Cng Tbi

[Tippin Spotted Cow]

Alright, this is in reference to my other truck, a 91 Ramcharger 318 TBI. I've been looking into compressed natural gas as a way to keep prices down on the gasser and also take another step away from foreign oil. I know this isn't a diesel question, but TDR is one of the very few places I can find any bit of intelligence on any subject on the internet.



More to the point, what's it take to do a conversion. I'd rather use my own ingenuity to come up with something I know will work than pay some company a lot of money for a "maybe" scenerio. Is it possible to do with the throttle body injection? Do I need to modify/replace anything on the throttle body or the injectors? From what I know, I need a tank (obviously), some lines, and a regulator to step the pressure down. Beyond that I'm still in the dark. Also, I would like to keep my standard gas tank and the ability to switch between fuels as a fall back if I'm miles from the nearest CNG station.



Any intelligence is always appreciated.

 

[betterthanstock]

Looking at the most famous cng car, honda civic: They raised compression to 12:1 and stronger connecting rods.

It looks like you only have one big injector, and they have 4 small ones. Since you are injecting a gas, not liquid, it needs more capacity than your liquid injector, so maybe you could find one large CNG injector, or use 6 honda injectors (each cylinder) at higher pressure than their pressure of 40 psi, to squeeze more in. I don't know how the oxygen sensor will function, but I imagine it should be close. The other option is to go carburetted.

Read thru the following, and you'll learn something:

http://www.sceneoftheaccident.org/erg/Honda Civic CNG.pdf

 

[Tippin Spotted Cow]

I have 2 big injectors in my throttle body. Would you supposed stepping them up to performance higher flow injectors would solve the problem?



I'm not sure what to do about compression. I've also heard about stepping timing forward for CNG and having to bring it back down for gasoline... not sure how I'd accomplish that with a standard rotory distributor. I think I'd just need to set it where it needs to be to burn the CNG and run premium if ever I need to use gasoline again.

 

[betterthanstock]

Dual fuel is a compromise. If you want just CNG, then raise compression, and tune for CNG. Ethanol will also like higher compression, so that's another choice if you want dual (CNG & ethanol). Otherwise, a low compression means less mpg with CNG.

Do you intend to drive outside your city area? If not, make it just CNG.

Or you can just add a forklift carburetor for CNG, and leave your gasoline tank/computer/injectors unmodified, but the efficiency will suffer.

You need much bigger injectors than performance gasoline injectors, search the net for CNG injectors.

Or call up a CNG converting company, and try to obtain as much info as possible, without telling them that you intend to do it yourself. They may even sell you some injectors and regulators and tanks.