sequential gearboxes

[Simon & Heidi Young]

> 
>         " Shift without lift " sounds good and i have
> heard a little about it, is this where the engine
> management system reduces engine rpm by cutting
> cylinders during a gearchange ?

	Sorta.
	With a dog ring box you can't shift without unloading the box.  The dogs
have  a back cut which locks the gear and dog together under load. SWOL
senses the load  in the shift lever and unloads the box, letting it change.
 The exact details of what happens I could never get the engine guys
(Cosworth) to tell me but from what I've seen it is little more than the
equivalent of backing off the throttle and getting right back on as you
would in a normal clutchless change.
	The turbo engines have a "ninth" butterfly between the turbo and plenum,
this is controlled by a servo motor via the ECU, the throttle cable acts on
the main butterflys and IGV (inlet guide vane, a system to keep the turbo
spooled up while the throttle is closed).  In action SWOL simply slams the
ninth butterfly closed and open again, enough to free the dogs and let the
shift proceed. There may be a spark cut but really it happens so fast I
doubt that it is necessary.
	How things are handled on NA engines I'm not sure.  I have seen one
article in a local boy racer mag describing how to set up a flat change by
sensing clutch depression and activating a rev limiter while you shift,
dodgy at best.


	Simon
	Sunbury, Australia