To warm up the car, or not to warm up the car?

[ice745]

I've heard that you should warm up the car, because the metals will expand and everything will have a better fit, and have less wear.

But then I've heard that cars shouldn't be warmed up, because they're not designed to sit and idle.

Where is the happy-medium? Or are one of those statements false?

Thanks

[G-man422]

I like to warm up the car, just because it gets the engine and me warm. also it seems to be less noisy if i warm it up. I've never heard of NOT warming up your car.

[MagicRat]

Newer engines benefit more from a brief warm-up. Well-used (100k+ miles, or so) are somewhat looser inside and are slightly less likely to be damaged by use when cold.

Generally any piston powered car can be safely driven once full oil pressure and circulation has been achieved, such as within 10 seconds or so. The idea is to drive reasonably gently until its warmed up to avoid excessive thermal expansion of the pistons, (which can lead to scored cylinder walls. )

Extensive warm-ups are a hold-over from the carburetor days where cars would run poorly for at least the first 30 seconds (often longer), until the exhaust-heat for the intake manifold would warm sufficiently to help heep the fuel droplets in suspension in the intake manifold.

Also, rotary engines, especially the older ones benefit from a warm up before you drive off.

Excess engine idling is apparently a bit hard on some engine camshafts, but not all. My understanding is that it's lubrication-related but I am not sure on the actual details.

[curtis73]

Originally Posted by MagicRat

Excess engine idling is apparently a bit hard on some engine camshafts, but not all. My understanding is that it's lubrication-related but I am not sure on the actual details.

Exactly. Cam-in-block engines like older American cars have rely entirely on oil slung from the crankshaft to lubricate the cam lobes. They get almost none at idle.

Its true that a warm engine is "settled in" to its final expansion, but idling won't get it hot. The water may eventually get hot, but the oil won't. The best way seems to be if you start up, wait for the oil pressure to settle in (10 seconds or so) and then drive gently until full temperature is reached. If you just start driving hard while its cold, it will get some parts like heads and pistons really hot really fast, while the oil, bearings, crankshaft, etc stays cool for a while.

I have a foolproof way of keeping my foot out of it... I took off the secondary lockout on my carb. Now if I put too much foot in it while its cold it just stalls It keeps me from hitting it too hard while its too cold to take the punishment

[Moppie]

Originally Posted by curtis73

I have a foolproof way of keeping my foot out of it... I took off the secondary lockout on my carb. Now if I put too much foot in it while its cold it just stalls It keeps me from hitting it too hard while its too cold to take the punishment

LOL! My old Triumph used to do that. The acclerator pumps would flood it when it was cold.


A lot of modern cars have limit set on the engine when its running cold.
My old Civic for example used to disable the VTEC and lower the red line to only 7,200rpm, and I was reading a post in the SRT forum where they mentioned that the SRT4 limits boost and RPM when its cold.

[jveik]

lol i found that stuff out the hard way... waking up late for school in the winter, fire up that old 350 chevy truck... floor it out of my driveway only to find out 2 or 3 months later that my cam lobes are, for the lack of a better word, gone...

[Black Lotus]

I have two turbocharged cars, one with cast pistons and one with forged pistons.
The cast piston example I start, and drive away almost immediately-- but gently. The forged piston car, I let warm for a couple of minutes, then drive it away-- gently.

[BlueFusion6851]

I always let the car/engine sit for about 1 minute before driving away gently. I know some ****** in my grade who burns out in his truck right after starting it. He's killed the transmission in his old grand prix and grandpa's delta 88 doing R to D burnouts So morale of the story, Warm it up, yo!

[beef_bourito]

and don't screw around with your tranny.

[kcg795]

I just fire it up, wait for the oil pressure gauge to reach normal pressure. Then I drive gently until overdrive kicks in. Some cars will not engage overdrive until coolant temperature is at least 120 degrees. I leave the heater off and in the COLD position as well. Leaving the heaters off allows faster warm-up for the engine. Once the temperature gauge starts to rise, then I start turning on the heat.

[jveik]

so as for the question about if idling is bad for an engine, am i safe to say that any engine with a pressurized oiling system i.e. an oil pump is probably not negatively affected by idling? i can see where oil slung engines would have problems... i bet the original smallblock chevy had that problem, as i dont think they had pressurized oiling the first year they made em...

[rubix777]

My transmission seems to shift a lot better when the car's warmed up for a minute or so.

[curtis73]

Originally Posted by jveik

so as for the question about if idling is bad for an engine, am i safe to say that any engine with a pressurized oiling system i.e. an oil pump is probably not negatively affected by idling? ..

I may have misled... Its not one or the other. Most pressurized oil engines (which is all these days as far as cars are concerned) with cams in the block rely on slung oil for the cam lobes. For instance, a Chevy 350 has an oil pump and it oils main and rod bearings, cam bearings, and valvetrain, but since the lobes themselves are hanging out in the middle of nowhere where they do their work, there is no pressurized oil getting to them. The lobes themselves rely on oil thrown from the crankshaft.

[dambro24]

if you read a bmws manual it says not to warm up the car , turn it on drive away and just keeping the rpms low until the cars temp gaue is in the middle

[mr_mushroom]

i have to wait around a minute or so in the mornings. sometimes more on cold days. any gas will flood it out and it will die.
ahh performance.
it idles stupidly low for a moment, then warms up.