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audi s3 compression readings too low?

Discussion in 'A3/S3 Forum (8L Chassis)' started by darren t, Sep 7, 2012.

  1. darren t
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    darren t Member

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    [Sep 7, 2012]
    hi there i have recently bought an audi s3 225bhp i took it for a rolling road at midland vw and it only made 230bhp 256lb of torque boosting 1.3 bar map as asking for 1.5 i was told but was advised maybe actuator or maybe rings so i have contacted previous owner an he advised me it has had a new turbo recently and a rebuild 10000 ago by halesowen engines with forged pistons and rods im a bit gutted rally owning the car for 2 days i thought it was a bit slow but lol that cant be right i have several logs 216gs of air was my best was advised rings as boost held 1.3 but not the 1.5 it was asking for??? contacted tsr who with recipt i have advised they were low com pistons slightly would 155 150 150 155psi be too low? ie wworn ring i have adjusted actuator hit overboost so ive took it back a turn feels quicker but surely wont have made 45bhp?
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  3. superkarl
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    superkarl MAN OF STEEL

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    [Sep 7, 2012]
    start with looking for a boost leak if its not hitting 1.5bar requested.
    lower comp pistons and not meeting boost will give lower compression readings, but im not entirely sure if yours is LOW.
    i've seen people report 180-190psi before.

    do you use any oil?
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  4. superkarl
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    superkarl MAN OF STEEL

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    [Sep 7, 2012]
    post the logs. some more experienced people may be able to advise you.

    what turbo is it?
    why would the previous owner fit lower comp pistons?
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  5. darren t
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    darren t Member

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    [Sep 7, 2012]
    only had it 2 days been advised actuator turned it today definatly a bit more power now but not 45bhp lol my agu engine made 165/170s im thinking worn rings?
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  6. darren t
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    darren t Member

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    [Sep 7, 2012]
    i was told this by tsr who i have found recipt off i gave them numbers they told me what they were he said slightly lower than standard i said 155 he said thats ok????i personaly think its too low????
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  7. darren t
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    darren t Member

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    [Sep 7, 2012]
    how do i attach some logs?
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  8. karl210
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    karl210 Member

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    [Sep 7, 2012]
    i thought these engines had a low compression ratio as it is let alone putting low comp pistons in, why would anyone build an engine without doing research? mine is all standard and my amk is putting out pretty much 180psi on all 4 and its done 175k
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  9. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Sep 7, 2012]
    Don't mess with the actuator too much... you will end up getting a huge spike in boost... this would be rather bad...

    Have you had a smoke test to check for leaks? compression seems a little low tbh... std comp ratio for an S3 is 9:1 and from memory should be in the 190psi region...

    Actuator pre-load should be around 3 full turns from it nipping the wastegate shut...

    <tuffty/>
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  10. darren t
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    darren t Member

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    [Sep 7, 2012]
    agu engines have a higher comp ratio apparently?
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  11. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Sep 7, 2012]
    Yes... 9.5:1

    VAG 20v engines don't seem to mind higher comp ratios... I run Ibiza Cupra pistons (same as AGU ones) at 9.5:1 on a big turbo with no issues and the TFSI comp ratio is somehing like 10:1

    <tuffty/>
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  12. darren t
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    darren t Member

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    [Sep 7, 2012]
    hope fully monday for leak test bloke at tsr said 155 is about right lol even with 155s on all cylinders pulling 216 gs of air egts at 7000rpm were 875 iat temp 28 fuel bang on he said that requeted boost wasnt being met at 1.3 bar as map is asking for 2550mbar max?
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  13. Lewis583
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    Lewis583 Active Member VCDS Map User

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    [Sep 7, 2012]
    Just checked Autodata and it says that for the BAM it should be between 10-13bar (145-188psi).

    Did you perform "dry" compression test and also a "wet" compression test?

    By "wet" i mean, have some oil put in the bores(only a little) to help with sealing the rings. By performing both tests, if there is a big difference between the 2 test readings then rings could well be worn. The only other way to test for worn rings would be to remove and inspect visually.

    Most likely cause IMO would be a boost leak. As Tuffty suggested, a smoketest would be the best/cheapest way forward.
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  14. darren t
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    darren t Member

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    [Sep 7, 2012]
    Dry test was performed so there looking low??? Is it possible to remove pistons without removing crank?
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  15. darren t
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    darren t Member

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    [Sep 7, 2012]
    I have no boost leaks but say I had that extra 0.2 bar would this make up for 45bhp power loss?
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  16. Lewis583
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    Lewis583 Active Member VCDS Map User

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    [Sep 7, 2012]
    Well at 150/155psi they're within spec although at the lower end of the scale. Don't forget you have lower compression pistons fitted to the engine.

    The crank can stay in situ, however the head has to come off as the pistons are removed from the top.
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  17. darren t
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    darren t Member

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    [Sep 7, 2012]
    So we're could this lost power be?? How do I attach some logs?? Holds boost ok feel a lot better now actuator has been adjusted will find out what turbo it has on!!!
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  18. Lewis583
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    Lewis583 Active Member VCDS Map User

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    [Sep 7, 2012]
    The cheapest place to start looking for lost power would be to check the intake side of the engine for any split/detached pipes, starting from compressor housing right up to inlet ports on head.

    Smoketests are fantastic at finding leaks quickly and easily.

    To attach logs:
    • Open log in Excel(or similar)
    • Take print screen of relevant section of log (the power-run(2,000rpm to redline(or as close as possible) in 3rd gear)
    • Open Microsoft Paint and press CTRL+V
    • Save the image and upload it to a image hosting site (eg. Photobucket/Imageshack)
    • There will be a share option after uploading, copy the IMG code and paste it in a comment on here
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