Tuesday, October 17, 2006

Which is Best: Diesel or Electric/Gas Hybrid?

diesel injection Diesel Engine or a Gas/Electric Hybrid? hybrid powertrain

The short answer to diesel versus hybrid is the choice depends on what you want to use the vehicle for. If you want a truck with lots of towing power, buy a diesel. If you want a fuel efficient commuter car for urban driving, buy a hybrid car like the Toyota Prius, or buy a turbo diesel-powered car like a VW.

Unfortunately, your purchase options are very limited because hybrid gas/electric powertrains and diesel engines are only available in a few cars. Diesels have long been a popular option in light trucks and the availability has been pretty good. But diesel cars have been in short supply – and will get even harder to find for the next year or so thanks to new emission regulations.

As usual we get the wrong regulations at the wrong time. The EPA decided it would be a good idea to require cars and light trucks with diesel engines to meet the same emission regulations as cars with gasoline engines. The Tier 2 emission regulations, which all cars must comply with start in 2007, require a fleet average of 0.05 grams per mile of oxides of nitrogen, a figure today’s diesels cannot meet without low sulfur fuel and electronic direct injection technology. The rules also limit particulate (soot) emissions, which requires diesels to have some type of particulate filter in the exhaust. To make matters worse, California, New York, Massachusetts, Vermont and Maine have all adopted even tougher diesel emission standards than the federal EPA standards.

In Europe, where gasoline costs several times as mucha s it does here, and where diesel emission regulations are less strict, diesel powered cars account for over HALF the car population. The European limits for oxides of nitrogen are EIGHT times higher.

Unless the new regulations are relaxes or repealed (fat chance for that happening), the diesel option in cars and some light trucks (depends on size & weight) will go away in 2007, and will only slowly return as the technology improves.

Diesel Options:

Currently, the only diesel-powered cars available are:

Mercedes E Class E320 CDI
Jeep Liberty CRD
VW Passat TDI
VW Touareg TDI
VW Turbo Diesel Golf TDI

Technical Differences: Diesel vs Hybrid Gas/Electric

The main attraction of a diesel engine is that it is more fuel efficient than a gasoline engine: up to 30% better fuel economy as a rule than a comparable gasoline engine of the same displacement.

A diesel engine uses high compression rather than spark ignition to burn the fuel. This eliminates the need for an ignition system (no spark plugs, coils or ignition module), but it does require a very high pressure fuel injection system, much higher than that on a gasoline engine. Most diesel engines have a glow plug system for cold starting. There is also no throttle on a diesel engine, so it sucks air more efficiently at idle and low rpm (reduced pumping losses). The trade off is that a lack of intake vacuum in the engine requires a separate vacuum pump for any vacuum operated accessories.

On diesel engines, fuel is injected directly into the combustion chamber as the piston approaches top dead center. The timing of the fuel injector is critical for good engine performance. Compression ratios are very high 18:1 or higher, so it takes a LOT of pressure (300 bar to 1800 bar) to inject the fuel into the cylinder or a precombustion chamber in the cylinder head. The heat of compression causes the fuel to ignite spontaneously. That’s why no spark plugs are needed.

Mechanically, a diesel engine is essentially the same as a gasoline engine except for the higher compression ratio. Diesels typically have stronger crankshafts, connecting rods and pistons than gasoline engines, and they typically run at lower rpms. Most of these engines are VERY durable and will last well beyond 150,000 miles with proper maintenance. Regular oil changes, however, are essential to maintain a diesel engine because they experience more blowby of combustion byproducts into the crankcase than gasoline engines.

Things that can go wrong with a diesel engine include injection pump problems, fuel injector problems, blown head gaskets, hard starting in cold weather if the glow plug system fails, and fuel waxing. Diesel fuel is actually a very light oil, so if it does not contain the right additives it can gel and plug up the fuel line or filter in cold weather.

Older diesels were also notorious for their idle clatter and black smoky exhaust. Many light truck diesel engines still have those attributes, but most of the direct injection passenger car diesel engines built by Volkswagen are relatively clean and quiet.

Would I buy a diesel powered car or truck? It would depend on the current price of diesel fuel versus gasoline, the cost difference to get the diesel option, and how much better fuel mileage the diesel gets over its gasoline counterpart. It would also depend on what I would be using the vehicle for (towing or general driving). Diesels do require a little more maintenance, and most owners who want to avoid cold weather starting problems are religious about using fuel additives in cold weather. I don’t see either of those things being a drawback if I wanted a diesel.

Hybrid Gas/Electric

Hybrid electric vehicles use a conventional gasoline engine for propulsion, and an electric motor for supplemental power. The gasoline engine turns an alternator that keeps a large high voltage battery charged. Some hybrids are designed to shut off the gas engine when the vehicle stops moving to conserve fuel. The electric motor is then used to accelerate the vehicle up to a certain speed at which point the gasoline engine restarts and takes over. For maximum acceleration, the electric motor and gas motor may both provide power to the wheels. How the vehicle is programmed to balance gas power and electric power affects overall fuel economy as do driving conditions. That’s why a vehicle like the Toyota Prius gets better mileage in stop-and-go city driving than it does on the highway.

On other hybrids, the electric motor is used more like a supplemental power source to boost acceleration when extra power is needed. This allows the use of a smaller, more fuel efficient gasoline engine that gets better fuel economy without sacrificing too much performance.

The third approach is to have a start/stop only system, where the engine shuts off when the vehicle is stopped, and automatically restarts when the driver steps on the gas pedal. There is no electric propulsion.

Hybrid Vehicles Currently Available:

Toyota Prius
Toyota Camry hybrid
Honda Accord hybrid
Honda Civic hybrid
Honda Insight
Lexus RX400H
Ford Escape hybrid
2007 Saturn Vue hybrid
2007 Mercury Mariner hybrid

Hybrid Complexity

A vehicle like the Toyota Prius is a technical marvel in my opinion. But it is also a VERY complex vehicle that is much more complex than any gasoline or diesel-powered vehicle. Consequently, the more complicated the system, the more stuff there is to go wrong.

As long as everything is working fine, I see no reason not to own a Toyota Prius or any other hybrid. But when these vehicles get some miles and age on them, I wonder how well they will hold up. Personally, I would NOT want to be the second or third owner of a used hybrid gas/electric vehicle. Why? Because of the high cost to replace the hybrid high voltage battery, because of the high cost to fix any electrical quirks or failures that may occur in the powertrain, and because replacement parts are NOT yet available in the aftermarket for these vehicles. New car dealers currently have a monopoly on these cars, and charge accordingly for parts and service. Most independent repair shops and garages are not yet up to speed on hybrid technology, so the new car dealer is about the only place you can take your hybrid if the electronic components or battery need repair. Ordinary stuff like brakes, tires, mufflers, cooling system, or the gasoline engine can be serviced anywhere.

The next-generation hybrids that will have a plug-in option and larger battery so the vehicle can operate more on electric power and less on gasoline power will make hybrids even better.

Diesels are Better

In the meantime, I see clean direct injection diesels as the better short-term technology. The EPA needs to cut us some slack and roll back the new Tier 2 emission requirements for diesel engines. The environmentally-sensitive Europeans do not seem to be overly concerned about current diesel emissions, and are way ahead of us in diesel technology.

Diesel Sets New Land Speed Record

diesel race car Who says diesels have to be slow?

On August 22, 2006, the JCB DIESELMAX set a new land speed record for diesel-powered vehicles with a speed of 328.767 mph at the Bonneville Salt Flats, Utah. Powered by two state-of-the-art JCB444-LSR engines developed by Ricardo, the JCB DIESELMAX beat the existing record by almost 100 mph. The race car was powered by two JCB444-LSR engines with two-stage inter-cooled turbo-charging, high pressure fuel injection and a low compression ratio, low temperature combustion system. All of these technologies are being developed by Ricardo for application on the high performance, ultra-low Tier II emissions diesel vehicles of the future.

EV1 electric car Electric Cars are Best

Long term, the best powertrain choice in my opinion is a pure electric vehicle. Electric vehicles are environmentally clean, quiet and energy efficient. Fuel costs are potentially equivalent to over 100 mpg at today’s energy prices. If charged by electricity from cheap wind, hydroelectric or nuclear power sources, the economics make even more sense.

The battery technology isn’t quite there yet for a do-everything electric car, but ni-cad and lithium ion batteries are more than adequate for urban commuting, which satisfies the needs of about 90% of the population today. The problem is getting the major auto makers to commit to electric cars.

It’s no secret that car makers do NOT want to build electric cars. Why? Because electric cars are not profitable (at least not yet). Development costs are high, battery technology is still iffy, and the domestic car companies are heavily invested in internal combustion engine technology and production tooling. They would much rather sell us accessory laden SUVs and luxury cars than small fuel efficient vehicles regardless of what kind of power system is under the hood.

The domestic car companies cite all kinds of statistics that claim nobody wants electric cars, nobody would drive them if they were available other than wealthy left wing liberal Hollywood celebrities, and they would be too expensive for the average schmuck. Proponents of electric cars say the cars make perfect sense, that people would be standing in line to buy them if they were readily available, and that electric cars could be both affordable and practical if mass produced by major auto makers. I agree.

Related Articles:

Who Killed GM's EV1 Electric Car?
Light-Duty Diesel Diagnosis
About Alternative Fuels
E85 Ethanol Alcohol Alternative Fuel

Hydrogen the Fuel of the Future

I've seen the future and it's a gas -- hydrogen gas, that is. At a 2005 General Motors press conference at Northwestern University in Evanston IL, Larry Burns, vice president of GM research & development, described the future of automotive technology.

Today, there are about 750 million cars and trucks on the face of this planet. Yet only about 12% of the world's population can afford to own a vehicle. As economies in China, India, Mexico and other countries expand, vehicle ownership will become possible for millions of people who previously couldn't afford a vehicle. By 2020, GM conservatively predicts the world vehicle population will exceed 1.1 billion cars and trucks!

These numbers make it obvious that we're headed for some serious problems unless we somehow reduce our dependence on petroleum. Today's oil prices (which are around $60 a barrel) and gasoline prices ($2.30 at the pump) will seem cheap in comparison to what we will likely be paying in the not too distant future as worldwide demand outpaces the worldwide supply of oil.

Oil Supply

According to the latest oil industry estimates, world petroleum reserves are thought to be around 3 trillion barrels. We have already used up about a quarter of the total, and are currently consuming oil at the rate of 75 million barrels per day. Two-thirds of the oil we import is used for transportation in this country. If the world vehicle population continues to expand at its current rate, we're headed for trouble. The world simply can't supply enough petroleum to support this kind of growth and usage.

So what's the answer? Ration cars? Tell the rest of the world they can't have what we have? GM and most of the other auto makers think the best solution is to shift our dependence from petroleum to a different energy source -- namely hydrogen.

Hydrogen Fuel

Hydrogen is the simplest of all known elements, and the most abundant element in the universe. Water, which covers two-thirds of our planet, is two parts hydrogen and one part oxygen. Passing an electric current through water (a process called "electrolysis") can split water molecules apart freeing the hydrogen from the oxygen. The energy for electrolysis can be generated by solar cells, nuclear plants, wind generators, hydroelectric dams, geothermal generators, wave generators or even conventional fossil fuel burning power plants. Hydrogen gas can also be made from biomass or even garbage. The potential supply of hydrogen would seem to be almost limitless.

Hydrogen is also a clean-burning fuel that generates no carbon monoxide, no hydrocarbons and no soot -- only water vapor. It can also be burned in internal combustion engines, but its best use is in fuel cells -- and that's the future of automotive propulsion, says Burns.

Hydrogen Fuel Cell

A fuel cell is a relatively simple device that combines hydrogen and oxygen to create electricity. The electric current can then be used to turn electric motors to drive a vehicle. Fuel cells were invented as a power source for space capsules back in the 1960s, and researchers have been playing with them ever since in an effort to improve their efficiency and performance, and reduce their cost.

It seems that the pay-off is close at hand. GM's latest hydrogen fuel cell powered car (HydroGen3) is seven times more efficient than GM's last hydrogen-powered test car, which was built six years ago. Burns says GM should have a production-ready hydrogen-powered car by 2010. In fact, GM's latest concept car, called "Sequel," is a five-passenger crossover SUV that uses both a hydrogen fuel cell and lithium ion battery for combined power. The Sequel that was on display at the press conference appears to be a preview of what may be GM's first fuel cell powered production vehicle for the U.S. market.

The main issues now, said Burns, are the cost and availability of hydrogen. GM estimates it will cost about $10 to $15 billion to add hydrogen refueling capabilities to 11,700 service stations across the U.S. And if hydrogen is manufactured from natural gas at today's prices, it would cost about 1.3 times as much to power a vehicle with hydrogen compared to gasoline. But those numbers may soon change.

Hydrogen is currently around $4 per kilogram. If a hydrogen-powered car holds 8 kilograms of hydrogen in its tanks (enough to give it an estimated driving range of 300 miles), it would cost $32 to fill up. Compare that to what it currently costs to fill up a big fuel-thirsty SUV -- say $80 to $100. Seems to me hydrogen is already a bargain.

Hydrogen Car Test Drive

GM Hydrogen3 fuel cell car

I test drove the HydroGen3 fuel cell research vehicle, and found it to be remarkably unremarkable. That's actually a compliment because it drove pretty much like any other small car. Except for a little electric motor whine, the test drive was relatively quiet and uneventful.

The neat thing about this exotic technology is that it is essentially invisible to the driver. If the car wasn't plastered with decals and didn't contain engineering instrumentation, I'd have no way of knowing I was driving something that is radically different from what I've been driving all my life. The technology works and works well.

Hydrogen, however, is a much different kind of fuel than gasoline or diesel. It is a lightweight gas, not a liquid, and contains far less energy than gasoline. So hydrogen must be stored under extremely high pressure (up to 10,000 psi!), or liquefied at extremely low temperature (-423 degrees F) and held in an insulated cryogenic tank so it doesn't boil off.

For test purposes, the HydroGen3 fuel cell car is fitted with a 4.6 kilogram capacity liquid hydrogen fuel tank, and a 3.1 kilogram compressed gas tank. Hydrogen from the liquid tank provides a driving range of about 249 miles, and hydrogen from the compressed gas tank adds another 168 miles. Top speed of the test car is claimed to be 99 mph. I didn't have a chance to verify the top speed or the driving range, but I did have to sign a waiver before the test drive saying my widow couldn't sue GM if the hydrogen car blew up and cremated me.

Actually, hydrogen is no more dangerous than gasoline. It is highly flammable and burns almost invisibly. But the extremely strong high pressure fuel tanks makes a fuel leak in a collision much less likely than in a gasoline-powered vehicle with a relatively thin plastic fuel tank.

The only question I have about this new technology is what kind of service tools and equipment will be required to work on hydrogen-powered fuel cells?

Do Any Gas Saving Gadgets Really Work

When I originally wrote this piece, the price of regular grade 87 octane gasoline was almost $3.40 a gallon in the metro Chicago area. The huge jump in fuel prices ihit motorists hard. People started looking for ways to reduce their fuel costs. Some were trading in their big gas-guzzling SUVs for smaller vehicles. More people switched to public transportation and car pooling (both of which are almost as painful as paying more at the pump). And some fell victim to con artists selling gas saving gizmos that promise huge fuel savings.

As PT Barnum once said, "There's a sucker born every minute." So don't fall for the con artists lies. Forget the gas saving gizmos because none of them work!

Every gas saving gadget I've seen to date does absolutely NOTHING to improve fuel economy. In fact, some of them actually reduce fuel economy.

Products that claim to magnetize or polarize gasoline molecules, realign the molecular structure of the fuel for more efficient combustion, or ionize the spark for better mileage are pure nonsense and are based on false science. So are products that swirl air entering the throttle body or leak air into the intake manifold to improve fuel efficiency. None of these product produces any measurable improvement in fuel economy.

100 mpg carburetors or fuel injection systems? Pure science fiction and urban legend.


One gas saving gadget that can improve fuel economy is a simple vacuum gauge. The gauge displays intake vacuum, which is an indication of how much load is on the engine. The lower the vacuum reading, the higher the load on the engine and the more fuel it burns.

The gauge saves gas by helping the driver see the effect his right foot has on fuel consumption. Tromp down on the gas pedal and intake vacuum drops and fuel consumption goes up. Take it easy on the gas pedal and accelerate slowly causes less of a drop in intake vacuum and less fuel usage. Duh! Pretending there is a raw egg under the gas pedal can have the same positive effect on fuel economy.


Back in the days when carburetors were used to feed gasoline into the engine, there were a couple of tricks that could improve fuel economy a bit, especially when the engine was cold. One was a simple honeycomb spacer that fit under the carburetor. The turbulence created by the honeycomb helped break up the fuel a bit. Another was an ultrasonic vibrator that mounted under the carburetor. The vibrator also improved fuel atomization slightly -- but only provided a marginal benefit when the engine was cold.

Some engines from that period used an electrically heated grid under the carburetor to improve fuel atomization following a cold start. But like the other devices, the benefit disappeared once the engine reached normal operating temperature.

Today's fuel injected engines atomize the fuel when they spray the fuel into the engine. They don't need intake manifold heaters or other such devices. The most efficient designs are the new high pressure "direct injection" systems that VW uses on some of its engines.


Other fuel saving tricks that actually work include variable displacement on demand (which is used on the new Chrysler Hemi engines in the 300C and other models), and the start/stop systems that some of the new GM and Ford hybrid vehicles have to turn the engine off when the vehicle sits for more than a few seconds at a stop light to save fuel. Fuel savings attributed to these technical improvements range typically from 5 to 15%.

The most fuel efficient cars currently on the road are ones like the Toyota Prius (50 to 60 mpg city) and Honda Civic hybrids that use a combination of electric power and gasoline power to optimize fuel economy.

The most fuel efficient vehicles of all were GM's discontinued EV1 electric cars, which used no gasoline at all. GM built about 1,000 of these two-seat cars and leased them to motorists in California. Almost everybody who drove one said they loved it. Unfortunately, these cars were introduced a few years too soon and were discontinued because of limited range (about 100 miles on a full charge), and the high cost of the batteries (GM's cost was reportedly $500 for each battery, and each car held 18 batteries!). If GM were to re-introduce the EV1 today, buyers would be standing in line and paying full list price plus -- just like people who want to buy a Toyota Prius today.


Miracle friction-reducing oil treatments are also a scam. Many of these products contain Teflon, which is claimed to have a coating action that reduces wear and friction. General Motors evaluated some of these products a number of years ago using an electron beam microscope to examine engine parts after the engine had been run with the special treatment. Guess what? They couldn't find a trace of the stuff on any of the metal parts. The Teflon ended up in the oil filter and the bottom of the oil pan.


The only way to reduce internal engine friction is to run a lower viscosity oil with a "fuel saving" rating from the American Petroleum Institute (API). Switching from a 10W-30 to a 5W-30 or 5W-20 oil may improve fuel economy a few tenths of a percent, but that's about all the improvement you're going to get.


A dirty air filter that is clogged with debris will restrict airflow into the engine and hurt fuel economy, performance and emissions. Inspect the air filter and replace it if it is dirty. The photo at the top of this page shows an air restriction gauge that indicates when the air filter is dirty and needs to be replaced.

How can you tell if the filter is dirty? Hold it up to a bright light. If the filter element is dark and obstructs most of the light, the filter needs to be replaced.

Stock air filters flow just as much air at low to mid-range engine speed as most aftermarket "performance" air filters. Installing a less restrictive performance filter may improve performance slightly at high engine speed, but for normal driving it probably won't have any measurable impact on fuel economy.


Ignition misfire can waste a lot of fuel and cause a big increase in exhaust emissions. On 1996 and newer vehicles with OBD II, the engine management system is capable of detecting engine misfires and will turn on the Check Engine light and set a diagnostic trouble code (P0300 series) if it detects a misfire problem.

Misfire can be caused by worn or dirty spark plugs, high resistance in spark plug wires, a weak ignition coil, dirty fuel injectors, low fuel pressure (weak pump or dirty fuel filter), or compression problems (burned valves, weak or broken valve springs, leaky head gasket, rounded cam lobes).

Standard spark plugs should be replaced every 45,000 miles, while platinum or iridium tipped long-life spark plugs can typically go 100,000 miles before replacement is needed. Refer to your owners manual for the recommended replacement interval.

Some spark plugs have special electrode configurations that are designed to minimize misfires. These may have a marginal benefit on fuel economy and performance, but don't expect any miracles.


A less restrictive exhaust allows the engine to breathe easier and use less fuel. Replacing a restrictive stock muffler with an aftermarket performance muffler can reduce backpressure and improve performance and fuel economy slightly. But the trade-off is usually a significant increase in exhaust noise.


One way you can maximize fuel economy is to keep you tires properly inflated. Increasing tire pressure reduces rolling resistance, but also adds ride harshness. For most cars, 32 to 34 psi is the maximum recommended inflation pressure for average driving. Refer to your owner's manual or the tire inflation decal in the glove box or door post.

Never exceed the maximum inflation pressure printed on the tire sidewall. Overinflated tires ride rough and increase the risk of tire damage or tire failure!

Underinflated tires, on the other hand, increase rolling resistance and drag. This makes the engine work harder and uses more fuel. Low air pressure also increases flexing of the tire's sidewall, which makes the tire run hot. Driving on a low tire at high speed on a hot day or with an overloaded vehicle increases the risk of tire failure and a sudden blowout. Never drive on tires that contain less than 25 psi of air pressure.

Air pressure should be checked at least once a month, and every week if you do a lot of highway driving. The pressure should be checked BEFORE the vehicle is driven because driving increases the temperature of the tires and the air pressure inside. If a tire is low, use a foot pump or compressor to add air. Then recheck the pressure to make sure it is correct and is not overinflated (this is especially important when using a high pressure hose at a service station). Also, use an accurate gauge. The gauges on many tire inflation machines are out of calibration.


Lightening a vehicle by removing unnecessary junk from the trunk or cargo area can also improve fuel economy a bit. But don't toss the spare tire or jack because you may need these items down the road.

Getting the lead out of your own posterior can also help. Walk more and drive less. Ride a bike. Go on a diet. Every 10 lbs. of fat you lose is 10 lbs. less dead weight your engine has to push down the road.

Keeping your gas tank half full is another trick that can save some weight. Gasoline weighs about 6.2 lbs. per gallon (6.3 lbs. for premium), so keeping a 20 gallon tank h`lf full saves about 62 lbs. of weight. Don't run the tank too low, however, because that may shorten the life of your fuel pump. Most engines with electronic fuel injection have an electric fuel pump mounted inside the gas tank. The pump runs hot and needs a certain amount of fuel for cooling and lubrication. Running out of gas may damage the pump and end up costing you $300 to $600 to have a new one installed!

Auto Repair Diagnosis Help

Recently, I expanded the technical coverage on my AA1Car Diagnostic Help for Motorists website at http://www.aa1car.com . The has expanded coverage includes even more auto repair and diagnosis help for motorists and technicians:

To view the latest subjects, click on the topic links below:

check engine light diagnostic information, what to do when your MIL lamp is on CHECK ENGINE LIGHT and TROUBLE CODES

Look up technical service bulletins TSBs for your vehicle Look up Technical Service Bulletins for Your Vehicle

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Front-wheel drive FWD diagnostic and repair information Front-Wheel Drive Info

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Automotive maintenance guidelines chart Preventive Maintenance Guidelines

Engine sensor and powertrain control module diagnosis and repair information Sensor & PCM Related Problems

ignition and spark plugs Spark Plugs & Ignition Related Problems

Steering, suspension, alignment, tires and wheel diagnosis and repair information Steering, Suspension, Alignment, Tires Info

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Library of automotive technical diagnosis and repair articles by Larry Carley. . . Technical Library of Automotive Diagnosis & Repair Articles

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