Moved onto motorbike engines since having my Ibiza and onto dog gear designs and shifting strategies. To get a shift from one gear to the next, you have to unload the dogs, move the dog ring over as fast as possible so there is no dog-to-dog impact, and then reapply the power only when everything is fully engaged. Too early it will knock the edges of the dogs. Numerous strategies for loading and unloading, throttle lift, shift cut, ignition retard, torque reduction etc. Get it all right and you can clutchless flat shift in under 20ms with a pneumatic shifter. More power tries to pull the car out of gear so undercut dogs helps to keep the car in gear. But then undercut dogs slows dog release at the start of the shift. Its a balance. These lads do very very nice bits https://novaracing.co.uk/.
Most fancy motorcycles now come with clutchless upshifting and down blippers out of the box. First bike I rode with what I'd describe as a good fully integrated clutchless shifting was the BMW S1000R iirc, but they've all caught up now. Quite uncommon for us to see gearbox failures, used to change a lot of R6 2nd gears back in the day though!.
True, bike boxes are really nice in most cases. I tend not to use the clutch 50% of the time for up changes on a bike, if its not a single! as Rob says you just feel the load fall off the dog and if you flick it quick it just drops in to the next gear with no fuss, but so little inertia on a bike engine it's easy. You can do down changes quite nicely as well, but you have to concentrate and be tootling about rather than on it, as if you get the timing wrong it won't change and missing down shifts isn't fun at speed lol.
I have fitted a throttle motor to my Hayabusa engine as a fly-by-wire system, so the ECU uses that to throttle match on the downchange, so clutchless up and down. Almost seamless changes result. ECU wont allow a change if it results in an over-rev so thats a good fauil safe on a fast changing system to not select an extra downchange and buzz the motor. Have also fitted a modified shift barrel so that Neutral is at the bottom, so you dont have extra distance to move the change going from 1st to 2nd (as in MotoGP/WSB bikes). Mega tech on a bike engine. Cassette gearbox would be nice as on some bikes but Busa doesnt have that, but on the plus side is a very strong box. EGAS motor https://store.jenvey.co.uk/throttle.../electronic-actuator/electronic-actuator-eta2 Pedal unit https://sbdmotorsport.co.uk/product/egas-p-01-sh-bosch-pedal-unit/ EGAS has all kinds of uses, can be used in traction control for lessening the severity of power delivery by slowing throttle opening.
Seen a few engine failures (connecting rods/ big end bearing failures) due to mechanical over-revving (dropping down the gearbox too fast).
Motor of this level should should have a slipper clutch though, surely? Never ridden a bike with a slipper clutch, but I imagine you can go as quick as you like and the clutch will keep the motor in one bit....within reason? Maybe the Busa is a bit before they slipper clutches became std....or maybe they don't work with the added weight of a car to lug about?? But I can imagine without one it would be a problem.
Slipper clutches not used on car applications, in fact mods are made to the Busa clutch basket to remove any 'slipperness'. Think its something to do with getting off the start line better, or maybe even some issues at very high revs. Not totally sure but its a common mod to remove the stock slipper clutch bits and lock it all solid. So you need to watch too many downchanges as it will go in......and with a paddle shift system its easy to call up too many too quickly. The ECU prevents that.
RobT, how did you get on with your flat shift box, did it take much fettling to get to your 2ms? Did you try and shorter?
With a VW manual box I doubt you will get less than 150ms just due to all the slack in the system and the fact there is no gear position sensor telling you where the gear shift rings are. On the sqs box I think I had it set at about 200ms shift cut. On race boxes that have a proper shift barrel and a sensor attached to that barrel, under 20ms is easily possible. I will post a couple of data logs to show this as my ECU logs shift % complete.
Cheers RobT, will work my way down to around 200 from the maximum, fitted an Sqs kit to my 02t gearbox for the last rally but didn’t use the ignition cut box, all wired up now so will give it a whirl
Its terrifying first time you use it, like its all going to go wrong, but you have to be comitted to make it work
