Practical solution to variable compression

[Matthew B. Watts]

> I was talking to my mate who has been working on engines
> for about 30 years now, he told me about an 8 piston desiel
> engine with 4 cylinder bores and two crankshafts.
>The two pistons opposed each other and on the compression
> stroke would move towards each other causing a masive
> compression which would ignite the desiel and force the two
> apart.  It worked very well but was unreliable due to the fact
> that it had so many rotating parts...


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 a little
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?

Matt
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