In the ever-evolving world of cars, the carburettor has gone the way of the three-speed gearbox, hand-wound windows and cross-ply tyres.
Today, there’s no new car sold in New Zealand using a carburettor – the device for mixing fuel and air that’s as old as motoring itself. But there are heaps of vehicles on the used market still using the good old carb – and will be for years to come.
Electronic fuel injection (EFI), as in Chev LS7 (above), is to an engine what the computer was to office workers who had been slaving away with typewriters, carbon paper and bottles of Twink.
Fuel injection does the job better and more efficiently, end of argument.
Computer-controlled fuel injection plays an important role not only in tuning for power, but for good economy, low emissions and driveability.
In their day, carburettors worked very well, benefiting from many years of refinement. They were quite efficient and accurate, but not a match for today’s fuel injection.
Those who like to tinker with cars mourn the passing of the carby, which was generally simple to understand, maintain and modify at home, and could be swapped from one engine to another without a lot of bother.
On the other hand, multiple carburettor set-ups could be temperamental and difficult to tune. Enthusiasts and racing team managers alike coveted good carb tuners.
The doors were opened to the universal use of electronic fuel injection by the need to comply with stringent emission control laws, requiring a catalytic converter in the exhaust system. Converters could quickly become ineffective when teamed with carburetted engines because a carb could not keep the air/fuel mixture sufficiently precise.
A slightly rich mixture was poison to a catalytic converter.
A benefit for car owners is that today’s fuel injection systems are very reliable and require little servicing, in contrast to carburettors that usually needed adjustment or other work during regular maintenance.
When EFI does play up, the cause can usually be quickly located using computer-based diagnostic tools that plug in to the system, lowering labour costs.
In today’s systems, an electronic engine control unit calculates the mass of fuel to inject, which is then injected by an electronic solenoid.
By contrast, a carburettor directs the induction air through a venturi, a restricted air inlet that produces a drop in pressure causing fuel vapour to be drawn from a bowl.
As more air enters the engine, a greater pressure difference is generated, and more fuel is supplied to the engine.
Getting better performance from carburettors was largely a matter of replacing their jets.
In a fuel injected world, the controlling computer program has to be remapped, a process now well understood and used to spectacular effect by good tuning shops. Alternatively, some modifiers fit different performance “chips”.
Don’t worry if the used car you’re considering is fitted with a carburettor. It served us well for many decades and there are still plenty of mechanics able to tune and repair them, and a great parts infrastructure.