Variable cam timing again

[SRavet at bangate.compaq.com]

Bruno! <u933234 at student.canberra.edu.au> Wrote:
| 
| Hi everyone,
| 
| Thanks for your ideas on this topic. A couple of you pointed out that 
| duration at high rpm would be a limiting factor to the overall 
| performance. 
| 
| So what I thought about was again with the synchro idea - the phase of 
the
| two would be controlled by computer, what could happen is that if the cam
| duration is set to be optimised in the low rpw range, when it goes into
| the higher rpm range, the valve opening time could be extended by 
altering
| the amount of slip in the two motors. what essentially happens here is 
| that the cam gear is not spinning at a constant speed, rather varying 
| sinusoidally. Relative to the speed of the crank, if the cam gear is 
| rotating slower, the valve is opened for longer. when the valve is 
| supposed to be closed, the motors controlling the cams could then speed 
| them up, setting the timing straight again.
| 
| There would not be a sudden jump from one engine mode (such as selecting 
| from two cam profiles mechanically, such as in a vtec type system), i.e. 
the 
| sinusoidal control could come on gradually. 

But the cam can't turn slower than the crank, at least not for very long, 
unless it turns faster later on to make up the difference.  Or were you 
suggesting that it speeds up and slows down during each revolution.  That 
could work.  Other wise it gets later and later until the valves are 
opening/closing at the totally wrong times.  As someone else mentioned, 
these schemes just modify cam timing.  The real gains would be being able 
to control overlap, etc.  I don't see how you could get that kind of 
control while using a cam shaft.

Ed, are you going to say anything else about this, or are you going to let 
your remark just lie there????  :-)

| 
| 		Bruno.  (u933234 at student.canberra.edu.au)
| 
|     "A sewer rat might taste like pumpkin pie, but I wouldn't know cos I 
|                     don't eat the filthy muthaf***a"
| 
| 


Steve Ravet
sravet at bangate.compaq.com
Baby you're a genius when it comes to cooking up some chili sauce...