KENNY BROWN CSR Cobra
Builders Notes: KENNY BROWN Mustang Cobra IRS - CSR/OT - Club Sport Racer- Open Track Edition
Note - Kenny wrote the CSR/OT Builder's Notes were written back in 2004, so some editing has been made to the Blog to correct and update to current products and specifications.
My goal in developing the Kenny Brown Cobra CSR/OT edition is threefold. First, the '99/'04 Cobras are an exceptional "Bang-for-the-Buck" high-performance value, and with the growing popularity of open-track events, I have received quite a few inquiries on setting these hot-rods up as "serious" open-track cars. we also see a growing number of '00 Cobra Rs in our shop for the same type of open-track upgrades.
Second, I see so many people that love driving, but end up spending most of their track time tinkering with their cars because they have made uninformed decisions on the wrong parts or have invested in a high-strung engine before they built their "performance foundation".
So, I decided to put together a comprehensive Street Sport/Open Track package that is set-up and ready so all you have to do is jump in and go. The Kenny Brown Cobra CSR/OT is a sorted proven driver's car where you can spend your time at the track working on your driving skills, not you're mechanical skills.
Third, I love driving just as much as my passion for building cool cars. So I just had to create the CSR/OT (Cobra Sport Racer / Open Track) performance track package - that is totally streetable as well. I engineered it from the driver's seat out, just for your driving seat!
I have always felt that the more quality information you have, the better informed decisions you will make. To that end, I have put to paper my blueprint for building a very serious hot street or open-track car (base donor car can be a '03/'04 Cobra, '00 Cobra-R as well as '99/'01 Cobras (Kermie, my green '01 Mustang development mule is the equivalent of an '01 Cobra). I'm sure you will see that owning your own Kenny Brown CSR/OT as a "serious" open-track car is a quality, informed and smart decision.
As you read through my Builder's Notes you will also see that I put a lot of effort into developing the CSR/OT -- a lot of effort and experience that you can benefit from.
I should also note that there are a lot of additional options and things that can be added to the base package, but in the CSR/OT I really wanted to focus on the core ingredients to create a knock-out open-track Cobra -- because from a solid foundation, you can always build up.
The CSR/OT edition isn't something brand new, it's a proven track package which is the result of many years of intensive engineering, developing and testing. I introduced the CSR at the 2001 SEMA Show specifically to demonstrate the virtues of balance and grip over horsepower. In fact, back then to drive the point home with even more emphasis, the first CSR only had a V-6 engine.
The following summer we took the CSR (lovingly nicknamed "Kermie" for its green color) to a number of open track events in the Midwest. BMW and Porsche owners were absolutely amazed with Kermie's agility and track manners and how deceptively quick he was. The best part was the total disbelief and humiliation of Corvette drivers when they found out that they just had their ass kicked by a V-6 Mustang. You gotta love it!
Anyway, the point being that CSR/OT is not something new, but the latest offering in the CSR series. The core components of the CSR/OT are the same as in the original CSR and the CSR-GT Pro-Racer, a very serious all-out race car. The CSR package is well sorted and proven, and demonstrated over and over again that it is a very competent platform for drivers of all skill levels in open-track and racing.
The #1 rule I follow when building the ultimate track car (or warmed-up every day driver for that matter) is there is more speed in the chassis than in the engine and a good handling chassis trumps a big motor every time.
Before you start working on the engine or adding lots of power, build your performance foundation first. The foundation consists of four elements - chassis, suspension, wheels, tires and brakes. It doesn't make a lot of sense to me to add a bunch of extra power, when you're not using all the power you currently have.
Whether I'm building a hot track car or just a mildly hopped up daily-driver, the #1 rule is always the same, the more performance you want the better and more complete your performance foundation needs to be.
This is a simple rule that needs to be at the forefront of your mindset when building any track car, daily driver or anything in between. I have proven time and time again with Kermie (my green open track Mustang) that quickness on the track is all about balance and grip not having big power, and what works on the track can also work on the street.
- Extreme Matrix System
- Super Subframe Connectors, Extreme Matrix Brace, Jacking Rails
- Strut Tower Brace
- Rear Shock Tower Brace
- Super Street Cage with horizontal and diagonal bars
It all starts with the chassis. Whether you are building a skyscraper or high-performance car, having a solid foundation is critical to achieving your best result. In a skyscraper it's bedrock, in a high-performance car it's the chassis.
In racing we go to great lengths to make the frame as ridged as possible because we don't want the frame to flex and be a variable. The chassis needs to be ridged and suspension needs to do the moving. (Ever seen all those triangulated cross bars in race cars?)
Short of adding a full-blown roll cage, I have developed a very comprehensive chassis support system that goes a long way to stiffening up the chassis. (Incidentally, a stiff chassis does not mean a stiff ride. Quite the opposite -- stiffening your chassis dramatically improves you ride quality.)
The heart and soul of chassis support is the Matrix System which consists of the Super Subframe Connectors, Jacking Rails and the Extreme Matrix Brace. The Subframe Connectors tie the front and rear subframes together while also reinforcing the center of the sub frame, the Jacking Rails (very handy when jacking up lowered cars) run along the outer rocker pinch-weld and the Extreme Matrix brace connects the two with 4 full triangulations per side. (Remember that triangulation is the lightest and strongest engineering structure.) The Extreme Matrix system basically puts a mini-frame under the center of your car.
The three-point Strut Tower brace triangulates the engine bay and helps cornering and torque loads spread more evenly across the front of the car and into the main body structure. The rear Shock Tower brace (again triangulated) helps reduce twisting at the back of your car.
The special CSR version of our famous Super Street Cage is the crowning jewel of the chassis support system. The primary function of the Street Cage is as an "inner skeleton" to fortify the inside of the main body section. The Street Cage consists of a robust B-pillar main hoop, rearward running C-pillar support braces and low (for easy access) forward running braces. This special version for the CSR/OT includes a shoulder height horizontal brace for better safety harness shoulder strap location and a diagonal brace for extra strength. (There's that triangulation thing again.) So there it is, chassis stiffened up and ready for the suspension.
Creating the best handling Mustang suspension in the aftermarket isn't rocket science, but it is science. When I first sat down to design the CSR suspension, I pretty much knew what I was looking for from my many years of racing and building Mustangs for the track. I knew that the Mustang had a few good qualities and some very undesirable ones regarding handling, grip and braking that needed to be addressed.
The biggest challenge was to create the ultimate handling Mustang suspension while retaining the OE architecture, so everything was a true bolt-in. I spent a lot of screen time at the computer moving points around, adjusting parameters, running driving event simulations and balancing front to rear before the first prototype part was even built. And in the end the results were well worth it.
The key to the front suspension is the K-member. This rectifies many of the inherent Mustang shortcomings in one package. First the whole module is about 45 pounds lighter than stock which takes weight off the nose to improve front/rear balance. It stretches the wheelbase forward one inch (just enough so fender mods are not required on the for the '91-'93 cars - pre 93 requires a small adjustment to the front lower fender or install a '91 fender, instructions are available for pre '91 Cobras) , which shifts 1/2 percentage point of weight bias to the rear (Every little bit helps in a front engine car). The unique geometry addresses roll-center migration, anti-dive, bump-steer and camber gains with most of the camber gain dialed into steer rather than bump helping maintain a bigger contact patch under hard braking.
On 99-04 Cobras, we "hard-mount" the IRS carrier mount in the back to keep it from moving around and literally cut off all the suspension pick-up points and weld them back on to reflect the new geometry I worked out on the computer. Included in the geometry change is a Rear-Steer, which we have a special Long-Spacer Rear Steer Kit specifically for that application (a KB exclusive) that helps reduce the unwanted effects of rear roll steer, which can be pretty unsettling in the middle of a fast turn. The combination of converting to Tubular Control Arms and Coil-over Shocks takes about another 45 pounds off the rear IRS assembly.
Two more KB exclusive additions to the IRS assembly are the heavy-duty Forward Torque brace and the front CSR Aluminum Differential Mount bushings. Our Forward Torque brace is far more robust than the original and the CSR Aluminum Differential Mount bushings are straight out of the Pro-Racer program. The combination of the two mounts -- the front differential solid mounts combined with the carrier/frame rear hard-mount reduces the infamous wheel-hop Cobras are known for. The Aluminum IRS Bushing kit is adjustable so it is easy to adjust pinion angle to reduce drive-line vibration (I recommend that you set the pinion angle as high as it goes as that's how I do it on my cars and it works great) and being solid aluminum - It also works as a heat sink to transfer heat from the aluminum carrier into the main IRS frame assembly.
With geometry optimized, its time for control and that comes in the form of custom built and vaslved struts and shocks ans custom selected spring rates for your application represents by far the best control and dampening I could find without going to ridiculously expensive (and difficult to dial-in) racing shocks. I have Strange Engineering custom build the Cobra shocks to my specifications - using Proprietary valving I have developed over many, many years. The front coil-over struts are double adjustable and the rear coil-over shocks you have the choice of single or double adjustable.
I like to select the spring and sway bar rates for each CSR based on the owner's/driver's individual experience and driving skill level. Typically, I will start you out in the medium-soft to medium range. This will make the car very drivable, predictable and forgiving for your skill level and reward you with a very enjoyable driving experience.
As your experience and driving skills progress, we can increase spring and bar rates in stages to make the car even faster. It doesn't make sense to put an open-track driver even with good track driving skills into a car set-up for a Pro Driver because the objective here is to have fun, not see how accomplished your dry cleaner is at removing stains from your driving suit.
A Special Note: All the strut and shock packages for the '99-'04 Mustang Cobras come fully assembles including main springs, helper springs, spacer and spring thrust bearings. Additionally I personally pre-adjust your shock and spring package to a neutral starting point plus include a shock set-up sheet accompanied by a basic 101 Tuning Instructions, and of course we are alqways available to answer your shock tuning questions to help make your Cobra to be the best it can be.
- Front Tubular K-member
- Special K-member 2-pt Lower Chassis Brace (substitute for LCB above)*
- Oil Filter Relocation Kit*
- Street/Sport/Track Control Arms*
- Custom KB Spec custom built struts and custom selected spring rates
- Front Sway Bar (KB specified for customer) with bushings and End link kit*
- Offset Steering Rack Bushings Bump Steer Kit
- Caster Plus upper strut mount
- IRS Advanced Geometry with Hard Mount
- IRS Competition Rear Upper Control Arms
- IRS Competition Lower Control Arms
- IRS Rear Steer Kit
- IRS Forward Torque Brace
- IRS Aluminum Adj. Differential Bushings
- Rear Sway Bar Bushings
- KB/Spec Baer 14" Pro Plus 6-piston or 14" 6 -Piston Extreme Plus depending on your application (requires 18" wheels check with us for fitment)
- Slotted Rear 2-piece Rotors (We don't run big brake kits on the rear IRS due to spindle/bearing weakness. In testing we found that the big brakes created extensive brake pad "Knock Back" and Stiffening the spindle to reduce flex produced so much bearing flex that the rotor can cut through the lower spindle joint sending the axle, spindle, wheel, tire and brakes flying – ask me how I know this).
- High Performance Rear Brake Pads
- High Performance Stainless Steel Brake Lines (front & rear)
- High Temperature Brake Fluid
- Front Custom Brake Cooling Ducts
It doesn't take but one time careening into a corner at full speed and finding a very long or spongy brake pedal to realize just how important having solid dependable brakes are. Cobras come with pretty good brakes (Cobra-Rs are even better), BUT if you are building a track car you need Great brakes, period.
I have selected two very competent super-stopping KB Spec Baer Big Brake Kits with 6-piston calipers and 14" rotors for the front as a really good set up set-up. The 14" Big Brake Kits require at least a 18" wheel with enough space for the big calipers. Please check with us for a brake template to use on your 18" wheels to assure that there is enough clearance.
The front of the car does most of the braking so there's no real value to put big brakes on the rear. In fact, we tried big rear brakes on the CSR-GT Pro-Racer and found that they created more issues than they gave benefit - after much testing and tinkering we chose to use the upgraded OE rear 2-piece slotted brakes rotors and life was good again (One of those hidden little benefits of using a proven package - we test, you benefit). We upgrade the rear with racing pads and slotted rotors. I don't like drilled rotors for the track because they reduce rotor surface ares and always crack from the holes out. I only use slotted rotors because the slots help relieve the hot-gas buildup between the rotor and pad plus help carry brake dust away. All pro race cars run slotted (only) rotors.
I use stainless steel brake lines front and rear to insure good pedal feel even when things start getting a little hot. Speaking of hot, the entire brake system is filled with high-temperature brake fluid, again to help keep a firm confident brake pedal.
And speaking of hot again - we add cooling ducts to the front brakes. If you are really using your brakes hard, front rotor temps could run upwards of 1000 degrees or more so getting fresh air to them between stops extends the life of both the rotors and brake pads, saving you money or a costly mistake.
- Pirelli 18" / 19" P-Zero Corsa tires are my favorite for track and street
- We have a selection of 18" ans 19" alloy sport and racing wheels to chose from, call for more information
With your performance foundation in place, now we are ready to work on the power and performance.
- Torsen "torque-sensing" Differential
- Track Car Custom Side Exhaust with X-pipe
- Close-ratio Shifter
- Chassis Dyno
The '03 and '04 Cobras and '00 Cobra-Rs already come with a bunch of power so with the performance foundation, I have made the available power more usable. It actually feels like there's more power simply because you can now more efficiently utilize more of the power you already have.
For the earlier Cobras we can add a number of optional power adders including a supercharger or even the Ford Racing 5.0L 440 hp "cammer" engine.
For the '03 & '04 Cobras I give you a nice little boost in power by freeing up the exhaust. The dual side exhaust I developed for the Pro-Racer has become very popular so I decided to include it in the CSR/OT package along with an X-pipe with or without cats.
The CSR Side Exhaust, which unfortunately is currently unavailable, does a couple of great things. First the obvious -- add an X-pipe + lose the mufflers = gain some good power (We do a before and after dyno to show you the gain). The second more subtle benefit to the side exhaust is that it keeps the heat created from the exhaust pipes away from the differential and fuel tank. If any one has ran their Cobra at high temperatures, you will appreciate this modification. I will address the differential cooling and in the Cooling section.
If you plan on running tracks that have sound limits let me know so we can build you a custom exhaust package for the required noise levels. Or if you just want a quiet track car we can accommodate that too.
I have added a close-ratio shifter as a mandatory performance upgrade. Just like a competent suspension and solid brake pedal, toggle-like shifting is part of the whole Kenny Brown driving experience. After all, it's much more enjoyable to have minimal effort firm shifts you don't have to think about as opposed to "rowing" the shifter around wondering which gear you are in and whoops, you just missed your braking point.
We also offer the Tremec Magnum 6-speed heavy duty road race transmission as an upgrade option, and amazing driving and shifting tranny
To help get the power down, I have chosen a Torsen "torque-sensing" differential for the CSR/OT because I really like the Torsen in IRS cars. The whole "torque-sensing" thing simply means that inside the differential there is a bunch of worm gears that direct most of the torque to the tire that has most of the traction. So in an IRS car this relates to very smooth power transfer between the unloaded and loaded wheel and reduces opportunity for wheel spin.
- Rear Differential Cooler
- Functional Aero Trim Kit
- Thermostat Block-off Kit
You need heat in your engine, driveline, tires and brakes to get the most out of your car on the track, but too much heat though is a bad thing, a very bad thing. We already took care of cooling the front brakes now there are a few other cooling issues to work on.
First and most important I add a differential cooler because Cobra IRS differential housings (and everything inside) get really hot fairly quickly on track. In a live-axle car you have this big mass of steel housing with lots of surface area to deal with the higher track temps. In a Cobra, you only have a small aluminum center section mounted in rubber insulating it from the heat from the rest of the car. Further, if you look up at the IRS rear suspension assembly from the bottom you will see that it sits in its own air pocket or I should say "hot" air pocket with virtually no air-flow. Now you can see how dumping the exhaust out the side helps reduce temperatures at the back of the car.
With no air and a lot of heat, you have to get the heat out before you burn-up your differential and a remote oil cooler is the easy answer. I use a efficient diff thermostatically controlled cooler package with a good efficient oil cooler with a fan pack attached and high-volume oil pump because getting clean air-flow of any value at the back of a production car is really tough. The system 180 degree thermostatically controlled, so when the oil hits 180 the pump and fan kick on and don't shut off until the oil is back under 180. Even if the car is sitting back in the paddock cooling off.
At the other front of the car, I try to help engine cooling as well because production cooling systems really weren't designed for all-out track running. It's kind of a repeat of that minimal air flow thing at the back. Getting air in at speed isn't the problem, its getting it through the radiator and out of the way. Pop your hood and take a good look at all the "stuff" in front of, around and behind the radiator. Now if you were a nice stream of cool air entering the front of the car, would you know where to go? What do you go through, what do you have to go around and what about the places where you just get stuck and then what?
The first step is our exclusive Triple Thick, Triple Pass Aluminum direct replacement radiator. Plus on the Pro-Racer, I completely re-engineer the entire front to promote proper low restriction air-flow and maximum thermal transfer plus help create some front down force in the process. For a production car, short of re-doing the whole front of the car, I have developed a few tricks to help the air understand where to go.
The actual pieces of the Aero-trim kit will differ a bit from car to car because I design each kit for each specific car's needs, but the key element for all is a deeper and wider chin-spoiler / air dam. This is directly below the radiator and runs side to side. Air rushing under the car hits the dam creating high pressure in front and low pressure behind. High pressure in front of the dam is forced up into the radiator cavity with the excess spilling out to the side in front of the tires. The now large low pressure area behind the dam draws hot air down and away from the radiator plus creates a little front down force in the process. I do a few extra things to get more air to the radiator, such as adding a simple thermostat block-off kit that I designed, to make sure all the hot water from the engine runs through the radiator.
Another common element of the Aero-Trim kit is the horizontal splitters on the bottom of each rocker. The faster you go the more the tendency for air to "curl" under the car, too much air and the car begins to get a little "light" at the back. Having a side splitter stick out a little from the rocker discourages air-curl and promotes better high-speed stability. Also by keeping extra air out from under the car there is more room for hot air to escape from the engine bay.
For the super serious we have competition radiators and other cooling related items as options, and those cool "retro" looking front fender vents on Kermie are also an option.
- Sport/ Race Seat - Driver's side and optional passenger side
- Schroth Rally 4 Harnessbelt one-latch with grips and shoulder pads -
- Battery Relocation Kit (Moves the weight rearward for better balance)
- Fire Extinguisher
It's kind of ironic that I designed the CSR Series from the driver-seat out and in our build-up I'm not addressing it until the very end. Well, everything we have done to this point is to get your car prepped and ready, now its time to drive.
A proper driver seat and harness is as essential to the total driving experience as anything else we have done so far. The reality is -- how can you commit 100% concentration and effort to controlling the car if some of that effort and concentration has to be used in bracing and controlling your body as G-forces try to toss you about. (Remember a CSR generates a lot of Gs!) A proper race seat should fit you very snug with good lateral support and we have several sizes to choose from.
I chose the Schroth Rally-4 harnessbelt in the CSR/OT base package. This is a very simple and easy to use rally-style driver restraint system from Europe that buckles-up with one click just like a regular seat belt.
A little trick - tighten up the lap belt before the shoulder straps. The lap belt should be worn just like Britney Spears pants - low, tight and on the hips. If you tighten your shoulder straps first, your lap belt becomes more of a . . . belly belt.
You can option in an identical passenger seat and harnessbelt or upgrade to a full FIA approved professional grade 5 or 6-point racing harness with center cam-loc.
A couple of other interior touches are a dual digital temperature gauge and a fire extinguisher. Two things you really want to keep an eye on are engine temp and differential temperature. I gave up on the "mickey-mouse" aftermarket electric gauges years ago, so the CSR comes with a top of the line SPA dual digital temp gauge mounted on the A-pillar for easy sight. (currently not available) The fire extinguisher mounted inside the cabin is just one of those little things that you don't really need until you really need it, so there it is.
The one other thing I do inside the car is move the battery from the front to the back. In reality your battery is one big heavy chunk of lead that for better balance really needs to live somewhere in the right rear of the car, the lightest corner of a Mustang. I upgrade the battery to a "closed dry-cell" racing battery.
Again for the really serious, there is a lot more we can with interior and instrumentation.
- Dash Plaque and Under hood Plaque
- Exterior Kenny Brown CSR/OT Graphics Package
- Kenny Brown Engineering
- Vehicle scaled specifically for customer weight
- Special Track Alignment for customer weight
- Shocks pre-adjusted to drivers skill level
- Track Set-up Notebook
- Special CSR/OT Production Administration & Management
Your car may be built, but our work is not done. Now the rest of what comes with your CSR/OT is something you can only get here, because this is what we do and how we do it.
All CSR/OT Cobras are serialized and come with the traditional dash and under-hood production plaques, build books and all build data is archived for future reference. It also comes with a complementary track set-up notebook, tire pyrometer and pressure gauge.
You may recall that I choose springs, sway bars and shock settings for each driver. This is all recorded in your set-up notebook as well as the starting corner weights and alignment. If you want to continually improve your driving and adjust the car to make it even better, you need to keep notes and record pertinent data.
So if you call me from a track or when you are getting ready to go to another track and say "my car is doing this when I want it to do that, what should I adjust?" My first question is going to be - what are your tire temps and pressures? Without those, it becomes exceedingly more difficult to analyze what's happening and figure out what you need to adjust or how much to adjust it. Now you know why I give you a complementary tire pyrometer and pressure gauge, so when you need my help or direction, we can look at some data to make my job a bit easier and your results better.
At track events I have been approached about creating a special graphics package similar to Kermie because so many Mustangs look alike and you can definitely pick out Kermie. I have created a special CSR/OT graphics package that will differentiate your CSR as a serious track car and it will be much easier to locate on the track.
Special Note, since these builder notes were written, there is an excellent tech article Kenny wrote on tire temps and their importance to getting the most out of you car at the track - https://www.turnology.com/tech-stories/brakes-suspension/speed-secrets-with-kenny-brown-setting-tire-pressure-for-the-track/
So, as a special feature of the CSR/OT I have included unique CSR/OT graphics package (A lite version of Kermie's) including a door number block containing the last two digits of your production number.
Having KB graphics on your open-track car lets people know that you are serious and have a genuine Kenny Brown CSR and that's good for both of us. The way I look at it is that when you are laying waste on the track with the Kenny Brown name it's just like advertising so just for running the KB graphics on your CSR we credit you back a Co-op sponsorship discount.
Well there you are, with everything in place when you pick up your CSR/OT you're ready to go, just buckle up and smile.