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  1. #1
    Breezey's Avatar
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    How accurate is the G/S reading to calculate bhp

    Hi guys,

    Car felt a little slow so i went out and did some logs with vag com all the usual stuuff like actual/requested boost was spot on so i decided to log the MAF its a spanking new one as my old one had it and i got a peak reading of 181g/s is this possible from a 210 AMK lol, its my understanding that you multiply the maf reading by 1.31 or is it 1.25? so 181 * 1.31 = 237bhp = extremely unlucky 181 * 1.25 = 225bhp = still pretty unlikely thoughts?

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  3. #2
    Welly's Avatar
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    The way I do it, and the way that seems to be generally accepted is is divide by 0.8.

    181 /0.8 = 226.25.

    May be slightly overreading - however that is healthy air flow for a 210.
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  4. #3
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    Hi mate.

    The formula that I've always gone with is simply MAF reading (g/s) / 0.8.

    You should therefore be hitting about 226bhp. Does seem like a lot for a non-modded car though. It is very cold, I guess...

  5. #4
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    Quote Originally Posted by Welly View Post
    The way I do it, and the way that seems to be generally accepted is is divide by 0.8.

    181 /0.8 = 226.25.

    May be slightly overreading - however that is healthy air flow for a 210.
    Doh...beat me to it!

  6. #5
    Breezey's Avatar
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    Cheers lads yea it is really cold im sure factory figure is done at normal temp so im guessing most will be over reading this time of year.

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    sorry to hi-jack but im having someone do some logs on my S3 this week, i've never used vcds and the guy that has it is a bit of a noob. Could you explain how to view requested boost VS actual boost and how to get a g/s MAF reading please. Thanks

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    Breezey's Avatar
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    I will do my best but im not terribly farmiliar with it,

    Ok quick guide for you but if you get stuck here is the rosstech link lots of stuff in there : Ross-Tech: VCDS Tour


    Here is a list of measuring blocks and what they do : http://www.ross-tech.com/vag-com/m_blocks/



    Should see a screen like this when you first start the program, you want to select control module :





    Then you want to select 01 - Engine :






    Then 08 - Measuring blocks :





    And here you have it block 002 will show your MAF reading and 115 will show actual and requested boost then just hit graph







    Hope this helps.


    Cheers

    Ben


    Edit : oh and dont get carried away thinking your car is running 2.0 bar pressure as the atmospheric pressure is 1bar so you should see around 1800-1900mbar which equates to 0.8 bar which is about 11 psi
    Last edited by Breezey; 7th December 2010 at 00:30.

  9. #8
    Chugger

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    you can either /0.8 or x.1.25

    either way will give you same result. This cold dense air will give you very good airflow, im quite tempted to see what mine will peak to.

    181 is very good considering im only just over 190 on a remaped car.
    57 A3 2.0 TDI Sportback (140)

  10. #9
    Welly's Avatar
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    Quote Originally Posted by SamiG View Post
    sorry to hi-jack but im having someone do some logs on my S3 this week, i've never used vcds and the guy that has it is a bit of a noob. Could you explain how to view requested boost VS actual boost and how to get a g/s MAF reading please. Thanks
    This is in the FAQs.... How to log with VAG COM.
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  11. #10
    Prawn's Avatar
    My other car is a MINI!!!!

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    Quote Originally Posted by sportstractor View Post

    181 is very good considering im only just over 190 on a remaped car.
    haha. your car is ghey! My old ko3S made 189g/s :P maybe that's why it's faster than yours :P
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  12. #11
    Welly's Avatar
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    Quote Originally Posted by Prawn View Post
    haha. your car is ghey! My old ko3S made 189g/s :P maybe that's why it's faster than yours :P
    Mean..... lol.
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    Quote Originally Posted by Prawn View Post
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  13. #12
    Chugger

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    lol prawn, and where is your old k03s now. We can all play the making up numbers game... but we all know... s3's are the elite. A3s are for chavs and/or homos and/or jews.

    Also how is your front wheel drive car performing in the snow?

    Cheers then :P
    57 A3 2.0 TDI Sportback (140)

  14. #13
    Prawn's Avatar
    My other car is a MINI!!!!

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    Quote Originally Posted by sportstractor View Post
    lol prawn, and where is your old k03s now. We can all play the making up numbers game... but we all know... s3's are the elite. A3s are for chavs and/or homos and/or jews.

    Also how is your front wheel drive car performing in the snow?

    Cheers then :P
    It's sat on my drive, waiting to be stripped and have the sparco seats fitted before christmas, then the full weld in multi point cage from custom cages will be arriving in january my FWD polo is just fine in the snow thanks!

    Anyway, back on topic:

    The maf/0.8 rule seems to be fairly accurate from what I've seen. On the road I get 183g/s, suggesting 229bhp. On bills dyno it made 224bhp, although interestingly, airflow on the dyno was only 175g/s, suggesting 219bhp, when it made 224.

    What's important to remember though, is that any boost leaks will skew the reading hugely, as it'll still be drawing in the air, but loosing some of it through the leak. So maf readings may suggest you have 225bhp, when infact you have a leak somewhere and it's working the turbo harder to make requested boost, so drawing in more air!
    -------------------------------------------------------------------------------------------------

    Prawns TFSI Turbo'd 1.8T Track Car

    But I know nothing so ignore me.

 

 

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