Supercharged 3800

[d houlton x0710]

Bruce Plecan wrote:
> 
> From: Peter Jaramaz <pjaramaz at ingenico.com.au>
> To: 'diy_efi at EFI332.eng.ohio-state.edu' <diy_efi at EFI332.eng.ohio-state.edu>
> Date: Friday, May 01, 1998 12:52 AM
> Subject: RE: Supercharged 3800
> 
> 
>   All blowers need some lubrication.   If the TB is upstream of the
> blower than the engine vacuum is going to try and draw this lube
> into the intake charge when closing the butterflies at high rpm.
> If the butterflies are below the blower it sees no vacuum during
> this period of overrun.


Conversely, if the TB is downstream of the blower, then when going from
full throttle and boost to suddenly closing the throttles creates a 
reverse pressure pulse that may damage the blower.  i.e.  The blower's
still pumping air, but it has nowhere to go because the butterfiles are
closed.  It's a good idea to add a blow-off valve that routes the extra
air back to the intake of the blower to prevent damage until it has a
chance to wind down.  Of course, if you don't have a MAF sensor upstream
of the blow-off valve, you could just vent the extra to atmosphere as
well without screwing up the A/F ratio.

--Dan