Test regulations are constantly being updated. Consider the ever-tightening emissions, noise and barrier tests, and how far they’ve come in the last 30-40 years. The perennial problems lie in how the regulations are written, by whom, and how much room there is for interpretation.
If you look at F1, for example, there was a recent debacle over the use of radios. The rules effectively said radio communication could not be used to coach the driver. But this proved unenforceable because of the grey area between coaching and advising the driver of a safety issue. As such, that rule was rapidly scrapped.
Things don’t move quite so quickly in the automotive test world, though. There has been much debate of late about lab emissions and real-world emissions, with particular reference to how emission performance behaves outside the defined test cycles.
It’s obvious to all who play the game that there can be no all-encompassing test cycle, but most would agree that lab tests provide the best repeatability for vehicle-to-vehicle comparisons.
It is also known that emission strategies are based around the test cycles. This is a fact of life, not a condemnation.
To prove this point, try running a Japanese spec car on a Euro 5 cycle. The emissions fall off the table above 90km/h, because the Japanese cycle is unregulated above that speed. Similarly, the US FTP 75 cycle only goes to 89km/h.
The question therefore becomes, how do you make the test cycle as representative as possible, and cover as wide a range of operation as possible? Firstly, let’s consider the cycle itself.
Back in 1968 a man climbed into a car in Los Angeles and recorded a 30-minute drive around the city. This was done under the LA4 drive cycle, which became the FTP72 test protocol. The test was split into two parts, the initial 505 seconds for the cold start, and the rest for the warmed-up engine.
Today, the cycle might be considered out of date as a drive pattern for LA’s current road network, but at least it’s taken from a real-world drive.
The European cycle is, by contrast, a series of constant rate accelerations and steady-state cruises. Hardly representative. This anomaly should be improved with the new worldwide harmonized light vehicles test procedures (WLTP) cycle currently under development, but this also brings me to a second point.
Back in 1975 the US Environmental Protection Agency (EPA) realized that cars do one cold start a day and many hot starts. So it changed the cycle by adding a 10-minute soak and hot restart repeating the 505-second cycle. This became, and remains, the FTP75 cycle. The EU cycle has never included a hot restart phase, and the new WLTP cycle doesn’t have one either. A grave omission on all levels.
Where the EU cycle was updated for the better was with the introduction of the extra urban driving cycle (EUDC), which raised the maximum speed to 120km/h, 8km/h over the legal speed limit, thereby covering the full legal speed range of the vehicle.
The cold start soak temperature is currently set at 20-30°C, which is pretty good for LA, but not quite right for places such as Birmingham in the UK. Here, the problem is facility based.
Keeping a parking garage at 20-30°C all year round is relatively straightforward when the outside ambient is rarely, if ever, above 30°C. However, holding a large facility at a much lower temperature than ambient would require a large air-con plant with the resultant CO₂ emissions that everyone is so worried about. The introduction of the -7°C test placates this issue somewhat, but a +5°C to +10°C start temperature would cover a larger section of the real-world operating fleet.
My third point is one of great contention following the recent diesel scandals. Specifically, why are gasoline and diesel limits different? In simple terms, they shouldn’t be. This particular problem didn’t really raise its head when the bulk of the passenger car market was gasoline-powered, but government pressure on OEMs to tackle CO₂ back in 2003 lead to diesels being given tax breaks over gasoline. This was allowed to happen even though the legal NOx limit at that time was almost four times higher for diesel than for gasoline, never mind the particulates. In 2014, the limit gap was closed to just under three times higher, still hardly a level playing field.
Test cycles continue to evolve, but they’ll never really be perfect. The general public needs to understand this, but they also need a clear, honest and, above all, simple explanation of what can be done, what should be done and what is impractical – either because of existing technology or critical cost factors.
Mark Berry: Itinerant development engineer, apprenticed at Rolls-Royce, prior to five-year-long spells at both Jaguar Land Rover and Lotus before 25 years as a “jobbing engineer” specialist in EMS calibration and emissions, while being widely conversant in most aspects of type approval. Particular skills in managing climatic and altitude field test programs.