Aero mods for chumps...

[Vanquizor]

We're fielding an entry in the ChumpCar World Series, and since the rulebook has absolutely no restrictions on what can be done to it other than the dollars involved it seems to me like an excellent opportunity for some aero development.

The car we're working with is a '96 Dodge Neon. The first track we're running is a little over a 2 mile road course average speed last time I ran it in a simmilar sedan was a bit over 75 MPH, top speed 120MPH, minimum speed 40MPH. The car is basicly gutted with an FIA spec cage and no glass other than the windshield.

Stuff that we test with or use to develop the car is only limited by my pocket book (reasonable but no wind tunnel time), but to stay on budget for the race what we bring to the track can't tally more than ~$100 materials. For tools I've got a good chunk of basic racecar fabrication and repair tools, and a cheapie digital differential manometer.

Actual testing time with the race car will be limited since it is not platable and track time is expensive, but I do have another platable neon which some development work can be done with (this one has all the glass in it).

I'm guessing anything forward of the A pillars should translate well between the two, I'm not sure how much of the underbody stuff from the street legal version will cross over, but I'm sure anything I learn on the upper rear surfaces will be all messed up by the lack of glass in the actual racer.

Given the goals of minimizing drag and maximizing downforce, If this was your car to develop how would you proceed?

[redneck]

Given the goals of minimizing drag and maximizing downforce, If this was your car to develop how would you proceed?

2 words...

Air Dam



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[botsapper]

Cool & fun racing! ChumpCars/24 heures du Lemons! What's your theme? (& budget?)

...assuming, everyone here would love to see a racing BOATTAIL!!!

...& resplendent, in rainbows of Coroplast!!!

[BamZipPow]

Since yer going cheap...use plastic wrap fer the lack of windows...

[Vanquizor]

Air dam is pretty simple, are really I'm more looking to be more ambitious... theme is up in the air, depending on how the modifications go, but right now we're kicking around doing a "Lightning McQueen" theme with a fully developed electrical system. In that case budget will be a MAX $100 for aero. Of course we could do a 'Life's a drag, racing shouldn't be' theme...

I would expect for $100 worth of material hanging on the car one could have a well developed underside including underside (flat? Venturi?), front splitter, and diffuser. Developing some low drag ducting for the cooling system should be mostly time but very little dough. Figuring out what to do with the glassless back half of the car shold be fun too.

To put some context to this I have done a fair bit of reading in regards to automotive/racing aerodynamics... there is sufficient material to give me a reasonable sense of what is possible and what others have done. The one area that is woefully lacking is advise on where do you start so that the testing and knowledge you gained on day 1 isin't completely invalidated because of the change you made on day 11?

Ideas aren't really where I need the help , more the methology for development. For example:

I was thinking the first thing to do is find out what kind of airflow the stock neon has through the radiator at 75MPH so I know what I need to have... The stock system seemed to hold up well to track days in my IT car.

If I measure the pressure differential in front of to behind the radiator in a few spots and ensure that same differential or greater is present in my final design that should ensure it cools as well as stock right? I guess the other variable I should monitor is underhood temperature to ensure adiquate cooling...

Here I'm working with the general idea that working towards sealing off the underside of the car is the right direction to go, and that by ducting air to/from the heat exchanger I can also minimize the size of the grille opening to also help aero. Also that this is a logical place to start...

Would it be fair to use the pressure measurments from various points along the underbody to evaluate the lift/downforce changes of a belly pan? MPG or coasting could tell me the drag side, but I bon't have shock travel sensors in my collection of bits to use rideheight to evaluate downforce.

I really need to make a gameplan of what to do in a step by step fashion...

[Vanquizor]

Turns out lexan can be inserted in place of the removed rear glass so the aero back there may not be that different from the road car...

[redneck]

Given the goals of minimizing drag and maximizing downforce, If this was your car to develop how would you proceed?

Just my .02 cents.

A front air dam will have a large effect on the reduction of lift, with a minimum increase in drag.

If there are no rules on the size of a air dam, I would make it as large and low as possible.(maximum effect)

Road races are usually won by whoever is the fastest going in, through and out of a turn. A large air dam will help that happen.

But then again, a air dam is but one tool in a bag of tools.




I never heard of ChumpCar Racing before. It looks like my kind of racing.
(cheap & fun)


In case no one else is familiar.

http://www.youtube.com/watch?v=sMnhF...layer_embedded

I see that the series will be in my neck of the woods this weekend coming. I might have to go.

29-30 January 2011
Roebling Road (Bloomingdale, GA)
January Junkfest!

I've been around that track a few times but it was on two wheels.

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[botsapper]

Do you have a picture of your of your Neon? You did not make clear if you have a coupe or a sedan.
Your initial interest in racing aero development is for better downforce and low drag. Aerodynamic efficiency is the goal for your campaign. You mentioned it would involved different tracks with different racing circuits requiring different aerodynamic and mechanical setup. Short/Street narrow course; slow tight turns with long straightaways, requires braking cooling ducts and top speed profile. Road/raceway; wide open track with both slow and high speed corners, requires brake cooling, balanced downforce -front splitters, corner canards & rear wings. Speedways/ovals; highest sustained aerodynamic efficiency, least downforce.
The most obvious aero improvement will be the flow management over the OPEN window openings. As the airflow moves toward the rear, the missing windows create such turbulent flow and speed-sucking drag. Even if you add a rear wing, the downforce/efficiency is compromised by disturbed flow. Recommendation to have the best aero profile. Replace windows w/ clear lexan. Weld on a 'boattail' cage rails to the back with the best aero profile, cover/rivnut on lexan sheets.
Here's the recurring template for the ideal teardrop profile. http://ecomodder.com/imgs/ideal-teardrop-comparo.jpg
Other low hanging fruit; air dam, adjustable grill block, wipers deletion, side mirrors deletion, side skirts, rear wheel covers, rear wheel spats, belly panels, rear diffuser, etc.
PS. Just for laughs, apply in uniform pattern, ball peen hammer strikes on all metal surfaces for the famous golf ball aero dynamics!!!

[mcrews]

ball peen hammer strikes on all metal surfaces for the famous golf ball aero dynamics!!!

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"I used to be a golf ball....."

"I hope Bertha doesn't show up""

'No mo ants!!"

"Hail Damaged.....and Proud of It!"

"Peen Damaged ...and proud of it"

"I said NE ON it.....Not Peen on it!"



ok....I'm a marketing guy......

[Vanquizor]

Apparently I can't post pics till my post count is higher but it is a 4 door sedan we are working with.


The courses we are running are all pretty substantial road courses, or Rovals. I can't even recall the last time I used first gear and wasen't in the pits. The vehicle is definately horsepower limited, so drag reduction will be my primary focus with downforce being secondary.

Maybe I'm looking at the whole airdam thing wrong, but I am under the impression that if we go to the point of developing an effective splitter, smooth bottom and diffuser an airdam will not generate more downforce, and may hurt both drag and downforce.

I guess ground clearence comes into play here too- the plan is to be about 4-4.5 inches off the ground at speed, and have enough bump rubber in the car to keep the nose off the track when hammering the curbs