Compression 2E vs ADY vs AGG

Discussion in 'Engines' started by sdj_mk3, Apr 26, 2007.

  1. sdj_mk3 Forum Member

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    2.0L 8v mk3 Golf Gti engines is the order of the day.

    In Haynes it says that all have exactly the same bore and stroke (82.5 and 92.8mm respectively)

    But the 2E and ADY have a compression ratio of 10:1 and the AGG has a compression ratio of 9.6:1

    Why? Is this due to different thickness head gaskets, different pistons or a different shaped combustion chamber in the head?

    I had an AGG with a skimed head running at 10.8:1 which I want to swap to and ADY depending on what the increase in compression is down to I could end up with either 10.8:1 as before or 11.2:1 which is too high really for what I want.
     
  2. sdj_mk3 Forum Member

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    Anyone???

    I'm thinking most likely is pistons. I took the plugs out of the ADY and looked down the bores and they're still dished pistons as in the AGG but I recon the dish only has to vary by about 1mm to give this change in compression which you can't tell with a torch down through plug hole!!! Anyone one know if the piston part numbers are different between the 2E/ADY and the AGG?
     
  3. Phil. Forum Junkie

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    I was going to say the dish in the pistons but are they all not the same non-interference type. I'll check on ETKA later
     
  4. rubjonny

    rubjonny Administrator Staff Member Admin

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    I think its more likely to be the gasket, early 2.0 8v engines had a fibre/card gasket or whatever they are made out of, and the later ones had a metal head gasket, same one as the ABF in fact :)
     
  5. sdj_mk3 Forum Member

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    Ah interesting. I ordered an AGG gasket for the head swap so if that's the case its all good. Let me know what you find Phil.
    Cheers guys.
     
  6. rubjonny

    rubjonny Administrator Staff Member Admin

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    I used a metal hg in my 2.0 conversion with a mk2 head, and it made 141.9 BHP at storm developments! A bit optimistic I'd say, but at least it shows that all is well :lol:
    Edit: A pretty much std 8v made 127bhp, for comparison :)
     
    Last edited: Apr 27, 2007
  7. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Let me see if I can shed some light on this based on VW infomation and my own experience.


    2E ADY 10.1 AGG 9.6:1 All rod lengths the same at 159mm.
    2Es have the same head casting as an Audi 80's 3A 037103351H. This was touched in an earlier thread where a 2E inlet was used on my complete 3A motor installing in a MK2.
    AGG and ADYs have the same head casting 0481033351D The only difference is the camshafts used so still does not explain the compression difference.
    2E, ADY can use 0481033383B head gasket (fibre)
    ADY,AGG use 048103383D (metal) stll does not explain compression drop.
    The only non universal set explaination would come from the pistons.
    2E and ADY carry the same pistons 048107065R
    But the newer AGG carried 048107065S
    If I was to go by common sense and the above infomation I would say that your CR difference is down the piston dish/deck height differences. A burette or dial indicator and some patience can always confirm.
     
  8. rubjonny

    rubjonny Administrator Staff Member Admin

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    Toyo arnt the metal gaskets a different thickness, or was that only on 1.8 engines? (i.e. G60 metal gasket)
    It was quoted to be .2 of a mm different IIRC, would that really make a big a difference?

    If the late 2.0 gasket is the same thickness that would be good news for me, otherwise I'd be lowering my compression by using one :)

    Edit: Also I don't know if this difference was pre-or post fitting, as I'd assume the different types of gasket would crush by varying amounts...
     
    Last edited: Apr 27, 2007
  9. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Measured the metal ones at 1.9mm vs for 1.6mm fibre thing. Makes very little difference in real life. I used a metal one on my 3A hoping to cure starter kick back because of the higher factory compression. Made no difference. Resorted to Mk3 020 gear reduction starter to solve.
    Thing is with metal or without the ADY was still 10.1.
    I am sure its a question of either deck height, deeper dish or both for the AGG piston.
     
    Last edited: Apr 27, 2007
  10. rubjonny

    rubjonny Administrator Staff Member Admin

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    Ah cool, good news for me then :)
     
  11. sdj_mk3 Forum Member

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    Cheers toyotec, more good info. I'll soon see when I pop the lid on the ADY next weekend, will let you know what I find!!
     
  12. rubjonny

    rubjonny Administrator Staff Member Admin

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    lots of pics please :thumbup:
     
  13. sdj_mk3 Forum Member

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    Sorry jonny but it was an all out epic rush in the end so the pic's got passed by the board. But anyhoo it was definitely the pistons, didn't need a dial guage it was obvious by eye they were different to the AGG ones I've got lying around. Put the head on anyway and no detonation yet, goes like stink too with the extra compression, just see how it fairs when I start shoveling nitrous in there. All good! Thanks for help guys
     
  14. wcrado Forum Member

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    i'm gonna be doing the 2.0 bottom end conversion on my mk2 soon, already sourced the block, was wondering how these metal head gaskets fiited in to the equation??
    some of you are saying they will raise compression and others that they will lower it, and some that it will stay the same!

    in terms of outright performance, is it best to go for a metal gasket or not? surely if the gasket is bigger it will lower the compression having a negative effect on performance?

    But rubjonny says his metal hg made a difference??
     
  15. nibbzy Forum Member

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    yeah im doing same soon and ide quite like to know that too
     
  16. rubjonny

    rubjonny Administrator Staff Member Admin

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    Nah what I meant was if the metal hg does lower the compression it cant be that much since it still made good power at the rollers :)
     
  17. nibbzy Forum Member

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    ahhh i get ya
     
  18. wcrado Forum Member

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    right i'll stick with the cork then!

    recommended to use metal headgaskets in the thread, so thought it may be a performance issue, guess just a reliabilty one.

    would a gasket which is .3mm larger not affect the timing slightly?
     
  19. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    It would retard the cam timing very slightly but not that you notice.
     
  20. rubjonny

    rubjonny Administrator Staff Member Admin

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    it can add up if the head is skimmed too, but would it be enough to notice?
    Even if it did, just get an adjustible cam pulley and dial it back to spec :)
     

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