Strange Gearbox Auto vs Semi Auto

Hawk Tuah · 5 Oct 2007 at 15:44

Ok, I've noticed an odd one with the auto box on the Jazz.

Ok, in full auto mode, cruising at 70 the car should be in 7th gear. If I click it into semi auto mode, its still in 7th gear, but the revs go up.

Now I'm confused, does that mean that in full auto mode there is another 8th gear?

I videoed it last night....

http://www.bugone.co.uk/RPMChange.wmv

Born_2_Kill_83 · 5 Oct 2007 at 15:47

Lol thats weird as...
It has to be dropping it down a gear :confused:

Lashout_UK · 5 Oct 2007 at 15:47

You'll probably find that like most autoboxes, there's a torque convertor lockup that usually operates on top gear (i.e. 7th) - it's for economy purposes.

When you manually engage 7th, this lockup drops out and the convertor slips, as such the revs rise.

Rilot · 5 Oct 2007 at 15:49

It's because it's not actually got any gears. It's a CVT box in that car IIRC which is two cones and a belt that varies the gear ratio continuously.

The 7 "gears" you can select are virtual gears that are just pre-set ratios of the cones and belt.

Lashout_UK · 5 Oct 2007 at 15:50

Ah yes, you should have said it was the CVT one to start off with

Hawk Tuah · 5 Oct 2007 at 16:06

Rilot said:
It's because it's not actually got any gears. It's a CVT box in that car IIRC which is two cones and a belt that varies the gear ratio continuously.

The 7 "gears" you can select are virtual gears that are just pre-set ratios of the cones and belt.

Ah. That would explain why the gear changes are pretty smooth then.

Thanks for the explanation.