auto gasoline to CNG conversion

[DustyBar]

I've thought about this some recently especially with the gasoline cost rising so rapidly. What would it take to convert my '03 Chevy S-10 pickup to use some compressed natural gas?

1. My daily commute is about 30 miles and I normally get about 20 mpg. How large would the fuel tank need to be for one round trip?

1. Is it possible to supplement gasoline operation with some CNG and not replace all gasoline use?

1. Can you dump some CMG into the intake and let the oxygen sensor adjust the gasoline as needed?

1. Would it work to parallel three or so electric fuel valves and open each one based on throttle position so that accurate metering wouldn't be required?

1. Is it possible to refill the tank each night at home? I found a home sized CNG advertised at around $5k, which seems a little expensive but probably wouldnt blow myself up.

1. Could an air-condition recycler be converted to compress some NG?

[Gene Williams]

DustyBar, We had a number of full size Chevy vans and a 1ton box truck with hte CNG conversions that were added on in addition to the normal gasoline. All that was needed on the fuel injected engines to switch between CNG and gas was to move the toggle switch which was installed with the conversion. Let up on the accelerator, change the switch and you are running on which ever fuel was selected.

We had a couple of cylinders very similar to welding oxygen tanks mounted and if memory is correct, it was about 4 gals equivelant per cylinder. CNG is not a liquid that vaporizes, it is under extreme high pressure 2000-3000psi.

CNG did not suppliment gas, it either ran on one or the other but easily switched between the two.

You may see only 17 or 18 mpg on CNG but it is very clean and after 3 or 4 thousand miles your engine oil will look brand new. Change it as usual and your engine will see greatly increased lifespan.

You can fill at home but it used to take a few hours. I don't know about converting a AC pump for this purpose.

We were very happy with CNG.

Gene Williams

[pegasuspinto]

1: I think it would be more cost effective to find one already converted. With modern computer controls, it takes a lot of 'mods'to make it work. there are a lot of CNG vehicles out there already, look at state and fleet auctions.

2: I'm sure you could get by with some small % with little trouble. If I was going to go this route, I think I would start by replacing the fuel pressure regulator with something electronically adjustable, and work out some kind of control that could sense load and ramp up the nat gas while lowering fuel pressure, and trying to keep the o2 in line Not the most complex project but it wouldtake some work with controls.

3: You can fill from home. I think you'd have to be pretty cautious with a home made setup. You could easily turn your garage into a blast zone!!

[RSCurtis]

To take full advantage on NG, you need a dedicated engine with about a 13:1 compression ratio- that precludes the use of gas as a supplemental fuel. I would spend the $ on a diesel conversion and enjoy the range, economy, safety, and the fueling infrastructure that's already in place.

[DustyBar]

I knew propane had a higher octane rating and could utilize a higher compression ratio but didn't know that about NG.

[OTTO-Sawyer]

Originally Posted by RSCurtis

To take full advantage on NG, you need a dedicated engine with about a 13:1 compression ratio- that precludes the use of gas as a supplemental fuel. I would spend the $ on a diesel conversion and enjoy the range, economy, safety, and the fueling infrastructure that's already in place.

I could be wrong, but with the cost difference in fuel, even if you got 1/2 or 2/3rds the milage (or even 1/4 to 1/3rd the milage) using CNG in a lower compression engine, it seems to me you'd still be money ahead, even compaired to a diesel.

I do agree on the refueling infrastructure problem though, especially if you were to go on a long trip with it.

[Jake Jacobs]

NO cheep way to build a refueling station for your home. AC compressor will not work. You need 3000-3600 psi and also a storage tank . Must meet DOT standards- not cheep. If I could come up with a cheep( not 8000 for a FILLMASTER that must be rebuild at 4000 hours) I would have done this several years ago.