Ecu's Vs Carburettors

[sanjsanj]

Can someone explain why the vast number of electrical sensors combined with an ECU make better engines than the old carburettor systems?

 

How does it lower fuel consumption and emissions?

[Willie Krashitt]

Quite simply, a carburettor is a very basic device that mixes the fuel and air together. The various jets, emulsion tubes, air corrector jets etc in the carb do a pretty good job of delivering the mixture to the engine, but cannot do the very rapid adjustment of the air -fuel ratio that enable a 3-way catalyst to function.

(The catalyst needs the air fuel ratio to be alternately slightly 'rich' and 'lean' cycle by cycle in order for it to work)

Cold starting requires a 'choke' - an extra plate to restrict airflow, so large amounts of fuel are poured into the engine, some of which will then burn. The rest goes out the exhaust unburnt. In addition carburettors are very altitude dependent - get the fueling right at sea level, and the engine will run very rich when going up a mountain.

 

The modern ECU controlled fuel injection system with its various sensors allow much more precise air-fuel ratio control for the engine across almost all operating conditions, from -30