[Stoves] "Those of us who believe that the WBT is critical to stove improvement"

Crispin Pemberton-Pigott crispinpigott at outlook.com
Thu Dec 7 12:26:04 MST 2017

Dear Andrew

Those are interesting questions. My answers are:

Manufacturers did not distort the test, they took advantage of its inherent weaknesses plus the wink and nod of the inspectors.  ‎As soon as I heard about the issue I blamed the drafters of the Standard. It is bleeding obvious that you could drive a Mac Truck through the loopholes in it.

It is a emissions and fuel efficiency test and everyone was 'cheating' (from my perspective as a writer) because the authors and test administrators allowed it. A lot of time spent writing a Standard is closing such loopholes without making it a specification standard (it is a performance standard which is harder to get right).

The Indian kerosene stove standard is a Specification Standard and you can't cheat at all, but it stifles innovation.

The second point is that the tests did not involve driving the car, ever. Well...duh!

For those who are not aware of what the 'cheat' was, a diesel engine's emissions depend on how much fuel is injected into the hot cylinder on each firing stroke. The NOx produced depends a great deal on the temperature and pressure generated when the fuel burns. More fuel, more pressure etc. The engines all pass if the upper limit for NOx was met, and no more fuel is permitted, limiting the engine power. The cheaters invoked the limit during testing but when driving, permitted the fuel volume to be higher famously giving it more power.

A car spends very little time running at full power anyway, so on average it probably met some standard, but that is not how it is worded. Actual or average emissions produced while driving is not the basis of the regulation. The requirement is decontextualised and based on the maximum possible value, which is of course 'full throttle'. The computer on board was programmed to detect when it was being tested and redefined what 'full' means.

The total emissions in typical use never came into the discussion, only the maximum rate, even if only for one minute.

The hugh Bechtel-built power station disguised on the waterfront in San Francisco that no one realizes is there, faced a similar problem. When first started, it emitted 'too much' CO accelerating up to speed (or was going to) and the City wouldn't let them start it! It didn't matter that it was going to emit very little for the rest of its operating life. It was going to emit some exceedance number for a few minutes and that was that.

Eventually the engineers figured out how to accelerate it slowly over a long time‎ and eventually brought it up to speed. That is the equivalent of putting an electronic stone under the accelerator pedal of a non-compliant diesel engined car. It is sort of allowed in San Francisco but not the EU.


On 7 December 2017 at 02:54, Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:

>The protocol used to test NO emissions in diesels was 'gamed' rather easily. Adopting a protocol that is difficult to game would be a better option.

It's an interesting concept in itself; that countries stipulate a
standard for engines to reach before they can be sold into a highly
sophisticated market with high standards for testing and:

1: a major player can distort the tests

2: the tests don't relate closely to real use anyway

I haven't bought a new car so it hasn't affected my choice, so why
should a stove tested to any standard affect a consumer?


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