[eye30]

I've just read an article on another forum that YOU SHOULD NOT let a diesel engine idle to let it warm up on cold frosty mornings so you can use the warm air to clear the front window of frost.
They indicate that due to its construction and the way it works in general, diesel engines takes way longer to warm up compared to an similar petrol engine.  
They also say the diesel engines convert its energy into power rather than into heat, which happens in a petrol engine.

Does anyone have any views?

[Shambles]

Never really gave it much thought to be honest eye.

I let Fergie warm up this morning as it was frosty (3 mins or so), but it took ages to get any heat thru the dash and clear the windscreen.

Diesels work via high compression rather than combustion so I believe, so I expect it will take longer to warm up.

[TheBunyip]

This subject has also come up in Mazda3 forums. If I recall correctly the same recommendation was made there. DO NOT IDLE when first starting... Apparently in Germany it is against the law to do so. Diesels must drive off as soon as the engine is started. Although no mention was made of anyone in trouble with Officialdom so I cannot guess if German Diesel drivers who IDLE are prosecuted.

On an American web site I found a warning against Idling of Diesels on startup. Cummins Diesel had this to say..."If it's not severely cold out and you're using high quality, clean 15W-40 engine oil or 10W-30 below 70 deg. F, you may start the engine, let it idle for 10-15 seconds and slowly drive away (at modest power levels) with no ill effects."

So... has anyone ever tried one of those "Ceramic" plug in Demisters to clear the windscreen on cold mornings

[Shambles]

I'll tell you what - no way would I drive off after a few seconds while my windscreen was frozen up.  

[TheBunyip]

Hi Shambles,

I'll tell you what - no way would I drive off after a few seconds while my windscreen was frozen up. :?:  Or are these devices just toys   .http://cgi.ebay.co.uk/ADVANCED-CERAMIC-CAR-HEATER-COOLER-WINDSCREEN-DEMISTER_W0QQitemZ220289311954QQcmdZViewItem?hash=item220289311954&_trksid=p3286.c0.m14&_trkparms=72%3A1301%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318

If not I too am back to continuing to IDLE until the screen thaws out.[/color]

[Shambles]

Does anyone know if something like  this would do the job. :roll: .http://cgi.ebay.co.uk/ADVANCED-CERAMIC-CAR-HEATER-COOLER-WINDSCREEN-DEMISTER_W0QQitemZ220289311954QQcmdZViewItem?hash=item220289311954&_trksid=p3286.c0.m14&_trkparms=72%3A1301%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318

Thanks for that - I just ordered one (from cn-ice.com - £19.99 delivered next day) I'll let you know what it's like

[Shambles]

Does anyone know if something like  this would do the job. :roll: .http://cgi.ebay.co.uk/ADVANCED-CERAMIC-CAR-HEATER-COOLER-WINDSCREEN-DEMISTER_W0QQitemZ220289311954QQcmdZViewItem?hash=item220289311954&_trksid=p3286.c0.m14&_trkparms=72%3A1301%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318

If not I too am back to continuing to IDLE until the screen thaws out.

Just been out and put a 20A fuse in the power outlet (existing 15A fuse wouldn't be enough - 200W @ 12v = 16.7A)

I can officially confirm that this particular model of "demister" is a toy. And not a very good toy. Started the engine then switched it on. It has a OFF/FAN/HEAT button and one for FAST/SLOW.

I set it to FAST HEAT.

The motor runs too slowly to do general coverage of the windscreen. It would have to be moved around like a hairdryer. And it didn't get hot at all, just warm.

So, stay clear of this gadget.

I'll be keeping my eyes open for others to try.

[Zhangster]

just wanted to tell u about the difference of petrol an diesel fuel.. as shambles said : Diesels work via high compression rather than combustion is one thing... but the most important thing about is :

if u have 1liter of fuel = 100% energy.

Petrol will convert 25% of the energy into power and rest is pure heat which make it heat up way faster than a diesel engine.

compared to the petrol engine.. diesel engine will convert around 40% or more ( cars like vw lupo)

which means less useless heat...

hope u get my point here

cheers

Never really gave it much thought to be honest eye.

I let Fergie warm up this morning as it was frosty (3 mins or so), but it took ages to get any heat thru the dash and clear the windscreen.

Diesels work via high compression rather than combustion so I believe, so I expect it will take longer to warm up.

[Dazzler]

Thanks dpo .. interesting info..

[LuciferDarklord]

Because diesels have a high compression ratio, they have less surface area of head in the combustion chamber.  Generally DI diesels have a flat head, with a toroidal combustion chamber in the top of the piston.  This makes them very thermally efficient.  In the mid-90's Isuzu made an experimental diesel engine with ceramic inserts in the head, valves and piston crown.  It had no cooling system at all!

[2i30s]

if its illegal in some country's to let a diesel idle on cold start up,how on a truck/lorry would you be able to stop with no or little air in the braking system,be able to see out of the windows on your car or truck.this seems a little dangerous to me.but i suppose if the engine was fitted with a block heater the engine would allready be warmed up enough to clear a frosty windscreen. but that still wont help you with the air brakes problem on a heavy vehicle.  [sorry about posting in an old thread and going off topic a bit.]

[MRH130]

I'd let it idle for about 30 seconds and then drive off gently. You don't need to let it idle longer than that but you do want to make sure that the oil is circulating and reaching all the important bits before you put the motor under ANY stress. Don't give it a big squirt until it's properly warmed up.

The exhaust emissions will be worse when it's cold which would be why some countries ban idling cold diesels.

But driving away immediately after starting the motor is bad for the engine and I certainly wouldn't do it (unless I had to by law, and if I did I would drive away at idle).

[clackerz]

I never realised this for diesels.
I always let the engine sit - usually around for 1min.  In the Territory it was enough to get the engine warrm.

I noticed that the diesel takes alot longer.

Today I only let it idle for around 20 secs and then drove off carefully until the engine is warm.

Applying only my own simple logic to this question; I reckon it would take so long for our little (and very efficient) diesel to generate any useful heat running at a dead idle to make it not worthwhile and perhaps detrimental.

Apart from demisting, which is a different problem, the idea is to get the temperature up as quickly as possible while at the same time not running the engine too hard while still cold. It's obvious these two requirements are somewhat opposed and a happy medium needs to be taken.

My approach is to let it idle only for the few seconds it takes to adjust the seat belt and check mirrors and the road behind before backing out then driving off very moderately yet with sufficient pedal to do enough work to generate some heat. Incidently, I also let it run for these 10 or 15 seconds with the clutch out to get the gearbox bits coated as well. Unless there is something wrong with the engine (or the oil) I also believe that this is sufficient time to get oil to all the right places.

Consider this hypothetical: If you lived halfway up a long hill and could choose to start your trip going either way would you choose to drive up the hill or down? Perhaps counter-intuitively, I'd drive up the hill to get some heat into the engine and oil as soon as possible. If you drive down, you will burn less fuel and if the hill is steep you might even have to go down with a closed "throttle" so that the engine just spins around cold not getting warm at all apart from a little friction. 

Adapt this scenario to your daily startup is my suggestion. Of course if you can't drive off because you can't see then make your own arrangements.

[agentr31]

ask yourself, this do you get out of bed and the first thing you do is start running around, jumping, yelling, playing, hop-scotch and weights??

no that would be silly you havent "warmed up" and even when you do go and do these activities you "warm up" dont you? or you can cause damage

same goes for an engine...

i usually have a smoke and let the car warm up while im smoking...

[2i30s]

wont putting the aircon in the demist position on screen flat out ,defrost  the front screen,that issue is solved.  

[agentr31]

not if you have frost on the outside!!!

[2i30s]

so that put a stop to my idea. 

[agentr31]

:o

ask yourself, this do you get out of bed and the first thing you do is start running around, jumping, yelling, playing, hop-scotch and weights??

no that would be silly you havent "warmed up" and even when you do go and do these activities you "warm up" dont you? or you can cause damage

same goes for an engine...

i usually have a smoke and let the car warm up while im smoking...

I don't think anyone is suggesting a warmup is unnecessary. What is being discussed is what method might be best.

[2i30s]

in eye30's original post it says, he only read the suggestion that you shouldn't warm up a diesel engine at all on a Mazda forum.I'm no engine expert but I've spent a lot of time working around these engines and i have noticed that most if not all truck drivers start the engine from cold and leave it running while loading it.i used to do it myself as a driver years ago.the fire pumps i make at work are tested prior to leaving the factory as a quality assurance thing.we start them up on the maximum rpm and run them flat out for an hour non stop,they don't get a chance to idle. 

[Dazzler]

I'm with Pip and others who just slip on their belt and drive off carefully the engine warms up much more quickly than if you just idle on the spot and you are using your fuel to go somewhere..

[2i30s]

 

[Lorian]

I'm with Pip and others who just slip on their belt and drive off carefully the engine warms up much more quickly than if you just idle on the spot and you are using your fuel to go somewhere..

It's not very practical for folk who are parked in the open in freezing weather though. Sometimes you just have to burn that fuel for heat.

[Dazzler]

I'm with Pip and others who just slip on their belt and drive off carefully the engine warms up much more quickly than if you just idle on the spot and you are using your fuel to go somewhere..

It's not very practical for folk who are parked in the open in freezing weather though. Sometimes you just have to burn that fuel for heat.

True, I am very much enjoying a large garage with remote door after around 12 years of parking out in the open (frost and all)

I used to remove the frost from my windows (carefully) with a bucket of luke warm water.. then drive off carefully...

[clackerz]

I'm with Pip and others who just slip on their belt and drive off carefully the engine warms up much more quickly than if you just idle on the spot and you are using your fuel to go somewhere..

It's not very practical for folk who are parked in the open in freezing weather though. Sometimes you just have to burn that fuel for heat.

Use The Force Luke........

[Lorian]

Use The Force Luke........

Burning midich-lorians will not help in this instance 

It's not very practical for folk who are parked in the open in freezing weather though. Sometimes you just have to burn that fuel for heat.

Indeed, if you have no alternative other than to use your poor diesel engine to defrost your car then so be it.  Just accept that so doing might not be extending its life and in any case earlier driving off rather than later is probably better.

In most states of Oz we are so lucky that sub-freezing temperatures are not as common as in other parts of the world (except for Canberra!) such that the secondary problem here discussed of warming the car itself is almost moot.

An analogy might be using those high wattage incandescent lights (petrol) in the bathroom to warm you because they make more heat than light, compared to using fluorescent lights (more light than heat). You can run the fluorescent light forever but you wont get warm. I've often gotten to my destination before my feel have thawed... the heater is quite ineffective for the first 10ks or so.

I really don't know why it became popular to idle diesels to warm them but I'd guess that due to the relatively low-tech, truly agricultural engineering in their early implementations that they quite possibly were barely drivable before they were significantly warmed.

Lakes has driven a few trucks if I recall. If he's about he might offer some historical insight.

[sgreeno]

indeed, in the UK, most of us in winter have no chance but to leave the car warm up. yeah, there are ice scrapers and de-icing sprays etc, but the mist on the inside of the wondow takes a good few minutes to clear to be able to drive safely!

[whitbomb07]

My car is parked out on the street and quite often I'm heading off to work before sunrise.

Temps are normally low single digit, Lots of water/sometimes frost on the outside, mist on the inside.

I have a hand towel to deal with mist on the inside, water on the window and side mirror. Then I give the widnscreen a squirt and wipe with the windscreen wipers, start up and go staright away.

I use my Scangauge as a guide, unfortunately it only shows water temp and not oil temp and pressure. I don't even consider driving it hard until the water temp is in the normal operating range (84-87C)

Until it's hot I granny it very carefully and gently, short shifting not going much over 2000rpm.

I've heard that leaving modern Diesels idling can cause glazing on the cylinders, but I have no proof of it, just something that I heard.

Interestingly I just read that the new European 2011 Ford Mondeo will make use of a system the closes up the engine bay to assist the engine in warming up quicker, it then opens up once the engine is warm.

Can anyone confirm that the heating system is still based on using water from the radiator? I know cars of yesteryear used this to provide heating, but not if modern cars do still.

Regards

Daniel