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Round 1, Fight!

 
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Alleycat_Joe  



Joined: 14 Sep 2020
Posts: 4
Location: Florida

PostPosted: Thu Sep 17, 2020 4:00 am    Post subject: Round 1, Fight! Reply with quote











This is my project 1980 931 and (1987?) 924S donor, neither running, both acquired within the last few weeks. The 931 was last registered in FL in 1997 and is the one I am pursuing a title (bonded or otherwise) for. Due to how previous repairs and maintenance items were handled on this 931, it needs some serious un-f#cking to get up to any standard. My background is in modifying (frame-stiffening, suspension, turbocharging, engine management) several 1990-2000 Miatas, maintaining a 2012 Kia Rio including engine replacement, and maintaining a 1981 Mercedes 240D. Plans for the 931 include modernizing engine management (MicroSquirt, EV-14 injectors, GM coils, universal fuel pump), replacing all broken interior and exterior bits (including locks/ignition), and simplifying. The end goal is a daily driver, with cheaper, accessible replacement parts. Luckily the 931 frame and body is 96% rust-free and seems to have low miles.

I have already:
verified timing and turned the engine by hand (with fresh oil)
found tons of hack-job wiring
found piles of rust in the tank after draining
found pitting on the top of some cam lobes and some lifters
started diagnosing wiring issues (removal of interior for ease of access)
found cracks in vacuum hoses and intake connectors

I am in the process of following the forum-approved 931 resuscitation methods. I plan to spend about $200 a month to get it where I'm happy with the end product. An estimated $2500 is already budgeted, meaning this will be at least a year long project. Keeping costs down is paramount, therefore universal parts and building my own replacement parts is the key; however a high expectation for the end product will not let cost-saving tarnish the quality of the end product.

A quick list of repairs follows:
    Purchase battery
    Timing belt replacement (water pump?)
    Check starter operation
    Fix wiring as needed
    Check compression
    Fuel tank replacement
    Fuel pump replacement (924S pump retrofit?)
    Fix wiring as needed
    Find bolts for intake system and orings/seals
    Fix vacuum lines as needed
    Decide if I try to revive the CIS or get rid of it
    Enjoy a beer after ripping out all the old engine management/vacuum lines/fuel vapor system
    Spend money & install new vacuum lines, fuel lines, engine management, ignition system
    Acquire Base Maps
    Inevitably find manifold cracks
    Replace turbo/manifold with custom T3/T4 setup (to retain characteristic boost lag)
Revision 1.0

I'm new to posting on forums and spent nearly all morning putting this post together including figuring out how to embed photos properly for maximum enjoyment. Any car advice is greatly appreciated and support is warmly welcomed.
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2038
Location: MI

PostPosted: Thu Sep 17, 2020 4:33 am    Post subject: Reply with quote

Sweet car!

I think you are right to change the timing belt first and then verify compression..

Deciding to go efi from the start may also be a wise decision but changing to a different style turbo would be a huge project without much gain imo unless you really want to fabricate a beautiful tubular manifold and go with an expensive ball bearing turbo..
The original kkk turbo setups can be built pretty easily to just about any power level you can get out of the engine, can still be rebuilt, and parts are available for them including billet wheels depending on how far you are trying to go.. For example, Iím running at 20psi on an original turbo setup but with a bit bigger compressor I got from a $120 parts turbo, built it myself, and itís not even that ďbigĒ of a compressor..

If you are thinking about power first think about intercooler..Even a stock 1980 turbocharger is fine for 15psi on all the original exhaust setup..
Intercooler is the key imo.. Then enough fuel above the limits of the stock cis, which is probably about 17psi of boost worth..
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80 Turbo - Slightly Modified
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Mike9311  



Joined: 14 Dec 2004
Posts: 873
Location: Chicago-ish

PostPosted: Thu Sep 17, 2020 6:16 am    Post subject: Reply with quote

I 2nd staying with the S1 turbo you have on this 80. It can easily handle 15psi. The compressor is larger than the 81-82. Technically the same size as 944Turbo K26/6 except the exducer (large diameter) blade tip height is taller. Really a good place to start if you need to make some part of the project easy for the moment while dealing with the rest


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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peterld  



Joined: 10 Dec 2006
Posts: 783
Location: Noosa Heads QLD Australia

PostPosted: Fri Sep 18, 2020 12:36 am    Post subject: Reply with quote

Welcome aBoard.

You're starting with a nice straight car.
Even if you had started with a near mint car you would in all likely hood be having issues with wiring/fuel/vacuum hoses etc. so you aren't really that far off.
Going to a modern fuel injection system as you're planning will cost about the same as having to refurbish the CIS system and will give you a lot more headroom.
The above guys know their onions, so a read of their posts will be advantageous.
There is so much good stuff hidden away on this Board - not easy to find, but very helpful.
Good luck with the resurrection of another 931.
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80/81 932/8 ROW
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 2006
Location: Somerset, UK

PostPosted: Fri Sep 18, 2020 1:34 am    Post subject: Reply with quote

Good luck!
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
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Alleycat_Joe  



Joined: 14 Sep 2020
Posts: 4
Location: Florida

PostPosted: Fri Sep 18, 2020 8:50 am    Post subject: Reply with quote

Thanks Eddie and Mike for the pointers on the stock turbo. I'll inspect it for wear and get it running then. Peter, thanks for your advice about the other issues. It's daunting trying to fix all of it, but if others before me have done it, I know its possible. The last thing I worked on was removing the wiper and turn signal stalk assembly. The internal plastics crumbled out of the assembly, so I will see about fitting the assembly from the 924S. The timing belt kit is in in the post, from NY to FL, so I should be making some moves and posting pictures again by the end of next week.
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1980 913 | 1981 240D 4spd
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Alleycat_Joe  



Joined: 14 Sep 2020
Posts: 4
Location: Florida

PostPosted: Wed Sep 23, 2020 11:47 am    Post subject: Reply with quote

There are some interesting finds after some 931 diagnosis. Compression is 130 psi across cylinders 1-3 at five revolutions but lower on cyl 4. It reached 113 psi after both wet and dry compression tests. I was able to see 125 psi after about ten revolutions. Does anyone have insight on what would cause this behavior? I did find a deep gouge at the top of the spark plug thread which may have been big enough to allow pressure to bypass the compression tester's o-ring, but was unable to get a picture.



The turbo is missing an oil feed line, which caused a nice oil spill during compression testing. There already seems to be a replacement in the trunk, but it looks damaged. The turbo is missing turbo-to-manifold bolts and I found a nice crack at the top of the downpipe to complement the pre-muffler crack in the rest of the exhaust.





Preliminary testing reveals about 4mm side-to-side play in the rotor shaft. The turbine wheel has no damage from what I could see; I haven't seen the compressor wheel yet. This car is easy to work on, but the turbo system seems wildly over-complicated for what it is. The oil return routing seems pretty convoluted with the oil separator/vacuum line added to the return, and the external wastegate system sure has a lot of failure points. In fact the whole car has way too many connections and failure points, each adding to the overall complexity of repair and diagnosis. I sure am glad to be simplifying this car and going down a modernization route.



The following picture is another gift from the P.O. He chopped all the wires off the back of the ignition barrel and replaced them with his own "clearly superior" solution to starting the car. I'm honestly surprised his push button starter worked with all the exposed wiring. I just hope he didn't try to completely bypass the DME relay, but a lot of his signature wires are sticking out of the back of the fuse panel where the relay is missing. I also finally found out he wired his own fan switch for the radiator, anyone know why he would do this? Surely not overheating issues.



This wiring debacle is going to be a bigger headache than I bargained for.
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1980 913 | 1981 240D 4spd
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 2006
Location: Somerset, UK

PostPosted: Wed Sep 23, 2020 5:37 pm    Post subject: Reply with quote

PO bodges and lack of maintenance is the first largest hurdle to overcome resuscitating and dead turbo

Over complicated turbo install? Maybe, but it was relatively new technology on production cars back in the day

Compression testing - #4 is often the weakest cylinder due to bore wear, detonation damage, heat damage, broken rings, scored bores, head gasket failure, leaky valves ...... pick any one or more of those

Cracked manifold means at least the head has to com off as the manifold often cannot be repaired insitu or be removed without head off or engine out.

Some fixings and parts are still available from Porsche. Some will need new alternatives.

Your sticking point of modernising the turbo will be the 3 bolt turbo mounting to the manifold. Not impossible to update but will need some bespoke fabrication to change it. Its been done rarely, but you could weld on a new flange to the manifold, but you will have a knock on affect to exhaust, J pipe, WG etc. etc.
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
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Mike9311  



Joined: 14 Dec 2004
Posts: 873
Location: Chicago-ish

PostPosted: Wed Sep 23, 2020 10:44 pm    Post subject: Reply with quote

...and at least you have the later variation of the drain line. Unless you go modern and mount a turbo higher, you need that vented drain line since the turbo is mounted so low.
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2038
Location: MI

PostPosted: Wed Sep 23, 2020 11:15 pm    Post subject: Reply with quote

I think the vented drain line might be a bandaid for a lot of blowby and crankcase pressure..
I have virtually no blowby, no oil on filter ever, no smoking ever, early drain tube, no problems..

You can get a rebuild kit for the turbo for less than a hundred bucks if your comp wheel and turbo pistons arenít damaged or too worn.. Could try it diy or send it in for a rebuild.. Its pretty simple in there..
The expensive part is the turbine wheel/shaft if itís too damaged and you basically have to cannibalize one from another k26 or a shop told me like almost $400 for one once..

You could just make it run to see what you have to work with as far as engine internals but that shaft play sounds not good and if you have 4mm side to side I imagine the wheels have been hitting..
Aluminum evidence in the oil/grime inside your intake tract?

How far are you willing to go if your engine/turbo are in bad shape?
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80 Turbo - Slightly Modified
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