BMW F82 M4
The time had come for Luke (co-owner of Tegiwa) to hang up the keys of his multiple race winning BMW E92 M3 and take on his next venture with something a little newer. The car of choice was a natural progression in the form of an F80 M4.
The M4 was already partially stripped and had a cage installed by our good friends at Safety Devices prior to us getting involved so our task was to get this build started properly from that point. Naturally, that means going back to a bare shell and starting from scratch.
Stage 1
Luke wanted to use the car for an attack on the 750MC Club Enduro class A championship which meant we had a solid idea of what we needed to achieve with the car. The car needs to complete 2 hour endurance races with a mandatory pitstop so alongside the usual chassis, braking and drivetrain requirements from a race car we need to make sure it can carry enough fuel, be refuelled quickly and allow for fast driver changes.
With that and Luke’s various sponsors in mind, the component choice will consist of a 120 litre ATL Fuel Cell, suspension components From Yellowspeed Racing, AP racing Endurance Brakes, Apex Wheels and some Carbon Fibre goodies from Eventuri. The idea is to make this build extremely reliable and as simple as possible; minimising and removing any unnecessary items to save some weight and make maintenance easier.
Once we got the car into the workshop it was time to go back to square one and remove all the original suspension, subframes, fuel tank, wiring looms and anything else bolted to the bodyshell to give us a blank canvas to work with and make some measurements for the fabrication to begin.
Shell Prep
A 120L fuel tank is a big component to fit into any car not just from a space perspective but also for weight when full. This means placement is important in getting the weight as low as possible in the car whilst avoiding the prop and heat from the exhaust beneath it. Some careful measuring and refitting of components to check clearance is essentially before you start to cut anything with a grinder and some extra time spent here can save you a whole load of headache further down the line! With the tank in place, we can start to fabricate the surround to allow us to securely mount it and fabricate the mounting for the fuel filler heads in the body as the standard filler neck is now removed along with the stock tank. Once this is complete we make a start on the air jacks.
Air jack location in the car is crucial to allow the car to lift squarely and high enough to be able to remove the wheels. Again, this requires some components to be refitted to the shell and a few hours with a measuring tape, set square and spirit level. Once the positions are marked, holes are drilled in the floorpan, the tubes inserted and tacked before we fabricate some gussets to ensure the 1400kg car can be lifted safely by the Yellow speed air jacks.
Shell prep is completed by blanking off any un-necessary holes in the bulkhead from HVAC system removal and the various redundant holes from component and wiring loom removal. Once this is complete, we tin tape the remaining unused smaller holes and get the shell off for paint!
Drivetrain
Whilst the shell is at the paint shop we can concentrate on the sub assembly of the engine, gearbox, diff and running gear to be refitted when the shell returns. The 3.0 litre twin turbo engine in the M4 needs little work for us to meet the power to weight requirements for the class and this stage is really about ensuring its reliability over the course of the season. We remove any unnecessary auxiliaries, replace Spark plugs, coil packs and replace all auxiliary belts. All fluids and filters are changed for Motul. The bulkhead and exhaust tunnel of the shell are covered in heatshield matting before refitting the engine to ensure the heat is kept away from the cabin, it’s hard enough to drive a race car for an hour as it is without the additional temperature a twin turbo straight 6 at 8k RPM creates.
Suspension
With the subframes and all components to be re-used cleaned, powder coated or aqua blasted we installed Powerflex bushes to the diff carriers and spherical bushes to front control arms. We installed rear Hardrace spherical camber and toe arms to allow us more adjustability in the geometry set up as well as removing any un wanted geometry changes from rubber or poly bushes. Spherical bushes allow complete freedom of movement and allow the 3 way Yellow speed dampers to control the car as intended.
Re-assembly and Interior Work
Now that the car was rolling again it was time to lay out the wiring loom and remove all un used modules and related wiring. We made an overlay loom to run the additional fuel lift pumps, rain light, AIM dash, VBOX and pit to car radio. This drops in on top of the trimmed down OEM loom so all of our additional systems are easy to maintain, change or add into if needed as well as being self-contained in its own cable sheathing,
The fire extinguisher system and Cartek electrical isolator were installed next alongside all of the air jack pipework. We run this neatly along the interior and secure with cable saddles along with the wring loom. A KMP steering wheel was added with bigger and more positive gear shift paddles and radio button so the controls are user friendly and easy to reach.
Fuel Feed & Brake Lines
With the fuel tank and wiring in place we run the fuel lines through the car via a bulkhead fitting, into a dry break drain fitting before running to the fuel rail on the engine. A fuel drain will allow us to accurately calculate fuel consumption, ensure we have correct fuel starting level in the car and to calculate our fuel pit stop window. The brake lines are then routed through the car to each rear wheel to ensure there is no potential for damage whilst fitted to the underside.
Exterior
Although a very fast car, the M4 is also pretty heavy. Any additional weight a race car carries hurts its ability to accelerate, stop and turn whilst also making it less fuel efficient. Tegiwa had some fibreglass doors made from the originals and supplied us with a Carbon bonnet, Carbon rear wing and a Tegiwa F series Carbon fibre splitter.
The splitter has brake ducts incorporated into it, so we made some additional modifications to the brake disc baking plates to allow us to couple up a flexible hose duct to direct air flow to cool the brakes. We then added some lock stops into the steering rack to prevent the wheels from eating through the ducting making it less efficient during a race.
The rear wing will give us some much needed high speed stability and as its adjustable, also adds another dimension to our setup window.
Livery
Now that the M4 had all panels installed window kit in place and pretty much back together it was time to have it stickered by Chris at CN signs. The design was done by the guys in the Tegiwa office and once again they did a great job.
Racing
We ran this car in 2019 in the 750MC Club enduro championship. The M4 was piloted by Luke Sedzikowski and David Whitmore. It was a tough season which was plagued with bad luck. The car had great speed winning races and securing podium finishes but with a DNF from contact at Oulton park and a puncture on the last lap at Silverstone whilst leading the race we finished 2nd by only a couple of points. Alongside the race wins and podiums the car was awarded with ‘Best prepared race car’ at the 750MC awards which as a car builder is a pretty nice award to receive.
Check out some of our favourite racing shots.
