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Pushing Oil

The oil pump is literally the heart of an engine’s lubrication system. It sucks oil in from the crankcase and pushes it through the filter and oil galleries to the crankshaft and camshaft bearings. A constant supply of oil is needed to support and cool the bearings. If for any reason the pump cannot keep the oil circulating, it’s the end of the road for the engine. So let’s see how well you know your oil pumps. Answer the following:

True or False – The oil pump creates oil pressure in the engine.

If you answered “False,” you answered correctly. Now go treat yourself to a snack or a soda from the nearest vending machine – unless of course you can’t get a hall pass at this moment.

The oil pump doesn’t actually create oil pressure. All the pump does is displace oil and push it into the oil galleys so it can flow to the bearings and upper valvetrain. What actually creates the oil pressure is the resistance the oil encounters as it circulates through the engine.

Most manufacturers recommend a minimum of 10 psi of oil pressure for every 1,000 rpm of engine speed. Using these numbers, most stock engines have about 50 to 60 psi of oil pressure. But some engines need more.

Let’s Talk Types
There are three basic types of oil pumps:

  • Twin gear pumps, also called “external” pumps, use a pair of intermeshing gears to pump oil. One gear is driven by a shaft and the second gear is driven by the first gear. The pump is usually driven by a shaft that connects to the crankshaft, camshaft or distributor shaft. Thus, the pump operates at half engine rpm. The pump gears turn in opposite directions. This traps oil between the gear teeth and carries it around the outside of each gear from the pickup tube inlet to the pump outlet. The tight clearances between the gears prevents the oil from flowing backwards to the inlet.

  • Rotor pumps, also called “gerotor” pumps, have an inner gear that turns inside an outer rotor. The inner gear has one less lobe than the outer rotor. The inner gear is also mounted slightly off center to the outer rotor, which forces the outer rotor to spin at about 80% of the speed of the inner gear. This creates a bellows-like pumping action that pulls oil from the inlet port and pushes it towards the outlet port. Close tolerances are required for good pumping efficiency. This type of pump may also be located in the crankcase.

  • Front cover pumps, also called “internal/external” pumps are usually located in the front engine cover. This is also a rotor-style pump with an inner drive gear and outer rotor, but the inner gear is mounted directly on the crankshaft. The direct drive approach eliminates the need for a separate pump drive shaft. This type of pump turns at the same rpm as the engine, so it generates more pressure at idle and does a better job of sucking oil from the crankcase and getting it to the upper valvetrain in a hurry. That’s why front cover pumps are used on many overhead cam engines. When this type of pump becomes worn, it is not always necessary to replace the entire cover assembly – provided the pump housing inside the cover is not worn or damaged. A new drive gear can be mounted on the crankshaft, and a new rotor can be installed in the cover to rejuvenate the pump.

Diagnosing Bad Pumps
With all three types of pumps, wear and damage are major concerns. Wear that increases internal clearances between the gears, rotor and housing will reduce the amount of oil the pump displaces and cause a drop in oil pressure and delivery volume. That’s why high-mileage oil pumps may need to be replaced.

Low oil pressure indicates trouble and may be caused by a low oil level, worn main and rod bearings or a worn oil pump. Low oil pressure can lead to bearing seizure and engine failure, so it should not be ignored. Sometimes a bad oil pressure sending unit will give a false alarm. But if oil pressure is really low and the crankcase is full, the engine may need bearings and/or a new oil pump.

Need More ‘Umpf From Your Pump?
For some applications, you might need a “high-volume” or a “high-pressure” oil pump. High-volume pumps typically have longer gear sets to displace more oil. A high-volume oil pump may flow 20% to 25% more oil than a stock pump to increase oil pressure at idle and to compensate for increased bearing clearances and wear in a high-mileage engine. But a high-volume oil pump is no cure-all for worn bearings or sloppy bearing clearances. A high-pressure oil pump, by comparison, uses a stiffer relief valve that does not open until a higher pressure is reached (75 psi or higher). This type of pump can provide additional oil pressure at high rpm, but won’t have any effect on idle pressure when the pump is turning slowly.

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Crossword answers for September 2004

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Crossword answers for August 2004

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Your Career Starts with a High-Quality Education

If you love cars and want a college education, CAP (College Automotive Program) may be the right choice for you. CAP is a nationwide effort of DaimlerChrysler to train and employ the industry’s best automotive technicians.

The CAP automotive program is available at 35 various schools in 27 different states across the country.

DaimlerChrysler believes in the value of trained technicians. They have worked closely with colleges to design a relevant curriculum. Therefore, CAP students must complete all coursework to receive a degree.

All CAP colleges are certified by ASE/NATEF (National Institute for Automotive Service Excellence/National Automotive Technicians Education Foundation). Every CAP instructor is a DaimlerChrysler-trained, experienced professional. DaimlerChrysler provides the latest vehicles, components and instructional materials, plus high-tech diagnostic equipment, for hands-on training. Class size is limited to maintain a good instructor-to-student ratio. Qualified candidates who apply early are chosen first.

The average cost of the two-year associate’s degree in the CAP program is $10,500. To find out the specific cost of the nearest CAP program, contact the local CAP school coordinator for further details. A complete list of the CAP colleges can be located at www.cap.daimlerchrysler.com.

In addition to the college training, CAP provides valuable internship experience at a participating Chrysler, Plymouth, Dodge or Jeep dealership, where students get on-site training under the direction of master technicians. Students rotate class time and internship until they fulfill the requirements of an associate’s degree in Automotive Service Technology (or similar).

“When I started the program I basically had little or no experience,” said Roger Chavez, CAP Graduate/Service Technician at South Bay Chrysler-Plymouth Jeep in Torrance, CA.

“I was in a high school automotive program where we learned small, basic things. Here at the program I learned so much just in the first nine weeks on brakes. I’ve always been the kind of person who takes things apart and wants to know how they work. I really enjoy working at the Chrysler dealer. It’s given me a lot of opportunities financially. I believe the CAP program is the best program in the country. If I can do it, you can do it.”

While at their internship, not only will students learn about repair procedures for DaimlerChrysler vehicles, but also dealership service operations. During the internship, students receive hourly wages and pay increases based on performance. Students are also eligible for optional bonuses from a Bonus Incentive Fund, established by sponsoring dealers to compensate students for continued employment, according to the terms of the agreement you chose.

Students can choose from a number of agreement options. The CAP Agreement is a two-year plan (A two-year internship, during which students are paid an hourly wage and are responsible for 100 percent of tuition and book costs).

The CAP Contract is a four-year plan (two-year internship and two-year employment commitment), which is similar to the CAP Agreement, except that the student and dealer share tuition and book costs.

If students live near a city with a CAP college (go to www.cap.daimlerchrysler.com for a listing of colleges), students can find a local sponsor and continue to attend the program while living at home. If there is no local CAP college, students can attend school in another city, finding sponsorship there. Housing assistance is available through many of the colleges.

Additional information on the CAP program can be obtained by visiting www.cap.daimlerchrysler.com, or by contacting a participating CAP college and asking for the CAP coordinator.

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From the Track to Rack

Racing tires, like passenger car tires, are specialized for different applications and purposes. Every form of racing has its own speed, traction and handling needs that require specially designed tires. A Formula 1 car obviously needs a different type of tire than a NASCAR racer or a NHRA Top Fuel dragster.

Any kind of motorsport that involves triple digit speeds requires tires engineered to handle the heat and withstand extreme forces. The conditions a tire experiences at 220 mph are far more demanding than an ordinary passenger car tire experiences at normal highway speeds. Temperatures are much higher and centrifugal forces are several orders of magnitude greater.

Tire manufacturers are very tight lipped about their compounds and other “tricks” that go into racing tires because they don’t want competitors to discover their secrets. It’s like the Colonel’s secret recipe for fried chicken. The right combination of ingredients (in this case, rubber compounds, plies and tread design) creates a tire that wins races. The wrong combination of ingredients can be an also-ran – or worse. The last thing a tire manufacturer wants is a tire that doesn’t perform well or can’t go the distance and fails during a race.

Take, for example, Bridgestone/ Firestone Americas Holding (BFAH), a tire maker that’s involved in open wheel racing. BFAH supplies race tires for Formula One, CART and Indy cars, and sponsors the Firestone Firehawk and Infinity Pro Series races.

We have heard that BFAH goes to great lengths to protect the technology in its race tires. In fact, every tire has its own unique bar code so it can be tracked from cradle to grave. Every tire that is assigned to a team must be returned when the race is over. The tires are then shredded and burned so nobody can find out what’s in them.

Industry sources say such precautions are necessary because racing tire technology is constantly changing and evolving. Race tires are even purpose-built to suit the unique needs of various racetracks and racing conditions.

Tough It Out
As a rule, racing tires are stronger and stiffer than passenger car tires. They have to be to survive the extreme forces and high temperatures generated by sustained high-speed racing. But tires engineered for a road course, street course or short track must have more compliance than tires for a high-speed oval because speeds are lower.

Another difference between race tires and passenger car tires is the thickness of the belts and tread. Race tires have a much thinner tread because mileage is not an issue. The tires have to last the race – or until a pit stop allows a tire change, but that’s all. They don’t have to go 60,000 miles.

Reducing the thickness of the tread keeps down the total tire weight, which helps the tire run cooler and improves traction by reducing tread flex and squirm. The lower weight, combined with the ultra light alloy wheels, allows pit crews to change tires out faster.

Balance is critical, too. BFAH says it balances its high-speed race tires to 8/100ths of an ounce.

“What we learn on the race track can often be incorporated into street performance tires. The long link carbon black compounds that have been developed for race tires to provide heat resistance, longevity and consistency can also be used in passenger car tires to improve tread life,” a BFAH spokesperson said.

Another tire maker, Goodyear, also is involved with most forms of racing, except the major open wheel series.

Goodyear racing tires are used in drag racing, on dirt tracks, off-road, sprint cars, sports cars and NASCAR.

The tiremaker is equally protective of its race tire secrets, but relies on its distributors to collect and dispose of old tires when a race is over.

Goodyear builds all of its radial race tires on special equipment in Akron, OH. Though the building process is similar to that used for consumer tires, Goodyear uses very thin plies and treads to manage heat. The materials are also stickier and wider than those used in passenger tire construction.

Goodyear designers said a race tire tread is about 1/4th the thickness of a passenger car tread, and the belts and plies are about half the thickness of ordinary tires. The curing process is essentially the same and uses a mold to vulcanize the green tire. But after the tire is cured, it undergoes a special inspection procedure that measures force variation and spring rate. The flex characteristics of each tire are marked on the tire so a race team knows how much air pressure to add to change the effective spring rate of the suspension.

The tires are also x-rayed to detect the presence of any foreign material or flaws, and holographed to check for air entrapment. Each tire is placed inside a vacuum chamber. Cameras then examine the tire for any air bubbles that are exaggerated by the vacuum.

The materials and tooling Goodyear has developed to build its race tires help it build better passenger car tires. “What we’ve learned on the racetrack has helped us improve the heat and stress management capabilities of our passenger car tires – especially on speed-rated tires like those we provide for the Corvette,” a Goodyear spokesperson said.

Many other tire brands – BFGoodrich, Falken, Kumho, Michelin and Yokohama, for example – are also heavily involved in various forms of professional and amateur racing.

The top professional series – Trans-Am, GT and Formula 1, for example – also get high tech course-specific tires. Some mid-pro also get special treatment with special compounds on DOT-approved tires. And many amateurs race on their favorite street tires.

Dealers are often involved, especially at the amateur events, supplying tires, providing mounting and balancing services, and shaving treads on street tires. This is not just a source of additional revenue for dealers; participation in these events helps build their performance image. In addition, they can relay technical information back to the manufacturer to help improve the street-use tires they sell.

So the next time you’re watching a race, think about all the technology that’s gone into the tires on the race cars – and how some of that technology filters down to the tires you use or may even sell to customers should you select a career in the tire industry.

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Crossword answers for May 2004

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Crossword answers for April 2004

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Questioning Misfires

Although the spark plug is a wee component, its effect on a properly running internal combustion engine is immense. In fact, this component has “sparked” many a question from professional techs on its use and replacement. We thought we would share with you some technical questions and answers regarding spark plugs and their importance toward a properly functioning engine.

What Causes a Misfire?

The spark that jumps across the gap between the plug’s electrodes ignites the fuel mixture and releases the explosive power in the fuel. If there’s no spark or the spark is too weak to ignite the fuel, the engine misfires, looses power, wastes fuel and pollutes.

Misfires are bad news because unburned fuel passes right through the engine and into the exhaust. This increases emissions and also causes the catalytic converter to run hotter than normal. A really bad misfire may even damage the converter.

Every engine misfires occasionally, but if the spark plugs are worn or fouled, or the ignition system can’t deliver enough voltage for reliable ignition, misfires may cause hard starting, rough running, hesitation, increased fuel consumption and elevated hydrocarbon (HC) emissions. It doesn’t take many misfires to make a vehicle fail an emissions test.

What Type of Plug Shall I Use?

One way to prevent misfires is to make sure the engine has a good set of spark plugs. These can be standard plugs, long-life plugs or performance plugs. As long as they produce a hot, reliable spark, ignition misfire shouldn’t be an issue.

To minimize the risk of misfire and maximize ignition performance, today’s spark plugs are designed to resist fouling and wear under a wide range of operating conditions. Improvements in electrode alloys allow many plugs to now last up to 100,000 miles. With conventional plugs, the recommended replacement interval is typically 45,000 miles.

Why Do Plugs Need Replaced?

Spark plugs need to be changed periodically because of wear and fouling. Every time a spark plug fires, a microscopic amount of metal is lost from the electrodes. As the miles add up, the electrode gap grows wider and wider increasing the voltage required to create a spark. Eventually the point is reached where the ignition system can no longer provide enough volts to fire the plug resulting in a misfire.

Fuel residue and oil ash also build up on spark plugs. Normally, the plugs get hot enough to burn off the deposits, but with frequent short-trip driving, the plugs may not stay hot enough long enough to burn off all the deposits. This can allow deposits to build up and interfere with the spark causing misfires.

The condition of the spark plug wires is also important. Wires that are damaged, cracked, loose or exceed resistance specifications must be replaced to assure a hot, reliable spark.

What Are Some Plugs Improvements?

Spark plug manufacturers have succeeded in extending the life of spark plugs and fouling resistance by going to high-temperature electrodes made out of platinum, iridium and other exotic metals. Platinum is one of the best conductors of heat and electricity. It also resists chemical corrosion and electrical erosion much better than ordinary steel alloys, making it an ideal material for the electrodes in long-life spark plugs. Iridium is even better. Iridium is six times harder and eight times stronger than platinum. This allows the use of a smaller center electrode, which reduces the voltage required to fire the plug by as much as 5,000 volts compared to a standard spark plug.

Spark plug manufacturers also use a variety of different electrode configurations to reduce misfires by exposing more of the spark and flame kernel to the fuel mixture inside the combustion chamber. Extended electrodes, surface gap electrodes, multiple electrodes and specially-shaped outer electrodes are all different techniques that are used to improve ignition performance and reliability.

Replacement spark plugs can be any brand and almost any type as long as the thread diameter and length, seat type, electrode reach and heat range are correct for the engine application. Follow the spark plug manufacturer’s recommendations for replacement plugs.

What About Upgrading?

Upgrading from conventional spark plugs to long-life plugs can reduce the need for future maintenance and lessen the need to change plugs as frequently on vehicles where plug access is difficult (like the back plugs on FWD cars and minivans with transverse mounted engines). Today’s tight engine compartments don’t leave much elbow room for changing plugs on many V6 and V8 engines, which is one reason why the OEMs have mostly gone to long-life 100,000-mile spark plugs. The other reason is to reduce the risk of misfires, emission failures and possible converter damage caused by worn or fouled spark plugs.

What are “Performance” Spark Plugs?

Performance spark plugs are primarily designed to reduce misfires. Some are also designed to last longer than standard plugs, but others are not.

Contrary to what you may have heard, performance spark plugs can’t create horsepower that isn’t there. What they do is maximize engine horsepower by reducing misfires.

When the engine is under load or when the pedal is to the floor, a much denser air/fuel mixture is present in the cylinders and cylinder compression pressures are much higher. This puts more of a strain on the ignition system and makes it harder to ignite the mixture each time the plug fires.

If the mixture doesn’t light, a misfire occurs and the engine loses power. Every misfire is a missed power stroke so it doesn’t take a lot of misfires to hurt performance, fuel economy and emissions.

When a V6 engine is cruising down the highway at 3,000 rpm, each spark plug is firing 25 times per second. At this speed, it’s virtually impossible to feel or hear an occasional misfire, unless the rate of misfire is really bad.

One way to reduce misfires under load and improve ignition reliability is to expose more of the spark to the air/fuel mixture. Standard electrodes tend to shield the spark somewhat and can actually quench the initial flame kernel under some operating conditions. To open up the spark, some spark plug manufacturers split the tip of their outer electrodes. Others use smaller, thinner electrodes or an outer electrode that comes to a point rather than having a square end. Some plug manufacturers add additional electrodes (two, three or four) and/or use a surface gap electrode to expose more spark to the mixture and reduce misfires as well as electrode wear.

Performance spark plugs cost more than regular spark plugs because of these added design features, and they generally give the best bang for the buck. Performance plugs are a good upgrade for any high-performance vehicles as well as those used for towing or sustained high-speed driving.

How Do I Choose Spark Plugs with the Correct Heat Range?

Follow the spark plug manufacturer’s recommendations. Spark plugs come in a variety of different thread diameters, pitches, reaches and configurations to fit different engines. Spark plugs also have different operating temperatures or heat ranges that vary from one engine to another. The heat range depends on the type of electrode material (copper and platinum help carry heat away from the center electrode) and the length heat has to travel down the center electrode to the steel shell.

It’s important to get the right heat range spark plug because this affects the plug’s ability to burn off fouling deposits and to resist preignition and detonation.

If the heat range is too cold for a particular engine, the spark plug may have fouling problems at idle or low speed. If the heat range is too hot, the spark plugs can run dangerously hot and cause engine-damaging preignition and detonation.

Most spark plugs today have broad enough heat ranges to satisfy almost all driving conditions. But for some performance applications it may be necessary to select a plug that’s one or two ranges colder to prevent preignition and detonation when the engine is working hard. Switching to a hotter plug in a high-mileage engine that is burning oil may help reduce fouling and extend plug life.

Can a Set of Spark Plugs Really Go 100,000 Miles?

Yes, but not if the engine is using oil or the vehicle is used only for short trips. Spark plugs have to get hot to burn off normal fuel and oil deposits. If the engine is never run very long or under heavy enough load to heat up the plugs, they may not get hot enough to burn off all the deposits. Over time, the deposits will accumulate and eventually foul the plugs causing them to misfire.

Electrode wear can also cause plugs to misfire. Every time a spark plug fires (which is thousands of times per mile), a few molecules of metal erode off the electrodes. As the miles accumulate, the electrode gap widens and requires more firing voltage from the ignition system to make a spark. Eventually the gap is so wide that the spark can’t jump across it to ignite the fuel. A misfire occurs, and the engine wastes fuel and pollutes.

The lifespan of standard spark plugs is typically around 45,000 miles. Long-life plugs, which typically use platinum or iridium electrodes, resist wear much better than standard plugs and can theoretically last much longer, up to 100,000 miles or more under ideal operating conditions. But as was stated earlier, if the engine is burning oil because of worn valve guides, piston rings or cylinders, the plugs will probably foul out long before they ever reach their upper wear limit.

Some spark plugs have multiple electrodes to improve ignition reliability and reduce wear. When a multi-electrode plug fires, there’s still only one spark and it jumps from the center electrode to one of the outer electrodes. The next time it fires, the spark may jump to a different electrode and so on, spreading the wear around and extending the life of the plug.

Long-life plugs reduce the need for changing plugs and are a good choice for engines where plug access is difficult (which is most V6 and V8 engines these days!) Long-life plugs cost more than standard spark plugs, but more than pay for themselves in their greater longevity and performance.

Steps to Choosing Racing Spark Plugs

Do you like to race? Selecting the proper race plug for your customer’s engine can mean the difference between front of the pack and a DNF. When using this guide, understand that race plugs are usually of a much colder heat range rating than automotive plugs. Colder plugs must be used in engines with increased cylinder pressures, higher temperatures and greater BHP. Other factors such as fuel delivery (turbo, supercharged), fuel types and piston-to-head clearance will also affect proper plug selection.

Step 1: Shell Design – The first step in choosing the proper race plug is determining the plug type that your cylinder head/piston will accept. Thread diameter and pitch, thread length and shell seat, as well as hex size are all factors that will define what shell type works best for your engine.

Step 2: Electrode Design – The second decision is electrode design and configuration. Is it a fine wire center or standard electrode? Projected or non-projected? Full coverage ‘J-Gap’ or perhaps a cut-back or angled ground wire? A good rule of thumb is to attain as much projection into the cylinder as possible. But be aware of piston clearance that could prohibit projected designs from being used.

Step 3: Heat Range – The third factor in choosing a race plug is heat range. Correct heat range is critical in maintaining peak performance throughout the duration of your race or event. Switching to a colder or hotter plug will not increase horsepower, but could affect engine performance. Choosing a plug that is too hot can result in preignition or detonation. A plug that is too cold could cause an engine to stumble, misfire or foul.

The main factors to consider in selecting the proper heat range are: type of race, methanol, specific output, nitro-meth, compression ratio, nitrous oxide, horsepower, super or turbo charging and racing fuel.

Source: Champion Spark Plugs

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Crossword answers for March 2004

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Crossword answers for February 2004