Some years ago I worked on a race team running a BMW 320i Super Tourer in a race series.
These cars used to run in the main touring car category in the 90’s, and competed against the Holden and Ford V8s at Bathurst.
The Super Tourers were similar to the British and European touring car categories, running 2L n/a engines limited to 8500rpm, with limited aerodynamic aids, and limited tyre width (225 from memory).
Apart from that the rules were fairly open, so the big budget cars had some very impressive engineering.
Engines were generally swapped out for each race - with the new one installed for qualifying. Engine life spans were around 300 - 500km, and a “rebuild” cost around $100k.
This particular car was a fairly late model, with many improvements over the earlier ones - including a very controversial active lateral brake bias controller, which was a completely mechanical system using a pendulum to control the left-right brake pressure to allow harder braking into corners without locking wheels.
It was very well hidden behind some carbon fibre panels under the dash!
In their time, the Super Tourer engines were pretty advanced - making 300+ hp from a naturally aspirated 2L production based engine. They were heavily modified from standard, for power as well as lighter weight. These ones ran titanium conrods, very short skirt pistons, dry sump, and featured a lot of carbon fibre parts.
The carbon fibre cam cover is especially nice
Note the oil pump is driven from a normal multi-rib belt (not a toothed belt)
The pipe running along the head under the intake ports is the coolant outlet manifold. Instead of the coolant having to flow through the head and exit in one place as in a production engine, this manifold keeps the coolant flow even across each combustion chamber to avoid uneven temperatures.
The porting job on this engine was pretty amazing. It was obviously all CNC, and the valve guides had been machined in place to avoid any excess disturbance to the intake air flow.
The exhaust ports are similarly nice, but a bit less clean!
The valve train was fairly interesting. There was obviously not enough space in the head to achieve the intended valve lift with the traditional production round tappet design, so the head had been machined to fit a rectangular tappet and allow clearance for the much larger cam lobes.
The intake is fed by a set of flat slide throttles, so when the throttle is open there is no restriction to the air flow.
The airbox is possibly the most impressive part on this engine. It’s all carbon fibre, and huge! The intake bellmouth is about 150mm in diameter. The offset intake trumpets allow much larger bellmouths and a larger airbox volume.
Note the secondary set of injectors inside the airbox. Under full throttle conditions fuel is injected via these as well as the usual ones close to the intake ports. It allows more time for the air and fuel to mix properly. This injector rail failed at a race and filled the airbox with fuel. Fortunately we caught it before hydro-locking the engine or starting a fire!
The exhaust headers were super light weight, made of very thin wall stainless steel, or possibly inconel.
They get pretty warm in operation
The ignition coils appear to be pretty standard, but are mounted in a very intricate carbon fibre frame! Interestingly, the engine runs “wasted spark” ignition, using two coils with twin ouputs, so the spark plugs fire every revolution and a spark is “wasted” every exhaust stroke.
The engine drives the car through a very fancy multi plate carbon fibre AP Racing clutch. Even though it is tiny and very light, the flywheel section has holes drilled around the edge to lighten it further!
The clutch is actuated by a concentric slave cylinder and thrust bearing mounted in the bellhousing, which also happens to be the oil tank for the dry sump lubrication system! This part is all cast magnesium alloy. The plastic tube on the front with a cable tie in the middle is the oil level gauge, and the two blue fittings at the top are for the oil return from the engine and the breather / vent.
The aluminium pipe pointing forward from the bottom of the oil tank mates up to the inlet of the oil pump. It runs through the middle of the engine mount, as seen in this picture.
Behind the bellhousing / oil tank sits a magnesium cased Holinger 6 speed sequential gearbox. These reportedly cost about $60k! It was fairly quick to remove from the car, open the case, and stack a new set of gears with different ratios in it for each track. Not pictured is the $20k carbon fibre tailshaft which used kevlar flex plates instead of universal joints like a normal car. The gear lever had a strain gauge on it, which was used to cut the ignition during gearshifts so clutch was not required.
The cooling setup in this car was pretty impressive. Two radiators are mounted in a V configuration inside a very complex carbon fibre duct which feeds the outlet air into the wheel arch area in front of the tyres - reducing the amount of air going under the car. Underbody aero / flat floors were not allowed in the rules, but this car had a suspiciously large and flat “fuel tank protector” and some oddly shaped mufflers which happened to fill in a few of the underbody gaps
The whole engine bay was designed so that the engine and gearbox could be removed very quickly - and the engines came with a trolley that wheeled into place for the pre-qualifying engine swap. Note the roll cage tubes completely containing the suspension strut tops.
Brakes were an important part of the performance of these cars, and there were two common options - 8 piston Brembo calipers, or dual 4 piston AP Racing calipers as this car had. Wheels were 18″ in diameter, with center lock hubs. We had a massive torque wrench (about 2m long) for tightening the wheel nuts - which had opposite threads on each side of the car to add to the confusion! In this picture there is a “transport nut” installed - which provided a convenient tie down point. Not pictured but of some interest are the wheel bearings. This car ran huge diameter wheel bearings lubricated by a light oil instead of the usual grease - for less rolling resistance but also less bearing play, which could cause brake pad “knock off” and slower braking response. In their heyday, teams would replace the brake rotors with super light ones for qualifying. They could only handle one lap at full pace, but reduced unsprung mass!
Suspension was also a “no expense spared” part of this car. It was apparently built by McLaren, and was vastly different to the earlier versions of these cars. Almost all parts were CNC machined from billet aluminium. In this picture of the strut top you can see the fine adjustment wheel for the camber.
From underneath you can see how the strut is attached to the cast magnesium front hub / knuckle assembly, as well as the carbon / kevlar brake cooling duct and the pushrod and bellcrank setup for the swaybar linkage.
The swaybar is a proper blade adjustable type. You can see the adjustment cable which rotates the “blade” at the end of the bar. Front and rear swaybars have in-cabin adjustment. Linear potentiometers attached to the swaybar bellcranks provided suspension travel readings to the onboard data logging system.