Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site watdaisy.UUCP
Path: utzoo!watmath!watdaisy!gvcormack
From: gvcormack@watdaisy.UUCP (Gordon V. Cormack)
Newsgroups: net.auto
Subject: Camless valve operation
Message-ID: <6848@watdaisy.UUCP>
Date: Tue, 8-Jan-85 10:26:00 EST
Article-I.D.: watdaisy.6848
Posted: Tue Jan  8 10:26:00 1985
Date-Received: Wed, 9-Jan-85 02:13:44 EST
Distribution: net
Organization: U of Waterloo, Ontario
Lines: 29

It has been suggested that the valves in an engine be operated
electrically rather than by a cam.  There is no doubt that such
operation could give more nearly optimal valve operation than
a fixed cam.

The above scheme has been implemented for the purposes of engine
testing (I can't remember the reference, it was either PM or C&D or
R&T in the last 10 years).  The trouble is that the solenoids to
operate the valves are tremendously inefficient and consume a
significant fraction of the overall output from the engine.  On a
test bench, this is not a problem.  In addition, the electronics
must switch a tremendous amount of current to operate the solenoids
quickly.  Such switches are not cheap.  The alternator, battery, etc.
on existing cars would also be totally inadequate.

If someone could invent an efficient mechanism to control the valves
like this, he would indeed have a better mousetrap.

I suggest the following compromise: (perhaps it has been investigated,
too)  use a twin-cam engine where the valve is open if either of the
cam lobes is up  (the valve operation is the OR of the two cams).
Statically, both cams are the same.  At increased engine speed,
one of the cams is advanced and the other retarded as necessary to
get the desired overlap.  The device to advance and retard the cams
should be feasible as it operates at a much lower speed than that
described above.  It could be implemented in much the same way
as existing hydraulic timing chain tensioners.  It is not clear
that the extra mechanical complexity is justified, but such a device
would give a factor of 2 in adjustment of the valve durations.