How important is it to let the car warm up?

[BMW POWER]

yeh i've just dug out my manual and it says to allow it to idle after the turbo has been heavily used. on my way to work it normaly has a gentle 10 to 15 minutes of slow driving through the town which lets it warm up and then it gets a blast down the motorway between 80mph and 120mph for about 45 minutes depending on traffic conditions.

 

[SpeedKrazy620]

Cars are actually faster when it's colder. Because air particles are closer together when it's cold allowing more air into the engine. So if your gettin ready for a race, start up your car and go, go, go!

 

[daan]

What you on about? It's only the outside air temperature that matters there. That means that if it's cold air going into the engine, then the engine works better but it still has to be warmed up to let the oil flow round and lubricate. If the engine is cold, the oil won't protect as it should.

 

[Goomba]

I've been letting my car warm up for a good amount of time before I take off, and still drive it light, keeping it under 3,000 rpms. Well... Tomorrow sure as hell will be different!

 

[Thio]

Originally posted by SpeedKrazy620
Cars are actually faster when it's colder. Because air particles are closer together when it's cold allowing more air into the engine. So if your gettin ready for a race, start up your car and go, go, go!

Wrong idea, 620.

The car is faster when the outside air is colder. If you run your engine cold, you're going to start hearing your valves knocking the head off of the block, and that's what you don't want if you want to keep your car running for 100K+ miles. Even worse, you might blow a piston or gasket or something. If you're rich enough, you can just swap out the old engine with a completely new one

Some engines are designed to run cold, like GM's Hot Blood engines. Those were designed to run off of the spot, but sports cars are different. In order for the full potential can be used, all the components have to reach operating temperature.

 

[neanderthal]

Originally posted by Thio
Yeah, but the transmission shifts really high when the engine is cold on my parent's car (1995)...

I guess the transmission needs to be warmed up also?

the transmission is not really gonna get warm until you drive or idle the engine for a long time. and by that i mean something like 5 minutes or so.

the fastest way to warm up your car and all its components is to drive it.

 

[GilesGuthrie]

Originally posted by BMW POWER
i dont want to go to far off topic or anything but my Audi is a turbo and someone at work (he owns an MR2 turbo) said i should let the car warm down after driving to prevent the hoses in the turbo from getting bloked up or something. i dont really pay any attention to this but i was just wondering if it was true or not?

This is correct. It's because the turbo gets very hot, and while the engine is running, the oil pump is moving oil through the turbo housing, helping to take the heat away. If you stop the engine, all the heat goes into the oil immediately surrounding the turbo. This can "cook" the oil causing it to solidify. Which is a bad thing.

 

[skip0110]

Originally posted by GilesGuthrie
If you stop the engine, all the heat goes into the oil immediately surrounding the turbo. This can "cook" the oil causing it to solidify. Which is a bad thing.

Unless you get a turbo timer, which keeps the oil pumping after the car is shut off.

 

[neanderthal]

also, the turbo continues to spin after the engine is turned off. so, if youve just come from a long hard drive and you turn the car off, the oil will no longer circulate while the turbo still spins.

thats why its imperative to keep the car idling for a minute or two after a long hard drive.

 

[SpeedKrazy620]

Oh, sorry. Got mixed up, I thought it was the temperature of the engine that made it faster. (Thank god I dont drive yet) lol

 

[Thio]

Hijacking the thread!

How fast does the turbo spin? ~200K RPM?

 

[Tofu4G63]

Originally posted by M5Power
Temperature or not, a friend of mine had a brand new top-line CR-V stolen out of his driveway about two months ago with $4000 of computer equipment inside when he was letting it warm up. I'll take the "less engine life" trade off.

Take 2 dollars to the hardware store for a second key..... start the car.... lock it....... use second key to open.

 

[Tofu4G63]

Ok...... I have a thought on all of the hearsay about letting cars warm up or not.

The quickest way to let a car warm up to operating temperature: Driving it. Why does it warm up faster? You are putting a load on the engine.... actually making the oil protect the metal componenets. When you drive..... even slowly keeping the engine speed you are putting alot of stress on the motor as compared to idling. Pulling around 2000-5000lbs of vehicle is alot more work than just sitting there only doing enough to run. I think its easier on the car to idle up to temp.

Another thing....... have you ever noticed on old cars and new cars alike that when starting the car up on a cold morning the RPM's are alittle bit higher? Around 1500RPM. This is computer controlled on new cars and mechanically done on carbureated cars. This was designed for a reason. This lets the car get to temp alittle bit quicker. So for those of you with computer controlled cars that say that driving the car right away is the best way....... are you saying the engineers let that happen by mistake? Did you just pay someone thousands for that vehicle and then say I dont think your way is the right way?

And for the person who's carbureated car must be revved up to keep idle on a cold morning, your choke is sticking. You can get out and manually move the choke to avoid this having to rev up a cold car deal every morning.

 

[Giancarlo]

Get an automatic start keychain kit for your car. Just turn on the car when you get out of bed, and by the time you get out, the car will be ready to go. Just unlock the door, trun the key, and drive off.

My brother has one of those on his truck.



EDIT:

Originally posted by Der Alta
Click and Clack. The Radio wonders of the world.

http://cartalk.cars.com/Columns/Archive/2003/May/03.html

I read that link, and it says it's a waste of gas to leave the car running... but doesn't most of the gas in a car only get used when you're accelerating? And what's the difference between pollution from your car sitting in the driveway and pollution from a car driving though it?

 

[///M-Spec]

Originally posted by Tofu4G63
So for those of you with computer controlled cars that say that driving the car right away is the best way....... are you saying the engineers let that happen by mistake?

Why then would the engineers who designed the car turn around and tell the press dept. to publish "drive away immediately" in the owner's manuals? Are you saying that the press folks purposely printed the opposite of what the engineers told them?

The high idle of the cold start process has more than one goal. Yes, it is designed to get some heat into the engine, but it is primarily engineered to maintain cold idle and cope with the rich A/F ratio, which in turn is to help atomization in a cold combustion chamber, lest there be stumbling and the engine falling dead.

In addition, a car that is idling in the ECU cold start 'open loop' will also make much more pollutants than a fully warm car --in turn making it tough on the catalytic convertors, which are very temperature sensitive. Everytime you let the car idle until warm, it's sitting there running rich, dumping unburned fuel into the cat --can't be good for longevity.

Either way you decide to go there will be engine wear everytime you start it. I'd rather subject my motor to slightly more stress under load for 2 minutes until it warms up than subject it to very little load, but for 10-15 minutes at lower temps.


///M-Spec