air dam it

[scottm]

Anybody been thinking of the possibility of lowering Cd coefficient of drag for this slippery car even further by adding an air dam? My goal would be increased fuel efficiency / more range. Even if the gain is a couple % it would make me happy knowing that I can go 8 extra km on a tank of ejuice. (Hey, it could be the difference between getting to a SC or not someday I've miscalculated or run into unfortunate circumstances!)

Some experiments suggest low setting on air suspension (I have it) can produce better returns on hiway trips. So can we do better by lowering that air gap under the nose even more? Getting lowering links and slamming the battery lower to the road starts to raise the risks of puncture. But if it's just an air dam that takes a blow, and can be replaced, I'm OK with that.

I've been toying with the idea of attaching something under the front nose.

I'd like to collect opinions, thoughts, advice from those who may have any experience or experimented with this... maybe on a Tesla, or any other hiway car.

 

[scottm]

What's better?

1. Does silhouette profile make a dam bit of difference... should it be flat like a wall, dished forward on its lower lip ("underbite"), or ranking backward from the top (an "overbite"). Which is better for evacuating / pushing the air out of the way to lower Cd?

2. Top view down onto the car... should the dam be near the leading-most edge of the car's existing little air splitter and follow the curvature of the nose as it wraps around the car, what if it's tucked more under the car and trailing a bit behind the leading edge, what if the dam is a "flat board" located just ahead of the front tires that runs the width of the car... when does it start to matter and what's the difference to get lower Cd?

3. How low can you go? I was actually thinking of making it so that when the car is on lowest air setting, the dam would be maybe an inch off the ground. Crazy right? To support this crazy idea.. it has to take a hit of debris and survive.. gotta be some flex. Choosing a material and mount technique that absorbs a hit (flexes, hinges up, snaps back... ) would be paramount. And it can wear down on the lower edge as it inevitably road rashes itself. I'm looking for maybe a real cheap and replaceable material that "snaps / slides into place" as a disposable thing. How about a firm closed cell semi-rigid polyurethane or polypropylene type foam. Strong enough to push the wind out of the way without deforming too much.. (I wouldn't drive or expect it to remain good driving over say 140kph... could start to deform badly after that.)

..

initial thoughts

 

[Chris_WDO]

Hi scottm,

I have designed and constructed carbon fibre wheel covers that increase the range of an existing Model S by additional 6%.

They are way better than the original Tesla aero wheels used to be, because the aerodynamic quality is significantly better. Additionaly, you don't have to have a separate set of rims and tires to use them, they can be attached and removed without the need of a car lift.

Coefficient of drag is reduced from cd = 0,240 to merely cd' = 0,222

See this article (in German atm, but I can translate it to english if wished):
Aerodynamik Tuning des Model S - mehr Reichweite • TFF Forum - Tesla Fahrer & Freunde

 

[ColBatGuano]

Hi scottm,

I have designed and constructed carbon fibre wheel covers that increase the range of an existing Model S by additional 6%.

They are way better than the original Tesla aero wheels used to be, because the aerodynamic quality is significantly better. Additionaly, you don't have to have a separate set of rims and tires to use them, they can be attached and removed without the need of a car lift.

Coefficient of drag is reduced from cd = 0,240 to merely cd' = 0,222

See this article (in German atm, but I can translate it to english if wished):
Aerodynamik Tuning des Model S - mehr Reichweite • TFF Forum - Tesla Fahrer & Freunde

I would be interested in reading this article in English.

 

[Chris_WDO]

The Topic says:
Aerodynamic improvement of Model S - 6% more Range.

In a nutshell, I've been testing the prototype of those carbon fibre wheel covers for roughly 15.000 miles by now, from low speeds to 155mph on the German Autobahn, from north sea to the mediteranean, and I've even been up on the famous mountain Großglockner (3000m =[10.000 feet above sea level] high mountan in Austria). Issues with the CFK covers = none.
Meaning no vibration, no noise, even a bit quieter aero-noise cause of less turbulence in the airflow passing the car.
The amount of aerodynamic improvement is singificantly better than the original Tesla aero wheels, which provided about 3% mor range but are no longer available.

What you get with those cfk covers is roughly 6% more range on any existing Model S with 19" standard rims, by reducing the cd from 0.240 to cd 0.222.

The only thing you can't do is going on a racetrack, and you have to use the regen on standard (always keep regen set on standard, never low) when going downhill from a mountain. And of course, NEVER charge to 100% when you are up high in the mountains, cause you'll have to have free capacity in your battery when going down several thousand feet of elevation without using the mechanical brakes too much. It is appropriate not to charge beyond 70% being on 10.000 feet above sea level with a 85kWh battery.

Of course, after driving thousands of miles with the covers fitted, you accumulate a lot of brake dust under them, so the rims need a thorough cleaning to look nice again after taking them off.

They are not meant to be taken on and off on a daily basis, cause you need about 40 minutes to fit them properly, and about 15minutes to remove them all. But on the other hand, who would want to do this?

 

[scottm]

Chris - Erstaunliches Stück Arbeit und Forschung mit dem Rad umfasst , und die Ergebnisse sind beeindruckend!

The CF look is OK for some cars, and would suit my Grey metalic -- I have done the nose cone in CF wrap so there is some consistency of decor there. Stylistically tho, I would at least smack a red Tesla T logo on the center of those covers... stickers are cheap and can be found many places now. ...then people will probably see them as somewhat "experimental" but somehow sanctioned by Tesla maybe as a road test they are doing.

6% is a big chunk. It would be so cool if these covers plus a few more aero efficiencies combined could return 10% range. That would be like getting back battery range lost through battery degradation over a few years. A "boost" back to original range. And for new cars, new "free" range.

One of my goals for an air dam would be stylistically integrated with the looks of the car... or perhaps just almost completely hidden underneath so it doesn't matter so much what they look like. Just funktion that matters.

 

[scottm]

just saw this

Sr. Engineer-Aerodynamics | Tesla Motors | Tesla Canada

Oh! Oh! Pick me! Pick me!

 

[No2DinosaurFuel]

What is the cost? Also will it work for the new slipstream rims?

If this works like it claims, then I can around 300 miles on my S90D if I charge to 100%

 

[scottm]

(Maybe contact the poster of those hubcaps directly? ...)

This thread is about air dam creation and maybe your 90D will go another 10 miles yet, if we can get something going here.

 

[Chris_WDO]

Yes, they also work with the new slipstream wheels.

They are handmade in Germany, therefore not cheap to manufacture, and you need mounting parts which are hard to get and not cheap either.

Still, the cost is less than a 5kWh Battery upgrade and less than the premium you pay for 21"wheels (which reduce range and increase tire cost), right now 1999,- EUR plus tax.

Oh yes, and you gotta have a good quality torque wrench, cause the torque needed to fit them is as low as 8 Newtonmeters.