Practical solution to variable compression

[Dave Balfour]

2 stroke..... you put the intake ports on one side and the exhaust
on the other. I have seen it done. (:
dave balfour

----------
| From: Raymond C Drouillard <cosmic.ray at juno.com>
| To: diy_efi at efi332.eng.ohio-state.edu
| Cc: diy_efi at efi332.eng.ohio-state.edu
| Subject: Re: Practical solution to variable compression
| Date: Friday, March 13, 1998 9:56 PM
| 
| The only problem I could see with the dual piston setup is...
ummm...
| where do you put the valves?
| 
| Ray Drouillard
| 
| 
| On Fri, 13 Mar 1998 10:02:00 -0500 jb24 at chrysler.com writes:
| >Variable compression will see you huge gains in part-throttle
| >fuel-economy.  It's that thermodynamics thing that expresses
work 
| >being
| >done is the area between max pressure and min pressure on a
| >pressure/volume diagram.  If you up expansion ratio (by way of
upping
| >compression ratio) you get more work for a given amount of
pressure.
| >When my variable compression ratio two-stroke patent gets
approved, I
| >will share it with the list (and no, it is totally different
than the
| >below mechanism, you hope :).
| >---------------------- Forwarded by John R
Bucknell/JTE/Chrysler on
| >03/13/98 09:50 AM ---------------------------
| >
| >        owner-diy_efi @ efi332.eng.ohio-state.edu
| >        03/12/98 12:24 PM
| >Please respond to diy_efi at efi332.eng.ohio-state.edu @ SMTP
| >To: diy_efi @ efi332.eng.ohio-state.edu @ SMTP
| >cc:
| >Subject: Re: Practical solution to variable compression
| >
| >>
| >> I was thinking about this while designing a model of a 200cc
| >> two stroke engine (single bore only) that uses opposing
pistons...
| >>
| >> What if one tied the cranks together with a gear drive
mechanism
| >> having a gear on each crank and a pair of idler gears coupled
| >> together with a clutch that could only slip say, 15 degrees. 
By
| >> effectively putting the two cranks out of exact
synchronization,
| >> wouldn't you change the engine's compression?
| >>
| >> Think about it a minute.  If at exact alignment, the two
pistons
| >> reach TDC at the same time, then you have MAX compression.
| >> If the alignment is offset by allowing the clutch to slip
just alittle
| >> and then lock back up say ten degrees off sync, then you
would
| >> never have the two pistons reaching TDC at the same time. 
Thus,
| >> your compression ratio would drop.
| >>
| >> Now, my next question is...  Would you gain significant
performance
| >> by allowing high compression at low throttle settings and
then use
| >> a lower compression at WOT?
| >>
| >> Having variable compression seems like a cool idea, and I
| >> believe an engine and management system could be built to
| >> do it.  Looking this whole thing over, I'm pretty sure that
| >> MAX performance would still be limited the way any other
| >> engine is, but couldn't the whole power curve starting from
| >> way down low near idle be boosted considerably?
| >>
| >> Does this idea warrant any merit?
| >>
| >> Can anyone shoot BIG holes in it?
| >>
| >
| >The only real problem I can see is that one of the pistons
would
| >be potentially moving into the flame front, which could be a
| >problem.  I think it would be more useful with a gas engine,
| >where too much compression detonates things, and less useful in
a
| >diesel engine where this is mostly normal operation.   Still
| >it may be a problem with the piston trying to compress an
expanding
| >gas, knowing what knock does to an engine
| >
| >   Roger
| >> Matt
| 
|
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