EXTERNAL AERODYNAMICS

[rtj]

Interesting, nice looking CF. I’d have to win the lottery before I bought parts from them.

 

[phantomjock]

Gorgeous workmanship.
I'd be tempted - but hate cut a diffuser into that CF airdam - but it might be useful...
The appears to be a lot of real estate available.
(I'll admit - I just watched - didn't listen to the audio) Could have missed a clue there.

Cheers - Jim

 

[rtj]

Probably be better off picking up on of these second hand and adapting it to the car.

 

[rtj]

Grabbed a pair of these before prices (possibly) increase. Going to get back on the cars soon.

 

[69427]

Had a good time at the last track day a few weeks ago. The car ran great, the extended belly pan length didn't break, and the air dam extension (downward) got just enough scratches on it to let me know that's as low as I want to go for now. The next track day is this Sunday. For this weekend I blocked off the center grill as much as I can, and removed the covers I had over the two radiator air feeds underneath the outer grills. I'm just trying to whittle down the amount of air I let into the engine compartment that eventually tries to find its way under the car. (I don't know why I keep seeing two pictures when I'm trying to just post one.)

View attachment 57587

 

[phantomjock]

It's because they are 2x GOOD?
Nice rake - or are you on the brake?
Looks real sweet on the track.

Cheers - Jim

 

[69427]

It's because they are 2x GOOD?
Nice rake - or are you on the brake?
Looks real sweet on the track.

Cheers - Jim

Thanks. I was probably braking for the 90* right hand corner just out of the picture.

 

[BBShark]

Grabbed a pair of these before prices (possibly) increase. Going to get back on the cars soon.

View attachment 57579

Like those

 

[rtj]

Amazon had the best price. I’ve seen other APR stuff on there at good prices, but don’t hesitate if you want it.

Picked up a nearly new Kirkey the other day locally. When you consider no shipping, it was close to 50% off. The shipping and occasional movie makes my Amazon membership worth while.

 

[69427]

Yesterday's track day went well. Nothing broke or got scratched up. A few conclusions I came to during the day:
1) I need to brake later. I'm still trying to get accustomed to how much quicker the car decelerates with the decreased weight.
2) The car is very neutral through the corners, with a touch of oversteer when I ask for it.
3) I'd like more front grip. I can't find many more ways to pull weight off the car, so I may have to look for other methods (stickier tires, steering geometry changes, etc). I'll be starting another thread regarding Ackerman geometries pluses and minuses. I can move the steering rack position pretty easily, but I don't have a sure way to decide which position is best for my situation.
4) And finally aerodynamics. I'm getting down the straights quicker than before, the car feels steady, and the brakes and engine are apparently cooling sufficiently in the process. A problem I ran into repeatedly was the headlights popping up at about 120. I don't have the vacuum system re-hooked up after I pulled out the vacuum tank, so I had to manually close the lights after each session. I don't know if the problem is purely aero pressure getting under the headlights (or maybe entering the headlight opening gap behind the front bumper), or if it's a combination of that and no vacuum in the actuators to help keep the headlights down. I welcome input or suggestions about this issue, as my plans at the moment are to reconnect the vacuum lines and perhaps install a small plastic vacuum canister to compensate for small vacuum leaks in the system.

 

[phantomjock]

4) DUCT TAPE!!

Or, LeMans buckets might be shallower if using modern rectangular LEDs.​

Then, you could swap the fiberglass covers with lexan and transparent blue mylar.​

Would look "semi" stock." Maybe less weight too. The stock light buckets are pretty heavy - mechanism, etc.​

2) I guess that touch of oversteer is from a throttle "Blip"- or drop?" "...when I ask for it."
I enjoyed "pointing the nose" of the little racer that way. It was a real hoot.

Cheers - Jim

 

[rtj]

The electric solenoid headlight conversion is pretty well documented diy project. Or, remove the headlights completely and install fill pieces. Those things are very heavy.

I know you want to keep the stock look, so the vacuum tank might be easiest.

 

[rtj]

https://americanraceronline.com/aor_site/wp-content/uploads/2023/06/2025-Catalog-PP-to-PDF.pdf

These guys have a large selection of 15” tires. Also, DOT rated tires.

The Goodyears the cobra guys like (billboards) are supposed to not last. Hoosier has some selection.

 

[metalhead]

Yesterday's track day went well. Nothing broke or got scratched up. A few conclusions I came to during the day:
1) I need to brake later. I'm still trying to get accustomed to how much quicker the car decelerates with the decreased weight.
2) The car is very neutral through the corners, with a touch of oversteer when I ask for it.
3) I'd like more front grip. I can't find many more ways to pull weight off the car, so I may have to look for other methods (stickier tires, steering geometry changes, etc). I'll be starting another thread regarding Ackerman geometries pluses and minuses. I can move the steering rack position pretty easily, but I don't have a sure way to decide which position is best for my situation.
4) And finally aerodynamics. I'm getting down the straights quicker than before, the car feels steady, and the brakes and engine are apparently cooling sufficiently in the process. A problem I ran into repeatedly was the headlights popping up at about 120. I don't have the vacuum system re-hooked up after I pulled out the vacuum tank, so I had to manually close the lights after each session. I don't know if the problem is purely aero pressure getting under the headlights (or maybe entering the headlight opening gap behind the front bumper), or if it's a combination of that and no vacuum in the actuators to help keep the headlights down. I welcome input or suggestions about this issue, as my plans at the moment are to reconnect the vacuum lines and perhaps install a small plastic vacuum canister to compensate for small vacuum leaks in the system.

i'm running the mx5 (miata) electric motors on mine. Never have to worry about them popping up by themselves again, and gets rid of the vacuum hoses (only vac line left on my car is PCV). I did measure the weight at the time, from memory I think it was pretty much a wash between the motors/wiring and the vacuum actuators and hoses. I did end up making some double shear brackets for the motors, I eventually cracked the single shear brackets (sourced from the Corvette Forum). But my car does get a lot of use and hard use at that.

 

[phantomjock]

I was hesitating posting this one. I was going to keep it "my little secret" but there is an opportunity rising here.

UOP Shadow was a unique CAN-AM team that brought a lot of innovation (in External Aero) to the track.

Here is an example that could be a potential solution to increasing front grip, eliminating the weight of headlight buckets, and vacuum tank..
It would involve a reasonably-fast acting (solenoid) ACTUATOR set up, a modified headlight assembly, and sort out some switchology.


This video was shot at Goodwood in England last year. LINK:

At the 5 minute mark you'll note the deployment of the front and rear spoilers. No brakes lights in the video, so unclear if tied to a brake switch or manually operated.
A "Plug-and-Play" headlight bucket could offer track toy and still double as a DD. Just need some switch-thinking. Definitely require some testing and a cooperative series.
I'd think track-days would be pretty open. Could be fun.

Cheers - Jim

 

[BBShark]

Yesterday's track day went well. Nothing broke or got scratched up. A few conclusions I came to during the day:
1) I need to brake later. I'm still trying to get accustomed to how much quicker the car decelerates with the decreased weight.
2) The car is very neutral through the corners, with a touch of oversteer when I ask for it.
3) I'd like more front grip. I can't find many more ways to pull weight off the car, so I may have to look for other methods (stickier tires, steering geometry changes, etc). I'll be starting another thread regarding Ackerman geometries pluses and minuses. I can move the steering rack position pretty easily, but I don't have a sure way to decide which position is best for my situation.
4) And finally aerodynamics. I'm getting down the straights quicker than before, the car feels steady, and the brakes and engine are apparently cooling sufficiently in the process. A problem I ran into repeatedly was the headlights popping up at about 120. I don't have the vacuum system re-hooked up after I pulled out the vacuum tank, so I had to manually close the lights after each session. I don't know if the problem is purely aero pressure getting under the headlights (or maybe entering the headlight opening gap behind the front bumper), or if it's a combination of that and no vacuum in the actuators to help keep the headlights down. I welcome input or suggestions about this issue, as my plans at the moment are to reconnect the vacuum lines and perhaps install a small plastic vacuum canister to compensate for small vacuum leaks in the system

I have seen the pneumatic logic diagrams for the headlights before. It reminds me of an old player piano (only the piano is more understandable). Could you cap the headlight vacuum actuator to lock them in place?

 

[mfain]

Now that we are on the subject, here is an experiment I intend to conduct. I have already built diffuser tunnels between the frame and rocker panels/side skirts. Air is fed to them via the front fender splash panel behind the tire and barge boards along the frame. I built CF plugs for my headlights, which have a fair size cross-sectional area. I made the plugs removable so I could just let air flow into the fender well above the tire. Now I need to build a simple CF upper/rear inner panel inside the fender well just forward of the firewall to smoothly guide air down toward the side pod diffuser entrance. It will be interesting to see if there are any benefits with regard to reduced frontal cross-sectional area or any improvements in downforce as more air is directed into the side pod diffusers...or, it is a total disaster and creates lift instead of downforce.

 

[69427]

I have seen the pneumatic logic diagrams for the headlights before. It reminds me of an old player piano (only the piano is more understandable). Could you cap the headlight vacuum actuator to lock them in place?

At a minimum I need to do that. Right now there's vented (atmospheric) pressure on both sides of the actuator diaphragms, so there's nothing additional trying to help the springs keep the headlights down. I believe I have a non-GM check valve in my hose collection that I can plumb into the carb plenum vacuum and headlight actuators to refresh the vacuum quantity every braking event. IIRC C4s have a small plastic sphere vacuum tank that I could repurpose to compensate for vacuum leakage during the non-braking periods. I'm also going to look to see if it's possible to make a simple linkage to lock the headlights down for track days.

Non-aero amusing story from last weekend's track day. I had a guy stop by where I was parked between sessions (He was driving a Nissan 370Z). He told me that when he first saw my car on the track he thought "Oh hell, another guy with an old Corvette who's going to be driving parade-speed laps and holding everybody up." (To be honest, the first two laps in my first session were of modest speeds while I tried to warm up the engine, brakes, and tires.) He then said "but then when you passed me on the next lap I quickly figured out I was wrong about that".
It's kind of a familiar experience for me. I almost always have the oldest car at any track day, and early in the day it often feels like people think I'm hurting the property values there by my appearance with this antique. But frequently after a couple sessions a couple guys will stop by asking questions why my antique seems to be holding its own out there. I always answer direct questions about what I've done to the car (to be honest, I'm always flattered when someone is curious about my car), but if the guy doesn't ask any questions I generally just let him think it's stock and I'm just brute force horsepowering my way around the track.

 

[69427]

Now that we are on the subject, here is an experiment I intend to conduct. I have already built diffuser tunnels between the frame and rocker panels/side skirts. Air is fed to them via the front fender splash panel behind the tire and barge boards along the frame. I built CF plugs for my headlights, which have a fair size cross-sectional area. I made the plugs removable so I could just let air flow into the fender well above the tire. Now I need to build a simple CF upper/rear inner panel inside the fender well just forward of the firewall to smoothly guide air down toward the side pod diffuser entrance. It will be interesting to see if there are any benefits with regard to reduced frontal cross-sectional area or any improvements in downforce as more air is directed into the side pod diffusers...or, it is a total disaster and creates lift instead of downforce.

View attachment 57593

I'm definitely interested in your results.

 

[phantomjock]

Pappy -
That "jet" you will create will be very interesting. It will be well "disguised" using the headlight as an "intake."
Kind of like the P-51 Mustang oil cooler "jet." Can't say its the same - but similar.
That high speed jet - entering a constricted area, moving into a larger area could generate some Downforce.
Data? Would be nice, but even a butt Dyno is cool too.

Pretty cool mate.

Cheers - jim

 

[69427]

4) DUCT TAPE!!

Or, LeMans buckets might be shallower if using modern rectangular LEDs.​

Then, you could swap the fiberglass covers with lexan and transparent blue mylar.​

Would look "semi" stock." Maybe less weight too. The stock light buckets are pretty heavy - mechanism, etc.​

2) I guess that touch of oversteer is from a throttle "Blip"- or drop?" "...when I ask for it."
I enjoyed "pointing the nose" of the little racer that way. It was a real hoot.

Cheers - Jim

I like the headlight bucket method. I've wanted to replace my flip up headlights with fixed rectangular ones for years. I pulled the whole setup out of a late 80s/early 90s Oldsmobile that used the smaller-than-usual rectangular headlights. I then wanted to cover them and the bucket in easily installed/removable body colored covers for the stock look, but haven't come up with a reliable method for the covers that I'm comfortable with yet.

Years ago I accidentally learned how useful drop-throttle oversteer can be. I was at Mid-Ohio driving a Skip Barber school Formula Ford, and I was coming around the Keyhole in a good clip, and nearing the corner exit I concluded that I'm going too fast and pointing right at the wall outside the corner. I panicked and quickly let off the throttle, ready to hit the brake pedal, when I suddenly remembered the instructor saying "Never lift off the throttle in a corner with these cars.". I immediately reversed course and got back on the throttle. In that half second of letting off and getting right back on the throttle, the rear of the car jumped a foot or two outward on the corner, and suddenly I was staring right down the back straight, instead of to the outside fence. After learning that "skill", I've used it a hundred times in autocrosses, a few times on public roads, and once in a while on track days. It is definitely a hoot.

 

[phantomjock]

I like the headlight bucket method. I've wanted to replace my flip up headlights with fixed rectangular ones for years. I pulled the whole setup out of a late 80s/early 90s Oldsmobile that used the smaller-than-usual rectangular headlights. I then wanted to cover them and the bucket in easily installed/removable body colored covers for the stock look, but haven't come up with a reliable method for the covers that I'm comfortable with yet.

Years ago I accidentally learned how useful drop-throttle oversteer can be. I was at Mid-Ohio driving a Skip Barber school Formula Ford, and I was coming around the Keyhole in a good clip, and nearing the corner exit I concluded that I'm going too fast and pointing right at the wall outside the corner. I panicked and quickly let off the throttle, ready to hit the brake pedal, when I suddenly remembered the instructor saying "Never lift off the throttle in a corner with these cars.". I immediately reversed course and got back on the throttle. In that half second of letting off and getting right back on the throttle, the rear of the car jumped a foot or two outward on the corner, and suddenly I was staring right down the back straight, instead of to the outside fence. After learning that "skill", I've used it a hundred times in autocrosses, a few times on public roads, and once in a while on track days. It is definitely a hoot.

I recall that being referred to as "Technique" - not "Procedure" in flight school.
It is a very useful skill to keep in your tool kit! The best ones are FUN too!

Cheers - Jim

 

[mfain]

Finally finished the front undertray for my C-1 track car. Bought some rubber strakes for a '23 Corvette Z06/Z07 and cut them up to help guide air to a couple of the diffuser tunnels. The front tunnels empty outside of barge boards that guide the air toward the outboard side pod diffuser tunnels. The front splitter extension is from a Viper ACR.

 

[phantomjock]

Looks great - Showroom Quality! Hope it hols up to some track time.
I guess the extension is "replaceable"?

Again - inspirational Pappy. Thanks.

Cheers - Jim

 

[mfain]

Thanks Jim. It is Kevlar on bottom for scrape resistance, foam core, and carbon fiber on top. Should be plenty strong. Yes, the splitter extension is removable. It can be replaced with any extension made for the Viper ACR. I have 3 different widths and materials, and I am building another (Kevlar/CF) with integral end fences.

 

[BBShark]

Nicely done , as usual! The replaceable Viper splitter extension is a great idea.

 

[rtj]

More parts collections for a day when I have more time. Got two of these universal splitters for $50 each off FB. Apparently a customer ordered them and changed his mind. They sat on the shelf a while as shipping label was 2012.
They go for $350 ea now. Look like fiberglass backed carbon fiber. Pretty flimsy, so looking for honeycomb to stiffen them up.

 

[rtj]

Duntov has a new page, and lots of interesting photos. Link below.

This diffuser looks pretty functional, nice gradual transition.



Link



https://duntovclassics.com/duntov-racing/

 

[rtj]

I was looking around and found APR has a “garage sale” page. Seems to be 30% off or better.



https://shop.aprperformance.com/collections/garage-sale


I was a bit shocked to see the swan mount wing I picked up for $1000, is priced at 3400. Apparently, they charge $1000 for the supports. Wing is $2500 approximately.