SPOautos

Ahhh, yea thats true....I just wasnt thinking about it real hard haha

I was doing good just to remember the go cart, it was like 2+ years ago when I saw it

STEPHEN

Shad Laws

Hello-

Actually, automatic clutching with a synchromesh tranny has been done before! In 1968, Porsche released a "Sportomatic" and VW an "Autostick." They are essentially the same thing, and deserve an examination. Let me explain...

Nowadays, we have these things called "Automatic stickshifts" or whatever the marketing guys want. They are basically an AUTOMATIC transmission that you manually control the shifting of... physically speaking, they still have wet clutches and brake bands, planetary gears, etc. The Autostick and Sportomatic are NOT like this.

The Autostick and Sportomatic are a MANUAL transmission with an automatic clutch. Here's how VW and Porsche decided to "make" one. Take a regular synchromesh manual transmission and clutch, complete with shifter and all. Then, add a torque converter between the clutch and the engine. Finally, rather than use a cable or hydraulic line to pull the clutch in, they use a vacuum canister with a big diaphragm in it. One side of the diaphragm sees ambient pressure. When the other side sees ambient, the clutch is engaged and the car moves. When the other side sees vacuum, the clutch is disengaged and you can shift just like normal.

Now, how do you control this? Well, they had a novel (and completely low-tech) idea: use the shifter! The shifter has a pair of contacts in it. When you apply pressure to the shifter to switch gears, the contacts touch and send a signal to shift. When you release the shifter, the contacts disconnect and stop the signal to shift. It sounds crude, but it works pretty danged well.

Then, in the back, you have a device that connects to an ambient pressure vent, your intake manifold, the clutch servo (the diaphragm-containing gizmo on the tranny), and a vacuum tank (about the size of a coffee can). This device is the key to operation. When there is no signal from the shifter, the clutch servo is connected to the ambient pressure vent. When there is a signal from the shifter, the clutch servo is connected to the vacuum tank. Also, as a secondary function, it controls how the vacuum tank is filled... only when your intake manifold pressure is really low does it open the manifold to the tank to "fill it up" - just a slightly-sophisticated check valve sort of thing.

Now, when you grab the shifter to shift, the system instantly connects the vacuum tank and clutch servo together with large-sized lines (~1/2" diameter or so) and pulls it open. This disengagement is FAST. When you release the shifter, however, the disengagement speed is slower... this is because the vent to ambient pressure is a smallish orifice whose size you can adjust. In other words, you can tune it to engage/disengage quickly (rough) or slowly (smooth) depending on your preference.

This solution is completely low-tech... only one simple solenoid and no computers are needed. Of course, it doesn't have much sophistication, either :-). VW and Porsche put a torque converter in there, too, for two reasons. The first is that it helps to start and stop the car. You leave it in gear at stop lights just like an automatic, and the torque converter takes over starting and stopping problems. The second is that it smooths out harsh engagements of the clutch.

Now, how can you adapt something like this to an FD? Well, first of all, you really don't want to use a torque converter - that's a pain in the ***. But, fabbing up a clutch servo and stuff isn't hard. I'd make it so that it acts independently of the clutch pedal... kinda like a cruise control. So, you can use the clutch pedal OR the clutch servo to disengage the clutch... whatever one is "more disengaged" wins the battle and the clutch moves appropriately. This allows you to still control starting/stopping with the clutch pedal, eliminating the main need for a torque converter. Then, you setup the shifter just like I described so when you go to shift, it automatically disengages and engages the clutch for you during shifting. Finally, you get a custom ECU that has "launch control." Most of these are basically just a new redline... if a switch senses that the clutch is in (or the shifter contacts are contacting in our case), then the redline is dropped to, say, 4000rpm. So, when you're on the track and you shift at 8000rpm, the ECU thinks the redline is now 4000rpm and cuts fuel until it drops the rpm... only usually the shift is so fast that it never gets that low :-). It's also useful for launching, hence the name... when the clutch is in, even WOT will hold the 4000rpm or whatever for you.

Of course, the system I just described would work very well for a dragstrip and perhaps/maybe "okay" on a road course (it would still require the driver to match revs and/or double clutch to avoid major jerking during downshifting), but would be completely inappropriate for street use unless you crammed a torque converter in there... and that'd just be annoying.

Just some food for thought :-).

Take care,
Shad

sevenin7

Someone with ikeya seg shifter in car ( USA fd ) ?

bigmack000

son of a bitch poset on the thread i searched for hahah