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      12-26-2014, 11:20 PM   #1
wrecklessfool
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Want to add oil pressure warning light—What PSI?

I have read that BMW sets the factory oil pressure idiot light to illuminate at 7 PSI. At that point I would argue that the engine is milliseconds from destruction or that the damage has already occurred. What I want to do is add a warning light sensor in addition to the factory sensor using the Macht Schnell adapter kit and a generic sensor through Summit Racing. Doing some digging around on here I have found people generally see about 30-40 PSI at idle and the rest of the rev range is higher. I also read a thread where someone stated the idle PSI was supposed to be 1 BAR (14.7 PSI) so I am a bit unclear on what the idle pressure actually is. I was considering getting an 18 or 20 PSI sensor to trigger a signal at that reading. Can anyone make a qualified recommendation on what pressure would be good for a warning light? I don't want to get too close to the normal idle pressure to avoid false alerts, but don't want to go so low that the project is useless or I stand the chance of damage occurring before the engine is shut down. Thanks guys!
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      12-27-2014, 01:34 AM   #2
Hujan
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Have you looked into possibility of coding car to illuminate at higher threshold? I would ask Mike at BPM Sport.
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      12-27-2014, 01:30 PM   #3
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Here are the specs from Mitchell Pro:

Oil pressure at idle speed with engine at operating temperature min bar 1.0
Control pressure with engine at operating temperature bar 4.0 ... 6.0
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      12-27-2014, 02:48 PM   #4
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Quote:
Originally Posted by kenwelch
Here are the specs from Mitchell Pro:

Oil pressure at idle speed with engine at operating temperature min bar 1.0
Control pressure with engine at operating temperature bar 4.0 ... 6.0
So by these numbers even putting in a 15 psi trigger could potentially trigger a false alert at idle? Min is 14.7, but what is the average from users who have a gauge installed? Like 30-40 psi at idle when warm?
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      12-27-2014, 06:05 PM   #5
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On my data logger I have it set for 25 psi when the RPMs are over 2000. Eliminates the light at idle when warm.
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      12-28-2014, 12:49 AM   #6
wrecklessfool
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Quote:
Originally Posted by gobuffs View Post
On my data logger I have it set for 25 psi when the RPMs are over 2000. Eliminates the light at idle when warm.
Not sure I follow. Do you have a gauge? If so, what pressure are you seeing at idle with TWS oil?
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      12-28-2014, 09:40 AM   #7
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I have a gauge and a reading in a data logger. Sorry, don't run TWS oil, but looking back at the data it seems like the hot idle oil pressure is around 40.
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      12-28-2014, 07:06 PM   #8
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Quote:
Originally Posted by gobuffs
I have a gauge and a reading in a data logger. Sorry, don't run TWS oil, but looking back at the data it seems like the hot idle oil pressure is around 40.
Ok thank you. Sounds like if I run a 20 psi switch the ONLY time I would see the light illuminate is if a failure occurred. And of course prior to startup. Does this sound accurate? If so I'll purchase the 20 psi sending unit unless you have an alternate recommendation. Thanks again.
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      12-28-2014, 07:31 PM   #9
pbonsalb
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Quote:
Originally Posted by gobuffs View Post
I have a gauge and a reading in a data logger. Sorry, don't run TWS oil, but looking back at the data it seems like the hot idle oil pressure is around 40.
40 psi would be a lot of pressure for 600 rpm.
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      12-29-2014, 07:33 AM   #10
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My idle is around 1000. But I don't normally pay attention to idle speed or pressure after initial spike. I do see it is getting pressure on track.
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      12-29-2014, 09:13 AM   #11
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I run 0-40 only and have never seen it below 27psi at idle, that is 240 oil. At 210-220 it is always above 30.
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