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Gatornapper
Joined: 23 Oct 2021 Posts: 294 Location: VA
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Posted: Sun Dec 05, 2021 12:36 am Post subject: Early '80 931 Turbo ISSUES/PROBLEMS |
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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: 8794 Location: Royal Oak, MI, USA
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Posted: Sun Dec 05, 2021 10:35 pm Post subject: |
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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. _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Gatornapper
Joined: 23 Oct 2021 Posts: 294 Location: VA
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Posted: Mon Dec 06, 2021 11:35 am Post subject: |
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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: 525 Location: Annapolis, MD
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Posted: Tue Dec 07, 2021 12:09 am Post subject: Re: Early '80 931 Turbo ISSUES/PROBLEMS |
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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. _________________ 1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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924RACR
Joined: 29 Jul 2001 Posts: 8794 Location: Royal Oak, MI, USA
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Posted: Tue Dec 07, 2021 12:52 am Post subject: |
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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. _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Gatornapper
Joined: 23 Oct 2021 Posts: 294 Location: VA
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Posted: Tue Dec 07, 2021 2:18 am Post subject: Re: Early '80 931 Turbo ISSUES/PROBLEMS |
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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: 294 Location: VA
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Posted: Tue Dec 07, 2021 2:19 am Post subject: |
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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 Posts: 8794 Location: Royal Oak, MI, USA
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Posted: Wed Dec 08, 2021 9:48 pm Post subject: |
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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... _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Mike9311
Joined: 14 Dec 2004 Posts: 1678 Location: Chicago-ish
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Posted: Fri Dec 10, 2021 12:51 am Post subject: |
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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 _________________ 1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
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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Gatornapper
Joined: 23 Oct 2021 Posts: 294 Location: VA
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Posted: Fri Dec 10, 2021 2:51 am Post subject: |
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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: 294 Location: VA
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Posted: Fri Dec 10, 2021 2:54 am Post subject: |
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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 Posts: 294 Location: VA
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Posted: Thu Jan 06, 2022 12:20 pm Post subject: Re: Early '80 931 Turbo ISSUES/PROBLEMS |
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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. |
_________________ '87 944 S, looks & runs like new - sold my sweet 931; '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: 32 Location: Apple Valley, MN
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Posted: Fri Jan 07, 2022 5:19 am Post subject: Re: Early '80 931 Turbo ISSUES/PROBLEMS |
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Gatornapper wrote: | Chuck -
Where would I tap for the boost gauge? Easiest & most simple point?
GN
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Yea I would like to know that as well LOL |
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anthonimartini
Joined: 17 Feb 2020 Posts: 240 Location: portland oregon
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Posted: Fri Jan 07, 2022 8:45 am Post subject: |
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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. _________________ ive saved alot of 924's
current:
79 MochaSchwartz 931
83 944
87 924S
Instagram @anthoni.jpeg
formerly known as turbellion, lost password. |
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924RACR
Joined: 29 Jul 2001 Posts: 8794 Location: Royal Oak, MI, USA
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Posted: Fri Jan 07, 2022 10:58 pm Post subject: |
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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... _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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