Aero improvement, or roadhugging weight?

redvetracr said:
I`m curious about one thing...how do you plan on sliding a jack under the car at the race track in case you have to bleed a caliper or change a tire?
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Well, I don't know if I have quite the level of confidence in my Wilwood calipers as others might, but fortunately it's just a street car so I don't have to worry about quick pit stops or anything like that. The rockers only hang down an inch below the frame (level with the trans crossmember) so I'll probably just put a 2x4 under the frame for rocker clearance and then slide the jack under the board.

At least that's the plan for now. :amused:
 
Well, I put the everyday tires back on the car, and I have 5" of clearance under the rockers. Worked well with the jack and a 2x4. The Hoosier tires are about the same height as the Goodrich tires, while the Nittos are about a half inch (radius) less.

IM001997.jpg


I've had the front outer grilles blocked off for the last year to reduce the amount of air getting shoved into the engine compartment. Two of the recent track days have been 98*F (Topeka) and 95*F (MAM-Iowa) and no overheating. I recently blocked off most of the center grill to reduce the air a bit more. We'll see if that will be an issue at the next track day. Fortunately it only takes about five minutes and a philips screwdriver to take it out.

IM001998.jpg

I'm also kicking around an airdam/tubing arrangement mounted under the (differential pinion bracket) crossmember to catch some of the air hitting it, and then directing the air out the rear wheelwell or caliper area to cut down on the amount of air that gets caught in the taillight area. It would take a lot of work to (aerodynamically) clean up the spare tire bucket area, so this is just something to bandaid the issue for the short term.
 
I made a set of side skirts for mine out of a plyable rubber that will bend up enough to let you get a low profile jack under it.
 
69427,

When are you going to be able to get the car out and see if your mods are an improvement? How are you going to measure or validate any change in performance? Seems like on many road courses, you'd spend little time at speeds that might use this approach to your benifit, but I could be way wrong. What kind of higher speeds to you see and for how long? How fast do you think you need to be going to get the benefit from your mods?

I understand aerodynamics just enough to be dangerous, but I'm an avid F1 fan and understand how much a small aero change can make on those cars, but that's about as far from our C3's as you can get and still have wheels. I'm very curious to see what improvements you see and to know if you have any temp issues from restricting the air flow through the engine compartment.

Thanks for sharing!!
 
damoroso said:
69427,

When are you going to be able to get the car out and see if your mods are an improvement? How are you going to measure or validate any change in performance? Seems like on many road courses, you'd spend little time at speeds that might use this approach to your benifit, but I could be way wrong. What kind of higher speeds to you see and for how long? How fast do you think you need to be going to get the benefit from your mods?

I understand aerodynamics just enough to be dangerous, but I'm an avid F1 fan and understand how much a small aero change can make on those cars, but that's about as far from our C3's as you can get and still have wheels. I'm very curious to see what improvements you see and to know if you have any temp issues from restricting the air flow through the engine compartment.

Thanks for sharing!!
Click to expand...

I'm hoping to get another track day done sometime in the next couple weeks.
I don't have any timing equipment or time to do any A-B comparisons, so it's just going to be some delta pressure measurements with my gauge, and some SOTP impressions.
Regarding "when" this should be beneficial, I expect that it should pay off during braking and cornering. Obviously it will be unnoticable on the slower sections, but hopefully it will incrementally improve the braking and cornering performance as speed goes up by reducing the front end lift. I don't expect actual downforce from such simple modifications, but even reduced lift at speed will be an improvement over the stock configuration.
I've only made one change (blocking the majority of the center grill opening) that might have an effect on cooling. If cooling is an issue I can remove the blockoff material in just a couple minutes.
 
You might check out a couple of the phone aps - for Droids at least.
I just bought a Galaxy Tab (7) and am looking at TRACKMASTER for the car/track day app. [I'm a bit late to the whole handheld phone/stuck in your face all day thing, but am willing to play on the edges for utility.]

It integrates Google Earth, apparently has a bunch of tracks loaded - and cheap at under 10 bucks.

Cheers - Jim
 
Coastdown/Decel data logging?

I'd like to figure out a handy/inexpensive way to measure/log decel speeds/g's during coastdowns (120-40 mph perhaps) to give me some indication of aero drag changes. (I've got some accelerometers and other parts in a box somewhere, so I could probably build something, but these days I just prefer to spend my time driving the car rather than sniffing solder fumes.) Any suggestions?

Thanks,
Mike
 
69427 said:
I'd like to figure out a handy/inexpensive way to measure/log decel speeds/g's during coastdowns (120-40 mph perhaps) to give me some indication of aero drag changes. (I've got some accelerometers and other parts in a box somewhere, so I could probably build something, but these days I just prefer to spend my time driving the car rather than sniffing solder fumes.) Any suggestions?

Thanks,
Mike
Click to expand...

Get a copy of the sae coast down standard. All you do is log speed during coast down on a level road and run the data through a program they give you.
 
BBShark said:
This guy used a wiimote and even dumped the data to Excel. We tried this at work a few years back and it worked great. You could also plot a graph

http://www.engadget.com/2007/07/31/car-modder-repurposes-wiimote-as-accelerometer/
Click to expand...

iPhone got a pretty accurate accelerometer too, there's tons of Apps.
http://gizmodo.com/5030749/iphone-apps-we-like-dynolicious-car-performance-meter

Some are ever free :
http://reviews.cnet.com/8301-13746_7-10424432-48.html

If it's just about logging the Gs, a couple of hours is all it take to code such application.
 
69427 said:
BBShark said:
This guy used a wiimote and even dumped the data to Excel. We tried this at work a few years back and it worked great. You could also plot a graph

http://www.engadget.com/2007/07/31/car-modder-repurposes-wiimote-as-accelerometer/
Click to expand...

I checked our favorite auction site and it looks like those Wiimotes are available pretty cheaply. Now I just have to figure out the details of operating the thing and the interface issues.

Thanks for the suggestion. :thumbs:
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Wooden you have to have a WII game console for the thing to talk to??

:skeptic:
 
mrvette said:
Wooden you have to have a WII game console for the thing to talk to??

:skeptic:
Click to expand...

No, you don't need the game console. There is tons of stuff on the internet using a wiimote for just about anything.

Hardware Requirements

You don't need much in the way of hardware to get your toes wet. Just a Wii Remote and a computer with a Bluetooth interface are required, but the Nunchuk, Classic Controller, and Sensor Bar are also supported

http://www.joystiq.com/2007/06/12/revolutionary-introducing-glovepie/
 
Aren't there apps that let you log data from the cars data bus? Just log speed, it would have to be way more accurate than a kids arcade game.

There is lots of info in the SAE standard that should be followed. Some local gov'ts make road survey data available, making finding a level road easier. SAE says to run two ways and average to remove grade effects, but less grade is better.
 
Kicking around another item to play with. Looks like it would be easy to get some delta pressure measurements also. For years I've seen some ("frame level") flat plates in front of the rear wheels of formula cars, and it strikes me as an effort to get some downforce from the air that strikes the rear tires (and possibly gets trapped a bit as the tire rotates). It looks like I could install some quasi-similar plates and easily hook up some tubing to my pressure gauge. Here's a mocked up setup.

IM002004.jpg

I don't know if this will be productive, but the material requirements are minimal, and it won't take much time to install a couple pieces of aluminum sheet onto the frame bottom in that location. If it doesn't work I'll just reuse the aluminum pieces for other projects, and the frame will be a dozen grams lighter due to the bolt holes (so it looks like I win either way :amused: ).
 
I have a question about inner genders and air flow control. I have converted the front end so it comes off with a few pins. Right now the inner fenders are off but not sure if to refit with dzus fastners. Car is street and track day with more focus on track.
 
I don't know the range of pressure you're supposed to measure, but let's take this sensor :
http://www.sparkfun.com/products/9602
Hooking them to an Arduino nano (15$) and hook the nano to a laptop could be pretty easy and cheap to do.
I've been tickling with micro-controllers and sensors, I can help.
 
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