Why does my CNG car run out of gas so quick?
Posted by Exciting-Process977@reddit | askcarguys | View on Reddit | 41 comments
I own a 2009 Honda Civic Natural Gas Vehicle. It only fills up about 5.3 gallons of gas and I have to refill it just about every 140-160 miles. It’s very frustrating and I was wondering if this is normal or if there’s something I can do to fix this. Because I hear of Civics that typically hold around 10 gallons which would make my life so much better. Thank you!
som_juan@reddit
150 miles/5 gallons = 30 mpg. Am I missing something?
Standard-Affect-9004@reddit
I have a CNG Impala for work. It claims to have a 8 GGE fuel tank. However, I have never been able to get more than a 6 gal fill up. There is a pressure cut off that shuts the fuel off when it gets too low. However since you are getting 30 mpg, you probably are just reaching your limit. The bad news is CNG tanks have a limited life of 15. 20 or 25 years. Check your tank and determine how much life is left. Tanks beyond their life shield should be replaced.
Own-Appearance-824@reddit
I worked for a company that put CNG in the work trucks. The CNG bottle was so big they had it in one of those aluminum tool boxes. I'll say this, I'd fill the bottle and drive to several sites maybe putting 75 miles on the truck. I would use at least 1 tank a day and still flip the truck back over to gasoline. We valued space in the truck more than the cost savings so we removed the CNG.
LrckLacroix@reddit
“Honda claims 225-250 miles on a full CNG tank, but independent tests have found slightly lower ranges.” From a quick skim it looks like people get 150-200 miles per tank. Hondanews says “8.0 GGE @ 3600psi”.
I would probably look into the condition of the tank. Looks like they are designed to last 15-20 years.
After-Chair9149@reddit
That sounds like my range in my 25 year old pickup with a 25 gallon tank! At that rate I’ll keep my fun lifted truck.
StonccPad-3B@reddit
Well yeah, the CNG car only has an 8 gallon capacity.
Exciting-Process977@reddit (OP)
this really helps, thanks g
50plusGuy@reddit
Mine had a 60l tank that provided about 140km.
CNG is damn bulky.
On the plus side of things: That tank held only 10kg, (the unit we have to pay for, here, which did cost in the 7.5l gasoline - less than 100km - ballpark.
Hersbird@reddit
I have a 120 gallon tank that was in the bed of a dual fuel 3500 silverado I once had. It had that much propane, and also 34 gallons of unleaded. It's about 4.5 feet long and 2.5 feet diameter. If you can figure out a spot to mount it on your civic you can have it, lol.
bomber991@reddit
I’ll just say I’m proud all these responses were on topic and nobody suggested something like eating more beans in your diet to help produce more natural gas for your car.
xxrambo45xx@reddit
I dont have experience with CNG engines beyond forklifts, but its my understanding having looked into going CNG for a project that propane has significantly less energy in it than gasoline does, its cheaper to fill, and more environmentally friendly but overall performance and mpg takes a dive ( ive never seen a CNG race car)
As far as more capacity it seems like the solution would simply be a bigger tank but ive never seen one of these vehicles in person so im unsure how hard that would be
Would be cool if it just ran off bbq tanks though easy to swap out and easy to get a bigger one
ThirdSunRising@reddit
They’re getting 30 miles to the gallon on it which seems fine for CNG, their issue is a five gallon tank which seems awfully small. I’m wondering if maybe the gauge is showing empty when they still have half a tank?
erroneousbosh@reddit
If it's a cylindrical tank it has to be mounted at the right angle for the gauge to work correctly, and sometimes they get moved off the correct angle to make the pipework easier.
Also the float on the multivalve (similar to the float for your normal fuel gauge, but also controls the shut-off valve for filling as well as the level gauge) might be porous.
There's probably a small mechanical gauge on the tank and it's worth looking to see what it says with the tank full and empty. Most CNG and multipoint LPG systems will switch back to petrol if they detect low feed pressure, although some just go by the tank gauge - feed pressure is more common because it's a lot safer.
xxrambo45xx@reddit
Fine for CNG but im fairly sure the ICE of this car get 40 or so
That could be it too, i was also wondering if its cold where they live as something in a conpressed state is less compressed when its cold... less pressure kinda equals less fuel, or at least less usable fuel
DegreeAcceptable837@reddit
1st comment made alot of sense, 2nd one less.
it's cuz cng have less energy, 5gal for 150 mi is correct.
gas version gets maybe 35 best.
Don think cold have anything to do with it, on the cng side, but it does run cooler, so if car is not at operating temp on cold days, it would get worse mpg.
solution is a thermostat that opens at hotter temp, and under hood insulation
Ponklemoose@reddit
I think it hit early.
xxrambo45xx@reddit
I was entering the void as i typed the last
CrashSlow@reddit
CNG is Compressed natural gas,, not to be confused with liquified natural gas... Aka methane. Same problem as propane, way less power.
erroneousbosh@reddit
CNG isn't very energy-dense so it has way less power but propane gives you a bigger slower bang. You get way more power on propane, particularly if you adjust your ignition timing to suit it.
If you were really going for it, you'd run about 12:1 compression because there's not a hope in hell of it ever knocking no matter what you do.
Zhombe@reddit
Also you can never use the entire tank. Just like our propane. Once you use 2/3 you lose too much pressure till you fill back up.
xxrambo45xx@reddit
Well theres the hole in my explanation, even if it still stands true
For clarity i was looking into building a propane rig for a rock crawler like 15 years ago, bit of lapse on my part
erroneousbosh@reddit
You actually get better performance on LPG by a considerable margin because it's the equivalent of 115 octane fuel and you can run an unholy amount of advance since it cannot pink or knock. It's much harder to get propane to light up than petrol and you'll get through a set of spark plugs a lot quicker - on my Range Rover I get through a set in 10,000 miles but fortunately they're just lawnmower-grade BPR6ES plugs at under a tenner a set.
Propane just does not want to explode like petrol vapour does.
You can't really run LPG vehicles off barbecue tanks because you need a liquid pickup for the vapouriser (although I guess you could turn them upside down). Forklift tanks are similar but have a liquid pickup tube running to the bottom of the tank which is why you have them sitting with the writing the right way up in their holder!.
xAugie@reddit
Honestly most Lifts now and for the past 10yrs have been hydrogen fueled? Or the old school ass battery
Leverkaas2516@reddit
How is it possible to choose a Natural Gas Vehicle without understanding the fundamental differences from a normal gas-powered car?
The fuel us different. The tank is bigger, heavier, and holds less fuel. Gasoline is more compact and easier to contain, as a matter of physics. There's nothing to fix.
Exciting-Process977@reddit (OP)
oh wow thank u, i had no idea that my cng car was different from a normal gas car! thanks legendary redditor!
imightknowbutidk@reddit
Why own a cng car? Also where are you located? Quick google search shows 8 gallon capacity and 180-220 miles range
AntiSonOfBitchamajig@reddit
Why own a cng car? When you have a good residential contract and a home fill station... it can be literally 75%+ less cost per mile than a comparable gasoline vehicle. The big suck is the refill time, overall energy density, and lack of stations, that killed it. LNG is taking off in China... so that'd be cool and help solve the density problem.
IMO though... blending NG with diesel engines is where its at, and is what im currently messing with on my cummins project vehicle.
imightknowbutidk@reddit
I’ve never heard of that before, how would you blend cng and diesel? An extra set of injectors in the manifold to spray a tiny amount of cng for an extra boost?
AntiSonOfBitchamajig@reddit
It isn't a boost but a blend. Most modders have agreed 50-66% of BTU content can be substituted. Uses the Diesel injection to pilot the burn. CNG is added to intake, there are several ways to add it. Some systems will use the intake air to heat the injection of it, others will use the coolant. Intake is much prefered, and post innercooler is even better yet, but theres a ton that can be done to make it more efficient rather than just leaking it in. But you can even add water mist... but err, getting into the weeds here... just know there are pretty large benefits as long as you can fuel it cheap, it really helps the burn, due to it being well mixed pre combustion event, power not so much (and actually less) Like on a 8.3 cummins... the NG version is LESS THAN HALF the power at same rpms vs diesel at only 99HP for a 8.3L BUT the fuels cheap... so.
Unlikely-Moose-4563@reddit
Tap the intake manifold
AlphaDisconnect@reddit
Entropy. Gas an diesel have more... gas? Laws of thermodynamics plus a 5 gallon tank when my gas car has 20 ish. Not gonna hate on the natural gas. Good on you.
outline8668@reddit
CNG does not liquify when you fill the tank like propane does. When propane is compressed back into a liquid it takes up less space. I forget what the ratio is but it's a significant space savings. CNG doesn't liquify at the pressures your fuel tank can hold, this means whatever you can pressurize in there is all you got.
ericbythebay@reddit
What’s the capacity printed on your tank? What is the PSI where you are getting it filled?
Lower PSI will have less range as there is less fuel in the tank.
Drove a CNG car for years and also didn’t like the range.
Monotask_Servitor@reddit
We had a lot of CNG conversions in New Zealand in the 1980s because NZ produced gas but had to import petrol, so the government basically subsidised it. Range was always a lot less than on petrol presumably because you’re storing a gas rather than a liquid in the tank and it takes up a lot more volume unless highly compressed.
too-slow-2-go@reddit
Because the tiny tank is in the trunk. I have a 2012 GX. I bought new it was awesome when CNG was about 90 cents a gallon. Now it's just a little cheaper than unleaded and the pumps are always broke down. I'd sell it but not a lot of people want a dedicated CNG car
series_hybrid@reddit
A gasoline molecule has 8 carbons in a chain, and a propane molecule has 3 carbons. A natural gas molecule (methane) has one carbon.
durrtyurr@reddit
09 Civics generally get around 30 mpg combined, at least USDM models. This seems totally in line for me. Even the gasoline ones are annoying because of their short fuel range. My general rule is that any highway car I have needs to break 500 miles of range to even be considered, I hate stopping more often than that.
Skyline43@reddit
You mention it yourself the tank is very small capacity. Look it up on google and you'll see a tank that takes up the whole space behind the rear seats and half of the trunk. It's super beefy, but doesn't hold that much. CNG is under thousands of pounds of pressure and needs to hold up in an accident so it doesn't explode. Picture a bbq propane tank on steroids. Small capacity and 27ish mpg and it makes sense you only get 140-160 miles of range.
DangerousChip4678@reddit
My son drives one and I’m not sure how much he actually puts in but it costs him about $20-$25 and we’re in Southern California and he says the at lasts him a week of driving to and from work and he lives about 15 miles each way to work. Hopefully that helps a little?
robbobster@reddit
Because you have a tiny amount of fuel
Interesting-Lynx-989@reddit
A slow leak? When did you notice the gas running out so quickly?