Warm Up Time

[OldRaver]

Well I've had the Rav for nearly a week now -really enjoying although getting used to a manual box after 10 years of driving autos will take some time (why? well going down to one car only now and the better half can't do autos) The question is that compared to many other cars I've had the warm up time for this diesel seems to be quite long. Is this normal?

Grateful for your opinions. Thanks

[Big Kev]

Well I've had the Rav for nearly a week now -really enjoying although getting used to a manual box after 10 years of driving autos will take some time (why? well going down to one car only now and the better half can't do autos) The question is that compared to many other cars I've had the warm up time for this diesel seems to be quite long. Is this normal?

Grateful for your opinions. Thanks

Hi Raver,

Totally the norm....my 2.2 Avensis and now my 2.2 Rav4 exactly same. If there was a "blind" system similar to what Kenlowe Fans used to do many years ago, I would blind off radiator and move only when heated up.

Anchorman, man.....do we see a business opportunity, or should ah just continue drinkin'?

Regards,

Big Kev.

[Davrav]

Well I've had the Rav for nearly a week now -really enjoying although getting used to a manual box after 10 years of driving autos will take some time (why? well going down to one car only now and the better half can't do autos) The question is that compared to many other cars I've had the warm up time for this diesel seems to be quite long. Is this normal?

Grateful for your opinions. Thanks

Had exactly the same query when I got my diesel RAV.

As Big Kev says, it is quite normal. Diesel engines are, as Anchorman pointed out when I raised the question, much more thermodynamically efficient compared to petrol engines.

From what I remember, if you set the aircon to demist, an electric heater provides supplementary heat until engine is sufficiently hot enough.

I raised the question with 'Honest John' on Times online and his response was that blinding the rad would not be much use [because of the thermodynamic efficiency] but that it might be worth considering an engine pre-heater if cold starting was a real issue. Kenlowe do one which is quite expensive and so does MrT but I bet that is mega expensive.

[anchorman]

Here we are 2009 and I still regularly cover my knees with newspaper when I'm driving my train so that the draughts don't completely paralise me!!!

This takes me back to the 70's when we used to lag up the old Fodens to satop them freezing on the inside when we were driving them. Dave is right. Not much point lagging them as it isn't the ram air thats causing the problem (the engine thermostat effectively shuts the flow of coolant off) it is the very high thermal efficiency that just puts all of the heat generated out through the exhaust.

You can speed things up a bit by turning the A/C off (even though it defaults to on) and turning the heater intake over to recirculate but it is fine balance in doing so as both will cause the windows to mist more.

Other than that those free Metro's work wonders if you have them about 3 thick!!!

I think paper recycling is the future Kev.

[Jamesbelfast]

Diesel engine are slower to reach optimum operating temperature than petrol engines because the ignition temp of diesel is 210C whereas petrol is around 250C. Modern diesel engines tend to heat slower because many have EGR valves fitted which reduce the combustion temperature further still. Any internal combustion engine will heat faster the greater the load applied - so by switching on the air-con, loads of electrics will help speed the warming up process. On the other hand cold engines don't like being abused.:)

[anchorman]

From Wikipedia

"The diesel internal combustion engine differs from the gasoline powered Otto cycle by using a higher compression of the air to ignite the fuel rather than using a spark plug (compression ignition rather than spark ignition).

In the diesel engine, only air is introduced into the combustion chamber. The air is then compressed with a compression ratio typically between 15 and 22 resulting into a 40 bar (about 600 psi) pressure compared to 8 to 14 bar (about 200 psi) in the petrol engine. This high compression heats the air to 550 °C (1,022 °F). At about this moment (the exact moment is determined by the fuel injection timing of the fuel system), fuel is injected directly into the compressed air in the combustion chamber. This may be into a (typically toroidal) void in the top of the piston or a pre-chamber depending upon the design of the engine. The fuel injector ensures that the fuel is broken down into small droplets, and that the fuel is distributed as evenly as possible. The more modern the engine, the smaller, more numerous and better distributed are the droplets. The heat of the compressed air vaporises fuel from the surface of the droplets. The vapour is then ignited by the heat from the compressed air in the combustion chamber, the droplets continue to vaporise from their surfaces and burn, getting smaller, until all the fuel in the droplets has been burnt. The start of vaporisation causes a delay period during ignition, and the characteristic diesel knocking sound as the vapour reaches ignition temperature and causes an abrupt increase in pressure above the piston. The rapid expansion of combustion gases then drives the piston downward, supplying power to the crankshaft.[12]

As well as the high level of compression allowing combustion to take place without a separate ignition system, a high compression ratio greatly increases the engine's efficiency. Increasing the compression ratio in a spark-ignition engine where fuel and air are mixed before entry to the cylinder is limited by the need to prevent damaging pre-ignition. Since only air is compressed in a diesel engine, and fuel is not introduced into the cylinder until shortly before top dead center (TDC), premature detonation is not an issue and compression ratios are much higher."

While loading the engine will undoubtably decrease warm up time, using the A/C is counter productive in warming the interior as the incoming air is chilled during the process.

Wiki article;

http://en.wikipedia.org/wiki/Diesel_engine#Major_advantages

[Big Kev]

From Wikipedia

"The diesel internal combustion engine differs from the gasoline powered Otto cycle by using a higher compression of the air to ignite the fuel rather than using a spark plug (compression ignition rather than spark ignition).

In the diesel engine, only air is introduced into the combustion chamber. The air is then compressed with a compression ratio typically between 15 and 22 resulting into a 40 bar (about 600 psi) pressure compared to 8 to 14 bar (about 200 psi) in the petrol engine. This high compression heats the air to 550 °C (1,022 °F). At about this moment (the exact moment is determined by the fuel injection timing of the fuel system), fuel is injected directly into the compressed air in the combustion chamber. This may be into a (typically toroidal) void in the top of the piston or a pre-chamber depending upon the design of the engine. The fuel injector ensures that the fuel is broken down into small droplets, and that the fuel is distributed as evenly as possible. The more modern the engine, the smaller, more numerous and better distributed are the droplets. The heat of the compressed air vaporises fuel from the surface of the droplets. The vapour is then ignited by the heat from the compressed air in the combustion chamber, the droplets continue to vaporise from their surfaces and burn, getting smaller, until all the fuel in the droplets has been burnt. The start of vaporisation causes a delay period during ignition, and the characteristic diesel knocking sound as the vapour reaches ignition temperature and causes an abrupt increase in pressure above the piston. The rapid expansion of combustion gases then drives the piston downward, supplying power to the crankshaft.[12]

As well as the high level of compression allowing combustion to take place without a separate ignition system, a high compression ratio greatly increases the engine's efficiency. Increasing the compression ratio in a spark-ignition engine where fuel and air are mixed before entry to the cylinder is limited by the need to prevent damaging pre-ignition. Since only air is compressed in a diesel engine, and fuel is not introduced into the cylinder until shortly before top dead center (TDC), premature detonation is not an issue and compression ratios are much higher."

While loading the engine will undoubtably decrease warm up time, using the A/C is counter productive in warming the interior as the incoming air is chilled during the process.

Wiki article;

http://en.wikipedia.org/wiki/Diesel_engine#Major_advantages

Thanks Anchs,

Extremely educational bits......gone are those simple days of fitting Niki carbs to air cooled Beetles, to eek out that extra 3.87 hp!!!!!!! Then the blessed thing froze in October....and I mean they iced up in wet cool weather....never did seek a proper explanation.

And as for the Foden....is that no where your enemies hide?

Big Kev

[OldRaver]

Just want to say many thanks for this info - this is my first diesel so very much a newbee in this zone. Can relax on that front now....

Pleased to say that the Rav had the camshaft belt replaced at 60K and more recently the DMF and clutch (about 3k before I bought it -now at 67K miles) - I thought this wasn't needed with 04 vehicles as a mod had been made to prevent the DMF coming apart? but as I said I'm just a newbee and lots to learn. Thanks again for the replies.