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Registered
Join Date: Jul 2021
Posts: 634
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How long does a 911 engine stay "warm"?
Running through a series of compression and leak-down tests, both of which should be done with the engine "warm". I timed myself at about 15 minutes per cylinder. Pretty slow, I know.
If I start my car and let it idle for 15 minutes, the engine is painful to hold my finger tips to, implying to me that it's warm enough. However, 30 minutes later (only 2 cylinders done) the engine is now just warm to the touch, not "hot". Am I overthinking this and warm to the touch is adequate, or should I be re-starting the engine and letting it warm back up every so often - maybe in between banks? |
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12-10-2022, 06:38 PM
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oil temp to normal, 180 is a warm engine .
Ian
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Kermit, 73 RS clone, Just Part of the Team Chris Leydon ,Louis Baldwin ,Peter Brock ,Riche Clark Jerry Sherman ,Rob McGlade ,Donnie Deal Hank Clarkson ,Craig Waldner ,Don Kean ,Leroy Axel Gains |
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12-10-2022, 07:26 PM
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Original Owner
Join Date: Dec 2002
Location: San Antonio, Texas
Posts: 1,905
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Compression and leak down should be run cold.
Why? Cold numbers don't lie...... Hot is OK...but hot numbers lie.....
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tsuter 78 911SC Turbo Targa Thaaaats Right!! |
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12-11-2022, 03:12 AM
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Titanium User
Join Date: Aug 2014
Location: NY
Posts: 3,238
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Always on a cold motor is what I've done and been told.
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12-11-2022, 05:45 AM
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Original Owner
Join Date: Dec 2002
Location: San Antonio, Texas
Posts: 1,905
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Sellers and Dealers do it hot....buyers do it cold....muhahahahaha!
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tsuter 78 911SC Turbo Targa Thaaaats Right!! |
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12-11-2022, 07:01 AM
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Registered
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How long the engine stays hot depends on ambient temps, summertime I needed 2 hours to fiddle with anything, winter maybe 45 mins.
180° is Hot - Warm (metal for instance) is anything that can be handheld comfortably for over 5 mins…85°-105° is a generally acceptable “tepid” range. As like stated measuring Cold vs Hot is a variable, as heat will increase/expand where as cold will retract/shrink the tolerances measured. So, is it the rational being it would be best measured at midpoint or Warm…? Operating at normal temp (180°ish) will essentially “seal” any worn rings/valves/guides while driving under normal conditions, until cold again - e.g. leaking oil into cylinders. If I’m at 175psi w/8% LD…I can expect 5 mins oil smoke from the tailpipe if she sits more than 6 weeks and zero oil smoke on startup after 2 weeks. |
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12-11-2022, 10:20 AM
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