Seems like none us cummins guys run it. i haven' t heard it mentioned once since i've been into this.

 

Some guys do. It's rough on head gaskets, you need to make sure the engine is fully warmed up before using it, and don't use too much. The propane lights before the fuel is injected so it's like a running your timing way advanced. Too much causes detonation and broken parts.

 

Dave about nailed it. Propane was popular about five years ago till folks grew tired of the damage it can do.

 

I still see some propane tanks under trucks, but its a dying fad.

Why use propane to gain only 50 Hp? Put in a plate and burn #2. And when guys are getting over 500 hp without it, the cons outway the pros.

 

"The propane lights before the fuel is injected so it's like a running your timing way advanced. Too much causes detonation and broken parts"

What lights the propane before the diesel is injected?

 

Compression. At 400 psi compression pressure the Propane lites around 250 to 300psi I think. So not including the input boost pressure, the propane is already on fire long before the #2 comes into the picture.

It artificially increases your cylinder pressure, but at the sake of using up some of the 02.

 

what blows head gaskets? propane or to much boost? To much fuel of any kind with to much boost will blow head gaskets. I've been running propane for 5 years no problem. Just like anything in life to much of one thing or abuse of something and its bad. follow instructions and propane will work great. People who blow head gaskets have it turned up way to far.

Saying all that would I do it again? NO. Not enough HP for the money it cost to get set up. I spent a 1000.00 on kit for about 60 hp. So I agree with most of what you guys are saying.

 

Seems a lot of folks that had trouble with propane live in the north. Cold temps play havoc with the regulators and valves and you end up with damage.

 

I don't think propane will light until you inject the diesel. Otherwise why do we need spark plugs in gas/propane engines? It's the pressure spike caused after the diesel ignites that causes propane to detonate. The ignition temp. for propane is right around 1000F in air or am I looking at this wrong? Propane also has a octane rating greater than 100.

 

Yes, Propane has an octane number around 115. However in spark ignited engines you have only around 200 Psi compression. You can burn propane (or any other hydrocarbon based gas) in the diesel engine uncontrolled without any spark.

This is the whole reason I need a positive air shutdown. If you hazed propane in front of my air filter the engine would take off without Diesel fuel. Otherwise the only ESD you would need is the same as a gas engine and thats to turn the key..

 

I watched (from a distance) as a diesel JD backhoe engine melted down after hitting a propane pipe. The operator shut it down but it kept on running then so did he. Up to about 15k rpm till boom. The operator should have moved the hoe away from the leak, better yet he shouldn't have hit the pipe.

 

This is because the diesel engine is not air starved and will run away, using the diesel injection "fire" as an ignition system when you supply more fuel be it propane or nat. gas. If you could shut of the injection quick enough I think the engine would quit before it destroyed itself. The gasoline engine will speed up until it runs out of air and gets to rich to ignite, either way not fast enough to come apart.

We experimented years ago running small John Deere diesel engines on nat. gas using the diesel injection as a pilot to start the combustion, they would not run on straight nat. gas. If you could run a gas engine as compression ignition, why doesn't anyone do it? We spend thousands on mags, etc to provide a spark.

 

There are engines in experimentation by companies like VW that are making direct injection gasoline engines that may or maynot use spark ignition.

The problem with getting gasoline or any other hydrocarbon gas to ignite under compression is to control the burn and administer the correct amount of fuel. The mixture also must maintain near Stoich conditions for proper burn and emmissions. You want to have a nice controlled burn to provide an even pressure on the piston. By burning methane or other hydrocarbon gasses by pure compression the mixture has a high peak pressure but the flame goes out quickly and you have only a sharp spike for pressure in the cylinder (ie blown head gaskets) and not a long steady burn. Its just harder to control.

If you have ever driven a 366 Chevy engine in an old grain truck, you know you don't need spark plugs after it gets hot.

You want to have control of the internal combustion before it becomes external combustion.

J-eh

 

Yeah, I've read about the direct injection gasoline engines, they use a spark plug to get lit and then once running they are in a perpetual state of detonation using left over free radicals to ignite the incoming charge. I just don't understand how a fuel with an auto ignition temp of 1000F and an octane rating of over 100 gets lit in an engine that generally has less than a 20:compression ratio. What's the peak temperature in the cylinder created by the compression, probably 500F or so?
What is stoich mean nowdays anyway? Engines that used to run 2% are now running near 10% 02 and 32:1 air fuel ratio.

The old grain truck probably had lots of carbon for pre-ignition and had 80 octane fuel that has an auto ignition temp. of around 500F

Not trying to get under your skin lil,Dog just trying to get educated.

 

Educated??? uh oh...

Hey this is all good. Making me think. All the points are valid DRD and I understand where you come from. Yes Stoich is out the window for most high speed engines as they stretch for emmissions and power.

Try to tell me the new automotive engines are using air/fuel ratios that use more O2 and explain the mileage. New engines are getting worse mileage than the old big blocks.

Basically I would rather inject NOS to cool the intake charge and give a little more 02 for the burn instead of adding another fuel source with charactoristics not similar to Diesel.

I will have to do my homework on the propane compression ignition, got me curious.