44 mpg propane injection!! ??

[Cooker]

When discussing things of this nature I would not discredit Rustys expertise. His knowledge is much more valuable in this discussion than that learned from installing and building CNC machinery.



I think there may be a misunderstanding here. I don't think Rusty is saying that an increase in mileage is impossible (If I am reading this right) I think the point is that if you were to figure in the total cost per mile of the propane and diesel combination vs. total cost per mile of diesel only that these number would very close and that a increase in overall efficiency was not obtained (because it cost the same to do the same work).



I apologize if I am interrupting this incorrectly.

 

[RustyJC]

Mark,



Let's not let a technical discussion degenerate into personal insults. I haven't called anyone anything, have I? All I've said is that the definition of thermal efficiency is work out divided by energy in. That's not up for debate. If your friend is claiming to get the same work output with less total energy input, then by definition the thermal efficiency of the engine must be higher.



As I said, the only way to understand what he's truly seeing is to measure total BTU going into the engine from both the diesel fuel and propane, not just the gallons of diesel fuel consumed. My point about "what my company does" is that we, like Cummins, are an engine manufacturer, albeit in different markets. If we (or Cummins) could build a diesel engine that was 50% more efficient by giving it a shot of propane, don't you think we would do it (even in the years before emission controls)? If Cummins could have done this, they would have owned the Class 8 market. So, where are all the Class 8 trucks with diesel and propane tanks?



Rusty

 

[HoleshotHolset]

So, where are all the Class 8 trucks with diesel and propane tanks?

Thermodynamics discussions aside... I got your Class-8 truck with diesel/propane tanks RIGHT HERE!



Matt

 

[Mark_Kendrick]

When discussing things of this nature I would not discredit Rustys expertise. His knowledge is much more valuable in this discussion than that learned from installing and building CNC machinery.



I think there may be a misunderstanding here. I don't think Rusty is saying that an increase in mileage is impossible (If I am reading this right) I think the point is that if you were to figure in the total cost per mile of the propane and diesel combination vs. total cost per mile of diesel only that these number would very close and that a increase in overall efficiency was not obtained (because it cost the same to do the same work).



I apologize if I am interrupting this incorrectly.

the costs of a commercial system usually make a return on invesment that is lack-luster and a long time coming. But when diesel is $2. 50/gal and propane can be had under $2/gal, you do get significant savings on fuel if you even get modest improvements on efficiency.



Back when diesel was $1-1. 50 and propane was $1. 60 it was hard to justify paying for propane injection parts.



If you could build it from spare parts at near $0 cost and you are using extended intervals on oil and putting on tons of miles the savings become substantial in a hurry.

 

[BManier]

Hey Rusty I do have a couple of things to say about your posts. For one your equations are vary true. However I do not belive that is a complete representation of what is happening in the chamber during the burn. Propane is cheaper right now so when you do the burn efficiency increase by the catalyst you do get a slight cost reduction. And as for your R&D I am inclined to think that your dual fuel engines are LP not propane. And as much as we can test in a lab adjustment on the road is more effective. Some other good reasons for propane are less smoke that can get you a ticket, and in general cleaner burn. So while I do not belive at all the 50% increase I very much would belive from 5 to 20%.

 

[Cooker]

the costs of a commercial system usually make a return on invesment that is lack-luster and a long time coming. But when diesel is $2. 50/gal and propane can be had under $2/gal, you do get significant savings on fuel if you even get modest improvements on efficiency.



Back when diesel was $1-1. 50 and propane was $1. 60 it was hard to justify paying for propane injection parts.



If you could build it from spare parts at near $0 cost and you are using extended intervals on oil and putting on tons of miles the savings become substantial in a hurry.

Mark,



Thanks for the reply. I tend to agree with your comments. I do not question the increase in MPG's but the lack of any substantial savings by running dual fuel. Using the information provided lets do some quick cost analysis to see how it works out.



If consumption of propane is 10-20% of the diesel fuel consumed , we'll use 15% and MPG is 22-26MPG on diesel only so we'll use 24 MPGs, and nearly 30 on the diesel/propane combo so lets use 29. 5.



For cost we will assume $2. 50 for diesel and $2. 00 for propane.



Cost per mile on diesel fuel only is 10. 42 cents.

Cost per mile on the dual fuel is 9. 5 cents.



A savings of less than 1 cent per mile or about an 8. 5% savings.



Put another way a 23% increase in fuel economy only come with an 8. 5% cost savings or about $880 in 100k miles.



I wonder if there is any additional maintenance or operating cost that offsets the savings?



Agreed that factoring in the cost of a propane injections system it would take a long time to pay off the investment. For someone that has next to nothing in a system and drives a ton of miles it may be worth it.



IMHO the only advantage I see to propane injection, assuming the numbers above are what is realistic of what could be expected, would be the ability to extended the distance between refueling.

 

[RailroadJim]

The kit cost in Summit was 795 with a red slash through it, so who knows, plus the inefficiency of stopping twice for fuel(1-dis, 2-prop. ) don't know too many places that have both. My thoughts were if both fuels were about the same price but diesel continuing up, it's worth looking at for 44 mpg total and a little kick in the pants.

 

[Cooker]

The MSD kit at Summit is $711. 88

 

[Mhannink]

the inefficiency of stopping twice for fuel(1-dis, 2-prop. ) don't know too many places that have both.

i don't know your area but around here almost every gas station has both diesel and propane so at least in my area this idea would work.





im also lucky that the 2 places where i work have big propane tanks and wouldn't care if i where to fill up now and again.



one question that may affect all this is how often would you need to fill the propane vs diesel. i mean if you can get a couple diesel tanks fulls out of one propane tank that would make a huge difference too.

 

[TGibbs]

one question that may affect all this is how often would you need to fill the propane vs diesel. i mean if you can get a couple diesel tanks fulls out of one propane tank that would make a huge difference too.

That would depend on the size of the bottle that you installed. You could put a big one in the bed that goes all the way across and get a whole lot more range out of it. But then it isnt easy to pull out and you are driving around with more weight.



Tristan

 

[mattfultz]

Hi guys, I was wondering how long you can keep the boost on these cummins before you start damaging the engine from too much boost! Does it significantly decrease the longevity of the engine to do so? I noticed some guys have 500,000 miles or better on their rigs and they are operating this high of boost plus the fuel screws turned up. How high can you really go?
Matt