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Water-to-air intercooler installation - 81 931
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chuck21401  



Joined: 20 Feb 2005
Posts: 467
Location: Annapolis, MD

PostPosted: Sat Apr 09, 2022 5:54 am    Post subject: Reply with quote

I'm hopeful that I've been able to sort the electrical gremlins after replacing the wiring harness to the starter/alternator and the alternator itself. The car seems to be running well and staying cool with the new engine fan in place.

I did seven runs at the local PCA "test and tune" autocross the other day...and nothing broke.


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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler.


Last edited by chuck21401 on Fri May 20, 2022 9:13 am; edited 2 times in total
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Fifty50Plus  



Joined: 28 Feb 2008
Posts: 1279
Location: Washington DC area

PostPosted: Sat Apr 09, 2022 7:55 am    Post subject: Reply with quote

New Avatar! Looking good.
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car
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chuck21401  



Joined: 20 Feb 2005
Posts: 467
Location: Annapolis, MD

PostPosted: Wed Jun 22, 2022 5:25 am    Post subject: Reply with quote

Couple of updates:

1. Oil pressure. After reading the recent thread regarding 931 oil pressure, I think mine is low. Warm oil pressure is 4 bar at highway speed warmed up and does not increase with RPMs. Idle warm oil pressure is between 1-2 bar.

The oil pressure gauge flickers a bit so I'm going to run a new ground wire first, then will check the oil pressure relief valve piston and spring. Finally I'll check out the cam oiler tube and elbow.

I recently changed the oil from 20W50 dino oil to 15W50 Mobil 1 synthetic and new filter and didn't see much of a change.

2. Slight boost leak. I'm getting a boost leak between the intercooler and the intake. This is the second time that I've replace the orange O ring (part #20 in the picture below). The first time the O-ring broke, the second time I nicked it when reconnecting the intercooler. I replaced the O ring but loosening the connection, removing the old O ring and slipping in the new one. I think that was part of the problem.

This time I emptied the antifreeze, disconnected everything and removed the intercooler. I figured now would be a good time to see how much work it takes to pull the intercooler and get to the valve cover for when I
check the cam oiler tube and elbow. I switched to water for the summer so don't have to worry about antifreeze going everywhere next time.

I am also seeing some oil in the intake track. It's not a huge amount, but it's there. The previous owner rebuilt the turbo, I'm guessing some seals somewhere are leaking? I don't think it's bad enough to pull the turbo....I'm not getting smoke at the exhaust if that's what I should be looking for.

While the intercooler was out I added some heat shield to the bottom. I'm not sure that it will make much of a difference but I figure that it can't hurt.

I was able to get everything back together again. I've found that there is still a slight leak between the intercooler and the intake. I can tell because new oil residue has appeared at the connection. It's not much, but it's there. The car has no trouble making 14-15psi.

I'm not sure what else to do, there isn't much of an adjustment in the mounting points.



[/b]


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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler.
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2542
Location: MI

PostPosted: Wed Jun 22, 2022 7:44 am    Post subject: Reply with quote

It’s easy to see if the oiler tube is working..
Just look under the oil cap while it’s idling and you’ll see it squirting on a live right under it..
One of my under hood checks I very often look at..

That’s way more oil pressure than I ever saw my gauge read.. My car has been like “oil light on at idle when hot”, reading like 0.5, bar on 15-50 full synth, I believe the entire time I’ve owned the car..
But I do get my car very hot..

I decided a long time ago that if it was gonna blow it was gonna blow..
But back then I think replacement engines were easier/cheaper to come by factoring into that decision..

Same engine, haven’t touch anything inside ever other than taking the head off and putting it back on, and have done the oil pan gasket..

I ran it for quite some time @ 15psi in my early time with it doing almost nothing but hard test drives/boost pulls..
After I replaced the head gasket I almost immediately worked it back up to around 18psi and it’s never been lower than that since..
I set it to 20psi +- 1psi or so because that’s about where power stops increasing with boost as much.. Never set it lower on purpose..
I have logged up to 23psi and have seen my 20psi gauge buried further than that at other times..
Super high load pulls at 20+ in 4th up steep hills on purpose, right from bog spool to redline..

It doesn’t blow up..
Rips..

IF I actually have low oil pressure, it doesn’t care..
I’ve mostly run 15-50 Napa full synth with a shot of ZDDP additive, and most recently ran Rotella T6 in it for a couple of changes (hardest running)..
All good..


I wouldn’t believe anything that gauge says..
That oil pressure is fine anyway..
If your super concerned about it, rig a real oil press gauge to the same port the sensor is on..
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80 Turbo - Slightly Modified
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Shurick  



Joined: 15 May 2005
Posts: 517
Location: Russia, Moscow.

PostPosted: Tue Jun 28, 2022 4:44 am    Post subject: Reply with quote

Fasteddie313 wrote:
That’s way more oil pressure than I ever saw my gauge read.. My car has been like “oil light on at idle when hot”, reading like 0.5, bar on 15-50 full synth, I believe the entire time I’ve owned the car..
But I do get my car very hot..

Eddie, do you use stock oil cooler? And do you have oil temp gauge?

I have some crappy chinise 10-row 12" oil cooler in a stock location and see temps up to 120-130*C in a traffic jam. But if i push it hard on a racetrack or highway my oil temps drop down to 100-110*C

I run Shell 10-60 synth oil and my good fella, a seasoned race engeneer told me that temps will go down if i'll move to thinner oil.
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WBR, Shurick
'79 931 -- intercooled K26-3060-6.10 turbo @ 1.2 bar, EFI+EDIS, 951S brakes, stripped interior, 951 look.
'86 924S -- R.I.P.
https://www.instagram.com/ru_pacecar/
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2542
Location: MI

PostPosted: Tue Jun 28, 2022 6:22 am    Post subject: Reply with quote

Stock oil cooler, no oil temp gauge..

Have monitored my coolant temps extensively though and it doesn't even get close to coming up to stock temps there..

I don’t get to beat around a track at extended periods of time either..
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