The CNG Project

Introduction to a New Ongoing Series

After months of planning and parts sourcing I am finally at the point where I am ready to begin a new project. This will be the conversion of my Lexus to CNG.  As you may or may not know, CNG stands for compressed natural gas. When I am done with this project I will be able to run the engine on either gasoline or CNG. The engine will be able to switch back and forth between the two whenever necessary.

The car being converted.

The reasons for doing this conversion are many. Some of these things are related to the advantages that CNG provides over gasoline; I have written on this subject before. On the practical side, CNG at the local station where I live goes for about $1.25 per gallon compared to the September 2011 price of gasoline at $3.52 per gallon. Obviously CNG is cheaper but more than that the price is also stable so a year from now it will be about the same, and if some crack pot dictator in the Middle East goes on a terror the price of natural gas will probably still be about the same.

The cost of the conversion is obviously steep if it is to be done correctly. Many people out there are doing conversions incorrectly and bragging that they can do it for between $1000 and $1500 dollars for the parts, and then mix in some free labor performed by themselves and they think they are good to go. The problem is they are using inferior systems with inferior parts. They will say that it doesn’t matter as long as the system works. The problem is that they usually end up with a system that will make their engine run but it will never run right. They will have problems with check engine lights coming on all of time, or the vehicle will lack power so badly that it’s almost not even drivable.

CNG fuel regulator, reduces the pressure from
3600 psi before sending it to the injectors.

A good conversion should not compromise performance in any way, shape, or form. Engine power should be about the same whether running on gasoline or CNG. Fuel economy should be the same on both fuels as well, and you should never have to deal with a check engine light coming on when the vehicle runs on CNG. The check engine light illuminating is an indication that something in the way the engine is running is not right. A quality CNG kit and conversion should allow the engine to run exactly as the engineers intended except on natural gas instead of gasoline. Some of the fly-by-night companies out there that are selling bogus CNG hardware will actually tell you that you should buy a cheap code reader in order to erase codes as they pop up.

Another thing that is important to know about CNG conversion is that these systems run at very high pressure, up to 3600 psi. In order to do the conversion in a way that is safe some training is required. Certain safety standards exist in order to keep these systems safe and it is important that these standards are followed closely by the individual performing the retrofit. I am a certified CNG fuel system inspector so I know the standard and obviously I intend to adhere strictly to the code.

Numbers

So what kind of cost savings will I see and how long will it take to recoup my costs? To fill the CNG tank on my car it will take about $9.00. This fill will give me about 180 miles before the tank must be filled again. This means that I will be spending about $.04 per mile. To run the car on gasoline it costs about $.13 per mile. If I drive the car 15,000 miles per year which is fairly average for the run of the mill car in the U.S. and if gas prices stay the same, I will recoup my cost in about 2.8 years. If gas goes back up to $4.15 per gallon like it was here back in 2008, I will recover the cost in about two years. If I drive more miles per year I will recover the cost sooner, and if gas goes to something never seen before, then there is no telling how fast I will recover the cost.

Saving money on gas is only one of the reasons that I am doing this. I am also doing this for purposes related to research and some things that I have going on related to my occupation as a college auto instructor. The last reason is I am doing this for fun. Most car guys spend money building some kind of custom 4X4 or restoring classic cars and such. I am kind of a geek as well as a car guy, so I am spending time and money building an alternative fuel vehicle.

The Hardware

The car is a 2007 Lexus ES300. This is kind of just a regular midsize sedan with 3 liter V6. The reason that I chose this car is because I got a good deal on it. I was looking for a midsize Honda or Toyota sedan to do this conversion. Since Lexus is built by Toyota the car that I am using will be just fine. The ES300 is actually just a fancy Camry so I pretty much got what I originally set out to get. Being a sedan and having a trunk is important because that is where the tank will go. You could really put the tank just about anywhere inside the vehicle that you want. You could even put it on the roof if you really wanted to.

The electronic control unit that runs the CNG system

The CNG fuel system parts come from Technocarb. This is a company out British Columbia Canada. They make several different kits from parts that are of Italian origin. I have friends that are into CNG conversions that have had very good luck with hardware from Technocarb. The kit is a multiport injection setup which is the most effective. A separate injector will feed each individual intake port which makes for more precise air/fuel metering. Some of the cheap junky kits use what is called a fumigation setup. This just floods the entire intake manifold with natural gas and it is not very precise.

CNG injectors. One set of three for each side of the engine.

The kit from Technocarb will require tuning and customization once it is hooked up in the vehicle. This is one of the things that makes the Technocarb setup nice. Software and a laptop computer are required to interface with the CNG computer to dial it in and make the vehicle run nicely. This also makes the Technocarb kit the kind of thing that someone without any knowledge of fuel control systems would not want to install themselves.

The CNG tank is the most expensive part of the conversion. A few different style tanks are available, but some are not practical for use in a normal sedan because they can be too heavy. The market for CNG tanks is also flooded with all sorts of used tanks pulled from wrecked vehicles and other places. Some of the used ones are good and some are not. Every tank has an expiration date on it and once that date passes the expiration date, the tank cannot be used again. Many of these expired tanks are out there on the used tank market. Some of the used tanks might be damaged as well, so buying a used tank is not ideal.

I purchased a new type 3 tank from a company in Calgary, Canada called Dynetek. The type 3 tank is very light because it is made of mostly carbon composite. Besides being very light and durable, the tank is also a 3600 psi tank. Running the system at 3600 psi is ideal because it increases the range of the vehicle. Many of the older used tanks are only 3000 psi tanks. This new tank from Dynetek is also a 20 year tank. That means that I will be able to use it until 2031. Many new tanks are only good for 15 years.

The CNG tank. This tank holds about 7.5 gasoline gallon equivalent.

What Now

Over the next few weeks or months, depending on what happens with my schedule, I will be installing these parts in the vehicle and hooking everything up. As I go through it I will take pictures and make some notes. Periodically I will write a bit about how the project is going and the things that I have learned. Once it is all finished we will know how it all works out, and I intend to test things such as real world fuel economy as well as power output on gasoline compared to power output on CNG. This should be fun and interesting.