CO2 anti-runaway system ideas...

[LesBerg]

So one of the things I'm always doing is trying to solve mechanical/technical problems.

I'm wondering if it would be possible/advisable to build an anti-runaway system for the DD 2 strokers. 

My thought is to use a large CO2 fire extinguisher and plumb it to the intake just before the supercharger or turbo - closest place to the engine where the system is still at normal atmospheric pressure. Rig it on an electric solenoid valve to a safety-covered toggle on the dash so that you could trigger the system from the driver's seat. Feed the engine large amounts of CO2 until it shuts down.

With some testing to make sure the CO2 is dumped in correctly, do you think something like this would work?  Could it damage the engine?

Thoughts?

[Iceni John]

Wouldn't the CO2, or the nozzle through which it is venting, freeze solid if it were being dumped at a high rate?

This may be a more benign way of shutting down an engine compared to physically blocking the intake air, which can sometimes damage the blower seals.   Yes, I like this idea, even with the freeze issue which is not insurmountable.

John

[LesBerg]

I had thought of that. I was thinking to set up an inline expansion chamber and plumb the dump in a 3/4 or 1 inch line to prevent line freeze and allow a high-flow discharge.

[RJ]

Les -

Are you trying to solve a problem that rarely, if ever, occurs anymore?

Most common reason for a runaway in the older 2-strokes was a stuck injector.  99.9% of those old injectors have long since been recycled, with the spring-loaded return models as their replacement.

So now if an injector sticks, it's only that one hole that goes crazy, the others remain in the no-fuel or idle position.  Like a centipede with a wooden leg: 99 - thump, 99 - thump, 99 - thump.

Sure, the engine can run on it's own oil, but that's even rarer than a stuck injector.

Far better to invest the time, money and effort into an engine compartment fire suppression system - which our own RV-Safety Systems guru Jim will be more than happy to help you engineer for your coach!

FWIW & HTH. . .

[papatony]

You already have a shut down system built into the engine that is as good as you can get.

[Len Silva]

I think using a CO2 fire extinguisher when you are working on the governor or rack might be a good idea.  Beats smashing the governor with a sledge hammer which is what I have heard some mechanics do.

I really don't think it's a big concern with a properly running engine in normal service.

[gus]

My thinking is the same as RJ's, you may be looking for a complicated solution to a non-problem.

[neverlearn]

I think it is a good idea.  My intention is to use a Nitrous Oxide setup (charged with CO2).  I don't believe that this approach is overly complicated and it uses standard components.  As others have pointed out, it may never need to be used, however if ever it does I would rather have the option to shut it down than to not.

[JWallin]

Chilling your hot engine rapidly may not be the best approach.

[luvrbus]

There is absolutely no reason for that type system just change the fuel rods if your engine has the old type fuel rods (2 screw adjustment) and replace with the 1 screw spring loaded type


good luck

[Hi yo silver]

Please don't use the term "fuel rods" in the same sentence with "bus". Marilyn already thinks the bus is nuclear...
Couldn't resist,
Dennis

[luvrbus]

Ok rack control rods

[TedsBUSted]

With the volume of intake air being pumped, and especially at runaway speeds, I don't believe that a single CO2 cylinder can boil-off gas fast enough (if the CO2 plumbing doesn't freeze solid from high flow rates) to dilute the engine's intake air enough to bring shutdown. After all, it seems like the orifice in a CO2 valve isn't even 1/4" in diameter.

If  the cylinder delivery rate problems were somehow overcome, still, a single common solenoid valve in a compact size definitely isn't going to handle the required volume.

The mechanic smashing the governor housing? I can't imagine standing next to an engine during runaway,  in the line of potential shrapnel, to do nothing more than hammer on it.

Anyway, choking the intake is more than adequate , but, if I was still interested in developing some sort of redundant way to "kill" the engine, I believe I'd look at  holding the valves open, per compression release.

Ted

[artvonne]

  Ive read and thought of this a while back. You read stories about runaways and it freaks you out. But as stated, they are mostly old stories. This is where we need to cherish the opinion of those more experienced.

  While sucking the seals out of the blower isnt a happy thought, I'm not so sure what a rapid shock of -160F vapor would do to hot pistons and liners. Be a lot easier to replace blown blower seals than cracked liners. And at that point why bother stopping it, just let her blow. Or whack that Governor with a hammer.

  How far back did they start using the newer style injectors and fuel rods?

[LesBerg]

Good to know, all the way around, especially holding the valves open. I mainly brought it up because I tripped over two threads in two days that were about runaway DDs.

I had also thought about adding a second solenoid line that could be tripped for an engine bay fire. My dad (retired navy) suggested using Halon for the system, but I think it's just plain dangerous. Also, if one were to plumb the system with CO2, you could fill or exchange the cylinder at nearly any Ox-Arc, Norco, or other compressed-gas outlet, where a halon system would have to be serviced by a fire system company.

I realize it's a rare problem, but it's just how my head works - I see a problem and I have to see if I can find a way do something about it.

I also saw that most DDs are equipped with a 'kill switch' that closes an air door, but I also thought I'd read that some people were removing them as the issue was so rare. Did I read that wrong? My M113 in the army was equipped with one, but I never needed to use it.

My thought with this was towards safety. If the air-door cutoff system is still in use, we can just let this die.