Compressed Natural Gas (CNG) conversion to cars- any experience?

[FunInDuhSun]

This thread ISN'T about propane, LNG, or the low-pressure houshold natual gas delivered via pipe to homes.

CNG is the exactly the same gas piped into homes, but for vehicular use the gas must be compressed to 3000 or 3600#. At this time there doesn't seem to be a safe, reliabile way to pump up home gas to a pressure needed for re-fueling.

In the US there are hundreds of CNG filling stations, and it happens that there are are 3 along the route of my normal commute. One is only 4 miles from home....

Gasoline sin't getting any cheaper, so I've been researching the possibility of converting a couple of my vehicles to dual-fuel CNG/gasoline.

Looks like it's doable for about $2K including a 7# tank. I think QC modifies trucks, so it it cost effestinve enough when the CNG stations are enroute?
I have a jeep SUV wuth a thirsty V8 and a Ford F250 Jeep tank will use up a lotta room, but truck has ruoom to sparre
What say you.

 

[QC]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

What's a 7# tank? How much do you pay for gasoline? How much will you pay for CNG? How much fuel do you burn annually in each vehicle precisely. Your answer is in the answers to those questions.

 

[Scott Danforth]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

did many CNG conversions a few jobs ago. they were for municipalities. the CNG tanks, regulators, etc took a bit of room. I would look into a diesel swap prior to a CNG swap myself.

The watchouts are higher combustion temps than with gasoline. depending on the application, you may need engine modifications for the higher combustion temps. we used to melt valves and warp heads often.

a dual fuel setup is a bit more complicated as you have two fuel systems to contend with, however does offer the benefit of the ability to fuel at both a CNG station and a petrol station.

 

[QC]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

I would look into a diesel swap prior to a CNG swap myself.

Never would pay back in a personal car IMHO.

 

[Scott Danforth]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

helped a co-worker do a CJ7 that went from 18 mpg to 31 mpg. was a 4BTAA - T5 swap with tweaked fuel pump. the fuel savings alone over a year paid for the conversion.

 

[QC]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

Can you post the $ numbers, Scott? If you get a great deal on the engine, then maybe. I don't deny it can happen, but it takes a lot to pay back $10,000. Just depends on the numbers. It's not necessarily about the MPG, it's about the MP$. You have to burn fuel to save money on fuel. If you only burn 500 Gallons a year it's hard to pay back anything.

I don't mean to be argumentative. Diesel engines are what I have done my entire career. I have some preconceived things that get in the way of super deals that some may come across. All good.

 

[Fishing Dude too]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

Maintance is cheeper too as less oil changes

 

[rbh]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

Just typing out loud here_
CNG and propane are virtually the same "I believe" when it comes to fueling up at the pump.
and as for the hardware they should not be that different, "should it"??
I think rejetting is all that would/should be required.

http://www.impcoautomotive.com/index.php?pagename=home


(We have 2 e150s on propane and a f150 as well and all use impco)

 

[geneseo1911]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

Actually, there are a couple companies making compressors for residential installation. They run in the 5K range. There are subsidies available. IL, for example, will pay up to half the cost of conversion and the compressor. CNG is measured in Gasoline Gallon Equivalent. The residential pumps will do 1-2 GGE/hour, so you're looking at an overnight fillup. Right now, a GGE of CNG is about half the cost of a gallon of gasoline. The US has enormous NG reserves, and the price of natural gas at the wellhead is so low right now, many places are burning it because it is not economical to ship it. Even when NG prices were higher, a GGE was about 70% of a gallon of gas.

I was reading that conversions are available for a number of common engines and run around 10K, and that vehicles have to be new or nearly new. I'd be interested to see what the op has found, as that looks a lot better than the info I was looking at. I'd love to convert my current pickup rather than buy new.

The only current factory CNG vehicle is the Honda Civic GRX (GSX...not sure if that's right), but next year, GM will begin selling Chevy & GMC pickups with a dual fuel converted 6.0L V8. It will have a standard gas tank, and a CNG tank in the bed. I believe it is somewhere around 20GGE, giving the truck a 650 mile range. We have been looking at these for the farm as we are connected to a cross country pipeline and can buy the gas very cheap. Dodge is also releasing one next year. I am hopeful this becomes a trend. NG burns cleaner, creating less pollution and longer engine life with less maintenance, and we have ample domestic supply.

 

[QC]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

CNG and propane are virtually the same "I believe" when it comes to fueling up at the pump

Actually they are very different. Can elaborate if we need to.

The only current factory CNG vehicle is the Honda Civic GRX (GSX...not sure if that's right

GX I think. Great car!!

GM will begin selling Chevy & GMC pickups with a dual fuel converted 6.0L V8.

There are factory approved Ford systems as well. Announced a couple of weeks ago.

Always verify what "dual fuel" and bi-fuel actually mean. Generally the industry uses dual fuel to describe a diesel engine that uses nat gas as it's primary fuel with diesel used as a "pilot" for ignition. Two fuels simultaneously . . . Bi fuel usually refers to one or the other, gasoline or nat gas. Regulators often use these terms 100% reversed. Very helpful :facepalm:

Edit: Anybody interested in detailed discussion an any of this PM me. There is so much bad info out there. I specialize on heavies, but know light duty as well.

 

[sprintst]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

I'm actually looking at picking up one of the cng GMC trucks next year. Makes sense for use as natural gas is much cheaper, cleaner and everywhere around here. It will just be an issue of refeuling stations catching up.

 

[Scott Danforth]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

Can you post the $ numbers, Scott? If you get a great deal on the engine, then maybe. I don't deny it can happen, but it takes a lot to pay back $10,000. Just depends on the numbers. It's not necessarily about the MPG, it's about the MP$. You have to burn fuel to save money on fuel. If you only burn 500 Gallons a year it's hard to pay back anything.

I don't mean to be argumentative. Diesel engines are what I have done my entire career. I have some preconceived things that get in the way of super deals that some may come across. All good.

It helped that I worked at Cummins at the time for access to a few of the miscellaneous parts, however most of the parts came from salvage yards. the engine came from a wrecked frito-lay truck, the transmission came from an S-10. total cost of the swap was about $3500

Here is a great forum for swaps http://www.4btswaps.com/forum/forum.php

Here is a low mileage 4BT http://columbus.craigslist.org/pts/2947001715.html

 

[QC]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

Well I can't join another forum as that would mean Divorce . . . But $3500 over 15 MPG (previous engine) means you'd need to run almost 30,000 miles for a payback. (double your mileage even with fuel the same price). Like this: 30K miles today (15 MPG gas, $4/G) = $8K. 30K tomorrow (30 MPG diesel, $4/G) = $4K . . . And that assumes two things, double the mileage (questionable) and gas and diesel at same price (diesel is higher). That's why I say it rarely pays. Coolness factor? Heck yeah. economics. Hard to make a case without really good deals on the diesel.

 

[rbh]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

QC/Kev with regards to the "almost the same thing" (prop to cng) at fill, I realize that prop doesnt need the same amout of compression as CNG and that a fill takes alot more time to fill for CNG, but I am betting that the parts are >>"almost"<< the same.

 

[QC]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

Parts on engine, yes. Refill and storage stuff, very different. Wrap your head around 3600 PSI. In some ways LPG is more like LNG, but to be fair they all have similarities (gasses) and all are pretty different too.

 

[puddle jumper]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

Just typing out loud here_
CNG and propane are virtually the same "I believe" when it comes to fueling up at the pump.
and as for the hardware they should not be that different, "should it"??
I think rejetting is all that would/should be required.

http://www.impcoautomotive.com/index.php?pagename=home


(We have 2 e150s on propane and a f150 as well and all use impco)

+1 very close to the same. All the BC gas trucks run on Natural Gas. Supply could be another thing.

 

[Fleetwin]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

QC is correct.

CNG is a great engine fuel but..........

-3600 PSI tanks and filling systems are necessary.
-The tank mounting can be an issue. For any range, they need to be quite large.
-Engine power will be about 75% of gasoline or propane.

On the plus side...........

-Nat. gas is relatively cheap.
-CNG WILL be the "fuel of the future" especially for Fleet applications. Especially for those that can use a centralized fueling location.

Personally, I would go propane.

-You can fill at MANY more locations.
-Propane tanks are much smaller/usable amount.
-Propane is almost 1:1 with gasoline as far as performance.
-Propane is still much cheaper than gasoline. Propane is a by-product of oil well drilling and refining.

A nice propane conversion (EFI) could cost upwards of $10K. You would have to do your mileage calculations based on that of gasoline and factor in the cheaper/gallon price. If you do a lot of local driving, it makes a lot of sense.

I have an old Jeep CJ-5 (GM 2.5L) that I am considering a carbureted conversion for. The carbureted conversions are much cheaper.

 

[dolluper]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

Well around here we have had factory natural gas converison vehicles for about 15 years.....Ford was pushing crown vic's for cabs....cng converts to most vehicles aftermarket were 3500 bones.......propane was 2500 bones taxi fleets went with propane of coarse....less cost to convert ,bigger tanks,more availability,more engine power [130 octane}.......much cheaper cost for propane compared to gasoline but now gasoline ,propane are same price .......less mileage on propane......a good thing propane was ,burnt clean was never supposed to be taxed.......but the gov bean counters couldn't resist and it's taxed now therefore equal costs for less mileage go figure

 

[QC]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

The only reason CNG delivers lower power is that it displaces air in the cylinder. Propane too. Both have higher Octane. Natural Gas, primarily methane, is higher. 140 - 120 I think, but I'll look into that. If the engine is built around that, you can get very good performance, but of course with conversions they are built for gasoline. Propane is rarely, if ever, as low cost as Natural Gas and has bigger seasonal price swings. Propane is indeed easier to handle, store, and transport. One downside is it is heavier than air, while Methane is lighter than air. Methane spill? No such thing. Propane will not remain liquid at ambient temperatures and pressure, but in gaseous form will go down a drain . . .

 

[halfmoa]

Re: Compressed Natural Gas (CNG) conversion to cars- any experience?

The only reason CNG delivers lower power is that it displaces air in the cylinder. Propane too. Both have higher Octane. Natural Gas, primarily methane, is higher. 140 - 120 I think, but I'll look into that. If the engine is built around that, you can get very good performance, but of course with conversions they are built for gasoline. Propane is rarely, if ever, as low cost as Natural Gas and has bigger seasonal price swings. Propane is indeed easier to handle, store, and transport. One downside is it is heavier than air, while Methane is lighter than air. Methane spill? No such thing. Propane will not remain liquid at ambient temperatures and pressure, but in gaseous form will go down a drain . . .

CNG octane is 130 [(R+M)/2]