Fuel Economy

[ronnyM]

If Propane injection helps fuel consumption as much as I hear it does

why is it in wider use?



What percent propane to diesel is used for best fuel economy?

 

[WoodChuck]

It only takes X amount of horsepower to accomplish any given task in a given amount of time. It seems to me the propane is mainly adding additional fuel which would require less throttle pedal and account for less diesel used.

With the expense of adding a propane tank and plumbing and then the cost of the propane do you really come out ahead?

 

[AMcCormick]

From what I understand the propane acts as a cataylst for the diesel that is in the injector. I dont know the exact numbers, not all the fuel is burned that goes through the injector the propane help burn more of that fuel. Thats just what I've found through reading. This or water injection is something that may be on my list in the future?

 

[DPellegrin]

The thermal efficiency advantages of a diesel cycle engine (heterogeneous charge) versus a Otto cycle engine (homogeneous charge) are well documented. A diesel engine derives much of it's efficiency advantages because it runs so lean. 90-1 air-fuel ratio (A/F) at idle and 20-1 A/F at full load. These are A/Fs that an Otto cycle engine is to lean to run at.



Because a diesel engine combustion is lean, the combustion event is notoriously slow. When propane vapor is introduced to the inlet air of a diesel engine the combustion process is enhanced by the formation of free radicals that get the combustion process started before the diesel fuel injection event that not only takes a long time, but the diesel fuel must vaporize (become a gas) before combustion can occur. This is called the ignition delay period, which is much shorter with the introduction of propane vapor in the inlet air.



The bottom line is propane improves diesel combustion efficiency by making the engine operate more like the constant volume combustion of a Otto cycle engine.



Testing has shown propane has its best advantage the higher the engine's load factor. The total number of BTUs consumed by the engine, both diesel and propane, is lower when propane vapor is introduced into the inlet of a diesel engine. Thus the brake thermal efficiency (specific fuel consumption) of the diesel/propane engine is lower than equivalent power diesel engine.

 

[hERKY130]

I've read through Diesel Power Magazine that the liquid propane is further vaporized by routing coolant through a regulator in order to heat it.



Barring the total cost of the propane system installation, is it more economical using propane vs. no propane? Has anyone done a cost analysis over equal distance runs using a given volume of propane and like amounts of diesel? Whats the measureable gain in MPG?



The article in, I believe, December 07 edition of DieselPower Mag had some good info on the installation of such a system, but its on a powerstroke truck. Does anyone have installation pics, pricing spreadsheet and labor estimates for DIY install on cummins? The article had no qualitative info on actual HP gain, just that "it was a definitely noticeable boost in power". They estimate a 60-80hp gain. Unknown if at the rear wheels.

 

[Houser]

Why don't one of you guys get brave and try a hydrogen boost kit
They cost about $600, Run on distilled water, and supposedly ad up to 25% 0r more MPG. You can even make one your self for under $100.
Then tell me how it worked so I can get one.

Mike
Palmer, Ak.

 

[betterthanstock]

Anyone messing with propane, or hydrogen, just keep in mind that diesels have a very high compression ratio. You want to add less than the minimum ignitable mixture. That is, keep it so lean that it cannot ignite before the piston hits TDC, or you will get knock/damage. You only want it to ignite after the diesel is injected. .

 

[Bob4x4]

I've read through Diesel Power Magazine that the liquid propane is further vaporized by routing coolant through a regulator in order to heat it.

.

If you don't heat the regulator it will freeze up. There is also a maintenance cost involved. Unless the propane sold today is much better than 10 years ago the regulators will gum up and quit functioning. The propane in Mexico was even worse and would foul the regulator and filter/lock offs much sooner.

One advantage the diesels have had in the past was it's simplicity. Why try to add more complexity?

The price of propane is not much different from Diesel here in Cali and will require one more fuel stop. No thank you for my trucks.



Bob