1. Introducing the smashing new Team FIAT T-Shirt !! To order yours click here : Team FIAT T-Shirt

The Layman's Perspective :So, what exactly is turbo "boost" ?

Discussion in 'Technical' started by gurjinder, Mar 15, 2014.

  1. gurjinder

    gurjinder Staff Member Janitor

    Messages:
    3,989
    Punjab
    Very often, we come across the term "turbo boost". And it being used in such sentences as :

    1. Hey, let's crank up the "boost" and make more power!
    2. I'm running more boost in my engine than person X.
    3. Let's put in a bigger turbo and run even more boost.

    And so on. Let's also put in a customary Vin Diesel pic when it comes to anything related with turbos and boosting cars.
    exactly.jpg

    On a somewhat more serious note, let's try to have a completely layman's look at what exactly lies behind the term "turbo boost".

    In it's most rudimentary form, consider a turbo as a fan having blades on 2 sides of a common shaft. The exhaust exits from the engine are connected straight to the exhaust side of the turbo. The "blades" on the exhaust side are driven by the exhaust gases exiting the engine's exhaust ports which spin the shaft. This spinning of the shaft in turn spins the intake side which takes in air from the air filter and sends it into the air intake manifold at a greater volume and pressure than it would naturally.

    So, what is the so called "boost" pressure? "Boost", like oil pressure, is nothing but the restriction faced by the air while moving from the turbo to the intake. Higher the restriction, higher the boost pressure, harder the turbo has to work to move a given volume of air. Imagine blowing a flute with your mouth. You can blow more air through a 1inch diameter flute at a lower pressure than through a 10mm flute which will require higher pressure to flow the same amount of air in the same time.

    So, a higher boost pressure does not always mean a positive co-relation with power output. Why, you ask? Any machine is designed to operate in a range where it is in it's peak efficiency. For e.g. a truck engine might be designed to operate continuously at rpm's below 2500 and a F1 engine may be designed to stay continuously in the 18000-20,000rpm range. Similarly, there is a efficiency range of the turbo as well. You can only spin a turbo so much. Try to spin it too much and working against too much restriction and it will be working beyond it's range and doing nothing but sending lesser volume of air at a higher temperature. You might see higher pressure readings but witness a power drop as well. Decreased reliability in the long run is another negative consequence.

    So, while talking of "boost pressures", the key point to be kept in mind is not some number which has a magical co-relation with power output. A more holistic approach is needed. For e.g. you can make X amount of power at 15 psi and you can make X+Y amount of power at 15psi as well. The Y amount of power gets added when we make the intake plumbing (including the cylinder head) that much more efficient (less restrictive,better flowing) and tune accordingly.

    The above is just a layman's view from a person who is not even a mechanical engineer. So feel free to discuss and debate. :)

    Cheers.
    20 people like this.
  2. Ravi

    Ravi Staff Member Janitor

    Messages:
    6,001
    Bangalore
    Grande Punto 1.3
    Your layman explanation on boost clarifies a lot, than having too technical jargons.
  3. Himanshukumar

    Himanshukumar Amatore

    Messages:
    157
    BANGALORE
    Bengaluru
    Grande Punto 1.3
    Gurjinder..... :up

    Nice explanation for a layman...... But i still find more technical..... It would be good to have small simple pictorial presentation with this..... B'coz Novice like me to automobile still find bit difficult to understand.
  4. livelyyoungman

    livelyyoungman Regolare

    Messages:
    428
    Chennai
    Chennai
    Linea 1.3
    Gur(u)ji ... Its awesome explanation.
  5. Chaos

    Chaos Regolare

    "Pictorial presentation"

    I respect Jason for his work on youtube.

    Gurjinder has nailed it for the layman terms!

    This video basically explains the working of a turbocharger (they all use bost :p) for some who want a pictorial explanation.


    I strongly suggest anyone with the hunger for learning the technical know-how to Subscribe Jason's channel! And watch some of his videos for a better understanding of their cars.
    He makes it all so simple :p
    6 people like this.
  6. Ganges

    Ganges Esperto

    Messages:
    3,125
    Driver Seat _/
    :
    Grande Punto 1.3
    i believe this is what we feel when the clutch is pressed fully and throttle position at maximum and after release of the clutch a sudden turbo boost we feel.
    Please correct me if i'm wrong.Anything related to clutch ?
  7. sine04

    sine04 Regolare

    Messages:
    275
    Mysore/Bangalore, Karnataka.
    Mysore/Bangalore, Karnataka.
    Fiat Enthusiast
    What's the relation between EGR valve and turbocharger? Is the exhaust gas routed through EGR to the turbo? If not, why would a car having a clogged EGR face lack of boost?
  8. gurjinder

    gurjinder Staff Member Janitor

    Messages:
    3,989
    Punjab
    No, not really. That's called dumping the clutch. You can do it on any car - turbo or NA and get a good launch from a standing start.

    No, the exhaust is not routed via the EGR to the turbo. A clogged EGR and a clogged intake manifold will not be classified as lack of boost but as lack of power because the engine is unable to breathe well. Lack of boost will be when the turbo-to-intercooler-to-intake manifold piping gets a leak due to getting ruptured etc.

    Cheers.
    4 people like this.
  9. sine04

    sine04 Regolare

    Messages:
    275
    Mysore/Bangalore, Karnataka.
    Mysore/Bangalore, Karnataka.
    Fiat Enthusiast
    Turbo boost, in 'feel' terms, is the surge you feel at around 2200 rpm.

    Sent from my Nexus 5 using Tapatalk
    2 people like this.
  10. asimpleson

    asimpleson Esperto

    Messages:
    3,000
    Heptanesia
    Linea 1.3
    Wastegate Valve..

    Appreciate the information Gurjinder, good write-up indeed. In the interest of further quest for information of TFIans, the following video well explains about 'wastegate', a component that is often less known about or talked about when referred to turbos.

    Last edited: Mar 17, 2014
    2 people like this.

Share This Page