Aerodynamic tests and modifications on the MR-2 Spyder

[Autobahnschleicher]

As I plan on improving the aerodynamics of my car I'm making a thread with my tests and modifications.
Maybe someone will find this interesting or usefull, maybe someone will have suggestions.

In my first test, I have use wool, tape and an action cam to visualize the flow on and around the rear window.
As you can see seperation is occuring in the center, but flow is staying attached to large portions of the rear window.
Therefore I'm going to mount vortex genertors near the center above the window to get flow attachment in the center section.

[aerohead]

Is the car a BMW X4?

[Autobahnschleicher]

Originally Posted by aerohead

Is the car a BMW X4?

As I said in the title it's a Toyota MR2 Spyder, a small japanese convertible.
However the distortion of the fisheye lens does indeed make it look rather weird...

[aerohead]

Sorry! You clearly described the car in the header to the thread.
The rear window is extremely steep! I can see why you are thinking about vortex generators.
Does your car have the rear spoiler?

[Autobahnschleicher]

My car does not have a rear spoiler or wing, but I plan on mounting a small lip spoiler on top of the rear bumper to get a cleaner flow seperation.

[aerohead]

I found your car here at EcoModder.com's drag list at the top of the forum.
It shows Cd 0.31, however, I don't know if that required the rear spoiler.
The 1st-gen MR2 spoiler was good for a 10-count drag reduction.
The blueprint for your car shows attention to roof sides camber into the C-pillars. They may already be optimized as they are.
Turbulence and vorticity can rob energy, so VGs, reducing the actual volume of disturbed flow might mitigate some of that to the good, even after accounting for the permanent drag due to the VGs themselves. It's hard to tell without a laboratory environment.

[Autobahnschleicher]

Are you sure you have looked at the right car?
My car has no C-pillars, it's a convertible wich only kind of has B pillars and no spoiler.
Could you maybe have confused it with the MR2 MK-2?

Anyway, getting the flow to stick would siglificantly reduce the size of the low pressure area behind the car, wasting less energy in the wake.
Alternatively I would need to fabricate a kammback-extension over the engine bay to reduce the angle.

[aerohead]

Originally Posted by Autobahnschleicher

Are you sure you have looked at the right car?
My car has no C-pillars, it's a convertible wich only kind of has B pillars and no spoiler.
Could you maybe have confused it with the MR2 MK-2?

Anyway, getting the flow to stick would siglificantly reduce the size of the low pressure area behind the car, wasting less energy in the wake.
Alternatively I would need to fabricate a kammback-extension over the engine bay to reduce the angle.

Please forgive the steady stupidity.
Your removeable hardtop obviously has no C-Pillars at all, and only the appearance of B-Pillars, since there's no actual structure under the roof.
So, correcting for my blindness, Toyota seems to have paid attention to the faux- B-Pillar area, allowing the air to flow around the sides of the roof and vector inwards, at least limiting the wake behind the roof at those locations. A good thing.
If the flow reattaches onto the boot, you'll have a separation bubble which travels with the car, and it's low pressure will be isolated from the actual wake behind the car.
A Kamm- back would sure help with pressure recovery and higher base pressure, cutting drag. As long as it didn't interfere with mid-engine operation (I'm unsure what the 'grille' openings are for on the rear decklid ).

[Autobahnschleicher]

Yea, the airflow does indeed come around from the sides and helps it staying attached, wich is some good engineering from Toyota.
However a section in the middle has a tubulence, in my video I saw the strings there pointing to the front of the vehicle.
If I can get the flow to attach there, I can reduce the size of the wake significantly with little modifications the TÜV can overlook.
But I'll see if it works, ordered the vortex generators allready so might as well give it a try.

[Cd]

Looking forward to your testing !
Since it has a removable hardtop, you have the opportunity to create a nice top that you can replace when you want.
Since the car is rear engine, I would guess that some ventilation would be needed in the design.
With the airflow being pulled onto the back of the car, this might even help the airflow stay attached, and that is a real plus in your efforts.

Did I miss the year if your car ? I didn't see it.
Looking at the photo though, I'm guessing this may be the design of your car.


You may find this hardtop Miata interesting.
You could do something similar. ( And it actually would look cool too ! )
Click the video link :
https://youtu.be/ymvI_h1VwgI