Aero mods and cooling

[Wimp Lo]

I think I want all air in the engine compartment to get there through the radiator.

I can probably find pictures of the undertray used in GRC Fiestas (they are airborne often enough) and start there for mine.

I have thought that a tubular K-member would be nice. I could make it lighter than stock, stiffer than stock with a brace, tuck up flat and provide solid under tray mounting points.

 

[Siestarider]

Ran yarn tests today, recorded with gopro in various locations. The approximate WRC vent locations exhibit unstretched yarn at speed compared to hood centerline which show yarn stretched tight to paint. But all the strands line up like you would expect, no obvious laminar flow failure on hood surface.

Looks like the WRC vents have a short upsteam lip, Even though pressure differential measured is good from beneath hood to above hood, the yarn suggests its a thin low pressure bubble on top. Maybe the lip makes the low pressure area above the vent a little larger, extracting more air volume from engine bay.

 

[Wimp Lo]

The lip enhances the low pressure area and kind of acts like an inverted splitter so the boundary layer on the body doesn't slow down the flow over the vent.

 

[Siestarider]

I hung around in the ecomodding forum some today, they have some pretty good tests of experimental methods of decreasing Cd. Front tray back to wheels looks like the best first mod to try for better cooling with stock radiator plus a little reduction in drag.

 

[Siestarider]

Going to record some more film on side of car, the way the hood is built seems there might be an option to vent just sides of hood behind headlights, leave top surface alone. Be a little stealthier.

 

[Siestarider]

Going to record some more film on side of car, the way the hood is built seems there might be an option to vent just sides of hood behind headlights, leave top surface alone. Be a little stealthier.

 

[Wimp Lo]

In my quest for WRC style hood vents, I found a source:

http://www.cars4youcustom.com/ford/exterior-parts/lightweight-body-kit-prototype-fiesta-r5-design

They have a US distributor and will be giving me quotes for fiberglass and carbon fiber.

 

[RAAMaudio]

Every good hood vent I have ever seen had a bump, lip, etc in front of the opening to divert air over them and induce a low pressure area to draw more air out from under the hood.

At the rear of my full length undertray I have have a downfacing lip to which was highly liked by the Ford Race Shop manager when he saw my car on the lift there

 

[Wimp Lo]

To be clear, the hood vent is essentially a lip around the top and front side of the cut out.

Let me try to insert a picture:

 

[Sourskittle]

To be clear, the hood vent is essentially a lip around the top and front side of the cut out.

Let me try to insert a picture:

Thanx. I needed the help on that one, lol.

Its like we are building our own rear engine super car or something.
Ducts for the brakes, lips and trays to push/guide into the intercooler/rad, hood vents to suck it out. You guys are mad, keep up the good work

 

[RAAMaudio]

Full length undertray incorporated into TR splitter.

It would be rather easy to make an aluminum extension attached with qtr turn fasteners to make the front of the splitter much more effective and wider as well and incorporate sections to direct air flow around the front of the tires as they do stick out a bit. Since the splitter is easily scraped on driveways, etc though the car is not that low, long nose adds to the issue, a removeable extension could be used just at the track or if a show car, shows.

------------

Duct added later upon recommendation by the Ford Race Shop manager after driving the car and seeing it on the lift.
I wanted to put two smaller ones further forward using NACA ducts but had none on hand, track even coming up, did this as an experiment and it helped under hood and overall temps considerably and no perceived loss in high speed stability, etc.....

Next I plan to add vertical sections in front of the tires and angled back towards the rear of the undertray to enhance the effectiveness of the unit, also recommended by the race shop manager.

As mentioned adding the undertray sealed up(would need a little finish work to be fully sealed) center duct below the bumper cover that extends out towards the wheels, curves back as using the mounting flange for the stock air dam, perfect to tap into for brake cooling.

 

[JasonHaven]

Dear god, can someone edit the title of this thread already?

 

[Sourskittle]

https://vimeo.com/150841865

Someone at dodge wanted us to be jelly.

 

[Chuckable]

Wait, what car is that?

 

[Sourskittle]

Dart 2.4L

 

[Siestarider]

Maybe the cooling part of this thread is being missed by some.

RAAM's undertray mods definitely affect aero, and I believe the cooling theories referenced in the original technical paper are also in play. Simplest version, for best aero dump the heat to a low pressure area as far behind nose of car as you can. Question is whether this approach can also improve heat extraction from engine bay.

I am still playing with yarn and gopro, confirmed today that hood side vent yarn behaves just like the top behind headlights, so side vents should work with a little lip to assist.

Next up for me is a test undertray mounted up behind the stock air dam and reaching back to lower A arms inner mounts. Not to improve aero per se, but to improve radiator and IC cooling flows. The air dam extension experiment enhanced low pressure area behind it.

Now there is a larger radiator and many larger IC's on market, but is it possible to retain stock radiator and be happy with it on track? I hope yes, just have to find a way to do it.

 

[TyphoonFiST]

Dart 2.4L

it's a SHART....not a dart. Shit + fart= Shart= dodge Dart. IMO.

 

[Wimp Lo]

If the Fiesta didn't have cooling issues when tracked hard, this would just be an aero thread.

What it comes down to is that all the air that goes under the bumper/splitter is air that isn't going through the radiator and hurts the low pressure area behind the radiator. Also, all the air that goes through the radiator and exits under the car is increasing drag so the aero treatment you see in WRC is the key to cooling and drag reduction.

I'm not terribly concerned about drag reduction but I want to do anything that can improve air flow through the radiator and intercooler so I can push it as long as I have gas in the tank.

 

[Wimp Lo]

Siestarider, where can I find pictures of your brake ducts?

After we fix the coolant and oil temps, the brakes are the next problem.

It sounds like Velossatek might make ducts for us and CMbuilds makes dust covers with ports for a duct hose.

Some combination of parts like that should help us keep the pads and fluid from dying too fast.



RAAMaudio, do you have a guide to how you stretched your front fenders?

I figure anyone who tracks would be using wide tires so we should make sure all of those parts work in the most likely configuration for a street/strip or track mostly car.

 

[Siestarider]

Pics are on this Forum somewhere in several places, but exterior shots are not well lit so hard to see. I will shoot new ones and post with CMB Racing brake cooling shield tests, will have to remove front clip to install hoses and it will be easier to shoot both inside and outside views at same time.