Side skirts for aero gains

[bryant]

im working with a maverick. its used for daily driver use, drag racing, and has done 2 silver state classic challenges and will do more. first time their was no aero mods on the car and driver complained about hood flaping at speed and the car not feeling planted in the turns. second time i put on a front air dam and that stopped the hood flapping and the front end felt planted. the driver did say the rear end felt a little wishy washy. now the first run the trunk was full of luggage and tools where on the second run it was empty.

so im looking at a rear diffuser but the underside of the car is very messy with exhaust pipes and the rear axle. so to my question.
would side skirts help over come the messy underbody and allow a diffuser to be effective?

also if using side skirts should they be located along the outer edge of the rocker or inboard inline with the inside edge of the tires? or maybe both with a channel or boxed in?

[Bryce]

sounds like a cool project.

I would run the skirts as wide as the body or at least as wide as the outside of the tire.

The diffuser is functional at helping the air under the car get from under the car and rejoin the air going over the top of the car. The rear diffuser usually has about a 10* rake up in the back. and as far forward as possible.

Post some pics!

[bryant]

ive been following your falcon thread. amazing car. im in san diego also. im building a 71 comet that i plan autocrossing when its done.

heres some pics of the maverick.
this is the 2011 SSCC first time.
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here it is at the 2012 SSCC with the air dam in the same area.
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you can see how the hood was lifting in the first year and it was sucked down with the air dam.

[Bryce]

you can also see the front ride height is lower with the airdam.

Cool projects, let me know if you need anything. I am always willing to help out the ford guys.

[Bryce]

come out to an SCCA event, we had 9 muscle cars last weekend.

[bryant]

thanks for the offer of the help. i have some questions about shoulder bolts that ill be asking you about when the time comes. ill come down to the next autocross and introduce myself to you.
i know how to make cars go straight as fast as possible but the turning thing is relatively new to me.

the front of the car has coil overs. the springs were brand new the first time at SSCC. the second time they were a year old. im pretty sure the ride height setting was about 3/4" lower the second year. im also sure that the front air dam did create substantially more downforce at speed than with out. i dont have all the info to determine the amount of down force developed.

my question of the side skirts has me questioning the working theory of the skirts. i know the idea is to channel the air that gets under the car out the rear. also that a diffuser will lower the pressure of the air as it flows out the rear.
my thinking is that if the skirts are along the outer edge of the car, the air will expand into the skirts creating a low pressure under the center of the car which sounds like a good thing. then it will be squeezed when it gets to the mufflers then tires and differential before it enters the diffuser and expands again. i wonder if the skirts or even a second set of skirts going along the inside of the tire will create a channel to help maintain the consistent pressure or flow under the car till it can reach the rear diffuser. i do understand that the underside of this car is very messy but thats another thing to discuss and work on.

[Ron Sutton]

There is a lot more to this.

I have "some" real world knowledge of aero. How many guys would like to start an in-depth discussion of what happens with air flow, goals to improve downforce & the tools to do so?

[NOT A TA]

There is a lot more to this.

I have "some" real world knowledge of aero. How many guys would like to start an in-depth discussion of what happens with air flow, goals to improve downforce & the tools to do so?

I'm in! Currently working on Aero mods for my 70 Firebird.

[GrabberGT]

There is a lot more to this.

I have "some" real world knowledge of aero. How many guys would like to start an in-depth discussion of what happens with air flow, goals to improve downforce & the tools to do so?

I cant believe you even asked. Hells yeah! lol

[bryant]

I definitely would like to be involved in a discussion like this. I've searched the net and this site and found snippets of info that are extremely informative and helpful but noting that talks a about how every area effects each other and the tools to accomplish the end goals.

I think generalized body types need to be separately addressed. My maverick body has similar problems to overcome as 60s camaro's and mustangs, but not much with 80s and 90s cars. I look forward to a well laid out discussion on this

[Motorcitydak]

If you plan on skirts and a diffuser, also plan on full belly pan to completely take advantage of all your low pressure under the car

Another really good aero mod that I have planned is a lexan rear window with scallop style vents placed into it. The rear window is a big area of negative pressure which slows the car down and also lifts the rear end slightly. If you run with your windows down, it will have a torrent of air coming out of the rear window. Check out pictures of the Ferrari F-40's rear window/engine cover

[bryant]

i havent really considered the rear window area yet. that makes sense that it would be a low pressure area. the rear window mod wouldnt be practical on this car as it needs to be watertight for daily driver use.
i suspect this low pressure area is what feeds the spoiler or rear wing, or the rear wing or spoiler are used to off set or correct for the low pressure generated by the sloped rear window.

rear wing and or spoiler is another area that ive got questions about.
i dont like the looks of a wing on stands on the trunk lid. i like a spoiler like the grabber style spoiler or one like a pro stock rear wing. the size of the spoiler will depend on the planned speeds. i would expect to have one that is just used for SSCC and then a different one for autocross and just spirited street driving.
any suggestions on what to use?
also is their a way to figure out what spoiler will be effective at 160mph? thats the to tech speed that the maverick will be able to do next.

[Damn True]

If you plan on skirts and a diffuser, also plan on full belly pan to completely take advantage of all your low pressure under the car

Another really good aero mod that I have planned is a lexan rear window with scallop style vents placed into it. The rear window is a big area of negative pressure which slows the car down and also lifts the rear end slightly. If you run with your windows down, it will have a torrent of air coming out of the rear window. Check out pictures of the Ferrari F-40's rear window/engine cover


Not always. It depends on the car, but often times the air passing the open windows of the cockpit creates a low pressure environment in the cabin. There are many cars, the Ford FR-500's come to mind, where the cabin pressure is low enough that the rear window bows in.

On some versions of the Porsche 911 this is not the case. On those cars the window must be restrained to keep from being pulled out.

[Ron Sutton]

Guys, I sent a PM to Larry to about setting it up as a tech thread.

[bryant]

Guys, I sent a PM to Larry to about setting it up as a tech thread.

cool. i look forward to this.

[Ron Sutton]

Larry & I discussed a game plan. I'm going to launch a few dedicated Forum Threads dedicated to Track Performance under the Advanced Tech & Performance Discussion category.

I'm going to launch them one at a time ... over time ... in this order.


Designing Aerodynamics for Track Performance
Safety to Match for Track Performance
Engineering Brakes for Track Performance
Building Engines for Track Performance


Then we'll have a dedicated spot that covers all the fundamentals first, then allows to discuss specific situations there.

I'll be back here to post a link once I have it the fundamentals of Designing Aerodynamics for Track Performance done.

[GrabberGT]

Checked your page to see if you had a book out and nothing. I may print all your info off and make my own binder. Between this and the suspension tech you have provided previously, we have a fairly comprehensive guide to making anything into a race car.

[UNGN]

When you see the hood lifting off like in the first pictures, the front end is generating lift. Maybe the springs settled to increase the rake, and lower the lift, but It looks like the airdam is most definately helping reduce the lift, by lowering the underhood pressure.

I am a big fan of airdams for reducing front end lift. You can only go so low under the front bumper and still have a practical street car, so we put a conveyor belt rubber one under the radiator support, lower than the headers and the exhaust.

What Class did you run at Silver State?

[Z06killinSBF]

Very interesting subject, I'm tuned in!

[bryant]

this is a good friends car that im the mechanic, crew chief, and voice of reason on. the car ran in the 105 class in 2011 with an average of 105.335 and in the 125 class in 2012 with an average of 124.9101. it wont make it there this year.

great to hear about the new dedicated threads. im looking forward to trying to digest the knowledge that will be revealed.

[Rod]

Designing Aerodynamics for Track Performance
Safety to Match for Track Performance
Engineering Brakes for Track Performance
Building Engines for Track Performance




you forgot one so I added it

5) Understanding all this stuff for dummy's!

that's my section

[Ron Sutton]

Checked your page to see if you had a book out and nothing. I may print all your info off and make my own binder. Between this and the suspension tech you have provided previously, we have a fairly comprehensive guide to making anything into a race car.

Thanks for the good words. I'm writing a series of "car guy" books on suspension, chassis, engines, brakes, etc. First one will be out early 2014.

[Ron Sutton]

you forgot one so I added it

5) Understanding all this stuff for dummy's!

that's my section

You're funny. I saw your Camaro at GG on Saturday, but didn't see you around it.

[UNGN]

this is a good friends car that im the mechanic, crew chief, and voice of reason on. the car ran in the 105 class in 2011 with an average of 105.335 and in the 125 class in 2012 with an average of 124.9101. it wont make it there this year.The "20 mph Faster average" pictures look good. It looks like the car could tech for the faster speed classes. Silver State is kind of a snooze until the 150 mph classes, but if you ever come east, the Big Bend Open Road Race is way more fun, with lots of curves and elevation changes.

[Rod]

You're funny. I saw your Camaro at GG on Saturday, but didn't see you around it.



She has a life of her own Saturday she was at Goodguys Pleasanton in the Jet Hot booth and Sunday we were at Sonoma for the Grand Prix! I'm always just along for the ride
https://static1.pt-content.com/images/pt/2013/08/GEDC1187_zpsb84a559f-1.jpg

[bryant]

The "20 mph Faster average" pictures look good. It looks like the car could tech for the faster speed classes. Silver State is kind of a snooze until the 150 mph classes, but if you ever come east, the Big Bend Open Road Race is way more fun, with lots of curves and elevation changes.

i would love to come out to the Big Bend Open Road Race. its something that is on the bucket list. so far its baby steps on knocking things off the list. i want to so some standing mile stuff, road race courses, autocrosses, still dragrace, and what ever other auto performance stuff i come across.

[Ron Sutton]

Writing up all the stuff in my head is taking longer than I thought ... but I'm getting close guys.

I'll post a link here when I get the new "Designing Aerodynamics for Track Performance" thread up.

[Ron Sutton]

Writing up all the stuff in my head is taking longer than I thought ... but I'm getting close guys.

I'll post a link here when I get the new "Designing Aerodynamics for Track Performance" thread up.

[Ron Sutton]

OK ... the new dedicated aerodynamics forum thread is up !

The title is "Designing Aerodynamics for Track Performance"
It is in the Advanced Tech & Performance Discussion section

Here is the link (https://www.pro-touring.com/cars-general-technical/advanced-technical-performance/designing-aerodynamics-track-performance-101460.html).

[Zspoiler]

843888438984390 Making a set of side skirts isn't very hard to do. I have 90" aluminum angles and rubber ,and or urethane skirting. Along with a rear spoiler,and wing.and diffuser in back. Nascar,and a number of automotive racing associations use different kind of Aero on their cars. Because it doesn't add much weight to the car for the grip it adds to it. There are a number of books out there that explains it.

[alphaenvirmgt]

I'm in too. Working on 84 Buick Grand National (Regal) and would love some aero mods!!!
Conrad