Supercharger Boost Control

[Yazza54]

Hi gents

I'm looking to supercharge the B18C type R Honda engine in my GTM Libra. For various reasons I want to use a centrifugal vortech supercharger.

I'm happy with the application etc but this will be my first venture delving into force induction - most people who use a centrifugal supercharger select the pulleys based on the max impeller speed they want to run based on a estimated max boost. For example the vortech I want to use can have a max impeller speed of 52000 rpm, but I know some people who use the same unit on GT86s run them at 42000rpm at peak engine revs which gives them 9psi at maximum revs, so they have a linear power spread but only ever get their maximum boost at peak revs.

My question is, can't I just forget all that and run it at 52000 rpm at peak engine RPM and control the boost/bleed off somehow, to gain mid range and build the boost earlier?

[stevieturbo]

Yazza54 said:

Hi gents

I'm looking to supercharge the B18C type R Honda engine in my GTM Libra. For various reasons I want to use a centrifugal vortech supercharger.

I'm happy with the application etc but this will be my first venture delving into force induction - most people who use a centrifugal supercharger select the pulleys based on the max impeller speed they want to run based on a estimated max boost. For example the vortech I want to use can have a max impeller speed of 52000 rpm, but I know some people who use the same unit on GT86s run them at 42000rpm at peak engine revs which gives them 9psi at maximum revs, so they have a linear power spread but only ever get their maximum boost at peak revs.

My question is, can't I just forget all that and run it at 52000 rpm at peak engine RPM and control the boost/bleed off somehow, to gain mid range and build the boost earlier?

You can, some do ( and other methods too ). But dumping air is apparently bad for the compressor, bad for the unit and it is less efficient. And really...any difference in boost at the low end really will be marginal anyway.

Keep it simple.

[Yazza54]

You're probably right, geared for max impeller RPM at max engine RPM only gives me about 3000 higher impeller rpm at 4000 engine rpm than if I had it set to give me what I want at peak rather than bleeding off. Not worth the additional complication

Edited by Yazza54 on Friday 8th September 11:45

[SuperchargedVR6]

Yazza54 said:

, to gain mid range and build the boost earlier?

You won't be wanting a centrifugal blower then.

[GreenV8S]

It is much easier to lose power than to gain it. If your concern is to avoid excessive power or cylinder pressure at high RPM, you can probably address that by fuel and ignition timing maps.

[Yazza54]

SuperchargedVR6 said:

You won't be wanting a centrifugal blower then.

I am aware of the characteristics of a centrifugal supercharger mate. Just thought this may optimise the setup a little, but given the impeller speed difference at low-mid RPM it's not worth the bother.

Edited by Yazza54 on Wednesday 13th September 20:48