Engine Tuning Basics

As your car left the factory the engine was set up ideally for most of drivers who require not a lot more than efficiency, reliability and economy. However, there are those of us who see the auto as a platform for creating something a bit more unusual with tuning its engine. This can be as easy or as complicated as your wallet can take, however there are some rules that ought to be followed first. Before starting any type of engine tuning, you should guarantee that your engine is running as the manufacturer intended. As soon as this has been completed you are set to extract a little more power from the engine.

Phase one is to get cleaner (and rather cooler) air to the engine and allow more fumes to go out the engine. This is done by adding a performance air filter and a performance exhaust. The air filter, can be either a substitute panel that fits in the presented airbox or a total replacement kit comprising of a cone filter and tubing. There are also numerous options for the exhaust system. Most cars have three segments in the exhaust system, the manifold starting at the engine block, a centre part and the muffler at the ending. Replacement of the centre and miffer is the minimum you must do.

Changing the exhaust and filter will not release that much power, but will make the engine breathe more freely and you should feel a little more response from the vehicle under speeding up. At this time we reach a split in the road of tuning. The road which you decide to follow depends on what kind of engine you possess. The first way is for naturally aspirated engines (with no a turbo) and the second way for forced induction cars (turbo or supercharged). At this step it would also be sensible to inspect the braking, suspension system, tyres and the gearbox as with additional power available, breaking and cornering are more important than earlier.

For a naturally aspirated engine, the next stage is to work on the head by porting it to increase the displacement and acquire a considerable amount of power. The camshaft should as well be replaced for a fast road kind. You should then look at the supplementaries such as spark plugs, the fuel pump, the oil pump, before going on to the bottom end and the crank. For a forced induction auto you need to look at the ECU and switch the intercooler with a larger capacity model. The ECU should be checked and either re-programmed or swaped with a performance item to increase power and enhance drivability. Depending on your taste you might wish to add a blow-off valve to let the turbo to operate more effectively. Water injection, stronger pistons and an bigger turbo should be next on your list. You can as well take into account adding a turbo to a naturally aspirated engine to considerably increase the power for a reasonably small sum of cash.

Engine Compression Ratio – Static versus Dynamic

If we split this phrase apart and look in the dictionary we will come across:

Compression – as an adjective means to squeeze.
Ratio – as a noun means a proportion of two things.

When talking about engines we classify two kinds of compression ratios (CR): static and dynamic.

Static CR

The static compression ratio is defined as the volume of the combustion chamber when the piston is in the bottom dead center (BDC) – very bottom of it’s journey – divided by the volume of the combustion chamber in it’s top dead center (TDC) – very top of it’s travel.

Static compression ratio is one factor that influences how totally the air-fuel mixture is burned, once it has been lit by the spark. If you burn all of the air-fuel mixture you get more hp. If there is some leftover unburnt air-fuel mix after the spark has been lit, you have not gotten all the power you can make out of the mix. This fullness of burn is named thermodynamic efficiency.

Improving thermodynamic efficiency is one of the 3 main power-gaining techniques existing for engine builders. Though, the problem is that as you increase CR, you increase cylinder pressure and temperature inside the combustion chamber. As air is squeezed hard inside a closed container like a cylinder, the pressure in goes up the harder you squeeze. As pressure goes up, so does temperature. This can initiate a process named self-detonation – the air-fuel mixture ignites by itself without the spark.

Secondly, as you rise static CR more and more, the cylinder pressures grow progressively. The piston must work a lot harder to squeeze identical amount of air-fuel mixture delivered into the chamber by reason of this higher pressure. This negative work slows the piston speed momentum which influences the power you make.

So you can produce additional power by improving burn efficiency via growing the static CR up to a point. For street engines, the maximum static CR on pump gas is close to 12.5:1 CR if you know how to tune. If you don’t, the maximum is close to 11.5:1 CR. For a race engine, the spot at which cranking pressure causes negative work and affects power production is approximately 14:1 CR.

Dynamic CR

The piston is continuously moving up and down however the intake valve opens and closes during this time also.
When the piston is starting to squeeze at BDC, the intake valve is starting to close. The intake valve is not wholly shut until the piston is almost at TDC. There is a link between the cylinder combustion chamber and the intake port/intake manifold runner, when the intake valve is still partially open. As the piston is squeezing and moving toward TDC, some cylinder pressure can loose pressure up into the intake port which reduces whole cylinder pressure.

If you use your adjustable intake cam gear to close the intake valve earlier, the amount of cylinder pressure bleeding up the intake port is reduced. The cylinder pressure builds up sooner and you get a better burn.

If you let the intake valve close later, more cylinder pressure will bleed out or be decreased and the burn will be less complete.

This is why it is key to rise your static CR when you get very longer duration cams.

You desire a fast, complete burn of the air-fuel mix to make power

Engine – Power versus Torque

It appears that lots of people are confused about the relationship between power and torque.

“Which do I require more – power or torque – to go fast?” – It is a common issue of conversation with auto enthusiasts – but one that seems to be never-ending and commonly unresolved. In order to be able to suitably deal with the difficulty, it is important to have an knowledge of what the terms really mean.

Torque

Torque is basically a measure of the twisting force that is applied in an attempt to turn an object. It is a force that is applied to a lever arm, and is measured in Newton Metres (Nm). Newtons are a unit of force, and at the surface of our planet a 1kg object will put forth a force on the ground of 9.8N, due to gravitation. Torque is, actually, the product of the force and the length of the lever arm. Understood this way, it is clear that there are two ways of increasing torque. You can either rise the force or rise the length of the lever arm. Looking at an engine we can say that the lever arm is the stroke and the force comes from capacity. So, to rise torque, increase the stroke, or rise the capacity, or do both.

Power

Power is defined as the rate of doing work, and has units of Kilowatts (kW named after James Watt) or horsepower (old Imperial units).

Watt wanted to be able to rate the power production of his steam engines in order to advertise them. He decided that the most wise unit of power to weigh against them to was the rate at which a horse could do work. He tested the skill of a variety of horses to elevate coal with a rope and pulley and in the end settled on the description of a “Horsepower” as 33,000 foot pounds per minute.  In metric, the Watt is defined as the power to do one Joule of work per second. One horsepower is equal to about 746 Watts.

The relationship

Now, another aspect to realize is that power and torque are intimately related. With engines, power is the torque multiplied by the radial velocity.

Power (kW) = (Torque (Nm) x RPM) /9549
Power (hp) = (Torque (lb/ft) x RPM) /5252

As you can see torque and power are (almost) flip sides of the same coin. Increasing the torque of an engine at a particular RPM is no different as increasing the power production at the same RPM. Power is as informative and important in determining vehicle performance as is torque.