GTS Oil Pressure - WHAT SHOULD IT BE?
10-11-2009, 04:15 PM
#17
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I just noticed something interesting, not on a GTS but you may find it relevant. If I start the car cold, wait till the engine sorts itself out and runs smooth(5-10 sec., CIS takes a bit) then turn the key off then back on after the engine stops spinning, it takes about 15 seconds for the oil pressure to get down to 1 bar. When it's hot, it drops to zero too quickly to evaluate this way.
Comparisons using this technique may be informative. IMHO it's a measure of flow, all else being equal worn bearings ought to show a more rapid pressure drop(also varies with base viscosity). If changing oil type in the same car, differences here may be interesting to note. Certainly there is far more to lubrication science and theory than can be summed up with such a "leakdown test", and I'm not sure what, if any, real meaning can be derived from results of this test. At the very least, individuals may find their own baseline using this technique and observe variations at a later date. New sender last weekend, FWIW.
Also, I used to use Valvoline 20-50 "high performance" dino. Once when I couldn't find it, I went to CarQuest and they said the CQ label was Valvoline, even showed me the MDSD to back it up. However, I found that my 3 bar hot idle was now ~2-1/3 bar. Needless to say, I changed it out fairly quickly.
As an example of how this may be applied, if Brian had performed a baseline "oil leakdown" test when he first got his car back, then again after his incident and when the car was dead cold again, he would have known instantly that he had a catastrophic lubrication issue.
Comparisons using this technique may be informative. IMHO it's a measure of flow, all else being equal worn bearings ought to show a more rapid pressure drop(also varies with base viscosity). If changing oil type in the same car, differences here may be interesting to note. Certainly there is far more to lubrication science and theory than can be summed up with such a "leakdown test", and I'm not sure what, if any, real meaning can be derived from results of this test. At the very least, individuals may find their own baseline using this technique and observe variations at a later date. New sender last weekend, FWIW.
Also, I used to use Valvoline 20-50 "high performance" dino. Once when I couldn't find it, I went to CarQuest and they said the CQ label was Valvoline, even showed me the MDSD to back it up. However, I found that my 3 bar hot idle was now ~2-1/3 bar. Needless to say, I changed it out fairly quickly.
As an example of how this may be applied, if Brian had performed a baseline "oil leakdown" test when he first got his car back, then again after his incident and when the car was dead cold again, he would have known instantly that he had a catastrophic lubrication issue.
10-11-2009, 05:09 PM
#18
Race Director
H
Sharky never ever read higher than about 4.8bar...but the widow will PEG 5.0bar easily....I think its just a variable in the sender calibration
Another idea that REALLY helped raise the hot idle oil pressure on sharky was to replace both springs to the oil thermostat....I was getting hot restarts of under 1 bar.....after changing the springs it never got under 2.5 bar hot....I think the springs fatique over time which cause the oil cooler to always be open, lowering pressure.....I think I confirmed this in the widow which had the oil thermostat removed and had a hot idle of about 1.8bar...granted on a dying engine..
Sharky never ever read higher than about 4.8bar...but the widow will PEG 5.0bar easily....I think its just a variable in the sender calibration
Another idea that REALLY helped raise the hot idle oil pressure on sharky was to replace both springs to the oil thermostat....I was getting hot restarts of under 1 bar.....after changing the springs it never got under 2.5 bar hot....I think the springs fatique over time which cause the oil cooler to always be open, lowering pressure.....I think I confirmed this in the widow which had the oil thermostat removed and had a hot idle of about 1.8bar...granted on a dying engine..
10-11-2009, 06:08 PM
#20
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The spring that contols max oil pressure is normally set at 8 bar so a hot 928 should be pegged on the 5 stop!
Anything less should be investigated; hopefully just a faulty gauge.
Anything less should be investigated; hopefully just a faulty gauge.
10-11-2009, 07:24 PM
#21
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1.5 bar on the GTS is normal
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
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928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
10-11-2009, 07:55 PM
#22
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