What mods would need to be done to increase high speed stability?

xj220

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Sep 15, 2000
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This is something I've been thinking of lately. What would need to be done to our cars to make them stable at high speeds (100+ mph)? Obviously suspension work, a bump steer kit, but what else? I'm thinking along the lines of autobahn cruising here. I know our cars aren't designed for that stuff, but what would it take to get them close?
 
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Large brakes front and back. lowered ride height with very stiff springs and shocks. good swaybars front and back. light weight forged wheels. good alignment. speed rated radials.. Oil cooler for engine, trans and rear axle. heavy duty cooling system. Maybe a chin spoiler and rear diffuser. small bullit mirrors.. Hood pins front and back...
 
Limiting air through the grill will help. Any air going in at the front of the car ends up under it. A radiator only needs an opening about 1/3 the size of the core. Any more is unneccessary. A chin spoiler lowers the point in which air goes over the car instead of under the car. Air extractor on the hood will remove air from the engine bay and keep it out from under the car. Air can get under the car from the area at the base of the windshield. This is a high pressure area meaning it is good for the carb, but any air allowed to get under the hood is pushed under the car. The less air that can get under the car, the lower the pressure under car. Lift is caused by air pressure below the car being higher than the air pressure over the car. Watch Nascar on Sunday, they use very small openings in the front. I also read that during developement of the new ZO6, the brake cooling ducts were reduced in size as much as possible to reduce lift at speed. Whatcha got in mind?
 
xj220 said:
This is something I've been thinking of lately. What would need to be done to our cars to make them stable at high speeds (100+ mph)? Obviously suspension work, a bump steer kit, but what else? I'm thinking along the lines of autobahn cruising here. I know our cars aren't designed for that stuff, but what would it take to get them close?

No bump steer kit needed and spending high dollars not necessary.

Get the car low, block off unused portion of front grill, 750# fronts, 5 leaf rears, plexi rear glass to let air out, bias ply's and oh yes some big you know whats. Want a pic at 145?

HistoricMustang
www.historicmustang.com/tech.html

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Would air extractors in the front fenders help? Like the ones on the late '70's TA Firebirds? They would have to be lower than the TA's because of the crease along the side of the Mustang fender. I saw a set on a '70 Ranchero, they actually looked pretty good. Would they make a material difference in under hood air pressure?
 
You would have to cut holes in the inner fenders, below the hood hinges, to get air from under the hood to the outer fender. One problem is that there is a high pressure area behind the front wheel. Shelby Cobras used extractors behind the front wheels as do many others. I'm not sure if they were for underhood or fender opening vents.
 
Unique Performance cut slots in the back of the engine bay on the GT350SR to help exhaust under hood positive pressure. The air excapes through the cowl. - http://www.uniqueperformance.com/GT350SR.aspx - pictures 5 and 6.

Another way is to limit the amount of air flow into the engine compartment. Here is a link to an air foil that eliminates any air into the engine compartment except what passes through the radiator - http://jmichael.info/docsairfoil.htm
 
65 fastback said:
Another way is to limit the amount of air flow into the engine compartment. Here is a link to an air foil that eliminates any air into the engine compartment except what passes through the radiator - http://jmichael.info/docsairfoil.htm

Here is how mine is blocked off. The only air entering front of car is through the radiator. Other sections of the grill have plexi glass and black duct tape. Below the grill is white duct tape sealing off headlight buckets, bottom of grill, etc. Back of hood is raised approximately 1/2 inch to let any air escape. I also have a cowl between the grill and radiator.

At Daytona the entire grill is blocked off. Only air entering the front of the car is through the opening in Shelby apron. This air enters the above mentioned cowl area and is forced through the radiator.

Also, keep in mind the car is lowered 2 1/2 to 3 inches.

HistoricMustang
www.historicmustang.com/tech.html

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Venting air out of the back of the hood is not one of the better places to do it. Air tumbles as it hits the windshield and it forces over the roof, and causes a HIGH pressure area at the cowl area. This makes a bad area to pull air from under the hood. A cowl hood or spacing the back of the hood will extract air because of the venturi effect, but because it is a high pressure area it is not as effective. Another thing that can reduce the venturi effect is the loss of laminar flow caused by the tumbling air at the cowl area. The vents on a Mustang are taking air from the cowl and I was very suprised at how much air is coming out of them at 50 mph. The reason Ford connects vent to this area is a natural high pressure area that forces air into the interior. The area around 1/3 of the way back on the hood is the area best suited for removing air since it is the area of lowest pressure. Look at the 67-8 turn signal hoods or the 03-4 Cobras. They both used this area to remove air. They current Shelby Cobras also have an extractor in the same location.