2013 Empulse R vs 2013 Zero S "shoot-out"

[Adan]

I doubt people are choosing between the Zero and the Empulse based on which one wins a race either off the line or from 50-80 mph.   I test rode the Zero S and gotta say, the acceleration from 50-80 is pretty exhilirating.  When it comes to that particular aspect of riding, neither bike will leave riders wishing they were on ICE.

[frodus]

Here's something I found interesting..... I was Looking at the Zero DS ZF11.4....

126mi city
82mi combined
61mi highway @70mph


The gearing, controller and motor are all the same. The only real differences I see are the DS tires and different suspension. The DS is 8lbs heavier.

So the kWh/mi for the Zero DS ZF11.4 is:
10kWh/126mi = 79.4Wh/mi city
10kWh/82mi = 122Wh/mi combined
10kWh/61mi = 164Wh/mi combined

And the kWh/mi for the Zero S ZF11.4 is:
10kWh/137mi = 73Wh/mi city
10kWh/93mi = 107.5Wh/mi combined
10kWh/70mi = 142.9Wh/mi combined

And we have the Brammo Empulse R/E1:
9.3kWh/121mi = 77Wh/mi city
9.3kWh/77mi = 120.8Wh/mi combined
9.3kWh/56mi = 166Wh/mi combined

For City, Zero S to DS jumps from 73Wh/mi to 79.4Wh/mi on city, and from 142.9Wh/mi up to 164Wh/mi for highway at 70mph.

That's a bit surprising. Do dual sport tires really cause that much drag that would put the DS into the same range category as the Empulse?

Something smells a little fishy.... That's an ~9% increase in Wh/mi useage in city, and a whopping 15% increase on the highway.

[flar]

In 2012 I think the DS had a different final drive, but the specs are the same for 2013.  The DS tires are higher profile on narrower rims.  I know how to calculate circumference for a car tire, but not sure how the rounded nature of a motorcycle tire might change that formula (not to mention the change in rim width).  Could the tires have different circumference and thus implicitly modify the effective final drive ratio?  They have the same top speed so I would guess not...?

[frodus]

Zero DS: 132T / 28T, Poly Chain® GT® Carbon™ belt
Zero S: 132T / 28T, Poly Chain® GT® Carbon™ belt

Same final drive.

Tire Diameters for the rear:
DS: 130/80-17 (25.189" diameter)
S: 130/70-17 (24.165" diameter)

So there's a ~1" larger diameter on the rear... that shouldn't change things that significantly.... that would really only effect acceleration .... but 9% and 15% for city/highway? That's a huge change for a different aspect ratio and some Dual Sport tires.

[flar]

Frodus, you're assuming that the tire sidewall extends vertically from the wheel rim as in a car (well, 99% of cars), but it does not.  As I said, I could apply the standard formula which works reasonably well for a car, but these are bikes with a rounded profile and sidewalls that extend at an angle from different sized rims.  I don't think the standard tire math even gives you a "rule of thumb" estimate of their actual diameters.

[Richard230]

I think the greater wind resistance of the DS, compared with the S, might account for much of the difference.  The DS has a seat height that is 3" taller than the S seat.  The greater frontal profile of the DS could make the difference at high speeds - along with the increased rolling friction of the aggressive dual sport tires mounted to the DS.

[frodus]

Frodus, you're assuming that the tire sidewall extends vertically from the wheel rim as in a car (well, 99% of cars), but it does not.  As I said, I could apply the standard formula which works reasonably well for a car, but these are bikes with a rounded profile and sidewalls that extend at an angle from different sized rims.  I don't think the standard tire math even gives you a "rule of thumb" estimate of their actual diameters.

You assume I'm assuming

I calculated those diameters based on the aspect ratio.  The aspect ratio takes into account the ratio of width and height. Those are true diameters that I have verified using several online motorcycle tire diamter calculators. I've also verified this with my old VFR tires.

[frodus]

I think the greater wind resistance of the DS, compared with the S, might account for much of the difference.  The DS has a seat height that is 3" taller than the S seat.  The greater frontal profile of the DS could make the difference at high speeds - along with the increased rolling friction of the aggressive dual sport tires mounted to the DS.

Good point Richard!!! Forgot about that.

That 3" height is almost all tires/wheels/suspension... the bulk of the bike stays the same. With that 3" height and lets say a 130mm width of the rear tire (~15") is roughly 45in^2 more frontal area. Lets kick that up to 60in^2 for good measure because if you do increase front height, you may increase the body cross sectional area a bit... but not by much.

Lets say the Zero itself is 500in^2 of frontal area... it should be close. I threw the values in my old elmoto calculation sheet with a 500 and 560 in^2 cross sectional areas, 0.8 Cd at a 70mph cruise. The drag Coefficient on these is going to be fairly bad since they're unfaired.

96.71Wh/mi for 500in^2 and
106.5Wh/mi for 560in^2

So a ~10Wh/mi change.... and it's right around 10wh/mi for other cross sectional areas I tried... like 400/460, 300/360

Looking at the Zero DS and S (166Wh/mi and 142.9Wh/mi respectively).... frontal area would account for 10wh/mi .... the actual difference is ~23wh/mi... so that other 13Wh/mi is coming from somewhere.

So yes it does effect the wattage useage some. I'd guess that less than 1/2 of that increase is due to increased frontal area.

It's amazing what you can do with just changing the rolling resistance of the tires and your cross sectional area..... tucking sounds better doesn't it

[Richard230]

Luke (liveforphysics) who seems to be in the know about Zero motorcycles had this to say about the differences in performance between the DS and the S on the elmoto forum:

You're aware one bike uses a Sevcon Gen4 size6 and one uses a Sevcon Gen 4 size4 right?

So how would a size 6 and a size 4 affect the range of similar motorcycles and why?  I can see how a larger controller would increase top speed and acceleration, but maximum range? 

[frodus]

I think he means that the Brammo uses a Sevcon Gen4 Size 6 and the Zero S and DS both use a Sevcon Gen4 Size 4. He commented on an earlier post than mine, not my S versus DS posts.

According to Zero's site, and from what I've been told, both have a "High efficiency, 420 amp, 3-phase brushless controller with re-generative deceleration"... meaning both of the Zero S/DS bikes use the Sevcon Gen4 Size 4.

And it could effect the acceleration if you threw a Gen4 Size 6 in a Zero. It would be allowed to draw more current from the batteries during heavy acceleration, which could potentially limit the max range. If you floor the throttle in an ICE, you use more gas, and get worse gas mileage.... same thing here.

[Richard230]

Makes sense.