Sorry to hijack, your motivation is fuel economy?
Jim
Not my thread anyhow, so hijack away
The fuel economy aspect is what got me looking into to propane system in the first place, but the extended range, power, and maybe cleaning up some of the block smoke were also a factor in going with the Digital system and larger tank, not to mention I found some heavely discounted prices on all the parts. The MSD/Superchips DPI system, BD 15-Gallon tank, and ARP head studs are going to cost me less than $1,700.
I guess I could have spent simular money an a larger / aux fuel tank to extend my driving range. For power I could have got injectors and / or a new turbo to boost the power, but I would still need to stud the head with those mods, and I think the propane system is the only one of these mods that might reduce my fuel cost per mile so it may pay for itself in 50,000 - 100,000 miles? Since I searched all over the web tring to get some facts on any mialage increase with propane and came up empty, I guess it is up to me to document the results.
Here is what I hope to accomplish:
Reduce my fuel cost from about $0. 20 /mile to $0. 17 /mile. This would pay off the system in less than 57,000 miles, but even at $0. 18 / mile, the break point is 85,000 miles.
Combined with my other bolt on modifications, I would like to get 500 rear wheel HP while still using the stock injectors and turbo (really going to have to watch the EGT's. )
I would like to extend my driving range by at least 150 miles per tank of Diesel.
Currently my "Average" fuel mialage is about 17. 5 MPG and @ 3. 50/gal thats $0. 20/mile and a driving range of 35gallons X 17. 5 = 612. 5 miles.
Would like to get a increase of 6 mpg or Average of 23. 5 MPG.
This would extend my range to 822. 5 miles.
my "Diesel" fuel cost would be $0. 1489 / mile, so I hope the propane cost / mile is only $0. 02-$0. 03? to get any "real saving".
With these numbers, if the propane cost per mile is over $0. 05, then there is no real fuel cost savings.
Since I could not find any real numbers on this, it's really just a guess?
I have heard claims of even higher MPG, but no mention of how much propane was used. Also the cost of Diesel and propane can vary quite a bit, but usually propane has been at least $1. 00 cheaper per gallon than Diesel (unless you buy the pre-filled grill tanks where you get gouged on the cost. )