In the last few decades, we have seen vehicle technology advance rapidly. We went from carburetors in the 1970’s, and 80’s to single point throttle body injection, then multi-point fuel injection, after that came sequential and finally direct fuel injection.
In part, this shift in thinking was caused by the precise requirements of catalytic converters. The last commercially available carbureted vehicles were sold in the US in 1994. Carbs can still be found on new motorcycles today as they have a lower electrical requirement.
Carburetors have existed since the invention of the first gasoline-powered motor car. Austrian inventor and engineer Siegfried Marcus created the world’s first petrol-powered four-cycle engine and fitted his own carb to deliver fuel to the engine. The concept then is not new. But surprisingly, for such an old concept, there are still occasions when you would choose to fit carbs over fuel injection.
In this article, we’ll list the benefits and drawbacks of both fuel injection and carb fed engines.
Let’s start with the older technology, the carburetor. The carburetor blends air and fuel into a proper ratio for combustion. Fuel is atomized in air so that it can combust rather than fill the engine void and cause misfiring.
Although all replaced in modern vehicle manufacturing, some planes still have carburetors, and small engine applications like gardening equipment or snow blowers still ship with carbs.
- Cost – Carburetors are still cheaper than fuel injection, and retro fitting fuel injection can be prohibitively expensive.
- For vehicle restorers and builders of concours vehicles, carbs were fitted to the vehicle at the factory, and so it is more period correct to fit carbs than to retro-mod the vehicle to run on fuel injection.
- Carbs are simple and easy to set-up, requiring an only a little theory. Electronic injection requires a diagnostics computer to adjust. They also require no return lines for fuel.
- Carbs are user adjustable. There are some reasons a user might want to adjust a carb, whether it be for performance, to smooth out misfires, knocking, a tendency to stall or poor idling. Carbs can also be adjusted to run leaner or richer as needed using a built-in choke or fuel enrichment device.
Adjusting a carb to draw more fuel thanks to the air pressure can also reduce internal engine temperatures and exhaust gas temps.
- Because carburetors are a physical, mechanical device, usually placed in an accessible spot, they are easy to maintain and repair by DIY mechanics.
- Carburetors only offer an approximation of the right air to fuel mixture and environmental differences can alter performance. They are less accurate than fuel injection controlled by a computer.
- They do not auto adjust for different altitudes, temperatures, and circumstances which fuel injected systems can.
Fuel injection is a more precise process. This precision has several performance benefits:
- Lower emissions as the right amount of air and fuel are combined, rather than dumping in excess fuel that is only partially combusted or could flood the engine.
- Fuel economy is increased thanks to a more effective injection method that is monitored by several external sensors
- The power curve of fuel injected engines is broader, and so it is said that they produce more peak power. The torque band, when measured, is also broader and this is what drivers feel when moving off
- There are less moving parts, which in theory, means fewer things to go wrong
- Motorists no longer need to adjust the air-fuel ratio using a choke, fast idle or enrichener device. These would often be forgotten about, and once the engine is up to temperature, it can cause damage to pistons and valves due to the overly rich fuel.
Fuel injection isn’t perfect though and does have some downsides.
- It is more expensive to fit fuel injection to a car versus a carburetor. The system requires numerous components, a fuel injection specific cylinder head and return fuel lines fitting.
- The installation of fuel injection to a car that was originally fitted with carbs is complicated and requires an ECU to run the injection as well as severe mechanical modifications and fabrication.
- Because fuel injection is controlled by a mixture of sensors and computers, it is less DIY friendly and requires diagnostic equipment.
Diagnosing problems on modern fuel injected engines is more involved thanks to the increase in components associated with the install.
Tuning has to be done by a technician and in some cases requires components soldering to a cars ecu.
Conclusion: The winner?
It isn’t possible to say whether you should choose carbs over fuel injection because each person’s requirements and needs are unique to them. If you are building a 1960s muscle car back to showroom condition, you’d likely choose carbs for their period correctness.
However, resto-modders will appreciate the performance and economy enhancements of fuel injection. Ultimately, you’ll have to decide for yourself, but we prefer our small engined mowers and brush cutters to be carb fed and our cars to be fuel injected.