Drag HP vs mph

Note that for all those cars, 80 MPH (130 kph) needs twice the HP as 60 MPH (100 kph)

As driver, it may seem just a little bit faster, to your car, it is twice as much work.

 

Please remind me -- are these data with the ICE off, so they are measuring the combination of air, tyre, and transmission losses ?

If so, I'm surprised that the Volt keeps up since it has a relatively high Cd and I didn't remember it as having a much lower frontal area. I'm also then not sure why the range/kWh of the Volt is so much worse than the Prime.

 

Rolling drag power goes up linearly with speed.
Air drag power goes up with speed cubed.

 

The math and the physics jibe very well in this chart.

But, how could a Prius 2 Eco be so much better than
a regular Prius 2 ? A rear window wiper about the only
thing different (?).

 

As humans, we fixate on making the front of the vehicle aerodynamic, but very often the real gains are at the back.

Often the front of airplanes is quite bizarre, but the back is the same as always, to get good aerodynamics.



here is air flow adding a tail to Semis



Do not discount the gains at the back.

 

That's a telling statistic right there!

 

I assume the Ioniq is the hybrid version? Blue?

 

Thanks Bob. This is really enlightening. Do you know if there's one for Gen 3? I did click the ink, but just got raw data. I'll have to try to explore more tomorrow afternoon.

 

I put the CSV file into a spreadsheet ... and then stared into the abyss. I have no idea how Bob turned the data into a graph although I have a vague recollection of reading that the the coefficients model constant, linear and quadratic forces proportional to speed. I could play if the numbers were not imperial units.

 

I hope to have time to mess with that this afternoon. I wanted to yesterday, but was spending some time at the hospital with my son who's facing some really serious stuff. So our lives are going to be very busy for a while. And I'll be driving the best car I ever had a lot more as I make extra trips to their house (1 hour away) or the hospital (1 hour in a different direction). But have less time for light stuff like this.

 

They have the same tires. Toyota recommends higher pressures though. There is a tire tracking thread that proves a various tires across Trim lines.

 

Take care of your higher priorities.
You are in our thoughts and prayers.

 

On second look the Ioniq may be the All Electric version.
First two digits on the cars' identifiers could be the model year, but for the Ioniq there is AE instead.

 

Take time for family, being a car geek can wait.
I wish your son well!

 

This is from another thread on this forum by Jan Treur of Dec 3, 2016. It reinforces the point Bob is making from the calculations of the low drag of the Ioniq: 4.08 vs 3.99 mi/kWh for Ioniq vs Prime

1. Hyundai Ioniq Electric----------------136 MPGe---58 KMPLe----6.53 km/kWh---4.08 mi/kWh---24.5 kWh/100mi
2. Toyota Prius PHV 2017---------------133 MPGe---57 KMPLe----6.39 km/kWh---3.99 mi/kWh---25.0 kWh/100mi
3. BMW i3-------------------------------------124 MPGe---53 KMPLe----5.95 km/kWh---3.72 mi/kWh---26.9 kWh/100mi

Chevrolet Bolt/Opel Ampera-e-------119 MPGe---51 KMPLe----5.71 km/kWh---3.57 mi/kWh---28.0 kWh/100mi
Nissan Leaf----------------------------------112 MPGe---48 KMPLe----5.38 km/kWh---3.36 mi/kWh---29.7 kWh/100mi
Tesla Model S with 85 kWh battery--89 MPGe----38 KMPLe----4.27 km/kWh---2.67 mi/kWh---37.5 kWh/100mi

 

Thanks

I have trouble with imperial units, but this looks like
power = force * velocity

So just taking the quadratic force of

• Target Coef C (lbf/mph**2)
• v - mph
• Drag_HP = (v*(Coef_A+(v*Coef_B)+(v*v*Coef_C)))/375

Would the Drag_HP then simplify to v*v*v*Coef_C / 375 ?
Where does the 375 come from ? I presume it is the unit compression between force and velocity in imperial units, but the number is escaping me. Imperial units are the devil.

A post on Quora says

4.45 N to a Lbf for about 99.95% accuracy. Sound right ?

I went back to look at the CSV and the Coef columns are either empty or have text in them. I'll have to poke around a bit more. Which columns are the data in ?

Lastly, a question about roll-down tests: Am I correct in thinking that the test occurs in neutral ? In a regular ICE car that would capture rotation of the drivetrain and engine, but how does the model account for Toyota hybrids where the ICE does not rotate during a coast ?