Engine braking

Discussion in 'Motorized Vehicles' started by fred2028, Aug 30, 2009.

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  1. epbrown

    epbrown Notebook Consultant

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    There's no sane reason to "save" the brake pads on passenger car - they're cheap as dirt and easy to replace.
     
  2. stewie

    stewie What the deuce?

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    Engine braking is not about gasoline vs. diesel, it's more about the stroke.

    Older 2-stroke engines will give you almost no engine braking without some sort of compression release. Although some newer 2-stroke engines with bigger ports may give you more engine braking feel, but it's still not like a 4-stroke.
     
  3. K-TRON

    K-TRON Hi, I'm Jimmy Diesel ^_^

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    This is not true at all on the diesel side. (I am unaware of any large two stroke petrol engine)
    On a detroit diesel 2 stroke. They have high compression, and a long stroke. The engine brake is nominally twice as effective on these kind of engines.
    For 53 Series
    On a standard engine, the compression ratio is 17:1
    On a Industrial Naturally Aspirated Engine it is 21:1
    On an industrial Turbo charged Engine it is 18.7:1
    The 53 series has a 3.875" bore and a 4.5" stroke.
    That is the smallest type of two stroke, the 71, 92 and 149 series have much longer strokes, and even higher compression.

    I am only aware of one other kind of 2-stroke diesel, and those are the old Cerlist's. Jacobs did not manufacturer an engine brake for them


    I forgot to mention that on a Jacobs breaking system, you need at least one master brake per rank of cylinders
    So on an inline, you need at least one master
    On a Vee type, you need one master brake on each half of the Vee

    K-TRON
     
  4. stewie

    stewie What the deuce?

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    Higher compression doesn't necessarily mean more engine braking, 2-stroke engines usually require a "compression release" device to create engine braking.

    Large 2-stroke petrol engine? hmm true, pretty rare, but 2-stroke petrol engines are very popular in snowmobile, motorbike, etc., and they're well known for not having engine braking unless using a certain special device.
     
  5. K-TRON

    K-TRON Hi, I'm Jimmy Diesel ^_^

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    There is no compression release for a DD 2-stroke
    They are a completely different animal to what a normal vehicular engine

    There are only exhaust valves. The intake is through ports in the side of the cylinder liner (There is an air box on one side of the engine, and a roots type blower on the other)
    [​IMG]

    When the brake is activated, the fuel rack is mechanically pulled back to the idle position.

    You can hear my friend Grigg Jake his Brazilian 4-53T in this video
    The jake is activated around 12 seconds in
    http://www.youtube.com/watch?v=tGzUb2Rpges

    K-TRON
     
  6. allfiredup

    allfiredup Notebook Virtuoso

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    I agree- brakes are much cheaper to replace than a modern 5-speed automatic transmission! Although a lot of cars have a "manu-matic" function that allows the driver to choose when to upshift and downshift (usually by sliding the shifter over to a different gate from the regular 'D' position. But on models with smaller engines, the automatic is already downshifting more often than one paired with a larger, more powerful engine....

    Manual transmissions are a toss-up, especially on some newer models- all of my Honda Civics and Accords (all were 5-speed manual) could eaisly handle engine braking if you wanted to downshift. Even at 150k+ the transmissions showed no signs of wear or problems!

    But my '06 Mazda3 is a different story- at 70k miles, the transmission has some issues (and I don't use it for engine braking) but it's not unheard of for them to fail with under 100k on them...I'm not happy about that either! :mad:
     
  7. Syndrome

    Syndrome Torque Matters

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    Its a ford, can't expect to much out of it. ;)
     
  8. allfiredup

    allfiredup Notebook Virtuoso

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    It's funny that you mention the relationship between Ford and Mazda (Ford owned controlling interest in Mazda until 11/18/08 when they had to sell off most of their stock to raise some cash!

    And don't get me started on the problems I've had with the Mazda! The engine was replaced at 49,200 miles (800 miles before the warranty expired) because fo a bad connecting rod! And just last week, at 72k miles and not even four years old yet- the A/C compressor locked up!!! And they have the balls to charge $750+ for a new one!

    Of course, I'm not dumb enough to pay that....eBay and auto salvage are a marriage made in heaven! I've got a used compressor from an '06 with 16k miles on the way- I paid $180 for it! :D But the original one should have lasted longer than it did...

    It seized up on Thursday evening and then the flooding started here in North Georgia on Saturday....I was SO tempted to let it go for a swim with the fishes...and should have!
     
  9. Syndrome

    Syndrome Torque Matters

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    Yeah, I think they're down to like 13% or something now?
     
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