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View Poll Results: How do you warm up your car?
Drive it as quickly as possible 24 72.73%
Let it idle to warm it up 6 18.18%
Sometimes idle and sometimes drive 3 9.09%
Voters: 33. You may not vote on this poll

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Poll: Warmup Procedures and beliefs

Hi,

I see a whole lot of people talking about "warming the motor up" by letting it idle. I saw that this was a wide-spread habit in the US when I was there, and that many people believe it is beneficial for the motor.

For the purposes of discussion, let's ignore warming the interior/demisting the screen when there's two ft of snow on the car, or getting the A/C working when the car's been sitting in direct sunlight @ 110+ degrees...

Where I grew up, I was always taught that idling the motor when cold was evil, as the oil was cold and at its thickest, and that the oil flow at idle is probably close to borderline when hot - thus inadequate when cold.

I was always told that you should use a fast idle (e.g. 1400-2000 RPM or so) for a few seconds for good oil flow and pressure, and then drive lightly to warm the motor up as quickly as possible, and that if there's any manual choke, that you should use as little as possible - and knock it off completely as soon as practical.

I also note that the Porsche handbook specifically states not to warm the car by allowing it to idle, but to drive it.

So how many of y'all idle the 930 to "warm it up", and how many of you believe that this is a harmful practise?

Is the recommendation in the Porsche handbook simply a result of the factory engineers believing the same things as me because we both live in Europe where this belief is widespread, or is there a good engineering basis for it?
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Last edited by spuggy; 11-08-2007 at 02:25 AM.. Reason: Clarified "fast idle" a bit
Old 11-08-2007, 02:18 AM
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I never idle it. As soon as I turn the key, away we go. *HOWEVER*, I NEVER boost a cold engine. I normally wait about ten to fifteen minutes...or until the oil temp needle is at the top of the first block on the bottom of the gauge.

As for cool down, I'm normally able to slowly cruise a few blocks through my enighborhood, and then it idles for a few moments in the garage while I have a peak undermeath the engine.
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Old 11-08-2007, 04:46 AM
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I should also point out that after many years of owning early air-cooled VWs, a Porsche 356, some MGs, Triumphs, a basket case of an Austin Healey, that this was also my procedure for driving them in the morning.
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Old 11-08-2007, 04:50 AM
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Quote:
Originally Posted by sand_man View Post
I never idle it. As soon as I turn the key, away we go. *HOWEVER*, I NEVER boost a cold engine. I normally wait about ten to fifteen minutes...or until the oil temp needle is at the top of the first block on the bottom of the gauge.
Sorry, what tempurature would that be, roughly? My gauge is numbered and doesn't look like that...

I stay around 3,000 RPM maximum until oil temp reaches 125 (I think - it's the unnumbered tick between 80 and 170 on my gauge), then I'll rev to 4,000 - but still carefully avoiding boost at this point.

I'll boost once the oil gets a little over 170 - which, with a FMOC, is about as high as it might get without boost on a cool day anyway...

Quote:
As for cool down, I'm normally able to slowly cruise a few blocks through my enighborhood, and then it idles for a few moments in the garage while I have a peak undermeath the engine.
Yeh, the nearest place to my house I can boost is a good 5 miles away, so I don't sweat the cool down much, even without a turbo timer circuit..

Although I have seen someone say they run the motor up a little (i.e. 1400 RPM or so) just before shutdown to ensure the turbo scavenge pump clears any additional oil.


Quote:
Originally Posted by bkreigsr
I just let it sit long enough to get out and close the garage door, then get back in and head out.
Revs stay between 2,000 and 3,000 until the oil gets to 170 deg.
Both you guys raise something that interested me, the topic of driving off almost immediately - and instrumentation differences...

NathanUK said in another post that oil pressures are limited to 5 bar. All the photos I've seen of the "druck" pressure gauges calibrated in bar, they look like they ONLY read as high as 5 - is this correct?

See, my oil pressure gauge reads up to 120 PSI (8 bar)... When I initially start the motor, I run it @ 2000 RPM (for good oil flow). Oil pressure reads 100 PSI (6.7 bar). A little more RPM will make the gauge read higher - it definately isn't limited...

PO told me to be careful not to run up the pressure too high in this stage.

After a few seconds (maybe 15-20, maybe a little longer, say, 30 if it's really cold), the oil pressure will blip downwards to 75-80 PSI or so for the first time - I believe this is the internal engine thermostat opening and returning the hot oil in the case.

After another 20-30 seconds, you start to see a succession of downward blips - I normally wait for 3-4 very close together (5-6 seconds) and then select gear and prepare to pull away.

If I sat there and continued to run @ 2000 RPM, about another 10-20 seconds would probably be enough that the oil pressure would be a constant 75-80 PSI (i.e. the engine thermostat was completely open, because any oil entering the motor gets hot enough on the way through to keep it open).

I'm pretty sure that running the motor up to 3,000 RPM in the first minute of starting it would create pressures that would exceed the ability of my 8 bar pressure gauge to display it. Just thought I'd mention that...
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Old 11-08-2007, 07:49 AM
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Quote:
Originally Posted by sand_man View Post
I should also point out that after many years of owning early air-cooled VWs, a Porsche 356, some MGs, Triumphs, a basket case of an Austin Healey, that this was also my procedure for driving them in the morning.
We're all just creatures of habit, aren't we?

Actually, I've always done pretty much the same thing with all my motorcycles (or cars I cared about) that I do with the 911 - just always wanted to get some heat into the motor - especially valves, pistons and heads - before putting any load on.

Some of that is a product of 60's Triumphs and Harleys having no cold enrichment worth a damn - they'll run with no load, but you need some heat in there in order to pull away without them being very cranky about it...
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Old 11-08-2007, 08:02 AM
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Quote:
Originally Posted by bkreigsr View Post
my reply was" oil gets to 170 deg", temperature - not oil pressure.
??

Yes, I read - and I believe understood - your reply, thanks.

Quote:
I'm not sure I would go by what my 30 year old pressure gauge is telling me, since the needle spends a good bit of time pegged at the top during warm-up and boost,
OK, I wondered if your gauge pegged at 5 bar. Looks like you answered that.

Mine reads up to the equivalent of 8 bar. It's never pegged - although it would, by revving the motor to 3000 in that first minute or so. It always reads 75 PSI (5 bar) during warmup (after that first minute) and under boost or above 4,000-ish.

I thought that, if your gauge stopped indicating anything useful at 5 bar, you might be both unaware of, and interested in, the behaviour of the internal thermostat - especially as it might intersect with your startup procedure.

If you don't believe my sender/gauge, that's fine by me - but I have no reason to believe it's not providing accurate information - I'd fix it if I did.

Like I said, the PO specifically pointed that out, and warned against over-pressurizing the oiling system. Think he said the engine oil cooler was the most vulnerable, but I don't really remember.

Quote:
and I know the pump is only capable of producing x amount of psi under a given set of parameters.
Things are very different when the oil is cold.

I've seen roller bearing motors - with a perfectly normal oil pressure of 6-12 PSI at idle, and a maximum of 30-35 PSI at full RPM - which idled above 60 PSI when the oil was cold. Easiest way to judge oil temperature, without a temp gauge. And that was a tiny little oil pump.
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Old 11-08-2007, 09:10 AM
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I drive away immediately. I limit myself to 3k rpm until I see a little over 120 degrees F on the guage. since the boost comes on pretty early in my car I sometimes see a little blip of up to .5 bar boost when I'm going through the gears. I wait until it's fully warmed up (around 180 degrees) before giving it boost intentionally or exceed 4k rpm.

Sometimes I let my American cars idle a bit while I get things together and get comfortable. Big water jackets, V8 engines, and forgiving tolerances make me tend to believe that it doesn't matter so much with them. That and I can replace an engine for less than $1000 in them... "It's not a pretty hammer, but it's cheap and effective" ;-)
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Old 11-08-2007, 08:11 PM
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I have heard it is not a good thing to warm up a 930 engine while it is sitting. I was told to drive it right after start up, and take it easy till the engine is at operating temps. Not sure why this is true b/c I used to always warm up V8 engines before driving, but many experienced mechanics told me different.
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Old 11-08-2007, 10:53 PM
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I do a combination of both. After starting the motor, I let it idle for 30-60 seconds to get some oil distributed throughout the engine. Then I drive off gently (like most of you seem to do), and wait until heat builds up before really winding up the motor.

It's a tradeoff: which will net you less overall engine wear? Idling the engine, which will take longer to warm it up (but at least you're doing it at the lowest revs possible)? Or driving gently, which will put more revs on the cold motor, but allow it to heat up much quicker? I fall into the latter camp. Nothings perfect, unless we start pre-heating the motor and oil before starting things up; so I think running the motor (almost) immediately--but gently--leads to less wear.
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Old 11-09-2007, 09:09 AM
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Quote:
Originally Posted by Noah930 View Post
It's a tradeoff: which will net you less overall engine wear? Idling the engine, which will take longer to warm it up (but at least you're doing it at the lowest revs possible)? Or driving gently, which will put more revs on the cold motor, but allow it to heat up much quicker? I fall into the latter camp. Nothings perfect, unless we start pre-heating the motor and oil before starting things up; so I think running the motor (almost) immediately--but gently--leads to less wear.
Yeh, I'm sure we're all doing what we do for the same reason, it's just that some of us are doing different things...

And when I lived in the US, I saw many non-petrolheads in WA who would idle their regular car for 5-10 minutes on a cold day before getting in it and driving off - they all seemed to be convinced it was "good" for the car, i.e. that it caused less wear than driving - however gently - on a cold motor.

Reason I do the "fast idle" thing is purely for adequate oil flow when the oil is cold. Before reading Wayne's recommendations for starting a brand spanking new engine rebuild (build oil pressure and run it @ 1,800-2,000 RPM for twenty minutes), I'd probably have run it at something closer to 1,200-1,400 RPM, rather than 2,000.

I should mention that my AAR does nothing at all on a cold motor - car will idle @ 950 when stone cold - although I'll get an 1,800 RPM idle slowly falling back to normal on a warm start - like if I stop for 20 minutes somewhere.
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Old 11-09-2007, 12:21 PM
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I like to start the engine first, then check mirrors put on seat belt etc etc.

I would not sit there and wait for no reason.

And yes, I too use the oil pressure gauge at idle to see how warm the oil is.
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Last edited by NathanUK; 11-10-2007 at 03:10 PM..
Old 11-10-2007, 03:05 PM
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Quote:
Originally Posted by sand_man View Post
I never idle it. As soon as I turn the key, away we go. *HOWEVER*, I NEVER boost a cold engine. I normally wait about ten to fifteen minutes...or until the oil temp needle is at the top of the first block on the bottom of the gauge.

As for cool down, I'm normally able to slowly cruise a few blocks through my enighborhood, and then it idles for a few moments in the garage while I have a peak undermeath the engine.
+1

If it hasn't been run in weeks, I may let it idle for a minute or two while I pack the trunk or install the radar detector...
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Old 11-10-2007, 09:43 PM
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