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Engine Cylinder Head

admin — Fri, 12 Mar 2010 09:22:06 +0000

The cylinder head is located on top of the cylinder block. The bottom of the cylinder head is indented and combines with the piston to form the combustion chamber. Internally, there are a oil hole and a water jacket to cool the valves and the spark plugs. Most gasoline engines have cylinder heads made of aluminum alloy. Aluminum alloy is lighter than cast iron, and it has excellent heat conduction properties. In between the cylinder block and the cylinder head is the cylinder head gasket, which acts to seal the junction of the two parts in order to prevent leakage of highly pressurized gasses, combustion gasses, coolant and engine oil.

EnginePlastic Region Bolt

admin — Thu, 11 Mar 2010 09:23:26 +0000

The plastic region bolt is used in such areas as the cylinder head or bearing cap assembly to provide a steady bolt tension. Normally bolts are tightened to the elastic region. In this condition, the bolt is tightened to the specified tightening torque. In the elastic region, the bolt tightening torque and bolt tension becomes greater proportionally. For tightening a bolt in the elastic region, some tolerance will be created through the bolt thread, flange or washer if the bolt tension is controlled at the tightening torque. In the plastic region, there is almost no change in bolt tension from tightening torque. The plastic region tightening method uses the material properties so that the uneven bolt tension from fluctuations in tightening torque is reduced. Bolt tension is stabilized as bolt tension itself becomes greater.

EngineCylinder Block 1 of 2

admin — Wed, 10 Mar 2010 09:24:39 +0000

The cylinder block acts to maintain the compression pressure with the piston and receive the combustion pressure. Recent cylinder block consists of the aluminum cylinder block and the cylinder liner. However, there are engines without cylinder liners (2ZZ-GE engine). Also there are cylinder blocks made of cast iron. The cylinder bore is a cylindrical shape. However it becomes inclined for the upper part of the cylinder, which becomes high temperature and high pressure, and the piston thrust side, which is pressurized with the thrust force of the piston to wear. For this reason, the cylind er can become oval shaped or tapered due to partial wear. Various defective conditions resulting from cylinder wear:

Extreme piston-side knocking

Abnormal engine oil consumption

Compression leakage etc.

HINT:

Abnormal wear and damage inside the cylinder and damage mainly occur for the following reasons:

Insufficient lubrication

Improper maintenance of the engine oil or oil filter

Dust being sucked into the engine

Air-fuel mixture too rich

Overheating

Overcooling

1. Cylinder bore size

Even when brand new, there may be some difference in cylinder bore size due to unevenness in manufacturing precision. For that reason, there are three standard cylinder bore sizes. The size code of each cylinder is inscribed on the top of a cylinder block. In order to increase the precision of piston clearance, standard pistons that match the cylinder size are used. As the size code increases, bore size increases by about 0.01 mm. For some engines, there are four to five standard sizes. Further, there are engines where there is only one cylinder bore size, in which case they do not have the size code inscribed on the cylinder block.

2. Crankshaft main journal bore size

The crankshaft main journal bore is machine-manufactured along with the cylinder block and bearing cap. Differences in crankshaft main journal bore sizes occur from unevenness in manufacturing precision. For that reason, there are several standard crankshaft main journal bore sizes. This size code in inscribed on the bottom of the cylinder block. Use this code when selecting bearings to improve the crankshaft main journal oil clearance precision in order to prevent abnormal noise and seizing and to maintain good fuel economy. As the size code increases, the bore size increases in micron units. Number of standard size, size coding and location of inscription differ according to the engine models.

EngineCylinder Block 2 of 2

admin — Tue, 09 Mar 2010 09:26:03 +0000

EngineCrankshaft

The crankshaft acts to convert the linear motion of the pistons into revolving motion. In order to be able to receive great force and revolve at high speed, it needs enough strength and rigidity, along with durability to wear, and to be statically and dynamically balanced to rotate smoothly. The crank pin and the crank journal are attached by a hardening process in order to make it enduring and durable against wear. The balance weight is installed to balance with the crankshaft rotation. The crank pin and the crank journal have an oil hole. The oil travels from the cylinder block, enters into the oil hole of the journal and goes through to the crank pin.

REFERENCE

Crankshaft Offset

Offsetting the crankshaft center and the cylinder bore center serves to raise engine efficiency

The maximum amount of combustion pressure that the pistons receive can be efficiently transferred to thecrankshaft.

By reducing the amount of force in the thrust direction of the piston, friction loss is reduced.

HINT:

ExampleAmount of crankshaft offset

1NZ-FE and 2NZ-FE engines12 mm (0.472 in.)

1SZ-FE and 2SZ-FE engines8 mm (0.315 in.)

The numbers for the journal installation

position and installation orientation are

inscribed on the crankshaft bearing cap.

ExampleZZ engine series.

Some bearing caps are single unit with

ladder-frame construction, which consists

of the bottom of the cylinder block.

Foot Brake Disc Brake

admin — Sat, 06 Mar 2010 07:30:02 +0000

1. Construction

The disc brake consists of the following components.

(1) Disc brake caliper

(2) Disc brake pad

(3) Disc brake rotor

(4) Piston

(5) Fluid

2. Operation

The disc brake pushes the piston using the hydraulic pressure transmitted via the brake line from the master cylinder to cause disc brake pads to clamp down on both sides of the disc brake rotor and stop the tires from turning. Therefore, because the disc brake rotors and disc brake pads rub against each other, frictional heat is generated at this time. However, because the disc brake rotor and brake body are exposed, the generated frictional heat can be easily dissipated.

3. Brake Adjustment

Since the brake clearance is adjusted automatically by the piston seal (rubber), the brake clearance need not be adjusted by hand. When the brake pedal is depressed, the hydraulic pressure moves the piston and pushes the disc brake pad against the disc brake rotor. As this time, the piston moves while causing the piston seal to change shape. When the brake pedal is released, the piston seal returns to its original shape, which moves the piston away from the disc brake pad. Therefore, even if the disc brake pad is worn down and the piston is moving, the amount that the piston returns is always same, so the gap between the disc brake pad and disc brake rotor is maintained at a constant distance.

4. Decrease in brake fluid

The amount of brake fluid in the brake reservoir tank is decreased by the wearing of the disc brake pad or lining. Therefore, the wearing condition of the disc brake pad or lining can be estimated by checking the fluid level of the reservoir tank. Due to the piston’s large diameter, wearing of the disc brake pads results in a greater drop in the fluid level in the reservoir tank than in the case of drum brakes.

5. Pad wear indicator

When a disc brake pad wears and needs to be replaced, the disc brake pad wear indicator generates a highpitched screeching sound to alert the driver. In the case of the Corolla, the warning occurs when the actual pad thickness is approximately 2. 5 mm (0. 098 in). (1) Construction and Operation When pad thickness is reduced to the above-mentioned thickness, the pad wear indicator, fixed to the backing plate of the pad, comes into contact with the disc brake rotor and produces a screeching noise during driving.

HINT:

There are sensor type pad wear indicator brakes like that shown at the bottom left of the figure. When the sensor is worn down together with the disc brake pad, the sensor’s circuit is opened. The ECU detects the open circuit and warns the driver.

6. Types of disc brake caliper

The types of calipers are explained below. (1) Fixed caliper type A fixed caliper type has a pair of pistons to push the disc brake rotor in the both sides. (2) Floating caliper type A floating caliper type is attached the piston only on one side of the caliper. Pistons act the hydraulic pressure. If the disc brake pad is pushed, the caliper slides into the opposite direction of the piston, and pushes the disc brake rotor from the both sides. As a result, it stops the rotation of the wheel. There are several kinds of floating caliper type, depending on the methods to attach the caliper to the torque plate.

7. Types of disc brake rotor

The types of disc brake rotors are

explained below.

• Solid type

There is made from a single disc brake rotor.

•Ventilated type

There is hollow inside. Excellent heat dissipation.

•With drum type

Built- in drum brake for the parking brake.

HINT:

Fading

When the foot brakes are applied (without engine braking)

constantly on a long downhill slope, etc., the lining

and disc brake pads become extremely hot due to friction.

The coefficient of friction of the lining and disc brake pad

surfaces decreases as a result, and the brakes exert less

stopping power even if the brake pedal is depressed with

a great effort.

Main journal and crank pin size

admin — Sat, 06 Mar 2010 01:26:49 +0000

Differences in the main journal and crank pin circumference occur from unevenness in manufacturing precision. For that reason, there are several standard sizes for the main journal and crank pin. This size code is inscribed on the crankshaft. There are engines where there is only one size, in which case they do not have the size code inscribed. Use this code when selecting bearings to prevent the crankshaft main journal oil clearance precision or connecting rod oil clearance precision in order to prevent abnormal noise and seizing and to maintain good fuel economy. As the size code increases, the diameter of the main journal and crank pin decreases in micron units. Number of standard sizes, size coding and location of inscription differ according to the engine models.

EngineConnecting Rod

admin — Fri, 05 Mar 2010 02:13:18 +0000

The connecting rod takes the force, which the piston receives, and transfers it to the crankshaft. Since it is constantly affected by compressing and pulling force, it needs to be sufficiently strong and rigid. There is an oil jet attached to the big end of the connecting rod for lubrication and cooling. Engine oil is supplied through the crankshaft engine oil hole. The connecting rod attaches to the bearing cap, so check the front mark as not to make a mistake when assembling the two parts.

Engine Crankshaft Bearing

admin — Fri, 05 Mar 2010 02:02:35 +0000

When there is an appropriate oil film on the surface of the bearing, it can absorb the heavy load and shock from the rotating parts in the combustion stroke. This oil film prevents seizing and reduces output loss due to friction. There is an oil hole and oil groove in the upper half-bearing and it supplies oil to the bearing and main journal and lubricates. There is a locking lip to keep the bearing from rotating. The thrust washer absorbs the force applied to the crankshaft in the axial direction. There is an oil groove on the surface that touches the crankshaft. There is a tab on the bottom side thrust washer to keep it from turning. There are some engines that do not have the bottom side thrust washer.

1. Bearing size

There are several standard sizes for crankshaft bearings. This size code is inscribed on the back of the bearing. Use this code when selecting bearings to improve the crankshaft main journal oil clearance precision in order to prevent abnormal noise and seizing and to maintain good fuel economy. As the size code increases, the bearing thickness increases in micron units. Number of standard sizes and size coding differ according to the engine models.

2. Undersize bearing

When the crankshaft main journal is damaged or the oil clearance becomes larger, the main journal is ground and a thicker undersize bearing can be used. There are some engines that cannot accept an undersize bearing replacement. If this is the case, the crankshaft must be replaced.

Big end bore size

admin — Thu, 04 Mar 2010 02:17:38 +0000

The big end bore is machine-manufactured with the connecting rod and bearing cap. Due to unevenness in machine manufacturing precision, differences in big end bore size can occur. For that reason, there are several standard big end bore sizes. The size code of each bore is inscribed on a bearing cap. Use this code when selecting bearings to improve the connecting rod oil clearance precision in order to prevent abnormal noise and seizing and to maintain good fuel economy. As the size code increases, the big end bore size increases in micron units. Number of standard sizes and size coding differ according to the engine models.

Engine Bearing Selection

admin — Tue, 02 Mar 2010 02:24:27 +0000

The oil clearance for the crankshaft bearing and the connecting rod bearing is determined by the engine model. Each bearing should be selected to obtain the proper oil clearance with regard to the cylinder block main journal bore size and crankshaft main journal diameter, or the connecting rod big end bore size and crank pin diameter. As the bore size increases or the journal or pin diameter decreases, the thickness of the bearing to be used increases.

Oil clearance

Oil clearance is the gap between the bearing and the shaft. Oil covers the parts so that metal parts do not make direct contact with other metal parts. When the oil clearance becomes larger, abnormal sounds occur and oil pressure decreases, leading to seizing.

Bearing selection method

Use the following process to determine the correct bearing (size code).

A+B=C

ACylinder block main journal bore size code (or connecting rod big end bore size code)

BCrankshaft main journal size code (or crank pin size code)

CTotal number

Example:

ACylinder block main journal bore size code4

BCrankshaft main journal size code3

CA+B=4+3=7

Select the bearing with a size code of 3 from the chart on the left. In this case, the total number is used as is for the bearing size code from the chart. The selecting method varies by the engine model. And there are some engines where the total number becomes as it is for the bearing size code. There are some engine models that do not have a rank for the crankshaft main journal or crank pin. In this case, select a bearing with the same size code as the cylinder block main journal bore size code or connecting rod big end bore size code.