Need Sportomatic education

[Shuie]

okay, Im ignorant. What is a sportomatic and how is it different from an automatic? Is it the same idea as a tiptronic? Can a modern 8:31 gearbox be converted to a sportomatic? What kind of mods are done toa car to convert it to a 'Sportomatic'? How impossible are the parts to find?

[Grady Clay]

Sherman,

Quick & dirty explanation:

There are two versions of the Sportomatic; the 905 based on the 901 transmission and the 925 based on the 915. The 905 was a 4-speed but the 925 had both 4-speed and 3-speed versions.

In short it is a regular transmission with a pneumatically operated clutch and a torque converter. The clutch is operated by a micro-switch on the shift lever which operates a control valve that, in turn, controls vacuum to a diaphragm to operate the clutch release bearing. The torque converter is a regular automotive type except it doesn’t use ATF; it uses engine oil supplied by a small oil pump on the forward end of the left cam. The transmission itself is very similar to its regular brethren and shares many parts.

It is an all-mechanical system. There are some electrical parts and interlocks but no computer.

While complicated appearing, it is actually relatively simple and reliable. Most Sportomatic devotes that I know scavenge every used and NOS part they can find. To convert a 911 to Sportomatic is best done with a donor car. When people convert from Sportomatic to a normal transmission they rarely remove everything.

If you want to see a FULL engine compartment, look at a MFI, A/C, Sportomatic. You drop the engine and transmission for much regular service. Only a Turbo with A/C has more stuff in the engine compartment.

An E50 Tiptronic is an entire ‘nother story. It is a proper automatic transmission with very sophisticated computer control.

2c

Best,
Grady

[Shuie]

thanks Grady

[Fishcop]

Go the Sporto!

Grady has described it really well. I keep telling myself that I'm going to change out my Sporto for a 901 manual, but the fact is i can't break the bloody thing! Mine's handling my RS spec 2.7 with no trouble and I've actually started to really enjoy it at the track as it is driven just like a manual, but with left and a right or "stop" and "go" pedals only it's very easy to balance the car and set the car up for and through corners. Having a torque converter in the system also lets you "cheat" some corners by allowing you to drive through in too high a gear (if that makes sense?).

I've heard of a few people setting up sportos from manual configurations... I even read of one gentleman who lost a leg through an accident and set his 3.2 up with a sporto and changed the gas pedal to the left side of the brake pedal to suit the loss of his right leg!