Underbody aero

[jaydog is back]

Nice work on the rear diffuser. It really doesnt matter if you have a frt or rear wheel drive car as far as the front lower cover. The newer BMW's have an almost complete, flat undertray with the exception of a cutout for the exhaust. Looking at the BMW's undertray, the only holes cutout are for the exhaust headers for the big v-8. There are inlets for the brake ducting and 2 smaller naca style ducts practically underneath the huge radiator. Looking at this, I could make a very similar undertray on the Mx-3.

For the front, with the MS front bumper, I am going to extend to make larger fenders, a lower splitter and attatch a stiff undertray underneath. I will most likely make it with the naca ducts like the BMW to help air escape. For the exhaust, it will have a cutaway, and a divided undertray on either side. A very crazy way of letting air out is to re-shape the front doors/fenders with a giant outlet on either side. This was seen on the German DTM, Audi TT racecar.

[WhiteFinish]

That's an old picture of Mike's car.

Where did you find it ?

[Josh]

Front and RWD do matter. it is about aerodynamics and the weight of the vehicle. Also an under tray on a FWD is more critical to airflow than a RWD platform. As air needs to be vented through the tray for proper cooling, It does on a RWD as well but the vent placement is not as critical. the rear diffuser looks great would like to see better pictures of it though.

[mx3matt]

if i could find more pics of this setup i'd be all over it, looks wicked and i'd be after it for aesthetics anyways lol

[Josh]

yeah I have run the exhaust of my RS out the center exactly like this car with same size tips just I used OE RX8 tips, and was debating adding a rear diffuser of some kind but not sure if I wanted to do more of an EO design or racing inspired design like this one.

[WhiteFinish]

Here are some more pictures of the car.

Unfortunatelly parted out 3 years ago.

http://jeroentje.nl/index.php?page=car_view&car_id=4

[jaydog is back]

Front and RWD do matter. it is about aerodynamics and the weight of the vehicle. Also an under tray on a FWD is more critical to airflow than a RWD platform. As air needs to be vented through the tray for proper cooling, It does on a RWD as well but the vent placement is not as critical. the rear diffuser looks great would like to see better pictures of it though.

Air flow is coming in through the front bumper in any case, so I don't really see your argument there. A cover underneath the engine would be to reduce turblent airflow as well as panels under the car, but that's only one of many effects of underbody aero. Airflow can just as easily "escape" no matter if its front or rwd. I don't understand what you are trying to say here..

To have a worthwhile undertray will need to be ultimately road tested. Have you tested an undertray on an Mx-3, only a question? Are you saying I must do something different than a rwd car??

[Josh]

Front and RWD do matter. it is about aerodynamics and the weight of the vehicle. Also an under tray on a FWD is more critical to airflow than a RWD platform. As air needs to be vented through the tray for proper cooling, It does on a RWD as well but the vent placement is not as critical. the rear diffuser looks great would like to see better pictures of it though.

Air flow is coming in through the front bumper in any case, so I don't really see your argument there. A cover underneath the engine would be to reduce turblent airflow as well as panels under the car, but that's only one of many effects of underbody aero. Airflow can just as easily "escape" no matter if its front or rwd. I don't understand what you are trying to say here..

To have a worthwhile undertray will need to be ultimately road tested. Have you tested an undertray on an Mx-3, only a question? Are you saying I must do something different than a rwd car??

Yes, it is a matter of effective cooling, not necessarily just aerodynamics. having a FWD vs RWD causes a blockade in the engine bay. RWD does not have this problem. with an engine and trans lying horizontally across the bay it cuts the flow down in the bay, air has to escape, and escape properly. look at real designs for FWD and RWD they are different. If you were to make a solid undertray you increase the potential of running hot. If air does not escape the engine bay you will cause an air dam, same goes with RWD, but generally the way RWD is set up air will escape through the rear of the bay along either side of the engine.

FWD Acura RSX only covers the front half


AWD Subi runs a horizontally apposed engine


RWD RX8 they run very hot thus the louvers


GTR - has hood scoops and engine tray is open and the back end.




S2K RWD there is a louver in the front to help with flow of the engine bay



Good example of RWD for a corvette


AWD Lancer but transvers mounted engine

Evo 8


The point is if you run a flat piece of whatever you are causing dead air in your engine bay and could result to ineffective cooling and or you could just be creating an air dam, doing you more harm than good. Air flows through a RWD front to rear mounted bay easier and more effectively than a transverse mounted engine bay that is why they can use a flat piece of whatever material and we cannot, we have to have some kind of louvers to help with the flow. IMO the RSX is the closest race inspired car to which we can steal design ques from that have been track tested.

[jaydog is back]

K, I can understand the concept of the cooling effects. The pics were pretty clear to me. The next challenge is actually making it work on an Mx-3. Vents. louvers, and naca ducts can be employed where they are needed.

BTW, the first pic isnt an RSX. This car has a diff front suspension and I can see the trans running to the rear.

[Josh]

Well someone on the forum here has a MazdaSpeed catalog with 323 GTR pics of the optional undertrays. If I ask him very nice he may post some pics of them and that would be very helpful.