chin spoiler

 

what course are late model Mustangs back flipping on?

way back when, I buried the speedo on my 67 Mustang coupe , swapped in CJ, the front got very light and a "normal" freeway left turn took me from the left lane to right shoulder. I had a chin spoiler,Shelby Drop, 70 CJ front springs cut about 2 coils,stock rear springs and Koni Shocks.

 

what course are late model Mustangs back flipping on?

Pacific Raceways, turn 1. DO NOT LIFT. It's better now that they repaved it, but along with a slight jig right, it drops off at about a 45* angle. A good friend of mine rolled his '08 Shelby GT there...lifted slightly, weight transferred...voila. It's one of the first things any instructor will tell you about the track.:skullnbones:

 

Biggest improvement in aerodynamcs is to cut holes in the fenders. Cut some NASA style HOLES IN THE FENDER back side even with the inner fender splash shield tappered forward in the upper side portion of the fender.

Cowl hoods can increase front end lift as air near the edge of the glass cowl push air into the engine compartment. Same with raising the back of the hood but raising the hood air trapped in the engine compartment can excape out the side gap along the fender.
Found raising the hood then duct tapoed between back of hood and cowel helped the most.
These changes made one of my mustangs increased economy, increased weight on front wheels at speed, almost completely eliminated hydroplaning in 2" and better of standing water.

 

Do you have any pics of these fender holes? Or links?

I'm trying to wrap my head around all this. Would the forward-facing scoop be redirecting air down under the car (causing the lift)? If I'm following your suggestion of sealing off the back of the cowl, would taking the scoop off actually make the lifting worse, ie more air escaping up?

I guess it's kinda guesswork, with each car different from the next. :-/

 

hAVE TO TAKE SOME PICS as the one i DID IT TO pics are stuck on a burned up hard drive.

 

I started getting into aerodynamics after reading an article based on the old big caddys. They did a study about how much weight was on the front wheels going down the road at 60 70 MPH. Back in the day one wold see them with the front a 1' or 2 higher in the front. Simply this translated into static front end wt around 2800 lbs at 60 70 wt on front wheels calculated to 500 600 lbs
After mods to the 68 the front ended up feeling much heavier

NASA style opening dipected. Arrows show basicly how the air flows around raised hood. were it shows air going back under the hood is were I ran some duct tape. Retangle shows a good area mabe to cut louvers have also thought about using boat hull vents some look a lot like the old hood vent looking one s on the cameros. The NASA duct did the most AS STATED THE BACK SIDE CLOSEST TO EVEN WITH THE INNER fender guard. This allowed me to do like 70 through a 10 mile strech of 2"s of standing water were I could only do 25 to 35 safely before the NASA duct.
Also found the front of the vehicle about an 1" lower than the front worked best also but by far the aboved mention mods did the most

 

Hmmm. Not really willing to make cuts in the fenders and hood...I'd rather replace the hood, and I don't have the budget to do so at this time.

So if the rear of my car is 1-1/2" higher in the rear than the front, as measured at the ends of the pinch weld, I should leave it as-is? And just add the chin spoiler for more downforce? Or would that be TOO much downforce?

I wish I had a test day to try out variations. :-/

 

If the hood is raised as mentioned then suggest running some duct tape across the rear opening were the cowel vent slits are as this is were aire is forced back under the hood. How close to the corners of the hood is needed varries somewhat depending on the vehicle. I did do string testing on this along the edges of the hood but on my stang was years ago and was totaled around 79 or 80.

Chin spoiler helps but also ads wind restance to some extent. What I DID WAS IN EFFET REDUCE FRONTAL AREA. The newer cars with the tires so close to the door NASCAR has found attemting to exit air in front of the tire instead of behind helps bust not as well as behind.

 

Maintaining some rake is important from what I know, unless you have a ton of aero and that component is calculated in the spring rates and valving etc (read real race cars).

Getting air out from under the hood helps a ton, via venting routes. With a functional and sealed air scoop, you could duct the air through the radiator and out of the back of the hood, keeping pressures down under it, akin to what turbo has shown. Via vents in the hood or fenders, raising the rear of the hood slightly etc. The chin spoiler will add some downforce, but it also adds more air under the hood. Someone here with way more knowledge about it will chime in I am sure.

Google the string test I think, which involves cameras and a bunch of taped on stringers to show where and how air is traveling around your car at speed to see where you can best utilize it.

 

Well I'm no aerodynamicist but I did stay at a holiday inn last night...

Chin spoiler keeps air from going under the car which creates lift/instability

Your hood scoop is likely in "dead" air, or the boundary layer on the hood

 

One of things I thought about, front springs. With the stock, soft and long springs there is a lot of stored energy to lift the front. I was wondering if a shorter, stiffer spring would help since it won't have the same amount of energy and help keep the front down. Maybe turbo2256b can comment on that, he's a pretty sharp guy.

 

I run 720 lb rate springs in the front of my 200 or 250 I 6s rear springs are 68 390 compitition springs with the trunk mtd battery that was an option.
Mods to rear springs rear hanger should be facing rearward at the bottom usally requires aftermarket rear hangers using the 2 closest holes. I then remove all clamps on he rear portion of the leafs (behind axle). Then clamp all leafs in front of the axle.
The 720 springs are cut down 69 70 ish front springs for a 429/460 torino. one coil removed.

This set up with 275 50s on the front and 295 50s on the rear nothing could catch me around a corner except mabe a unlimited go cart.

 

Here are some of the marine vents I have thought about installing on hoods in the retangular area I MARKED.

ATTWOOD Venturi Vents | West Marine

 

It sounds like the cause of the crash you described had less to do with aerodynamics and more to do with some less than stellar driving and poorly timed weight transfer.

I would keep the rake that you have (slightly higher in the rear). A chin spoiler could help, as could raising the rear of your hood slightly.

 

I just watched a few Youtubes of crashes at PR , and I would say you are 100%correct,cresting the hill causes the suspension to rebound at the point you need more grip on the front.

OP if your car wants to loose the front there some (very) good shocks are in your future to control the rebound.

 

Front springs are the 620 Grab a Trak. The car has the full TCP subframe/x-brace package with a Fays2 Watts link and is generally very stiff. Typically, the car has a rake until I approach ~90 mph, then it sits level. At 100mph+, it still appears level (from photos), but I just get that "feeling" of it lifting in front. Mind you, I'm limited to about 5 seconds at this speed due to the transmission/rear end ratio, but still.

I've read about the string test, and that's why I was wishing for access to a test track.

What I'm reading about is that a 1-2* rake is desirable, and that the addition of a chin spoiler, while adding drag, more than compensates that amount of drag by adding downforce. I don't see how I can really make a difference in drag elsewhere without adding a rear splitter of some sort. And that's getting into $$$. I'm more concerned with the front end lifting.

 

And stupid question: How would I lift the rear of the hood? Add a shim in between the hinges and the hood?

 

Hey Sparky,
That transition at Pacific pulls a lot of folks into the wall, listen to your instructor and do what he says...you'll be fine. Edit: my bad, T-9 will cause problems also!

Cheap aero...If it were me I'd be looking at a chin spoiler and a spare "track hood". I'd hit up your local wrecking yard and look at vents from some of the 80's and 90's imports and cut them into your spare hood.

I've found the biggest improvements in aero are keeping the air out from under the car (which causes lift) and relieving the engine bay of incoming air. The spoiler does cause drag but the benefits of eliminating the pressure under the car out way the drag from the spoiler.....think about all the "hang ups" that cause drag under the car, control arms, exhaust, rear axle....

While not an early mustang, I picked up 3mph at Bonneville by cleaning up my aero, free horsepower!

:thumbsup:

 

Thanks Dbasher, exactly what I'm leaning towards.

BTW, that friend that I mentioned earlier is my coach at that track. He now races an E30 race car.

The spare hood is an EXCELLENT idea. I doubt any wrecking yards around here have any first gens, but I do know a guy that restores them, so he's bound to have one eventually . I'm thinking along the lines of the New Edge Mustang heat extractor hoods - the vents are behind the "scoop" if you will, near the cowl.

 

As we have thrown out the idea of a track hood, how about rear trunk lid too? Lift/snap over steer is going to ask for more rear traction and not more front end bite. It must be balanced! I must concur that this turn is more weight transfer than aero.....but your straight away lift that you are complaining is certainly the aero brick your driving.

Clearing air out of engine bay without shoving it under you is going to help. You need air flow to cool but you need to clear this too. If you open can funnel this appropriately you can achieve benefits in both. On these old Mustangs with NO aero attention done to underside, I don't think the increase in frontal area vs possible lowering of cd is going to be a net loss. The Trans Am guys, though 40 years ago, were pretty sharp. The vintage racers of today are VERY sharp. Just copy them within reason. They are pretty fast for what they are given as a palate.

I don't think an air dam is even a question. I also think experimenting with a cheap trunk lid with an adjustable rear spoiler for height or a deck lid with wing and adjustable wickerbill/Gurney to dial in balance is worth thought when discussing aero balance. Many a Porsche 911 has met its end to aero inbalance as they are like trying to get a "wing" to not fly.

 

Sparky, just put a "want" in classifieds. If you weren't across country I could give you one from previous restorations.

 

Small world, I've reconnected with an old high school friend that does the same, he's now moved into the new class. C. Hurley, hell of a wheel man!

Keep your eyes peeled on Craigslist for a hood, I've seen a few that would be perfect for this kind of set up go for cheap.

See you at the track!

 

I lifted the rear of the hood by loosining the hood hinges and pulling them as far upward as possible then added spacers between were hood and the hinge bot togeather. Taller spacer at the rear. Had to do some hood latch adjustments too I THINK.

mY 69 Shelbey GT 350 got realy sweet after lowering the front about an inch. Think that front bumper acted a bit like a spoiler and the rear vent holes in the rear of the hood helped also. At speeds around 90 and above the car would settle downwards about an inch or so and stay that way even at 200 MPH.

 

When mine started to try and fly on the drag strip I lowered the rear 2 inches and the front 3 through a combination of springs and tires. Tucking the tires up in the fenders helps quite a bit. The rake angle puts down force on the hood also. Once the car rises up to level, the hood on these cars acts like a sail.

Put a thin plate(aluminum) between the grill and the radiator support also to keep air from running up in there.
You can see what they do on the trans am cars;

Do something along the lines of this;

I haven't had to fab up one of these yet.

 

Do something along the lines of this;

That car's had a nose drop to look like that.

 

Okay, now that's just sexy. I don't even think I care if it works or not. I just want it.

 

I agree that the Trans Am guys had a lot figured out, and the current serious Vintage guys have modernized that path, copying what they are doing will certainly put you on the right path.

If you have a sufficient cooling system during track use, you could start experimenting with limiting the air incoming through the radiator, in conjunction with the chin spoiler (to clean up air below the car) to help minimize the air coming in under the hood and reduce the "sail" effect. The backup hood, along with the rear spoiler/spare truck lid sounds like a good option. In the future once I get lots of other things sorted out, I will be sourcing a functional hood scoop and a spare trunk lid that will have a spoiler/foil on it for autox and track use.

Another thing to check out are all of the high dollar classic pony cars that are playing in the Ultimate Street car series .... tons of aero and venting getting added in to vintage bodies to try and keep up with the aero, cd, and tech assist advantages that the modern cars have (C5/C6 vettes, 5th gen Camaro, Mustangs, and GTr's)

Thanks for all of the replies on here, good info

 

Agreed - MUCH thanks for all the info!!

And that '70 is PERFECT. Seriously. I need a tissue.

I don't have any cooling issues, even in hot/humid traffic. I USED to, but since I added the flex fan, shroud, Water Wetter, and lower valance cut-out ala R model valance, no probs whatsoever. BUT I had an inkling that the hood was acting like a sail...you'd think my first clue would've been that one time before hood pins and it DID sail up . This was at 38mph. It did a number on my original hood, hinges, and inner aprons.

Funny you would mention OUSCI, as I was all set to do the weekend in Portland in July...until they released the schedule for 2015. Nothing in Portland, just Thunderhill at the end of February. Siskyous in February? No thank you. Killed my whole year, as that's EXACTLY the kind of stuff I love to do with my car. And what it's being set up for :crybaby:. I saw all the final competitors at SEMA, and while a lot of them *were* very high dollar builds, a lot were not. But it was interesting to see their setups at the very least.

 

Three playing fields in USCAI, the purpose built, just write the check approach owner, the long time non pro racers with some sponsorship, and the Company cars built to sell products.

There is another class of the more grassroots build on a realistic budget, that the TV show likes to highlight. The reality is, you don't win without being in a full built race car with carpet and lights installed, and a serious wheel at the helm.

 

I'm not looking to win anything. I just want to be better than the guy who's in last place...just a dumb girl in her 50 year old secretary car lol.

Thunderhill was a blast! And the Siskyous....where have you been all winter? Not a drop of the white stuff anywhere!

Sparky it sounds like we're headed in the same direction. I'm looking at running Pacific and the Ridge as well as Bremerton...you've got a head start as I'm still putting my junk together. Hopefully I'll be on the road by the end of April and signed up for HPDE shortly after.

:thumbsup:

Ugh. It was too much of a gamble, and really too far for us. I'm trying to lobby them to bring it back to PIR next year!!! There's a HPDE at The Ridge 5/7 with Hooked on Driving that I'm going to - maybe swing by at the least, say hi, and hitch a ride!

 

Thunderhill was a blast! And the Siskyous....where have you been all winter? Not a drop of the white stuff anywhere!

Sparky it sounds like we're headed in the same direction. I'm looking at running Pacific and the Ridge as well as Bremerton...you've got a head start as I'm still putting my junk together. Hopefully I'll be on the road by the end of April and signed up for HPDE shortly after.

:thumbsup:

 

Portland was.....not very successful last year. We joked that at least everyone finished in the top 20, hard to run this kind of program with low numbers.
I did hear some chitter chatter at Thunderhill about Oregon Raceway Park, I've never been but it is a bit closer.

:thumbsup:

 

Could've been that, at least around here, I was the only one in my circle of track friends that even *knew* about the series. Thunderhill adds another 2 total days of travel - and expenses - for me.

I guess my biggest gripe was, if you're going to move it south to CA, move it later in the year (so we don't have to worry about little things like towing in the mountains in winter).