CNG diesel

[E7mack96]

Just heard for the cummins rep that there will be a CNG cummins 6.7 engine coming out. Anyone know more..

We are testing a Cummins Westport CNG 12 liter at work. A few of our competitors are running them. Cost of CNG is $2.30 per equivalent gallon of gas which is the same as $2.53 per diesel equivalent (all based on BTU)

Would anyone consider running a CNG 6.7 in a personal vehicle?? I have a station opening near me at home and have a station near my work. There seems to be alot of interest in this fuel these days.

 

[Wingate]

Have seen several Peterbuilt dumptrucks filling up at the local CNG stations...
That being said, is the Cummins a Dual-Fuel aka Bi-Fuel engine? is it a true CNG only engine or a diesel with bi-fuel capability?
It shouldnt be too much of a stretch for Cummins as they currently have a 5./9L/6.7L Natural gas Stationary engine platform to work from. At Caterpillar, the big push has been on large displacement stationary engines to be converted to DGB Technology that allows diesel engines to run a mixture of diesel fuel and CNG/Wellhead/Propane gas to lower diesel consumption.

 

[rscurtis]

You couldn't give me a CNG truck unless the fuel was free, and even then I'd still have to think about it.

 

[Bob4x4]

Ram already offers a gas /cng pick up

 

[Wayne M.]

Ram already offers a gas /cng pick up

Yup, I just went to training on a GMC Savanna CNG van we're getting a bunch of. Seems that CNG is picking up popularity again. Difference is this time I think the technology is good enough. The previous vehicles- especially the conversions were disasters!

The title is CNG diesel. Really that's not possible. CNG is a spark ignited fuel. The Cummins and westport CNG engines are indeed diesel engines we already know that are converted. Compression ratio changed, spark plugs in place of the diesel injectors, CNG injectors installed where you'd find them on a gasoline engine, and a throttle- among other things. When it runs, it's dramatic like comparing a 1999 24 valve to a 2004 24 valve- they sound weird- quiet weird. Some CNG engines are modified gasoline engines. The one in the GMC van is a special RPO 6.0.

 

[E7mack96]

I do mean a straight CNG engine.. I posted with the title of CNG diesel cause thats the sub-forum.. So far, on our test engine, running 24/7, it is running pretty good. Drivers are not complaining. One down side was the original 7,500 mile oil change interval - well they got it up to 18,000 miles.. We would have had to change oil every week.

 

[Wayne M.]

I do mean a straight CNG engine.. I posted with the title of CNG diesel cause thats the sub-forum.. So far, on our test engine, running 24/7, it is running pretty good. Drivers are not complaining. One down side was the original 7,500 mile oil change interval - well they got it up to 18,000 miles.. We would have had to change oil every week.

What the application? tank capacity? Range?

 

[rscurtis]

The title is CNG diesel. Really that's not possible. CNG is a spark ignited fuel.

You may want to revisit that statement. CNG ignites very easily with diesel fuel. Warren Buffet is experimenting with LNG as a locomotive fuel, and that is how ignition is accomplished. The engine idles and runs at low power on diesel fuel, and LNG is added with the intake air as more power is required. This is really the optimum way to run CNG. It eliminates the need for a spark ignition system and the need for a warm-up fuel as is required in the CNG RAM. It also solves the problem of range anxiety, as you still have a fuel supply once the CNG is used up- which happens relatively quickly compared to other fuels.


Having said this, you still couldn't give me one. It is pointed out that CNG on a per-gallon equivalent is cheaper than diesel, but that differences diminishes when you consider the difference in BSFC. Eventually, the free market will also erase that difference. I'm not even addressing the $11k+ option cost, either. The only way a municipality can justify the CNG option is because someone else is paying for it- namely you and I. There isn't even an emissions benefit anymore either- diesel is just as clean- and it can be parked or worked on in an enclosed building without the explosion hazard.

 

[E7mack96]

In our application, the upfit cost is an addn'l $50,000 or so. Even with our tax rebate of 25K it is still a hefty penny. WE are trying out one with a 90 gallon equivalent tank. the drivers are fueling up 4x a day (we run lots of miles) The range is about 330 miles or so. we haul at 80,000 gross. since the 7th, we already put 7900 miles on it.

 

[Road Dog]

Yup, I just went to training on a GMC Savanna CNG van we're getting a bunch of. Seems that CNG is picking up popularity again. Difference is this time I think the technology is good enough. The previous vehicles- especially the conversions were disasters!

Disaster? A friend of mine converted his gas pickup in the early 80s. The government was doing a big push so there were good rebates and several fuel stations around. The only down side was the space the tanks took in the bed. Much cheaper to run around town during the week and you could switch back to gas for camping and hunting on the weekends. I think the payback was under a year.

 

[rscurtis]

The government was doing a big push…..

The payback was fast because someone else paid for it.

 

[RustyJC]

Dual fuel engines have been around for over 60 years in stationary power generation and other services. These engines start (and can run) as straight diesels and switch under load to dual fuel mode where they typically run 96% natural gas/4% diesel (injected to ignite the air/natural gas mixture). The advantage to the users (e.g., municipal power plants) is that they can run the engines on whichever fuel is less expensive ($/MMBTU) and/or available at any given time. A dual fuel engine has air/fuel ratio controls that are disabled during pure diesel operation (they run maximum air under those conditions) and enabled during dual fuel operation to control the air/natural gas mixture.

Typically, these engines can also be operated in spark gas mode by removing the diesel injectors and installing adapters with spark plugs. Obviously, an ignition timing system is required as well.

An example is the Cooper-Bessemer LSVB-20-GDT where the GDT stands for "gas diesel turbocharged".

Rusty

 

[Wingate]

Wow, COOPER! Really you had to go there?? hahahaha.. Might as well throw in an old Climax Engine Co. or a White-Superior since were digging out pig-iron slow speeds.

 

[RustyJC]

I guess I don't understand your comment. I pointed out that dual fuel (gas diesel) technology has been around for a long time and cited an example. FYI, Cooper-Bessemers are still manufactured for a number of customers who will pay more in initial price and cost of installation to get better fuel consumption, efficiencies and lower maintenance costs over the life of a long term project than they can obtain with high speed separable units. Cooper-Bessemer, Superior, Ajax, etc. are now products of the GE Oil & Gas Reciprocating Compression group.

Rusty

 

[Wingate]

haha.. coopers that are still in one pile around here are OLD.. i mean OLD! Most have fallen victim to the scrap torch and replaced with high speeds.

 

[RustyJC]

Well, I still don't understand your point. Cooper has been in business since 1833, so I guess it stands to reason that there would be some old Coopers in service (and, yes, being retired), but new ones with state-of-the-art technologies are still being built and sold. High speeds are cheap to buy and install, but they use more fuel, are more expensive to maintain and (in compressor service) are not as efficient as modern integral engine/compressors.

So, what does this have to do with the subject of this thread? I pointed out that Cooper, among others, has been building dual fuel engines since the 1950s, so I'm supposed to be impressed that Cummins finally figured out how to do it? Dual fuel engines are established technology.

Rusty

 

[E7mack96]

Well an update on our CNG truck is that we have put 13,566 miles on it so far this month. WE are running it hard. Drivers seem to like it.

 

[Wingate]

good deal..
I hope that CNG gets a hue market share in the near future. It will help our economy.