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Why is breaking the timing belt so bad on a TT?

Discussion in 'TT/TT-S/TT-RS Forum' started by SilverTT1, Dec 12, 2008.

  1. SilverTT1
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    SilverTT1 New Member

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    Ack... just got news from the repair shop that my timing belt broke. I'm waiting to hear the full extent of the damage. I was going about 45 mph when it went. Can someone explain to me why with the TT's interference engine that breaking the timing belt does so much damage? Why are the valves inset so that they can get damaged when the cam shaft stops?
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  2. auroan
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    auroan Active Member

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    It's all about efficiency and power.... I'm sure someone with more time will be able to explain a bit more.
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  3. alijames
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    alijames Active Member

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    It's certainly all about efficiency and power.

    The piston has to compress the air/fuel mixture to the smallest possible volume to develop power, and the valves have to open as wide as possible to get air in and exhaust out as quickly and efficiently as possible.

    Unfortunately, as we expect good power AND economy, the valves, when open, have to occupy the same space as the piston does at another point in the cycle. Thus, if the timing belt goes, valves WILL meet pistons.

    You could always buy an old low compression engined car, or find one that uses a chain instead of a belt...

    IIRC, chains are starting to become popular again.

    Cheers,
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  4. Macduff
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    Macduff Member

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    I don't understand why car makers went to belts in the first place. A very unreliable solution to a problem that didn't seem to exist.

    If I was cynical I'd say it was to give dealers work that they might have lost as cars became more reliable.

    However, as alijames said, chains are coming back. All the VAG diesels except the 1.9 and 2.0 use chains (the V10 has gear driven cams which is even better but expensive to produce). I think most of the bigger petrol lumps have chain drive. Not sure about the smaller petrol units though.
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