I did a CNG/diesel injection system on a 1998 Land Rover Discovery that has a 300tdi diesel engine in it that I did the conversion on. this video shows the complete conversion process and explains the various components. I don't know the overall outcome of fuel economy yet. I just installed it. when I get the numbers I will do a follow up post. Hope someone will enjoy this.

Thanks.

 

Nice work! Way too long a video though. :P

 

thanks. yes it is long. just trying to be complete.

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I have done two CNG conversions and have found some interesting numbers on economy.
One was a 2006 Volvo AWD S60 2.5 turbo intercooled engine. It gets 24 mpg so it uses 625 gallons of fuel for 15k miles. It cost $2250 for gas @ $3.60 gallon and $950 for CNG @ 1.52 a gallon. So cost per mile was $.15 for gas and $.063 for CNG. It was a fumigated system with a Red Gas regulator. I noticed a large power loss on the mountainous pass I drive to work and back on but on level ground no noticeable power loss. Fuel economy was the same whether I was on CNG or gas. I was extremely happy with it.
The other is a 1998 Land Rover Discovery. It originally had a 4.0 v8 gas engine. I was getting 10mpg. Due to the engine head gasket problems I decided to install a 300tdi rover 2.5 turbo diesel intercooled engine and manual transmission. My mpg went to 22.3 mpg. But was seriously underpowered for the mountains I drive in. I tweaked the injection pump and it helped some. I decided to do CNG fumigated injection. It does not have o2 feedback nor a modulated stepper fuel nozzle. The Discovery is seriously underpowered at 117 hp. The CNG makes a huge difference in power. My EGT for the same speed/gear has dropped 100-200 degrees Fahrenheit due to the increased hp. So the fuel/price numbers are:
Gas 10mpg @ $3.60 per gallon costs $.36 per mile.
Diesel 22.3 mpg @ $3.75 per gallon costs $.168 per mile.
CNG diesel 66% diesel 33% cng mix mpg dropped to 19.2 total mpg fuel costs $.148 per mile. (32mpg diesel)
CNG diesel 32% diesel 68% cng mix mpg dropped to 16.2 total mpg but fuel costs remained at $.148 per mile. . (40.3mpg diesel)
So what I assume happens as I increased the amount of CNG per diesel the fuel economy went down due to the lower btu content of CNG vs. diesel. CNG btu is 114000 vs diesel 129500 btu, 12% less. So the price per mile doesn’t change but power really does. I did not run a lot of miles (706) on the 33-68% mix as I just increased the amount of CNG mix in it so I’m not totally sure of the accuracy of those numbers. I could be like a lot of people I hear about cng diesel mix and just say the diesel fuel economy went to 32 mpg and 40.3 mpg but you need to include the cost of CNG. The power is absolutely worth it!! And it burns much cleaner!
My driving consists of 85% highway driving but I have a serious mountain pass I drive every day. Its 10 miles long but goes up 2600ft in elevation. I live around 7000ft in elevation and work at 4600ft elevation. I’m. (32mpg diesel) interested in any constructive input. Thanks.

 

nice