Why Don't Small Turbo Engines Get Good Gas Mileage? (Real World)
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In attempts to improve fuel economy, many companies are choosing to downsize and turbocharge engines. These small turbo engines tout the power of larger engines, but with much better fuel efficiency. You may notice however, your real world fuel economy may not always match up with the EPA numbers provided on the vehicle's monroney sticker.

Why is this? Well while downsized turbos do have many advantages, such as less moving parts, less weight, better packaging, lower frictional losses, and lower pumping losses, once the vehicles start to get into boost, that efficiency can be significantly lower. This video will discuss fuel enrichment and why it's necessary for high boost engines in order for them to run reliably.

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    • Daniel Madden
      Daniel Madden

      That is a human colon you got your classes mixed up.

      about 15 hours ago
    • Marik Zilberman
      Marik Zilberman

      What about intercoolers that cool the boost air?

      about 1 day ago
    • F!@#Guilt
      F!@#Guilt In reply to Marik Zilberman

      Do any turbos not have an intercooler? I thought it was universal.

      about 14 hours ago
    • mercuriallimit

      can you do one on civic fk? there are versions that are 1.8 and 1.5 with small turbos

      about 1 day ago
    • electrictroy2010

      I drioe Ford’s turbo-3 cylinder and got 70 mpg on the highway, so yes it can be highly efficient if you stay out of the turbo


      about 2 days ago
    • Fournier Don
      Fournier Don

      Thanks for explaining what I have noticed with cars I have owned/own. My current vehicle (small turbo) gets poorer mileage than my previous model of the same car (larger non-turbo).

      about 2 days ago
    • Eduardo Sánchez
      Eduardo Sánchez

      I just rented a VW Polo in France for over 1 month and it gave between 45 to 50 mpg depending on how fast I drove it. Btw, in France people go fast, highway speeds are usually 85 mph and in the city you always have lots of stop and go driving

      about 2 days ago
    • Indrid Cold
      Indrid Cold

      A small engine with a turbo is nothing but a ticking time bomb. They are formulas for disasters. Traditionally, four cylinder engines with a turbo are junk. That tradition is still not broken. Modern four cylinder turbo engines are the mechanic's bread and butter.

      about 3 days ago
    • Alexandar Hull-Richter
      Alexandar Hull-Richter

      Doesn't having a richer fuel mix create excessive hydro-carbon emissions, and make it harder to pass smog?

      Also, wouldn't the richer mixture create extra blow-by and dilute the oil?

      about 4 days ago
    • electrictroy2010
      electrictroy2010 In reply to Alexandar Hull-Richter

      Richer fuel mix makes less NOx (which CARB and the EPA hates)


      about 3 days ago
    • Chris Grasser
      Chris Grasser

      "Why doesn't my car get the sticker fuel economy?" Because you're not strapped down to an emission dyno doing a fuel economy trace. The EPA estimated fuel economy numbers are to compare one car to another not tell you what YOU will get for gas millage.

      about 5 days ago
    • Marko Josic
      Marko Josic

      1) with an good intercooler you increase your effficency

      about 6 days ago
    • Simon Long
      Simon Long

      Rich mix is cooler as you're burning more hydrogen to carbon

      about 6 days ago
    • Mike Girard
      Mike Girard

      My Honda Civic 1.5t is insanely efficient. Runs lean with no boost and gets 50mpg with a light foot. But yes, if you use all 170HP, you get that relative economy. Honda figured it out. I suspect the turbo location (integrated with the exhaust header) and some enhancements in head and piston shape make it work.

      about 9 days ago
    • MyTech

      The WW2 fighter planes that ran 70inchesHg (~2.3bar absolute) during full power often used water or water/methanol injection to stop knock rather than increasing the richness. (methanol prevents freezing and may assist with vaporization and stable combustion, up to 50% was used, though straight water has a higher heat capacity)
      Increased richness was preferred for takeoff and landing as those are more critical phases of flight and so avoiding extra mechanisms is desirable. Just don't use water high in minerals or you will coke up the exhaust valves and turbo.
      Turbojets into the 1970s often had water injection for takeoff and initial climb so they could increase thrust without melting the hot section; when old films of jets show sooty black exhaust on takeoff this is from water injection cooling combustion. (the water also adds a few percent to the accelerated mass, which is the essence of thrust)
      The Atkinson cycle can work well for a small supercharged engine designed for efficiency, avoids the issues with low compression.

      about 10 days ago
    • Fred Bach
      Fred Bach

      You keep talking fast and saying some things over and over again. Ok I'll let that go. However I was somewhat disappointed that you didn't discuss water injection to cool the hot compressed gasses and slow down the flame front(s). Also what about just using a higher octane fuel?

      about 11 days ago
    • Tony p.
      Tony p.

      The MK7 VW golf 2.0 and 1.8 reach the goal of V6 power with 4 cylinder efficiency. Hyper control over many parameters, good head design and some other stuff I'm not aware of. But what is do know is AFR. These engines stay stoichiometric at insane loads and boost levels and hold together like an old train.

      about 11 days ago
    • ChawenHalo 008
      ChawenHalo 008

      Thanks for that. I could never figure out why most 4 pot turbo bangers with around 250-300 bhp used more fuel than my S54 inline 6 with 350 bhp.

      about 13 days ago
    • Brothers Minchevs
      Brothers Minchevs

      Diesel engines don't have this mentioned problems. Pure benefit from downsizing

      about 14 days ago
    • TJ Ward
      TJ Ward

      Forget fuel economy. I just want to turbo my dual sport. Needs a little extra power to get up those hills.

      about 14 days ago
    • sights2397

      It would have been interesting to say what are you considering to be a small turbo engine, by US or/and European standards. Anyhow, thanks for great infos, as usual.

      about 15 days ago
    • Mehdi S
      Mehdi S

      More interesting is what is the longevity of these bicycle engines... I have my doubts about them reaching even 200.000km, like a decent Japanese normally aspired 1.2 - 1.6 can easily do...

      about 16 days ago
    • deniz vapur
      deniz vapur

      Legal speed limit is significant parameter.

      about 18 days ago
    • Albert Ochoa
      Albert Ochoa

      Mate, my TSI 2.0 is making 8 l /100

      about 18 days ago
    • ThirdLife86
      ThirdLife86 In reply to Albert Ochoa

      Mate, i can do that with my 5.0 SC AWD Car with ZF 8HP as well. Difference is: mine actually pulls when i want it.

      about 15 days ago
    • J L
      J L

      What about small turbo diesels?

      about 19 days ago
    • Monsterfrog
      Monsterfrog In reply to J L

      As long as you don't romp on it constantly, even a 3.9L 4bt cummins can get 25-30 mpg. Smaller 4bt diesels can easily get 40 mpg even when driven hard. My 1.9L jetta tdi gets 45 avg mpg and I drive it ~100 miles per day, half city, half highway. Only put my foot to the floor a few times a day when I really need to.

      about 19 days ago
    • Mr. Sir
      Mr. Sir

      I have a 2 litre N20 engine, and around the city I average about 16 mpg even if I have a grandpa foot... kinda pisses me off sometimes. Car feels great under boost though

      about 22 days ago
    • Mr. Sir
      Mr. Sir In reply to Mr. Sir

      Ray Ant That's pretty interesting to know. I was also kinda curious if upgrading the intercooler would help prevent knock prevention from happening as soon... But anyway I'll definitely have check out some tunes!

      about 18 days ago
    • Ray Ant
      Ray Ant In reply to Mr. Sir

      And even better with a tune, and it seems I'm getting better gas milage with the tune as well

      about 19 days ago
    • why care
      why care

      2017 Cruze 1.4 gas turbo...40 mpg hwy, I average 42 between city and expressway

      about 22 days ago
    • Dr H
      Dr H In reply to why care

      I’ve got a 2013 Cruz with the same 1.4 ecotec turbo and I love it. It’s got great power and is perfect for my needs. As long as you’re not carrying a bunch of heavy passengers it’s actually pretty quick.

      about 20 days ago
    • RAYDOGLOC Coolest shots
      RAYDOGLOC Coolest shots

      You look like my cat vanilla she’s white!

      about 22 days ago
    • Richard Stoud
      Richard Stoud

      my 2015 volvo S60 T5 (240hp and 260 lbft of torque from 1500 rpm) has 2 driving mode. In regular, you can drive it like its a diesel. The reves rarely go above 3000 rpm. I get 30 around town and 38 on the high way.

      about 23 days ago
    • Notmi Relnam
      Notmi Relnam

      You mean to say that when my engine is making more power, it's also using more fuel? Say it ain't so!

      about 23 days ago
    • Pierre Kuchmann
      Pierre Kuchmann

      Well how much air an engine uses seems irrelevant to me only the fuel matters i assume how it works means more air also neccesitates more fuel

      about 23 days ago
    • Gtaoutsider

      This is wrong I have MK7 gti o get good mpg if I drive it normal my wife Jetta with the 1.4t that cars get 31 mpg city driving

      about 23 days ago