V-box: 915 shifting speed - 0,2 sec?

Ole Petter · 10-23-2008, 11:48 PM

Hi all! Following up on the thread where the 915 gearbox was introduced as: What was Porsche thinking of?

I was lucky enough to have an Performance V-box "strapped to my car" the other day for some action. The owner of this box analyced the results and he was rather amazed by the shifting speed! He claimed a 0,2 second shift (I shifted throgh 2. and 3. gear). I told him I just couldn't believe what he was saying! His reply was - "it is all here on the print-out".

To me this sounds just "too fast" - does someone has the same experience? Maybe this person was confusing the numbers?

My car is a 10/74 S.

CharlesJones · 10-24-2008, 05:13 AM

Maybe you're just a very good driver! It does sound way too fast to me though - my 915 is set up great, with no crunching or baulking, but it still ages to change gear. I would have thought you would have needed some sort of racing crash box to change gear in 0.2 of a second!

What is a V-box? And how does it work out how long a gear change takes? Maybe the 915 takes soooo long to change gear, that the V-box is getting confused and is interpretting something else as the gear change.

Ole Petter · 10-24-2008, 06:02 AM

I don't know the details about a v-box, but it measures distance and speed very accurately. As I understand it there is a graph showing each gear, with the power curve and the time and distance. So where the graph dips, there is a gear-change, and where it goes up again, the power is on again, and therefor the next gear is in place. Something like that.
Anyway, he sounded like he knew what he was talking about!
I would think a shift-time of 0,5 seconds would be an ok time, but I am no pro...

Geary · 10-24-2008, 06:22 AM

An H-pattern dog box can be shifted at .25 seconds. How can a synchro box be shifting quicker than this?

id911T · 10-24-2008, 08:19 AM

Quote:

Originally Posted by Geary

An H-pattern dog box can be shifted at .25 seconds. How can a synchro box be shifting quicker than this?

Depends on the transmission. The box we used in our last hybrid competition vehicle was capable of .18s shifts from 3rd-4th with a good driver. It's a plain jane GM F40 6 speed fully synchronized manual trans.