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Early '80 931 Turbo ISSUES/PROBLEMS
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Gatornapper  



Joined: 23 Oct 2021
Posts: 155
Location: VA

PostPosted: Sun Dec 05, 2021 12:36 am    Post subject: Early '80 931 Turbo ISSUES/PROBLEMS Reply with quote

Just read this today - missed it earlier - just a bit upsetting (from here -
http://www.924.org/techsection/Boost924and944.htm) :

"The cylinder head was a new piece and had an improved combustion area and revised porting and repositioned spark plugs because of exhaust manifold clearances and heat generated in the turbo area. The engine also received a new oil cooler and thermostat to aid in reducing oil temperatures. But there were a few probems with the system. The oil feed to the turbo was routed close to the exhaust manifold. When engine temperatures soared, the oil in the engine and the feedline cooked, which in turn led to premature turbo failure.

Most early turbos had to be rebuilt or replaced at less than 60,000 miles.] Labor was 8 to 10 hours and the exhaust manifold usually had to be replaced. Those wanting more perfromance had to fiddle with some questionable aftermarket parts that modfied the wastegate for more boost.

Porsche realized these shortcomings and for mid-1980 went to an improved ignition control and revised turbo and intake tracts. This yielded a full 45 horsepower over a standard 924 and was more reliable than the 1979-80 924 Turbo setup. The engine breather system was also revised to decrease head gasket failures and oilvapor generation."


QUESTION: HOW MUCH OF AN ISSUE IS THIS? Is my 931, built in 6/79, a LEMON because of this issue? Has 58k original miles on it, turbo is clearly original.

Should I just get the car running well and sell it, and find an '81 or '82 with their timing sensor issues?

TIA,

GN
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924RACR  



Joined: 29 Jul 2001
Posts: 8546
Location: Royal Oak, MI, USA

PostPosted: Sun Dec 05, 2021 10:35 pm    Post subject: Reply with quote

Get it running and enjoy it!!! Rebuild the turbo when needed, just run synthetic in the meantime and be sure to let the turbo cool with idling for a little bit before shutdown.

The biggest challenge IMO for the early Turbos is the gearbox... and even that can be fixed, if the trans is too beat up, by swapping in a 944 torque tube and 'box. Of course, it's also a key part of the character of those cars, so I'd want to try to keep it as much as possible.

Everything else can be fixed, changed, or dealt with.
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Gatornapper  



Joined: 23 Oct 2021
Posts: 155
Location: VA

PostPosted: Mon Dec 06, 2021 11:35 am    Post subject: Reply with quote

Vaughn -

Thanks for the encouragement. Just put Valvoline VR-1 in engine but will revert to Mobil 1 in next change. I've been using synthetics almost exclusively since 1977, but many think they don't do so well in older engines.

Will do on letting the turbo cool.

Not so worried about gearbox if all is well with it - I'm used to the pattern in my 914 that I restored and drive regularly. I've read several places the later 944 torque tube & box is not an easy swap at all, so I hope to not do that, but keep original.

While I'm a decent mechanic with a full shop, I've read that a turbo rebuild must be done by the experts and is very expensive.

Your thoughts?

Thanks!

GN

924RACR wrote:
Get it running and enjoy it!!! Rebuild the turbo when needed, just run synthetic in the meantime and be sure to let the turbo cool with idling for a little bit before shutdown.

The biggest challenge IMO for the early Turbos is the gearbox... and even that can be fixed, if the trans is too beat up, by swapping in a 944 torque tube and 'box. Of course, it's also a key part of the character of those cars, so I'd want to try to keep it as much as possible.

Everything else can be fixed, changed, or dealt with.
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chuck21401  



Joined: 20 Feb 2005
Posts: 444
Location: Annapolis, MD

PostPosted: Tue Dec 07, 2021 12:09 am    Post subject: Re: Early '80 931 Turbo ISSUES/PROBLEMS Reply with quote

Gatornapper wrote:

Should I just get the car running well


IMHO that's the first step. Somewhere along the way you might consider adding a boost gauge, at least temporarily so that you can determine if the wastegate is operating properly.
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924RACR  



Joined: 29 Jul 2001
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Location: Royal Oak, MI, USA

PostPosted: Tue Dec 07, 2021 12:52 am    Post subject: Reply with quote

Removing and installing the turbo with the motor in the car is a massive PITA, but do-able - I've done it numerous times. But the actual rebuild of the turbo itself definitely needs a legit turbo shop to be done right - because balancing at high speed. Worth considering an upgraded compressor wheel while in there, if you need to go that route.

The trans swap isn't that big a deal IMO - just a big disassembly. Fortunately, going that direction ends up being simpler, not more complex (mainly in shift linkage). If it becomes necessary.
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Gatornapper  



Joined: 23 Oct 2021
Posts: 155
Location: VA

PostPosted: Tue Dec 07, 2021 2:18 am    Post subject: Re: Early '80 931 Turbo ISSUES/PROBLEMS Reply with quote

Great idea, for sure. Where do I tap it? across from Boost Pressure Control switch? I think that's the first thing I'll do once engine is running right.

And whose gauge would you recommend?

Cleaning injectors and purging all fuel lines now. New plugs of course.

Thanks,

GN

chuck21401 wrote:
Gatornapper wrote:

Should I just get the car running well


IMHO that's the first step. Somewhere along the way you might consider adding a boost gauge, at least temporarily so that you can determine if the wastegate is operating properly.
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Gatornapper  



Joined: 23 Oct 2021
Posts: 155
Location: VA

PostPosted: Tue Dec 07, 2021 2:19 am    Post subject: Reply with quote

Thanks Vaughan.

GN

924RACR wrote:
Removing and installing the turbo with the motor in the car is a massive PITA, but do-able - I've done it numerous times. But the actual rebuild of the turbo itself definitely needs a legit turbo shop to be done right - because balancing at high speed. Worth considering an upgraded compressor wheel while in there, if you need to go that route.

The trans swap isn't that big a deal IMO - just a big disassembly. Fortunately, going that direction ends up being simpler, not more complex (mainly in shift linkage). If it becomes necessary.
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924RACR  



Joined: 29 Jul 2001
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PostPosted: Wed Dec 08, 2021 9:48 pm    Post subject: Reply with quote

If you use the boost switch/wastegate sensing line point, you won't read vacuum when not WOT (correct me if I'm wrong here)... I tapped mine into the manifold to get that reading too...

Though in my case it was in place of the boost line to the DITC, since I ditched the DITC and went MS. Though actually I did have it teed in at one of the smaller vacuum ports on the throttle body before that, before the conversion...
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Mike9311  



Joined: 14 Dec 2004
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PostPosted: Fri Dec 10, 2021 12:51 am    Post subject: Reply with quote

I did something like this one my 80 way back when and didn't read vacuum

Also, Gatornapper, to me you got a very cool version of the 924T. The early US model has lower compression and larger compressor wheel on the turbo. Plus its simple and in no way a dud. I have had lots of fun in my 80 so I am partial to the early version
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Gatornapper  



Joined: 23 Oct 2021
Posts: 155
Location: VA

PostPosted: Fri Dec 10, 2021 2:51 am    Post subject: Reply with quote

RACR -

Not being former military (Lord knows, I tried...), not sure what DITC or MS stand for.....

TIA,

GN

924RACR wrote:
If you use the boost switch/wastegate sensing line point, you won't read vacuum when not WOT (correct me if I'm wrong here)... I tapped mine into the manifold to get that reading too...

Though in my case it was in place of the boost line to the DITC, since I ditched the DITC and went MS. Though actually I did have it teed in at one of the smaller vacuum ports on the throttle body before that, before the conversion...
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Gatornapper  



Joined: 23 Oct 2021
Posts: 155
Location: VA

PostPosted: Fri Dec 10, 2021 2:54 am    Post subject: Reply with quote

Mike - VERY encouraging - thank you.

Stuck trying to get my injectors cleaned & working. Soaked in Berryman's Carb Cleaner, then 30 min. in ultrasonic cleaner, but 3 of 4 are still blocked.

May have to buy new ones.

Trying something new today: putting small amount of Seafoam in ultrasonic cleaner (it's a small one, just big enough for 1 injector at a time) and see if that will clean them up.

Otherwise I'll be getting new injectors.

GN

Mike9311 wrote:
I did something like this one my 80 way back when and didn't read vacuum

Also, Gatornapper, to me you got a very cool version of the 924T. The early US model has lower compression and larger compressor wheel on the turbo. Plus its simple and in no way a dud. I have had lots of fun in my 80 so I am partial to the early version
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Gatornapper  



Joined: 23 Oct 2021
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Location: VA

PostPosted: Thu Jan 06, 2022 12:20 pm    Post subject: Re: Early '80 931 Turbo ISSUES/PROBLEMS Reply with quote

Chuck -

Where would I tap for the boost gauge? Easiest & most simple point?

GN

chuck21401 wrote:
Gatornapper wrote:

Should I just get the car running well


IMHO that's the first step. Somewhere along the way you might consider adding a boost gauge, at least temporarily so that you can determine if the wastegate is operating properly.

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'80 924 Turbo, 58k miles, great condition, being restored; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......
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joemoma1990  



Joined: 29 Jun 2021
Posts: 27
Location: Apple Valley, MN

PostPosted: Fri Jan 07, 2022 5:19 am    Post subject: Re: Early '80 931 Turbo ISSUES/PROBLEMS Reply with quote

Gatornapper wrote:
Chuck -

Where would I tap for the boost gauge? Easiest & most simple point?

GN



Yea I would like to know that as well LOL
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anthonimartini  



Joined: 17 Feb 2020
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Location: portland oregon

PostPosted: Fri Jan 07, 2022 8:45 am    Post subject: Reply with quote

I added a t from the brake booster hose. I prefer to know what boost pressure is at the manifold as the closer to the turbo you measure the higher the number will be.more of an issue when running an intercooler which I am.
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924RACR  



Joined: 29 Jul 2001
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PostPosted: Fri Jan 07, 2022 10:58 pm    Post subject: Reply with quote

I tee'd in at the small vacuum port by the throttle body (on the manifold side, as noted, not the charge tube side)... less to go bad if it came loose (as opposed to messing with the DITC boost port).

Though now that I've ditched the DITC (MS conversion), I use the larger port that was for the DITC to feed both my boost gauge and manual boost controller...
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