PWM an electromagnetic (A/C) clutch?

[rob files]

Hi Dan,

I think this would be a bad idea because of the reason you mentioned.  
Basically I think it would wear out the clutch very fast.  This is basically 
because you are limiting boost by slipping the clutch.  As an MR2SC owner 
myself I know that the clutches wear out during normal usage which is on 
above 10" of HG engine vacuum with about 10 seconds of minimum on time.

The best way to limit boost is take another page from the Toyota SC setup; a 
bypas valve.  You could pick a bypass valve (some random turbo BOV should 
work fine) that opens at 8psi say with just the pressure diff across the in 
and out ports.  Then using a Vacuum Switching Valve (VSV in Toyota speak), 
you could pulse boost pressure to the vacuum port that keep it closed until 
the desire boost is achieved.  Does that make sense?

But the real quesiton is why would you want to control boost with an SC 
setup?  The gas pedal does a real good job of it on it's own :).

If you have any questions, feel free to email me directly.

-Rob


From: Daniel Houlton <houlster at user1.inficad.com>
>Reply-To: diy_efi at diy-efi.org
>To: diy_efi at diy-efi.org (EFI )
>Subject: PWM an electromagnetic (A/C) clutch?
>Date: Tue, 18 Dec 2001 11:25:13 -0700 (MST)
>
>Any thoughts on how an A/C type clutch would like being
>PWM'd?
>
>I've been thinking about the clutch used on the supercharged
>MR2.  It's similar to an A/C clutch.  I've got an Eaton M90
>installation just about completed and was toying with the
>idea of using an electric clutch on the pulley to limit boost
>and/or have a 'valet' mode.
>
>In theory, you could PWM the clutch to limit SC rotor speed
>to get any boost level you want up to max boost.  Not sure
>how it would work in reality though.  Seems the clutch
>would maybe over-heat, or just wear out as they're not
>really designed for modulation.
>
>Any thoughts?
>
>
>thanks
>--Dan
>houlster at inficad.com
>
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