We want the best of all worlds, and messages from government try to convince us this is deliverable.
We want cars that are cheap and that don’t pollute the environment or trigger climate change and aircraft that allow us to holiday in the Bahamas without building new runways or making life unbearable under their flight path.
In reality, all these require compromises and the design of diesel engines is no exception. We were encouraged to switch from petrol to more efficient diesel cars to reduce carbon dioxide (CO2) emissions, but they also produce oxides of nitrogen (NOx) which pose a serious risk to health.
The designers of car engines must obtain the best (or possibly least bad) compromise between performance, flexibility, fuel efficiency, CO2 emissions, carbon monoxide, and NOx emissions. Given the importance of meeting CO2 and NOx emissions standards, it is hardly surprising if they adjust the engine control unit (ECU) to ensure that, under test conditions, the optimisation is tilted towards emissions reduction, rather than performance.
This is not cheating, it is normal practice when trying to meet a range of conflicting requirements.
But what happens if, even with the best optimisation techniques, it is not possible to meet all these conflicting requirements? The extreme option is to set up an ECU with two completely different settings – one for normal driving and the other for when it is being tested for NOx emissions. By reading sensors such as the warning detector for the driver’s seat belt and the sensors that compare the speeds of front and rear wheels, it would not be difficult for the ECU to detect when the car is in the lab and select the appropriate settings – an action that can only be described as fraudulent.
The greater the expectations and pressure placed on the design team, the greater will be the temptation to move from simple optimisation to something more serious.
We like to think that environmental benefits, like emissions reductions, can be
obtained by creative engineering without resulting in compromises in cost or performance.
It is politically unpalatable to say that high-speed rail or a third runway at Heathrow will increase emissions, but we need to face reality. Meeting the 2050 carbon emission targets is unlikely to be compatible with unregulated growth of transport without fiddling the figures. Similarly stringent CO2 and NOx limits may not be compatible with the sparkling performance and falling motoring costs we have come to expect.
If we are not prepared to accept compromises, we must expect more cases where reality fails to meet the theory.