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Rotrex belt slip at high rpm

 
Old 03-31-2019, 12:55 PM
  #21  
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Twibs,

I'm wicked confused. You say this...

Originally Posted by Twibs415 View Post
the spm supercharger pulley is not the same alignment with two more ribs out front. Itís actually one rib on each end of the stock pulley. This was why I had to space the auto tensioner in closer to the bracket
But also this...

Originally Posted by Twibs415 View Post
So I had a giant clusterfuck with 949racing and bhj but luckily bhj is semi local to me and I was able to get the right crankpully and overlay to run the 6 rib setup. It took some work but I got it done.

i replaced the crappy small bearing manual tensioner pulley for a Hyundai Elantra timing belt idler.

Then i spaced in the auto timing belt pulley a few mm closer to the bracket.

Found my 6 rib belt for my new blower pulley and hit the track. No belt dust and the belt lasted the entire day no problem.
I can't find spm supercharger pulleys in the google machine. Did you replace the pulley on the Rotrex? Mine already has a six rib pulley. What I need is an overlay for the crank pulley. If your Rotrex came with a four-rib pulley that lined up with the stock crank pulley, how were you able to use a new six-rib supercharger pulley that had an extra rib on each end without spacing it out at least one rib's thickness from the Rotrex?

You used an overlay for your crank pulley. Doesn't that mean you should have used a larger pulley for the Rotrex as well? I thought 80mm with the stock crank pulley would take the Rotrex to its max rpm of 120,000, so a larger overlay would overspin the Rotrex when you get up into the higher engine rpms.

I did check out your IG page. Beautiful car.

Thanks,
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Old 03-31-2019, 02:38 PM
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The spm pulley is itís own beast with its own issues. And things with it werenít as advertised. I would disregard anything you read about it because I donít think there were even a handful of them made.

Iirc all the rotrex pulleys come in 6-8 rib. There no issues with this side of the equation. Figure out what crank pulley diameter youíll be running and then give kraftwerks a call and They can set you up.
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Old 04-01-2019, 05:55 AM
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BTW poormxdad , the 75mm rotrex pulley will put the c30-74 just under 120k RPM at 7000rpm with the stock miata BP pulley, not the 80mm one.
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Old 04-04-2019, 04:53 PM
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Originally Posted by lbatalha View Post
BTW, the 75mm rotrex pulley will put the c30-74 just under 120k RPM at 7000rpm with the stock miata BP pulley, not the 80mm one.
Irregardfull, that doesn't mean he's not overspinning the Rotrex. I should be at about 10psi with the OEM crank pulley and 80mm s/c pulley, but I've got some belt slippage as well. If he's got an overlay, he should be making more than 10 psi.

Twibs, did you see an increase in boost when you got it all sorted out?
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Old 04-07-2019, 01:22 PM
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If I remember right I was slipping about .5 of a psi before the belt broke on the dyno.

My before the overlay and after had similar max blower rpm. So no measureable difference except not breaking belts.

I did see an increase In boost with my bigger exhaust.
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Old 04-07-2019, 04:15 PM
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poormxdad if you dont have P/S, it might be worth looking into an ATI Damper, they have 6 rib support so they might line up correctly with the rotrex (since they align with the stock PS, and just have more rib space forward, its likely you can just bolt it on and add a 6 rib belt, and be done with it)

https://www.flyinmiata.com/ati-dampe...-kit-36-2.html

Probably better to talk with FM about it to confirm though.
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