Sequential gearbox question

[David]

Complete newbie, I was wondering what the transaxles that come with sequential shift are like for a road legal car. I can see how a sequential racing shifter that is designed to shift at max rpm copes. But how does a sequential shifter that's part of a transaxle and has no connection to the engine ecu figure out how quickly or slowly to engage/disengage the clutch . I would have thought any aftermarket sequential box wouldn't be happy with lots of normal road driving. Do the aftermarket boxes and shifters get engine info as well?

[Tim Kay]

David,

From my experience with a Fortin sequential in an off-road car using it on the street would not be a problem at all. A manual sequential isn't any different than a standard h-pattern in the sense that you still have a manually operated clutch. Your technique in shifting has to be a little more purposeful but you still have the option of using your clutch to smooth the transition from gear to gear or not use the clutch at all.

Having a sequential like a Fortin or Mendeola gains an advantage by having dog ring straight cut gears thus positive quick shifts along with strong components but crazy noise! You wouldn't believe the racket these trannys make.

It's possible to add a momentary switch to your shift lever that will send a message to, say your Motec ECU, that will drop your rpm at the precise time of the shift so you can keep your foot on the throttle but I suspect that would be required more for racing than street driving and clutchless shifts.

Can't comment on the more sophisticated electronic controlled sequentials other than I have a BMW M6 with the electronic\hydraulic clutch sequential gearbox which is seamless at any speed.

I'd love to hear from anyone that has driven one of the Porsche GT3 Cup cars which come with a 6 speed sequential. Some have put that trans in the street legal GT3 RS.

As far as for a GT40, I went down that road a couple years ago. At the time Fortin and Mendeola could not be used due to the length. I don't know today if that has changed or maybe another manufacturer has come out with one that will fit, ie ZFQ

[EGLITOM]

how about inverting this one ?

Porsche 996 GT3 Umrüstsatz auf sequenzielles Getriebe - Albert - Motorsport

TOM

[Pablo]

The sequential shift lever has a "strain gauge" that senses the miniscule bend in the lever whenever a shift is made. This triggers engine managment to provide a short (0.08-second) ignition retard during clutchless shifting. The clutch is usually used for 1st-2nd and 2nd-3rd upshifts, as well as downshifts.

For street sequential transmissions, helical gear teeth are used rather than straight-cut. This eliminates the load gear noise that is typical of full racing transmissions. (Some gear strength is sacrificed for quiet operation.)

Unlike typical helical street gears, sequential street gears maintain the large engagement dogs (rather than small synchro teeth and synchronizers).