Why do rotary engines backfire

If you've noticed these signs while driving, you might be wondering what causes an engine to backfire. While there are many possible causes, we've compiled a list of the three leading reasons that engines backfire. Automotive engines are designed to operate with a precise ratio of fuel to air.

To create combustion, your car's engine needs a specific amount of fuel and air for each stroke of the cylinder. If it receives too much fuel and not enough air -- a condition known as running rich -- it can lead to backfiring. With an excess amount of fuel being pumped into your engine's combustion chamber, some of it may not be burned. And any remaining, unburned fuel will travel out the exhaust where it causes backfiring.

Two spark plugs are used to ignite the air-fuel mixture, helping to speed up the combustion process and ensure the majority of the fuel burns, and this forces the rotor to continue to rotate. Similar to the intake stroke, the rotor moves until exhaust ports are accessible, and the exhaust gases at a high pressure are then forced out as the rotor closes off the housing. This means that while intake is occurring on one portion of the rotor, a power stroke is also occurring, leading to a very smooth power delivery and a large amount of power in a small package.

One of the biggest advantages of the rotary engine was its size. The 13B engine of the Mazda RX-7 took up about one cubic foot of volume, yet produced a significant amount of power for its small proportions. Often in engineering, the simplest solution tends to be one of the best solutions. The rotary engine drastically reduces the number of parts required for combustion to occur, with just three main components spinning in a two-rotor motor.

The rotary engine has no reciprocating mass, like valves or pistons in a traditional engine. This leads to an incredibly balanced engine with smooth power delivery, and the ability to rev high without concern of things like valve-float. The Mazda RX-8 was the final production vehicle with a Wankel rotary, the 1. Whether or not the RX-8 lived up to the rotary name, we all shed a tear at the loss of this innovative and unique approach to internal combustion.

What dealt the final blow? The RX-8 was unable to meet Euro 5 emissions regulations, and thus it could no longer be sold in Europe after Though still legal in the states, sales had significantly dropped as the model had been around since Due to the long and uniquely-shaped combustion chamber, thermal efficiency of the engine was relatively lower compared to piston-cylinder counterparts.

This also often led to unburnt fuel leaving the exhaust hence the tendency of rotary engines to backfire , which is obviously as awesome as it is inefficient. By design, the rotary engine burns oil. There are oil squirters in the intake manifold, as well as injectors to spray oil directly into the combustion chamber.

Not only does this mean the driver must regularly check oil levels to keep the rotor properly lubricated, but it also means more bad stuff comes out the tailpipe.

And the environment hates bad stuff. Remember, intake and combustion are occurring simultaneously, but in very different locations in the housing. When backfires occur as your lawnmower idles or as you're turning off the engine, the most likely problem is that you're slowing your engine speed too fast.

Moving quickly across your yard builds up the engine speed, and if you shut it off suddenly, the engine could pump gas into your muffler where the gas could ignite. Slowing the speed gradually and allowing the motor to idle for 15 seconds before you turn off the mower can help reduce these backfires, says Briggs and Stratton. The problem also could be that your mower is overheating; if you suspect this, contact the manufacturer about ways to increase air flow to the engine.

Lawnmowers shouldn't backfire when you're trying to start them. This often is a sign that the mower is damaged in some way; for example, you might have run over a large rock or other obstruction.

Many mowers have safeguards in place to allow inexpensive items, such as flywheels, to break when the blade hits a large obstruction; these parts basically sacrifice themselves to save more expensive ones, such as the crankshaft.

When a flywheel is broken, your mower might stutter or backfire when you try to start it, but it won't completely engage, says Sci.