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I am contemplating a CNG conversion on a new MAZDA5.

Could you recommend a parts catalog that has CNG conversion kits?

Specifics: my break-even point is $10,000, based on price difference of 3.80-2.14 per gallon of fuel, and expected life of vehicle at 150,000, 25 mpg.

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    Have you considered propane? It's easier and less expensive (the conversion, not necessarily the fuel) – Move More Comments Link To Top Mar 27 '13 at 12:03
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In order to convert the vehicle you would need the following items:

  1. Fuel tank.
    • They make a few different versions of these. They more money you spend the stronger, smaller, and, lighter it will be. You can get these built from a cheap all-metal heavy designs (steel/aluminum. To an expensive extremely light weight and much smaller designs (plastic fully wrapped in carbon fiber).
  2. Fuel regulator
    • To reduce the pressure from the 3600psi+ it's stored at in the tank, to the 125psi that's required by the engine.
  3. Fuel injectors
    • This will require harness adapters to convert the factory plug to the new injectors.
  4. Fuel rail
    • To support the new fuel.
  5. Wiring harness
    • This will allow the the Engine Control Module to communicate properly with all the new components. Depending on the kit that you go with if you decide to do the conversion, it will supply you with several different harness for connection everything.
  6. Fuel management computer
    • This is used to convert the information that would have been passed to the Engine Control Module (throttle position, ambient air temp, etc.) to now be passed to the CNG injectors.

Documentation on the subject is not too easy to come by. A lot of sites that I've had bookmarked that talked about CNG have since gone missing. But I managed to find this two page article with some great pictures of what's involved and what a basic kit looks like.

My opinion:

Fueling the vehicle is too much of an issue. And if you wanted an at-home system then you would have to be ready to spend some money, and commit to driving CNG for the rest of your car owning life. Also, the time it takes to fill these vehicles is way too long and most likely the reason why you don't see more people going with CNG (from empty to full 22hours). And, the fact that their aren't CNG filling stations everywhere. I would hate to be forced to plan a trip around where I can get fuel for my vehicle.

Best of luck if you go for it. And if you do, please post some pictures. I bet a lot of the people on here would love to see how the install comes out. And your opinions on it would also be cool.

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    I have a CNG fueling station within a mile from my residence. – GregC Mar 27 '13 at 13:34
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    This is in Dallas, TX... they made it work for smaller blocks: ngvtexas.com/sales.asp – GregC Mar 27 '13 at 13:46
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    That's one station. I guess a second car could be used for trips? Also gas mileage isn't greatly increased if at all. Is it just the ~2 dollar saving on the fuel cost that sparks the interest? – cinelli Mar 27 '13 at 13:48
  • "Save the planet" argument has also crossed my mind. These days, CNG is better for environment than hybrids, when all the variables are included. But business first. – GregC Mar 27 '13 at 13:55
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Buy a Civic NG or similiar. It's the same thing as trying to add 4WD to a 2WD car. It's just easier to buy the right one to start with. Financially you would never recoup the cost over buying a purpose built CNG car. Many automakers build them for fleet sales and the US Govt has a lot in the GSA fleet. These vehicles get sold at auction and sometimes have very low miles and you can be sure that they got an oil change every 3 months and all regular maintenance performed.

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