DIY_EFI Digest V5 #578

[Dan Zorde]

Here's an idea for variable boost.  On a setup like a suck thru system
where you use a bypass valve for closed and partly open throttle blades,
what about using a 2nd set of throttle blades before the s/c to restrict
the air going into the s/c and then use the bypass (or a 2nd bypass) to
give you the required air for the engine.  This way you control the amount
of boost by varying tha amount of air the s/c can suck.  Only disadvantage
I can think of is that the air might get quite hot if the s/c is restricted
too much at high speeds.  I have tried the blow off approach, and rest
assured that a 62mm outlet at 6500rpm on a Toyota MR2 s/c is VERY noisy
(the dB meter full scaled at 124dB and the needle was off the end).

Dan  dzorde at erggroup.com


  From: Walter Sherwin=20
  To: gmecm at diy-efi.org ; diy_efi at diy-efi.org=20
  Sent: Friday, April 13, 2001 12:25 AM
  Subject: Twin Centrifugals VS Single


  Forwarded from another list.....



  >Here's something I've been tossing around in my mind, for street toy =
use, and I'd love to hear more from the group........

  >Let's say you have a large displacement stroker motor, and you desire =
to artificially stuff it's hunger with centrifugal supercharging (non =
manufacturer specific at this >point).  The typical approach today would =
be to seek out a largish single centrifugal unit that would do the dirty =
job, and pulley it to gain the max desired air flow/boost at >a specific =
engine speed.  This would net you a large diameter centrifugal, =
operating at a somewhat less than maximum impeller speed, hung from one =
side of your >engine.  This would work, and you would prolly have a cog =
belt drive arrangement as a result, if you wanted serious manifold =
pressure.  Of course this will generate a new >force/belt vector load at =
the nose of the crank, that may or may not affect your front bearings.  =
One might even direct the output of this large compressor to a single =
>inter/aftercooler device for post cooling.

  >Let's consider a different approach......

  >What about mounting two smaller centrifugals, low on the motor, =
perhaps directly opposed to the crank centerline so as to cancel the =
belt load vectors.  Further imagine >the discharge(s) from these =
compressors being directed thru two parallel inter/aftercooler =
exchangers (ala: Porsche twin turbo setups).  The twin intercoolers =
might be a >bit easier to position within a street vehicle.  At an =
esoteric design level, twins could allow a person to fabricate an engine =
bay setup that has a symmetric and artful >appearance.

  >Cost aside, does anyone see any further advantages/disadvantages to =
running two slightly smaller compressors in place of one larger unit?  =
Obviously, the cost will be >higher with twins.  I'm more wondering =
about airflow versus crank speed, throttle response, boost response =
profile, parasitic drain at a given combined flow/pressure, >etc.   =20

  >Thoughts would be appreciated;
  >Walt.



---------------------------- ERG Group --------------------------
 The contents of this email and any attachments are confidential
 and may only be read by the intended recipient.
-----------------------------------------------------------------

----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org