ElectricMotorcycleForum.com
Makes And Models => Zero Motorcycles Forum | 2012 and older => Topic started by: Tudor on October 17, 2012, 09:14:14 PM
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Hi,
first time poster - long time lurker from Sweden here.
I'm curious about the specifications of the FX and the difference between the two battery configurations.
| Version | Torque | Power |
| 2.8 | 70 ft-lb (95Nm) | | 27hp (20kW) |
| 5.7 | 70 ft-lb (95Nm) | | 44hp (33kW) |
It says both have the same torque, but the 2.8 have almost half the power.
Obviously I'm not an expert on this, but isn't that a contradiction? I would think less power would give less tourque.
How would one experience the difference (acc, wheelies, uphill etc)?
Thank you
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Both bikes have the same initial motor torque (95 Nm). The FX 2.8 may even be a little faster off the line, as it has less weight to move. It also should be able to wheelie better. Uphill is likely to be somewhat easier for the 5.7 kWh bike, especially at speed.
Zero lists the peak power for both motors at 3700 RPM. At this RPM, the 2.8 outputs 20 kW and 52 Nm, the 5.7 outputs 33 kW and 85 Nm. The larger battery is able to supply more power at the top end (20 kW from 2.5 kWh = 8C discharge, 33 kW from 5.0 kWh = 6.6C discharge).
The 5.7 bike's peak power is limited by the motor or the controller - assuming a 33 kW peak, the motor could produce full torque (95 Nm) up to 3300 RPM (33 kW). The 2.8 bike is limited by the battery peak output above a certain RPM - assuming a 20 kW peak, the motor could produce full torque (95 Nm) up to 2000 RPM (20 kW), at which point it starts to fall off.
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I think Zero should publish graphs of the power and torque curves. I think it would be much easier to see with a picture.
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Umm..
Ok,
thank you.
So -from what I understand, if one put it really simple, tourque would give you acc at low speed and power gives you acc at higher speeds.
torque - faster off the line
power - (power to) sustain speed uphills at medium to high speed
On thing still confuses me though,
If Zero specs the 2.8 to have peak power 95Nm at 3700 RPM, why:
The 2.8 bike /../ could produce full torque (95 Nm) up to 2000 RPM (20 kW), at which point it starts to fall off.
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Provided that the wheel and drivetrain do not slip, motor torque output is directly proportional to the forward force on the bike. In the absence of aerodynamic drag, this forward force is proportional to acceleration.
Torque maximum is reached at 0 rpm and held for a time. This is limited by the motor controller maximum current output (250A for the XU, 420A for the FX / MX / S / DS) or by the motor maximum torque.
Maximum power is either limited by the battery's maximum discharge rate (XU / FX / MX 2.8), by the controller maximum power (XU 5.7), or by the motor maximum power (typically heat or RPM related, FX 5.7).
See below a plot of dyno data for a 2010 250R and 2012 S (chassis dyno, assuming zero drivetrain losses) vs nominal idealized data for 2013 XU and FX. Note that the 2012 S is really, really close to the 2013 XU .. but the 2013 XU 5.7 is about 40 pounds lighter than the 2012 S ZF6.
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Thank you for explaining this, protomech. :)
It's beginning to make sense to me now, hehe. The graphs also really highlights the imporovement of 2013 lineup.
The FX 2.8 and 5.7 would then have very similar torque curve but different power curve.
It also makes me curious of what the speed would be at ~3000-3500 RPM (FX-model) would be where the torque is still strong.