CNG and LPG conversions

[sewlow]

I think lpg is out
It looks like 5.348 gallons of lpg equal 1 gallon of gas. So it would have to get amazing mileage to ever pay off.

But when comparing to gasoline, the cost per mile is cut virtually in 1/2 with

I mentioned it before, but I'll say it again just in case you missed it, since you're looking at used CNG tanks... They DO expire. They are dated, and it doesn't matter if they've been used or not.

Yup. They can be re-certified though, via hydro-static testing. Same as a scuba tank.

 

[R422b]

But when comparing to gasoline, the cost per mile is cut virtually in 1/2 with


Yup. They can be re-certified though, via hydro-static testing. Same as a scuba tank.

I am under the impression that in the usa replacement is the only option.
That said i have no clue how soon the used tanks i have in mind expire i have to find out still.
How can the cost per mile be lower on lpg at a summer low of 1$/gallon for lpg when gas is 2.25 and you use over 5 gallons of lpg to do the same as gas? I ask because i am hoping my calculations are way off.

 

[R422b]

I was way off. I just looked at the numbers again and realized 1.65 gallons lpg = 1 gallon gas. Much better i can handle that.

 

[Crookedaxle]

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.

The power loss on a vaporizer type of set-up is due mostly to the reduction in volumetric efficiency when running propane. The liquid injection type like I had doesn't have that issue and supposedly starts better in cold weather but I never ran it in the winter with the truck I had.

 

[Crookedaxle]

I had a 2005 GMC C6500 with an 8.1L and 4 speed Allison auto that ran on LIQUID propane through special injectors. It ran like a ***** ape! I would imagine it had a specific tune for the engine and made more power than gasoline however I do not know that for a fact. I'd get 6-7 MPG or so pulling a tri-axle trailer weighing 18,000lbs. or so. I got rid of it because I was afraid I'd never find anyone to work on it if something went wrong and there must have been enough wiring on the vehicle to circle the globe a few times. It was also getting harder and harder to find someone to fill it up "off the record" because of road taxes. Federated Co-Ops is about the only one that would fill it up for me towards the end of me having it. It was an old Schwans truck in it's former life. Good cheap HP. If you have a tank at home that you fill when prices are low, or better yet for tax exempt farm use, and can fill the truck from that yourself I don't know how you can't come out ahead running LPG. That's if you have a simple system you can work on yourself and doesn't cost too much upfront. Unlike what I had....

 

[R422b]

That makes sense. I am not woried about power reduction. I consider most american trucks over powered.

 

[R422b]

Sounds amazing. We have an lpg refueling station here also. Ups uses it a lot i belive there prices are good.

 

[R422b]

Anybody have any links to good lpg tanks for vehicles?

 

[sewlow]

That makes sense. I am not woried about power reduction. I consider most american trucks over powered.

My '97. The blue one. 4.3/NV3500/3.08's, +200,000 miles.
It's NOT over-powered! Lol! Not even close.
Some of the l-o-n-g steep mountain passes around here, & I'm down to 3rd gear, foot through the firewall, just to maintain 80kmh. (50mph)
...and the semi's are passing me! So embarassing!
Stock Honda Civics make more power & weigh 1/2 as much as the truck.
I figure that a 5.3 with a few mods (Cam/springs, good heads, good tune) could produce approximately 2.75x-3x more than what the getting tired V6 is producing.
450-500hp?
Throw in a gear swap for some 3.42's.
Oh yea. Now THAT's just about right! Lol!

I have a 3.73's eaton posi rear end sitting here too, but that ratio may be a bit steep for a daily.

As you can probably tell, mileage is not a real concern for me.
In the '80's I drove a car that got 6mpg, of premium, 8 months of the year for 9 years. 450hp+. As a daily. In rush hour. A stickshift, to boot. I'd spend more on gas per month than rent. Didn't care! Miles per gallon? Nahhh. SMILES per gallon. That's always been the priority.

If you look at the average wage back in the '60's and compare it to the cost of gas at the time, & then look at today's average wage & compare it to the price at the pump right now, on a percentage basis, gas actually takes less out of a person's paycheck today than it did back in the '60's.

 

[R422b]

My '97. The blue one. 4.3/NV3500/3.08's, +200,000 miles.
It's NOT over-powered! Lol! Not even close.
Some of the l-o-n-g steep mountain passes around here, & I'm down to 3rd gear, foot through the firewall, just to maintain 80kmh. (50mph)
...and the semi's are passing me! So embarassing!
Stock Honda Civics make more power & weigh 1/2 as much as the truck.
I figure that a 5.3 with a few mods (Cam/springs, good heads, good tune) could produce approximately 2.75x-3x more than what the getting tired V6 is producing.
450-500hp?
Throw in a gear swap for some 3.42's.
Oh yea. Now THAT's just about right! Lol!

I have a 3.73's eaton posi rear end sitting here too, but that ratio may be a bit steep for a daily.

And the 5.3 would probably get better mileage.
I (from an armchair point of view prefer the 4.8 i would like to build one with
Stronger rods and a good rework of the block with a cam setup for mileage.
I have 3.42 rear gears in my 2002 tahoe with 5.3 and it drives really nice. My last tank over 273.5 miles @ 2.23 gph @16.51 mpg i am not a good mileage driver. But it still does ok.