Glow plugs

I have an SD4 due in March. Having never had a diesel car before, I wasn't aware until reading the on-line manual that diesel engines still use glow plugs. The reason I say this is that I have a boat with Volvo D6 diesels which don't have glow plugs. From what I can gather, the high compression alone is enough to raise the mixture to ignition temperature. The design is very effective, as, even from winter cold, the engines start the moment you turn the key (so quickly you don't even discern any cranking).

May I ask of those who have Evoque diesels how quickly they start from really cold temperatures? Also, as they don't have auxiliary heaters, how quickly does the engine warm sufficiently to heat the car? As an aside, does anyone know why auto diesels use glow plugs when there are optional designs? Is it just a lower compression issue? Thanks!

The other day at -6 I pushed the button and it took about 5 secs for the glowplug light to go out before starting.

Car is warming in minutes.

(07-02-2012 06:35pm)cjfp Wrote:  The other day at -6 I pushed the button and it took about 5 secs for the glowplug light to go out before starting.

Thanks. That seems quite a long wait to me! (Pleased to hear the car warms up quickly, though).

It's the only time I've had to wait more than 1 sec.

They are pretty quick, it takes my Defender 10-15 secs at normal temperatures for the glow plug light to go out

(07-02-2012 07:25pm)XFullFatTim Wrote:  They are pretty quick, it takes my Defender 10-15 secs at normal temperatures for the glow plug light to go out

It sounds as if they are as good as they can be. I have no basis for comparison car-wise, but I still wonder why glow plugs are needed (as discussed in my first post).

Any diesel engine specialists here to explain? Here is the Wikipedia explanation http://en.wikipedia.org/wiki/Glowplug

Uh......I think I prefer blissful ignorance rather than trying to understand how it works and I guess I can wait a few seconds to start the car.

(07-02-2012 08:09pm)Donny Dog Wrote:  It sounds as if they are as good as they can be. I have no basis for comparison car-wise, but I still wonder why glow plugs are needed (as discussed in my first post).

i have no direct industry experience, but I would hazard a guess that igniting purely by compression would require extremely high compression ratios, which combined with the reliability and mass-productivity required in cars would make it too expensive?

I do however, believe there are some cars out there without glow plugs, I believe the dodge ram is one, but it heats the diesel in the inlet before it is injected... So it has a similar effect as a glow plug, just via different means.

I dont know how long marine engines run for before an overhaul... 5000hours? 10,000hours? Not sure I could see them running for 200,000hours without work, which is what I think you should expect from a production car.

The marine engines I deal with - really BIG ones not matchbox sized boat engines - don't have glow plugs at all, the fuel is preheated to very high temperatures before it gets to the fuel injector, also to start the engine we use compressed air to "blow" the engine over and momentum does the rest.
Big marine diesels run until they breakdown these days, its the ancillaries that get all the maintenance rather than the actual engine. The engines I sail with are very very big like 13.5m high weighing in at some 3000 tonnes. Take a look at the Wartsilla Sulzer RTA96c http://en.wikipedia.org/wiki/Wärtsilä-Sulzer_RTA96-C