DIY_EFI Digest V5 #578

[Bruce Plecan]

Might hunt up info on the Accel Priority Valve
Bruce



> 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.
>
>
>
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