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Re: [turbobike] Carb Question

Bryan (bgoodwin@iquest.net)
Mon, 22 Nov 1999 12:21:56 -0500

50% of 1000cc doesn't seem like much. Have you ever seen a 1L container
before? 1L is equal to 1.1 qt if I am not mistaken. That's makes 1L roughly
35 oz. or so. Half of that would make your plenum not much larger than a
tallboy beercan.

When I say a large plenum, I'm talking a box big enough to envelope an
entire rack of carburetors plus have open space. When you figure all the
gaps and other spaces around the carbs, I'm thinking an airbox of ,say, 4
to 6 liters.

At 09:39 AM 11/22/99 -0500, Jeffrey K. Churchill wrote:
>  I think you are dead-on,....the formula is something like 50% of engine
>displacement on a four stroke,..right ??
>  Funny thing is,..I didn't do it on my Buell turbo project bike,...it
>has practically
>no plenum volume,...but responds and runs great.  The .63 turbine  A/R 
>is a little
>big for a street bike,....I haven't fully tested the .48  hotside
>yet,...but I found that the
>key was making the intermediate (carb)  circuit lean enough for good
>while adding an additional main fuel circuit for adequate high rpm
>  It seems that the overall fuel needs are so broad that a regular carb
>compensate properly.  Of course  F.I.  solves this nicely.
>  I'm sure my solution is not unique,...but the method and result was
>eye-opening.  Using a cv carb allows good velocity everywhere,  and MAY
>why I am getting away with no plenum.  The extra fuel circuit doesn't cut
>in until
>the slide lifts over 3/4,...allowing a smaller regular main jet and
>needle combo.
>  Have you seen something like this before ??
>Jeff Churchill
>J.C. Performance    617-06 Bicycle Path   Pt Jeff Sta  NY  11776   USA
>techline: 631-928-9863    Fax:  631 928-6679
>website:   www.jcperformance.com
>On Mon, 22 Nov 1999 07:49:13 -0500 shammar@nsk-corp.com writes:
>> 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 and
>> 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 event
>> and turbocharger matching.
>> That's just my $0.02.  I've built a few bikes but that doesn't mean 
>> anything
>> either.
>> Bob
>> 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, 
>> ABNZX9@aol.com
>> >writes:
>> >
>> ><< 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
>> >fit
>> > an intake plenum to the carbs that way?   I have a feeling that 
>> the intake
>> > 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,
>> you
>> >eliminate the need for separate pressurization lines for bowl 
>> vents, CV
>> slide
>> >vents, etc., as you would have equal pressure operating on all 
>> sides of the
>> >crab.  The pressure in the venturi would be lower than the other 
>> areas,
>> which
>> >is how a carb works.  Your next problem is then to seal the 
>> throttle cables
>> >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
>> less
>> >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 future
>> >project......)
>> >
>> >Dennis
>> >'99 M2 Cyclone
>> >'87 KLR 650 Urban Assault Vehicle
>> >'78 KZ900 bike in boxes
>> >
>> >
>> bgoodwin@iquest.net
>> FZR1000 turbo EFI
>> (aka The Money Pit)
FZR1000 turbo EFI
(aka The Money Pit)