## 29 Eco-driving and downsizing

With climate change andglobal warming and higher price for petrol/diesel, you need to drive more carefully, slowly, economicaly. It's often called eco-driving or energy-efficient driving (see wikipedia : https://en.wikipedia.org/wiki/Energy-efficient_driving). It's a set of techniques to use the most economical engine operating ranges. But it's also very different with a manual clutch/Gearbox than for an automatic gearbox. You will have to do yourself the choice of the speed, and not only accelerate slowly, anticipate braking, and everything that is within the emissions measurement standard in terms of driving pace (now called WLTP). You have to know that the engineers who designed your car and especially the engine with the gearbox, worked a lot to maintain the lowest emissions and the associated fuel consumption for this particular cycle, supposed representative of real life. But there's also another "cycle", what we call Real Driving Emissions (RDE) and which has been implemented and defined after the Die
sel-Gate of VW. This time, it's not on a bench but in real streets with a real driver. I have worked with those drivers and I know how difficult is their job to maintain the car in the specifications of the European Standard. But if I had to resume without revealing any secrets, you have to be relaxed when you're driving and attentive to anticipate the difficulties : junctions, slowdowns, traffic lights, pedestrian crossings...

I will be a little more technical today, so I need to explain some words. Downsizing is the choice that made engineers 20 years ago to make more little engine for the same power, with the help of a turbo-compressor. For example, in the 80-90s, 
a car with 130HP had a 2 liter engine. Now, you can find the same power with a 1,0 or a 1,2 liter engine and sometimes with more torque than the old 2 liter. The problem is that an engine has it's own "engine mapping"", a set of settings that manages operating conditions such as operating temperature, throttle position, air-fuel mixture quality". I could show you some beautiful graphics and why it's called "mapping" (it's like a 3 D map on a screen)...But all you have to know is that you must be close to the ideal operation provided for by this mapping. That's not written in the manual but you have instructions to help you on the dashboard.

The last time I have driven a car, it was a f....g SUV with a small 1,2 liter 3-cylinder engine of 100 HP for 1200 kg which is a quite good result. I had a fuel consumption of only 5,5l/100km (51 mpg) because I used a Eco-driving mode on this manual clutch basic car. All I had to do was to change the gear ratio as indicated on the screen of the car. But I need to look at the road to. After a while, you can make it by ear, or just watch the rev counter needle for the engine speed. It's often after 2000 RPM that you have to use the upper gear ratio. So you can consider than your ideal engine speed is between 1000 and 2000 rpm, and that's tiny if you consider that the engine can do more than 7000 rpm, and the "red zone"is after 5000rpm. With a big engine, you could do a quite good result like that but you haven't such big differences between the lower and higher engine speed. Now it's very different with a turbo-downsized engine. When you use more than 2500 rpm, or when you accelerate violently, the turbo kicks
 in and the fuel consumption can be 2 or 3 times higher than at the ideal engine speed. For an hybrid car, it's replaced with the use of the electric engine at low speed and the Internal combustion engine is used to add power at its ideal engine speed. But it's an automatic gear-box and you can't choose the gear-ratio.

When I was learning to drive, that was not what they explained to me and I used to change the gear ratio at 3000 - 3500 rpm. I only had to be smooth on the acceleration to lower my speed. For a long time, Mazda did the opposite of downsizing with bigger engines with a particular engine-mapping: A very smart approach because it's less restrictive for the user. And you can see some very good fuel consumption results for Mazda Skyactiv engine, even I marketing have used the name for all. Their small 1.5 liter is often better than the downsized 1.0 or 1.2 liter of the others. But only because they thought differently. My old father did not understand how to use it's 1.2 liter engine because he was used to drive with bigger engine for decades. And the information/help on the dashboard is boring. As I said, after hours you can use your ear to drive and to be an eco-driver. But sometimes, you have to use the full power of the engine. It's perhaps in 1 or 2% of your time of driving. To show good figures for fuel-eff
iciency and 0 to 100 km/h is hypocritical. You won't have both and that's why the available power in such cars is too high, compared to what you really need for eco-driving (you don't need power to overtake!). With the smallest engine of this SUV, I had all that I need to make a comfortable travel. I just needed more power to climb with 5 passengers inside but was it 100HP or 75? If I remember my old Peugeot 206 with it's 75 HP engine in the mountain, I know the answer but all is related to the weight of the car, as I said last week. With 200kg more or 20% more weight, I need 20% more power...In that case, 90HP would be enough in that 1200kg SUV, or a 13 kg/hp ratio. Look at what we used in the 70s, 80s, 90s and now...
Just figures : A Ford Escort mk II of 1975 gad a 14,6 kg/hp ratio with it's 1300 version (60HP). A VW Golf of 1986 had a 11,6 ratio for the 1.6 version (75HP)). A Renaut Megane of 1995 was at 10,6 for the 1,6 16s version (90HP). A Toyota Corolla of 2005 had a 10,4 ratio for the 1.6 version (110HP). in 2015, a Peugeot 308 blue HDI diesel had a 9,6 ratio for its 1.5 HDI engine (130HP). Always more power, more performance that you don't need. Now you have to think that progress is not that but is to be smarter in the choice of the engine, of what you really need. Highways won't be long limited at more than 120km/h in Europe and even Germany will change on than subject because new drivers will also change with the use of EV cars. the 30km/h limitation in more and more cities is changing the way you use the gearbox. I have also seen different uses and habits in Asia with very low revs and less gearbox use. The world is changing... and you? 

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