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A day at the track with my friend George
I have a saying - "A Bad Day at the Track is better than a Good Day at the Office!" That makes a good day at the track absolutely PRICELESS. Well I had one of those priceless days at the track recently at Putnam Park. Over the winter one of my customers George decided to step up the performance of his 2001 Kenny Brown Cobra. George does quite a few track days and wanted to be able to run with the really fast guys. So he added a Vortech Supercharger and had the engine upgraded. More power is great but unless the rest of the car is upgraded to match, most of the power will be wasted.
George ended up with nearly 550 horsepower which is plenty to chase down Corvettes and Vipers on the straight, but just like Porsche upgrades the entire car when they add a turbo, I laid out a plan to upgrade George's car to support the power and up the performance. I had a 4 part plan - Power, Suspension, Aero and Wheels & Tires.
The results were spectacular, the car drove like a dream - fast, stable and handled like it was on rails; it reminded me a lot of Kirmie, the best and my most favorite track car. I wanted to accompany George on his first outing to help with anything that came up, help engineer and set-up the car for his driving style and give him a little driver coaching as this would be a different car from what he drove last. We had a couple of small teething issues in the morning; good thing I brought Scottie along, Scottie was one of my mechanics when we ran the Mustang Challenge. When I go the track I always like to bring along "Smartly Attired Lads" with tools, to support my activities.
My guess on set-up was pretty good as we didn't have to adjust the car, only tire pressures. The other adjustment was George's driving style. Absent from his Kenny Brown Cobra for nearly a year, George had been attending track events with his Porsche. Initially he was using a classic Porsche line, early apex and power through the corner. The IRS Cobra actually drives more precise and the line calls for a little later apex, rotating the car and power down. I try to set-up my cars for and teach drives to focus on getting off the corner, the sooner you can put the power down - either around or before the apex - the faster you will be on the straight. Once George caught on to my driving technique, his lap times started falling like rain. Every session was much quicker and the race prepped Porsche GT-3's that passed him the morning quickly fell prey to the Cobra's prowess and potency in the afternoon - making a priceless day even more priceless.
Here are the details on my 4 part plan - Power, Suspension, Aero and Wheels & Tires to upgrade George's Cobra to match the power and up the over-all performance.
- Supercharger heat exchanger
- Supercharger Water pump
- Rear mounted supercharger water tank
With all that power, I knew heat would be a problem from supercharging so keeping the charged air cool before it hit the engine was really important. The heat exchanger that came with the supercharger kit was pretty wimpy; I've used oil coolers bigger than that. The heat exchanger came off and I replaced it with a huge '03-'04' Cobra Duel Pass Heat exchanger. The water tank for the SC intercooler was mounted high and up front which does a couple of bad things, it is weight high and in front of the front axles and it hold heat, something I want to get rid of. The most logical thing to do was remount it in the back of the car on the passenger side (the lightest corner of the car). The only trick was to mount it slightly higher than the highest point of the intercooler on the engine as to not cause air pockets. With the big heat exchanger and rear mounted water tank in place we tested the system only to find the water pump that came with the SC kit was pretty pathetic, I knew it wouldn't cut it so to the parts catalogue and I found a super high flow water pump that proved to be well up to the task.
- KONI DA
- Coil-over conversion
- High rate springs
- Corner weights
With increased power I wanted to step up the suspension. The car had the KW non-adjustable coil-over struts we used back then which are pretty good but I wanted to up the spring rates quite a bit and the shocks wouldn't be able to take it. Increasing the spring rate will make the car faster, but the window for error shrinks proportionally which is why I only go with higher spring rates for experienced drivers. George had quite a bit of experience so I wasn't worried.
I'm looking at a couple of options for a high-rate true coil-over strut solution for SN-95 Mustangs but for now KONI double adjustable struts with my coil-over conversion would work just fine. I also up the rates on the rear IRS KONI coil-over's to match the front. I made my best guess on the set-up as we aligned it and also adjusted the corner weights. My guess was pretty close as we didn't need to make any adjustments at the track.
- Hood venting
- Side splitters
- Radiator ducting
The faster you go the more important the Aero becomes and this car was going to be fast. I had a pretty good baseline on Aero improvements from Kirmie. The first thing I did was vent the hood. He already had an '04 Cobra carbon that was pretty new except the vents weren't very big. To save his hood I found some carbon vents used in Grand-Am that just fit into the vent groves of the hood. We also opened up the existing vent by about 30%. As you can see the result was 12 hood vents vs. 2. A Vented hood not only extracts heat, it reduced pressure under the front which adds grip via down-force. A properly vented hood is worth a half to a full second a lap at most tracks.
Still at the front of the car I wanted to manage the air under, through and around the nose. I added a Mach-I chin spoiler to lower the frontal area and added a splitter on the corners to separate the air then added leading edge fender opening to cover the width of the exposed tire. This does two things, creates a negative pressure area in the fender well to extract air from the nose and shields the tire as it turns so the turning tire doesn't push air into the fender opening.
Down the side of the car I use a horizontal splitter on the bottom of the rocker molding. As a car goes faster air wants to curl under the rockers building up pressure under the rear of the car reducing stability. The rocker splitters helps keep the air out from under the car, keeping the under car pressure low adding grip and stability.
The other big Aero improvement was my Club Wing. The Club Wing is 61" wide and has a good look on track day cars where my Pro wing is 66" wide. Both are low-drag and highly efficient, so much so that they start working at 40 miles an hour and I run about 2-4 degrees less angle of attack to other race wings and get better down-force. And please don't confuse real race wings to "dress-up" wings that are so prominent in the aftermarket like the Cobra R or dozens others. While we were there mounting the rear wing, I took the opportunity to take out some weight by using a super light-weight rear carbon deck lid.
The last Aero improvement is important, radiator ducting and air flow management. We spent a great deal of time building a duct from the fascia to the radiator, this makes sure all the air that enters the front of the car goes through the heat exchanger and radiator - Very important in managing heat. The other part of radiator management is I added an air dam over the chin spoiler under the nose from wheel to wheel following the curvature of the lower split line. This does two things, creates positive air pressure in front of it forcing air up and into the radiator duct and low air pressure behind pulling air through the radiator and out under the car.
Wheels & Tires
- BFG R-1
George took care of upgrading wheels and tires, he had a set of out Black Chrome Cobra-R wheels so he up fitted them with BFG R1 DOT track/race tires. These are pretty good tires, I know because that's what we used in the Mustang Challenge series and a great choice to match all the other upgrades.
The Final Touch
The final touch was the Kenny Brown Motorsports number plates on the doors and trunk. Many driving clubs and track day events now require the cars carrying numbers so we used the same type of number plate we use on our pro race cars.