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From: prins@cornell.UUCP (Jan Prins)
Newsgroups: net.auto
Subject: Electronic valve control
Message-ID: <994@cornell.UUCP>
Date: Tue, 8-Jan-85 19:40:06 EST
Article-I.D.: cornell.994
Posted: Tue Jan  8 19:40:06 1985
Date-Received: Wed, 9-Jan-85 06:28:44 EST
References: <498@amdcad.UUCP>
Reply-To: prins@gvax.UUCP (Jan Prins)
Distribution: net
Organization: Cornell Univ. CS Dept.
Lines: 27
Summary: 

Phil Ngai suggests electronically controlled valve actuation could be even more
exciting than breakerless ignition!  But why settle for "programmable" cams --
when you could have dynamic valve timing.  Increase lift and duration with rpm
and throttle position and your lightweight idlemaster economotor might become
a nasty 125 hp/liter screamer at high revs.

But how could you make electromechanical valves work?  Do you open conventional
valves with solenoids?  The current requirements would be impossible.  Desmo-
dromic actuation (push to open, pull to close) would be preferable -- the valves
would be much easier to open without a stiff spring, and the resultant decrease
in forces would allow the valves themselves to be much smaller and lighter.  
Still, to accelerate a valve over 10mm in 40 degrees of crank revolution at 7200
rpm (specs suitably blue-sky, to fit pipe-dreams) will require enormous forces.
Can it be done?

Moreover, you may need to control the opening/closing rate, to capitalize on 
all the gas flow quirks that the cam people know all about, not to mention the 
proper operation at TDC overlap while staying out of the pistons way.  That
brings up another difficulty.  One program/transducer/whatever error, just one,
in those hundreds of events per second, and your motor will be dining on valves.


Maybe those messy chains, inflexible cams, funky followers and stiff springs
aren't so bad after all...  But it can't hurt to dream!  Uh, except when you
have work to do.

cornell!prins