard any belt squeak-age with my new installation

Should I go through the exercise of loosening that tensioner now just until I hear the belt slip and then tighten it from there?

My reading of the instruction manual was that Belt was going to gradually require more and more tightening with the tensioner as it got broke in and stretched a little bit.

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[flash]

it will stretch a little bit, but not much.  if you had to struggle to get the tensioner in there, it's too tight

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