Date: Mon, 8 Dec 1997 02:14:38 -0700
Reply-To: Jerry Hart <harte@BVSD.K12.CO.US>
Sender: Vanagon mailing list <Vanagon@Gerry.SDSC.EDU>
From: Jerry Hart <harte@BVSD.K12.CO.US>
Subject: Re: Motor Theory For Dummies
Content-Type: text/plain; charset=iso-8859-1
Simoes, Brian wrote:
>
> Volks,
>
> My wife and I are in the process of purchasing an '85 Westy GL and I was hoping
> to gain some basic knowledge on the theory/operation of combustion
> motors...especially as it relates to the motor in my Westy.
>
(snip)
Brian,
Please don't think I am trying to insult your intelligence by telling
you this but I used to teach aircraft systems, including normal and
emergency operational procedures, to fighter pilots. I taught them what
I am going to tell you. When the old fire goes out and your engine stops
turnin' and burnin', you can't just pull your Phantom over to the side
of the cloud, park and pull out the manual. You have to do your
troubleshooting quickly and accurately or you have to jettison the
airplane and spend the next six months filling out paperwork equivalent
to the gross weight of the aircraft.
All internal combustion four cycle engines(gasoline or diesel piston or
turbine) work basically the same way. The four cycles are INTAKE,
COMPRESSION, COMBUSTION and EXHAUST. In layman's terms, all engines
SUCK, SQUEEZE, BANG and BLOW. They intake(suck) air, compress(squeeze)
air, combust(bang) about 15 parts air to 1 part fuel and exhaust(blow)
the hot expanding gases out of the engine. In automotive engines, the
energy is used to drive a set of pistons down and the piston rods and
eccentric crankshaft convert the linear motion into rotary motion. The
heavy flywheel takes care of getting the pistons back up again.
Two things need to be added to the 4 cycles mentioned above to complete
the understanding of how an engine works. A measured amount of fossil
fuel has to be introduced(carbureted or injected) into the compressed
air at the proper time(valve timing or diesel pump timing) and a source
of ignition has to be applied at the right time(ignition timing) to
initiate(diesels and turbines) and often to sustain(pistons) the
combustion of fuel and air.
So, if you understand the following, you will understand the operation
of your vehicle's engine. I fall back on this for troubleshooting
whenever I'm faced with a puzzling engine problem that defies easy
solution.
All 4 cycle engines SUCKŠŠSQUEEZEŠŠBANGŠŠBLOW.
Oops, forgot something.
All 4 cycle engines SUCKŠŠSQUEEZEŠŠŠFUELŠŠFIREŠŠŠBANGŠŠBLOW
All together nowŠŠŠSUCKŠŠSQUEEZEŠŠŠFUELŠŠFIREŠŠŠBANGŠŠBLOW
And, that's all you need to know.
Oh yes. In aircraft anyway, in the absence of visible(oil leak, fire,
etc.) or audible(grinding, banging noises) symptoms, most engine
failures by far are caused by an interruption of fuel flow, followed by
an interruption of air flow. The least likely cause is an interruption
in electrical ignition but I suspect this may not hold true for
automotive piston engines. Things are also complicated somewhat by the
need to maintain engine temperatures within a narrow range(air or liquid
cooling) combined with the cooling properties of engine oil. But, that's
a subject for someone else on another day.
I hope this helps. I have been told I have a tendency to tell someone
who asks for the time how to build a watch. I hope I didn't this time.
Jerry Hart
'84 Wolfie
