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by James Stanford

Toyota HiLux

Turbocharging is more popular than ever as car makers look for ways to produce power more, more efficiently.

Turbos have been around since before the First World War and have traditionally been used as a way of generating more power without increasing the displacement of an engine. The increase in popularity of the diesel passenger car in the last 15 years is primarily due to turbocharging, and turbos are now finding their way onto downsized petrol engines to improve fuel economy.

BMW Turbocharger - 2

Turbochargers were first used on some aero engines in WW1, soon finding their way onto large diesel engines used for trucks, trains and ships in the 1920s. Turbocharged petrol cars appeared in the 1970s. Technological improvements have widened the appeal of turbocharged cars by reducing the time it takes for the turbo’s added grunt to kick in – referred to as turbo-lag.

BMW Turbocharger - 1

To put it simply, turbochargers help engines breath better and perform better. They do this by using the engine’s exhaust gas to spin a turbine wheel that connects to a compressor wheel via a shaft, that then compresses intake air and forces it into the cylinder. This compressed forced air allows more fuel to be burnt and more power to be produced at the same engine speed.

Subaru WRX STi

The turbine and compressor are sophisticated fans that sit at either end of a single short shaft. The exhaust gas spins the turbine, rotating the shaft and the compressor, pushing more air into the engine. Many turbochargers control the maximum intake pressure or boost with a wastegate valve that allows some exhaust to bypass the turbine. This system improves low-speed performance without risking dangerous overboosting at high speed. The high-pitched ‘pssht’ sound you sometimes hear on powerful turbocharged cars, especially when modified, is the blow–off valve operating, releasing an oversupply of air from the intake system after the driver has suddenly shut the throttle.


Most turbo engines also run an intercooler. Like a radiator, it cools the intake air after it has been compressed, increasing its density and engine power potential while guarding against knocking (detonation) in petrol engines. Intercoolers are often found at the front of the engine, such as on the Ford Falcon XR6 Turbo and Mitsubishi Lancer Evo, or on top of the engine, as on the Subaru WRX and Toyota Hilux, usually resulting in the use of a bonnet scoop. Some cars even employ an intercooler water sprayer to better assist with chilling the passing air.

How It Works is part of a technology focus series that features first in the CarAdvice iPad magazine app that can be downloaded free every month.

  • AndyGF

    Nice article CA, you could have added a little more about variable vanes turbos and maybe even twin scroll turbos (both increasingly becoming more popular on production cars).

    All petrol turbo cars make the ‘pssht’ noise, just most production cars don’t vent to atmosphere which makes the sound audible, they vent into the decompressed side of the intake system to reduce air-filter maintenance.

    Keep on with the tech-articles…

    • Zaccy16

      even in my polo i get that fantastic little wastegate noise, makes you want to lift of the throttle! 

      • Robin_Graves

        Thats not the wastegate Spaccy, its the blow off valve (BOV) or compressor surge.

        • Zaccy16

          No it is the waste gate, read the article and watch top gear

          • Robin_Graves

            Spaccy I dont need to read the article or watch top gear (lol) to know that the ‘fantastic little noise when you lift off the throttle’ is not the wastegate.  The wastegate lets excess exhaust gas bypass the turbine to control boost and it makes a ‘braaaat’ noise on engines with external wastegates or ‘screamer pipes’ Its just exhaust noise.  The fluttering noise on lift off is either the blow-off valve or compressor surge or both.  If your Polio has VGT then it probably doesnt even have a wastegate.

          • Zaccy16

            It is the wastegate

          • Robin_Graves

            Sorry to burst your bubble zaccy but you are 100% wrong.

          • Zaccy16

            Do a bit of research robin and you will discover that the tsi engine has a electric wastegate

          • Robin_Graves

            ‘Electric’ or electronic boost control has been around for decades. Makes no difference how the wastegate is actuated.  When you lift off the throttle there is a decrease in exhaust gas flow meaning the wastegate is not needed. Conversely there is a surge of boost not being consumed by the engine. That’s where the bov comes in, venting off excess boost to stop the turbo compressor hitting a brick wall and slowing down causing lag when you put your foot back down.

          • Zaccy16

            have a look at the video on youtube ‘VW TSI ENGINE ANIMATION’ and you will see that it has a wastegate

          • Hung Low

            Sorry Zaccy, Robin is 100% correct on this one.

          • AndyGF

            Zaccy, Robin is correct, your polo does not have a wastegate, but it does have a dump valve or blow off valve, easy to get confused… no harm done. I know what you meant.

            PS: be grateful your car does not have a wastegate are horrid things, prone to jamming and most modern turbocharged engines do not use them, I say good riddance.
            I would rather have a twin supercharged, quad turbo chargered engine with no wastegate, than one single turbo with a wastegate.

          • http://www.facebook.com/kiran.sb.3 Kiran SB

            yes the polo has a wastegate valve 77tsi

          • Zaccy16

            exactly, robin is a bit delusional i think

          • Hung Low

            Yes it does like most production cars, what happens when the waste gate opens is that the exhaust gas that is used to spin the turbine to a desired speed/boost level is bypassed down the exhaust with the rest of the exhaust gases. Being an internal waste gate design (part of the housing) it is plumbed into the exhaust so you do not hear it. I’d say its compressor surge you hear cause the dud quality blow off valve has crapped itself.

          • Sumpguard

            I’m feeling your pain Robin.

      • Enthusiast

        You drive a polo… Hahahahahahahahahahahahahahahahahahahahahahahahahahahahhahahahahahahgahahahahahhaha

    • Dave W

      If the air passes through the intercooler anyway, then why do people say Golf has to be detuned here because of our hot weather?

      • Robin_Graves

        The intercooler works much better when its cold outside.  Detonation is much more likely when intake temps rise – especially in the case of VeeDuds when the whole engine ends up detonating.

  • Golfmother

    So addictive , once you have it you cannot go back , performance with economy .

    • F1orce

      Yeah but you need to spray more fuel to take advantage of more air..

      • Golfmother

        Economy is better in normal driving ,more use of higher gears , sure it sucks plenty when pressing on .

    • Zaccy16

      i agree, the torque in any gear is fantastic!

      • Zaccy15

        I agree!!!

        • Robin_Graves


          • Karl Sass


          • Zaccy

            go zaccy woo!

  • Frostie

    Great work introducing this new segment. I’d like to see more of it.

  • Trump

    Caradvice has now reached the next level! Love your work CA. Now if you could teach me how to program an apexi….

  • F1orce

    Nissan 370z doesn’t have a turbo.

    But yet it’s a thrill to drive

    • The Real Wile E

      But imagine it with twins  -oh I forgot that’s the GTR

    • Zaccy16

      but engine sounds rough and not sporty

      • Enthusiast

        You drive a polo and criticizing? Hahahahahahahahahahahahahahahahahahahahahhahahahahha

  • Robin_Graves

    Maybe could have mentioned the purpose of the BOV as well, prevent compressor surge and keep turbine speed up during gearshifts or changing throttle position in corners to reduce lag.

  • Hung Low

    As simple as turbochargers seem, they are a complex unit when it comes to matching engines for a desired performance level. Turbine wheel and housing sizes, Compressor wheel and housing sizes, A/R ratio relationships. Compressor flow maps to maximise flow at a desired boost range, electronic controlled waste gates, variable vanes that change the turbine housing AR ratio to reduce lag at low rpm while still providing top end power. As much as people enjoy the surge of torque and power of a turbo engine, sometimes the immediate throttle response and linear power delivery of a sporty n/a engine is hard to beat on a quick blast or on a circuit in my experience.

    • AndyGF

      I can tell you that throttle response is a purists view to performance motoring, get in drive and its predictable, its maximum power delivery is determined by its rpm, so at low rpm its predictably ‘slow’. Same could be said for my grand-father and his 28hp Morris Minor he’d often go on about…

      Turbocharged cars on the other hand are an acquired taste; and like most acquired tastes they tend to be worth it after little getting used to…

      One thing is for sure though; turbocharged cars do make for amazing daily drivers…

      • Hung Low

        I would say the naturally aspirated engine is an acquired taste, especially when one is talking a cammed engine or ported rotary ie small capacity engines. Turbos when matched well make the power and torque more accessible and drivable, it is ultimately easier to live with as a daily driver but on a circuit in high hp applications, throttle control when exiting corners is much harder, hence why drifters love them. I remember having a Cordia Turbo back in the day, huge turbo for a production 1.8 car, it would not even see boost/ positive manifold pressure in 1st gear due to lag from the massive turbine, but in the upper gears with revs on board, the thrust back in the day way amazing from a 4cyl car, it would give the V8 falcadores of that era a bit of a spanking once on the move.

        • AndyGF

          NA engines are an acquired taste? That is pushing the definition of predictability a little don’t you think?

          Irrespective; smaller turbos are less predictable on the track for sure because the throttle response is too violent…
          However larger turbo chargers typically have a much more progressive (intertia) and less violent spool characteristics, making them actually track day friendly, rather than a hindrance.

          I personally find turbocharged cars easier on the track, by keeping the revs lower you can get on the gas earlier after the apex (corner exists) and the progressive nature of a larger turbocharger means its easier to maintain traction. VS very powerful NA cars if you just flex your right toe a little too much mid corner you end up over-steering (and possibly wreaking it).
          Also very peaky NA engines (the ones you think are acquired tastes) are slaves to their gear ratios, if your ratios arent 100% perfect the track you are on you are off your game and there is nothing you can do about it…

          • Hung Low

            Andy, I was referring to an acquired taste in performance street applications. These days, noise, drivability, economy etc of a performace atmo engine is the bane, heck people even whine about the drivability and torque hole in Hondas Vtech. In comparison turbocharged engines are totally docile and give the best of both worlds. Larger turbos like an old Garrett TO4E on a 13b rotary or in race applications like the Group A Sierras were anything but progressive. When getting into boost the torque and power curves can double within 1000rpm giving that true turbo rush. It is no secret the Grp A Sierras were an handful around Bathurst!

  • Guest

    Good as a Turbo is! – There is a dark side to it. Turbo engines generate a lot of heat – Thermal loading from very high EGT (exhaust gas temperatures) on the exhaust turbo side. A Turbo engine need frequent oil & oil filter changes ie. @ 5k km intervals. Recommended oil is the synthetic type. Mineral oils tend to break down into sludge due to high operating temperatures. The radiator & cooling systen needs to be flush & coolant replaced every 10-15k km. Turbo engines need a lot of maintenance to keep the engine & turbo from failure. Even brakes & transmission needs to be regularly checked as turbo engines tend to have high torque output. In short, without proper & costly maintenance, turbo engine will have a very short life.
    Unless you’re willing to pay higher maintenance on a turbo car, it’s not recommended buying one!

    • Golfmother

      Rubbish , just follow , service times , dont track thrash.

      More cars than ever will be turbo in the future .

    • http://www.bryanbyrtrenault.com.au/ Modern Man

      WTF are you on about. I think you might be thinking of OLD SCHOOL high performance turbo engines.
      Modern engines (turbo or not) specify synthetic oils as they are cleaner and last longer and do less damage to alloy engines.
      Frequent oil changes are a thing of your imagination. in oz most companies doing a turbo engine will dictate a 10k or 15k service and coolant is the australian standard of 2-4 years depending on driving and brand. overseas the same engine is anywhere from 20-45k between services depending on manufacturer. the differences are due to our lack of training and knowledge of what to check (i.e. brakes tyres suspension) on our cars rather than our climatic conditions.
      brakes and transmissions checking is completley dependant on your driving and not the engine.
      for instance a 2.0l NA engine is heavier than a 1.4l turbo and during normal day to day running will actually put more wear on the brakes than the turbo due to the weight over the front wheels. if however you have a 2.0l NA and a 2.0l Turbo then this is different as one is clearly used for performance duties and will generally have its brakes etc upgraded anyway.
      what the article was describing is the use of smaller engines with turbocharging to acheive the same/similar power to a larger heavier engine. this is why fuel consumption is dropping in the real world compared to NA engines.
      Your heat issue you describe is another falsity. most engine bays are designed for a larger NA motor and when you downsize the engine you create breathing space and a 1.4 needs smaller radiators but the tend to leave them the same size for cooling efficiency as well as parts commonality.

      Conclusion; higher maintenance is a moot point nowadays unless you are looking for performance not fuel economy. Remember trucks do millions of heavy high temperature kms and they are all turboed.

  • A.Wal

    I have a turbo daily driver, a (Fiat) 90kw/206nm 1.4 petrol. They’re great engines, it come son boost at approx 1500rpm and is pulling at full force by 1750rpm with a flat torque curve pretty until 4500rpm. I find then it tends to fall flat on its face and feel relatively weak at about 5000rpm. So while the low down torque is very handy in the sense frequent gear changes arent required, theyre not fun at high revs.

    I also notice if driven very softly they’re very efficient but if you wring its neck it has no problem drinking 9l/100km.

  • A.Wal

    Possibly a stupid question: Are Cold Air Intakes on turbo cars pretty much pointless? as the turbo will heat up that air anyway? and the intercooler will then cool it down again?

    • Pro346

      Far from it!

    • http://www.bryanbyrtrenault.com.au/ Modern Man

      cold air intakes grab the air from the outside of the car otherwise it would be grabbing the air from with in the engine bay which is hotter and therefore less dense.
      Inlike in real life, the denser it is the beter it is.

    • Karl Sass

      Short answer, no. Long answer is they’re still useful because an intercooler can only reduce intake temps by so much, so if the intake temp is lower to start with, it’ll still be even cooler coming out of the intercooler..

  • Random

    Shhhh … nobody mention a turbo to the 86 … it might burn and crash

  • Fred S

    The video was very informative……… I thought a “turban” was something that would be worn on the head, not used in an engine!

  • Peter

    Does anyone know why a manufacturer chooses turbo over supercharging and vice versa for particular engines?  Jag have turbo petrol 4 cyl, supercharged petrol 6 cyl, turbo diesel 6 cyl, supercharged petrol 8 cyl, I always wonder why one over the other

    • Oosh

      In general turbos are more efficient and have a better top-end but they result in a more complex system overall and even though they have come a long long way lag can still be a factor.
      Superchargers (of the positive displacement variety) are still the way to go for massive globs of instantaneous low-down torque.
      Packaging can also be a factor, depending on the engine and engine bay it’s going in to, the available space may better lend itself to one setup or the other.

      • Peter

        cool, thanks.  I actually didn’t mention – all of those engines go into the one car (the XF), and I forget there is a turbo diesel 4 as well (ignoring the NA 6 and 8).  But I think that Jag might have outsourced the 4 cyl engines, and it isn’t often that you see a 4 cyl supercharged outside of the kompressors

    • Robin_Graves

      Turbo is more efficient as it is driven by waste heat being lost out of the exhaust where as supercharger uses a fraction of the available useable power to drive it.

    • Dave S

      My opinion is that generally smaller engines like to rev more. Turbos (exhaust driven) – more revs = more boost and power.
      Superchargers are better for bigger motors because they are mechanical and use an amount of the engines power to work.Superchargers are more about torque and high rpm power.

  • HAHA!

    Zaccy16 is a Douche!