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 |
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