turbo sizing

[Dave Morrill]

Steve,
	Not sure, but you guys may be barking up the wrong tree.  The reeds
should be able to seal with no problem.  I don't exhibit this problem at
all, I have a significant power improvement from 8 to 15 pounds boost. 
Yes, this is seat of the pants.  I won't be able to set up a dyno run
until 2 weeks from now, but you can really REALLY feel the difference as
you turn up the boost.  I have stock reeds.  

	My thoughts are that your turbo is undersized, or the A/R ratio is
wrong, or the turbo is overspeeding or surging, etc..   What are you
using for a turbo?  The only other problem you may be having is fuel
delivery.  Are you raising fuel pressure with boost, or leaving it
constant?  Do you monitor EGT?  

	Here are my CFM calcs for the ZRT800 engine:
	at 45degrees F, sea level
stock  201
8lbs   315 
10lbs  332 
12lbs  350
14lbs  365
15lbs  373

	What may be happening is that your turbo may be just big enough to run
at a reasonable efficiency at 300cfm, but as you go higher on boost, you
are below 60% and you get too much air heating, or the compressor is
surging.
	At 15lbs boost, the air is heated from 45 to 211 degrees at 65%
compressor efficiency, at 45% it gets heated to 285 degrees and you drop
to 336 cfm, from 373.  

	Do you have the compressor map?  I would be interested in comparing
your cfm numbers.

Best,
	Dave.

Steve Leonard wrote:
> 
> Dave,
>    I have been helping my friend on his 1998 Ski-doo
> Mach Z, with the 800cc Suzuki triple, using a Motec
> controller. Typical bosch injectors etc.
> We made 223 HP at 9,200. 0n 8lbs of boost. Here is
> the kicker, on 10lbs of boost it made 202hp, at 12lbs
> it made 186hp. We said what the F#%@!!!!!
>   It turns out the reed valves won't seal under these
> boost conditions, we tried several aftermarket reeds
> with minimal success.
>   The sad part is, a 670cc rotary valve bored to
> 724cc, is making 240 on 10lbs boost, carburated! So
> we are still looking for answers.
> 
> 
>                                 cya
>                               Steve L
> 
> ---Dave Morrill <david.p.morrill at fairchildsemi.com>
> wrote:
> >
> > Steve,
> >       Would love it if you'd post a summary of what
> you've learned.  I have
> > turbocharged ZRT800 snowmobile which I've put a
> piggyback fuel injection
> > system.  I started it for the first time last night
> but didn't have time
> > to test.  Anything you have learned would be
> applicable to me and I'm
> > sure everyone on the group.
> >
> > Thanks,
> >       Dave.
> >
> > Steve Leonard wrote:
> > >
> > >    I just wanted to thank everybody on this list
> for
> > > all the information you have given me on my Turbo
> > > Suzuki motorcycle and our Formula SAE Turbo single
> > > cylinder.
> > >    On another note, My Pentium computer has been
> > > infested with a virus, the virus has killed both
> hard
> > > drives. So much for the latest version of McAfee's
> > > Virus program, I'm using my ole 486 25mhz, in the
> > > meantime anybody that has sent mail to me in the
> last
> > > couple weeks and I haven't replied, forgive me.
> > >
> > >                                         regards,
> > >                                       Steve L
> > >                                       UB SAE
> > >
> > >
> > >
> > >
> _________________________________________________________
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> >
> 
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