A Tesla Model 3 with 440 miles of range?
Nov 20, 2018
How some modest aerodynamic improvements to the Tesla Model 3 could dramatically improve its range at highway speeds. Enough in fact to give a Tesla Model 3 with a 310 mile stated range 440 miles of range at 75 mph. Range improvements like this would also apply to the Mid-Range and Short Range versions of the Tesla Model 3.
By John A Gilkison and Phillip R Knox
Sometimes you begin a blog project with one goal in mind and another result that is unexpected drops out of it as you research the project. In this instance we started out with the premise of what aerodynamic modifications would be necessary to give a Tesla Model 3 the capability of 100 mpg-e while doing 100 mph. Given that the Tesla already has a low Cd = 0.23 and is an energy efficient platform capable of over 80 mpg-e at 100 mph we thought add on aero mods might do the trick.
With this idea in mind I consulted Phillip R Knox our aerodynamics expert in Sanger, TX about the possibilities. I sent Phil a data sheet on the Model 3 and a report on the watt hour per mile consumption at 65 mph, 70 mph, and 75 mph published on You Tube video by a California V-blogger.
Phil generated a graph which peaked at 100 mph and 327 watt hours per mile as its end point. Many other numbers fell out of the graph at lower speeds that we could use in reporting on the project. The Cd number that fell out was Cd = 0.179 which we will call Cd = 0.18 for the purpose of this article.
Our idea would be to take a Model 3 RWD (because it is more efficient) and add a boat tail to the rear of the car to lower the coefficient of drag. Other modifications such as rear wheel opening skirts, and possibly removing the passenger side mirror and substituting a camera (this is legal) to lower the drag there also. The boat tail under consideration is either three feet or four feet long since we do not know without doing the project in real life what the results would be.
To be clear before anyone complains about how such a vehicle would not be commercially viable because of the odd looking shape the GM EV-1 had a Cd = 0.19 which is very close to this number. In point of fact some aerodynamic engineers added a little extra length to the EV-1 boat tail and set a 183 mph speed record for the car at Fort Stockton, Texas. This is our proof of concept here, which is that these ideas have already been proven to work in the real world.
There are two ways of adding a boat tail to a car like this for a do it yourselfer. They are 1: To have a light duty hitch installed so you can mount a platform behind the car to build on and 2: Use a bicycle rack to build a platform around. The second choice is probably cheaper. The goal would be to keep all the mods weighing less than 60 pounds.
After receiving Phil’s graph I crunched some numbers and put together a You Tube video titled “Tesla Model 3 Aero enables 100 mpg-e at 100 mph” uploaded on November 14th, 2018.
On the 16th of November, 2018 after fleshing out the watt hours per mile consumption at various speeds and the resulting range for the vehicle at those speeds I published another You Tube video titled “Tesla Model 3 with 440 miles of Range?”
It was only after publishing my second video that it begins to occur to me that these aerodynamic modifications dramatically extended the range of the Model 3 in all of its iterations, extending the range of the Long Range version to 440 miles (stock 310 miles) at 75 mph. Even the short range version (not for sale yet) would have its 220 mile range extended to 309 miles at 75 mph. The mid-range Model 3 benefits also with a range extension from 260 miles stock to 368 miles at 75 mph.
In case you are wondering the MPG-e ratings for all three variants of Tesla Model 3 cars are the same at the speed regimes we are discussing here (65 mph, 70 mph, and 75 mph). They are respectively 252 mpg-e at 65 mph, 218 mpg-e at 70 mph, and 192 mpg-e at 75 mph. The MPG-e rating only drops down to normal Cd = 0.23 ranges at speeds beyond 87 mph. This is how this drag reduction paradigm works, every performance parameter is moved 20 mph to the right on the graph.
The motor (or engine) of any car only knows about aerodynamics, rolling resistance, and drivetrain losses when it comes to the power that is needed to maintain any given speed on the highway. These are the counter forces it is encountering (given an ideal day) no appreciable winds, rain, snow, or other conditions which would have a bearing on how these forces manifest themselves.
This is a major coup I had not really thought about in any detail when we started the project. I had been thinking about how 60 lbs. (the weight of the appliances) of extra batteries would only extend the range of any given car only about 18 miles so potentially our appliance was the greater bang for the buck. I had not envisioned just how much.
The boat tail would be easily removable for local driving and would only need to be installed for traveling. With a 136 mpg-e City EPA rating the appliance would not be needed as they would have little effect on low speed driving where aerodynamic forces are not predominant.
Obviously being able to get 100 mpg-e at 100 mph is a nice round number metric and a good attention getter, but the ramifications of extending the range of any Tesla Model 3 by 30% had not really registered for me at first. With a Long Range Model 3 having 440 miles of range, range issues would just not be a real problem. The majority of travelers could reach their stay for the night (or their destination) and simply just charge overnight.
Imagine you buy a Short Range Model 3 (when they become available) which only has a 220 mile range on the highway. Adding the aero appliances increases its range to 309 miles at 75 mph. Slow down to 70 mph and the range leaps up to 358 miles. The range increases for the Long Range Model 3 come out to 440 miles and 500 miles respectively. Both scenarios are a smoking bargain, and the Mid-Range version isn’t too shabby either with a 417 mile range at 70 mph, and 482 miles at 65 mph respectively.
The original impetus for this blog was a You Tube video done by Bjorn Nyland (from Norway) about high speed travel with a Tesla Model S P-100D on the German Autobahn.
Bjorn posted his watt hour returns for various speeds clustered around 160 kph and when looking at his tables it occurred to me he was doing over 70 mpg at 100 mph.
Then I looked into the Tesla Model 3 because I thought since it had less frontal area and less mass so it should do better. With only 23.68 square feet of frontal area, sure enough the Model 3 could do over 80 mpg-e (down from 123 mpg-e at normal highway speeds) at 100 mph. This project looked very doable given these numbers.
In our blog post here at EV World published in 2016 titled “100 mpg-e and 100 mph” we considered the Chevy Bolt as a platform. The Tesla Model 3 wasn’t in production yet at that time. Since the Bolt has a Cd = 0.31 we considered a complete replacement of the body for a Cd = 0.12 body form. Obviously this is outside the capabilities of almost everybody on the planet and GM is highly unlikely to ever do such a thing themselves.
The Tesla Model 3 already having a low drag body form and a highly efficient drive train lends itself well to such a boat tail project. No modifications to the original body need to be made as the appliances we are considering are simply add on devices. This puts this project inside the wheel house of thousands of motivated amateur aerodynamicist. While this may be a small group, they are out there, go to ecomodder.com and you will see what I mean.
My wife and I are planning to get a Tesla Model3 in the late fall of 2020. We will be done paying for our 2014 Ford XLT Crew Cab 4x4 with a 6.5 foot bed and we can also sell our Ford C-Max Energi so we will be much better position to buy a Tesla financially.
While our C-Max Energi will not be paid off, we want to pass the car on to our daughter since she lives in the city, and this car would electrify almost all of her driving. We could make her a better deal than any dealer, and she can make us a better deal than any dealer would give us.
Up until now I had not been considering variants of the Model 3 other than the Long Range Model 3. This had meant I would most likely be in the market for a used Model 3 given their high price. However, the possibility of building a range extending boat tail that could even make a $35K Short Range Model 3 perform like a Long Range Model 3 has opens up our considerations.
Being able to do 100 mpg-e at 100 mph on the German Autobahn would be just the icing on the cake. The exciting prospect here is the dramatic improvements in the range that can be obtained by lowering the coefficient of drag in the car like the Tesla Model 3 project such as we have outlined here.
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