compressed natural gas for fuel

don luster · Post by **don luster** » October 9, 2008, 7:43 pm

Is there anyone in states that use natural gas compressed to run vehicles on that could refur me to some web sites that would give out technoligy over the enternet. about how the system works when the throttle open. Is this increased by a regulator? How is it contained in the intake etc? My machines friend and brother-in-law is interested in maybe try to modify or develope this and I would like to play with it with my truck engine etc. Thanks for any and all help. I know there are some pay for informations sites but want the free stuff that will answer a lot of questions we have now.

Johnny Canuck · Post by **Johnny Canuck** » October 9, 2008, 8:29 pm

Don I don't claim to be an expert, because I know CNG is at higher pressure than liquid propane, but the differences are not large, re: regulator etc. Your best bet on this forum is Alan the Aussie, who runs his nasty Slick on Prope.

Hoofbeat Racer · Post by **Hoofbeat Racer** » October 9, 2008, 9:14 pm

Quick reply here Don, I work in the natural gas business where we produce the stuff and burn it as a fuel gas in large stationary 2500 hp engines to run our compressors. Back in school we also played around with it a bit in mobile equipment. Here is the quick and dirty. Natural gas, which is comprised mostly of CH4 or methane is an excellent fuel gas as well as a clean burning fuel and has a wicked octane rating. Able to produce gobs of power however it is not very efficient to pack around in a vehicle. Like propane, it must be in a liquid state to transport a usable quantity and the vessels must be able to withstand excess of 3000 psi. Not to mention that is like driving around with a medium sized bomb in your trunk. Natural gas engines uses carburetors and looooooove to be turboed too. Got your lips smacking now I bet. Can't remember the boiling point (vaporization point) Basically, you will have a series of regulators to drop the pressure down and it will gasify. Downfall, not many places to fill up and not a large range of travel. We have an endless supply piped in so availability is not really an issue. Personally, I would play more with propane

I can answer some more in detail later, just going out the door to play hockey. Must skate to maintain Canadian citizenship eh!

Hope this helps you get started

Alan Mclennan · Post by **Alan Mclennan** » October 9, 2008, 9:50 pm

Thanks Johnno!, you want me to explain something!

Don, I don't know about compressing natural gas, except they do it here to run government buses on it, and have done for some time now!.
I run my slick on LPG as we call it here, and have no problem with it, my tank holds 200ltrs so i can cover a fair bit of ground, I haven't ran it to empty yet as I don't have a LPG jerry can yet!, basically a BBQ bottle with adaptor hose to fit tank filler nozzle.
My set up is a dual throttle body system by a company here in OZ
http://www.gasresearch.com.au/ Gasresearch technologies

here's a pic of my set up, but has changed slightly now!
[img][img]http://i533.photobucket.com/albums/ee33 ... neth-1.jpg[/img]

I do believe it is not an easy task to compress NG, so as Mark said best try propane, which is not the same as you us in your BBQ.

so if you are confused and none the wiser, blame Johnno!

Alan,

I`ll try and find a diagram that shows the workings of the LPG system.

slick4x4 · Post by **slick4x4** » October 9, 2008, 9:58 pm

i had some 'natural gas' in my 4x once....
but my wife soon rolled down the windows.

Gary Seymour · Post by **Gary Seymour** » October 10, 2008, 9:33 am

I too am interested in either CNG or Propane to power my truck. I have a book on propane conversions and CNG is same principle. The gas mixers or "carbs" are simple. Pressure tank, shut off valve (vacuum or elec.), vaporizer (first electric until engine is warm - then coolant is used to vaporize the fuel), and gas lines are what is needed for the most part. The ignition timing needs to be altered. I think more intitial and less total timing advance is needed for propane. I think there are ignition systems out there that allow you to program the timing curve (?). New engines should be first broken in on GASOLINE as the soot helps to get the rings seated properly. Also all ways to keep the intake cooler helps. Sheet metal pans to keep hot oil off the bottom and heat riser passages blocked. I think propane is about 60% less than gasoline, and both CNG and LPG burn a lot cleaner. There aren't many downfalls to it except availablity of places or means to fill up. If it's not for a daily driver it shouldn't be bad to live with. Should make the vehicle emissions exempt (?).

61 Merc · Post by **61 Merc** » October 10, 2008, 10:03 am

The natural gas pipeline company I used to work for tried the conversion on a select number of vehicles, saved some money on the fill, but the time to fill and distance wasn't worth it. You have to have the capability to pump the tank to around 10,000 psi and it would still only get you a 200 miles at best. Usually with natural gas conversions they run dual fuel due to the limited mileage and availability of filling stations.

It was so time consuming that the employee's refused to use the natural gas fuel. This was done back in the early 90's but it still requires a large tank in comarisson to LPG for the same distance.

Dean

Thunderboy · Post by **Thunderboy** » October 10, 2008, 11:56 am

I used to be a mechanic for a large school district that runs several CNG vehicles, including school buses. I am also familiar with the Honda Civic GX, which is a dedicated CNG vehicle.

I would dispute a couple of points above. First is the "bomb in your trunk." Natural gas burns in a narrower window of flammability than gasoline, and it is always a vapor that rises (propane sinks) if it leaks. Statistically it is safer than gasoline in terms of flammability. I've seen videos of a fully-charged CNG tank being shot into by a high powered rifle (it did a controlled vent, and did not explode or burn) - Try that with any gasoline tank. Another tank was burned in a fire (the high pressure from the intense heat caused the tank to vent where it was designed to, and it did burn large, but very briefly - a few seconds).

Second, it is very clean burning, and does have much higher octane rating than gasoline. It works well with turbos, too. There are no carbon deposits left in the combustion chambers, and the oil drained after a normal service interval looks as clean coming out as the new oil you put in!

Most common tank storage in the US is in 3600 psi tanks, though in a effort to get better range, 5000 is becoming more common, and the industry is considering 10,000 psi.

The newer systems I am familiar with (mostly Ford, Cummins, John Deere and Honda) all use port fuel injection with two stage regulation, the first stage from tank pressure to 175-300 psi, and the second down to rail pressure (35-65psi). The injectors look the same, but they are designed for CNG. There are systems around that use a "mixer," like Alan's LNG setup (a very cool truck, I think!), but those are mostly not seen on computer controlled vehicles.

I know almost nothing about converting a gasoline engine to CNG/LNG, or about using the mixer-based systems. I have been told that the fuel system itself is the biggest difference. You can run a higher static compression ratio (Honda runs 12:1), and some engines (Tecogen, using a GM 7.4L Turbocharged V8 with a mixer, for example) have special exhaust manifolds to withstand higher exhaust gas temps. That may be due to the turbos, though, I'm not sure.

Fleets that run CNG in California anyway, are required to regularly inspect vehicle fuel systems for leaks. As you might imagine, the hard fuel lines are special, high quality pieces, and at 3000 psi, you don't run your hands around the lines to find the leaks (they are usually small and rare, BTW). Fuel filters need regular service, too.

In California, the major utility, PG&E, has a lot of good tech info, but I don't know if it is freely available on the web. In California, anyway, Ford has sold dedicated CNG vehicles such as the Crown Vic and F-150, so I am sure there is info there, too.

HTH

Drew

MrEvil · Post by **MrEvil** » October 12, 2008, 7:10 pm

Most vehicle conversions run compressed natural gas. Not Liquified natural gas. Though Liquid Natural gas is catching on.

Refueling units for CNG are about $4000. I inquired about getting one when I saw how cheap CNG crown vics go for at auction. However, it would take alot of driving to recoup the cost PLUS since I often travel far away from home I run the risk of getting stranded with NO PLACE to refuel.

LPGas a.k.a Propane is far more common, plus you can carry more Propane with you since Propane doesn't require as much pressure to liquify. (no more than 300psi)

Really the only difference between LPG and CNG carbureted engines are the fuel tank and the regulator. My dad has taken IH combine engines designed for LP and run them on Natural Gas by just replacing the regulator. However it's not so easy on the newer stuff.

moondog · Post by **moondog** » October 12, 2008, 9:49 pm

Back in 78 through about 85 I had a pickup I ran on propane. It was quit a common thing for the farmers in west Texas. It was a simple setup I aquired through the local propane dealer. I was able to swap back and forth between gasoline or propane. If I remember right it was only about 15 cent a gallon. With the gas you were standing in line every other day to fill up.
Then the State of Texas got a notion to start taxing propane as a motor fuel and it had no better value, price wise than gas.
Roger

BarnieTrk · Post by **BarnieTrk** » October 12, 2008, 10:24 pm

moondog wrote:Back in 78 through about 85 I had a pickup I ran on propane. It was quit a common thing for the farmers in west Texas. It was a simple setup I aquired through the local propane dealer. I was able to swap back and forth between gasoline or propane. If I remember right it was only about 15 cent a gallon. With the gas you were standing in line every other day to fill up.
Then the State of Texas got a notion to start taxing propane as a motor fuel and it had no better value, price wise than gas.
Roger

That would be reason enough for me to keep it under my hat if I was going to run NCG, LPG bio-diesel or any other currently non-taxed fuel in my daily driver.
This past Summer, the local NEWS did a bit on a fella that was making and putting bio-diesel in his truck - They bragged him up good. Then about a month later, the dude was back at the NEWS because their broadcast caused him to get busted for driving on the public roadways without paying highway fuel taxes......

BarnieTrk