Anyone dared a CNG converision for the 3.6L Pentastar? - Jeep Wrangler Forum

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Old 02-02-2013, 11:16 AM   #1
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Anyone dared a CNG converision for the 3.6L Pentastar?

I would seriously consider this. I live in NE PA and we are getting CNG stations as of now, CNG is $2 per gallon equivalent of gas. Nice.

I've looked at "professional" conversion companies briefly, they are crazy expensive at $15K - $20K but appear to have been done on the 3.6L Pentastar. Now a quick search reveals simple kits available on eBay for under $1K (without the holding tanks). So, has does anyone here have any experience with those, or with doing it to our new motor? Or the 3.8L for that matter.

I know with our potential head issue, it's probably not going to be a good idea until you have your heads fixed, but after that maybe. Thoughts?

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Old 02-02-2013, 01:52 PM   #2
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Man...this is one of those instances I'm gonna trust my gut instinct: no good can come of a $1K kit that purports to do what was previously accomplished by a $15K-$20K conversion.

Run.

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Old 02-02-2013, 01:53 PM   #3
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I could be wrong, of course. But I wouldn't wanna be the guinea pig on this one...
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Old 02-02-2013, 02:17 PM   #4
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CNG can be a decent prospect for fleets, commuter vehicles, and such vehicles in cold climates. However, a vehicle has to be engineered to accept the fuel and CNG is not a 1:1 equivalent of gasoline. CNG has about 35% less energy per equivalent unit of gasoline, so you will have less HP and less torque.

Chrysler may have done the computer programming to make the engine control unit recognize and properly run the vehicle on CNG for potential fleet use, but there is no public release of it that I know of.

The physical components of the engine often have to be reengineered and re-spec'ed for CNG. Lubricating oils are different, different fuel delivery parts, etc.

In the Seventies, this was a popular idea with the alternative energy folks. They'd rip off the carburetors and gas tanks, then refit a used '73 Olds. Most never got them to run right over the long term and with computer controlled 21st century vehicles, I wouldn't try it without being fully conversant in automotive engineering or being an ASE certified Master Tech.

A $1,000 parts kit is going to equal a conversion costing tens of thousands? Not a chance in the world.
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Old 02-02-2013, 02:29 PM   #5
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......and ya can't just buy CNG everywhere.
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Old 02-17-2013, 10:03 AM   #6
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......and ya can't just buy CNG everywhere.
It's an interesting concept. I've heard rumors that otr truckers are starting to convert to CNG. All of the garbage trucks in my area are running CNG too. Also, from my research, I am finding that CNG will get you 90% of what you're getting with gas, is this not correct? There are a lot of vehicles using it now if you think about it; city buses, fork lifts etc. If we are the Saudi Arabia of nat gas why not? There are also home filling stations available too, GE is supposed to be coming out with one.
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Old 02-17-2013, 10:25 AM   #7
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I would seriously consider this. I live in NE PA and we are getting CNG stations as of now, CNG is $2 per gallon equivalent of gas. Nice.

I've looked at "professional" conversion companies briefly, they are crazy expensive at $15K - $20K but appear to have been done on the 3.6L Pentastar. Now a quick search reveals simple kits available on eBay for under $1K (without the holding tanks). So, has does anyone here have any experience with those, or with doing it to our new motor? Or the 3.8L for that matter.

I know with our potential head issue, it's probably not going to be a good idea until you have your heads fixed, but after that maybe. Thoughts?
Here in W. OK cng is 1.39 per whatever. Lots of the oil company's are using it as well as trucking company's. a conversion is about 5-6k from my research but most leave the gas on as well so can still use it when cng not avail, the Pentastar does have the hardend valves for a conversion to it but ther is really no room for a tank without taking up space in the back.
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Old 02-17-2013, 05:20 PM   #8
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CNG is not a lot different than LPG and tons of forklifts and equipment run it . Starting to see garbage trucks and buses here in Ohio running on CNG.From what I have read they are starting to sell compressors for people to use at home .Not uncommon for folks around here to have wells on their property and have a free gas allotment.
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Old 02-18-2013, 06:59 PM   #9
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I am planning on doing this in a few months. Here in California I get natural gas at my house for less than $1 GGE. There is the upfront cost of the home refueling station (~$3500 after a tax credit) if you go this route.

My understanding is that CNG conversion costs by legal installers are artificially high because of government licensing fees which can exceed $100,000 per year per engine model. A diy install can be accomplished for as low as $1000 with a small CNG tank.

I will try to remember to post to this forum if I do it.
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Old 02-18-2013, 07:41 PM   #10
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I would not even begin to consider the possibility of even considering this. In fact, I'd go so far as to say you should re-consider having considered it in the first place. If you want to drive a CNG vehicle, find a used one for sale on craigslist and drive it daily. Keep the miles off of your jeep and drive your jeep on weekends, road trips, nice days, whatever.
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Old 07-11-2013, 12:52 AM   #11
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Some of these responses are pretty amusing.

Anyway, my brother-in-law has taken classes for CNG conversions and is now opening a business that specializes in it for our area. Probably the only one anywhere near here. I suspect I will have my JKU converted to bi-fuel (gas / CNG) in the near future. We have a local refueling station.

I'd be interested in hearing from others who are doing this, or are considering doing it. If your entire response is nothing more than why you think it's not worth it or why it shouldn't be done, do some more homework, lol. The benefits in a real world scenario are pretty good.
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Old 07-11-2013, 01:13 AM   #12
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I would not even begin to consider the possibility of even considering this. In fact, I'd go so far as to say you should re-consider having considered it in the first place. If you want to drive a CNG vehicle, find a used one for sale on craigslist and drive it daily. Keep the miles off of your jeep and drive your jeep on weekends, road trips, nice days, whatever.
I'm with you on this one. I work on NG engines all day every day and would NEVER consider the possibility of considering this conversion!
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Old 07-13-2013, 02:40 PM   #13
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There is nothing intrinsically unsafe or that much different in running CNG versus gasoline. It's been done tens of thousands of times in conversions that are racking up millions of miles. You don't want to do it to your rig and like paying twice as much for fuel and sending that money over to the middle east, that is your right and I respect that. My brother in law has been certified for doing CNG conversions and is currently doing it on his Ford Raptor, so I guess he is pretty confident in the systems and the stock components in handling CNG versus gas.

It's not rocket science, I'm more interested in hearing from people who have real world experience than people who don't want to do it. I'm not looking for justification or support in my decision on what I do with my rig. Like it or not CNG is the only true viable alternative fuel and it's American sourced so I think it will be a big deal in the not too distant future.
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Old 12-25-2013, 12:37 PM   #14
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It's not rocket science.
Reviving an old thread . . . Has anyone gone ahead and done this? I found one thread on a CNG site with a tank in the back and a cng range of 120 miles. It retained the petrol system and could switch between them. However it was problematic. That was 2011 though and conversions may have improved since then.

http://www.cngchat.com/forum/showthr...sic-new-to-CNG

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Old 07-10-2014, 01:09 PM   #15
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Just to let everyone know, I took the plunge and I guess I am the Guinea Pig on the first 2014 wrangler with CNG. I already owned a E-350 that is a dedicated CNG van, so it wasn't a big jump for me to try it on my daily driver. I have about 2000 miles on the jeep so far with CNG and so far, so good. I had a great, knowledgeable company (Mach Fuels in Chattanooga,Tn) do the conversion and they are very interested in the data as well since this is a new engine design, and unchartered territory for CNG. CNG seems to change the shift points, but other than that, no difference in driving the Jeep at all. I seem to get about the same or maybe slightly less MPG around town and for sure ONE MPG BETTER on the highway than on regular gasoline. Our local utility district recently installed a filling station so that was huge in my decision to do the Jeep, plus we can buy CNG for $1.98 GGE (Gallon Gas Equivalent). So, depending on the day you look at gas prices, I am generally buying CNG for about $1.40-$1.50 less that standard gas.
This is not a cheap conversion, my guess is I need to drive the Jeep about 65K miles to recover the investment of converting before I see any real savings in my pocket. However that number can vary depending on where you live with some states having tax incentives, etc to do conversions. Here in Tennessee we don't see those at all at this point.
Planning a trip is a bit more than just stopping at any exit for fuel. We did a 1600 mile trip last week from Pigeon Forge, Tn, to Siesta Key,Fl and back. My range (10GGE) is about 180 we think (figuring 21mpg highway and probably 8.6 usuable fuel volume). We had two segments that were 179 and 177 miles each, so there was a question as to if we would have to switch back to gasoline, but we made it fine and did the entire trip on CNG. Prices varied from $2.59 (atlanta) to $2.49 (Athens,Tn) to all other stops at $2.35. Remember, in Florida and Georgia, regular gas ran anywhere from $3.39 to $3.89, depending on where we were at.
Anyway, I am very happy so far with the performance and mileage of the conversion and while I am certainly no TREE HUGGER, it is nice to buy fuel cheaper and know I am "driving green" in something other than a prius.
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Old 07-10-2014, 01:48 PM   #16
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Guy at the local uhaul store told me he has cars that fill up there.

Dual fuel with a "phil" station in your garage would be nice OR

Converting a diesel to run on fry oil.
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Old 08-14-2014, 11:15 PM   #17
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CNG can be a decent prospect for fleets, commuter vehicles, and such vehicles in cold climates. However, a vehicle has to be engineered to accept the fuel and CNG is not a 1:1 equivalent of gasoline. CNG has about 35% less energy per equivalent unit of gasoline, so you will have less HP and less torque.

Chrysler may have done the computer programming to make the engine control unit recognize and properly run the vehicle on CNG for potential fleet use, but there is no public release of it that I know of.

The physical components of the engine often have to be reengineered and re-spec'ed for CNG. Lubricating oils are different, different fuel delivery parts, etc.

In the Seventies, this was a popular idea with the alternative energy folks. They'd rip off the carburetors and gas tanks, then refit a used '73 Olds. Most never got them to run right over the long term and with computer controlled 21st century vehicles, I wouldn't try it without being fully conversant in automotive engineering or being an ASE certified Master Tech.

A $1,000 parts kit is going to equal a conversion costing tens of thousands? Not a chance in the world.
You seem to be on a different planet! There is a switch.. A literal switch, that you toggle that turns on natural gas and turns gasoline off, without any hiccups, the vehicle continues to run. New cars have computers to tune the timing and fuel mixtures. They are expensive because the EPA has not classified them yet and it is difficult to place the tanks in a safe place, cert for mechanics to install them, etc... A lot of red flags and tape especially since there isn't a standard refilling station. You could probably take a tank, run a line into the intake and start pumping natural gas into it... The concept is simple, the parts should be cheap, finding a filling station and a certified holding tank is the most difficult part so far as well as finding a certified installation mechanic.
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Old 08-14-2014, 11:16 PM   #18
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I am curious to hear from anyone that has a conversion kit on any car.
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Old 08-14-2014, 11:22 PM   #19
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You seem to be on a different planet! There is a switch.. A literal switch, that you toggle that turns on natural gas and turns gasoline off, without any hiccups, the vehicle continues to run. New cars have computers to tune the timing and fuel mixtures. They are expensive because the EPA has not classified them yet and it is difficult to place the tanks in a safe place, cert for mechanics to install them, etc... A lot of red flags and tape especially since there isn't a standard refilling station. You could probably take a tank, run a line into the intake and start pumping natural gas into it... The concept is simple, the parts should be cheap, finding a filling station and a certified holding tank is the most difficult part so far as well as finding a certified installation mechanic.

I drove a CNG vehicle for work for a number of years and they were sole fuel vehicles. Your experiences are not solely universal.
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Old 08-15-2014, 01:23 AM   #20
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Anyway, I am very happy so far with the performance and mileage of the conversion and while I am certainly no TREE HUGGER, it is nice to buy fuel cheaper and know I am "driving green" in something other than a prius.
Sorry, but if anyone criticizes those who prefer CNG over gasoline as "tree huggers," they're idiots, plain and simple. I wouldn't worry about convincing such a person of the viability of CNG. And yes, I realize you were not calling CNG'ers "tree huggers," so that comment was not directed at you. Just an fyi.

CNG is cheaper. It gets almost the same fuel economy. There's no reason not to use it except availability and cost efficiency (i.e., conversion cost). If there were CNG-equipped Jeeps from the factory, and locally-available CNG stations, there's no doubt a lot more people would use it. I would! Hopefully we get to that point one day. I could care less about using gasoline in the Jeep if CNG was available. But, I'm not going to do a conversion because I don't think it's a good investment at this point. I'd rather just buy a CNG Jeep from the factory. At least you maintain the powertrain warranty that way (which is a good idea because there's bound to be some problems during the first couple years).
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Old 08-15-2014, 05:30 AM   #21
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Back in the early 90s, we had a Suburban with a 454 which also ran on CNG. It was a toggle switch we hit to change it back and forth from gasoline. If we weren't towing, it ran exactly the same. The only time you could feel the power loss was towing our 27ft camper. (It still worked fine) One thing I noticed was the engine oil. It always looked like it did after an oil change, never got dark. Really, the only drawback was the size of the 2 tanks behind the rear seat, and the range it offered. I can remember filling up for about 8 bucks, which would go about 150kms.
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Old 08-15-2014, 07:43 AM   #22
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We have no where that sells cng anywhere around here.
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Old 08-15-2014, 10:03 AM   #23
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Our local utility district recently installed a filling station so that was huge in my decision to do the Jeep, plus we can buy CNG for $1.98 GGE (Gallon Gas Equivalent). So, depending on the day you look at gas prices, I am generally buying CNG for about $1.40-$1.50 less that standard gas.
Does CNG have all the same direct and indirect taxes on it, like road taxes, that gasoline has included?
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Old 03-30-2015, 10:31 AM   #24
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CNG Jeep?? We built one!!

We just finished building a CNG Jeep! It will run on gasoline or Natural Gas. We will be at Jeep Safari this weekend if you would like to see it!!
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Old 03-30-2015, 11:44 AM   #25
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I handle the insurance on a business who does CNG conversions in Oklahoma. I think their prices are about $10K. He has people call every day asking about doing their vehicle and he tells them that if they drive less than 25K miles a year, it won't be worth it.

I would also be scared of doing a retro fit like this myself. You have a tank of compressed natural gas in your Jeep now, go watch them flare a natural gas well if you are curious as to how well that stuff burns.

If you have any questions about what happens when your home made conversion goes wrong, take a look at this.
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Old 03-30-2015, 01:15 PM   #26
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We just finished building a CNG Jeep! It will run on gasoline or Natural Gas. We will be at Jeep Safari this weekend if you would like to see it!!
Here are some photos if anyone is interested!
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Old 03-30-2015, 04:52 PM   #27
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Here are some photos if anyone is interested!
Well, you've got a couple problems there.

Firstly, there are no certified EPA kits for the Jeep Pentastar, so it is actually illegal for this vehicle to operate anywhere but offroad. The full list of certified vehicles and drivetrains can be viewed here:

Alternative Fuel Conversion | Cars and Light Trucks | US EPA

Secondly, it is inherently dangerous to have your fuel tank in the passenger area... rules and regs specify a compressed gaseous fuel tank need to be separated from the passenger area of the converted vehicle, either in the trunk or under the vehicle.

Not trying to rain on your parade, but the last thing alt fuels needs is black eyes from bad or illegal installs.
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Old 03-30-2015, 04:57 PM   #28
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Does CNG have all the same direct and indirect taxes on it, like road taxes, that gasoline has included?
If you fill up at a CNG vehicle fueling station, yes, you pay a road tax.

If you have a personal, time fill fueling station at home hooked up to your natural gas service, not so much.
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Old 04-06-2015, 12:20 PM   #29
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Well, you've got a couple problems there.

Firstly, there are no certified EPA kits for the Jeep Pentastar, so it is actually illegal for this vehicle to operate anywhere but offroad. The full list of certified vehicles and drivetrains can be viewed here:

Alternative Fuel Conversion | Cars and Light Trucks | US EPA

Secondly, it is inherently dangerous to have your fuel tank in the passenger area... rules and regs specify a compressed gaseous fuel tank need to be separated from the passenger area of the converted vehicle, either in the trunk or under the vehicle.

Not trying to rain on your parade, but the last thing alt fuels needs is black eyes from bad or illegal installs.
Our kit is EPA Certified. All is road worthy.
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Old 04-06-2015, 12:26 PM   #30
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I have only one question... How many rounds of rock-paper-scissors did you guys need to go through to determine who would be driving that offroad Hindenburg?

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