Rotrex Superchargers

[Yazza54]

I have recently been looking into Rotrex'ing my GTM Libra B18C Type R engine kit car. I have figured out how to mount it, what belts to use, etc.. as no off the shelf kit designed for a civic or integra will fit in this car, installation wise I'm happy.

The kits use a C30-94 and that's what I've been looking for, but not had much luck. I've found quite a few C38 chargers which is the larger unit, and I was just wondering if it's possible to run a bigger unit but spin it slower. I'd ask the likes of TTS or someone but I doubt they'd give much information away without me actually buying it from them.

What I'm unsure of in a nutshell is, is oversizing a supercharger just as bad as lets say fitting too large a turbo to an engine? Will it be laggy or will I end up having to constantly bleed off pressure. I'm only looking to make around 9 psi but would be good to have some capacity for the future. I appreciate the B18 is only 1.8 but the C38 is commonly used on the K20A which is still a "small" engine.

Anyone with experience able to chime in? No guesswork please.

[Yazza54]

HappyMidget said:

Superchargers are fairly easy to change speed, just change the pulley size. Larger crank pulley makes it spin faster, so just get an underdrive pulley when you install it

I get that, but what I'm unsure of is will this be less responsive than the smaller C30-94 spinning faster?

[Yazza54]

There's some details here with compressor maps etc, but I'm not really versed in how to read them

http://www.google.co.uk/url?sa=t&rct=j&q=&...

https://www.verboom.net/images/speedster/20140419/...

[Yazza54]

Butter Face said:

GreenV8S said:

Rev limit on the engine?

It can be set to anywhere needed as part of the mapping; currently at 8300 so is overspeeding the charger at that point.

If you're overspeeding the charger already you won't net any more boost, you'll just shift the peak boost to earlier in the Rev range. But then you'll have to cap the Rev limit.

Edited by Yazza54 on Tuesday 4th September 08:18

[Yazza54]

I'll add that what I looked into a while ago, and found it has already been done with some success is the use of a wastegate in the system to bleed boost. Can be mechanical or electrically controlled. But this would only really work with a larger rotrex that was capable of much higher cfm than you need. If you want more boost and are already overspinning it sounds like you need a bigger unit.

Changing the pulleys to hit peak impeller RPM sooner and then capping the engine Rev limit will produce a more tractable engine but if you have the revs you may as well use them.

[Yazza54]

Butter Face said:

Thanks for the input, this is what I’m struggling with, if I’m already using all that the supercharger can do, why am I hitting just 0.6 bar of boost when the C30-94 should be a lot more?

Is your intercooler bigger than it needs to be? Associated piping large bore and long etc?