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1982 931 a good year?

 
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txjake  



Joined: 17 Feb 2007
Posts: 395
Location: Oklahoma City OK

PostPosted: Tue Jan 14, 2014 9:32 am    Post subject: 1982 931 a good year? Reply with quote

Have an invitation to buy one, any pluses or minuses about this year?
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1978 924, aka The Red Rocker
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fiat22turbo  



Joined: 18 Jan 2006
Posts: 4040
Location: Portland, OR

PostPosted: Tue Jan 14, 2014 9:52 am    Post subject: Reply with quote

Well, its the last year for them and I think the majority of the problems are the usual CIS related stuff that these cars suffer from.

Improved ignition system

Exhaust manifolds are less prone to cracking.

Round TB that is rebuildable and more easily adapted for intercooling if you choose that route.

I believe they all came with 5-lug suspension by default now.

Audi transaxle is robost and can be swapped with units from 944's, etc.

Otherwise they are pretty standard 924's inside and out (cracking dashes, manual steering, manual roof, required CIS and 2.0 maintenance, etc.)

If you want one, that is a good one to go for from what I've gleaned from reading the board over the years. I'm sure someone with more direct knowledge will chime in, which might help.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)
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fiat22turbo  



Joined: 18 Jan 2006
Posts: 4040
Location: Portland, OR

PostPosted: Tue Jan 14, 2014 9:53 am    Post subject: Reply with quote

Oh and this might help:

http://www.924.org/models/931_overview.htm
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)
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txjake  



Joined: 17 Feb 2007
Posts: 395
Location: Oklahoma City OK

PostPosted: Tue Jan 14, 2014 11:50 am    Post subject: Reply with quote

Thanks. I had read that, wanted any subtle nuances from thhe forum. Pretty nice car, says it has fuel pump issues .......
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ideola  



Joined: 01 Oct 2004
Posts: 15501
Location: Woodstock IL

PostPosted: Wed Jan 15, 2014 7:23 am    Post subject: Reply with quote

The biggest issue with the 81-onward 931 is the DITC system (Digital Ignition and Timing Control). It is a primitive predecessor to the Motronic full engine management capability that followed in the 2.5L motor beginning with the introduction of the 944 in 1982.

There are three significant problems that are common with the DITC system:
1. burnt traces on the circuit board in the DITC box itself
2. faulty connections at the large harness connection to the DITC box
3. failed crank position sensor

The most troublesome of these problems is #3, as the crank position sensor is NLA, and good used ones are nearly impossible to find, and tend to be very expensive when found (typically $200 or more due to rarity). We have yet to identify a suitable aftermarket replacement.

#2 problem (harness connection) is very common, and fortunately, typically quite easy to resolve. There are a few writeups here on the forum on how to fix the issue. If I have time later, I'll see if I can dig up some references for you. But essentially, reseating the connector to the DITC box, and making sure it stays dry and well-seated is the key to trouble-free operation.

#1 problem (burnt traces) can be resolved by attempting repairs to the DITC circuit board (here's a writeup) or by swapping in a known good unit. DITC boxes are also somewhat hard to come by, although seem to be a bit more available than the crank position sensors.

I mention the DITC because in almost every case, if part of the DITC system is not working, the fuel pumps will not run. This is why one should be extremely cautious when evaluating or purchasing ANY 1981-onward 931 that is described as non-running, or having a fuel delivery problem. In my experience, it is almost always the DITC at fault, and it is often compounded by the usual array of CIS-related failures (bad WUR, bad accumulator, bad CSV, and on and on).

Other things to be aware of:
While the S2 cars had an improved exhaust manifold, they are still subject to cracking. Roughly 50% of the S2 manifolds I've inspected have been cracked. So regardless of the mileage of the car or the apparent care provided by previous owners, an S2 is absolutely no guarantee of uncracked exhaust manifold.

While the US-spec S2 has marginally more horsepower than US-spec S1 cars (156BHP vs. 150BHP to be precise), this is almost entirely attributable to the higher compression pistons, and has very little to do with (IMHO) the different turbocharger. In fact, in my opinion, the S2 turbocharger is much less desirable than the S1 because it is more limited in top-end, a significant consideration for anyone considering power-adders. The 931 in general has tremendous performance improvement potential, but I for one would not prefer to start with an S2 car. I would much rather have the more reliable (albeit more primitive) ignition of the S1 and the greater performance potential (albeit greater lag time) of the S1 turbocharger.

On the other hand, I am fairly certain that all S2 931s came with five lug / four-wheel-disc suspension, and in the US, they all came with the nearly bullet-proof Audi-based five speed (vs. the slow shifting G31 trans in the S1, which almost always needs an expensive rebuild). Still, I much prefer the G31 and have converted ALL of my cars that didn't come with one (including my NAs) because it is ultimately a stronger box, and IMO much more fun to shift and drive with the racing-style dogleg shift pattern.

The round throttle body of the S2 is an advantage, but it is a relatively trivial exercise to convert an S1 to the S2 charge tube and throttle body.

One other key advantage of the very late model year 1982 cars is that the last thousand or so serial numbers in the US got the somewhat improved HVAC system found in the 944 and 924S.

This information should get you started. I am working on a 931 buyer's guide, and I have several other posts throughout the forum detailing the differences between S1 and S2, so worth doing some searching. Hope to have the buyer's guide completed in the next week or so, and will certainly post here as well as on my FB page.
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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fiat22turbo  



Joined: 18 Jan 2006
Posts: 4040
Location: Portland, OR

PostPosted: Wed Jan 15, 2014 7:42 am    Post subject: Reply with quote

I had thought the 944 flywheel sensor was a more or less direct replacement? I could be wrong as I thought I read that somewhere.
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1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)
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ideola  



Joined: 01 Oct 2004
Posts: 15501
Location: Woodstock IL

PostPosted: Wed Jan 15, 2014 8:28 am    Post subject: Reply with quote

fiat22turbo wrote:
I had thought the 944 flywheel sensor was a more or less direct replacement?

No, the 944 sensor does not work for the 931. There are two sensors on the 2.5L car, the crank position sensor and the test sensor. Neither of them work for the 931.
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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kcoyle  



Joined: 15 Jan 2011
Posts: 712
Location: Long Island, NY

PostPosted: Wed Jan 15, 2014 9:40 am    Post subject: Reply with quote

+1 to whats been said above. My car has 944 type HVAC, 944 type front sway bar mount, 5 lug, all disc brakes.

Very nice write up of a DITC alternative.
http://www.924board.org/viewtopic.php?t=37897&sid=93431732b0678560a268962767f2e326
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Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.
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