Fuel injection provides precise delivery system

It's not often we can be unanimous in our praise of regulations, but most of the significant features in today's motor vehicles result from laws.

Take fuel injection, for example, which has replaced carburetors in virtually every motor vehicle sold in countries where there are exhaust-emission or fuel-economy regulations because it allows a more precise delivery of fuel.

Precision is the name of the game in the continuing search for squeezing the last little bit of energy out of every drop of fuel. This not only makes sense from a mileage point of view, it ensures very little is left over to go out the exhaust as harmful emissions.

The carburetor was initially devised to mix air and fuel and deliver that mixture via an intake manifold to the cylinders of an engine. Now more than a century old, this device is still in use in less developed countries and on engines not covered by emission and other regulations, such as lawn mowers, outboard engines, power saws, motorcycles and stationary power plants. However, in many of these applications fuel injection is becoming more common.

The problem is not so much the design of a carburetor as the need for constant maintenance and adjustment. A properly designed and adjusted carburetor can be incredibly efficient.

Those atop a NASCAR race engine help produce huge horsepower and maximum use of available fuel. But they cost thousands of dollars and are literally rebuilt after only hours of use by incredibly accomplished technicians.

In the real world, carburetors are more commonly out of tune, gulping vast amount of fuel and allowing the majority of it to escape out the exhaust as unburned emissions.

One of the most common problems with carburetors is the need to supply a rich mixture at startup, to allow more fuel into the combustion chamber in order to assist that initial start. Carburetors use a device called a choke that dumps more fuel into the system and gradually backs off as the engine heats up - as long as it is adjusted properly. The problem is this adjustment does not last very long.

The next time you see an old car or truck going down the road with a dark smoke coming from the exhaust pipe - not a white or blue smoke, but a dark gray or charcoal coloured cloud - that is raw gasoline from a choke that has not closed.

With injection systems, fuel is measured and metered precisely and electronically. An exact amount of fuel is mixed with a precise amount of air depending on conditions - including startup.

Fuel injection systems have evolved over the years from a single-point system built into a carburetor atop an intake manifold to highly complex electronic systems that inject the fuel-air mixture into each cylinder individually under high pressure.

The early versions were called throttle body systems because they were simply a highly developed part of a carburetor that delivered the fuel-air mixture to a common manifold. From that initial entry point, the mixture made its way over varying lengths of distance to the cylinders - with a different amount getting to each.

Today, each individual cylinder gets its very own fuel delivery dependent on conditions and demand at that particular cylinder. Elaborate electronic devices measure and monitor each cylinder as well as atmospheric conditions, elevation and numerous other factors. They adjust for wear, fuel quality and other issues reducing, if not removing, the need for maintenance.

They sure don't build them like they used to.