turbo sizing

[Dave Morrill]

Group,
	I have a ZRT800 turbocharged snowmobile, and I assure you, turbocharged
2 strokes DO work, amazingly well.  Several friends also have turboed 2
strokes, all making significant power gains and are fairly reliable.

	I've just built a piggyback fuel injection system with a custom analog
computer that I designed and built, It really makes a lot of power. 
Based on the fuel consumption that I am using, I'm putting out over
250hp out of an 800cc engine, will have dyno data in the next few weeks
to confirm.
	
Best,
	Dave.


jb24 at chrysler.com wrote:
> 
> >>
> >> A while ago there was a discussion here about turbocharging a
> >> two-stroke, and the general consensus was that it couldn't be done,
> >> or was very difficult, at least. So how is it done?
> >>
> >> Stuart.
> >
> >First off I want to say that I am admittedly no expert on 2 stroke
> >engines.  The only one I have ever owned was in my 175 Yamaha Enduro.
> >However, I am quite familiar with their operation I would would venture
> >to say that there is no reason why a 2 stroke couldn't be turbo'd or
> >supercharged.  I would agree that it would be more difficult to
> >achieve high levels of boost but providing that the reed valves are
> >stiff enough to counter the highest boost but not so stiff that they
> >won't open during the downstroke of the piston then you should achieve
> >some gains.  Granted, you will be likely to have a great deal more
> >of blowby into the exhaust if turboing a 2-stroke but it should work
> >to some degree.
> > I would agree, though, that turboing or supercharging a 4-stroke
> >does make a little more sense and will make better gains (at least in
> >efficiency).
> >
> >--
> >Christopher Bruno
> >Teradyne
> 
> Where supercharged snowmobiles get their gains are when the pumping
> action of the cases aren't at their most efficient.  Tuned pipes only
> work at certain rpms, and they stuff as much fresh charge into the
> cylinder as possible, but charge purity is only like 80% in the tuned
> range.  Turbos can get 90% or more all the time.  So you get the power
> by blowing tons of fresh charge out the exhaust.  Peak cylinder
> pressure won't get a lot higher like it does in four strokes.  That is
> why turbo two strokes don't really "work", you can't double or triple
> horsepower by the same multiple of boost pressure over ambient.  The
> most that can be achieved is what normally aspirated race engines do
> today (sometimes not even that much).
> 
> John Bucknell is jb24 at chrysler.com