APY and BAM Cylinder Head Cracks - A Valve too Far?

Discussion in '1.8 & 1.8T' started by Dave, Jan 20, 2018.

  1. Dave

    Dave *Very Smart* Pedantic Old Fart Paid Member

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    Location:
    Sligo, Eire
    Some of you may know that Lainey's Mk4 AUQ destroyed its cylinder head due to an oil flow problems.
    Since then I have got hold of 3 more heads:

    #1 - AUQ which was warped beyond use.

    #2 - APY with cracks between the exhaust valves and also spark plug threads. It also has corroded water passages probably due to non-use of antifreeze, or distilled water!?
    The exhaust valve seats were actually oval and took a lot of grinding in.
    In desperation to get the car car back on the road, I used this head even though I was worried about the corrosion. The lands between water ways and combustion chamber were almost none existent.
    The car walked its NCT in December. Of note, the HC levels were half what they had been on the previous 3 tests. One assumes that the polished ports were helping!?
    Just after xmas what I had expected happened. Water leaked into cylinder 1!

    #3 - BAM with cracks between exhaust valves and also spark plug threads.
    I had already bought this head in early December hoping the APY would last 'till the warmer weather arrived.
    There is no corrosion so obviously the previous owner had used a proper coolant mix.
    The cracks are less severe and the valve seats were not badly distorted and took little grinding with coarse paste.
    I have heated the cracked area and peened the cracks closed, polished the ports and will use the head!

    Neither of the AUQ heads have cracks!

    So.
    Are cracks to be expected in all 1.8T engines tuned beyond 180ps?
    The cracks in themselves aren't too big a worry, but misshaped valve seats, which could become loose are.
    Is this why AUDI reverted to 4 valve heads on the TFSI motors?

    Of Note.
    Alloys used:

    alloy props.png

    From what I can find out, the TFSI uses a lower grade of alloy that the 1.8T. (Confirmation needed)
    TFSI = Al Si 7 Mg
    1.8T = Al Si 10 Mg Cu - This has alloy has hot tear properties.

    Valve Spacing:

    The gaps between valves and plug thread are greater in the TFSI head.

    Comments very welcome.

    Dave.
     
    Last edited: Jan 20, 2018
  2. notenoughtime

    notenoughtime Moderator Moderator

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    Dave, hows things?

    There must be a good reason that they changed from 5 to 4 valves per cylinder and as you say more distance between valves helps prevent this, maybe its a cost thing also?
     
  3. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    EA113 TFSI engines, run cooler as you are injecting fuel directly into the combustion chamber near the compression stroke.
    The third inlet valve on a 5v/cylinder engine helps to encourage swirl motion for fuel air mixing prior to combustion. On a TFSI, the shape of the piston enhances tumble motion and are designed to guide the fuel injected from side mounted valves into that tumble blurb. So a 3rd intake valve is not required. There would not be any space for it anyway.
     
    Dave and jamesa like this.

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