Last week we took a closer look at injection in diesel engines. We’ll look at injection in petrol engines this week.
Carburettors do their job well enough — even today, fans of carbs will tell you that a well-tuned carburetted engine will outperform a similar fuel-injected engine. While this may be true for outright performance, the fuel injection will nose ahead on emissions and overall fuel consumption.
Back to the future
Fuel injection in gasoline engines has been around for a while — the Mercedes-Benz 300 SL that went on sale in 1954, had a fuel injection system. However, the 300 SL was to 1954 what the Bugatti Veyron is to 2005. Five decades in the future, we might even be able to buy a 1000 bhp hatch for a daily drive. Of course, today’s 20-somethings hoping for mile-long burnouts at every stop on their commute will be septuagenarians by then, so they won’t have an office to commute to. We’ll probably also have legislation that makes that much fun illegal.
Today, almost all petrol engines run fuel injection, right from small bikes with 100 cc capacities (in developed markets) to engines like the 8383 cc one in the Dodge Viper.
Fuel injection is controlled by a microprocessor that sends the right amount of fuel to the cylinder through the injector. The fuel injector is an atomiser like a mosquito spray. The smaller the droplets of fuel, the better they’ll mix with the air going into the cylinder, and the combustion process will burn the fuel completely, meaning optimum power and emissions.
The injectors can be placed in different positions; older systems have injectors in the intake system, just before the intake valve. The intake valve is what lets fuel and air into the cylinder. Placing the injector here helps the fuel mix better with the air.
A curious bit of trivia is the fact that Mitsubishi is the first company to have put direct injection in a gasoline engine on a production car. One of the models was the Galant Fortis, which we know as the Lancer.
However, the Lancer Evolution, Mitsubishi’s flagship car and a performance icon, still runs indirect injection. This is probably because the ‘Evo’ has been a perennial favourite of the performance tuning fraternity. By upgrading the injectors, you can deliver more fuel to the engine, which gives you more power. Direct injection won’t give you this freedom.
...vs better fuel economy
What direct injection will give you is very good fuel economy and emission levels, which is why manufacturers are now moving to this technology. Audi’s FSI is one of the most well-known of the lot. If the injector introduces fuel directly into the cylinder, there are no losses due to evaporation, and only a minute amount of fuel can be introduced into the cylinder at idle or when the driver is braking.
The precision with which fuel can be metered gives direct injection its edge, although if you want any performance modifications from this system you might want to trade in that spanner for a scanner.
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