Fully-Integrated: Understanding Automotive Electrical Systems

Text by Dmitriy Orlov

In the Beginning…

Before electronics and computers, vehicles were simple, mechanical machines; engines had to be tuned and dialed in by hand, drivetrains were unsophisticated and the seat belt was the only real safety system.

Modern electronics and increasingly powerful microprocessors have enabled cars to be more efficient and dynamic than ever before. Just about every mechanical system is now supplemented with electronics that provide feedback, logging and control capabilities. Without these systems, the level of power and performance found in today’s cars would not be possible; furthermore, vehicles would lack the cutting-edge safety features and amenities that are now standard.

Automotive electrical systems consist of smaller, individual networks of wiring harnesses, sensors and modules that communicate with each other, as well as the main Engine Control Unit (ECU). In this article, we will take an in-depth look at some of these electronics systems and explain how they work behind the scenes while you are driving.

Powertrain Control

The ECU is the brain of the car and controls virtually all aspects of the powertrain. Sensors monitor engine operation and provide the ECU with vital feedback and data to ensure safe, reliable operation under all driving conditions.

Ignition timing control is one of the most basic functions of the ECU and relies on the exact positions of the crankshaft and camshaft(s) to achieve optimal power output; this allows the engine to be more dynamic and variable. Depending on the design of the valvetrain, the ECU is capable of running a motor smoothly at idle and more aggressively at higher RPMs, due to the level of control that is possible with sophisticated electronics. In forced induction applications, the computer can optimize power delivery through throttle mapping and regulating boost pressure.

Many modern cars are "drive-by-wire,” meaning the traditional throttle cable setup is replaced by a fully-electronic system. When the accelerator pedal is depressed, a signal is sent to a small electric motor on the throttle body, which opens the throttle plate. Drive-by-wire systems allow the ECU to more precisely control engine operation.

On some performance cars, drivers can change the way the engine responds by simply pushing a button; engine output can be increased for spirited driving or decreased for more traction in inclement weather. In motorsports and performance applications, the factory ECU is often replaced with a fully-programmable aftermarket unit that allows the user to tune for a wide variety of parameters to maximize an engine's performance.

In the past decade, transmission design has greatly benefitted from electronic integration, such as dual-clutch and CVT gearboxes. The ECU determines the best shift point based on input from various sensors, and because computers can react quicker than humans, the performance and response of electronically-controlled transmissions far surpasses that of traditional ones. In modern all-wheel-drive systems, the ECU can control the differentials to distribute power to the wheels that have the most grip, ensuring steady and consistent power delivery.

With the advent of hybrid cars, electronics are more important than ever – the ECU must monitor a vehicle’s power demands and switch between the electric motor and the engine on the fly. Additionally, opportunities to recharge the batteries, be it through regenerative braking or starting up the engine, are recognized and controlled by the ECU.

Not only does a computerized powertrain optimize performance and efficiency, it is able to detect mechanical problems and early signs of component failure. Scan tools communicate with the ECU through a diagnostics port and are able to pull codes, as well as clear Check Engine Lights. This allows problems to be quickly and easily pinpointed.

Chassis Control

As with the powertrain, all major chassis systems can be monitored and controlled by the ECU, if the hardware supports it. This integration stabilizes the vehicle, changes its handling characteristics and makes it safer.

Instrument cluster of the Mitsubishi Evo X shown here displays a graph that shows where the power is being diverted to in relation to the wheels. When you enter a corner at high-speeds, you'll notice the power is diverted to the inside front wheel and the outside rear wheel for optimum traction and stability.

Many high-end performance and luxury vehicles feature dynamic suspension control, which allows the driver to electronically change dampener settings or adjust ride height from the cockpit. Some designs even eliminate sway bars, instead using an array of sensors to monitor and automatically compensate for body roll, without any input from the driver. These aids result in superb handling and allow the driver to push the car harder.

Dynamic steering systems, much like suspension systems, can change the response and ratio of the steering wheel, depending on vehicle speed and the specific driving situation. Sensors relay feedback from the ECU to the steering module to make the necessary adjustments.

Advancements in brake systems have also been made due to modern electronics; the introduction of ABS and stability control has made vehicles safer than ever before. Speed sensors can monitor each wheel individually and apply just the right amount of brake pressure needed to maintain optimal traction, and in extreme situations, regain vehicle control.

Safety & Emissions

By collecting data every millisecond, computers have drastically increased the safety of cars. Stability control and braking systems are optimized to provide vehicle response and traction in case of emergencies. Tire Pressure Monitoring Systems (TPMS), now standard on all vehicles, ensure that all tires are properly inflated, which is critical for safety as well as fuel economy.

Airbag systems are also linked to the ECU and utilize special sensors to detect a crash and trigger the airbags. The computer will also shut down the engine to prevent fires. Some vehicles are linked to concierge service providers, such as OnStar, and will automatically send any relevant data and the location of a vehicle in distress, allowing for much quicker response times by authorities and emergency crews.

Environmental concerns have necessitated increasingly efficient engines with reduced emissions. Oxygen sensors measure the air/fuel ratio of the exhaust and dictate how the ECU will adjust the fuel mixture for optimal performance, economy and the lowest possible emissions.

Entertainment & Comfort

The vast majority of on-board creature comforts and entertainment systems have been computerized as well. Much of the information collected and calculated by the ECU, such as MPG, outside air temperature and other statistics, is available to the driver via in-dash displays or computer screens.

Center consoles now feature full entertainment and multimedia systems and can even connect to the internet and integrate with mobile devices. Climate control has also become much more sophisticated and intuitive, with multi-zone temperature and comfort settings that allow passengers to create their own personalized areas within the vehicle.

The Future

As technology continues to improve, automotive electronic systems are becoming more and more state-of-the-art, and are beginning to take driver error out of the equation. Autonomous vehicle technologies are already being tested that would allow cars to drive themselves; fully-autonomous transportation has the potential to further optimize the use of cars by making it quicker and easier to commute. The technology for a car to self-park already exists, as well as the ability to monitor blind spots and warn drivers of obstacles in the road.

Vehicle networking systems will make it possible for a car to detect other cars’ positions to avoid collisions; this technology has already been implemented and could very well become standard equipment in the near future.

All of these exciting, new automotive technologies aim to improve the overall driving experience through increased safety measures, more comfort and better economy. The downside, many enthusiasts argue, is that fancy electronics and driving aids are no replacement for true driving skill and are making modern cars boring and predictable. While this might be true, there will always be older, more unforgiving cars to play with.

Previous Building Blocks - The Basics - Articles

Stopping Power: How the Brake System Works

Putting the Power Down: Wheels, Tires, Suspension & Steering

Power into Propulsion: How the Transmission & Driveline Work

RPM to MPH: How Car Engines Work


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auto body repair shop1/28/2014

Nice Post
If we go with a standard auto repair shop then we maintain our car for a long time.

Avi Ez8/29/2013

I had trouble with my car's electrical system in the past. I tried researching information on this at many auto shops. I recommend having your auto repair at Boykin Auto in Thousand Oaks California. They were friendly and informative.
Check out their website.

Srtacclaim's Profile Image

ya buddy

Rockysds's Profile Image

thats whats up- Reppin