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Old 13th March 2004, 22:06   #1
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hi guys....
I had 2 questions in mind:
1. When we start the car first time in the morning , do we have to idle the engine for a minute or 2 ?
2. Can we switch on the A/c immediately or it's better to wait for the engine to reach it 's optimum temperature and then switch it on?

What i do is when i start the car first thing in the morning i allow it to idle for about 30 to 60 seconds and start driving it. I keep the engine at low revs till the engine reaches it's optimum temperature and then i drive normally. i switch on the A/c too after the engine temperature gauge has reached it's optimum level. I tried to do some research on this and nowhere did i read that u got to let the engine idle for a few seconds/minute before driving. Fiat india's website clearly states that u don't need to idle today's hi-tech cars at all. All u got to do is drive it at low rev's till the temperature reaches it's point and then drive normally. Nothing is mentioned about when to switch on the A/c
can anyone help?
Thanx
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Old 13th March 2004, 23:47   #2
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i guess its OK to switch on the a/c while lettin the car idle for sometime.
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Old 14th March 2004, 04:22   #3
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Hey Amit,

Idling the car when u start it for the first time in the day (especially when cold) is a really good practice. Let me give you a couple of reasons why>
1. Engines are made of metals, and metals expand and contract according to temperature. The way engines are manufactured is to have the perfect clearances between the moving parts when the engine has been brought to the right temperature range and all the parts have expanded to that degree and hence glide over each other rather than scraping each other (to put it simply).
2. Lubrication - After a long rest all the oil that was in the passageways of the engine, lubricating the cams and especially the highest parts (sometimes the fastest working parts) of the engine has all drained back down into the sump thanks to gravity. Now u can imagine how EXTREMELY bad it is for your engine to run without oil. And for the first few seconds that u crank up your car that is exactly what is happening, until the oil pump manages to get the oil completely flowing. (Essentially there is nothing u can do about this (except maybe use "magnetic oil" but im not sure how much of a gimic that is) but the point is that you should not be putting any load on your engine in these few seconds. Something like 60%* of engine damage happens when starting your car. (*Please correct my figure guys...)
3. Automatic cars, (esp. older ones?) need some time to get the auto-fluid up to temperature and flowing around nicely. I dont know about newer/other autos, but in my 1983 W123 200 if i dont idle for atleast a minute the car will NOT move at all.
4. TC'd cars say that they have to be idled when starting up and when shutting off. Doing this when starting up enables the TC to actually start spinnnig a bit, otherwise the turbine will be causing problems for the exhaust airflow, this also warms the turbo up slowly. Idling for a minute or 2 before shutting off allows the TC to spin down and cool off, because they run VERY VERY hot (ie. the actual turbine and compressor blades) and letting them cool gradually increases their life.
5. Since India is a place of many wonders, it is also good to idle your car in the morning so that it gives enough time for the mice cats dogs snakes people and maybe even cows to wake up and leave before the car gets into motion!

About the AC, it is an extra load on the engine, so it is better to keep it off. Running the AC would be the same as say driving on a flat road once you have got speed.(<= just making a vague example between AC and driving for this explaination purpose)

I personally idle my cars for as long as possible (wihtout the AC on) when i start esp. since the first thing it has to do it go up a steep slope. This sometimes irritates people but then i just tell them that i care about my car more than them so they can stuff it. hahaha

cheers
Rehaan.

Quote:
Originally Posted by [b
Quote[/b] (v12 @ Mar. 13 2004,22:17)]i guess its OK to switch on the a/c while lettin the car idle for sometime.
Ofcourse V12 has a point.
I guess it all depends on how hot it is ;-] ! Running the AC isnt gonna KILL your car, but id still wait 25secs minimum before the AC.

cheers

Last edited by v12 : 26th September 2009 at 22:12.
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Old 14th March 2004, 04:51   #4
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Rehaan,

I could not have put it better myself. Just one comment, in TC'ed cars - say like the Sierra Turbo - While the engine redlines at 4000 odd rpm, the Turbo can run as high as 150,000 rpm. The turbo in these engines relies solely on the engine for its lubrication, hence the need to idle the engine for a minute.

Would not want to run at that high an rpm without oil now, would we?

GTO
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Old 14th March 2004, 05:07   #5
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Absolutely right GTO,

The speeds at which some turbos spin is mind boggling!!!

cheers
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Old 16th March 2004, 07:54   #6
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I think rehaan said almost all the reasons behing idling of engine in the morning . So when runnig the engine itself is not good , then it goes withiout saying that the engine should not be loaded . And one more reaosn for warming up is that in the cold condition the oil is less viscous ,a dn so has greater resistance for flowing . So even if is passes through all the system it may not lubrigate completely.
But after warming up the Lube is set and lubricate the whole system completely .
And this is one of the reason that when we drain oil from the engine , we warm up ad then we drain the oil so that the comaplete oil is drained out !!
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Old 16th March 2004, 08:07   #7
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Hey good point toyota!

Even with multi-grade oils (ie they are designed to stay near ideal viscocity at all temperatures) they still do thin out a bit when heated and get into those tight places in the engine a lot better.

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Old 16th March 2004, 14:06   #8
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REhaan Youre right about the Automatic transmission . Like your Merc even my Zen to be idled for say a minute after its parked stationary for a long time. It doesnt move otherwise.

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Old 16th March 2004, 17:18   #9
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So the same way engine has to be run in idle speed before turning off . Some people have a habit of raising the engine and switching it off . It is not good for the engine. Run it in idle speed for some time and then switch it off . Lets say few parts like TC, even after switching of the engine the TC s shaft rotates and take some time to stop rotating. But when you switch of the engine , the oil pump is stopped and the oil pressure comes down and so the shaft will not be lubricated . This slowly reduces the life of the parts .
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Old 16th March 2004, 17:20   #10
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Is it true that the vehicle doest move at all when you shift to D ,when you drive A/T !
And everytime you have to idle for sometime?
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Old 17th March 2004, 00:11   #11
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Quote:
Originally Posted by [b
Quote[/b] (toyota @ Mar. 16 2004,15:50)]Is it true that the vehicle doest move at all when you shift to D ,when you drive A/T !
And everytime you have to idle for sometime?
Toyota,

Yes, Dippy and me have both stated that we experience this in the posts above

cheers
Rehaan
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Old 17th March 2004, 13:11   #12
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THis shouldnt happen i suppose in the normal driving condition . All AT do not behave like this!
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Old 19th April 2010, 14:20   #13
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Default Idling with AC for extended periods :(???

^Bump

We all do it, don't we?

With summers approaching we let the Car idle(not while starting in the morning),switch on the AC and do chit-chat/eat at road-side eateries etc where there isn't an air-conditioned place available and in general spend lots of time idling and staying in air-conditioned comfort

Does idling hamper the engine in any way?

Both Diesels as well as Petrols

^It isn't recommended to i-d-l-e a motorcycle

^^ talking about extended period of around 1 hr+
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Old 19th April 2010, 14:49   #14
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Quote:
Originally Posted by Sheel View Post
^Bump

We all do it, don't we?

With summers approaching we let the Car idle(not while starting in the morning),switch on the AC and do chit-chat/eat at road-side eateries etc where there isn't an air-conditioned place available and in general spend lots of time idling and staying in air-conditioned comfort

Does idling hamper the engine in any way?

Both Diesels as well as Petrols

^It isn't recommended to i-d-l-e a motorcycle

^^ talking about extended period of around 1 hr+
I don't think that extended period of idling impacts the engine in any way if the cooling system is working fine. Generally the radiator along with fan will try to dissipate the engine heat, the bonnet might feel some degrees hotter.
A note of caution is that always idle a car in open area which has free air movement else danger of CO poisoning is possible.

Motorcycles generally have a air cooled mechanism hence should not be idled more as the engine run hotter due to lack of air movement over the engine fins.
Even a liquid cooled bike tends to over heat under idle condition as there is not much air to dissipate the heated generated by the engines. Excessive heat damages the engine components resulting in truncated life of the engine.
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Old 19th April 2010, 15:32   #15
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Does the observations made in 2004 above still hold true with newer generation cars with new technology?

A few google searches seems to suggest that running a/c while idling is okay provided the temperature guage is within limits.

So asking again..is it ok to run the a/c while idling, and at the same time, working on a laptop connected to 12V socket (have done a couple of times on highways) for around 30 mins or so? FE apart, will it reduce engine/battery life to a significant extent?
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