Non Circular Gears

When non-circular gears rotate, they can pump fluids because their lobes leave empty volumes within the disk of revolution. A circular gear completely fills its disk of revolution, thus leaving no space for a fluid to enter. As the lobes turn, the hollow volume goes through a revolution as well, carrying along any fluid within. This allows for moving a known amount of fluid per revolution. In this way flow can be easily measured or regulated. Just count or control the number of revolutions and the amount of transferred fluid is known.

Reversible Fans : Clean Radiators Can Save on Gas

Heavy machinery can guzzle gas. A simple idea for cutting back on their thirst is to keep their radiators clean by reversing the cooling fans to blow any obstructing dust and dirt off. Radiators clogged with dirt will require more work from the fans to force the same amount of cooling air through the engine. Fans working harder means more fuel spent to run those fans. The alternative is to operate the engine without sufficient cooling airflow, but the resulting higher temperatures will reduce equipment life and lead to losses in efficiency, which in turn waste fuel.

By running the air intake fans in reverse for a few moments much of the obstructing material can be removed. A simple but great idea for saving on gas!

Get to Know Your Valve Train

In operation, an internal combustion engine, such as the one you likely have in your car, needs to take in fuel and air. After burning them, it has to eject waste gases. It must do this while maintaining a sealed cylinder which can take advantage of the high pressure generated by the combustion. The solution is provided by the valves, which open and close as needed. The valves are the gatekeepers to the kingdom of the engine, controlling what goes in and out when. The valve train is the entire apparatus of rods, cams and springs dedicated to the operation of the valves. Understanding the valve train is absolutely fundamental to knowing how an engine works. This handy video gives a great introduction to the valve train, with nice animated cutaway views.

Next Generation Learning to Save on Gas

This piece tells the story of a high school shop teacher who has his students working on constructing a vehicle that uses only 1.1 GPHM. The pupils will help design the gas saving cars of the future rather than learn how to tune up the old gas guzzlers of yesteryear. I think this sort of education is exactly what our children will benefit from. Youngsters of today will spend almost all their lives in an environment quite unlike the one their parents knew. The children will know a world where gasoline is expensive and therefore you always think twice about using it. Better they start learning how that world works than invest hours studying dinosaur fuel wasting cars of the obsolete happy motoring epoch.

Convert Your Pickup to Diesel - With a Tractor Engine

Here is a fellow who replaced the engine of his pickup with the diesel engine from his tractor. One way to get a more efficient diesel in your vehicle!

Wheel Alignment is Not an Elective Service

Out of alignment wheels will decrease the gas mileage of your vehicle. They will also reduce the handling performance of the car, which makes it less safe to drive. And of course the lifetime of your tires will be shortened resulting in you spending more on replacement tires. When should you have the wheels aligned? Align your wheels after installing new tires or rotating the old ones. Have them aligned after replacing or having work done on the steering or suspension. Also go for an alignment after any collision repairs.

Keep your wheels in good alignment and you will save a percent or two on gas!

Torque vs RPM

On a dynamometer chart you always see the torque and power produced by an engine plotted versus RPM. That shows you how the engine performance depends on speed. The engine speed is related to the vehicle speed but not directly because of the gear ratio in the transmission. Have you ever wondered why the torque curve has a peak? What causes the torque to be lower at low and high RPMs?

First of all, why is there a peak torque? Peak torque occurs when the engine receives the maximum amount of fuel air mixture in the cylinders to burn. The torque is produced by the pressure of the explosion on the pistons. This pressure is transmitted to the wheel rims as rotational force against the road. More cylinder pressure gives more torque, and to get more cylinder pressure you need to burn more fuel. So peak torque is when the cylinders are getting the most fuel with air sufficient to burn it all.

AS the RPM goes above the point of peak torque, torque decreases mainly due to difficulty getting air in and out of the cylinders. Basically the engine can't breathe fast enough to keep up with the pistons. The air will only move around so fast. The maximum external static pressure to drive air into the cylinders for example is one atmosphere. If the pistons begin to move up and down faster than the air can move into the spaces they leave behind then the air fuel charge amount will start to drop. As the exhaust gases are forced into the exhaust manifold faster than they can flow out through it, the back pressure in the manifold rises and rises. This rising back pressure robs output from the engine as it must now divert some effort to fighting it. Also mechanical efficiency drops at high RPM due to generally increased frictional resistance at high relative speeds between moving parts.

Now what happens at lower RPM? First of all, the pistons are now moving slowly. This gives time for heat to flow. During the compression stroke and power stroke at slow piston speeds, there is time for some of the heat in the gas mixture in the cylinder to escape through the cylinder wall. This loss of heat leads to a drop in temperature and pressure. This pressure loss directly reduces torque. Remember that the torque is being generated by the pressure on the pistons. There will always be an imperfect seal around the piston rings and the valves. At low RPM there is time for the pressure to bleed off through leaks. In addition to these factors the timing of the ignition and valve open/closing for normal engines is optimized for midrange RPM. Engines with variable timing systems do not have to suffer low RPM torque losses due to this factor, but the majority of today's engines do not have such systems.

Check Your O2 Sensor

We talked before about oxygen sensors going bad. A bad oxygen sensor will think there is not enough fuel in the air-fuel mixture and add more. The result will be too much fuel for the amount of oxygen and not all of it can be burned. The extra unburned fuel will be wasted with the exhaust. Remember that your engine is an air breather.

This video compares a bad and a good oxygen sensor to show the difference. The two sensors are given time to warm up. Then a rag is wet with brake cleaner. Because the brake cleaner is combustible, the sensor treats it as fuel. The good sensor indicates the presence of fuel (full rich) as long as there is still brake cleaner in the rag. The bad sensor after a short time shows full lean. The bad sensor thinks there is far too much oxygen relative to fuel even though the situation is the opposite. You do not want this to happen in your car!

Check Your Tire Pressure

Try to always keep your tires inflated to the recommended pressure. Under inflated tires will suffer premature wear and need to be replaced sooner. They will degrade the handling (and thus safety) of your vehicle. And of course, they will lower your fuel economy. This video clip from Edmunds shows how you can easily keep an eye on your own tire pressure. The most important lesson? You can't tell by looking if your tire pressure is slightly too low. You have to check the pressure using the right gauge.

NuVinci Continuously Variable Planetary Transmission

The transmission is the connection between the speed of the engine and the speed of the vehicle. Conventional transmissions provide a series of gears. Each gear has a fixed ratio between engine speed and vehicle speed. If you wish to go at a given speed and your transmission has for example five gears the engine has to run at one of five speeds. Each engine is most fuel efficient at exactly one specific RPM. If none of the five speeds is at that RPM, your engine will not be able to drive you at your chosen speed as efficiently as possible.

Continuously variable transmissions provide a range of ratios between engine RPM and driveshaft rotation (vehicle speed). This allows the engine to always run at its most fuel efficient RPM. Changing vehicle speed is accomplished by changing the transmission gearing ratio instead of the engine RPM.



There have been many implementations of continuous variable transmissions using a variety of techniques. Good old Wikipedia has a list of automobiles using them. Although automakers have only really been getting serious about their use in the last five years or so. Fallbrook Technologies has recently been developing a new type : the NuVinci. Watch the video above to see how it works. I think it is an ingenious mechanical system. This is a planetary continuously variable transmission. The name comes from Leonardo da Vinci, who first invented continuously variable transmissions 500 years ago. And Detroit has only seen the value about 5 years ago. Oh well, better late then never.

Turbo-Compounding

We have come to number four in our series. Turbo compounding is a method for recovering otherwise lost energy from the exhaust of a normal internal combustion engine (ICE). The design puts a turbine in the exhaust manifold which collects the kinetic energy (energy of motion) of the escaping exhaust gas. This turbine then transfers the power it generates to the crankshaft. The transfer is usually made by a hydrodynamic linkage, like in a transmission.

There are two basic types of turbines that operate by extracting energy from either the velocity (kinetic energy) of the working fluid or the pressure of the working fluid. In the case of pressure turbines there must be a large pressure drop across the rotor blades. This type is not used in turbo compound engines because the pressure drop restricts exhaust outflow, smothering the engine. Instead of pushing exhaust out against atmospheric pressure, the engine has to push it out against atmospheric pressure plus the turbine pressure drop. Using kinetic turbines avoids this problem.

Note that this is different from a turbocharger. In turbocharged engines there is a turbine powered by the flow of exhaust gases, but instead of adding this power to the driveshaft of the engine directly it is used to run a compressor which pressurizes the intake air. This results in a density boost, filling the cylinders with more air (and thus more oxygen) per charge. Since the ultimate limit on the energy you can get out of the combustion is set by the amount of oxygen present, turbochargers also increase power output. The mechanism is different though.

Turbo compounding allows for more power output given the same fuel input because it captures energy that would otherwise escape as exhaust gas velocity. However, the power per weight ratio is lower due to the turbine. The engine is also bulkier. But it is possible to greatly increase either the power available or the fuel economy or a mixture of both.



Although some World War II era aircraft before the development of turboprops used turbo compounding the technology has not been used by automakers. That is now changing. For example, the Daimler Trucks Detroit Diesel DD15 uses turbo compounding. The video above talks about the turbo compounding at about the 3:10 minute mark. Note there is also a turbocharger on this engine. Once again, turbo compounding and turbocharging are two different methods for recovering energy from the exhaust gas.

Perhaps someday soon car engines will also feature turbo compounding.

Variable Displacement Engines

Here is number three in our series of posts. The displacement of an engine refers to the total volume covered by the piston stroke inside the cylinders. Note that it does not include the heads. This is because the thermodynamic work done by the engine happens when the piston is forced down under the pressure of the hot combustion products.

Variable displacement technologies use mechanisms that can change this active piston swept volume according to the power demanded of the engine. When the engine needs less power the displacement is reduced and when the engine needs more power it is increased. It is more efficient to run a smaller engine at normal power output than to run a big engine at a bare idle. This is because the big engine has to be throttled way back and it suffers heavy frictional losses trying to suck in air. The energy lost while sucking air into the engine and pushing it back out on the intake and exhaust strokes is known as pumping loss.

The conventional way to reduce the displacement is to shut off some of the cylinders. For example, the 2008 Honda Accord V6 three, four or all six cylinders depending on the load. A management computer directs the switchover between different numbers of cylinders in use.

More advanced non-conventional techniques also exist. The Hefley engine controls the displacement by moving the average position of the pistons up and down the cylinder. To be able to do this required a complete redesign of the engine layout.

According to Wikipedia the first variable displacement engine was built over a hundred years ago (although it was a stationary engine). The first try at commercial use in cars was by Cadillac in the 1980s but failed due to mechanical breakdown being too common. Only as recently as 2004 was there mass commercial deployment of this technology. One cannot help but wonder if this fuel saving tech might have been developed and deployed a decade or two earlier if Detroit had made it a priority.

Variable Valve Timing

This is the second in our series of seven fuel economy technologies Detroit could have pursued but did not. Although almost all of the world's automakers have made at least one engine with variable valve timing within the last 10 years, before that time they were rare. Even today the majority of engines have fixed timings.

The video illustrates the idea. Basically, the fuel-air intake valves and the exhaust valves open a certain distance and stay open for a certain time. Also the location in the piston cycle at which they are open is important. At a given RPM, the engine has to open the valves different amounts at different positions for different times to get maximum efficiency. If the valves have fixed timings, the engine will only be at its top efficiency at one narrow RPM band. However, if the valves can modify their timing, the engine can reach high efficiency over a wider band of RPM.

In normal operation, there is a moment near the end of the exhaust stroke when the exhaust valve and the intake valve are both open. Also the exhaust valve stays open a little while into the intake stroke. This time when both valves are open is known as the overlap, and is one of the most important variables to control. At low RPM, the overlap should be low. This is because at low RPM the airflow is fast relative to the engine speed. At high RPM, the engine is moving so fast relative to the air that it is better to open the intake valve early so that the air has a better chance to enter.

The first vehicles with variable valve timing technology were not introduced to the US market by Detroit. Instead Alfa Romeo, Nissan and Honda blazed the trail. One more chance missed by Detroit.

How to Change Your Own Oil Filter

Your car's engine depends on three filters: the oil filter, the air filter and the gasoline or fuel filter. These keep the engine's "lifebloods" of gas, air and oil clean. Dirty clogged oil filters will result in a bigger pressure drop across them, lowering the oil pressure in the engine. If the pressure loss is too great, oil filters are designed with a bypass value that opens and lets unfiltered oil through. Why? Because dirty oil is better than not enough oil. Loss of sufficient oil pressure can destroy the whole engine. The pressure drop across the oil filter goes up with engine RPM. At very high RPM, say around 4000 RPM, the bypass valve will normally be open due to the large pressure drop at this RPM. Dirtier filters have lower RPM thresholds for opening the bypass. Thus with a dirty filter, every time you rev up your engine you may be letting a shot of dirty oil through.

Dirtier oil is more viscous and the particles of debris in it may wear directly against the moving metal in the engine. This increases engine friction, which lowers fuel economy. So clean oil filters can help get better mileage. You can change your own oil filter and save some money. It is really easy. The video shows how. Watch and learn!

The video below has the part about changing the oil filter. The video above is the introduction and also shows how to change your own oil. If you want, go ahead and buy a K&N HP-1010 Oil Filter from Amazon now!

Brickley Engine - Less Friction, Better Mileage

Friction in the engine itself lowers your car's gas mileage. Instead of begin converted to useful work, some of the energy in the fuel is wasted in the form of heat or noise. Mainly heat. The Brickley engine design aims to rearrange the cylinders and crankshaft arms to reduce this friction. A Brickley engine is an internal combustion engine with specially connected pistons that move along paths to a very high tolerance. Because the piston stroke is defined to a couple thousands of an inch, the piston skirts can be eliminated or reduced. So far this engine exists only as a patent. I doubt there are working models. Not to say I doubt they will work, just that there is still no prototype. Apparently the Brickley design can eliminate 35% of the engine friction. This could give a 15% to 20% increase in vehicle mileage.

One other interesting bit of information was a list of components and their contribution to friction in a typical engine. Here is the breakdown of engine friction by part according to Mike Brickley, the engine designer:

Research attributes the following approximate amounts to the various components: crankshaft 18%, connecting rods 15%, accessories 10%, camshaft 15%, piston rings 21%, piston skirts 21%.

Engine Friction Breakdown

Component	Friction
Piston Rings	21%
Piston Skirts	21%
Crankshaft	18%
Camshaft	15%
Connecting Rods	15%
Accessories	10%

Velozeta Six-Stroke Engine

Six stroke engines add another two piston motions to each fuel injection cycle to those of the common four stroke engines. Everyday cars and trucks use four stroke engines. These are called four stroke because for each time that a new shot of fuel is burnt, the pistons sweep up twice and down twice, for a total of 4 sweeps or strokes. The four stroke sequence goes like this:

Intake Stroke

This stroke begins with the piston at the top of the cylinder. The piston moves down, opening up space in the cylinder. As it does so, the valves in the head above open and fuel-air mixture gets sucked into the cylinder.

Compression Stroke

When the piston reaches the bottom of the cylinder, the valves close off. As the piston rises up the cylinder, it compresses the fuel air mixture, which now has nowhere to go. This compression primes the mixture for detonation. The stroke ends with the piston at the top of the cylinder and the mixture compressed into the small space in the head above.

Power Stroke

Now the fuel air mixture is detonated by the spark plug. The resulting explosion forces the piston down the cylinder and rotates the crankshaft against any attached load.

Exhaust Stroke

Exhaust valves in the heads above open up, and the piston rises up the cylinder, forcing out the exhaust gases, which are the ashes resulting from the combustion of the fuel air mixture.

Students from the College of Engineering at Trivandrum in India have developed an engine which adds two more strokes after the exhaust stroke. It uses air to scavenge heat from the cylinder and convert it to motive power. This can improve efficiency, because normally that heat is just wasted. The engine is a modified Honda four-stroke engine. After the exhaust stroke, valves open and allow cool air to flow in as the piston descends. The air gains heat from the very hot cylinder which causes it to expand. This heat-driven expansion occurs forcefully enough to actually power the piston down. In other words, there is a secondary, weaker power stroke after the exhaust stroke. On the sixth stroke (which is a secondary exhaust stroke), the rising piston forces the now warmer air out the exhaust.

This engine uses 40% less fuel and can run on normal gasoline.

Piston Rings

The piston rings in your car's engine are what keeps the compression build up in the cylinders. Anything off kilter with them will lead to loss of performance and efficiency in your engine. Here is a little video explaining how they work, and what the difference is between gasoline and diesel engine piston rings.

Sparkling Clean Spark Plugs

The job of the spark plugs is to ignite the fuel-air mixture inside the cylinders. The resulting explosion forces the piston back up the cylinder, which provides the power to turn the crankshaft. In top shape, the plugs provide just the right amount of electricity to efficiently burn all of the fuel. If they are out of shape, some of the fuel could be going unburnt, or the spark could be setting the explosion off out of timing. Out of timing explosions can work against the crankshaft, robbing power from your car. Both of these things can cost you gas. If your plugs are fouled by oil or just worn out from a long service life, you will be getting lower gas mileage than you should. Simply keeping your plugs like new can give you 4 or 5 miles per gallon more, helping you save on gas. Have your plugs checked or changed every 30,000 miles.

5 More Tips to Save on Gas

Drive Green: How To Save Money On Gas

Here are five more tips for how to save on gas. Keep your gas cap tightly fitted so you don't lose gas to evaporation. Keep your air filter clean. Very important one here: keep your tires inflated to the correct pressure. Have tuneups done regularly. The last tip is one that is easy to overlook. When you are doing city driving, keep your gas tank less than half full. Why? To save on weight. Having to haul around the gas in your tank makes your car do extra work, which burns extra fuel. In the city, you always have a filling station close by so there is no need to burn fuel carrying a reserve. Go ahead, watch the video, and save on gas!

Watch Out for Oxygen Sensor Problems

If your car uses an oxygen sensor (all the new ones do), then make sure it is not malfunctioning. The job of the oxygen sensor is to measure how much oxygen there is relative to fuel in the combustion mixture. What can happen is that faulty or old sensors can start to register more oxygen then there actually is. In response, the computer in your car will flood in extra gas to try to get the right fuel/air ratio. All this extra gas is not really needed, and just gets wasted. Result: you can get really big drops in gas mileage. A malfunctioning oxygen sensor can give a 40% drop in miles per gallon. That's right. A big fat 40%. Old sensors can give 20% drops in gas mileage.

If you have noticed that suddenly your car seems to be burning a lot more gas lately and you really don't know why, because you didn't change anything and nothing seems to be wrong, suspect the oxygen sensor. Have your oxygen sensor changed every 30,000 to 60,000 miles. The few bucks to have it done is worth it to save on all that gas!