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Forced Induction Turbo, Supercharger, Methanol, Nitrous


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Old 03-04-2019, 10:15 PM   #1
projek_01
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Opened up my Rotrex today. Here are my thoughts.

*Disclaimer - This is by no means a DIY or tutorial on how to rebuild a Rotrex. I'm no expert and may or not be doing things correctly.*

Growing up, one of my dream cars was the Honda S2000. So naturally, Skunk2 and Kraftwerks were known and trusted brands in my books.

I ended up getting a FR-S instead but still wanted a KW kit on my car.

After 4 years and ~18000kms, my supercharger seems to betting louder and recently started to hear some minor internal grinding.

DIY KW specific pulley counter-hold tool.




Heated the compressor wheel before using a pulley puller then hydraulic press to get it apart.




Observations so far:
Opening up the supercharger is quite hard, you need a counter-hold tool, a good vise, shop press, slide hammer.

Flaws that cause our superchargers to fail:
KW flaws:
1. Terrible belt system that rides a fine line between being over or under-tensioned. Over-tensioning causes premature failure of the bearings.

Rotrex flaws:
1. 8.8 grade bolts without lock-tite used internally that can back out.
2. Undersized (7mm) sun-shaft that can snap and cause the impeller to grind the compressor housing.
*** actually it's not undersized compared to a normal turbo. It's the hardened 60 HRC steel shaft that makes it brittle.***
3. Very tight tolerances internally that can cause catastrophic failure if anything where to get in-between the rollers. Change the oil and filter often!!
4. Very tight tolerances are also naturally temperature sensitive. A bigger oil cooler might do wonders.
5. Awful customer support, refusal to sell parts, create authorized repair shops or even rebuild them directly.

What's next for me:
Finish tearing everything apart, inspect surfaces and tolerances, then replace every seal/bearing.
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Old 03-05-2019, 12:39 PM   #2
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Sounds like they need on the team to get something done right. Top notch write up. Now I see why most stay away from KW and go JR instead.

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Old 03-05-2019, 12:59 PM   #3
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The sheer number of these Rotrex units failing makes me not want to install the JRSC that has been sitting in my shed for a few months. That said, it sounds like the issues are correlated with the belt tension, so maybe JR owners have less to worry about.

It feels like 50% of the Rotrex units seem to eventually have issues or get replaced entirely.

Good on you for cracking it open and spreading the info!
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Old 03-05-2019, 01:01 PM   #4
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The sheer number of these Rotrex units failing makes me not want to install the JRSC that has been sitting in my shed for a few months. That said, it sounds like the issues are correlated with the belt tension, so maybe JR owners have less to worry about.

It feels like 50% of the Rotrex owners seem to have issues or get a replacement unit eventually.

Good on you for cracking it open and spreading the info!
Haven't heard anyone with JR that has had issues tho. Maybe I'm just ignorant to what's out there.

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Old 03-05-2019, 01:03 PM   #5
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Quote:
Originally Posted by Joveen View Post
Haven't heard anyone with JR that has had issues tho. Maybe I'm just ignorant to what's out there.

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There are many replaced Rotrex units in the owners thread. I think the kit is otherwise top notch.
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Old 03-05-2019, 01:46 PM   #6
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Quote:
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Haven't heard anyone with JR that has had issues tho. Maybe I'm just ignorant to what's out there.

Lots of JR Rotrex units have failed. Mine did first year; bearing failure.
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Old 03-05-2019, 01:50 PM   #7
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Nice work disassembling the unit. Your shop looks like a laboratory - I'm jelly!
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Old 03-05-2019, 05:30 PM   #8
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Haha good eye! I'm a chemist by training working on the Rotrex while I'm waiting for lab tests to finish.

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Nice work disassembling the unit. Your shop looks like a laboratory - I'm jelly!
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Old 03-05-2019, 05:45 PM   #9
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Haha good eye! I'm a chemist by training working on the Rotrex while I'm waiting for lab tests to finish.
what kind of lab has a bench vise in it?!?
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Old 03-05-2019, 07:40 PM   #10
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healthy jrsc checking in, just dont want the only vocal owners to be the 2% horror stories.
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Old 03-05-2019, 08:42 PM   #11
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Another jrsc with more than 20k miles
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Old 03-06-2019, 03:29 PM   #12
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O&G lab. I'm fortunate that we build and maintain a lot of our lab equipment. So we have a decent amount of tools on hand.

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what kind of lab has a bench vise in it?!?
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Old 03-06-2019, 05:35 PM   #13
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CSG BRZ #2 with a JR kit ran perfectly fine without any Rotrex issues for 55k+ miles. The subsequent owner of that kit is also enjoying the kit without any Rotrex issues.

Remember, this was a kit that was used for hard R&D at the track, and was on the HBP for the majority of it's life.

CSG purchased the kit for their own R&D and internal testing; this is not a shill or paid opinion, unlike so many posts from shops and influencers out there.
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Old 03-06-2019, 07:35 PM   #14
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I recently bought a used JRSC for the hardware, previous owner ended up also giving me the Rotrex unit(Owner said it seized). I took it apart in attempt to rebuild it, everything was well inside, except the sun shaft. Found a website that claims they sell "New" sun shafts. As projek_01 said, Rotrex won't sell you any replacement parts or recommend to attempt to rebuilding them. Due to the tight tolerance (Friction driven unit) and the "Incorrect disassembly/assembly procedures. I did so much web search about rebuilding these units. I only came across one guy with a M3 that rebuilt his and has been running it for a year now. All the bearings and seals are good in mine, so I'll be ordering the shaft within the next weeks.
https://www.superchargerrebuild.com/rotrex-rebuild/ Not sure where they source the "New" parts but as long as I get over a year out of it, I'll be happy.
http://www.m3forum.net/m3forum/showthread.php?t=598558 This is the link to the guy that rebuilt it, there is also a link to a photo album of a guy from Heath Racing that rebuilds these for Race teams.

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