Turbo, Big Turbo, TwinTurbo, Bi Turbo!!
To understand Turbo‘s you have to know the basics of how an engine works.
Think of an engine like a very large pump it sucks air and fuel into a cylinder, compresses and combusts it pumping out the exhaust gasses. To get more power from an engine, you need to burn more fuel more quickly, getting fuel is usually as simple as turning it up, but unless there’s also more air that extra fuel is useless.
A cylinder is limited in how much air it can breathe by size or displacement. Historically when engine makers wanted more air to mix with their fuel, they needed a bigger cylinder, there was no replacement for displacement. this made engines larger, heavier, in often times made it slower to rev.
Then in 1905 Swiss engineer named Dr. Alfred Büch came up with a replacement for displacement when he use the exhaust gases of an engine to power a compressor that then fed denser air into the combustion chamber, more air meant more fuel can burn and get more boom.
Turbos were quickly adopted by the aeronautical industry, were 20,000 feet up the air is almost half as dense, losings almost as much of half of their power.
Turbos restored air pressure in the engine back to sea level pressure, this is called Turbo normalizing when a turbos used to exceed that pressure that’s called turbo charging!
A
s you engine expels exhaust gases they enter the hot side of the turbo where the gases flow over the turbine spinning it, the exhaust gases then travel down the exhaust and out the back your car.
The turbine is connected to a impeller on the other side of the turbo, it spins too, as it spins it sucks in air from the air filter/Inlet, spins the impeller and sends it into your intake manifold, the air is now more dense, it has more oxygen so it can burn more gas more quickly giving you more power. To keep that charged air from going back into the turbo when you lift off the throttle, a blow off valve releases the pressure letting the air back into the atmosphere that’s why you get that cool turbo sound PPPSSSSHTTTT or BWAAAA-SUTUTUTU.
Turbo charging creates a lot of heat, the turbine side constantly has exhaust gases passing through it making it literally burn red hot, you may notice that the side which is appropriately referred to as the "hot side" of turbo often looks rusty that’s because the extreme heat acts as a catalyst causing the metal to oxidise more quickly.
The "cool side" also generates heat, when you compress air you push the molecules closer together and create friction when they all rub up against each other all these hot energized molecules move around everywhere, they then increase the speed of the air and that makes them lose density.The whole point of forced induction is to get denser air, well if we cool all of this hot turbo charged air off, the molecules will cooler down sit closer together and become even more dense, there are a few ways to do this.
The most popular and simple way is with an intercooler, an intercooler sits between the turbo and the engine, the air passes through channels with cooling fins, the cool air from outside passes over the fins, absorbs the heat and reduces the temperature. if your Subaru has a hole in the bonnet, don’t worry that’s for your intercooler.
Now we know that a turbo charger is an air compressor, so if you want more power why don’t you just get the biggest turbo you can find? Well its not that easy, if a turbo is too big it takes a long time for the exhaust to get it spinning fast enough to compress the air, the time between hitting the gas and feeling the boost is called LAG. They solved this problem by using two smaller turbos to push more air than one large one, we think of twin turbos as their own category but there is actually multiple ways to put two turbo chargers on an engine, parallel turbocharging, sequential turbocharging and to a lesser extent two stage turbocharging. We will go over different options their pros and cons in a future article.
We hope you enjoyed this article and got a better understanding on Turbos and their function.