Your local diagnostic expert
New generation diesels a speciality
UNDERSTANDING MODERN MOTOR VEHICLES
Modern Vehicles and the need for competent technicians
Listed below are some of the computer controlled systems that you will find on the average
modern car along with a basic synopsis of how they work.
The ECU controls almost every aspect of the engine, starting with the measurement of air drawn into the engine,
the correct amount of fuel to mix with that air, through to the generation of the spark at the plug and the timing
of the controlled combustion generated, it then analysis the quality of the combustion by way of measuring the
exhaust gases produced and not content with that it further analysis the correct operation of the catalytic
convertor and therefore the emission released from the exhaust pipe.
Note at high engine RPM the spark plugs and injectors are operating at anything up to 50 times per second.
The ECU continuously monitors the speed of all four wheels and cross checks one
against the other, it has the capability of over riding the brake pressure applied by the drivers
foot on the brake pedal, holding or releasing that pressure at individual wheels or in fact
pressure generation independent of whether the foot pedal is depressed or not.
The ECU is capable of carrying out all of the above calculations and actions up
to 14 times a second.
The ECU monitors the rate of de-acceleration through sensors fitted about the
car, once this rate has been acceded the relevant airbags can be deployed within 5thousanths of a second along with
the seat belt pre-tensioners.
The latest systems have become proactive instead of reactive, what I mean by this is that the new systems weigh you
when you sit in the car, there is a sensor fitted to the seat so the computer knows how far away you are from the
steering wheel and there can be a miniature camera set in the “A” pillar so the ECU knows how tall you are, armed
with all this information and combined with a radar sensor fitted to the front of the car (behind the grille) The
ECU works out the current vehicle speed and the rate at which you are approaching the obstacle in front of you, it
then knows that you are not going to stop in time, therefore it knows you are going to have the accident before you
have had it. It will then take advance measures of deploying the seat belt tensioner’s and in fact the airbags in
relationship to your body mass and the speed of the approaching collision this make the airbag system far better
suited to the individual driver and accident.
Once you have had the accident the ECU will also automatically shut off the fuel supply, activate the hazard
warning lights, turn on the interior lighting, unlock the central locking and if the vehicle is built with an
internal mobile phone it will send out a signal to the emergency services.
I have only briefly covered 3 ECU’s within the modern vehicle and to put this
into prospective the average family car will currently have in excess of 30 ECU’s and a top of the
range vehicle can have in excess of 200.
All of these ECU’s will communicate with each other and share information (I.E if
the ABS system has a fault the Engine Management may well limit full power as a result). I hope
this highlights some of the technology within the modern vehicle and therefore the importance of
having fully trained technicians working on your vehicle.
Please contact Rebecca or Elaine at Tisbury Motors on 01747 870258 who
will be more than happy to deal with your enquiry.
Courtesy cars are available please mention this at
the time of booking so that recepton can factor this in to suit your requirements.