NGV FAQ

FREQUENTLY ASKED QUESTIONS ABOUT
NATURAL GAS VEHICLE TECHNOLOGY

I get lots of questions about my CNG powered cars. Here are some of the more common actual questions I have answered so far.

Table of Contents

1. How much do you pay for gas?
2. Where do you fill it up?
3. What  kind of mileage do you get?
4. Isn't driving around with a tank of compressed gas dangerous ?
5. Does the car drive as well as a gasoline powered car?
6. What's the difference between a P30 fill nozzle and a P36 fill nozzle, and what about types 1, 2 and 3?
7. How far can you go on a tank of gas?
8. How much do you have to pay for one of these and where can I get one?
9. Everyone is saying that hydrogen is the fuel of the future. Why not run your car on that?
10. Isn't it smarter to get one of those new hybrid vehicles everyone is talking about?
11. What's the difference between flex fuel, dual fuel and hybrid vehicles?
12. How do you fill up the tank?
13. What are the environmental benefits I keep hearing about?
14. Won't running the engine on natural gas hurt it?
15. Can you use propane from your BBQ grill if you run out of CNG?

How much do you pay for gas?

As of August, 2005  I currently pay about $1.45 per GGE (gallon gas equivalent) at the pump. A GGE is the roughly the same as a gallon of gasoline. The cost per GGE is pretty much the same if I fill up using my refueling appliance at home. The calculations for determining this can be found here

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Where do you fill it up?

Most people who buy NGV cars for personal use do so because there is a gas station that offers CNG nearby. These stations have CNG dispensers that look and operate like a conventional gas pump. These pumps will usually accept credit cards, but some only accept special "key" cards that must be obtained in advance from the party that owns the dispenser.

These are FAST FILL dispensers, where the CNG is stored under high pressure in large tanks waiting to be transferred to your vehicle. The time required to fill the tank is roughly comparable to the fill time required by a conventional gasoline pump. There are two fill pressures currently in general use: 3000PSI and 3600PSI. In order to prevent a vehicle rated for 3000PSI service from connecting to a 3600PSI dispenser, the fill nozzles are keyed. 3000PSI nozzles are usually blue, while 3600PSI nozzles are yellow.

The US department of energy maintains a database of alternative fuel stations, Their alternative fuel station locator can display CNG stations available in a particular area, or plot a trip route showing fill stations along the way. Unfortunately, many of the stations shown are private access only, but you can often call ahead to make special arrangements in a pinch.

The other way to fill up your NGV is with a vehicle refueling appliance, or VRA. These are usually SLOW FILL systems that compress the low pressure natural gas entering the appliance directly into the vehicle. The fill time required varies, but a rate of .4 to 1.5 GGE per hour is typical. The most visible manufacturer of VRA's for home and small business use is Fuelmaker. The PHILL home refueling appliance is now available from Fuelmaker in selected market areas. Honda has partial ownership of Fuelmaker and is now offering the PHILL along with the Honda Civic GX NGV to the consumer market.

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What kind of mileage do you get?

Like they say, your mileage may vary but we have been getting an average of 31 MPG on our 2002 Honda Civic GX. This is about the same as one would expect from a gasoline powered Civic.

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Isn't driving around with a tank of compressed gas dangerous?

On the contrary; I feel safer with a CNG tank than I do carrying around a tank full of gasoline. First of all, natural gas is lighter than air and will therefore dissipate into the atmosphere should a leak develop. Gasoline vapors aren't as well behaved. Also, it's a lot harder to get natural gas to ignite; the temperature at which natural gas spontaneously ignites is 842 degrees F, vs. 572 degrees for gasoline and 446 degrees for diesel. Natural gas cylinders are much thicker and stronger than gasoline or diesel tanks.  Industry standards require them to withstand 11,250 fill cycles, and endure far beyond normal environmental and service damage risks.  Cylinders must even withstand a bonfire test and penetration by a 30 caliber bullet without rupture!

In general, natural gas vehicles have an excellent safety record for two primary reasons: the properties of the fuel itself and the integrity of the natural gas vehicle and its fuel delivery system.

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Does the car drive as well as a gasoline powered car?

That would depend on the car and how it was designed. Natural gas has some performance advantages over gasoline, namely the octane level. The octane rating of a fuel is a measure of how resistant it is to preignition, or "knocking". However, the energy content you get is somewhat less than gasoline. A well designed CNG engine takes advantage of the increased octane level by increasing compression and advancing the spark. This compensates somewhat for the loss of power incurred by the decreased energy content of the fuel. Most vehicles perform adequately, but you will see some decrease in horsepower when compared to the equivalent gasoline powered vehicles. This is also the reason that a "dual fuel" vehicle (i.e. one that can switch between gasoline and CNG) does not perform as well as a dedicated CNG vehicle since the engine can't be completely optimized for natural gas.

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What's the difference between a P30 fill nozzle and a P36 fill nozzle, and what about about types 1, 2 and 3?

Good question. The most common system used  in North America for CNG fueling is the NGV1 standard. The part that goes on the fueling device (i.e. at the end of the hose) is called the NOZZLE. The part that mounts to the vehicle is called the RECEPTACLE. There are two different sizes of both these components; the P30 is for 3000PSI service, and P36 is for 3600PSI service. P36 nozzles are usually yellow, while P30 nozzles are blue. In order to prevent a P36 nozzle from connecting to a P30 receptacle, the P30 receptacle is 1mm larger in diameter at the rear: There are venting (Type-1) and non-venting (type-2 and type-3) nozzles. Type-1 nozzles release pressure built up in the fuel  hose at the nozzle end by operating a manual "fill/vent" valve on the device after refueling is complete. The relieved gas pressure is then diverted to a separate hose leading back to the refueling apparatus to be vented to atmosphere or fed back into the compressor. A type-1 nozzle can also vent directly to atmosphere at the nozzle end, thus precluding the requirement for a separate relief hose. A type-3 nozzle relies on the refueling apparatus to vent the pressure at the supply end. A type-2 nozzle is basically a type-3 nozzle with a separate relief valve fitted to it at the nozzle end, so it operates much like a type-1 nozzle. The type-1 nozzles are usually found in fast-fill applications, while the type-2 and type-3 nozzles are usually found in slow-fill refueling applications.

TYPICAL NGV1 RECEPTACLE

TYPICAL TYPE-1 NGV1 NOZZLE

STAUBLI P30             PARKER P36 TYPICAL TYPE-3 NGV1 NOZZLES

You can plug a P30 nozzle (blue) into a P36 receptacle, but you cannot plug a P36 nozzle (yellow) into a P30 receptacle. The opening in the P36 nozzle will not physically fit over the 25mm rear "collar" of the the P30 receptacle. You can *theoretically*  modify a P30 receptacle to work with a P36 nozzle by removing 1mm of material from  the receptacle  collar with a decent quality metal lathe. Please do not attempt this modification unless you understand the potential consequences!!!

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MORE ANSWERS COMING SOON!!!

QUESTIONS? COMMENTS?

SEND THEM TO:  mailto:holtek@wi.rr.com

This page was last updated on 12/31/2007