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9xx
Joined: 18 Jun 2006
Posts: 627
Location: Jarvenpaa, Finland
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 Posted: Fri Jul 24, 2015 12:16 am Post subject: 924/931 compression check |
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I recently sold my Carrera GT IC & hood and I have not yet installed the original charge tube. So I thought this would be a convenient time to perform compression check. I've done it once to a 944 but how is it with the 931?
-throttle body wide open
-remove the fuel pump fuse (at least in 944?)
?
Is that it?
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Mikko
All gone: 931 '82 Alpine White, original option "220" G31 with LSD + 3 x 944 |
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Fasteddie313
Joined: 29 Sep 2013
Posts: 2595
Location: MI
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| Posted: Fri Jul 24, 2015 1:12 am Post subject: |
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Yep WOT and pull the fuel pump relay, thats all I did..
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80 Turbo - Slightly Modified |
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9xx
Joined: 18 Jun 2006
Posts: 627
Location: Jarvenpaa, Finland
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| Posted: Sat Jul 25, 2015 12:23 am Post subject: |
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Well nevermind the absence of the charge tube because compression of course should be measured while the engine is warm. So I installed it back and drove around the block couple of times.
#1 170 psi
#2 160 psi
#3 n. 160-170 psi gauge started to leak
#4 n. 160-170 psi gauge started to leak
I do not recommend Biltema compression test kit for anyone. It started to leak somewhere from the gauge body itself so I had to hurry to see the results before the pressure dropped too much. Almost brand new kit  Anyway the results were very much satisfying. There is some blow coming from the oil cap hole but no blow from the dipstick hole. Well it is an old engine and I'm just fine with that slight blow. Emission values are good and it doesn't consume much oil. So I will continue to drive it hard.
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Mikko
All gone: 931 '82 Alpine White, original option "220" G31 with LSD + 3 x 944
Last edited by 9xx on Sat Jul 25, 2015 3:55 am; edited 2 times in total |
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Sat Jul 25, 2015 12:28 am Post subject: |
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| 9xx wrote: | | I will continue to drive it hard. |
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erstwhile owner of just about every 924 variant ever made |
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Fasteddie313
Joined: 29 Sep 2013
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Location: MI
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Sat Jul 25, 2015 2:52 am Post subject: |
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A more useful test / tool might be a leakdown.
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erstwhile owner of just about every 924 variant ever made |
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Fasteddie313
Joined: 29 Sep 2013
Posts: 2595
Location: MI
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| Posted: Sat Jul 25, 2015 3:42 am Post subject: |
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I plan to build a leakdown, it's just a 1mm standard (restrictor) port between 2 100psi gauges. Regulate pressure to your first gauge to 100psi and the difference between the 2 gauges = leakdown percent.. Use your spark plug adaptors from your comp tester..
100+psi source-regulator-gauge at 100psi-1mm restrictor port-100psi gauge-spark plug hole..
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80 Turbo - Slightly Modified |
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