My First aerodynamic test with wool tuffs

MvM · 13 June 2011

Today I had planned to do some aerodynamic tests using wool tuffs fixed to the car. Not just to see how the air over the car, but also to see if my NSX-R hood and front underbody cover is actually doing something with the airflow over the front of the car (air coming out of the hood opening).

Unfortunately, the weather was pretty bad and we decided to postpone the real testing to a later date. However, I decided to do a few small tests to test the methodology as well and see if it would work at all.

So, I fixed about 60 12cm (4.8") wool tuffs to the rear hatch and trunk lid and a few left side rear quarter panel and drove a short distance on the highway with my camera fixed to my NSX-R wing.
The weather was pretty dark and rainy, but I could take some shots that give you an idea.
Just uploaded them to YouTube and you can find them here:

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In the second run I briefly took the car up to about 85mph. You can see how the tuffs on the trunk lid are pointed straight ahead but those halfway the rear hatch are twirling in the wind.
But, most important, you see the tuffs near the rear window garnish going INSIDE the opening. This must be because the air is going IN and NOT OUT.

So, basically, the air is going into the egine bay through the rear garnish.

I am planning to redo these test in a more complete manner and then use a few longer tuffs (around 6-8 inches) on the rear hatch to see if it can tell me more about the way the air flows over the car.
Also interesting to see was the fact that the tuffs I fixed to the B-style of the car were going around to rear hatch, pointing to the center of the car.

BATMANs · 13 June 2011

that's really cool.

Got me thinking about doing mines with the spoiler.

have you thought about installing Vortex generators?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=230608737212&viewitem=#vi-content

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docjohn · 13 June 2011

I must concratulate you on your attempts at data collection as best you can.......but I could'nt help think that the title of the vid should be "nsx inseminated"

huck-jai · 13 June 2011

I noticed something interesting. In the first run you can see two three tuffs going into the vent/garnish. The two from the left, you can see them moving. However, the one on the right seems to be very stationary and no movement at all?

Also same thing in the second run. You can see five tuffs going into the garnish. The left two are moving, and other three seem to have no movement at all. They should have some sort of movment at those speeds shouldn't they? Am I seeing things?

huck-jai · 13 June 2011

Might be a dumb question:
Could it be possible that air is coming out from only the centre of the garnish causing the tuffs in the centre of the hatch to twirl?

pgilliam1 · 13 June 2011

huck-jai said:
Might be a dumb question:
Could it be possible that air is coming out from only the centre of the garnish causing the tuffs in the centre of the hatch to twirl?

If you look closely the tufts on the right are stuck under the rear window.

huck-jai · 13 June 2011

pgilliam1 said:
If you look closely the tufts on the right are stuck under the rear window.

Ok, i see it now. Thx.

MvM · 13 June 2011

pgilliam1 said:
If you look closely the tufts on the right are stuck under the rear window.

Just to make a point clear here.
The tufts are not exactly stuck under the rear window. You can pull them out with your fingers real easily.
During driving, the literally get blown into the edge around the rear hatch by the air getting inside the engine bay.

RYU · 13 June 2011

What type of engine cover are you running MvM? Stock? Perforated? None?

ChopsJazz · 14 June 2011

What a cool test. I'm wondering what people were thinking seeing an NSX with what looks like a bunch of sperm cells stuck to your car?

So, it looks to me like the RWG is really doing it's job: drawing air into the back of the engine bay. But what else did we learn?

I'd like to see the same test with a view of the front windshield and top of the roof, not to mention the rear wing (but I mentioned it anyway).

MvM · 14 June 2011

ChopsJazz said:
What a cool test. I'm wondering what people were thinking seeing an NSX with what looks like a bunch of sperm cells stuck to your car?

So, it looks to me like the RWG is really doing it's job: drawing air into the back of the engine bay. But what else did we learn?

I'd like to see the same test with a view of the front windshield and top of the roof, not to mention the rear wing (but I mentioned it anyway).

I am definately planning to do some more of these tests.
Problem was first that last weekend was a bit rainy and also very windy.
Doing this with a wet car and wool would probably not give good results and the water of course would also be bad for the camera.

I want to do this kind of test again with the whole car stickered with wool. I have the VIS NSX-R hood, the Downforce bumper undercover and big battery undercover and Dali Racing air duct behind the radiator.
I want to find out if the airflow through the radiator is indeed coming out of the hood vent. I did notice that the front of my car is really stable now at high speeds.
Same for the way the NSX-R rear wing is working.

rsevo6 · 14 June 2011

Am relatively certain the VIS NSX-R hood doesn't work, just get rid of it, sell it to me

:wink::biggrin:

Bogie Bog · 14 June 2011

Good experiment...You might want to use a longer tuffs similar to the Lancer picture. Stick it middle of the back window and about 2-3 inches past the garnish. If your experiment is correct, it should go inside the garnish..If not, it would be outside..

MvM · 14 June 2011

rsevo6 said:
Am relatively certain the VIS NSX-R hood doesn't work, just get rid of it, sell it to me:wink::biggrin:

Well, what do you think about doing TWO tests?
One with my car with the NSX-R hood and the front undercover and one with you car with the OEM hood?

GrounDDesignS · 14 June 2011

Pretty cool man.
Look forward to seeing the rest of your tests.

stuntman · 15 June 2011

Bogie Bog said:
Good experiment...You might want to use a longer tuffs similar to the Lancer picture. Stick it middle of the back window and about 2-3 inches past the garnish. If your experiment is correct, it should go inside the garnish..If not, it would be outside..

Not necessarily. Due to the size and location of the garnish, most of the air will probably flow over the inlet and over the trunk of the car rather than into the inlet. It will not be a definitive test. We already saw the smaller tufts go into the inlet.

0.02

MvM · 15 June 2011

stuntman said:
Not necessarily. Due to the size and location of the garnish, most of the air will probably flow over the inlet and over the trunk of the car rather than into the inlet. It will not be a definitive test. We already saw the smaller tufts go into the inlet.
0.02

For the next test I plan to replace the short 4" tufts near the rear window garnish with longer ones that have the length to go completely over the garnish. I am assuming that either they will all be sucked/blown into the garnish opening themselves. Or perhaps that some will not and will be pulled upwards into the airstreams.

To be continued.....

Bogie Bog · 15 June 2011

MvM said:
For the next test I plan to replace the short 4" tufts near the rear window garnish with longer ones that have the length to go completely over the garnish. I am assuming that either they will all be sucked/blown into the garnish opening themselves. Or perhaps that some will not and will be pulled upwards into the airstreams.

To be continued.....

Correct. Then we should have some idea whether or not it goes in or over the garnish....

Keep us posted.

greenberet · 15 June 2011

MvM – thanks for filming that.

ChopsJazz said:
So, it looks to me like the RWG is really doing it's job: drawing air into the back of the engine bay. But what else did we learn?

I find it nice to see that even though the airflow separates from the car about halfway down the rear window it reattaches itself to the rear decklid again very quickly. So with stock aerodynamics, the wake of an NSX is small and the rear wing gets clean airflow, whichever wing you have. The engineers who designed the NSX did a good job with the aerodynamics at the rear of the car.

BATMANs said:
have you thought about installing Vortex generators?

Those help on cars with steep rear windows like the Mitsubishi Lancer you pictured above where the airflow would separate and never reattach itself to the bodywork without them. With the gentle angle of an NSX’s rear window, the airflow reattaches itself to the decklid very soon anyhow and the rear wing gets clean air already. So installing vortex generators probably isn’t going to change much in terms of drag or downforce. However, if you can keep the airflow more attached over the lower half of an NSX’s rear window you might get more airflow into rear window garnish. Since vortex generators are most efficient if you mount them just ahead of the separation zone, you should mount them right across the middle of the rear window to get that effect.

BATMANs · 15 June 2011

greenberet said:
MvM – thanks for filming that.

I find it nice to see that even though the airflow separates from the car about halfway down the rear window it reattaches itself to the rear decklid again very quickly. So with stock aerodynamics, the wake of an NSX is small and the rear wing gets clean airflow, whichever wing you have. The engineers who designed the NSX did a good job with the aerodynamics at the rear of the car.

Those help on cars with steep rear windows like the Mitsubishi Lancer you pictured above where the airflow would separate and never reattach itself to the bodywork without them. With the gentle angle of an NSX’s rear window, the airflow reattaches itself to the decklid very soon anyhow and the rear wing gets clean air already. So installing vortex generators probably isn’t going to change much in terms of drag or downforce. However, if you can keep the airflow more attached over the lower half of an NSX’s rear window you might get more airflow into rear window garnish. Since vortex generators are most efficient if you mount them just ahead of the separation zone, you should mount them right across the middle of the rear window to get that effect.

Ugh I was afraid of that.

So there isn't any benefits from mounting them at the same location as the EVO?

stuntman · 15 June 2011

Bogie Bog said:
Correct. Then we should have some idea whether or not it goes in or over the garnish....

Keep us posted.

It will still not be difinitive if the really long tufts don't go into the rear window inlet because the majority of the air goes over the car and not into the inlet. I doubt the long strings would go in the inlet. We already saw the short tufts go into the inlet, if you want to be sure, mount tufts on the inside of the engine bay near the inlet and see if they blow out the inlet (which I doubt).

RYU · 15 June 2011

RYU said:
What type of engine cover are you running MvM? Stock? Perforated? None?

??? I'm very curious if you could be so kind to answer.

BATMANs said:
Ugh I was afraid of that.

So there isn't any benefits from mounting them at the same location as the EVO?

Afraid of that? I'm happy to know there is potentially no added benefit for those things.. I think they are particularly ugly.

BATMANs · 15 June 2011

RYU said:
......Afraid of that? I'm happy to know there is potentially no added benefit for those things.. I think they are particularly ugly.

I can make it look good. :biggrin:

geometro · 15 June 2011

For giggles, you can run a strip of turbulator tape straight across the middle of the rear window to see if it helps smooth things out...

whitebois · 16 June 2011

Pretty cool. You could save some time by only doing half of the car. The airflow should be symmetrical. Nice to see that the wing gets laminar airflow onto it.

My First aerodynamic test with wool tuffs

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