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This picture shows the drivers side duct off the car. Not much to see with all of it covered with black duct tape. From left to right is the 5 inch to 4 inch reducer (item # 1), the aluminum four inch duct (item # 3), PVC Pipe coupling (item # 4, hidden by duct tape), three-way adjustable elbows (item # 5, also hidden by duct tape) and finally the high temperature brake duct. NOTE: You notice the 3 way adjustable elbow is almost adjusted to 80 degrees. It had to be adjusted to this angle to prevent it from being hit by the wheel / tire. Also you will notice the orange high temperature duct is cut at an angle. This is to allow the duct end to fit as close to the rotor center as possible.
This is the view from the front of the car. You can see the three and nine o’clock bolts (item # 2) that firmly hold the 5 to 4 reducer (item # 1) to the fog light hole. You can also see the reflection of the inside of the aluminum duct. When this picture was taken the duct was angling down as the other end of the duct was on the driveway. With everything in place it is a straight shot back to the right angle to the rotor. With only one turn I think I am getting good airflow to the rotors. You can also see my fabricated wrap-around 3.5-inch air damn; this replaces the cheesy air deflector under the Mustang. If anyone is interested in how to build one of these for a SN95 Mustang please e-mail at the e-mail address below.
This shows how the other end of the duct is attached to the chassis. You can see the big screw hose clamp (item # 8) securing the duct to the sway bar mount. Remember inside the duct at this point is the PVC pipe coupling (item # 4). This allows you to tighten this clamp as tight as you wish.
This shows the end of the duct. Here you can see the angle of the duct end. You can also see the zip tie holding the end of the duct to the coil-overs. In this photo the wheel is turned full lock left. Information by Ran Shan (RSSS96962@MSN.Com) Step-by-Step & Part Numbers for FOUR inch Brake Cooling Ducts After a number of brake cooling duct failures I have finally designed a reliable way to duct a great deal of cooling air to the front brake rotors. The car (97 Mustang Cobra) is a weekend car that is also used for 3 to 4 track events per year with both my wife Sally (Track nick-name Mustang Sally) and I driving. With both of use driving, brake heat is something that needs managing.
At open track events a number of people have asked where I purchased my brake cooling duct kit. Finally I was asked if I would e-mail to them a short description. The next time I was at Home Depot I jotted the part numbers and cost down. Below is how to put a four-inch brake cooling duct system together.
The set up is so reliable that now I leave the brake cooling ducts on the car all the time. The main duct is FOUR inch in diameter rather than the normal three-inch ducts. My engineering friend tells me a four-inch duct carries roughly 78 percent more air than a three-inch duct.
If you are interested in how he came up with 78% what follows is how he explained this to me. Flow rate = diameter of duct squared. So, a 4 inch duct squared = 16 vs. 3 inches squared = 9, 16 divided by 9 = 1.78). He went into the pie (spelling?) factor and the area of 4 vs. 3 inches, but got over my head pretty quick.
NOTE: Four inched compared to 2.5 inches is 156 % more airflow. (16 vs. 2.5 squared = 6.25, 16 divided by 6.25 = 2.56).
My engineering buddy that gave me the formula also explained, that I did not want the cooling air to pass too fast through the rotors cooling vanes. By going from the 5-inch fog light openings to 4 inches would allow the air to pass through the rotors slower than going from 5-inch fog light openings to 3 inch ducts.
This is for a 97 Mustang Cobra. The only part specific to a Cobra is item #1. Those of you that have 94 to current Cobras have an easy task fitting the duct opening to the car fog light hole.
Below is the parts list, Home Depot part numbers, cost and descriptions.
Parts listed in order of airflow. =========================================================== 1. Two, round galvanized sheet metal air reducers, 5 inch to 4 inch – Home Depot # D100-552, $3.79 each, total of 7.58.
NOTE: This will fit perfectly over the fog light holes in the Mustang Cobra. =========================================================== 2. Four (two for each opening) one inch by .25 inch black hex head black bolts. Nylon locking nuts, flat washers and 1/8 by ¾ inch rubber washers. Estimate $2.00.
INSTRUCTIONS: These hold item # 1 to the fog light openings. Drill two .25-inch holes (I know, it hurts to do this part) (one inch from the leading edge) inside the fog light opening at the 9 and 3 o’clock positions. These will hold item # 1 firmly in place. You will trial fit (from the backside) item # 1 over the fog light openings and then mark the place to drill the .25 inch holes through item # 1. Do not attach the reducer to the fog opening holes at this time.
NOTE: Do not try to use a 4 to 6 inch screw clamps to hold these to the fog light openings. I tier to do this rather than drill the holes. You cannot get them tight enough.
You have no idea what is sounds like when they fall off, are run over by the tire and rip all of the cooling ductwork right off the car. The track workers think it is grand fun to pick one of these smashed brake duct snakes off the track after stopping the track session.
It is “most uncool” when the track worker comes through the paddock at lunch dragging your smattered and smushed brake air duct looking for you and your car. =========================================================== 3. Two, four inch round by 8 feet long aluminum flexible semi rigid air duct - Home Depot # A186-627, $6.24 each, total of 12.48.
INSTALLATION: Slip the leading edge of the semi rigid air duct (item # 3) over the 5 X 4 reducer (item #1). You can go ahead and secure these two together using duct tape and glue.
NOTE: When this semi rigid air duct is purchased it is about 3 feet long. By pulling it, it can expand to 8 feet. DO NOT pull it, keep it short and compressed. =========================================================== 4. Two, white PVC pipe-coupling connectors (approx. 3 & 15/16 inch outside diameter). Home Depot # 189-030, $.96 each, total of 1.92
INSTALLATION: (This is the part of PVC pipe that normally allows you to joint two PVC pipe pieces together). Slip this PVC coupling half way inside the trailing end of item # 3. It may be a tight fit; I had to grind off a couple of small burs on the outside of the coupling. Use duct tape and glue to secure the aluminum duct over the PVC coupling. Only use one revolution of duct tape. You still need to fit the next item over the other half of the PVC coupling.
NOTE the reason this PVC coupling is used is for strength. The semi rigid air duct is not strong enough to firmly secure to the car. Next wrap a couple of revolutions of duct tape around the aluminum duct where it fits over the PVC coupling. The purpose of this is to protect the aluminum duct from the hose clamp covered in step 6. =========================================================== 5. Two, four inch three way angle adjustable elbows - Home Depot # B148-717, $1.70 each, total of 3.40.
NOTE: This is the trick part that makes this work. This is a three way adjustable piece that is about 6 to 8 inches long. It can be adjusted to an infinite number of angles. This is what gives you the ability to aim the airflow at the center of the rotor.
INSTALLATION: Slip the three-way angle adjustable elbow over the trailing end of the PVC coupling. The aluminum duct and the three-way angle adjustable elbow should now butt up to each other with both over the PVC coupling. After doing this you will no longer be able to see the PVC coupling. =========================================================== 6. Four stainless steel screw (3 to 5) inch hose clamps - Home Depot # A100-530, $1.67 each, total of 6.68
INSTALLATION: Firmly secure the semi rigid aluminum duct to the PVC coupling that is inside the duct by using a 3 to 5 inch hose clamp (item # 6). Be careful and do not tear the aluminum duct.
Next firmly secure the three-way angle adjustable elbow to the PVC coupling using a 3 to 5 inch hose clamp (item # 6). Again you will be clamping the 3-way adjuster over the PVC coupling. By using the PVC coupling you can get the clamp very tight. =========================================================== 7. One 3 foot section of 4 inch “high temperature” racecar ducting – Pegasus Racing Supply 1-800-688-6946, Part # 3620-4.00 $18.90
INSTALLATION: Based on the car you will need to cut a section of hose to reach the brake rotors. On a Cobra I needed about 6 inches. Slip the high temperature duct over the three-way angle adjustable elbow. You will need to glue these two parts together and then duct tape them together. =========================================================== 8. Four stainless steel screw (5 to 7) inch hose clamps - Home Depot # A 100-558, $1.82 each or 7.28.
INSTALLATION: Next you will attach the brake-cooling duct to the car. Attach the 5 X 4 reducer to the fog light opening. Next pull the aluminum duct until you find a place to secure the end of the duct where you have the PVC Coupling and the three-way angle adjustable elbow.
On a Mustang the best place is the front sway bar mount. I run the 5 to 7 inch hose clamps through the opening of the sway bar mount and then around the duct / three way angle adjustable elbow. Remember the PVC Coupling is underneath this area. With this underneath you can tighten the hose clam very tight.
Hang on we are almost finished. I next use a zip tie to secure the high temperature racecar ducting to the coil over springs. For this final adjustment you will want to have the car weight on the tires and wheels so you can make your final adjustment aiming the cooling air at the center of the rotor. The SLA front end I have installed has a perfect area for the 4-inch duct to reach the rotor and bearing.
With everything in place put the wheels back on, put the car back on the ground and check your full left and right steering wheel movement. Make sure your tire or wheel is not touching the new cooling ducts. I had to make adjustments several times before I got it where the tire / wheel would not hit the brake ducts.
Final step, with everything in place wrap everything in duct tape. This will hide all the Home Depot parts, protect the aluminum duct and make the whole assembly rigid.
When installed it looks racecar fabrication quality.
After having the ducts on for a day retighten the hose clams that secures the brake cooling duct to the chassis / sway bar mount. I have found it will need tightening up from time to time.
8. Roll of black duct tape. $3.50 ============================================ Total Parts Cost $63.74
Author- RSSS, RSSS96962@MSN.Com.
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