Engine Efficiency #3

The third and perhaps the most important efficiency related to engine performance and affecting overall engine output is volumetric efficiency. This is essentially a measure of how easily the engine breathes air in and out. The more air that can be moved into the engine, the more oxygen there will be to mix with more fuel. This creates a more powerful combustion event whenever more power is needed. The power is in the fuel. If you can burn more fuel you can create more power. The actual rating of volumetric efficiency is the measurement of air that actually makes it into the cylinder while the intake valve is open, and the piston is moving down, expressed as a percentage of the theoretical potential volume of the cylinder.

To understand volumetric efficiency it must first be understood that the piston moving down on the intake stroke, with the intake valve open, only creates a negative pressure within the cylinder; it does not suck the air in as you might believe. Once negative pressure, or vacuum, is created in the cylinder, a greater force can push the air into the cylinder. That force that is atmospheric pressure. This is the primary reason that if you drive your car over a high mountain pass, where atmospheric pressure is low, the car always seems to have less power than it does when you are driving around town. Oxygen density at high elevation is also diminished. Sorry, Denver and Salt Lake, but cars are always faster in Los Angeles or Houston.

So if atmospheric pressure pushes the air into the cylinders, it will have to push past obstacles that are in the intake manifold, to get as much air in as possible before the intake valve closes. Not too many engines can get a full dose of air into the cylinder, but the more air that can get in there, the greater the volumetric efficiency.

Equally important as breathing air in is the ability of the engine to easily push the exhaust out. If all of the exhaust is not evacuated from the cylinder then it will displace some of the incoming oxygen. A well designed exhaust system will not only allow easy removal of exhaust gases from the combustion chamber but it can actually aid in drawing the air/fuel mixture into the cylinder. After the piston moves to the top to push exhaust out of the cylinder, and before the exhaust valve closes completely, the intake valve will start to open. The air/fuel mixture will then begin to move into the combustion chamber. Ideally this burst of air from the opening intake valve will help to move the last bit of exhaust out of the combustion chamber. This is a condition known as scavenging, and the better the scavenging the more the inert, exhaust gasses can be removed and the more space there will be for the fresh air/fuel mixture.

Exhaust manifold with tuned
ports.

Other than more precise fuel control, improvements in volumetric efficiency represent the biggest difference between old engine designs and those found in the modern day automobile. Better intake manifold and exhaust manifold designs help the air to flow in and out much more effectively. These manifolds use what is called tuned ports in order to make this happen. A tuned port intake manifold is designed so that all of the tubes or passages that carry intake air to ports in the cylinder head are exactly the same length. The length will also be designed according to the way pressure waves in the manifold resonate back and forth as intake valves open and close. These tuned ports take advantage of a phenomenon known as Hemholtz resonance.

As the air is being pushed into the engine through one of the passages in the intake manifold, it will suddenly stop every time the intake valve at the end of that runner slams shut. The momentum of this air will actually cause the air to reverse direction as it now kind of bounces off the closed intake valve. This pressure wave will move back into the plenum where is serves to help push air into the other runners in the manifold. If the ports are all the same length, then just when the intake valve in the first port opens again, another pressure wave coming from another port in the manifold will be timed just right to help push the next charge of air through the open intake valve into the combustion chamber. This is where that scavenging effect comes into play.

A dramatic example of an engine with a tuned port intake manifold.

Because Hemholtz resonance only occurs at specific engine speeds and loads, many engines also have what is called a variable length intake manifold (VLIM). This is a manifold that can change the length of the intake runners while the engine is running, in order maximize air flow for various operating conditions. At low speeds a longer narrower intake helps to increase the velocity of the incoming air, this increased velocity helps to fill the cylinder with air when the engine is running slowly, and the negative pressure in the cylinder doesn't build as quickly. This gives better throttle response off the line because of the increased torque that can be provided.

The inside of a variable intake manifold. Notice the butterfly
valves that can close to redirect intake air to other passages.

At high engine speeds a series of valves within the intake manifold will simultaneously switch the intake air to a much short runner that is wider. At high speeds the negative pressure in the cylinder builds quickly and in order to fill the cylinder we just need a short, wide path for the intake air. Race cars and other high performance vehicles have very short wide intake runners in the manifold because they are meant to run almost exclusively at high speeds.

Another very significant improvement in engine design that increases volumetric efficiency is the size and number of valves. Since the valves are the gateways in and out of the combustion chamber this of course makes sense. In the old days the combustion chamber had one intake valve and one exhaust valve. These valves were mounted in the cylinder head right next to each other, facing the top of the piston. In the old old old days they were mounted in the block but we won’t go back that far. These valves and the ports that they seal, can be made bigger which allows more air in and out. The problem is that they can only be made so big before the ports start to touch in the center of the combustion chamber. In order to provide even more flow, extra valves are added to the cylinder.

A newer valve arrangement referred to as a pent-roof hemi.
Intake and exhaust valves are set opposite of each other. The
spark plug hole being right in the middle of the combustion
chamber also provides benefits.

An old style wedge combustion chamber. The air does not flow
in and out efficeintly, and there is no room to make the valves any bigger.

Some manufacturers started building engines with two intake valve and one exhaust valve, or two intake valves and two exhaust valves. Some even made engines with three intake valves and two exhaust valves. In order to fit all of these valves in the combustion chamber the arrangement had to be changed. Instead of the valves being arranged next to each other, facing the same direction in the combustion chamber, the valves are mounted on opposite sides of the combustion chamber with the valve faces being angled towards each other. This angled arrangement also increases volumetric efficiency because it provides more of a straight path for the air, through the combustion chamber.

All of these valves crammed into the cylinder head would be difficult to operate with a cam-in-block design that was the standard. For this reason and others related to mechanical efficiency, the cam was moved out of the block and put in the top of the head. In some instances two cams are used to allow the valves to be bigger and angled more towards each other in the combustion chamber. These designs that use two cams in each head are referred to as dual overhead cam, and they are used on all of the most modern high-performance engines. A DOHC engine with a straight cylinder arrangement has two cams, an engine with a V arrangement, or a boxer engine with a flat arrangement has 4 cams.

Cam timing or phasing, and systems that can manipulate this during engine operation, have become a major contributor to increased volumetric efficiency. One of the challenges to making an engine operate efficiently and return good fuel economy, while maximizing power, and burning the fuel as cleanly as possible, is the fact that the engines must operate under a wide range of speeds and loads. An engine can very easily be made to run well at a specific load or RPM range. This is why stationary engines used in industrial equipment such as generators and pumps are usually among the most efficient. They really only operate at one speed and under a very similar load condition each time they are used.

This cam sprocket has five vanes that can move when
acted upon by pressurized oil to change the phasing
between the hub of the sprocket and the teeth

Changing the cam timing will change the timing of the opening and closing of the intake and exhaust valves. Considering that atmospheric pressure is ultimately responsible for pushing the air into an engine, in order to maximize volumetric efficiency at high RPMs, the intake valves must open sooner than they would at low RPMs. This can be done by changing the cam phase. The cam is essentially rotated a few degrees one way or the other in accordance to where the crankshaft is in its normal rotation. This feature is usually referred to as variable cam timing. Ford calls there system TiVCT, Toyota calls their system VVTi, Honda calls their system iVTEC, and so on (What is the deal with the lower case “i” anyway; marketing people everywhere like using it). All of these systems do essentially the same thing. The VTEC system from Honda also incorporates a system that can change how much a valve opens. This doesn’t necessarily change cam phasing but it does cause a sizable increase in volumetric efficiency.

The most fun and perhaps most dramatic way to increase volumetric efficiency is through forced induction. Using a device such as a turbocharger or a supercharger, volumetric efficiency can be literally pushed to over 100%. In a naturally aspirated engine some form of vacuum nearly always exists in the intake manifold and atmospheric pressure rushes in to fill the void. In an engine that uses forced induction the intake manifold is pressurized to anywhere from just a few psi to a few dozen psi. This causes even more air or oxygen to move into the cylinder which allows the engine to burn even more fuel. This might seem like it would cause a decrease in fuel economy and in some extreme applications it does. In reality however, it allows a vehicle to use a much smaller more fuel efficient engine because the forced induction can make the engine more powerful only when more power is need such as during acceleration or passing. The rest of the time all that extra power is not needed. On a normal flat road a Geo Metro can go 65 mph just as easily as a Corvette.

A turbo charger is just an air compressor that pushes air
into the intake manifold.

Turbochargers and superchargers have a drawback in that they increase the load on the engine. Superchargers affect the mechanical resistance that the engine has to deal with because they are driven by a belt off of the crankshaft. Turbochargers are driven by the exiting exhaust gases in the exhaust pipe. This makes it more difficult for exhaust to leave the engine. Both of these drawbacks are minor compared to what is gained in the overall breathability of the induction system.

So what does all of this have to do with engine design that was referenced in the first efficiency article? An engine that is to be used in a mid-size sedan may be the same engine that is used in a mid-size SUV. Because the SUV weighs more or because it might have to tow a trailer once in a while, the way the engine reacts under these different situations is going to make a difference in the overall drivability of the vehicle. The larger vehicle will need more torque at lower RPM than the smaller vehicle. Changing the arrangement of the intake manifold runners, or the way the variable cam timing functions will change the way the engine responds. The engine in the sedan may need to rev higher so things that cause internal resistance affecting mechanical efficiency may need to be considered.

The one thing that is constant is that the engines that perform the best are the ones that rate well for mechanical efficiency, thermal efficiency, and volumetric efficiency. This doesn’t mean that an engine with good ratings in all three of these categories is going to have the highest output; it may get the best fuel economy or perhaps the lowest emissions instead. Ideally it would have some combination of the three. Beyond gas mileage, power, and emissions, what else matters?

Engine Efficiency #2

The next efficiency that has an effect on the way an engine performs is thermal efficiency. As you can imagine this has something to do with heat, that is to say heat not temperature. In case you are not quite clear on this subject, heat is a reference to one of the basic forms of energy, and we typically measure this in Joules or British Thermal Units (BTU). Temperature is only a measure of the intensity of heat energy and we measure this in degrees Celsius or Fahrenheit depending on your unit persuasion.

One joule of heat is equal to the amount of heat given off by the human body at rest over a period of about 15 seconds. The temperature of the human body is 37° C, but if you were to take that 1 Joule and spread it out over the size of a medium sized living room, the intensity of the one Joule of heat would drop significantly so that the temperature of that room would be something very cold.

Gasoline is burned in the engine in a combustion process that converts the chemical energy of the gasoline into very concentrated heat energy. This concentration of heat causes a very rapid expansion of the compressed air in the engine’s cylinders. This expansion of air acts against the piston, pushing it down in the cylinder, which causes the crankshaft to turn. The more accurately the fuel and air are mixed, and the more precise the combustion process, the more efficient the engine will be.

The amount of energy that comes from the fuel that can be turned into force to move the piston down in the cylinder, rather than just turned into heat that will eventually be lost, the more thermally efficient the engine is said to be. Overall, internal combustion engines are very thermally inefficient because most of the energy in any engine is actually turned into heat and lost. Considering that super heating the air to create the expansion necessary to push the pistons, this excessive heat and the loss thereof is not really a surprise, because the heat cannot all be directed toward moving the piston. About half of the lost heat actually goes out the tailpipe, and the other half of the heat goes out through the cooling system and radiator.

The average gasoline engine has a thermal efficiency of only about 20%. This means that only 20% of the heat energy from combustion gets turned into work that moves the piston. This number is pretty low but it is much better than it used to be and will probably get better with time, however, most engineers theorize that that gasoline engine thermal efficiency can probably never get any better than about 35 or 40% due to the constraints of the laws of physics. A diesel engine has greater thermal efficiency than a gasoline engine which is the reason that diesels get better fuel economy. A diesel’s thermal efficiency can be as high as 30% for diesel engines found in cars and trucks and around 40% in many industrial equipment applications. Although this is an improvement over the efficiency of the gasoline engine it is still very low.

Diesel engines have higher thermal efficiency because they can operate with a much higher compression ratio than a gasoline engines. This is because the fuel is injected into a diesel engine just before the piston is at the top of the compression stroke. In most gasoline engines the fuel is injected onto the back of the intake valve and drawn into the cylinder on the intake stroke. The fuel then gets compressed with the air as the piston moves up in the cylinder. As this piston is moving up it is compressing the air which concentrates the heat energy in cylinder. When this heat becomes concentrated under compression, the intensity of the heat goes up. This increased intensity, or temperature, can ignite the fuel before the appropriate time arrives which will cause engine knocking. This is a terrible condition that causes the engine output to go down, and can potentially damage engine internals.

Direct injection has an injector that sprays fuel directly
 into the combustion chamber

Many engine manufacturers are building more and more direct injection gasoline engines. These engines inject the fuel in a very similar many to the way diesels inject fuel. This gives these gas engines greater thermal efficiency because they can run well with higher compression ratios. The compression ratio cannot be raised to high however, because the higher pressure that results causes a loss in the mechanical efficiency of the engine, not to mention the fact that the engine must be built to be more robust in order to withstand the higher pressure.

Next up, volumetric efficiency.

Engine Efficiency #1

Many things go into the design of an engine. Engineers must consider what kind of vehicle the engine will be used in, and this means everything from, how heavy the car will be, how many people it will haul, how much stuff it will haul, what will the overall volume of the vehicle be, and so on. Usually they will try and apply one engine to as many different vehicle platforms as possible in order to make the money spent on development go farther. This is why the V6 engine found in the Lexus ES350 bears a striking resemblance to the engine found in the Toyota Sienna, or the engine in the Pontiac Solstice seems just like the engine in the Chevy Cobalt.

When engineers adapt the same engine to multiple platforms they often make a few changes to the power plant that make it more suited to the platform. These changes affect the output of the engine because they usually change one of three efficiencies that ultimately determine how that engine will perform. These efficiencies are volumetric efficiency, mechanical efficiency, and thermal efficiency. These three efficiencies will be explained in time but for now let’s start with what might be the easiest to understand, and that would be mechanical efficiency.

Mechanical efficiency refers to how much energy the engine wastes because of the internal friction that is ever present. This friction loss is constant over the entire operating range of the engine. Metal parts rubbing together are going to cause friction that will of course cause resistance to the engine turning. Energy of course cannot be created nor destroyed; it can only be changed into something else. That something else in this case is heat. Anytime energy is lost to inefficiency in anything mechanical it is usually lost as heat. This heat from friction inside the engine is not the thing that makes the engine get as hot as it does, most of that heat comes from another source that we will discuss later.

In order to make the engine more mechanically efficient, friction must be reduced. Not only does reducing friction make the engine more efficient, it also makes the engine last much longer because friction and heat destroy all things mechanical. Obviously, the one thing that reduces friction inside the engine more than anything else is plain old motor oil. Everyone knows that without oil the engine would not last long and would seize up into one hot flaming chunk of cast iron and aluminum. Of course many people will still blow their engines up because they will forget to check the oil or something like that, even though they should know better. In the old days the oil was just about the only thing used to reduce friction and increase mechanical efficiency.

An old push-rod valve train.

Another thing that has been used to reduce friction on modern engines is more efficient valve train designs. The valve train begins with the camshaft. This shaft uses teardrop shaped lobes that spin on the shaft to push on some kind of a follower, or rod, or lifter, in order to open a valve. The valves allow the air into the cylinder, and let the exhaust out. On older less efficient engines the valve train was actually more complex and used more moving parts to transmit this force from the cam lobes to the valve itself. Every time another device is added for transmitting force, friction will be present.

Most manufacturers use what is called an “overhead cam” design in the valve trains of their engines. This places the camshaft, or camshafts, on top of or right next to the valves, instead of being in an area down near the crankshaft, alongside the cylinders. Placing the camshaft above the valves means the force travels a shorter distant from the cam to the valves, so less energy is lost to friction. Not all modern engines use this design, but most do and the few left out there that don’t, are likely holding on to the old designs because of the expense associated with R&D of new engine architecture. The overhead cam design also helps to increase volumetric efficiency which we will discuss later.

The mechanical efficiency is further increased by using rollers against the cam instead of just a regular lifter or rocker, which pretty much rubs against the cam. Rollers of course, roll instead of rub, and the rollers can use tiny roller bearings within themselves to eliminate friction even more. These rollers can be used on any kind of engine no matter where the camshaft is located.

A modern over-head cam design.

Modern engines employ many more things to further reduce friction and increase mechanical efficiency. Manufacturing and machining processes have gone a long way to reduce friction. More exact tolerances within the engine help oil to work more effectively. Parts that fit together the way they should will not bind in a way that increases friction, but will fit together well enough to not be constantly pounding each other apart.

While not always internal to the engine, better design of engine accessories and things that are driven by belts from the engine help to increase the mechanical efficiency. Many of the accessories on the engine that used to be belt driven are being eliminated by the use of more electrical and electronic devices. Smog pumps have disappeared, power steering pumps are being eliminated, and even A/C compressors on some vehicles are no longer driven directly by a belt or by the engine. All of this relates to improved mechanical efficiency. If you aren’t using power to power your peripherals under the hood, then that means there will be more power going to the wheels.

Next time we will discuss thermal efficiency.

Good Explosions

Tiny explosions occur inside the engine and that’s what makes it go. Squirt some gas into the engine at just the right time, light it off, and you’re ready to go. This is true enough but the best way to describe the combustion that takes place inside an engine is as a process of energy conversion. Convert energy from a form that is cheap, portable and easy to store, into a form that will move us down the road. That is what the combustion process is all about.

A few simple things are needed to make this energy conversion take place smoothly: spark, fuel, and compression. That’s it; nothing else is required, except for maybe the proper timing of these three things. All of these must happen at the right time, or at least close to the right time and the engine will run. In order to have compression, the intake and exhaust valves must be closed, and the piston must be moving in an upward direction within the cylinder. This is easy enough, what about spark and fuel?

Fuel

The fuel is where the energy is. This energy is in a chemical form and in order to make this fuel propel the vehicle down the road it must be converted into heat energy. Over the years the fuel distribution mechanism has evolved, and in the process has grown more and more efficient. For decades the fuel going into the engine was blended with the intake air stream in the carburetor. These old, inefficient devices were last found on new cars in the early 90’s, since that time all cars sold have had some form of a fuel injection system. The carburetors use what’s called a venture to create a low pressure area that relies on atmospheric pressure to push the fuel into the intake manifold where it vaporizes as it gets sucked into the cylinders. This is very inaccurate and leads to poor fuel economy, dirty exhaust emissions, and less power output.

Fuel injection systems will either spray the fuel into the intake onto the back of the intake valves, or spray the fuel directly into the combustion chamber. This is very accurate and each individual cylinder will get the exact amount of fuel that it will need to make the most of the capacity of the cylinder and the amount of energy that is in the fuel.

When the air and fuel are mixed, and the mixture has entered the combustion chamber, both the intake valve and the exhaust valve will be closed and the piston will move be moving up in the cylinder. The piston moving up will compress the air fuel mixture and squeeze it into a very small space at a ratio of about 10:1. Squeezing the mixture like this concentrates the oxygen in the fuel and the heat in the cylinder. Both of these things help to make the combustion much more powerful and the consumption of the fuel much more thorough.

When the air/fuel mixture is fully compressed a spark will be fired to the spark plug where it jumps the air gap between the two electrodes of the plug. This spark introduces a small source of heat that lights the air/fuel mixture. When the air/fuel mixture burns it causes a tremendous increase in temperature, and when temperature goes up, pressure goes up. As this pressure wave propagates within the combustion chamber, the piston must be in the right position to take the brunt of this expanding force. The piston takes the force of this expansion and moves down in the cylinder exerting tremendous force on the connecting rod, which connects the piston to the crankshaft. The crankshaft turns the reciprocating motion of the piston to the rotational motion that goes to the wheels.

Much is happening within the engine and considering how fast all of this takes place, it’s a wonder that the engine runs as well as it does. Not only does it run well and produce gobs of power but it can do it for hours on end, day in and day out with very little trouble.

Spark

In the old days the spark would originate in the ignition coil which essentially works like an electrical transformer. The coil takes a small amount of voltage with a high amount of current, and produces a high amount of voltage with a small amount of amperage. This spark is produced in accordance with the physical position of the pistons in the cylinders. When a piston is on the compression stroke and nearing the top of the run, on older engines, the coil would fire a spark to the distributor which would then send the spark to the appropriate cylinder at the appropriate time. The distributor was mechanically timed to the crankshaft and the camshaft so that the rotor that was spinning in the distributor would be lined up with the spark plug in the cylinder that had a piston nearing the top of the cylinder.

On the most modern ignition systems found on today’s engines, each cylinder has its very own coil. No mechanical connection is needed between the engine and the coil controls. A computer looks at piston position via crankshaft and camshaft position sensors, and when the time is right it will fire each individual coil for each cylinder. This is extremely accurate and very efficient. This way of firing the spark requires fewer moving parts, and fewer parts in total. This system allows the computer complete timing control. Eliminating moving parts and turning all control over to the computer makes the engine more efficient.

In order to have good, strong combustion, the spark that lights off the air fuel mixture must be introduced at different times depending on how the engine is operating. The amount of time required for the air/fuel mixture to burn is usually about the same no matter how the engine is running. Combustion occurs very quickly, so much so that it seems like an explosion, but in reality it is a very controlled process. In order for the piston to be in the right position to accept the rapidly expanding air, the spark must be introduced at just the right time.

On nearly all engines the spark must hit the air gap of the spark plug before the piston is actually all the way at the top of the cylinder. When the engine is running at high RPM’s the spark must be introduced even sooner because it will take just as much time for the air/fuel mixture to burn. This early timing of the spark is referred to as timing advance. The faster the engine is running the more advance is needed. This timing must be precise in order to maximize power output and efficiency. This early introduction of the spark is measured in degrees of crank shaft rotation before the piston is at the very top of the cylinder. When the piston is at the top of the cylinder it is said to be at top-dead-center or TDC.

Timing Advance

If the spark is introduced too late, then by the time the air/fuel mixture burns thoroughly, the piston will be so far past top-dead-center that the expansion of the air will not exert as much force on the top of the piston. If the spark is introduced too early then the combustion process will push on the piston when it is still in a position before TDC, this not only does not produce very much power but it can also be very damaging to the engine. The piston essentially slams into a rapidly burning and expanding air/fuel mixture. When this happens it is known as knocking or pinging. This knocking usually produces a sound deep in the engine that sounds like a rattle. This is a very bad thing, but usually only happens when something within the engine control systems is not working properly. Knocking can also be a problem if the fuel that is used in the combustion process has too low of an octane rating.

The ideal position for the piston to accept the power of the combustion in this example is 23° after TDC. At 1200
RPM the spark must fire at 18° BTDC and at 3600 RPM the spark must fire at 40° BTDC.

In order to make sure that spark timing stays exactly where it needs to be for the varying engine operation, a computer receives information from several different sensors. A cam sensor and a crank sensor look at piston position, and engine speed. A throttle position sensor looks at throttle position to see what the driver wants the engine to do. A coolant temp sensor looks at how hot or cold the engine is because this too has an effect. The computer can even look at a sensor called a knock sensor to see if the combustion process is happening to soon. This early combustion is the engine knocking that was explained above.

When the knock sensor detects engine knock, the circuits in the engine control computer that adjust ignition timing will back off the timing of the spark so that no engine damage will occur. This means that the spark will be fired at the spark plug closer to TDC. The ability of the computer to rapidly adjust this timing advance is a drastic improvement over the way timing advance used to work. On old engines, timing could never be advanced as much as would be considered ideal, because the mechanisms that controlled timing advance where crude mechanical devices that were slow to react and imprecise.

Burn It Good

Despite the fact that combustion controls are far more efficient then they used to be, the gasoline powered internal combustion engine is still only about 25% percent efficient on average. This is much better than the 15% efficiency that was common in the old days. Most likely the internal combustion engine will continue to become more and more efficient but the likelihood that it could become as efficient as an electric motor is not very high. Diesel engines are more efficient than gasoline engines but they still waste a tremendous amount of energy compared to electric motors. As long as the internal combustion engine keeps getting better and better, and the cost of electric cars stays high, we will keep on driving the cars that we know best.

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.

The Best Cars Ever: Toyota Corolla

Another Entry in the Ongoing List of Amazing Cars

1968 Toyota Corolla

In 1968 Toyota introduced a new car to the U.S. market that like other cars in the Toyota line up used a version of the word “crown” for its name. Toyota first came to the United States in 1958 and the first sedan they had to offer the American market was called the Crown. This car didn’t sell very well and after a few years was discontinued. The Next sedan released in the U.S. was the Corona. This is the Latin word for crown. This car sold very well and in 1968 Toyota introduced the Corolla which derives its name from the Latin word for small crown. The Corolla was essentially a smaller version of the popular Crown.



2000 Toyota Corolla

 Today the Corolla is the longest running “import” sedan sold in the United States (the longest running model from an import company sold in the U.S. is the Toyota Land Cruiser which came to the U.S. on the first boat from Japan when Toyota arrived on our shores in 1958). Globally the Corolla has sold more units than any other car ever, including the old Volkswagen Bug. Estimates show that a Corolla is sold somewhere in the world every 40 seconds. Nearly 40 million units have been sold world wide since it was first introduced.

The Corolla has been used as a basis for many different cars. The Geo/Chevy Prizm, the Chevy Nova from the 80’s, the Toyota Matrix, the Pontiac Vibe, and the Scion xD have all come from the Corolla. The Corolla has been sold in rear wheel drive, front wheel drive, and 4 wheel drive configurations. Over the year there were 4 door sedans, 2 door coupes, and 3 and 5 door hatchbacks, there was even a few different station wagons. The only configuration that has not changed over the years is that the engine has always had 4 cylinders. The current Corolla is the 10^th generation and is always found in list of the top 10 best selling cars in the U.S.

Popularity and manufacturing longevity do not make this car great; the thing that really makes it great is that it is so darned reliable. Not very many cars come close to matching the reliability of the Corolla, no other model in the Toyota lineup can claim to be better built than the Corolla. Anyone who has ever owned one of these cars knows exactly how it is, and probably has a story about how amazingly trusty their Corolla was or is. Some of them become very ugly and beat up but they still run well and they still drive solidly down the road. It’s one thing to have a car go hundreds of thousands of miles with the original engine and transmission, but it’s another thing to be able to remain a solid ride despite some rust, dents, and faded paint.

The Corolla is not offensive to look at, but it has never been anything special in its form. The car has never been slow compared to other cars in its class, but it has never been a sports car either, although there have been some models that were rather sporty. Back in the late eighties there was a rear wheel drive coupe version referred to as the GT-S that was sold for a few years despite the fact that all other models were switched to a front wheel drive layout several years earlier. These old GT-S coupes are still highly sought after by some Toyota enthusiasts. There was also a model referred to as the FX-16 that was a sporty hot hatch, which is interesting because this was back in the days before there was really such a thing as a hot hatch.


1986 Corolla GT-S



1987 Corolla FX16

For most people out there things such as looks or sportiness are not the least bit important when their car is broken down on the side of the road. The car that doesn’t leave you stranded is the car that you have a hard time learning to hate. People who don’t like the Corolla will always comment on their dislike of superficial things such as looks or they will claim that the car is not fun to drive. What car in the same class as the Corolla can be classified as a driver's car? Is the Corolla some what plain? Perhaps but it is at least as good if not better than any other car in it's class when it comes to aesthetics? Also, there is nothing wrong with viewing a car as an appliance, or a simple tool of transportation. To most people, that's all a car is anyway.

2011 Corolla

Two words that sum up the reason for calling the Corolla one of the greatest cars ever are, “time tested.” After these many decades the Corolla has proven itself to be reliable, solid, safe, and efficient transportation, getting people from point A to point B without any fuss. This is the kind of reputation that many auto manufacturers wish they had for their transportation offerings, such status cannot be purchased by any corporation. The Corolla is solidly one of the best cars ever… no pun intended. 

The Latest Line on Brake Linings

For all of you that are adventurous enough to do a little work on your own car. One of the things that you might have tried, or may be willing to try is replacing your own brake pads. In many cases the hardest part of replacing your brake pads comes during that moment that you are standing at the parts counter at your friendly neighborhood auto parts store. After they look up your parts based on make and model, they will usually ask you what kind of pads you prefer.

You might answer this question by telling them that you want the new kind of pads. Of course this goes without saying. What they are referring to is the composition of the friction material used in the pad. Not all pads are equal, and just because they fit on your car doesn’t mean that they are the best thing for it. Your choices are usually semi-metallic, organic, or ceramic, but there are a few more choices for some makes and models.

Semi-metallic pads are the cheapest, and last a long time. They are composed of a material that contains ground up bits of metal. Semi-metallic pads used to be the most commonly used pads but they have some drawbacks. The biggest drawback is that semi-metallic pads are much more likely than the others to develop a squealing noise. This might be just a minor chirp as the wheels come to a stop or it could be a major howl that emanates the instant the brake pedal is touched. Either way it can be very annoying. Semi-metallic pads are also harder on brake rotors and have more of a tendency to wear the rotors down.

Organic pads are made from materials that are usually carbon based. Sometimes they are referred to as synthetic pads. They are a very common pad of choice for smaller vehicles because of they way they wear. Organic pads used to use asbestos as a primary component in the friction material. Asbestos was very good at withstanding the heat, and providing nice smooth braking feel, but it is a known carcinogen and was fazed out decades ago.

A common component in organic brake pads today is Kevlar. Organic pads are good because they are very quiet compared to semi-metallics and they are easier on the rotors. The biggest problem with organic pads is that they wear much faster than any of the others. Sometimes organic pads can be worn out in as little as 20,000 miles. They do not take abuse very well. They also produce a fair amount of break dust that will build up on your bling rims.

The third type of pad and the one that might be the best is the ceramic brake pad. These pads are composed of a material that is made up of ceramic fibers, copper, and bonding agents. These pads last a long time, dissipate heat very well, and don’t produce very much dust that accumulates on the wheels. They are also very quiet, or at least it would seem so to humans. The vibration of the pads in the calipers that becomes the noise that we hear, vibrates at a frequency that human ears cannot hear. If the noise can’t be heard, is it really making a noise? Do the dogs in the neighborhood appreciate all of this noise?

The biggest problem with ceramic pads is that they are expensive. Often times they will be 3 times more expensive than semi-metallic or organic pads. A normal set of semi-metallic pads might run $15 to $20, where as a set of ceramic pads for the same vehicle might be $50 or $60. Considering how much better ceramic pads are, the cost should not be prohibitive. Remember we are talking about a very important system on your vehicle. The difference between $15 and $50 is not the same as the difference between $100 and $300 dollars so spending three times more on brake pads is not as painful on the wallet.

The other things that you usually get with the more expensive pads are things such as new shims, and new anti-rattle clips and springs. Replacing this hardware is a good idea even though it may not be totally necessary. Both of these things will help to keep the pads quiet.

Ceramic brake pads can be hard on brake rotors but considering brake rotors are getting much cheaper to replace, the amount that pads wear down the rotors, doesn’t matter as much anyway.

Disc brake quiet applied to the back of the pad and not to the friction
surface on the bottom.

Another type of pad that is out there but maybe not so common is the full metallic type. Metallic pads are made from pulverized metal particles formed into a block and attached to a steel plate. These are very tough but they are only effective when the brakes get hot and they make a tremendous amount of noise. These are probably best suited to using on a race car rather then on the family minivan (not that you could even get any that would fit your minivan).

If you find yourself in the parts store buying brake pads and they ask you which ones you want. Go for the ceramic first, the organic second, and if neither one of those are available don’t bother with the semi-metallic and just go to another store. When they try to sell you the small packets of goo that goes on the pads, it’s not a bad idea. Just don’t put the goo on the friction surface of the pad, it’s supposed to go on the steel backing plate of the pad. This helps the pads to keep from vibrating in the calipers which causes a squealing sound. Never be afraid to spend a little extra when doing your brakes, in the end it will likely be worth it.