Wednesday, 31 August 2016

New concepts: new engines

The research carried out in recent years by petrol engine manufacturers has focussed on the battle to lower CO2 emissions (considered a cause of global warming).
Compliance with the magic figure of 130 gr/km valid until 2020 has got the engine development departments working flat out. This figure is the only one that has led to a radical rethink of the modern engine, as the Euro 4 to Euro 6 standards do not significantly differ as regards the polluting gases measured for approval (CO, HC and NOx).

The Lambda 1 petrol engine is a high generator of CO2, in fact in the catalytic converter two oxidations and a reduction occur, CO2 being a large part of the results.

Today, the only way to reduce CO2 emissions lies in reducing consumption. At the moment there is no system or device that assists the engine in lowering this emission.

Thursday, 18 August 2016

Types of active suspension (l). Hydroactive 3 for Citroën C5

In an ideal suspension system, the position of the wheels would not change with respect to the body. The purpose of the various active suspension systems is to control the stiffness of the damping.

In hydraulic and air systems, the height of the vehicle is also controlled depending on variations in weight and road conditions. Electronic and electro-mechanical systems are required for this. In this and subsequent posts, three examples of this type of suspension are going to be described: the Citroen C5 Hydroactive 3, the Audi A8 Air suspension and the VW Golf DCC Adaptive Chassis Control.

In this first post, we are going to look at the Hydroactive 3 suspension.

Hydroactive 3 from Citroën C5

This type of suspension allows the distance to the ground to be varied automatically depending on speed. There are two positions, sport and comfort, which automatically change the stiffness of the damping. These changes give greater stability due to the lowering of the centre of gravity by 15 mm at the front and 11 mm at the back, which reduces fuel consumption. On poor roads, the system can raise the height of the vehicle by up to 13 mm.

Hydroactive 3 facilitates choosing between the two suspension options, it allows switching, alternately and in real time, from a soft setting, which gives priority to comfort, to a hard one to improve stability, while taking into consideration the driving style and the road profile at all times.

The main elements involved in the system are:

1. Integrated hydroelectronic block.
2. Front bearing elements.
3. Front stiffness regulator with its sphere.
4. Front height sensor.
5. Rear hydropneumatic cylinders
6. Rear stiffness regulator with its sphere.
7. Rear height sensor.
8. Control unit.
9. Steering angle sensor.
10. Hydraulic fluid tank.
11. Accelerator pedal position sensor.
12. Braking pressure sensor.
-A simplified hydraulic system.

Tuesday, 16 August 2016

The required and correct maintenance of the particulate filter (FAP)

In 2010, the Euro 5 standard came into force that requires car manufacturers to install a Particulate filter (DPF or FAP), among other elements, in the exhaust systems of diesel engines.
The purpose of the FAP is to store soot particulates generated by the incomplete combustion of the fuel, which drastically reduces the harmful particulate levels emitted to the atmosphere.

The FAP is a particularly effective mechanical filter which is made up of honeycomb type cells that trap the particulates emitted during combustion. It can retain more than 99% of the combustion particulates.

Particulate filter

To regenerate the Particulate Filter and prevent internal saturation with soot, the system carries out a regeneration process. This process is activated when certain technical temperature and running conditions are fulfilled. When these conditions are met, the engine control unit starts this process by acting on the injection system in order to raise the temperature inside the particulate filter, and thus burn the soot accumulated in it.

Tuesday, 2 August 2016

How does the Valvematic system work?

The various car manufacturers’ race to develop systems to reduce emissions, consumption and increase performance of their engines has led the Japanese Toyota brand to develop its Valvematic intake valve variable lift control system.

The Valvematic system, in coordination with the VVT-i dual system (variable valve timing), carries out the continuously variable intake valve lift control, as well as controlling the actuation angle of the intake valve, the full opening of the throttle valve and the synchronisation of the intake valve in accordance with engine conditions. This improves engine performance and saves fuel. The intake valve lift varies between 0.09 mm and 11 mm in accordance with engine needs.

One of the particular features of this system is that the intake manifold throttle is fully opened (like a diesel) in order to reduce pumping losses at all engine speeds. The Valvematic system will act based on the information that the ECM (engine control module) has collected from the TDC (engine rpm) and NTC (coolant temperature) sensors, the exhaust and intake camshaft position Hall sensors, from the MAF (Mass Air Flow) sensors and from the intake throttle position sensor and through the EDU (servomotor control unit), and it will open the intake valves between the aforementioned 0.09 mm and 11 mm according to needs so that the engine runs at the speed required by the driver.

This system requires the use of a vacuum pump to provide the correct vacuum to control the brakes, this is because the throttle is fully open and there can be no difference in pressure between its faces.

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