Teach me about Rotrex superchargers

Any of you guys have hands-on experience with them?

Superchargers are a little confusing to me in general, so i have some reading to do, but for now, i'm interested in impressions.

Looks like it is driven by an internal clutch (to reduce surging at idle I suppose) and driven by a set of planetary gears. Interesting solution.

I've never been impressed with superchargers over turbochargers due to the friction losses involved and the lack of breathing at high RPM, but I know they can work well and the newer gear reduction style units have power curves closer to turbochargers than the old roots style units and they are more efficient.

Hopefully this will generate some good content as it could be fun to learn more about this :)

I'd like to learn more as well, I feel like I know very little about these and other superchargers...

I believe it's Vortech who now makes a centrifugal supercharger that contains a CVT in it. That means the boost level and response is adjustable on the fly.

The Rotrex is a centrifugal. That basically means a gear-driven turbo. Boost is directly proportional to engine RPM. How it makes that happen is what sets the Rotrex apart from others, but the first decision is whether you want positive displacement (Roots, twin screw, boost not tied to engine speed, lower efficiency, physically bigger supercharger) or centrifugal (easy packaging, lower bottom end boost, high efficiency).

I've always felt that centrifugal superchargers make an engine feel like a highly tuned naturally aspirated unit. Positive displacement makes them feel like bigger displacement.

Centrifugal is what i'm interested in.

There was a guy that created a Rotrex supercharger kit for VTEC VFR's. Power went from something like 95hp at the rear wheel to about 145hp. This was with 780cc of displacement. It was a very neat kit.

That's really all I know; on a VFR, they're neat.

I know this runs one.

What's the curve like with it? That particular car has almost nothing in common with the car i'm considering using one on, save for cylinder count, but i figure it's worth something.

Stupid and arbitrary power goal would be 500hp or so. Yes, i know that turbo would probably be cheaper and more tried-and-true, i'm just tossing the idea around for the moment.

I think more variables need to be defined:

How large an engine?

RPM range?

Weight of car?

I have some experience with Rotrex superchargers. I have had two of them (still have one), both on an S2000.

S2000 #1 was an AP1 which revved to 9400 RPMS. It had a Rotrex C30-94.

S2000 #2, which I still have, is an AP2 and revs to 8600 RPMs. Also a C30-94.

Both were/are overspinning the SC beyond the factory suggested limit. The AP1 eventually let go at 15-20k miles, the AP2 is still going strong at over 35k miles.

I took apart the one that blew, there are no gears. The pulley and the impeller are not connected. There is traction fluid that thickens and engages it. It is VERY efficient. I eventually had the one that broke rebuilt by some guy in TX, the factory does not rebuild them. Once it breaks, its toast ... and they do have a lifetime. They are also not cheap.

Mine was not like the one on the picture above, it did not have those clutches.

I believe the one that broke, was due to the high RPMs the AP1 was able to spin at. When I bought it, the factory recommended no more than 120k RPMs, but then they backed that number to 100k. I still spun them to 120K. I think if you have a car that revs no more than 8k RPMs, you can still take the SC to 120k RPMs with no problems.

I drove one of them from Florida to California and back ... they are a lot of fun. very cool little units.

If you have any specific questions, let me know. Also what car would you be looking at installing it on?

Also, mine was part of a kit put together by Kraftwerks (Used to be owned and developed by Oscar Jackson and son). I visited them in California, two VERY nice guys, they took me for a spin in a Miata with one. That was one fun little car. I believe it also had a C30-94.

turboswede wrote: I think more variables need to be defined: How large an engine? RPM range? Weight of car?

2.0-2.2 litre 4 cylinder.
8000-9000rpms.
2000-2200lbs.

All theoretical.

The rotation speed is what i'm most confused about. Are different sized pulleys available enough that i'd be able to avoid what happened with Slippery and overspinning them? The ones i'm looking at seem to be rated at 90,000.

Sorry, guys, it's actually Procharger:

http://www.procharger.com/i-1supercharger.shtml

Swank Force One wrote:

turboswede wrote: I think more variables need to be defined: How large an engine? RPM range? Weight of car?

2.0-2.2 litre 4 cylinder. 8000-9000rpms. 2000-2200lbs. All theoretical. The rotation speed is what i'm most confused about. Are different sized pulleys available enough that i'd be able to avoid what happened with Slippery and overspinning them? The ones i'm looking at seem to be rated at 90,000.

Not sure about the Rotrex ones, but different sized pulleys are available for just about any other supercharger. The smaller the pulley, the more boost.

With centrifugal blowers, there's also a way of using an external wastegate installed in the charge piping to allow boost control.

Basically, you install an exhaust wastegate in your charge piping, referencing it to the intake manifold, and use it to maintain a lower pressure than what the blower's pulley would normally produce, thus giving you more boost at lower RPMs and less boost at higher RPMs. You're doing this by venting excess boost to the ambient atmosphere when the boost level exceeds the wastegate spring. You using a blow-through MAF setup, as well.

I'm not worried about boost control, just blower RPM. My power goal is pretty much at the top of what the blower is "rated" to anyways.

Swank Force One wrote: I'm not worried about boost control, just blower RPM. My power goal is pretty much at the top of what the blower is "rated" to anyways.

You tree'd me in the middle of editing that post. You might want boost control, because utilizing a wastegate allows higher boost at lower RPMs.

Well... it would only allow higher boost at lower RPMs if you desired max boost is achieved at less than max blower RPM, right? If i'm spinning the blower to it's 90k max at my redline, i don't have a way to get more boost anywhere across the board than what the blower will "naturally" put out, right?

I could be wrong, i'm not great with this stuff. Turbos are my thing.

I'd prefer to just use a MAP based setup... my only experience with MAFs and standalones is the benefit i get when i get to delete my MAF.

I made my own pulleys in 5 mm increments

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With your numbers, I would run a C38 if there is enough space.

I made 382 rwhp on dynojet with the C30, with a C38 you can probably go over 400rwhp

Rotrex kits are popular in the s2k world, so I'd say 9000 engine rpm will be fine.

And I think I know what you're planning this for....... and I like it

I was just looking at running one of the two biggest C38s.

Hmm, using speed density with a centrifugal blower? I've never seen it done. It would certainly simplify the routing of the blow-off valve, since it would vent to ambient. Then again, locating the MAF sensor near the throttle body allows ambient venting, too.

(Yes, you need a BOV with a centrifugal blower. The blower keeps spinning after the throttle closes, just like on a turbocharger.)

Top end of a medium turbo, bottom end of an N/A car, linear blend of the two in the middle, in other words, terrible.

Sky_Render wrote: Hmm, using speed density with a centrifugal blower? I've never seen it done. It would certainly simplify the routing of the blow-off valve, since it would vent to ambient. Then again, locating the MAF sensor near the throttle body allows ambient venting, too. (Yes, you need a BOV with a centrifugal blower. The blower keeps spinning after the throttle closes, just like on a turbocharger.)

I'm pretty sure all the C30 miatas just run speed density.

Leafy wrote: Top end of a medium turbo, bottom end of an N/A car, linear blend of the two in the middle, in other words, terrible.

Still more power than your super crazy SSM car. Suck it! Fast is fast.

It's just an idea. What will more likely happen is that i'll end up sticking with the FaeFae turbo.