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OBE
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bit quick that!!...
 

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I'd like to see the dyno sheet.

I've had Rotrex chargers and they aren't really suited to small engines IMO.

Fine for track as you're only using the top end but laggy on the road

(may as well use a turbo, except its easier to make a Rotrex kit)
 

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Mark, TrackDayHookey on mt.net/m.net is pushing well over 300hp with his Kraftworks Rotex.

Emillo from 949Racing is pushing less than that but it's still a lovely powerband.



Is laggy the right term? it's not like the turbine is/can spool up, it's just you're not in the right gear?
 

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Rotex Chargers are great on small engines, just need the right one.

i know of a few that are running on 1.3 (polo g40) and 1.8 (golf gti) engines with great results.

They are bloody expensive tho!
 

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Oh, hai!
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It's certainly compressor stalling on throttle lift. If the video didn't say it had a Rotrex charger on there, I'd argue blind it was a turbo.

'tis fast though!
 

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Richy (or anyone) care to post up a decent IC'd MP62 for comparison.

Maybe laggy isn't the correct term but you know what I mean... its hardly a V8 like power curve.

I guess if you like the Vtec type power curve or its a track car or its substantially cheaper than the other options its worth a look but it doesn't appeal to me for a road car.
 

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spending too much money
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are you sure thats compressor stall?

To me it sounds like a dump valve to atmosphere, with the supercharger obviously still compressing air but going through the dump valve.

Still its dam fast, i ve been in a ep3 with a rotrex, must admit power delivery is more like a turbo (centrifugal charger if you want to read up) but jesus when its on song its going for it.
 

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I will let you know whether it is "laggy" when I get the Kraftwerks Rotrex kit fitted to my 1.8 2003. Emilio (949 Racing ) claims the power deliver is reminiscent of that from a BMW straight six. I had a IC'd MP62 on my previous car and so it will be an interesting comprison
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Would be easy to tell - compare dyno graphs.

Although I have a BMW 328 and find its delivery very dull so I hope for your sake its not the same.
 

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Wow that shifts, even if all the other cars on track are NA and stuck in 5th!!!!!!!
 

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That thread is a good read and I love it when people have a go themselves so all credit to him.

BUT I'd prefer Big Gulps MP62.
after seeing detailed pics of it from the owner I wouldn't anymore, it was impressive but no effort went into the details, it's all headline, new owner sounds like he's having fun getting it 'straight'
 

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BUT I'd prefer Big Gulps MP62.
Does the MP62 give a more flat torque curve ? (please someone post a decent curve
)
If yes, why ? I thought that for a supercharger, boost was proportional to engine speed, so I would have expected similar curves for both rotrex and MP62...
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Not all superchargers are equal... the rotrex is a centrifugal - think of it as an easy to package mechanical turbo.

IMO its easy to fit but has all the downsides of both SC's (less efficient) and turbos (lack of instant low down response).

The owner sums it up well:

It has to do entirely with the delivery vs. RPM for centrifugal compressors.

When people think supercharger, they usually think positive displacement ("roots", MP62, etc.). Almost perfectly level torque, since the blower pumps out the same volume of air (more or less) per crank rotation, independent (more or less) of crank speed. So the cylinder ends up filled about the same at any crank speed.

A centrifugal blower has a delivery curve that pointy heads usually refer to as "square law". In this case, that means that 2x the rpm produces 4x the flow, and also approximately 4x the horsepower. So you get a torque curve that is roughly proportional to rpm and a power curve that is roughly proportional to the square of the rpm.

Engine VE tends to flatten this out - good VE in the midrange picks that area up, while poor VE at high revs pushes the peak down.

No amount of tuning will make significantly more torque at 4K rpm. The blower simply won't flow any air at that speed, assuming the blower is geared to stay below redline through the full engine rpm range. In a turbo car the blower spins at whatever speed is required to make the design boost (assuming that the turbo is "spooled" and that the wastegate is actually controlling things as expected). So you get monster torque down low where the engine VE is good and plenty of flow is available.

Fortunately for a track car that doesn't matter much. If you are at 4K rpm you are in the wrong gear, plain and simple.
 
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