Runaway diesel

[Leeward Rail]

That video is more like a 300 or 400 horsepower engine and intentionally held to high rev's

Try 2,900 horsepower. Watch the digital display on the side of the Dyno.

It's being run on a Dyno to see how much power it produces. It's a competition.
These engines are pushing the extreme boundaries and are prone to failure for that exact reason.

Not a runaway. There is a guy in the truck with his foot on the throttle.

That YouTube channel is run by a company that builds strong transmissions.
They hold competitions on trailer mounted Dyno, with spectators at a safe distance due to the risk.

The owner is famous for the truck "Red Delicious" which hit 3,000 hp. It also eventually blew up on a subsequent test.

Small marine diesels, with hardly any power, obviously have almost nothing in common with these trucks and don't blow up like that even if they failed.

I do know exactly what you were thinking about going into an engine room emergency,

Keep a Co2 extinguisher at hand. If governor failure runaway or other - Co2 kills the motor instantly - every time.

Exactly. IMO Just another reason why a co2 or similar extinguisher is mandatory on a boat.

Our boat has a panel in the companionway stairs that can be opened to allow a fire extinguisher nozzle.

When talking to a local fire protection company about an automatic+manual fire system for the engine bay, they suggested a "cleanguard" system that uses HFC-236fa. Doesn't make a mess, doesn't damage electronics, and will displace oxygen. Apparently work as well as co2 on shutting down a diesel.

Just yank the release cable/pin and Robert's yer uncle.

 

[twodzusfittings]

Is this thread still attracting traffic.........

Google Image Result for https://i.ytimg.com/vi/YWTJ8iZr7ro/hqdefault.jpg

 

[Davidasailor26]

It remains that I can watch my engine start while the starter cranks it, and no way it achieves 200rpm before starting. It usually achieves less than 1 rpm before it starts. I'm sure it achieves the equivalent of 200rpm during the 4" the piston needs to move to get compression/ignition.

200 RPM is not a measure of how many revolutions the engine has turned in the last minute. It is a measure of the instantaneous rotational speed of the engine. If the engine “achieves the equivalent of 200 rpm” then at that point in time it was moving at 200 RPM. A tachometer won’t tell you that because it shows an average sampling of RPM over some period of time, as a result of how it measures speed, but that doesn’t mean the engine didn’t move at 200 RPM at some point.

In order to start combustion the fuel needs to be mixed with air at high compression and temperature. What the graph above shows is that compression increases as rotational speed increases. This is because the faster the piston reaches the top of the cylinder the less time there is for compression to be lost past the rings or seals. The amount of compression needed to ignite the fuel will also depend on temperature, which increases with compression and with increased ambient engine and fuel temperature. As an engine ages and the rings wear compression is lost more quickly, so the engine will need to move faster to achieve the same compression amount as a new engine moving slower. But none of this means the engine must sustain that speed for an extended time (more than one piston stroke), though more strokes may build up more temperature in the cylinder and allow the fuel to combust at a lower compression.

 

[colemj]

200 RPM is not a measure of how many revolutions the engine has turned in the last minute. It is a measure of the instantaneous rotational speed of the engine. If the engine “achieves the equivalent of 200 rpm” then at that point in time it was moving at 200 RPM.

Totally agree, and I have been saying that all along - the piston must only achieve the equivalent of 200rpm speed over 4". This could be accomplished by just a short pull on a handle, and the reason why a weak battery can't start the engine is that it cannot push through the compression stroke at this speed (or at all).

Mark

 

[Hayden Watson]

Totally agree, and I have been saying that all along - the piston must only achieve the equivalent of 200rpm speed over 4". This could be accomplished by just a short pull on a handle, and the reason why a weak battery can't start the engine is that it cannot push through the compression stroke at this speed (or at all).

Mark

This is why my old diesel Massy Ferguson tractor was able to start at -20º when nothing else on the ranch would. You did not crank it. You turned the engine until it was at the very beginning of a compression stroke and then gave one hard yank on the handle which quickly ran that one piston up over the top, compressing that cylinder and getting that one to fire. Once on cylinder popped, that provided the needed speed for all of the others to follow along.

 

[Leeward Rail]

You turned the engine until it was at the very beginning of a compression stroke and then gave one hard yank on the handle which quickly ran that one piston up over the top, compressing that cylinder and getting that one to fire.

I was always taught that was standard procedure with hand crank engines.

 

[dLj]

I was always taught that was standard procedure with hand crank engines.

All the farm equipment I've worked with that's the case.

With all the marine diesel engines I've worked with, they had large fly wheels and you had to get them spinning fast enough to then drop the decompression lever to get them started. No idea why the difference...

dj

 

[dlochner]

No idea why the difference...

Farm boys are bigger and stronger than old sailors.

 

[dLj]

Farm boys are bigger and stronger than old sailors.

Ha, that's it!

dj

 

[MikeHoncho]

you guys ever see the 12 gauge blank fired starting diesel tractors? gives it compression and heat.