Motor Operation Detection?

Tach?

Microphone or vibration sensor.

If your "automobile-size engine" comes with an automobile-style electronic engine controller, it may well have a (serial, digital) OBD- II output, which will tell you more than you ever wanted to know about the operation of the engine. Not particularly hard to interface with.

Temperature is going to be a pretty laggy indicator, I'd run a tach of some sort off a shaft, or use an inductive pickup off a spark plug wire or fuel injector.

There used to be an after market tachometer that plugged into a lighter socket. It filtered the engine firing noise off the automobile 12 volt buss for input.

w..

eeboarder wrote:

oil press sw

If you mean to detect shaft rotation that would probably be best. But, I would put one on each end of the shaft.

Oil pressure - will be somewhat laggy, but nowhere near as bad as Temperature.

Alternator output - be sure to isolate from battery

If it uses spark plugs - monitor spark. No spark, no run.

Plus all the others mentioned

Do fuel injected engines generate enough vacuum? I kind assumed that most "automobile-size engine"s would be, these days.

I remember vacuum powered windshield wipers. Had to take your foot off the gas for them to work really well. :-)

On a 52 Husdon, if you really want to know. :-)

Usually the two ends of the crankshaft ought to rotate together, except for very brief and rather disastrous scenarios.

Or vacuum, assuming it's a naturally aspirated engine.

Best regards, Spehro Pefhany

No ECM at all. It may be naturally aspirated or turbo charged. It's for a compressor station, but it's essentially a car engine.

... snip ...

Fuel requires oxygen to burn. Where do you think the engine gets that? If it is not 'naturally aspirated' something has raised the atmospheric pressure at the intakes.

Fuel injected engines don't have carbs. AFAIK, most of the vacuum came from the venturi in the carb (used to suck the gas into the air stream). For a fuel injected engine, I can see no reason to have an unneeded restriction to the intake airflow just to have a vacuum source.

Oil pressure sounds like a logical way to go. There's probably an ignition shut-off that kills the engine if oil pressure drops-- even inexpensive portable generators have those.

Best regards, Spehro Pefhany

The torque of an internal-combustion engine is controlled by a throttle valve in the intake manifold. When the mixture is correct for the burning in the cylinders, the effective pressure in the cylinders is proportional to the absolute pressure in the intake manifold. This applies regardless whether the fuel is added in a carb or injected into the manifold or injected into the cylinders (as in diesels).

An absolute pressure less than the surrounding air pressure is commonly called suction. In a non-turbocharged engine the absolute pressure in the intake manifold is always less than the air pressure outside, due to the flow resistances in the piping, filters and throttle.

The gas flow around the throttle valve creates a feedback effect between the rotation speed of the engine and the manifold pressure. This may create an impression that the speed of the engine is controlled by the throttle.

In message , Spehro Pefhany writes

Turbo or NA, I would suspect you're going to get a pressure difference between atmosphere and manifold so a differential sensor may be useful. Of course, it might not work on a diesel. For a petrol/gas engine I'd be looking for an ignition pulse or alternator noise and for a diesel I'd be looking for alternator noise alone.