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Thread: dyno figure weirdness.

  
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    theblueraven's Avatar
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    dyno figure weirdness.

    just quickly guys, i have and interesting scenario.

    my astra turbo has recently had a few dyno runs before and after an aftermarket ecu installed (interceptor style). Car only has 30000 miles on it...

    my mods list is:

    3" dump pipe/3"cat/2.5" cat back all stainless
    k&n pod filter with heat sheild
    custom 600x180 front mount intercooler(an power pipe & 2" cooler piping)

    after i had that lot put in it felt a hell of allot quicker than stock as you would imagine.

    but here are my dyno graphs from the same dyno (all showing at the wheels figures!!! here in australia nobody does 'estimates' at the engine), before and aftrer the installation of the haltech interceptor. before anyone asks the traction control was off and the fuse was pulled (but apparently pulling the fuse didnt make any difference)

    before

    after



    it just doesnt make sense to me, the car pulled hard before the ecu, harder than my calibra when i had nitrous in it and it showed 130hp at the wheels, so i just dont know how it could show only 90hp. after the tune it holds 1.1bar of boost to redline and feels like a rocket! but only 145hp? less than stock? anyone have any idea why my car would read so low on the dyno? i can promise you it will eat a stock astra turbo for breakfast now....

    i am happy with the power, but confused about my results...

  2. #2
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    wywywywy's Avatar
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    What a strange graph... it uses KPH instead of RPM for the X axis?
    Astra Coupe Turbo Project Log KW var2, BK299, Apexi, HID, Angel, Leather Cobra, Phoenix Gold, GT/R2, Fluted, DV26D, Pre/Sports/Catback, CarPC, B&M, VXR Turbo, Tarox-10, Phase 3! Car is for sale!

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    reggie69's Avatar
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    dodgy rolling road maybe?

    try somewhere else and see what happens...

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    Try a new AFM i think vxgsiturbo on here had the same problem before only pulled about 80 as standard but once changed was good as new
    Zaffy VXR on the beat

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    never had a warning light or anything that would make me think the afm was on its way out...like i said on the road it feels great, i thought there might be something else but i dunno :P

    how do i tell if it the afm needs changing or not?

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    vxgsiturbo's Avatar
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    i had no lights on mine either and i felt fine on the road but the air mass was the problem

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    Enkidu's Avatar
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    BTW mate its been proven that the flywheel calculations are far more accurate than the @ wheel figure.

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    how can that be true??

    when the calculations for flywheel use the at the wheels figures to arrive at the flywheel estimate? the measurement is taken at the wheels then put through a formula to estimate flywheel power, taking into consideration any losses through transmission/wheels etc...

    so sorry mate, there is no way a calculated or estimated figure is more accurate than the original measurement taken at the wheels. All dyno competitions across the world only use at the wheels figures.

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    There was a post on here somewhere that explained it...

    Basically the @ wheel figure can be altered really easily by lots of key things which will either give you a high or a low reading....

    Strap tightness
    Gear used
    Tyre pressure
    Gear box temp

    When the computer calculates the @ fly figure it has been tested by some big names here in the UK that pretty much within a couple of bhp its spot on... Do a search its here somewhere, thorney etc posted. I used to think the same as you until I read that.

    Plus its also been tested with standard cars that come up trumps with the manufactures given flywheel figure AND its nice to compaire your car once modded to the manufactures quoted figure to see how much extra you have.

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