How accurately does Zwift simulate motor performance and battery consumption

[BikeMike]

I am trying to answer the specific questions in this post:

Optimizing Specialized Creo Expert SL with 1.1 motor for 60 miles at 25mph

Hi, I sent the following email to Specialized Care today. Perhaps, your answer will prove more informative? I own a 2015 Specialized Diverge (mechanical bike). I live in Denver. I am a strong rider. I generally ride about 5,000 miles per year. I weigh 225 pounds. I have generated over 800...

electricbikereview.com

I would like to optimize battery and motor performance by finding the optimal drivetrain for a 60 mile ride at 25 mph. My bikeshop has a 30-day return policy. I am considering using a trainer to measure the bike. I have a feeling my goals are beyond the Creo Expert capabilities.

Here is the post for your convenience:

The main reason for considering a Creo Expert is to ride 70 miles from
Denver to Fort Collins as fast as possible.

I have a mechanical mountain bike with a single chainring. I start to spin out of
gears on my mountain bike at higher speeds. I do not like the single chain
ring efficiency at speeds over 25mph.

I always use the big chainring on my Specialized Diverge for 25mph speeds. I would like
the Creo Expert chain to be as straight as possible at 25mph. I expect to
ride for miles, on country roads, in the same gear at 25mph. My typical
cadence is 95 RPM.

1. Which chainring/cassette combination is optimal for 25mph battery
consumption?

2. How much aerodynamic overhead does the Creo frame incur over the
Diverge?
- The bottom bracket is wider. I suppose the downtube is wider to
accommodate the battery?

3. How much power is consumed by the eBike to overcome it's weight,
aerodynamics, motor resistance, etc...?
- I suppose the Eco setting (30%) is needed to offset the overhead?

4. If I rode the bike with and without electric power, how would I
calculate the minimum motor power and battery capacity I would need to ride
70 miles at 25mph?

5. Is the Di2 shifter synchronized with the motor to suspend power when
shifting gears?

I understand 170 watts are generally required to reach 20mph speeds. 300
watts are generally required to reach 25mph speeds. The SL 1.1 is rated at
240 watts. The maximum sustained speed of the motor should be between 20 to
25mph. 28mph only makes sense to me, when I supply the underlying speed.

1. What speed do I need to pedal the Creo Expert at without power, for
the bike to achieve 28mph with power?

Attached please see the ride I am most concerned about optimizing battery power at 25mph. The section from Westminster to Boyd Lake State Park.

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[HLM]

Put the Creo on an accurate trainer and you'll get your questions answered.

 

[Stefan Mikes]

For me, 60 miles at 25 mph for a Creo means the rider is putting 90% of the input himself.

 

[nublar]

It depends on rolling resistance, work, and wind resistance. You can generally calculate the first two from your weight, tyre choice, elevation gain, etc but the third one depends on actual real world conditions and your bike position and can be highly variable, especially at 25 mph. In my experience I got 10-15 watt-hr per mile going ~20 mph with level 3 (out of 4) assistance while on the drops.