[Alter Ego]

How long do you all wait to warm up the engine after starting it up before you drive off?(From a cold start that is.)



I have heard varying thoughts on this in the past. Some say 30 seconds due to electronic fuel injection. Some wait several minutes. The owners manual I think says don't let the engine idle for more than a few mintues to prevent damage? (that one doesn't make any sense to me.) I am just trying to prevent any unnecessary premature damage/wear to the engine as much as possible. I just figured that the longer you let the engine warm-up at idle, the more lubricated and 'ready' the engine will be upon driving off.



Also, BMW M5 and M3 have indicator lights on the tach to indicate when it is 'ok' to rev up to that particular RPM when driving while the engine is reaching optimal temp. A while back, I read that it could take up to 15 minutes of normal driving before the engine management will allow redline RPM to be reached. Any thoughts on any of this?



Thanks in advance!

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[Cloud9...68]

I don't speak from any sort of credentials on the subject, but I would bet at least a nickel that this falls into the same category as so many other items of automatove lore, that what used to be a valid rule of thumb ("make sure to let 'er idle at least [fill in the blank] minutes before driving off") no longer applies to modern cars with electronic engine management. Especially if you're running synthetic oil, which all of us should be. Obviously, you don't want to floor it as soon as it fires to life, but I would guess that driving away after a few seconds, as long as you drive fairly modestly for the first few miles, is perfectly fine.

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[968rz]

Give it a couple of minutes (2-5?) to allow the oil to flow to all the internal parts. Taking off too soon just put more stress on un-lubed bearings and such .

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[Cloud9...68]

Not to start an argument over this or anything, but I wonder how long it actually takes for synthetic oil under 50+ psi to flow to the endinge's critical parts? I would venture it would take on the order of seconds. And the parts aren't exactly devoid of oil while they sit idle. Have you ever looked at a bearing after removing it from an engine? All the ones I've ever removed are soaked in oil. Yes, it takes awhile for the engine to warm up, but aren't multi-viscosity oils designed to flow well at the lower temperatures typically seen during the warm-up period? Of course, there's nothing wrong with letting the engine idle for a few minutes before driving off, but my guess is that it isn't necessary. Any mechanical engineers out there (I'm just a humble Chem E) who can shed some educated light on this?

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[rustech]

Let me start by an old saying, "opinions are like ..., everyones got one"

I agree with you on this Cloud. Start the car, give it about 10 seconds, start driving, and keep the rpm low (~<3000rpm) until up to temp. I even wait about 5 minutes past the point it reaches temp to ensure the oil temp catches up. That is how I ensure the oil has thinned enough to flow properly. I've also read on many cars not to idle them too long, especially at startup, because it might result in hot spots in the engine.

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[SILVY968]

I had this argument with my son, who insisted that ALL engines need to " warm up".

We consulted the PORSCHE manual for the 968, which states that you should NOT warm up the car, but start to drive right after starting.

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[Cloud9...68]

[quote name='rustech' post='29928' date='Jan 15 2007, 08:10 PM']I've also read on many cars not to idle them too long, especially at startup, because it might result in hot spots in the engine.[/quote]



Yes, I also heard/read somewhere that it is not only not necessary to let the engine idle too long after starting, but that it is not advisable, but it was a long time ago, and I don't remember where I heard it. Modern cars, of which, unlikely as it may seem for a design that dates back to the late 70's, the 968 is one, are so drastically different from the carbureted, point-ignition, mechanical timing machines of yesteryear, that so many of the old rules just don't apply. The BMW M cars have it right - fire it up, let it settle for a few seconds, then drive, gently at first, then with increasing vigor as things warm up.



[quote name='SILVY968' post='29933' date='Jan 15 2007, 09:05 PM']I had this argument with my son, who insisted that ALL engines need to " warm up".

We consulted the PORSCHE manual for the 968, which states that you should NOT warm up the car, but start to drive right after starting.[/quote]



Ah, we have an authoratative source! Interesting how you and your son flipped my argument on its head - the more seasoned one of you understanding that "rules of thumb" can change over time, while the younger one went with the "that's how it's always been done" thinking. Who says us old guys are always stuck in our ways?

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[earossi]

The thing about today's engine technology is that you need to warm them up as fast as reasonably possible without putting excessive loads on them. The issue is not really lubrication anymore. Today's synthetic oils are more stable on viscosity and flow much better on a cold start than the oils of 20 years ago.



So, my "opinion" is that you should start your car cold and allow 20 to 45 seconds for fully established lubrication flow; and then start driving the car, but not aggressively. By that I mean that you should not initiate any jack rabbit "launchs" or take on that muscle car next to you in a drag race. Just drive the car as you would drive your normal boring sedan. Do this until the temp gauge begins to climb off the peg.....then you are good to go. Once the temp gauge is off the peg, you are probably 3 to 5 minutes away from reaching the normal range for these engines.



So, what is the issue? Today's engines are much tighter than the 55 Chevies we used to drive. The bearings run tighter. The pistons are a tighter fit as are the piston rings......and so forth. So, the faster you can warm up the motor without abusing it, the faster the clearances open up. My guess is that you probably see more engine wear per crackshaft revolution on a cold engine than on a hot engine.....so, rapid heat ups should add life to the engine. That's my 2 cents anyway.



The second issue with a cold engine, is that to overcome the increased internal friction of a cold engine, the fuel management system "wants" to run a rich fuel/air mixture to keep the engine from dying. On a carbuerated engine, this was the function of both the choke and the accelerator pump circuits. The choke reduced the amount of air while the accelerator pump added more than the normal fuel to get you going. Today, this is done by computer (and much better, I might add!).



So, why is a "rich" fuel/air ratio an issue? Simply because it is possible to get the saturated atomized fuel to condense out on the "cold" cylinder walls. Once the fuel condenses on the cylinder walls, it runs down the walls and gets by the piston rings and then into the oil. As the fuel moves down the piston walls, it effectively dissolves any lubricating oil film that provides lubrication for the piston rings. Finally, any fuel that makes its way past the piston rings gets added to your oil and dilutes the oil and its ability to lubricate. This phenomina doesn't last very long........seconds to minutes at the most. And then, the fuel will vaporize as the oil heats up and move into your emmissions system. But, for this very short time period, your engine sees accelerated wear.



The bottom line to all this is that you want to warm your engine up as rapidly as possible without placing big loads on the engine. Since driving the car under light load creates much more heat than "idling at a standstill", you should drive it.



Sorry for the long post.

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[bob blackwell]

When I bought my first Porsche it was a brand new 1965 SC in Germany. The dealer who picked it up at the factory and delivered it to me said no warm up is necessary with a Porsche, it warms up best while you are driving it. He also encouraged me not to lug the engine but rev it freely as I accelerated through the gears. I have joyously followed his instructions for all these many years with many different Porsches. Now that we have seat belts I start the engine then connect the seat belt and drive away. Good luck, Bob Blackwell.

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[Super_Marv]

Yep - I do what I do with all the cars I've owned. Get in, drive away. It's the best way to warm everything up, as said before.

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[sasilverbullet]

FYI...in Germany it has long been against the law to idle your car excessively, i.e. 'warm it up' because of clean air laws.



So it stands to reason in my book that the German manufacturers will build the cars to take a short warm up.



As far as whether it's good or not until it's warmed up - I think that if you start of quick but as little a strain on the engine as you need till it warms up!



On our cars, I'm more worried about the timing/balance belts 'warming up' and not snapping than the metal components!!!

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[Anchorman]

One of the reasons to start driving - modestly - almost immediately is that it gives a chance for EVERYTHING to get warmed up, as noted above by Super Marv. The entire drive train needs to get "warm", not just the engine. So, like Bob, I start the engine, put on my seat belt, and away I go, keeping generally below 3k rpm until the heater starts putting out warm air.

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[sguy]

I agree with Anchorman, start, get everything adjusted, drive modestly to warm up. It probably takes 10-15 minutes for everything to come to optimum operating temperature (thoroughly heat soaked), so hold off on the "full out" for a while. We haven't been above freezing for a week with snow on the roads so the Porsche is garage bound - Sniff.



Cheers

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[flash]

the new computer ignition systems do shorten the warm up period - but, metals are metals, and their inherant characteristics are a constant - ring expansion takes a bit of time - it is also assisted by loading the engine



what does that mean? after the first few seconds of letting things settle in, and making sure you have gotten the deposits off of the O2 sensor, and fuel atomization is normalized by the computer, go ahead and drive - then keep it in as tall a gear as is possible until the water temp comes up - that means lugging the engine - make it work - this does not mean floor it in 6th gear at 20mph - it means go up a gear or two from what you normally would, and don't go over 3.5k, trying to keep shifts at 3k or so - once the water temp comes up to normal, drive as you normally would

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[Renalicious]

I too typically get in and drive away, shifting at 3k

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[Dave]

I drive Porsche's within 5 seconds of start-up. Keep revs below 4k rpm and up to half throttle until the oil pressure at idle drops to your normal warm spot (usually around 1.5 - 2 bar). At this point, the oil is warm and you can flog it like the beast it is, full throttle, right up to redline.



That's my story and I'm stickin' to it.

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[VGM911]

[quote name='Anchorman' post='29980' date='Jan 16 2007, 09:41 PM']One of the reasons to start driving - modestly - almost immediately is that it gives a chance for EVERYTHING to get warmed up, as noted above by Super Marv. The entire drive train needs to get "warm", not just the engine. So, like Bob, I start the engine, put on my seat belt, and away I go, keeping generally below 3k rpm until the heater starts putting out warm air.[/quote]



I, too, agree with this thread's concensus of a short warm-up (only a few seconds) and driving moderately until the coolant and oil temps come close to normal operating levels.



Anchorman's point was also made in the current issue of Roundel (BMWCCA's monthly publication) by tech guru Mike Miller....he believes that it's important to warm up everything, including the drivetrain, before putting the pedal to the metal. So a short warm-up (30 seconds) and moderate driving as described above are also his prescription, as well. Warming up your engine while you're in the house finishing your coffee is a needless waste of gasoline.

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[Tom in Austin]

Interesting discussion ... when I pull out of my driveway in the morning, I go up a short uphill to a 4-way stop. I have to choose between keeping it in first and revving to about 3,500 rpm or shifting to second and having RPMs fall to around 2,000 (I've never liked the 1-2 gear split anyway).



My theory is it's easier on the cold drivetrain to go to 3,500 rpm even with a 'cold' engine than try to upshift and lug it.

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[flash]

3.5 is no big deal, but it is better on the rings to lug it and get them to expand - that is actually how i used to break in an engine - there was a really good hill i would go and lug it up - worked great, and much better than the 500 mile method



also, if you think about it, at 3.5k, everything is spinning faster, therefore enduring more friction, therefore producing more wear



the lower the rpm the better

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