CNG and LPG conversions

[R422b]

I was wondering about CNG and LPG conversions. Has anybody here tried it? What kind? Brand? Driveability? Power? Mileage? Did it have any bad or good efects on the engine? Oil consumption?

I have been looking at Grimhall vehicle upfitters millennium cng conversions because i drive 100 to 200 miles a day on average and getting 16mpg my wallet is considerably lighter than it could be. Gas is over 2.25 and rising but CNG is 1.75 steady so i am thinking hard about converting. Any thoughts?

Sorry for not including any vehicle specifics. I drive a gmt800 2002 tahoe so it is sort of off topic for this forum but I plan to someday get a gmt400 3/4 ton suburdan for a work truck. Untill then i just read and dream on here.

 

[df2x4]

I believe CNG GMT400s were available factory from GM, at least for a couple years. My set of factory service manuals for '97 has a Bi-Fuel (CNG) supplementary book that describes an OEM CNG setup.

 

[R422b]

I have heard that. Do you know what kind of system that was? Was it mechanical or electric?

 

[Chackerman]

I just pulled a dual fuel gas/lpg system off a vortec 350 that I am working on. Had the double tanks between the rear frame rails where you spare tire normally goes. Hoses and gauge wire ran to the engine bay to the mixer/vaporizer. Then to the intake just before the throttle body. There was a module under the dash for switching between gas and propane that would kill signal to fuel pump and injectors and give power to the mixer when running on propane and vice versa for gasoline.

Not sure what the system was called but the vaporizer was a vaille which are apparently the desireable ones.

Guys I know who have run lpg in the past disliked them on cold start days but luckily they were dual fuel and they would start them on gas then switch to propane once warm. Had one truck that didn’t get up to temp often and the extra condensation from burning the lpg on short runs led to rust problems and a seized exhaust valve.

The system is heavier, heavier walled larger tanks. I think power factor is about a 10% loss compared to gasoline however lpg has a higher octane rating so you can run more timing. I think mileage is similar or a little less, so your using less expensive fuel with less power to go similar distance .

As far as oil consumption it seemed to be similar to gasoline, however propane burns cleaner and doesn’t wash down the cylinder walls so the oils stays cleaner longer, has the propane smell to it as well.

I am no expert, but have some experience with lpg in the past. If I’m wrong anybody can fee free to chime in and correct me.

 

[df2x4]

I have heard that. Do you know what kind of system that was? Was it mechanical or electric?

Looks to be electric. It has a separate ECU to control the system.

 

[R422b]

Looks to be electric. It has a separate ECU to control the system.

Not sure what the system was called but the vaporizer was a vaille which are apparently the desireable ones.

Sounds similar to the after market system i am looking at. They are 400$ new.

 

[454cid]

I was wondering about CNG and LPG conversions. Has anybody here tried it? What kind? Brand? Driveability? Power? Mileage? Did it have any bad or good efects on the engine? Oil consumption?

I have been looking at Grimhall vehicle upfitters millennium cng conversions because i drive 100 to 200 miles a day on average and getting 16mpg my wallet is considerably lighter than it could be. Gas is over 2.25 and rising but CNG is 1.75 steady so i am thinking hard about converting. Any thoughts?

Sorry for not including any vehicle specifics. I drive a gmt800 2002 tahoe so it is sort of off topic for this forum but I plan to someday get a gmt400 3/4 ton suburdan for a work truck. Untill then i just read and dream on here.

CNG isn't really economically feasible because gas is cheap right now. You also have to have a filling station near you. Also it' snot really a system that you can just DIY. Everything is special for CNG, as the pressures are very high. Tanks are rated for a certain amount of time... they expire. The whole system may need to be certified... not sure how that works. My uncle has a CNG van, and he was mentioning the other day that the CNG forum that he used to read is dead because hardly anyone is running it anymore.

 

[DerekTheGreat]

You save a ton of money by driving an old car without a payment. Least here in Michigan you'll have cheaper insurance, cheaper registration fees and yep, no payment. People always try to knock me for my "gas hogs" yet if I'm feeling smarmy I'll say something like "I spend less on gas per month than you do with your car payment."

I just don't see how it's economically feasible to either spend money & time on a conversion or another car which does better on gas. Sure, you might see instantaneously better MPG but the real question is how long will it take before your investment pays dividends or simply pays off? Most seem to omit that question or act like 5-8 years is no big deal. 5-8 years is a long time, I know personally within that type of time frame I've sold cars or things I said I'd never sell... And also, 5-8 years is a long time to expect a car to operate without any other problems or getting totaled due to a moronic, distracted driver...

 

[kennythewelder]

LPG CNG is a very clean burning fuel, so why arnt the snow flakes pushing for this instead of pushing for electric cars. Oh wait, my bad, its all about money DUH.

 

[jkeaton]

LPG CNG is a very clean burning fuel, so why arnt the snow flakes pushing for this instead of pushing for electric cars. Oh wait, my bad, its all about money DUH.

They are too worried about cow farts.