It wasn’t so long ago that the most powerful cars had horsepower ratings in the 375 to 400 HP range. Today, it’s hard to believe that horsepower ratings like this are actually pretty average. Last year, drivers searching for cars with 600+ horsepower on tap, an unheard of amount of power 50 years ago, had 18 models to choose from. Even boring commuter cars are posting power specifications in the 300-350 hp range.
And they are more efficient too. Back in the 60’s and 70’s, the high horsepower cars delivered terrible gas mileage. Most of the cars with big block engines were rated in the 12-14 MPG range. And for the tractor-trailer trucks, they could post mileage in the 4-6 MPG range. It was a simple formula back then: If you wanted lots of horsepower, you gave up lots of gas mileage.
Today, things have changed quite a bit. Since then, the EPA’s median measurement of miles-per-gallon over all the currently sold cars has doubled, from 14 to 29. At the same time, the engines in them has shrunk 43% in size. How did engineers pull off this off? It wasn’t a single design breakthrough. It was a lot of new techniques and technologies. Let’s look at a few of them:
In the old days, cars had carburetors that mixed gasoline with the air being pulled into the engine. This created a combustible mixture that just needed a spark in the combustion chamber to get things rolling. Back in the 1960s, a new technology was developed that shot a mist of gasoline directly into the cylinders. It was called fuel injection and it was much more efficient than carbureted cars. At first, fuel injection was accomplished by complex, mechanical injection systems that didn’t prove to be terribly reliable. Today’s cars utilize fully electronic systems that are fine-tuned to so that little gas is wasted in the combustion process.
Consider that the 2017 Dodge Challenger puts out 707 horsepower but can deliver 22 MPG. It doesn’t seem possible that a big V8 engine could do this. Well, it isn’t a V8 engine, all the time. It’s done via cylinder deactivation, a technology programmed to shut down four of its cylinders when they aren’t needed. Essentially, when your 707 hp car is just cruising along, a computer shuts down four of your cylinders so you are instantly driving an economy car. When more power is needed, the other cylinders kick in.
The real miracle comes in the smallest Jeep engine, a little four-cylinder, 2 liter package that makes close to 300 horsepower. 300 hundred horsepower? The huge power to weight ratio of these small engines comes from turbocharging. Turbochargers are fan-like devices that use the energy of the exhaust gases to drive more air into the engine cylinders. This in turn creates more power.
Some manufacturers are building turbochargers that are quite advanced. Mazda, for example, is now installing their Dynamic Pressure Turbo (DPT) system on performance versions of their models. According to Hiley Mazda of Hurst, a local Mazda dealer in Hurst, TX, DPT is the world’s first turbocharging system that is able to vary the degree of exhaust pulsation depending on the speed of the engine.
And they are lighter, too
Finally, cars on a relative basis have become quite a bit lighter. The baseline Dodge went from roughly 4,000 pounds in the 1970s to about 3,200 pounds today. This has been accomplished by using lighter materials. Engine blocks and body panels changed from iron to lightweight aluminum alloys. Intake manifolds and other engine components aren’t even metal now, they are made out of advanced theromoplastics. And the really expensive cars? They are veined with copious amounts of carbon fiber.
Earthgarage – Greener Car. Fatter Wallet.