hondaapi

I searched a lot but could not find good informations.

Are there any real flat undertrays available for the EGs?

I´m really at thinking about building a complete undertray for our car which leads into a diffusor.

I wanted to combine it with our P1 splitter kit where I want to build a new blade which goes up to the front LCA.
I also had the idea to buildt a complete new 3" exhaust system and put it high enoug to make a flat undertray fit.

I recieved some pics from Kiwi but do some other people have some further ideas?

meb58

I am sure you know that the splitter, undertray and diffuser all work in sync and are typically wind tunnel tested to determin efficiency and effectivness...

I guess the point I am making is that even an exposed rivet can hamper air management...the subtleties in the design are critical; how the diffuser merges air from the roof and or upper portions of the body is super critical.

I had the opportunty to spend a fair amount of time working with a BMW F1 aero engineer. We were looking at ways to improve my Mini's aero - a brick essentially. In the end I leanred a lot and found that some minor modifications - cheap and effective - were about as far or as deep as I was willing to go. Producing an effective design is super expensive.

...as a note, some of those flaps sticking out under our productions cars produce a much more effective aero package than if they were removed. Counter intuitive for sure.

night

what about simple drag improvements.. covering the engine undercarriage to the firewall and from just behind the rear axle line to the bottom of the bumper. No diffuser design, just making it smooth.
Although if you have a splitter I'd imagine under the engine doesn't see much drag, so perhaps just the rear.

GSRCRXsi

I would also put some sort of venting to keep the exhaust cool if you plan on covering it up.

kristo

Some collected links:

Special Projects Motorsports: Technical: Aerodynamics

Modified Magazine: Automotive Aerodynamics

Autospeed Magazine: Modifying Under-Car Airflow

http://www.fatcatmotorsports.com/iga...o_articles.zip
Stock Car Science: The Splitter Material


Fora:

Time Attack Forums > Aero Dynamics

dirty19

iTrader: (1)

Kiwi is our best resource for aero over this way.
If he doesnt have a kit for the undertray it's because there is no market for it, or it's not legal for use with the sanctioning bodies that most of us participate in out here in the USA.
Thats not saying he couldn't produce something like that if the right deal came along.
He is a businessman/racer, and his breadth of knowledge is superior to most out here.
I say pick his brain some more, also check into the time attack people a bit more closely.
They tend to be the types who use every bit of aero you are talking about because their rules allow for it in the higher classes.
Regardless... building something like that will take alot of resources, testing and finding ways to make it all aerodynamic, so it all works.
GL keep us posted.

descartesfool

Always good to look at proven wind tunnel designs for inspiration.

GT-R, Drag coefficient of 0.27 and mild downforce

F430 looks good from underside as well.

powerneedy

Not saying this source is perfect but it says the gtr is only a .32? regardless lots of cars and good info, like c d but also lift

http://www.genmay.com/showthread.php?t=827884

elfather

cool link !

vtecjj

educate me.
subscribed

descartesfool

The pictures in that link are all taken from the magazine SportAuto's Supertests. They test all the cars in a Mercedes Benz wind tunnel which does not have a rolling road, and thus they get numbers slightly different than the manufacturer published ones.
They test all the world's fastest cars, including lap times at the Ring and at the Hockenheim F1 track for comparisons. For example, see this one on the newest BMW track edition of the M3 GTS:

http://www.sportauto-online.de/super...e-2206288.html

Click on "Wertungen" tab and then on tab 4 which bring you to Windkanal.

GT-R 2012 model is claimed by the factory to have improved aero downforce and drag coefficient lowered to 0.26, which is a stunningly low number.

Here is the F430 underbody. Somebody is going to have to work long and hard to try to match a typical factory effort on a super smooth underbody:

exgr

can you give some examples of these flaps you're referring to?

night

how much benefit would it really be for a FWD. unless you can get the front to stick like glue, wouldn't more in the rear be counter productive

Driven

except what you posted isn't the underbody of a F430, that's an enzo.
mirrors are on the fenders (Enzo) vs the doors (F430), rear brake duct is more forward, front fender vents (F430 doesn't have any), etc.

meb58

In the case of the mini, it has a flat piece of heavy duty plastic sitting aft of the fire wall extending about 1.5" into the wind below the body from nearly inside of tire to inside of tire. Removing this rather blunt object, I was told, would increase drag significantly.

It is not elegant but it apparently works on a car that is otherwise a brick; very short front over hang, fairly upright windscreen and short-ish body with a rather blunt back end. And folks call it cute...

I was told that managing heat is one of the most difficult parts of designing an under tray. But in F1, aero dominates everything so I imagine all else is relegated, to some degree, to aero.

Also, trapping air beneath the car is critical...it cannot escape out in front of the rear wheels...I am trying to remember a bewildering amount of information...most of which was far above me. But the Mini in particular is at a huge aero disadvantage; a lot of front over hang helps to keep air more laminar as it moves over the car and a longer back end with an extended diffuser ( the actual length and angle is critical and tailored to the characterisitcs of air as it moves away from the back end of the car). Here the wind wake must be fairly tidy. There is much much more but I am, I think, over my head.

Wind tunnel testing proves out good designs. But upper body shape determines the path taken at some level.

Regarding hatch backs, I was counceled very hard by my F1 contact to create spoilers on each side of the rear most side glass as it rounded into the rear hatch. The idea here was to cause the air to stay as close to the body for as long as possible. The newer Minis have these spoilers fachioned into the rear pillar...but they are a bit smallish. I was told that the "stylists" reduced the final functional shape a bit.

Also, aero results require a fair bit of speed to work. My goal wasn't so much down force as it was making the car more slippery. It - the mini - was awful at tracks like the Glen. Just shy of 2,500 lbs, the 210hp and 193 lb ft moved the car along very well...until about 110 mph hwere aero drag really began to ruin acceleration.

Side view mirrors are a big drag iten BTW...and so are wide tires.

Apologies for the blah, blah, blah, but I am amused and amazed by aero.

hondaapi

Thanks for the input

So, a flat undertray on a Civic would be an advantage if it is designed like the Ferrari or other cars with entire flat undertray leading in a diffusor?

As far as I can remember one of Kiwi´s Integras also had a full undertray with some sideskirts leading into a diffusor. As far as I can remeber he wrothe that in made a lot of overal downforce.

Of course there are many problems to think about - for example the exhaust system - specially on a turbocharged civic ... :-)
It also needs to be easy to remove ....

I can understand that there is no market for because it will be hard to fabricate ... and for sure, expansive...

dirty19

iTrader: (1)

I have never seen a whole undertray on any of Kiwi's cars but thats not to say he didnt make one.
I've only seen a splitter and side skirts.
The Kiwi is a crafty one though. innovation is one of his strong points.
Now you have me wondering... I think its time to go visit him again in his new shop.

fireant

Reminds me of a rare Honda accessory for 96-00 hatches:



Ignore the mid-wing, I'm talking about the side spoilers. I'd love to know if they help and how much.

descartesfool

A little closer to Honda land.

A Password JDM brand kit for an S2000

http://passwordjdm.com/PasswordJDM-D...P2421C393.aspx

And an F430 aero package (not Enzo this time!) being tested in a wind tunnel, going one past the factory design: http://www.worldcarfans.com/10611145...ynamic-program

Stinkycheezmonky

Maybe I'm misinterpreting data, but I remember seeing that side view mirrors accounted for <2% of a car's frontal area, and did not have a huge effect on drag. Some, yes, but not much.

For a picture of a good "sidewing" design, see Adam Jabaay's red hatch (redzcstandardhatch on here). I'll post one if I can find it.

dirty19

iTrader: (1)

I think it was the post about mirrors and Johnny Mac chimed in about his findings with the mirrors.
Since he is an aero expert id believe what he says!

Stinkycheezmonky

Paul, do you remember where he posted that? I had read my thing in an issue of Racecar Engineering, in an article that was (I thought) also written by an aerodynamicist. They had some wind tunnel data to back it up, if I remember right. However, this is all going off my memory of something I read in a magazine. Take that for what its worth

redzcstandardhatch

[/quote]

dirty19

iTrader: (1)

I think it was this post here. Johnny talks about the APR mirrors.
He actually came back and posted a second time explaining more. Good info.
https://honda-tech.com/forums/showth...hlight=mirrors

essex

I think lifting the back of the hood sucks air back into the bay not let it out.