Reply to: Re[3]: Variable cam timing

[RABBITT_Andrew at mv8.orbeng.com.au]

infinitely variable cam phasing and duration has already been acheived 
by Austin-Rover in the UK on their K-series 1.8L engine fitted to the 
new MGF.

This uses a mechanism which controls the speed fluctuation of the cam 
such that the speed of the cam during which the valve is lifted 
determines the cam duration and likewise when the valve is seated the 
cam phasing can be controlled.

A hydraulic bleed system would have a significant BSFC penalty and I'd 
be interested in how an electrical synchronous drive could guarantee
the correct cam phasing, especially during start-up

Andrew Rabbitt
oecar1 at orbeng.com.au

From: jfaubion at cs-smtp.tyndall.af.mil:smtp
Date: ## 05/06/96 17:10 ##

>ehernan3 at ford.com (Edward Hernandez (R)) Wrote: | 
     
>I remember a mechanical type described in Motor Trend a while back.  The 
>chain end of the camshaft was threaded, and the sprocket screwed onto the 
>thread.  There was an oil driven piston that pressed against the sprocket.  
>As the piston moved the sprocket back and forth, it caused the camshaft to 
>be advanced or retarded via the threads.  It was a very coarse thread.

<SNIP>

This would change only the timing, not the shape of the lobe. Controlling 
the lift and duration of the valve would change the performance much more 
dramatically. Why not use a solenoid valve to bleed off pressure from 
hydraulic lifters? The cam could be ground much more radical and the 
computer could easily bleed