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The methodology here is highly suspect. First of all they are using an AWD dyno which can be unlinked to test a FWD or RWD car. It is expected that the car will

The methodology here is highly suspect. First of all they are using an AWD dyno which can be unlinked to test a FWD or RWD car. It is expected that the car will dyno lower when driving the rear wheels as well as the front. Not only does it have to turn the drums of the dyno but also the rear wheels, tires, and brakes of the vehicle. Second, a key component of the cheat as reported by the media is keying off of the presence of the OBDII instrumentation. As far as I can tell they did not have any way of simulating this condition.

kw71 11y ago
Not all emissions tests are conducted with OBD2 link. In some relaxed regimes, OBD2 interrogation is the only component of the emissions test, and the car passes if the car determined there is no faults. I lived in a county with emissions testing and the OBD2 link was used as a pre-test before the dyno run, and to feed the VIN number into the state's computer to provide some assurance about the identity of the car being tested. Some vehicles, like my Toyota, indeed behave slightly differently if there is a diagnosis computer connected. I don't know if this applies to the OBD2 link as well as the toyota-specific connector under the hood, but it's pointed out in the factory shop manual. At any rate this knowledge has prevented me from trying the "scangauge" type of data collection device.
msandford 11y ago
Not really. The car is a FWD car. So when the rear wheels aren't being spun up, the car should produce ever so slightly more measurable power instead of less. Because, as you stated, it didn't have to spin up the rear wheels, etc. The dyno can tell if both wheels are being driven or just the front ones. If it couldn't, then the results wouldn't be off by 10% but they'd be off by 50% as the dyno wouldn't understand that by having the two drums linked they got twice as heavy and it'd do the calculations based off of the inertia of a single drum instead of both drums.
rasz_pl 11y ago
>will dyno lower when driving the rear wheels as well as the front well, it did BETTER on four wheels spinning, so how is that a bad test?

kw71 11y ago

Not all emissions tests are conducted with OBD2 link. In some relaxed regimes, OBD2 interrogation is the only component of the emissions test, and the car passes if the car determined there is no faults. I lived in a county with emissions testing and the OBD2 link was used as a pre-test before the dyno run, and to feed the VIN number into the state's computer to provide some assurance about the identity of the car being tested. Some vehicles, like my Toyota, indeed behave slightly differently if there is a diagnosis computer connected. I don't know if this applies to the OBD2 link as well as the toyota-specific connector under the hood, but it's pointed out in the factory shop manual. At any rate this knowledge has prevented me from trying the "scangauge" type of data collection device.

msandford 11y ago

Not really. The car is a FWD car. So when the rear wheels aren't being spun up, the car should produce ever so slightly more measurable power instead of less. Because, as you stated, it didn't have to spin up the rear wheels, etc. The dyno can tell if both wheels are being driven or just the front ones. If it couldn't, then the results wouldn't be off by 10% but they'd be off by 50% as the dyno wouldn't understand that by having the two drums linked they got twice as heavy and it'd do the calculations based off of the inertia of a single drum instead of both drums.

rasz_pl 11y ago

>will dyno lower when driving the rear wheels as well as the front well, it did BETTER on four wheels spinning, so how is that a bad test?