Why aren’t the engines in your typical production car 2 stroke?


Why aren’t the engines in your typical production car 2 stroke?

In: 4

Two stroke engines are light and simple, but weak and inefficient. The overlapping intake and exhaust stroke makes both processes ineffective, and they don’t get the full power out of the fuel in a dedicated power stroke.

Four stroke engines are much more complicated and physically larger, but easily beat a two stroke in any application where the sheer size isn’t a problem.

A 2-stroke engine can’t fully clear the cylinder, so there’s a lot of combustion products leftover in the cylinder. There’s *enough* oxygen to produce the combustion necessary, but you are limited by how much fuel you can add because it’s just not clean air. You’re always going to have unburned fuel, too, which is both less efficient and bad for the environment. However, the engine is simpler to run and simpler to fix.

A 4-stroke engine includes an extra stroke to completely blow out almost all of the gas in the cylinder and then refill with completely fresh air. That gives you a much more efficient engine that can use more fuel per stroke *and* burn most of that fuel, so you get a cleaner burn and more power. That’s *way* better for the environment, better for your gas mileage, better for your engine maintenance, just generally better for everything. The downside is that the engine is more complicated.

For a lawnmower that you’ll run for an hour or two a week, you want simple and sturdy and easy to work on in your garage, and you want it cheap. Paying a bit extra for an extra gallon of gas every other month isn’t a big deal.

For your car that you will be driving for many hours a week and which uses a ton of gas, and for which you are already committed to pay a lot for, you want it to be clean, efficient, and last for a very long time. You probably aren’t going to be doing a ton of engine work in your home so if you’re already paying for someone else to maintain it, you might as well make it the best that you can (within reason and affordability).

Many auto rickshaw taxis in India are still 2 stroke. The air pollution in the cities is wonderful.

Mostly because of the EPA. I love 2-stroke engines and my daily commute would be a lot more fun with a 2-stroke wound all the way up 😉