Distributor affecting perfomance?
Distributor affecting perfomance?
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MMA4life

Original Poster:

810 posts

186 months

Tuesday 19th October 2010
quotequote all
Hi guys & girls

The other day I took my mk3 polo 1.6 to the garage as it had been running very sluggish ever since I bought it. Didnt think of it as I thought it was just due to its age, but then I drove the mothers 02 plate 1.2 punto and found it was so much quicker. My brother also drove me polo and said it very underpowered.

The mechanic said the distributor cap had been turned far and therefore causing the spark plugs to fire a bit later resulting in poor performance. Once he had changed the position of the distributor slightly, it drove so much better.

Therefore, how does the timing of the firing of the spark plugs due to distributor affect performance? I.e. spark plugs firing early or late

Cheers for your help.
MMA4life

shouldbworking

4,796 posts

236 months

Tuesday 19th October 2010
quotequote all
I can't describe it very well, but get the timing wrong and you are looking at pre-ignition, or detonation. These are effects where the ignition of the spark plug fails to produce the desired moving flame front in the combustion chamber, and instead either results in partial or complete explosion of the fuel mixture.

This results in a great deal more force being transferred to the engine components and can rapidly destroy an engine.

Someone who can word that better will be along shortly im sure smile

MMA4life

Original Poster:

810 posts

186 months

Tuesday 19th October 2010
quotequote all
shouldbworking said:
I can't describe it very well, but get the timing wrong and you are looking at pre-ignition, or detonation. These are effects where the ignition of the spark plug fails to produce the desired moving flame front in the combustion chamber, and instead either results in partial or complete explosion of the fuel mixture.

This results in a great deal more force being transferred to the engine components and can rapidly destroy an engine.

Someone who can word that better will be along shortly im sure smile
Sounds alright to me smile Cheers for the explanation.

Steve_D

13,801 posts

282 months

Tuesday 19th October 2010
quotequote all
An engines power comes from compressing the fuel/air mixture then setting fire to it. As the burning gases expand they push the piston down.
If you wait until the piston has reached the top of its compression stroke before firing the spark the piston will be well on its way down before the gas expansion has a chance to get going.
The answer is to fire the spark plug before the piston gets to the top.
As you can guess, the timing of this is quite important. Too late and you've missed making the most of the burn, too early and you may be trying to stop the piston coming up.

The distributor controls this timing and actually modifies the timing depending on engine load but that's another lesson.

Class dismissed.

Steve

MMA4life

Original Poster:

810 posts

186 months

Tuesday 19th October 2010
quotequote all
Steve_D said:
An engines power comes from compressing the fuel/air mixture then setting fire to it. As the burning gases expand they push the piston down.
If you wait until the piston has reached the top of its compression stroke before firing the spark the piston will be well on its way down before the gas expansion has a chance to get going.
The answer is to fire the spark plug before the piston gets to the top.
As you can guess, the timing of this is quite important. Too late and you've missed making the most of the burn, too early and you may be trying to stop the piston coming up.

The distributor controls this timing and actually modifies the timing depending on engine load but that's another lesson.

Class dismissed.

Steve
Awesome explanation Steve smile. Mine had been firing too late grr