So trying to do some things to my car to make it more efficient through the air instead of spending more money on go fast parts. Fastest pass thus far is 202.9 in the mile and 213.1 in the 1.5 mile. Being that the car is a FRC and not a hatch I am already at a disadvantage.

One idea is something like this splitter for the front: http://st.hotrod.com/uploads/sites/2...ette-front.jpg

Then there is a rear drag race wing:
https://www.skinnykidracecars.com/sy...5-07-wing2.jpg

Last currently I only have window nets is it worth the cost to do lexan windows?

So what are your thoughts and experiences whats worth the money and whats just crap?

I am already replacing the wheel and tire combo for a taller rear tire currently I am having to shift into 6th at 198mph which is killing my topspeed. With the new setup I should max out at 211 in 5th now.

Thanks for an ideas.

 

I think you're on the right path with both the splitter and the rear deck extension you've listed.

The FRC really is the worse case scenario. If I was trying to make the car faster with less drag, here are my ideas:

1. Windows...yes as those alone may be worth way more mph than you think.

2. Try to make the front fender wheel well extend outwards past the tire as far as possible. Look at both NHRA funny cars and even Nascar front ends, the tire is 3" to 8" inside the edge of the wheel well opening. For a lot of cars that this doesn't make sense (like a Viper ACR) so they use canards. So many people think canards create actual down force but the reality is they direct the air away from the tire and wheel well opening. The spinning front tire and wheel is extremely disruptive to the airflow down the side of the vehicle. You want the front of the car wider than the rear and smooth airflow to limit drag.

3. I'm not sure if the sharp downward angle of the FRC rear window is long enough to work with this, but I'd recommend running some small vortex generators along the back edge of the roof line to help pull the air down onto the rear deck quicker and keep that giant area of upset air behind the rear window to a minimum.

4. A few vortex generators along the B billar behind the doors windows may also help pull the disturbed air back onto the trunk lid where it can re-attach onto the rear deck spoiler you linked to above.

5. Vertical fins on each side of the roof and down onto the rear deck will keep the air on top of the car and not allow it roll off and down the sides of the car. (look at the roofs and rear decks of Nascar, sometimes hard to see because they use clear plastic fins down the window and rear deck). You want to have the vertical "fins" on both sides of the vehicle (maybe along the trunk opening seam). Air spilling down the sides of the car mixes and causes turbulence with the air coming around the front of the car and causes drag.

Ok, that's all I can think of for the moment. Full disclosure, I am not an aerodynamics engineer. Double check all my recommendations before implementing because once you get over 150 mph, the energy of the air can be enormous.

Looks like you've got a good amount of h.p. if you're getting over 200 mph in the mile. Getting your gearing just right so you don't lose a bunch on the shift will make all the difference. Good luck, looking forward to your next update on the results.

 

I too was also going to mention vortex generators on the roof rear because of the FRC. Did you vent the hood? I would also go to narrower front tires. Longer flat spoiler in rear like exaggerated version of the Caravaggio spoiler. Attach Moon discs to your wheels if possible. Some ideas I want to try on my own car. Oh, also you might want to consider a lower numerically rear gear. With the 3.15 gear you might be able to stay in 5th longer.

 

Wow great info guys I appreciate it. I had not thought about the vertical fins and vortex generators.

Right now my current tire and wheel setup sticks past the fenders that is item one on my list to fix.

My rear gear is a 2.92 so hoping that unless I do another 1.5 mile event 5th gear will be all I need. Unless I add a decent amount of more power.

 

a roof extension (maybe out of alumilite?) could mimic the coupes aerodynamics (and maybe improve on them)

sorry for my quality









essentially trying to move towards a look similar to this:

NB miata with normal hard top:



extended hard top:





also some good reading on the benefits of a "long tail" with regards to highspeed stability

http://www.automotiveforums.com/t461...shorttail.html

blackbird fab made a long tail conversion for miatas:

http://www.trackhq.com/forums/f360/f...ck-miata-6456/

 

Thank you for those articles gives me more to think about. Really the FRC is not a good starting point for Aero. Oh well gives me something to do over the winter and test in the Spring. Wish I had a wind tunnel close.

 

Forgot to mention I am running window nets I would assume this is a big speed killer. I was looking to get these and build brackets:
http://www.opticarmorwindows.com/app...urer=Chevrolet

 

That's fast!
I did 167 in my nearly stock C5 and I felt like she was starting to "float". What are you using for down force?
How much HP are you putting down?
I would think windows would help.

 

Honestly it feels pretty stable at those speeds but I also have a deathgrip on the wheel so there is that. At this point the car is totally stock nothing has been added for down force.

I put down 600rwhp on motor and 800rwhp with nitrous. On motor alone I can do about 188mph in the mile with good conditions.

 

Sweet Jesus, 200 mph on a 2 lane road, totally cool

 

Venting the hood would do a lot for reducing drag as well as reducing front end lift. The body side moulding (BSM) apparently also helps with aero at high speeds (proven in wind tunnel testing). That's it for the ideas I have.
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Ha yep after running on a 2 lane highway going 200+ on a runway seems far less intimidating.

 

I have been wondering if venting the hood would help. Not only for lift but when I tape the seams I cannot open the hood and it gets pretty steamy.

And damn of course I removed the body side moldings for a cleaner look but go figure that was a mistake.

 

Now that I see our car here are a couple more things to try.

-Lower the car a little, preferably with a slight nose down rake

-Tape closed the grill openings if it doesn't effect air cleaner intake. Looks like your car is still a bottom feeder for radiator cooling so the front grills aren't keeping it cool.

-Rocker panel side sill extensions to keep the air from rolling down the sides and under the car, usually sticking out further in the front half (behind the front tire) than the rear.

-I'm not a 100% sure venting the hood is going to help with aero dynamic drag at the speeds your running. It might actually create more drag due to the under hood air interrupting the air flow and pressure already there. It looks like you've spent a fair amount on this project, since it is so easy to swap C5 hoods it might be worth trying one vented at an event and swapping back to stock if it slows you down. Grab a hood off Craigslist, vent it and bring it with you to the next event....only way to really know.

 

Hood venting should work as long as you open it too far back. Just behind the radiator should work. I'd like to try those Trackspec vent grills.

 

Good ideas thanks. I keep forgetting about those rear brake ducts. As for the hood I agree it makes sense to just get another one and do some testing. I have a feeling a lot of this will be trial and error. As for the tires I agree on the rake looking at either 315/35/19 on the rear or a 315/40/18 both will give me a 1.2 inches more than current. Then a 285/30/18 which is 2.4 inches shorter than the new rears. Or is that too drastic of a change?

 

If I'm understanding your numbers, that is nearly a 2" difference. That might be a lot....maybe be safer to take baby steps. Also, lowering the car using raised spindles will help close up the tire fender gap for better aerodynamics yet keep your suspension from bottoming out. 90% of all of this is only going to matter once you get over 160 mph and at that speed there is a lot of energy acting on the car. I recommend small changes so you don't get any surprises that are out of your control. Too much rake might cause instability side to side under braking or side winds. I'm not 100% sure as there are many things that are in play here (like tire sidewall height, sidewall stiffness, air pressure, spring rate, shock dampening, etc).

 

No, totally stupid!

 

Thanks I was thinking that rake was pretty crazy as well. At the moment it is pretty stable so don't want to ruin a good think.

 

LOL yeah its not the safest not gonna lie. Thats why I bought a car with the best cage I could find. Granted at those speeds not much is gonna help but its something. I would much rather do more of the airstrip events IE Texas, Arkansas and Colorado but just so far away.