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RE: [turbobike] Carb Question

Abraham Mara (AbeFM@dis.member.org)
Mon, 22 Nov 1999 10:10:21 -0800

Well, being used to big V-8, I am a little unsure where exactly to start for
a base number, but if your "big box" is WAY oversized, say a foot on a side,
that's 1 cu foot.  Assumeing that bit of math worked out, and that the bike
is pulling, oh, say 200 CFM, and we're presureizeing it to 1 atm guage, then
that's about 2 cu. feet for our 1 cu foot box.  Not that we're really
flowing the full amount yet, not being in  a steady state, but the idea
being in about 1/100 th of a minute (a touch over a half second) the big
cubic foot box should no longer be an issue.  Then again, a lot of that air
is going into the engine durring all this, so perhaps I should shut up.

-----Original Message-----
From: owner-turbobike@natvideo.com
[mailto:owner-turbobike@natvideo.com]On Behalf Of Bryan
Sent: Monday, November 22, 1999 9:26 AM
To: shammar@nsk-corp.com
Cc: FFDennis@aol.com; turbobike@natvideo.com
Subject: Re: [turbobike] Carb Question

Bob, I realilze that boost response and timing is primarily controlled by
the turbine sizing. However, that assuming all else equal. Given a fixed
A/R on the turbine, increasing the size of the plenum volume will increase
the time it takes to fill it. What I'm not sure of is how dramatic an
effect this will have.

P.S. Not trying to argue, just making friendly counter-discussion. :)

At 07:49 AM 11/22/99 -0500, shammar@nsk-corp.com wrote:
>Realistically you'll never get too much plenum volume.  The need for plenum
>volume is all but forgotten on four cylinder engines since the intake
events of
>the cylinders provide an almost uninteruppted flow out of the compressor.
>However, a larger accumulator volume reduces manifold pressure fluctuations
>between intake events.  On a twin, you'll run into surge much more easily
>must have a huge plenum.  Having a large plenum is akin to being able to
blow up
>a balloon with full lungs the whole time.  You don't want empty lungs
before the
>intake valve event has finished.
>Turbine response (how fast it makes boost) will be governed by the exhaust
>and turbocharger matching.
>That's just my $0.02.  I've built a few bikes but that doesn't mean
>Bryan <bgoodwin@iquest.net> on 11/21/99 01:37:26 PM
>To:   FFDennis@aol.com, turbobike@natvideo.com
>cc:    (bcc: Bob Shammas/EQA/Nsk-Corp)
>Fax to:
>Subject:  Re: [turbobike] Carb Question
>I think the only problem you would run into there is that the volume of the
>airbox would be too large. This might cause the turbo to boost later.
>At 10:38 AM 11/21/99 EST, FFDennis@aol.com wrote:
>>In a message dated 11/19/1999 23:56:32 Central Standard Time,
>><< Now for another question how about intake plenum and attaching it to CV
>> carbs?  Should I buy a set of velocity stack and machine them in order to
>> an intake plenum to the carbs that way?   I have a feeling that the
>> plenum I am currently using is robbing me of effieciency.
>>  >>
>>You raise another interesting possibility.....If you can encapsulate the
>>entire carburetor within a plenum, and then pressurize the entire plenum,
>>eliminate the need for separate pressurization lines for bowl vents, CV
>>vents, etc., as you would have equal pressure operating on all sides of
>>crab.  The pressure in the venturi would be lower than the other areas,
>>is how a carb works.  Your next problem is then to seal the throttle
>>and fuel lines where they pass into the plenum.  I've seen ram air setups
>>like this.  It seems to me that a turbo plenum could get away with being
>>aerodynamic internally due to the mechanical pressurization.
>>Just my .02.........lots of book knowledge and reading, I've never built a
>>turbo bike (but I have a KZ 900 motor in pieces, bead blasted, for a
>>'99 M2 Cyclone
>>'87 KLR 650 Urban Assault Vehicle
>>'78 KZ900 bike in boxes
>FZR1000 turbo EFI
>(aka The Money Pit)
FZR1000 turbo EFI
(aka The Money Pit)