[DMCForum] Martin's class on basic diesel theory
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[DMCForum] Martin's class on basic diesel theory
- From: "cruznmd" <racuti1@xxxxxxxxxxxx>
- Date: Wed, 17 Aug 2005 16:46:13 -0000
Martin,
Thanks for explaining all of that. I definitely did not know that the
amount of air metered into the engine was constant at all throttle
positions.
--- In DMCForum@xxxxxxxxxxxxxxx, Martin Gutkowski <martin@xxxx> wrote:
> Volvo diesels have never been known for being very good.
>
> to say "modern" diesel is a bit different than talking about
a "modern"
> petrol engine. A diesel engine is much simpler than a petrol
engine.
> Apart from the obvious main engine differences, there are no spark
plugs
> and no throttle(s). The engine is controlled solely by the metering
of
> the fuel. You put your foot down more, it injects more fuel, the
more
> power you have. The amount injected is directly proportional to the
> position of your foot and manifold air pressure is more or less
constant
> given the lack of throttles! So basically if you want to drive a
diesel
> economically, don't have a lead foot.
>
> So how is it done? Well, the older, simpler diesels run a single
fuel
> pump, run off the cam belt that does all the work of timing the
> injection, and the throttle cable attaches to a lever on top of the
> pump. Fuel is injecte dinto the intake tract, much the same as a
petrol
> engine.
>
> The only electrical devices on the entire engine are the glowplugs,
> which work for the first few seconds on cold startup, and the fuel
> cutoff valve - which is the only way to stop it once it starts.
>
> "Modern" diesels are all EFI and more critically direct injection
where
> the fuel is injected directly into the cylinders. The VW/Audi "TDi"
> engines, also found on Landrovers are mechanical direct injection,
The
> Peugeot/Citroen and Renault engiens are all EFI. EFI does not give
much
> better economy than TDi but does give cleverer control of the
turbo, and
> given the nature of a diesel engine, a turbo suits it perfectly.
>
> Martin
<snip>
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