Aerodynamic modifications to a 2007 Camry SE

[Taylor95]

I made front wheel spats for my 2007 Camry SE out of some mud guards I had laying around. I cut the midguards in half and I attached them using some included fasteners as well as bolts that hold the front undertray in.

The spats made a hole going into the wheel well. I am not sure if closing it off would be beneficial. I will test that when I do AB testing for the wheel spats.

I will be making rear wheel spats with the rest of the material I have.

[COcyclist]

Interesting. How will you know if they are helping mpg? I see you plan to test. What methods will you use?

[Taylor95]

On Monday I will do a coast down test at 45 mph. It will actually likely be a BAB test rather than ABA.

[JulianEdgar]

Unfortunately, coastdown tests are, in my experience, completely unreliable.

To test the technique, do multiple windows up / windows down coastdowns and ensure that the averaged results show a major increase in drag with the windows down.

[Taylor95]

There was some snow earlier this week so I was not able to do any testing. I will have to do that later.

I just finished adding the rear wheel spats. It was strange to see that there was a factory spat on the driver side but nothing on the other side! The factory wheel spat did not look very functional-about half of it went past the inside edge of the tire.

I let part of the spat go outside the wheel well. Let me know what you think about that. I think that it would create an air curtain effect. If not, I can always cut that off. Unfortunately I cannot do any ABA testing on these. They aren't very easy to remove.

[COcyclist]

Originally Posted by Taylor95

I let part of the spat go outside the wheel well. Let me know what you think about that. I think that it would create an air curtain effect.

It’s complicated. I have added spats in front of my rear tires but they do not extend out beyond the body of the car. My coasting distances and tank averages are better than before I started my mods but it is very difficult to tell if the spats are helping or hurting my mpg by themselves. (I have a full under tray that may be helping the most).

It is my understanding that we want the air to stay attached down the sides of the car and detach cleanly at the back end. From the photo, it looks to me like you have added a “Gurney Flap” which is like a small spoiler that may kick the air out around the spinning wheel. I cannot say if this will help reduce aero drag without testing. It may be a good attachment point for a future fender skirt to help clear the lower edge of the tire. I hear you about the spats being difficult to remove for testing. Sometimes a compact ratcheting right angle screwdriver works. I found one cheap at a discount tool chain. You could try some tuft tests to see how turbulent the airflow is. I have seen where Julian will add a tuft taped to the very center of the wheel to see how the air flows across the wheel face.

If there is a high mpg or all electric version of your model of car it is usually safe to copy what the factory has done. FWIW some of the factory spats I have seen are about the size of a playing card, usually much smaller than the size of the front of the tire.

The “air curtains” we discuss here generally have a duct to speed the airflow across something like the front wheels so the flow is more attached down the sides after the wheel opening. Good luck. I hope his helps.

[MeteorGray]

I "assume" gurney flaps in front of the tires help.

My 2015 Mazda3 has them in front of all four tires. I doubt Mazda put them there unless they help fuel economy enough to justify the cost.

I doubt I could discern any mileage degradation if I removed them from my car because of my inadequate ability to test, but I'd bet dollars-to-donuts that Mazda saw an improvement when they designed the car.

[Taylor95]

Originally Posted by COcyclist

It’s complicated. I have added spats in front of my rear tires but they do not extend out beyond the body of the car. My coasting distances and tank averages are better than before I started my mods but it is very difficult to tell if the spats are helping or hurting my mpg by themselves. (I have a full under tray that may be helping the most).

It is my understanding that we want the air to stay attached down the sides of the car and detach cleanly at the back end. From the photo, it looks to me like you have added a “Gurney Flap” which is like a small spoiler that may kick the air out around the spinning wheel. I cannot say if this will help reduce aero drag without testing. It may be a good attachment point for a future fender skirt to help clear the lower edge of the tire. I hear you about the spats being difficult to remove for testing. Sometimes a compact ratcheting right angle screwdriver works. I found one cheap at a discount tool chain. You could try some tuft tests to see how turbulent the airflow is. I have seen where Julian will add a tuft taped to the very center of the wheel to see how the air flows across the wheel face.

If there is a high mpg or all electric version of your model of car it is usually safe to copy what the factory has done. FWIW some of the factory spats I have seen are about the size of a playing card, usually much smaller than the size of the front of the tire.

The “air curtains” we discuss here generally have a duct to speed the airflow across something like the front wheels so the flow is more attached down the sides after the wheel opening. Good luck. I hope his helps.

The front ones I can definitely test. I still want to do that. I think coastdown testing would be the best method, but I do have a scangauge I could use too. The rear ones would require removing the tire no matter what... there is probably 1 cm in between the tire and the screws. Not to mention I also would need to remove some body paneling to put them back on.

That is good to know that dome cars come with gurney flaps from the factory. Mine hardly stick out at all so I would think that they are beneficial. It would just be a lot of effort to test...

It is worth mentioning that I did see a slight mpg increase my last fillup, which is the first one with my mods. It has been a lot colder lately, so I think I can attribute some of the difference to my mods. I will definitely get around to testing the front ones though, and postung what I find.

[Taylor95]

Originally Posted by MeteorGray

I "assume" gurney flaps in front of the tires help.

My 2015 Mazda3 has them in front of all four tires. I doubt Mazda put them there unless they help fuel economy enough to justify the cost.

I doubt I could discern any mileage degradation if I removed them from my car because of my inadequate ability to test, but I'd bet dollars-to-donuts that Mazda saw an improvement when they designed the car.

Could you post a picture of them? About how far do they stick out from the body?

[MeteorGray]

I'm too dumb to do pictures, but I can say they are not very large at all and certainly do not stick out from the side of the car. I doubt very much you would notice them if you weren't looking specifically for them. In fact, the first time I noticed my car had them was when I read some forum guy was looking for a replacement, since one of his had fallen off his Mazda3. They're only about the width of the tire, and they appear to be positioned to displace that tiny bit of air before it hits the tread.

If Mazda hadn't put them on, I'd say it would be silly to bother installing them. But as I said, I'm certain Mazda recorded some measured improvement with them.