The latest run from Canberra to Sydney and back produced a very good result. Temperature range was 10°c to 22°c on the way up and 20°c to 13°c on the way back.
I filled up at Sutton Forest, halfway to Sydney. After 796.5 km, of which about 20% was city driving, I put in 34.49 litres for an average of 4.3l/100km Cost was $1.49.9 for Shell 91 RON. (The HSI displayed 4.1l/100km.)
From fill-up to Newtown and then the City ended as 132.9km for 3.4l/100km at an average of 86km/h. Adding 5.8% to the HSI display gives 3.6l/100km. (Corrected figures shown in italics.) That’s my best ever run into Sydney, though it doesn’t include the hills between Canberra and Sutton Forest.
Return trip was quite cool. Sydney didn’t get very warm on Saturday and the temperature dropped steadily as we travelled South. I used 2/3 lower grill block on the way up, in case I encountered temperatures much above 18°c on the way up. After a brief stop on the way back, I restored the full grill block. Upon return, the tank trip was 418.8km, 4.0l/100km (4.2 corrected) at 79km/h.
The Canberra to Sydney loop was 564.0km, 4.1l/100km at 80km/h.
Why the improvement from previous loops?
I’d put it down to never using the cruise control.
The beauty of the Prius’ cruise control is that it can regulate speed very well. If you are coming down a steep hill, it can use regenerative braking to hold your speed. (If the HV battery is already charged, the engine will be forced to run to “burn off” some of the excess charge. This is also the only time that you would use the B (Brake) position; to prevent overcharging.)
Steep hills can be easily scaled by changing to the PWR Mode so that the speed doesn’t decrease as much before the acceleration takes over. Leave it in ECO Mode and the speed will drop so far that all resources will be called upon to leap back to the set speed; a far less economical way to drive.
Radar cruise control in the iTech is even spiffier. Except that every press of the accelerate or decelerate lever changes speed by 1 km/h and every long press by 10 km/h. While this is very logical (Mercedes-Benz use this method) and is more accurate than holding until the desired speed is reached, it did catch out Steve “Woz” Wozniak, allegedly.
Freeway Driving without Cruise Control
How can I even suggest such a thing? Surely CC makes a journey bearable. Well… the Canberra to Sydney run is not very flat and once you reach the flat sections, the traffic increases. Neither are ideal conditions for cruise control. And the Prius will allow me to take over from the CC, however results can be mixed. If I am pushing the accelerator, say to speed up before a steep hill, but the car dips below the set speed, CC will not try to maintain the set speed. Take my foot off the accelerator, the CC springs back into life. I expect my foot to complement CC, not override it.
ECO Mode makes the accelerator less sensitive, which in turn makes it easier for the right leg to control speed. Using Pulse and Glide techniques, long downhills can be used to charge the HV battery, or increase speed. In short, you can control what the CC can’t see.
Having throttle control allows me to find the Super Highway Mode for very low consumption driving at high speed. I was able to maintain 2.0 – 3.0 l/100 km at 110km/h for flat and slightly downhill sections by keeping the Ignition Timing (IGN) in the range +12-+16. In fact, I was merely reading the instantaneous FC figure from the Scangauge-e rather than resorting to maths.
Because the accelerator pedal is quite light in ECO Mode, driving is not a chore. And since I don’t have radar CC, I find myself cancelling CC when approaching slower traffic anyway.
I’ll use the CC selectively in future.