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Thread: Diesel Gate

  1. #201
    Senior Member Engineer's Avatar
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    Aug 2010
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    I have no idea what VW did to cheat the USA rolling road NOX tests but I know what can decrease NOX values in a DTI engine combustion chamber and they can all cause lower efficiency, lower performance, poor drivability and possible engine damage if activated on the road.

    1. Injecting excess fuel with lower air/oxygen into the combustion chamber can = diesel knock and possible piston, conrod and bearing damage especially under load.

    2. Opening the EGR valve/s early and/or over a longer time period and/or engine temperature range.

    3. Increasing exhaust valve overlap using the VVT to leave exhaust gasses in the combustion chamber to lower combustion tempertures on the next power stoke.

    VW may have used all the above or not to pass the USA rolling road emission tests and as I recall somewhere a few engines were for whatever reason run in test mode on the road and unfortunately destroyed themselves

    And not all the engines affected just require a re-map, which means that some will need other electronic and/or mechanical update components in order to function over the possible longer time spans as detailed above, which may also include the need for more efficient DPF's or AdBlue cats on some engines.
    “If you see a gap and don't go for it, you are no longer a racing driver”


  2. #202
    Senior Member Jag-Black's Avatar
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    Aug 2016
    Cambridgeshire UK.
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    Quote Originally Posted by Zero123 View Post
    VW cheated the emission tests by installing software that knew when the car was stationary and undergoing testing; the vehicle's emissions were then set to comply with the regulations which incidentally were more strict in the USA - hence why they've had to buy back and/or compensate there and not here in the UK. However, once the car was on the open road, in order to achieve better fuel consumption and increased power, the emission restrictions were relaxed and went well above the stated figures.

    You could say the same thing applies to mpg rates as they are never replicated in the real world, but then everyone knows that - but nobody knew VW were cheating and that's the crux of the matter.

    So no, the software wasn't altered just during the warm up part of the emission test but just when it knew it was being tested!
    That's my thoughts too. i don't know all the facts but understand if you set a test criteria too narrow it is more easily exploited. Some responsibility should be taken by those designing and imposing artificial test conditions.
    Jaguar x-Type 2.2D S Saloon 2006 149k Black. First Jaguar. No modifications.
    Maintenance: Sills and rear running gear repaint. Rear chassis and body under seal. Headlight revamp & T Cut. Lubricate clutch pedal, hinges and joints.
    Items replaced: LH drive shaft and bearing. Aux belt, tensioners, Crank pulley. Reverse switch. A/C compressor. Front EGR hoses. Thermostats. RH Splash guard.

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