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Rotrex belt slip at high rpm

Old 06-07-2018, 12:52 PM
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Default Rotrex belt slip at high rpm

finally got my c30-74 rotrex setup running and dyno'd.




At the dyno, the car shredded a belt but i had another and we pushed on. Ended up with this even with the belt slipping past 7k.. Flamesuit on for low torque.



I guess the question i have i can i convert to a 6 rib setup with a supermiata s/c damper? 949racing says it wont work, but my pulley has 2 more ribs on the front side and the spm sc pulley says its the same alignment as a stock pulley but with two more ribs out front. my basic math tells me it would work. ill just need a new pulley for the rotrex aswell.
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Old 06-07-2018, 01:20 PM
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Good results! What size pulley are you running on the Rotrex?

By the way, diggin' the intercooler set up ;-)
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Old 06-07-2018, 01:24 PM
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Blower has a 80mm pulley. About 9 psi before it slips. slip indicated by the rubber everywhere/hot belt and the belt breaking and the psi tapering off at high rpm

Your pics make the ic look like its supposed to fit there.. this is also a much bigger ic hence the pain in the *** to make fit
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Old 06-08-2018, 02:24 PM
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Originally Posted by Twibs415 View Post
Blower has a 80mm pulley. About 9 psi before it slips. slip indicated by the rubber everywhere/hot belt and the belt breaking and the psi tapering off at high rpm

Your pics make the ic look like its supposed to fit there.. this is also a much bigger ic hence the pain in the *** to make fit
With the four rib set up they can slip when you go too small on the pulley, but I've only heard of problems with the 75mm pulley. I've never moved on from my 85mm pulley and have never experienced any issues with it. Are you running A/C and P/S? What size belt?
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Old 06-08-2018, 02:29 PM
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no a/c or p/s. the belt is a 4pk1160, its the smallest i could fit for maximum wrap. im starting to think the no PS is the issue. there is no guidance up there by the blower and the belt being longer stays cooler.
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Old 06-09-2018, 12:06 AM
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Damn 312 whp on the smallest Rotrex? Good stuff.
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Old 06-09-2018, 01:28 AM
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Great numbers for the smaller Rotrex. I bet the intake plays a big role.

What’s up with that throttle body-IC tube funkiness. Square up that TB plate and you’ll be left with a straighter shot to the intercooler. Get some good bends and loose all those goofy pie cuts. I bet you can make the transition in 1-2 cuts.
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Old 06-09-2018, 02:54 AM
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Intake is 3 inch to 60mm.

I wish i could ditch the pie cut piece but I was having issues with the spm radiator and the charge pipe. The intake manifold has the tb pointed toward the center of the car so not much I could do. Iím not happy about it, but it works!
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Old 06-09-2018, 04:07 AM
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300hp with 9 psi is something new for me.

Regarding belt sleeping, I don’t think a 6 rib setup would help. That rotrex support is flexing , that’s my guess as I’ve seen before, it even ended up breaking on the top of the rotrex where the support its thinner.
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Old 06-09-2018, 02:02 PM
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Originally Posted by Twibs415 View Post
Intake is 3 inch to 60mm.

I wish i could ditch the pie cut piece but I was having issues with the spm radiator and the charge pipe. The intake manifold has the tb pointed toward the center of the car so not much I could do. Iím not happy about it, but it works!
look closer at the intake. That looks like a bolt on adapter thatís causing the throttle body to be cocked. Can you machine that piece square?
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Old 06-09-2018, 02:33 PM
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No that’s part of the manifold. I’m not interested in fixing it cause it’s not an issue. Like bracket flex/belt slip
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Old 06-09-2018, 06:19 PM
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You say you have 2 more ribs on both the SC and the crank, and they go the proper direction? That kinda sounds like a no-brainer to me. You can space the autotensioner forward, and get a different pulley for it.

Edit: i have no experience with Rotrex, but I DIY superchargers.... an additional bracket on the back of the SC makes a world of difference.
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Old 07-09-2018, 12:20 PM
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Default Itís fixed

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.

Ill hit the dyno later later this month to confirm no more belt slip and consistent boost. but Iím pretty sure itís fixed

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Old 07-09-2018, 12:29 PM
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Default Also...

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
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Old 07-10-2018, 04:21 PM
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Tbh I want to see more pics of that engine bay from engine to bumper. That's such a beautiful setup.
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Old 07-10-2018, 06:23 PM
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i have a build thread! or check out my IG thetwibs
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Old 07-10-2018, 07:07 PM
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use exhaust to spin it up. problem solved.
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Old 07-11-2018, 01:05 PM
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i was actually gonna use the exhaust to spin up a pinwheel with an extra flywheel i have so even when im not accelerating the pinwheel can propel me in a forward direction to make me faster.

Out with the turbo talk please.
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