Cartalk Wednesday

More thoughts on computers used in cars...

I'm not poo-poo-ing on technology in cars. Computers have contributed many wonderful things to the automotive industry. Digital FM tuning alone has probably saved lots of lives by letting people see more clearly what they're tuning at a quick glance, instead of a hard to read dial. (because you know for a fact that someone isn't going to be satisfied with leaving it on one station, even in the 1950s.)

And that's what this post is about. One of the most remarkable advancements of automotive industry starting mostly in the 80s is computer controlled fuel injection.



Before mechanical fuel injection, the only way a working engine would know how much fuel it needed from the gas tank to run was correctly tuning a mechanical device called a carburetor. By adjusting this device mechanically, it would change both how air and fuel was 'pulled' up into it before it was mixed and fed to the ignition chamber of the engine. It would be adjusted to account for weather changes, different fuel grades, performance, altitude, and other specific reasons, but sometimes setting it up for one condition was detrimental in other conditions. You could, for example, set a carb up to pull in lots of air and fuel because you're going to run the engine really hard racing.... but then the car won't start properly because it can't begin the combustion process with the fuel/air mix volume that high. (so in this example you'd adjust it after you already started it).

Anyways, the alternative to this was/is fuel injection in cars, and mechanical fuel injection has been around for a while before the 80s. The biggest advantage is that it can be far more precise than a carb, and therefore get more power and efficiency from the same amount of fuel. In fact, it was mostly used in fighter plane engines before the jet engine revolutions. But as far as cars, it saw very limited use because they weren't very flexible, tunable, or useful in the same way. It was an exotic car feature until the advancement of 'electronically controlled' fuel injection. Instead of being controlled by a computer, it was electronically controlled by voltage readings from an electrical element, or the behavior of an electromechanical sensor. These systems were used as far back as the 50s, but of course, electrical components were primitive, sensitive, expensive and not as flexible as hoped.


as computer processing power became cheaper, revisiting fuel injection made more sense. A computer takes readings from that sensor, digitizes them for analysis, and then decides how to control the operation of the engine combustion on some level.

These computers are super simple instruction chips that are physically robust (for weather conditions), run at low clock speeds for long term reliability, and are usually programmed in low level assembly- or even lower machine code.

In fact, these days, companies have been trying to reverse-engineer these computers in order to tune the engine in different ways. My car has been 'reprogrammed' by such a company to focus on performance and to adjust the engine for the parts I've added to it.

This is where worlds start colliding. Car manufacturers guard their code and engineering in the car computers as MS does with Windows code. This naturally infuriates proponents of 'open source,' who want to know exactly how the computer in their car works. In fact, there's a group of open-source tuners out there for some of the computers in cars that they believe they have cracked.

Why would you do this? Couldn't you just buy your own computer to control the car? The answer is yes, but not something like a PC. Purpose built vehicle computers that can be customised for any car start around $2000, and you program and install it yourself. These things are extremely powerful, but usually ignore emission controls because they are used mostly in racing cars off-the-road.

Besides, the car computer stores its instructions in a flashable ROM, and the computer in most cars since the 90s is actually very powerful and customisable. As long as you've reverse engineered it successfully. Good luck getting an API from a car manufacturer...