The RT2000 car I drove at Skip Barber had a sequential shifter.
It works just like a motorcycle gearbox. When you pull on the lever, you go up one gear. When you push on the lever, you go down one gear. In neutral, a light comes on.
The main advantage in that you do not have to push in the clutch during upshifts. Just lift off the throttle, pull on the stick, and back on the power. It takes very,very little time to upshift.
On the downshifts, you need to use the clutch (most of the time), but the shifts are still faster than a H pattern shifter.
As far as double clutching goes, it is completely unnecessary and a waste of time. Modern gearboxes with synchros do not require it at all.
That being said, I like the H pattern (with shortshifter) in my streetcar, and would prefer a sequential only in a race car.

 

Guys,
I feel like we are fighting on the same team .
I said I dislike the unit and you guys are arguing that you dislike it....its not really arguing its agreeing
Some people like it, some don't just like any product out there...I may work for the company but I personally dislike it (being totally honest). Like I said I have one customer that loves it and would not have the car any other way...he swears by it...
To each his own

 

Double clutching is fun!

Also smooths out the downshift, especially when you're trying to rev-match going into 1st to take a hairpin.

 

OK, what's double clutching?

 

I believe the Cartronic sequential was originally developed in Czechoslovakia. Apparently, some parts are now manufactured in Germany, although assembly takes place in the Czech Republic.

There was a recent article in Excellence about this "SQS" shifter.

 

Example going from 4th to 3rd
Off the gas
Clutch in
Shift into neutral
Clutch out
Blip the throttle
Clutch in
Shift into the 3rd
Clutch out
Back on the gas.