Valve train is one of the essential system in the operation of the engine. I think you must always hear about DOHC, VVT-i or VTEC when talking about the car. All this terms basically come from the valve train of the engine. The function of the valve train is to control the air-fuel mixing into and out of the cylinder.

In modern engine, the basic components in valve train are camshaft, cams and of course the valves. The valves’ function is to allow the air-fuel mixture to enter or exit the cylinder. The movement up and down of the valves will be controlled by the rotation of the cams. The rotation of the cams will somehow controlled by the camshaft because all the cams will be attached to the camshaft.

The camshaft will connect to the engine’s crankshaft by the belt or drive chain to ensure the timing of the movement of the valves matching with the movement of the piston. Below are the pictures to make you all more understand about the valve train.

Valve

Camshaft

Valve train operation

Source:
1. http://auto.howstuffworks.com/engine4.htm
2. http://en.wikipedia.org/wiki/Valvetrain

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Most of the people always seeing or hearing this terms when reading or talking about the car. If you take out a brochure, there are many cars that had been described using DOHC valvetrain configuration. But what exactly the meaning of DOHC? Let’s check out.

DOHC stands for Double Overhead Camshaft. Actually, the engine need a valvetrain to operate (except most of two-stroke engine). The function of the valvetrain is to open and close the valves to allow the intake, compression, power and exhaust stroke operate smoothly. DOHC is one of the valvetrain systems that had been equipped in most of the modern cars.

Double stands for two while overhead means within the cylinder head or above the combustion chamber. Camshaft is an apparatus often used in engine to operate poppet valves that consists of a cylindrical rod running the length of the cylinder bank with a number of oblong lobes or cams. The cams force the valve open by pressing on the valve or on some intermediate mechanism. Camshaft is driven by either gear, chain or timing belt. So, DOHC is the two camshaft been placed within the cylinder head of the engine.

Camshaft

Cam operating

The advantages of DOHC are it allows the manufacturer to easily implement a 4 valve per cylinder setup, allows the engine to rev higher and allows the better placement of the valves in an optimized setup that gives maximum performance. The disadvantages of DOHC are more weight, more cost and more complexity.

Cylinder head sliced for DOHC

Suzuki DOHC engine

Source:
1. http://en.wikipedia.org/wiki/DOHC#Double_overhead_camshaft
2. http://en.wikipedia.org/wiki/Camshaft
3. http://paultan.org/archives/2005/06/22/sohc-vs-dohc-valvetrains/

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Check out your car’s tires now. What is the specification of the tires? And do you know what is the meaning by the specification that been shown on the tires? So, let me reveal what is the meaning of the tires specification by using the Mitsubishi Lancer Evolution X’s tires specification.

The specification for the Evolution X’s tires are P245/40R18. But what stands for P, 245, 40, R and 18? The letter P stands for passenger car. So, instead of using this standard Evolution X’s tires for racing, better changes to the other tires. It is because for the tires with the P letter in front, you get the grip and comfortable, not the performance tires. 245 stands for the section width of the tires in millimeters. 40 stands for the aspect ratio of the tires. It means the distance between the edge of the rim and the edge of the tire is 40% from 245 mm or 98 mm. R stands for radial tire and 18 stands for the diameter of the rim in inches.

So, instead of only know how to driving your car, better know your tires specification also for your better understanding with your cars.

Source:
1. http://en.wikipedia.org/wiki/Radial_tire
2. http://www.supercars.net/cars/3928.html

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Grab any car’s brochure and take a look at the car’s suspension. Basically, most of the modern cars have used the MacPherson Strut as the suspension. The advantages of the MacPherson Strut suspension is it provide low cost and easy to manufacture due to its simplicity.The disadvantages of this suspension are it cannot allow the vertical movement of the car. Also, with this suspension, the wheel tends to lean with the body leading to understeer.Also, this suspension tend to transmit noise and vibration from the road directly into the body shell, giving higher noise level. These drawback will affect the quality of ride and the handling of the car.

If you want to learn more about MacPherson Strut suspension, take a look at my source:
1. http://en.wikipedia.org/wiki/MacPherson_strut
2. http://www.carbibles.com/suspension_bible.html

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