Australian Car Advice | News Blog

Power steering is a system for reducing the steering effort on cars by using an external power source to assist in turning the wheels. All modern cars come with power steering. Although they take the “feel” out of driving, for many driving without power steering is a whole new experience. There are three types of power steering:

Hydraulic systems

Most power steering systems work by using a belt driven pump to provide hydraulic pressure to the system. This hydraulic pressure is generated by a rotary-vane pump which is driven by the vehicle’s engine. As the speed of the engine increases, the pressure in the hydraulic fluid also increases, hence a relief valve is incorporated into the system to allow excess pressure to be bled away.

While the power steering is not being used, i.e. driving in a straight line, twin hydraulic lines provide equal pressure to both sides of the steering wheel gear. When torque is applied to the steering wheel, the hydraulic lines provide unequal pressures and hence assist in turning the wheels in the intended direction.

Electric systems

More modern systems, such as those found on the Acura NSX, use completely electric components. Sensors detect the motion and torque of the steering column and a computer applies assistive power via electric motors. This allows varying amounts of assistance to be applied depending on driving conditions.

In contrast to hydraulic systems, with an electric system the “communication” is only one way. The steering wheel transmits forces to the front wheels assisted by the motors, but the forces on the front wheels are not transmitted back through the motors to the steering wheel. Electric-only systems thus do not provide as much feedback to the driver, a criticism commonly expressed as a lack of steering “feel”.

Electro-hydraulic systems

So called “hybrid” systems use the same hydraulic assist technology as standard systems, with the hydraulic pressure being provided by an electric motor instead of a belt driven one.

Rotary Valve

The “rotary valve” is the key to the operation of power steering. It directs the power steering fluid under pressure to either side of the rack piston, which converts hydraulic power to mechanical force. Friction from the wheel causes a torsion bar in the rotary valve to deflect. This changes the position of the valve spool and sleeve, directing fluid under pressure to the proper end of the power cylinder. The difference in pressure on either side of the piston (which is attached to the rack) helps move the rack to reduce turning effort. Find out how to clean your valve

Rotary Engine | Wankel Engine

The rotary engine applies power directly to the transmission. Its construction allows it to provide the power of a conventional engine that is twice its size and weight and that has twice as many parts. A large combustion chamber in the form of a pinched oval, called an epitrochoid is the basic unit of the rotary engine. Within this chamber all four functions of a piston take place simultaneously in the three pockets that are formed between the rotor and the chamber wall. Just as the addition of cylinders increases the horsepower of a piston-powered engine, so the addition of combustion chambers increases the power of a rotary engine. Larger cars may eventually use rotaries with three or four rotors.

In the rotary engine, the four strokes of a typical Otto cycle engine are arranged sequentially around an oval, unlike the reciprocating motion of a piston engine. In the basic single rotor Wankel engine, a single oval (technically an epitrochoid) housing surrounds a three-sided rotor (a Reuleaux triangle) which turns and moves within the housing. The sides of the rotor seal against the sides of the housing, and the corners of the rotor seal against the inner periphery of the housing, dividing it into three combustion chambers.

As the rotor turns, its motion and the shape of the housing cause each side of the rotor to get closer and farther from the wall of the housing, compressing and expanding the combustion chamber similarly to the “strokes” in a reciprocating engine. However, whereas a normal four stroke cycle engine produces one combustion stroke per cylinder for every two revolutions (that is, one half power stroke per revolution per cylinder) each combustion chamber of each rotor in the Wankel generates one combustion ’stroke’ per revolution (that is, three power strokes per rotor revolution). Since the Wankel output shaft is geared to spin at three times the rotor speed, this becomes one combustion ’stroke’ per output shaft revolution per rotor, twice as many as the four-stroke piston engine, and similar to the output of a two stroke cycle engine. Thus, power output of a Wankel engine is generally higher than that of a four-stroke piston engine of similar engine displacement in a similar state of tune, and higher than that of a four-stroke piston engine of similar physical dimensions and weight.

National agencies which tax automobiles according to displacement and regulatory bodies in automobile racing variously consider the Wankel engine to be equivalent to a four-stroke engine of 1.5 to 2 times the displacement; some racing regulatory agencies view it as offering so pronounced an advantage that they ban it altogether.

Much more information can be found here

Radiator Shroud

The radiator shroud prevents the recirculation of air around the fan. It is usually a plastic hood that encloses the fan to guide the air through the core, and stop it from coming back around and through the fan again. It also protects you from the fan blades. The plastic covering does tend to break or come loose, so it is worth checking and making sure you are careful when you are working on the engine. If the fan that pulls air through the radiator core to cool the engine coolant is too far back, it will end up recirculating the same hot air that has collected behind the radiator. For this reason, the radiator often has a shroud.

Radiator Grille

The grating that admits cooling air to car’s radiator. The radiator grille is the part of the body shell on the front of your car that covers the area where the air enters. The radiator grille can also be part of the bumper on some cars (although not very common). The radiator is connected to the shroud for the radiator, which directs the air that comes in through the radiator grille to the radiator only. This prevents the air from escaping around the radiator and failing to cool the engine. On newer cars, the radiator grille has been lowered to take advantage of lower hood lines, brought about by an effort to increase fuel efficiency. Radiator grilles are very important as they help keep your engine cool. It is important to make sure yours is not covered with dust, leaves or other objects that might prevent good air flow.

Radiator Cap (Pressure Cap)

The radiator cap is more than a cap for your radiator; it keeps your engine cool by sealing and pressurizing the coolant inside it. It is designed to hold the coolant in the radiator under a predetermined amount of pressure. If it was not kept under pressure, it would begin to boil, and soon all the coolant would have boiled away. However, the radiator (or pressure) cap prevents this from happening by exerting enough pressure to keep the coolant from boiling. If your cooling system is under too much pressure, it can “blow its top”! To prevent this, the radiator cap has a pressure relief valve. The valve has a preset rating that allows it to take just up to a certain amount of pressure. When you turn the cap on the filler neck of the radiator, you seal the upper and lower sealing surfaces of the filler neck.

The radiator cap actually increases the boiling point of your coolant by about 25 C. How does this simple cap do this? The same way a pressure cooker increases the boiling temperature of water. The cap is actually a pressure release valve, and on cars it is usually set to 15 psi. The boiling point of water increases when the water is placed under pressure.

The pressure relief valve spring is compressed against the lower seal when you lock the cap. The radiator filler neck has an overflow tube right between the two sealing surfaces. If the pressure in the cooling system exceeds the preset rating of your cap, its pressure relief valve allows the lower seal to be lifted from its seat. Then the excess pressure (coolant, air) can squish through the overflow tube to the ground or the coolant reservoir.

When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place where this pressure can escape, so the setting of the spring on the cap determines the maximum pressure in the cooling system. When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled.

Radial Tyres

In radials tyres the ply or ply cords are alligned at 90 degrees to the circumference. While radials improve performance the fact is that they are not very good for bad roads and overloading. The suspension of a vehicle has, also, to be modified to accept radials. Radials offer much better grip of the road especially on surfaces which offer poor wheel traction like wet of slippery roads. The beauty of the radial design is that it separates the functions of the sidewall and crown of the tyre, allowing greater vertical flexibility whilst ensuring that there is still as much surface in contact with the road as possible. In classic radial tyres the sidewall has a one or two layers of textile cord giving good flexibility, and the tread is made rigid by combining the casing layer with two (or more) layers of steel cord bracing plies. Both these factors give the classic radial tyre excellent road holding capabilities and a longer life span when compared to vintage cross-ply tyres.

Rear View Mirror

The rear view mirror is a wide rectangular mirror that you (the driver) use to view anything behind the car. You don’t have to take your eyes off the road to turn your head around. Modern day cars might have mounted cameras on the back of their cars to assist with parking and reversing.However oOn most cars, the rear view mirror has a “day/night” selection switch that tilts the mirror inside its glass housing without tilting the exterior glass housing itself. The switch tilts the mirror upward, about five degrees, to divert the majority of the light striking the mirror up on to the headliner of the car. The light that you see when the mirror is on the “night” setting is actually bouncing off the glass housing (a good reason to keep it clean). The percentage of light reflected into your eyes in the night position, is very small compared to the amount that would normally be reflected into your eyes in its normal position.

Push Rod

A push rod is a connecting link in an operating mechanism. Two examples are the rod between the valve lifter and rocker arm on an overhead valve engine, and push rods at the piston ends which apply pressure to the brake shoes. Push Rods attach the valve lifter to the rocker arm. Through their centers, oil is pumped to lubricate the valves and rocker arms.

Parking Brake
The mechanical hand- or foot-operated brake that prevents the vehicle from rolling or slipping when parked.

The parking brake (or hand brake) holds one or more brakes continuously in the applied position. The parking brake employs the regular drum brakes on the rear wheel. Instead of hydraulic pressure, however, a simple mechanical linkage is used to engage the brake shoes. When the parking-brake pedal is depressed (or, in some cars, a hand lever is raised), a steel cable pulls taut a tension lever; other cables draw the brake shoes firmly against the drums. The release knob slackens the cables and disengages the brake shoes. The parking brake is self adjusting. An automatic adjuster in the piston moves on the thrust screw to compensate for lining wear.

Parking Brake Warning Light

The parking brake warning light notifies the driver that the parking brake is engaged. This reduces the chances of driving off with the parking rake engaged, causing premature wear of the rear brakes.    

Summary :

The type of valvetrain arrangement in which the engine’s camshaft(s) is in its cylinder head(s). When the camshaft(s) is placed close to the valves, the valvetrain components can be stiffer and lighter, allowing the valves to open and close more rapidly and the engine to run at higher rpm. In a single-overhead-cam (SOHC) layout, one camshaft actuates all of the valves in a cylinder head. In a double-overhead-camshaft (DOHC) layout, one camshaft actuates the intake valves, and one camshaft operates the exhaust valves.

More Detail: 

Overhead camshaft (OHC) valvetrain configurations place the camshaft within the cylinder heads, above the combustion chambers, and drive the valves or lifters directly instead of using pushrods. When compared directly with cam-in-block (or OHV) systems with the same number of valves, the reciprocating components of the OHC system are fewer and in total will have less mass. Though the structures that support the system may become more complex, most engine manufacturers easily accept the added complexity in trade for better engine performance and greater design flexibility. The OHC system can be driven using the same methods as an OHV system, these methods may include using a timing belt, chain, or in less common cases, gears.

Many OHC engines today employ Variable Valve Timing and multiple valves to improve efficiency and power. OHC also inherently allows for greater engine speeds over comparable cam-in-block designs.