active 915 tranny?

lonewolf · lonewolf's Garage

at the track a fella said he was running a 915active transmission.
what,s the difference? and advantages?
does it have the same shift pattern ?
you couldn,t hear the shifts ,they were very smooth and quik.
what,s the cost difference?

anyone know
thanks

BlueSkyJaunte · 10-01-2002, 12:02 PM

http://www.phii.net/new/gears.cfm

TimT · 10-01-2002, 01:06 PM

An active transmission means the gears have been optimized so all gears can be used effectively. 901's, 915's etc have top gears that are usually much to tall. On certain tracks you cant use 5th gear, the engine drops out of its power band, and you lug along not gainng more speed.

In active trannies gear selections are based on the top speed desired, the engines effective powerband, redline, and even the track the tranns will be used at. Some of the big buck Club Racers have extra trannies, with tall gears, with short gears that they have installed as needed

Early_S_Man · 10-01-2002, 01:19 PM

The concept certainly isn't new ... in fact, it was precisely what Mark Donohue was suggesting for the 911E and 911S models in his 1969 test for Car and Driver!

Unfortunately, the Powerhaus II folks choice of the word 'active' in their marketing is a bit misleading, since most people associate that word with electro-mechanical/'smart' technology, these days!

Oldporsche · 10-01-2002, 01:33 PM

Active="Use all of the gears"

Early 911's using the 901 gearbox used terms such as "airport gearing" or "hillclimb gears". Essentially an optimum gear selection within the gearbox for the use of the car.

old stuff for porsches, new terms for marketing!

Good luck,
David Duffield

BlueSkyJaunte · 10-01-2002, 02:09 PM

Reminds me of the 911R featured in Excellence some time ago--had the same ratios 4th and 5th, in case one of the gears blew out!

Jim Sims · 10-01-2002, 02:16 PM

"in case one of the gears blew out." I wonder how long a transmission would continue to function before the rest of the gears "blew out" from the metal debris (dog teeth, brake bands, energizer and anchor blocks) in the housing and gear oil?

Jim

Early_S_Man · 10-01-2002, 02:31 PM

Actually, the 'spare' top gear was an idea based on test bed runs prior to oil coolers and spray-jet application to the transaxles ... engineers knew from galling of the fifth gears of disassembled test subjects ... that the fifth gear was likely to fail during the 24-hour endurance run for FIA records ... so the idea of the 'redundant' gear was born, and the pairs were alternated, by the hour, so neither would fail. The engineer that dreamed up that solution ... got a case of champagne after the record-setting 911R run!

emcon5 · emcon5's Garage

Quote:

Originally posted by Early_S_Man
so the idea of the 'redundant' gear was born, and the pairs were alternated, by the hour, so neither would fail. The engineer that dreamed up that solution ... got a case of champagne after the record-setting 911R run!

Isn't it amazing how such a simple idea is so brilliant?

Tom

Roland Kunz · 10-02-2002, 09:45 AM

Hello

The dual 5th speed gear trany was used on the record seting run at Nardo where the car was runing constant WOT for hours.

This tranys wheren´t used on races.

Grüsse