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How accurate is the G/S reading to calculate bhp

Discussion in 'A3/S3 Forum (8L Chassis)' started by Breezey, Dec 6, 2010.

  1. Breezey
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    Breezey Member

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    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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  2. Welly
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    Welly VX220 SC Driver :)

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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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  3. nick4501
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    nick4501 Member

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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...
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  4. nick4501
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    nick4501 Member

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    Doh...beat me to it!
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  5. Breezey
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    Breezey Member

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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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  6. SamiG
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    SamiG On Boost, ish.

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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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  7. Breezey
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    Breezey Member

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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 :


    [​IMG]


    Then you want to select 01 - Engine :


    [​IMG]



    Then 08 - Measuring blocks :


    [​IMG]


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


    [​IMG]




    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: Dec 7, 2010
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  8. sportstractor
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    sportstractor 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.
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  9. Welly
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    Welly VX220 SC Driver :)

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  10. Prawn
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    Prawn My other car is a MINI!!!!

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    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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  11. Welly
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    Welly VX220 SC Driver :)

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    Mean..... lol.
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  12. sportstractor
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    sportstractor 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
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  13. Prawn
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    Prawn My other car is a MINI!!!!

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    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!
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