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Exhaust leak cause low mileage???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 89GMCSuburban, Mar 27, 2003.

  1. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    I have an exhaust leak at the head on the driver's side manifold, my O2 sensor is on that side and the leak is before it...can this be causing my 9 MPG?
     
  2. BowtieBlazer

    BowtieBlazer 1/2 ton status

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    I run a carburated motor but still my exhaust leaks seem to make the motor run a little worst at lower RPMs, I think its feasable.... /forums/images/graemlins/crazy.gif
     
  3. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    I have an exhaust leak at the head on the driver's side manifold, my O2 sensor is on that side and the leak is before it...can this be causing my 9 MPG?

    [/ QUOTE ]

    Yes.
    Exhaust leaks are the worst for mileage.
    Fix it and you could get into 11-13mpg
     
  4. OrangeCrushK10

    OrangeCrushK10 1/2 ton status

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    okay, I can understand why an EFI system would get worse milage. But shouldn't a carbureted engine do better? The exhaust just restricts flow which causes loss of HP to the wheels.

    So wouldn't an exhaust that has a leak flow a bit easier since it can bypass the muffler and get a bit more HP freed up?
     
  5. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    okay, I can understand why an EFI system would get worse milage. But shouldn't a carbureted engine do better? The exhaust just restricts flow which causes loss of HP to the wheels.

    So wouldn't an exhaust that has a leak flow a bit easier since it can bypass the muffler and get a bit more HP freed up?

    [/ QUOTE ]

    No
    You need some back pressure to build torque, and torque is what gets you the mileage.
    You could rev it easier but torque is what gets you off the line, and HP is torque times RPM so lower HP.
    The only place where you get more power is if you have great flow on the intake which is never the case on stock engines.
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    You need some back pressure to build torque

    [/ QUOTE ]

    That is the biggest myth. That's total BS. Backpressure is BAD, period. Backpressure is what makes restriction in the exhaust system.

    Yes, you do need pipe of the correct size to flow correctly, but that's not called backpressure, that's called cylinder scavenging.

    BACKPRESSURE IS ALWAYS BAD.
     
  7. monte0172

    monte0172 1/2 ton status

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    I have a 79 full time with a 400 and i dont care if it has an exhaust leak or not (which it did at one point) I can pull anything or nothing at all and it gets 9MPG no matter what!!
     

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