[Guesty]

Just stumbled accros this. Amazed that the model s is lower drag than the leaf. I new it had a lower coefficient but thought it was offset by its size.

Wonder what an I3 is? Do the skinny tyres help with aerodynamic drag?

http://www.businessinsider.com/tesla-model-s-wins-wind-tunnel-wars-2014-5

"The numbers get even more interesting: Did you know, for example, that a Model S requires just 14 horsepower to maintain 70 mph, 4 hp less than a Leaf?

That rises sharply by the time you reach 100 mph—exponential increases in wind resistance means the Tesla uses 42 horses to stick at 100—though that's still 11 hp less than the Leaf would need."

Edit: 4hp = 3kw so pretty significant
PDF here http://www.teslamotors.com/sites/default/files/blog_attachments/the-slipperiest-car-on-the-road.pdf

 

[Paul]

That's really interesting stuff... Seems like Nissan are currently missing another trick here then!

Love my LEAF, but "must try harder" is my general view.

 

[Edd Beesley]

Yes I went into a lot of detail on this in a Leaftalk thread a while back, weighing up whether aero improvements or weight reduction were better for range. The conclusion (for me anyway) was that getting the Leaf even down to Prius aero levels would have a significant range improvement, far more than removing a few hundred kilos of mass (the comparison being all about the i3's CFRP lightweighting). Getting it to EV1 levels would give you a Leaf capable of 100 miles at 70mph using the existing battery.

 

[Brian Stanier]

BMW and Nissan both regard their cars (i3 and Leaf) as city cars rarely likely to exceed 30-40mph and pushed drag to bottom of the optimisation list. That they are wrong may or may not have filtered through to the design process.

 

[Guesty]

I think your probably right but what would have been the items higher up the list? Visibility? Rear headroom due to batteries under the seat? Can't think of anything more important that range other than maybe 5 doors and 5 seats.

I understand that the motor is also more efficient around town than out of town but since i can get well over 120 miles per charge around town. It would have been nice to have a little bit more efficiency at the high end.

It's a great car but looking forward to what they can bring to the table next.

 

[Edd Beesley]

Yes, a longer tail on the Leaf would have given us better Cd, and more boot space. Might have limited rear visibiity (though we have a rear camera...) and encouraged people to put more stuff in the boot (we don't have much ability to carry stuff, officially). But a Leaf Estate, with a second battery under the boot floor sounds pretty awesome to me!

 

[Brian Stanier]

For the i3 especially compactness which means blunt ends to retain interior passenger space in a short length. And if its to be a city car range is not that important.

 

[Paul]

Yes I went into a lot of detail on this in a Leaftalk thread a while back, weighing up whether aero improvements or weight reduction were better for range. The conclusion (for me anyway) was that getting the Leaf even down to Prius aero levels would have a significant range improvement, far more than removing a few hundred kilos of mass (the comparison being all about the i3's CFRP lightweighting). Getting it to EV1 levels would give you a Leaf capable of 100 miles at 70mph using the existing battery.

Is unsprung weight as significant here as I imagine? I have no idea how regen and all that other stuff works (should learn), but anything to get that down can only be a helpful addition (as opposed to carbon fibre number plate strips or whatever).

 

[Edd Beesley]

For efficiency in stop start city driving, weight is king. You can also capture lots of regen, since the amounts of energy involved are less. Really once you start getting over 40mph you are using more energy to push the air out of the way than to over come your rolling resistance. By the time you're at 80mph in a typical car the rolling resistance is in the 10% or less region of power being used. So reducing your mass by 90% will only reduce the amount of power needed by 9%...! Going for a more moderate 20% loss by doing something like using aluminium instead of steel of course only sees a 2% loss in power requirement. Now that can make a sensible difference in the city stop start, but is almost meaningless at 80mph.

 

[Paul]

...but is almost meaningless at 80mph.

If only we could go that fast on UK roads.

 

[Edd Beesley]

If only we could go that fast on UK roads.

Indeed! The comment is more for our German friends, I mean speakev is for all nations, surely?

 

[Ian]

And I am still happy with my PiP.

 

[nattydread]

As the article says the LEAF has the largest cross sectional area which is why it performs poorly.

 

[Paul]

Updated with nice video version:

And Car and Driver article in full:

http://www.caranddriver.com/features/drag-queens-aerodynamics-compared-comparison-test