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[plasticbaldy]

Can somebody please tell me what changes were made in 1981 over the 1980 931 ?

[Benski]

In the US, the 1981's had digital ignition, a different exhaust manifold (i think?), a more reliable turbo, and an Audi transmission that was eventually put in the 944.

I'm sure I am missing a few things (don't have an 81 ...)

As for the rest of the world - I don't really know. I know a lot of countries kept the Porsche transmission until 82 or so.

_________________
76 924 (white), 78 924 (red and automatic)
80 924 (silver), 80 924 (dual carbs, snailshell)
2 80 931's (red + burgundy)
85.5 944 (being fixed and sold for cash)

[ This Message was edited by: Benski on 2002-05-18 15:28 ]

[924RACR]

From the Porsche 81 Service Information:
Major mods concerned enigne and ignition system... new ignition system, changes to fuel system, and increased CR have increased engine power... built with the M 31/04 engine (US/Canada) with 115kw/154hp SAE Net, was formerly 110kW/143 hp SAE Net.

Pistons have a flatter, centric recess than before. CR is up from 7.5:1 to 8:1.

New flywheel with milled teeth for the digital ignition.

Crankcase venting appears to be different, as also oil line return - different plumbing.

Turbo unit is a new refined version of the previous turbo... vanes on compressor changed for better efficiency... smaller turbine housing for better engine pick-up @ lower RPMs. Different gasketing. New wastegate, but same boost levels. switched to single-bore throttle body. Pressure tube and intake changed correspondingly.

fuel injector holder is changed for better sealing.

Ignition is now a crankfire fully electronic system, uses distributor only for spark distribution.

Details of changes to the ignition and fuel system are extensive, will not repeat here.

Has stronger 25mm drive shaft in torque tube. Is equipped with the 5-speed from the '80 924 (016/9 MF) with several mods - trans code 016G for US and Canada. Differences as compared to trans type 016/9 MF:
larger input shaft 25mm for connection to 25mm drive shaft
input shaft runs in 4 bearings
new seal for input shaft to match 25mm dia, sealing tube for input shaft/trans case is omitted
new trans case revised for 4 bearing input shaft
ring/pinion gear ratio is 9/35
3rd gear ratio is 24/35
4th gear ratio is 28/31


_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[gohim]

The differences between the 80 and 81 exhaust are changes in the types of seals to improve sealing. 80 engines had a series of flat gaskets to seal many of the components of the exhaust, turbo, and wastegate. The 81 and later cars had many of the flat gaskets changed to aluminum sealing rings, which required the related flanges to be grooved to create a seat for the crush type aluminum sealing rings.

The Throttle Body was also changed, 1981 model year had a single large barrel, and 1980 had a two smaller barrels.

The Oil Breathing/Separation was also changed on the 81 and later models to try to reduce oil burning. 81 models have a line running to the top of the cylinder haed that was not installed on 1980 models. There was a retrofit, and a Factory Campaign to install this kit, but it ended long ago. The kit once sold for around $200. The individual parts sold for over $350 the last time I checked. A friend of mine lucked out 10 years ago when I found a kit at the Pomona Swapmeet for $75, otherwise he would have been out another $300 (kits had already been discontinued for years, even at that time). That gives you an idea of how long it has been since the complete kits were offered by Porsche.

[friskynibbles]

my '81 931 has a beautiful drive shaft. i was quite impressed when i saw it's condition.