Posted tagged ‘combustion’

Super Charger

September 28, 2011


Engines combust (burn) fuel and use the energy of that combustion to do work. The more fuel that is combusted in any given time then the more energy is available to carry out the engines task. Fuel requires air (or the oxygen contained within air) to burn so if there isn’t enough air mixed with the fuel it will not burn. This also means that the amount of air entering an engine determines how much fuel can be burnt and consequently how much energy (or power) an engine can produce. Superchargers are essentially an air pump designed to cram extra air into an engine allowing it to combust more fuel than would otherwise be possible.


Mercedes pioneered automotive superchargers on their race cars during the 1920’s. These were simple reciprocating compressors attached to the engine by an electrically operated clutch. A switch activated by the accelerator pedal turned the pump on when extra power (full throttle) was required. A flurry of engineering endeavor ensued in order to reign in Mercedes advantage on the racetrack. Within a few short years most of the basic designs for modern superchargers had appeared.


During the 1930’s superchargers were largely the preserve of marine engines, aircraft and race vehicles but gradually found their way into commercial diesel engines by the 1950’s. It has been common for truck engines to be turbo supercharged (a.k.a. turbocharged) for decades but car engines originally had difficulty in effectively employing this technology.


Superchargers mostly fall into one of two categories, mechanically driven superchargers and turbo superchargers driven by exhaust gasses. A third category is starting to make an appearance and that is electrically powered superchargers.


Turbo superchargers (a.k.a. turbochargers or turbo’s) are relatively compact, lightweight and efficient but suffer from turbo lag and heat stress. By turbo lag we mean the amount of time it takes for the turbo’s rotor to speed up to full efficiency. Some of the earliest turbo charged vehicles took so long for the turbo to produce a usable amount of boost that they were all but useless. Modern turbo chargers are much better in this regard but turbo lag is still a problem. Heat is another bane of turbo chargers. Exhaust gasses are extremely hot and can cause so much heat to build up in the turbo that oil will burn and congeal within its galleries leading to a bearing failure. This is why many turbo chargers have a turbo timer. The timer will cause an engine to continue idling for a few minutes after it is switched off allowing excess heat to be dissipated.

01-super charger schematic diagram

Mechanically driven superchargers usually don’t suffer from turbo lag and can often produce more boost than an exhaust driven charger (turbo). On the negative side they are generally bulky, heavy, and have a cumbersome drive mechanism (usually belt drive). Furthermore most chargers of this type have to supply air at all engine speeds and loads making them difficult to match various engine conditions precisely.

As our supercharger is electrically driven we have devoted an entire article to the advantages and disadvantages of this type.

Heat exchangers (intercoolers) are frequently used in conjunction with superchargers. Compressing air increases its temperature thus making it less dense. By re-cooling the compressed volume of air before it enters, density is increased allowing even more air to be forced into the engine. Intercoolers are more important for turbo superchargers as there are two heating sources present, the act of compression and heat from exhaust gasses both increase air temperature.

Idling Stop Technology | i-stop

September 16, 2011

Idle stop systems save fuel by shutting down a vehicle’s engine automatically when the car is stationary and restarting it when the driver resumes driving. Especially in urban areas, drivers often let their car’s engine idle at traffic lights or when stopped in traffic jams. Switching off the engine to stop it idling in these situations enhances fuel economy by about 10% under Japan’s 10-15 mode tests.

Conventional idling stop systems restart a vehicle’s engine with an electric motor using exactly the same process as when the engine is started normally. Mazda’s ”i-stop”, on the other hand, restarts the engine through combustion. Mazda’s system initiates engine restart by injecting fuel directly into a cylinder while the engine is stopped, and igniting it to generate downward piston force. This system not only saves fuel, but also restarts the engine more quickly and quietly than a conventional idle-stop system.

01-i-stop operation-operating principle of the i-stop-idling stop technology-piston position control

  • Piston stop position control and combustion restart technology

In order to restart the engine by combustion, it’s vital for the compression-stroke pistons and expansion-stroke pistons to be stopped at exactly the correct positions to create the right balance of air volumes. Consequently, Mazda’s ”i-stop” effects precise control over the piston positions during engine shutdown. With all the pistons stopped in their optimum position, the system restarts the engine by identifying the initial cylinder to fire, injecting fuel into it, and then igniting it. Even at extremely low rpm, cylinders are continuously selected for ignition, and the engine quickly picks up to idle speed.

Thanks to these technologies, the engine will restart with exactly the same timing every time and will return to idle speed in just 0.35 seconds, roughly half the time of a conventional electric motor idling stop system. As a result, drivers will feel no delay when resuming their drive. With the ”i-stop”, Mazda can offer a comfortable and stress-free ride as well as better fuel economy.


August 23, 2011

01-hydraulic hybrid system-Hydraulic hybrid vehicles-HHV-hydraulic motors to power wheels-accumulators to store the pressurized  fluid nitrogen gas 

Introduction To Hydraulic Hybrid Vehicles:

Hybrid vehicles use two sources of power to drive the wheels. In a hydraulic hybrid vehicle (HHV) a regular internal combustion engine and a hydraulic motor are used to power the wheels.

Hydraulic hybrid systems consist of two key components:

  • High pressure hydraulic fluid vessels called accumulators, and
  • Hydraulic drive pump/motors.

Working of Hydraulic Hybrid Systems:

01-hydraulic-hybrid-retrofit-hydraulic hybrid system-HHS-regenerating braking energy

The accumulators are used to store pressurized fluid. Acting as a motor, the hydraulic drive uses the pressurized fluid (Above 3000 psi) to rotate the wheels. Acting as a pump, the hydraulic drive is used to re-pressurize hydraulic fluid by using the vehicle’s momentum, thereby converting kinetic energy into potential energy. This process of converting kinetic energy from momentum and storing it is called regenerative braking.

The hydraulic system offers great advantages for vehicles operating in stop and go conditions because the system can capture large amounts of energy when the brakes are applied.

The hydraulic components work in conjunction with the primary. Making up the main hydraulic components are two hydraulic accumulator vessels which store hydraulic fluid compressing inert nitrogen gas and one or more hydraulic pump/motor units.

The hydraulic hybrid system is made up of four components.

  • The working fluid
  • The reservoir
  • The pump or motor
  • The accumulator

The pump or motor installed in the system extracts kinetic energy during braking. This in turn pumps the working fluid from the reservoir to the accumulator, which eventually gets pressurized. The pressurized working fluid then provides energy to the pump or motor to power the vehicle when it accelerates. There are two types of hydraulic hybrid systems – the parallel hydraulic hybrid system and the series hydraulic hybrid system. In the parallel hydraulic hybrid, the pump is connected to the drive-shafts through a transmission box, while in series hydraulic hybrid, the pump is directly connected to the drive-shaft.

There are two types of HHVs:

  • Parallel and
  • Series.

Parallel Hydraulic Hybrid Vehicles:

01-hydraulic hybrid cars-HLA system-pump mode to motor mode-parallel hydraulic hybrid vehicles-nitrogen accumulator pressure 5000 psi

In parallel HHVs both the engine and the hydraulic drive system are mechanically coupled to the wheels. The hydraulic pump-motor is then integrated into the driveshaft or differential.

Series Hydraulic Hybrid vehicles:

01-hydraulic hybrid vehicles-combines regular internal combustion engine- hydraulic motor as a accumulator-kinetic energy into potential energy to drive the vehicle

Series HHVs rely entirely on hydraulic pressure to drive the wheels, which means the engine does not directly provide mechanical power to the wheels. In a series HHV configuration, an engine is attached to a hydraulic engine pump to provide additional fluid pressure to the drive pump/motor when needed.


  • Higher fuel efficiency.  (25-45 percent improvement in fuel economy)
  • Lower emissions.  (20 to 30 percent)
  • Reduced operating costs.
  • Better acceleration performance.


August 23, 2011

02-direct-injection-engine-disi engine-gasoline engine

In developing the DISI engine, we aimed to cool the interior of the cylinder as much as possible by promoting fuel vaporization and uniform mixing of atomized fuel and air. This produces a high charging efficiency of the air-fuel mixture and a high compression ratio, which results in significant improvements in both torque and fuel efficiency.

Characteristics of the direct injection engine:

  • Fuel is injected from a tiny nozzle into a relatively large cylinder, so it has a high latent heat of vaporization, which efficiently cools the air within (in-cylinder cooling effect).

  • The air temperature in the cylinder decreases, which means:

  • (1) more air may be charged into the combustion chamber, which produces increased torque.

  • (2) the engine is less prone to knocking. This contributes to increased torque, and enables a higher compression ratio that also contributes to good fuel efficiency.

In a direct injection engine, however, the fuel skips the waiting period it would have to endure inside a standard engine and instead proceeds straight to the combustion chamber. This allows the fuel to burn more evenly and thoroughly. For the driver, that can translate to better mileage and greater power to the wheels.

In the past, direct injection posed too many technical hurdles to make it worthwhile for mass market gasoline automobiles. But with advances in technology and greater pressure to make cars run more cleanly and efficiently, it looks as if gasoline direct injection — or GDI as it’s referred to in industry lingo — is here to stay. In fact, most of the major car manufacturers make or plan to soon introduce gasoline cars that take advantage of this fuel saving and performance enhancing system.