For first hand experience of the Geartronics kit, speak to Nicholas Belling at Firman West Cars - http://www.firmanwestcars.com They are the North American agents. They use the Geartronics system on their F1000 race cars.
Regardless of whether the engine is in a bike or a car, there is no need to use the clutch, up or down - so long as the engine cut and throttle blip are timed correctly. That's where the Geartronics system scores over its rivals. Most aftermarket shifters are pretty crude bits of kit which work on fixed timers for the shift actuator & engine cut etc. Unfortunately, a gear shift is never consistent, and the shift times vary dramatically, thus rendering the cheap systems next to useless. The Geartronics system differs in that it uses a highly intelligent controller that monitors the gearbox position, engine speed and throttle position. This enables it to alter it's behaviour depending upon the prevailing conditions and how the shift is progressing. So, for example, it will only cut the engine for as long as is necessary to engage the next gear - this means there is no danger of turning the engine back on prematurely and damaging the box. Also you're not killing the engine for longer than necessary and slowing the vehicle.
Regarding matching revs and shock loadings -on the upshift, if you cut the ignition while on a full throttle, the engine speed drops very very rapidly, something in the order of 1000-1500 RPM over the period of just 10 engine revolutions. This rate of fall works out quite nicely with superbike gear ratios and pneumatic shift systems because the revs will be a pretty good match for the next gear by the time the dogs start to engage.
Downshifting is a bit more complex though. Contrary to what most people think, the throttle blip isn't just to match the revs, it's to unload the box to enable the dogs to disengage the current gear. There is less of a requirement to use engine control to match the revs because the vehicle should be braking hard during downshifts anyway. So, you don't need to increase the RPM during downshifts as much as you need to reduce RPM during upshifts.
To make fast and non-damaging downshifts you need to use quite a large throttle blip in order that you can increase the engine speed sufficiently once the dogs do disengage. This then causes other knock-on effects that must be dealt with by the electronics. The crude solenoid shifters don't have any strategy to deal with this, and as a result the downshifts are often inconsistent, agressive and potentially damaging to the box.
Things are happening so fast during a shift that it's impossible to guess or predict what timings are required. The only way to ensure consistent and non-damaging shifts is to use a sophisticated gearbox control unit. Unfortunately they tend to be more expensive than the crude timer devices (which usually come with the solenoid based systems), but you have to balance the initial extra purchase price against the cost of a transmission repair...
Neil.
