How Does A Turbocharger Work?
You’ve heard the word “turbo” tossed around a lot, especially by performance car enthusiasts, but all you possibly know is that it means an engine has more “power” to it than normal, but what exactly is going on underneath that bonnet?
Engine power is proportional to the amount of air and fuel that can enter the cylinders, all things being equal, larger engines flow more air and as such will produce more power. If we want our small engine to perform like a big engine, or simply make our bigger engine produce more power, our ultimate objective is to draw more air into the cylinders. By installing a turbocharger, the power and performance of the engine will be dramatically increased.
So how does a turbocharger get more air into the engine? Let us first look at the schematic below:
How a turbo forces more air into the engine
- Compressor Inlet
The air filter (not shown) through which ambient air passes before entering the compressor.
- Compressor Discharge
The air is then compressed which raises the air’s density (mass/unit volume).
- Charge air cooler (CAC)
Many turbocharged engines have a charge air cooler (aka intercooler) that cools the compressed air to further increase its density and to increase resistance to detonation.
- Intake Valve
After passing through the intake manifold, the air enters the engine’s cylinders, which contain a fixed volume. Since the air is at elevated density, each cylinder can draw in an increased mass flow rate of air. A higher air mass flow rate allows a higher fuel flow rate (with a similar air/fuel ratio). Combusting more fuel results in more power being produced for a given size or displacement.
- Exhaust Valve
After the fuel is burned in the cylinder it is exhausted during the cylinder’s exhaust stroke into the exhaust manifold.
- Turbine Inlet
The high-temperature gas then continues on to the turbine (6). The turbine creates backpressure on the engine which means engine exhaust pressure is higher than atmospheric pressure.
- Turbine Discharge
A pressure and temperature drop occurs (expansion) across the turbine (7), which harnesses the exhaust gas’s energy to provide the power necessary to drive the compressor.
But be warned not all hybrids are perfect in every area, there is usually a trade-off for all this performance gain in the way of turbo lag (excluding the latest ball bearing & Variable Nozzle Diesel turbos).
It is very difficult to get improved performance/response all through the rev range with a standard journal-bearing turbo and still get big output at the higher end of the rev range, that isn’t to say it can’t be done, it can with careful design, but on the whole, there has to be a compromise.
We will always give you honest advice, not sell you up and then have you disappointed or upset. If you’re a person who likes to shop around and you find wildly differing prices, be warned, whilst there are occasionally bargains around when buying turbochargers, with Hybrids you do pay for what you get. Find out exactly what you are being offered for your money.