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Blow-by Gas

Discussion in 'Technical' started by bhai, Feb 22, 2012.

  1. bhai

    bhai Esperto

    Messages:
    1,183
    Ahmednagar
    Grande Punto 1.3 90 HP
    Hi

    Blow by is created at the time of power stroke. At the time of power stroke, piston is pushed to downwords.

    Because of wear of piston rings & block, exhaust gases are leaked in crankcase ,when piston is pushed to downwords.These escaped exhaust gas through the block wall creates negetive pressure in crankcase so we face power loss.

    Blow by can cause power loss. See the video

    http://www.youtube.com/watch?v=PvDvcl29ZqMCheck wheather your MJD has blow-by.

    Last edited by a moderator: Feb 23, 2012
  2. Italia-Linea

    Italia-Linea Staff Member Janitor

    Messages:
    2,123
    Pune
    Bhai- there is a mechanism to counter this in every modern engine. Its called as Positive Crankcase Ventilation. The PCV valve exits these blowback gases back to the intake manifold.

    So as such there is no power loss in MJD engine. Chill :)
  3. bhai

    bhai Esperto

    Messages:
    1,183
    Ahmednagar
    Grande Punto 1.3 90 HP
    Thanx Amit for reply. I know that PCV valve is fitted in MJD.But how we know that PCV valve is working right ? Is ECU capable to show faulty PCV Valve ?

    As per videos of blow-by gas, if we keep oil cap of engine oil on filler hole without tightening it & keep engine at idle, cap should not bounce.
    But I found that, yellow oil cap of my MJD is bouncing , small particles of oil are bouncing in the hole from which we put engine oil.

    As the cap is bouncing & small amount of oil is bouncing then I doubt that PCV valve of my car is doing malfunction. I am getting power loss also


    I compared this issue with my DDiS. oil filler hole of my DDiS is complete dry. But oil filler hole of my MJD is messy with oil. Small amount of oil is bouncing through the filler hole of engine oil. That's why I am asking. So I doubt that some amount of blow by is present.

    In addition to that there is oil leak from engine oil sump.

    As I told above blow-by gas creates pressure in crankcase. Because of this abnormal pressure oil may leak through oil sump.

    P.S. Please take a note of that ,hardware of both engines is same. That's why I am comparing this issue with DDiS engine.
    Last edited: Feb 22, 2012
  4. gurjinder

    gurjinder Staff Member Janitor

    Messages:
    3,989
    Punjab
    Bhai ,

    Check the following :

    1. What is the compression in all four cylinders.
    2. What are the present bore to piston clearances.
    3. What is the ring end gap of all the rings in the 4 pistons.
    4. Measure the amount of oil you assume to be losing.
    5. What is the exact amount of power loss being experienced by you.
    6. Is there any glazing of the cylinders
    7. Is the factory crosshatch of the cylinders still present?
    8.
    9.
    10.
    ..
    ..


    Just kidding mate.:D

    Enjoy your Punto. Don't bother about such small things.

    Cheers.
    1 person likes this.
  5. vIjAy_kHaSa

    vIjAy_kHaSa Esperto

    Messages:
    1,352
    Panchkula
    gurjinder don't give new ideas to bhai, he would open separate threads for all the points you have mentioned in checklist thinking his car suffers from all disorders mentioned
    Why don't we make a separate Sub-Forum for Bhai threads.

    Bhai post a video of oil and oil cap bouncing.
    How many kms does your car have on ODO, Combustion gases can also escape if run in is not completed fully. Diesel engines can take 20k and longer depending on your driving style to break in completely
    1 person likes this.
  6. bhai

    bhai Esperto

    Messages:
    1,183
    Ahmednagar
    Grande Punto 1.3 90 HP
    Video of Suspected Blow-by-gas


    is video of my Punto 90 HP. Clocked 8600 KM.

    Facing power loss & 100 % absense of low end torque.Between idling to 1500 RPM there is super & super turbo lag.

    See the video. When I remove oil cap noise of escaped gases comes.& if I replace the oil cap without tightening it ,cap is bouncing .

    So definately blow by is there.I have discussed this matter with TATA ASS.
    WM has described this issue in his local concept " Back-Compression"

    Visiting ASS in next week. Let's see what happens
    Last edited by a moderator: Feb 25, 2012
  7. gurjinder

    gurjinder Staff Member Janitor

    Messages:
    3,989
    Punjab
    The video proves nothing Bhai sahab.

    The cap bouncing around is perfectly normal, in my book. I would be worried if the cap is blown off from there. Also, there is no question of a power loss till 1500rpm. It is just normal turbo lag.

    I hope your experiements with the 90hp Multijet would cease now.:rolleyes:

    Peace!
  8. sungoa2010

    sungoa2010

    Messages:
    2,878
    Goa
    I think ignorance is the best friend:confused unless problem come and knock the door continuously.
  9. Italia-Linea

    Italia-Linea Staff Member Janitor

    Messages:
    2,123
    Pune
    this is very very normal on a diesel engine. the cap mostly jumps due to vibrating engine. secondly have u seen a tata indica with problematic back pressure? the oil is thrown totally everywhere.

    I would seriously suggest you to totally stop suspecting that anything is actually wrong with your car. Drive it, enjoy it, forget it. There is no need of being tensed over these machines. We have lot better things to be tensed of.
  10. vIjAy_kHaSa

    vIjAy_kHaSa Esperto

    Messages:
    1,352
    Panchkula
    The cap is not original Fiat cap or may be Fiat have changed the cap design now.
    Noise of gases escaping is normal for a short duration (2-3 sec) after removing cap remember the system is pressurized and oil is hot which causes oil vapor to stay inside the system.
    8600km is too less for run in to be completed fully, wait at-least till 15k service to have the run in complete fully and If you babysit (rpm>2500) your engine then wait at-least till 30k kms.

    From the video it can not be concluded that there is Blow By to me it seems more like cap is dancing due to vibration from engine. :D
    I would post a video of my 12 year 800 to show you what Blow By actually is, oil everywhere inside the bay if you remove oil cap.
    Last edited: Feb 25, 2012

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