yaris v prius economy

[Heidfirst]

1 hour ago, wass said:

I am glad that it isn't my imagination. So somehow the prius with a larger shaddow manages a better drag coefficient than the little yaris... or does drag coefficient relate to something like kg force per square cm of profile? So the QE2 , for the sake of illustration ,could have a drag coefficient of 0.3 despite it being so blooming big?I suppose also that if one cant store so much energy from coasting down hills and braking, then that is essentially wasted fuel. So it would make sense that the Yaris has less battery capacity.

https://en.wikipedia.org/wiki/Automobile_drag_coefficient#Reducing_drag

[danowat]

13 hours ago, wass said:

I am glad that it isn't my imagination. So somehow the prius with a larger shaddow manages a better drag coefficient than the little yaris... or does drag coefficient relate to something like kg force per square cm of profile? So the QE2 , for the sake of illustration ,could have a drag coefficient of 0.3 despite it being so blooming big?

Drag isn't just about the profile the object presents to the air, but also what that profile does to the air after it passes over it, turbulence = drag, the Prius has a number of air detachment surfaces on it that remove some of the turbulent air, the easiest one to see is the rear screen, watch what happens to any rain on the rear screen in the prius, and what happens to it on a normal car, you can also see but the way dirt buildup on the rear of the car doesn't have the patterning of other cars.

You'll also notice that the Prius is quite tall and narrow, thus reducing it's frontal profile.

 

[wass]

Oh , so the lesson to be learnt here is more along the lines of cd values. Other cars are designed to sell more on appearance rather than fuel efficiency and economy is taken care of by slapping on a label which tells the owner," eco,blue, green,efficient,e,i, ionic jet etc" rather than designing a Shell which is aerodynamic and then incorporating the ecobluegreen mechanicals/electronic wizardry as has been done with the prius gen 2 onwards and... the mark 1 Honda  integra ( which didnt sell particularly well because it looked a bit odd). Unlike Toyota, Honda seemed to give up with the slightly different styling and brought out the mark 2 integra which looked a little more conventional and consequently sold more easily.

CD values must be very significant factors in choosing an eco vehicle . Its not just the labels and mechanicals and electronics.

[PeteB]

1 hour ago, wass said:

CD values must be very significant factors in choosing an eco vehicle . Its not just the labels and mechanical and electronics.

Absolutely.  I don't know if it's still the case, but when launched the Gen 4 Prius (15" wheel) cd of 0.24 was one of the 5 best in the world for production cars, equalling the impressive Tesla Model S, which has a slightly easier job because there's no combustion engine, so no radiator, so no grille.

The 17" models have a slightly higher cd (0.26 For Gen 4) because the wheels are wider (circumference is almost identical - more metal, less rubber across the diameter), presenting a larger area that needs to push air out of the way.

It is said Toyota spent millions refining the Gen 3 Prius to get the cd down to 0.25 (15") from the Gen 2's 0.26 (actually a major improvement despite the small numerical value).  To my mind,  then putting 17" wheels on the 2 trim levels that sold most was shooting themselves in the foot, having spent so much, and making the T4 & T-Spirit worse than the Gen 2 at 0.27.

[PeteB]

In case anyone is wondering why many of the super-sleek looking and frightfully expensive supercars don't push the Prius further down the list, it's because their deign, while slippery, concentrates on producing down-force to press the tyres harder again the road and 'glue' the car to the road when cornering at speeds that would separate me from my lunch!

[Steve Whits]

Since 31st May my Auris has returned the following mpg 54.16, 49.49, 59.54, 70.4, 69.61, 64.49, 44.28 the higher mpg's underlined were on holiday in Scotland with long journeys with no or very little traffic. The other figures are short journeys in Sheffield.

The last 4 fills for the Yaris since April are 54.71, 52.69, 60.1 and 54.97 which are mainly travelling to and from work (a journey in traffic of about 8 miles) with a couple of longer trips thrown in travelling across the Pennines. 

Not too scientific but I think the Yaris is better around town than the Auris but the Auris seems to be better on a long run

 

[johalareewi]

My wife has the mk1 hybrid yaris which she got after having a petrol automatic yaris. The hybrid yaris gets better mpg than the petrol auto did but as you say, nowhere near what my gen3 prius got at the time (gen3 is now a pip).

As well as the drag factor and small hv Battery, the yaris isn't easy to drive economically. The hsi is tucked away behind the steering wheel and isn't easy to see while driving.  So i just end up driving it like an automatic.

There doesn't seem to be the choice in lrr tyres that the prius has and there are 2 published tyre pressures. One normal and one eco. Mrt seem to use the normal setting even with lrr tyres which also impacts mpg.

So for my 10p worth, there is no one big thing but a combination of small things.

 

[Chris Dance]

When the engine is stopped on a Gen 4 Prius the computer gives tips on how you drove on the last journey. A strange tip came up yesterday which I do not understand. It stated " GOOD STEADY DRIVING, REDUCE TEMPERATURE TO IMPROVE".  How do you reduce temperature?  The fuel consumption is high 70s. but on a trip to Lowestoft last week end computer showed 84 MPG.

[danowat]

Outside temperature?

[ian rooke]

Hi it's saying raise the temperature of the air con to improve the fuel consumption 

[PeteB]

1 hour ago, Chris Dance said:

... REDUCE TEMPERATURE TO IMPROVE".  ...

I've seen this many times in the winter when I've asked to be kept quite warm.

There's probably a limited number of messages in a list, and I suspect this one is also used when it really means "don't ask for it to be quite so cold when it's hot outside".