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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Tue, Aug-01-2017, 11:42:51 AM   #41
TheSt|G
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Default Re: Getting Gas with the Engine Running

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I still don't see why a brief idle warm up (< 2-3 mins) is bad for the engine.
Assuming it takes X revs to warm up the engine, then it may take more time, but no fewer cold revs than warming it up at speed. And I don't see why different rates of expansion would change this - if anything I'd think a prolonged, steady warm up would be better for parts that expand at different rates. But I am no mechanical engineer.
But further, why not rev it up nice and high right away, and get it warm extra quickly? We obviously wouldn't do that, so what's the sweet spot? We don't have oil pressure gauges, and what's optimal probably depends on ambient temperature.
I don't buy it just because BMW says it - for all we know, they're saying it so that your cats get up to temp quicker or to prevent inhalation of exhaust gasses. It's interesting that in some cases people think whatever BMW says is to be taken for pure truth, and in other cases we're happy to prove they're undeniably wrong (vanos, subframe, OCIs, whatever).
To dispel the notion that it is for emissions purposes, here is a page directly from the manual of my 911 that was prior to such things. The writing is pretty clear:

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Old Tue, Aug-01-2017, 11:55:00 AM   #42
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Default Re: Getting Gas with the Engine Running

Daaaaaaamn, STIG.

Okay, the matter is settled for me. Crazy. I really always thought I was doing my engine a favor. Noted!
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Old Tue, Aug-01-2017, 12:21:58 PM   #43
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Default Re: Getting Gas with the Engine Running

Could always get an accusump and pre oil every startup. I have seriously considered that for the s85 but since I'm doing a bypass filter too it will just complicate the system too much
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Old Tue, Aug-01-2017, 12:27:13 PM   #44
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Default Re: Getting Gas with the Engine Running

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Could always get an accusump and pre oil every startup. I have seriously considered that for the s85 but since I'm doing a bypass filter too it will just complicate the system too much
Would it be feasible and/or helpful to implement a separate circuit for the starter motor, so we can crank the engine for a few seconds with no fuel/spark in hopes of pre-oiling everything a little? Not sure if it would make any difference
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Old Tue, Aug-01-2017, 12:45:37 PM   #45
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Default Re: Getting Gas with the Engine Running

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Would it be feasible and/or helpful to implement a separate circuit for the starter motor, so we can crank the engine for a few seconds with no fuel/spark in hopes of pre-oiling everything a little? Not sure if it would make any difference
What RPM does the starter crank at, do you know? This would touch on my "old airplane" concept, and I love it. I always pictured a slower crank than the starter speed, but I'll bet that must spin the engine at a lot less than 800rpms?
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Old Tue, Aug-01-2017, 01:05:01 PM   #46
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Default Re: Getting Gas with the Engine Running

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What RPM does the starter crank at, do you know? This would touch on my "old airplane" concept, and I love it. I always pictured a slower crank than the starter speed, but I'll bet that must spin the engine at a lot less than 800rpms?
Oil tech has moved on in a monumental way since prop planes.
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Old Tue, Aug-01-2017, 01:10:26 PM   #47
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Default Re: Getting Gas with the Engine Running

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Oil tech has moved on in a monumental way since prop planes.
Yes, but to my OCD biological engineering, that span of time is but a heartbeat.
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Old Tue, Aug-01-2017, 01:20:26 PM   #48
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Default Re: Getting Gas with the Engine Running

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What RPM does the starter crank at, do you know? This would touch on my "old airplane" concept, and I love it. I always pictured a slower crank than the starter speed, but I'll bet that must spin the engine at a lot less than 800rpms?
I think the starter only spins the engine at a few hundred rpm max
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Old Tue, Aug-01-2017, 01:25:56 PM   #49
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Default Re: Getting Gas with the Engine Running

I really don't pretend to know better, I'm just trying to learn why this is the case.
So where does the "3K" cold limit come from? My gauges say 5k or so is fine at startup, and the redline moves up from there as it warms. I sure as heck ain't going to 5k right after startup. And I have the conservative CSL warmup lights! Point is, y'all probably right but it's not just because BMW says it's so. We don't do 15K OCIs either.
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Old Tue, Aug-01-2017, 01:28:17 PM   #50
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Default Re: Getting Gas with the Engine Running

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I really don't pretend to know better, I'm just trying to learn why this is the case.
So where does the "3K" cold limit come from? My gauges say 5k or so is fine at startup, and the redline moves up from there as it warms. I sure as heck ain't going to 5k right after startup. And I have the conservative CSL warmup lights! Point is, y'all probably right but it's not just because BMW says it's so. We don't do 15K OCIs either.
True. That's true. One could argue that BMW is fine with 5k rpms from the moment of "Starting up and driving away", and there seems to be zero indication that we should do otherwise.

And yet: clearly that's not a good idea.
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Discussing Getting Gas with the Engine Running in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)