It seems hard to believe that it would net a zero improvement at lower power levels because vapor (propane) is smaller than droplets (diesel) and the faster flame front of propane would lead to a more complete burn (assuming there is enough oxygen). At higher power levels I can see your point that there would be less air available to do a complete burn. But I do not have a good grasp on dueling flame fronts.

Disclaimer:I am not an engineer.

 

The "catalyst" effect doesn't actually happen. Its just a common scam marketing technique.

 

The lack of improvement is very simple to explain:

Propane is still a fuel and fuel alone is useless.
Please have in mind that diesel needs to run at least at a 20:1 mixture of air to run smokeless. That means during low and mid power you only have a small amount of air supply available because your turbo does not deliver excess air. That will appear with full boost.
As a reason of that most propane systems are activated with a boost pressure switch to ensure the adequate supply of enough air to burn the diesel+the added propane.
Injection is very similar to the Diesel nitrous systems. But in this case nitrous is much safer than propane systems. Adding nitrous in a diesel does not lead to detonation, It is able only to kill the flame in the diesel chamber if adding to much nitrous. you can see some smoking trucks at the quarter mile, they stop smoking as soon as nitrous is injected.
Some commercial systems go a step further, they add propane only under specific load conditions to ensure safe running conditions. The problem with propane is known, but kept silent.

 

Hmm.... Interesting!

So, does adding nitrous to a diesel work the same as it does in a gasser? (In a gasser, basically nitrous adds a lot of 'available' oxygen inside the combustion chamber. This is accompanied by the addition of a lot more fuel! Together, this extra fuel and oxygen creates a serious increase in power!!)
I always thought that adding nitrous to a diesel allowed the 'extra' fuel being dumped in there by large injectors to have some more air to burn and make more power. It is basically like increasing turbo boost, isn't it? (Of course, to be able to use it you have to already have larger injectors spraying more fuel in there!)

So what else is there to know about propane? Or should I say: Let's here it all!!
Dan

 

Off topic: Adding nitrous in a diesel is way better than in gasser. There will be no risk of detonation!
No, it's is way better better than increasing turbo boost! It does also decrease intake temperatures like an extra intercooler, it also decreases as a result of that EGT's.
It does increase simply allow the engine to burn more fuel more safely.

Just have in mind that nitrous injetors have be 30% bigger to the 30% more air demand of diesel engines compared with a gasser.
Off topic off!

As far as I know do MSD and Bully dog offer commercial propane systems for Diesels.
Due to the need of a lot of combustion air I would install always a full throttle switch and and a boost pressure switch in combination with an electromagnetic valve to prevent the activation of propane during low boost. Do not forget it is still a high flammable gas!

 

There are a few commercially available propane systems out there. I think most of them are set up to not come on until at least 5 psi of boost is made.

I am only interested in propane for increasing mileage as I don't care about having more power (or need it!).

Oh, and as far as low boost is concerned: I heard it explained like this. Basically you have a normally aspirated engine before the turbo spools and starts making boost. I think that sums it up quite nicely!!

 

Here are some interesting facts to me at least- propane works very well in small doses to increase mileage. I make a variable flow VACUUM referenced, propane kit that I use mainly for mileage improvement. My Mega went from 18-19 mpg's to 25.2 on the interstate running propane running light. Hand calculated so extremely accurate and was there for 3 tank fulls traveling to Illinois. The power brings a smile to my face - even wife notices difference when we are out of propane. Noticeably better throttle response, less smoke, and more fun to drive. I use the kit to turn on after the truck is over 170 degrees water temp. and all is well. My 20 lb test propane bottles last 600 - 800 miles and I have my propane set so that it comes on at 1 lb of boost! I wanted it to help when cruising too, not just on hills. Diesel ignites at 437 degrees F. Propane does not ignite until 1004 degrees F. What propane does is causes turbulence in the cylinder to help spread the approaching diesel flame front more throughout the cylinder AND since propane is a fuel too it gets used to propell the vehicle. So the diesel ignites the propane - which resists detonation in the cylinder as its octane is 112 - and once the diesel is introduced and burns, starting at 437 deg F, and ending at 3729 dgrees F, it ignites the propane at 1004 degrees F. Propane is one of the most cost effective mileage and power increasers, my 20 lb bottles cost 65 cents per pound to fill, I get minimum of 600 miles per bottle, which is 3 cents per mile for the propane. The diesel on the other hand is $3.09 per gallon and at my best mileage of 25.2 miles per gallon is 12.26 cents per mile. So in effect - use the propane - it is a cheaper fuel, adds sig power (80 to 100 horses) , pollutes less per mile, cause your using less diesel to do the same work, supposedly reduces oil contamination, (I can't verify that mine is always black and have never had it tested), and it is cool to tell others you use propane. It is an easy install too. Everyone that has seen my kit wants one but i'm too busy right now working on my house to make some up but will soon. PS I will use a power speed calculator and tell you my rear wheel horsepower increase Soon!

 

Thats false economy due to fuel substitution. Actual economy (as in BTU's consumed) didn't change.


842*f.

Propane autoignites long before that, especially at boost.
Diesel's autoignition temperature of 494°F means the air must be at least that hot just for the engine to start. Since Cummins can start well below freezing without an external heat source, that means at warm ambient temperatures the air is well above 494°F, far higher with boost.

 

 

Here is the chart I got the temperatures from: Propane Facts & Comparison Charts The purpose of the temps listing was to show that Diesel ignites before the propane ignites, even though the propane is already in the chamber. Of course propane is a fuel, and of course no matter which fuel you use- it takes the same btu's (work) to do the same job. By replacing more expensive diesel fuel with cleaner burning propane AND more power - and still costing less overall than diesel to travel per mile - win-win. The propane also since it causes turbulence in the cylinder allows the diesel that is then injected to burn more completely, especially since the propane burns slower and longer time than diesel - so that the efficiency ratio goes up. Same distance travelled - same btu's required - but more power when needed and lower cost. Forced I enjoy your thread answers - but have you ever used propane? It works great for mileage.