Answer to the 6-speed, Auto, SMG debate?!?!... - The Unofficial BMW M5 Messageboard (m5board.com)

Yupkwondo · 13th February 2003, 06:53

After all this SMG, Auto, 6-Speed debate...what would be the possibility of a transmission that could do both or all three. From this point on, SMG is SMG and Automatic since it has an Auto mode in it, just for comparision purposes......

Anyway,I know it's not in development,(well as far as I know) but if you thought about it, I don't see how hard it could really be. (Take that in terms of what they have accomplished already, it's way to hard for someone like me to develop)...Anyway, as I see it, one would need a dual cylinder clutch, one for the pedal, and one for the SMG. The computer could control which one works when, through a pressure release valve, that switches to whatever one needs the pressure at that time. And you would need a way to change from a stick control, to servo activated gear changes. Again, I'm sure there is a way to do this. A "7th gear" where you put it and the servos/pneumatic valves that do the actual gear changes start to work. I think that would be the ultimate way to progress, the two in one possibility of full manual control, and true race inspired SMG!!

Or, as another way to develop the system, you could have a manual/stick that is drive(Shift) by wire. As you move the stick the computer uses sensors, to control the transmission through already controlled means that a SMG has. SMG already has different speed controls, and the car has enough computing power to know/learn how to work the clutch with a variable input, not just given parameters. Using this method there wouldn't have to be a way to switch from true manual to SMG manual, it would all be SMG components with even more User interface.

Or it could even then have a "button clutch," full clutch movement, and feel however the computer would again sense position and react in the way it needs to, so it could accuratly reproduce your clutch pedal movement in the transmission. So if the processor does 1000 positions per second, there would be no way to know what was controlling your clutch activation. Then when you goto true SMG mode (again the "7th Gear") you goto the fully manual paddles on the wheel,and the 5ms shifts, or what have you. Or if you want the Auto option for putting around town.

If I had the development money, I would truly pursue this idea, as I feel that it would be an enthusiast dream, well as long as they aren't a purist and an enthusiast!! There would be a lot of develoment just as far as computer programming is concerned, but I believe that it is actually something that could be accomplished.

~ Jason
2001 Lemans/Lemans

P.S. Sorry guys I cross-posted this to get more traffic, because I wanted to know what people really thought.

CEC · 14th February 2003, 22:09

I don't know why you would want such a system. For me it is either SMG OR stick. Adding complexity - something else to break - and weight - plenty of that already - makes little sense. I would rather see the engineering dollars spent on perfecting SMG and/or improving the present 6-speed transimission (heftier clutch, shorter throws).

Artur Costa · 14th February 2003, 22:59

Yupkwondo ,
I think that system exists in the WRC cars.I once saw that the WRC cars have a clutch to launch easier!
And at some spots they need to press the clutch to leave the car on "free roll"

Dunno if this is 100% but I hope someone backs me up!

TCM · 14th February 2003, 23:20

Arthur:

I will venture out and back you up as I saw a piece on the WRC Sweden Rally last night. They did a focus on the Suburu gearbox. A clutch is used to start from a stop and a traditional H-gate shift pattern is used but no clutch is needed to switch gears. This allows the driver to go from say 6th to 1st after a spin out instead of having to flick a paddle 5 times to downshift. Pretty smart, I would not be surprised to see some production cars adopt this transmission style. Of course, the transmission cost $50,000 I beleive

.

pmiranda · 14th February 2003, 23:28

I know that CART cars have a sequential manual tranny - all mechanical, but they can "shift without lift" because the engine management cuts spark when they move the shift lever. I'm not sure if it blips the throttle for them on downshifts or not. The point is, they only need to use the clutch for starting and stopping. Rev matching for shifts are done electronically but they still have direct manual control of the transmission. I think most Rally gearboxes are/were like that, usually with a fore/aft level to the side and either a hoop or paddles behind the wheel to duplicate it according to driver's preference.

MIB · 15th February 2003, 03:24

Didn't they have something in Europe years ago, where you could move the lever first, but it wouldn't select until you depressed the clutch.

Similar concept for racing. The driver can approach the corner, down shift early, then have both hands back on the wheel, then dip the clutch after all his hard braking, and he will then be in the gear he had selected ealier on.

Eg. Still coming down the straight in 6th. Move lever to 2nd, start braking hard, tap the clutch and your in 2nd.

Nybes · 15th February 2003, 16:18

Yes MIB,
It was called the pre-selector gearbox. It was on some French cars and I think also some limited US cars (Cord?)
N.

DavidS · 17th February 2003, 20:34

Rolls-Royce had it in some 1940-1950 models, if I remember correctly.

David