Wednesday, July 27, 2011

Hyper-miling in my '09 HCH

Recently, I've learned more about hyper-miling in my Civic Hybrid. This isn't something you learn in driving school. Or from the Civic manual. Luckily, there are people out there who take the time to discover what their cars can and cannot do, exploit it to the limit and post their findings online.

Unlike some hybrid cars that have a dedicated EV mode, where nothing but the electric motor is driving the car until the battery runs down, series hybrids like the Civic can't do this. But it has been a known fact that the Civic hybrid does have the capability to run only on electricity when the conditions are right. Honda just doesn't bother to tell you how to do it, or how you would even know you're doing it. It's not like there's a light on the dash that comes on when you're in fully electric mode.

It all has to do with the state of charge (SoC) meter to the left of the tachometer and the multi-function display that shows coolant temperature or mileage to the left of the speedometer. In this case, you want the display selected to show mileage, not coolant temperature.

Now as I said before, Honda doesn't quite explain this to you in full but when you step on the gas, how far you press and with how much aggression, completely affects what happens next. The more 'gas' you summon, you could get a combination of more engine revs coupled with assist from the electric motor. But if you ask for more gas less aggressively, you might get more engine RPM but without any electric boost. So the key is to have a much more sensitive foot. It's kind of like having turbo. You only get it when you need it.

When you ease off the gas, again, it all boils down to how quickly you let off. A sudden, complete removal of your foot causes the engine to slow down, then shut off and the energy from your speed is recouped into electricity. Now a lot of people are fooled into thinking that while they are coasting that the engine is still running, because the tachometer still registers at about 1000-1100RPM, but in fact the fuel system has been completely shut down. The only way you would know that is by observing the l/100km gauge to the left of the speedometer. If that sucker is registering nothing (as in 0 litres per 100km), it means there is no gas being used - the engine may be turning, but it's essentially off. To prevent this from creating engine drag, Honda does a few tricks with the valves etc. So, as you quickly let off the gas pedal, you go from using gas and possibly electricity, to the engine being off while recharging the battery with no real transition. But if you very gently ease off the gas pedal, something wonderful happens. First, the amount of electricity used falls off to nothing (using the turbo analogy - the turbo shuts off). Then the amount of gas used drops off. Keep letting your foot off the pedal and you use no gas (the engine shuts off), but you don't go so far as to engage the recharge feature just yet. Now you're coasting. No energy output, no energy capture.

Why would you want to coast? To maintain speed as long as possible while using no fuel. You're now taking advantage of the Civic's great aerodynamics and the low rolling resistance tires to coast farther. If you ease off the pedal some more, the gauge shows you starting to recapture energy by recharging the battery. The more you let off the pedal, the more you recapture, depending on the amount of inertia you have working in your favour. Downhill, you collect a lot more energy than on an even road. Going up hill - forget it, you're not recapturing anything, you're just trying to keep the car moving.

If you press the brake pedal, you now use the electric motor as a far more aggressive generator and the meter shows even more energy re-capture. But if you stopped easing off the gas pedal just as you reached perfect coasting condition and then ever so gently press back down on the gas pedal, you will turn into an electric car. You are now driving on pure electricity - no gas. You can tell because the IMA gauge is showing a boost, but the mileage gauge is still showing 0l/100km. On a flat stretch, it's not quite enough to maintain speed, but your coasting will last 2-3 times as long as without any help. If your going slightly downhill, you can actually pick up a bit of speed using no gas at all.

This all may seem like a lot of work, but if you keep your eye on the mileage gauge to see how much gas you're using (if any at all), you can increase your mileage in a big way. I average 5.3l/100km now (44mpg). With a lighter foot and an eye on the gauges, I could get that down to 4 (60mpg). I've even heard stories of short trips that resulted in as little as 2-3l/100km (80-100mpg).

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