Scotty C
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Registered: 6th Nov 05
Location: Kidderminster Drives: 1.6 16v Sport
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Now, this is going to be a completly stupid question.
But how do they work?! Reason for asking is because my Boss has the 1.3 CDTI Corsa C and it was being a bit sluggish on start up, so I said ''put some new spark plugs in''
And his just laughed in my face  
Now, I obviously haven't a clue on diesel engines, they've never really interested me, but i'm now curious why he was laughing in my face 
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WATSON
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Registered: 16th Jun 05
Location: Fife, Scotland
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They run on glow plugs 
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pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
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Diesel doesnt need a spark to ignite, hence no spark plugs.
It ignites under compression, but the cylinder does need warming so diesel have glowplugs that warm them up before startup.
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Scotty C
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Registered: 6th Nov 05
Location: Kidderminster Drives: 1.6 16v Sport
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So if they have no spark plugs, how does the pistion get pushed down
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Rob E
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Registered: 1st Jan 06
Location: Madeley, Stafford....I want to live back in Wales!
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diesel engines use glow plugs to pre heat the cylinder when the engine is cold to make the diesel ignite 
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Scotty C
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Registered: 6th Nov 05
Location: Kidderminster Drives: 1.6 16v Sport
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Oh, wait, it ignites under compression? how the fudge does that work then?
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pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
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By the explosion that the diesel makes when it is compressed (ie when the piston goes up)
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swill_omnibus
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Registered: 12th Dec 07
Location: : S. wales Drives: Dodge Caliber
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An explanation from Nu-Car about glow plugs:-
Diesel Glow Plugs
Glow plugs are important for cold starting of diesel engined cars. They are electrically controlled heaters which warm the engine prior to cold starts. Without glow plugs, a diesel engine would not start because the engine needs hot compressed air to ignite injected diesel. Petrol cars do not require glow plugs because they operate using spark plugs to ignite a fuel/air mixture.
Diesel engines do not require complicated electronic computer management to mix fuel and air before injection into the cylinders. Air is compressed within the cylinder, when compressed the air trapped inside the cylinder and combustion chamber can reach 400-800 °C. Injectors then spray high pressure diesel into the combustion chamber which immediately ignites from the hot compressed air. This explosion then forces the piston down which rotates the crankshaft, gears and subsequently drives the wheels.
Hope this has helped
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AndyKent
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Registered: 3rd Sep 05
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Starts as a petrol car but cylinders are preheated.
Diesel is compressed, ignites under pressure and forces piston down same as petrol.
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Rob E
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Registered: 1st Jan 06
Location: Madeley, Stafford....I want to live back in Wales!
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Is your bosses car also a bit smokey when first started from cold?
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Scotty C
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Registered: 6th Nov 05
Location: Kidderminster Drives: 1.6 16v Sport
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quote:
Originally posted by swill_omnibus
An explanation from Nu-Car about glow plugs:-
Diesel Glow Plugs
Glow plugs are important for cold starting of diesel engined cars. They are electrically controlled heaters which warm the engine prior to cold starts. Without glow plugs, a diesel engine would not start because the engine needs hot compressed air to ignite injected diesel. Petrol cars do not require glow plugs because they operate using spark plugs to ignite a fuel/air mixture.
Diesel engines do not require complicated electronic computer management to mix fuel and air before injection into the cylinders. Air is compressed within the cylinder, when compressed the air trapped inside the cylinder and combustion chamber can reach 400-800 °C. Injectors then spray high pressure diesel into the combustion chamber which immediately ignites from the hot compressed air. This explosion then forces the piston down which rotates the crankshaft, gears and subsequently drives the wheels.
Hope this has helped
That helps ALOT 
Why can't petrol ignite off compression then?
quote:
Originally posted by Rob E
Is your bosses car also a bit smokey when first started from cold?
A little bit, yes.
[Edited on 13-06-2008 by Monster]
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pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
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Not as explosive I dont think.
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Scotty C
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Registered: 6th Nov 05
Location: Kidderminster Drives: 1.6 16v Sport
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It's more?
I've chucked a fag on diesel before and it didn't do anything. Then my Boss said ''if it was hotter, that diesel would of gone up...''
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pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
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Fook knows. Im no greeeesee monkehh
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AndyKent
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Registered: 3rd Sep 05
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Different type of chemical reaction I think. Petrol won't ignite under pressure without a spark source.
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Superlite Ltd.
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Registered: 9th Jan 07
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Another big difference you may get caught out on is Diesel engines don't have a throttle plate.
On a petrol when you put your foot down the throttle plate opens letting in more air (more fuel is also squirted in)
But...
on a diesel air is getting sucked in all the time at the same rate with no metering from a throttle plate. When you put your foot down it just operates the fuel pump to squirt more juice in.
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Schlumpfy
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Registered: 2nd Apr 07
Location: Stourbridge, West Midlands
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So who doesn't understand what
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Scotty C
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Registered: 6th Nov 05
Location: Kidderminster Drives: 1.6 16v Sport
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quote:
Originally posted by Schlumpfy
So who doesn't understand what
Well consdering I started the thread, it's all me.
Only thing I can't understand now is - if derv's run off compression, and pertrol is more explosvie, why isn't that run of compression?
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Superlite Ltd.
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Registered: 9th Jan 07
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toooooooooooooo volatile mate
you'd get detonation and it would blow up at the wrong time (half way through a piston stroke)
That would break an engine 
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Superlite Ltd.
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Registered: 9th Jan 07
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quote:
Originally posted by Corsa_Sport21
Petrol engines do run off compression,just not as much as diesels.
See i can be helpfull
All piston engines use compression, but diesel engines use it for ignition unlike a petrol engines that uses a spark.
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deano87
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Registered: 21st Oct 06
Location: Bedfordshire Drives: Ford Fiesta
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No idea, but just watched the Top Gear where Clarkson drives the 1.4TDi Lupo 1 lap around the M25. 119miles and he achieved 72mpg, and that wasn't dawdling 
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mattk
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Registered: 27th Feb 06
Location: St. Helens
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Deisel wont light by a spark and is instead lit by the friction and compression of the engine
throw deisel on a fire and it will more than likely put it out
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ed
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Registered: 10th Sep 03
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quote:
Originally posted by Rob E
diesel engines use glow plugs to pre heat the cylinder when the engine is cold to make the diesel ignite
They use glow plugs to pre-heat the cylinder head. They don't use the to cause ignition as diesel ignites under compression.
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ed
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Registered: 10th Sep 03
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quote:
Originally posted by pow
Not as explosive I dont think.
Diesel has a lower RON rating meaning it combusts under pressure. The higher the RON, the higher the pressure it takes to ignite the fuel under compression, hence why you need to run optimax in engines with turbos or high compression.
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Ben G
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Registered: 12th Jan 07
Location: Essex
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don't worry monster, i build them for a living and never had a clue either
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