By Khiem Dinh
Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing. All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.
2013 brought big changes to the BMW Team Rahal Letterman Lanigan with the introduction of a new race car, the Z4 GTE. The M3 from previous years was getting a bit long in the tooth along with its production coming to a halt. BMW had already developed the Z4 into a GT3 race car in Europe, so it was a logical step to develop a GTE version of the car. Furthermore, the dedicated coupe silhouette of the Z4 fit in much better with the low-slung competition versus the tall and narrow sedan based chassis of the M3. Developing a new race car is never easy and even starting with the GT3 variant required many changes. Despite the short development time for the new race car, BMW Team RLL has been able to garner a few podiums along with a win in 2013. Follow along to see what makes the Z4 GTE tick.
Up top is the old M3. Below is the new Z4. Big dry carbon ducts are still used to exhaust the radiator air out the hood. Two long diffusers are still used to go from the restrictors placed in the grill area to the intake manifold. The engine is still a 4.4L V8. Everything else between the two engine bays is drastically different. The Z4 is currently equipped with strut front suspension with adjustable camber plates. Braces triangulate the strut towers to the rear firewall. Looking at the fluid reservoirs along the firewall on the driver’s side, it’s cool to see the good old ‘sock’ trick used to absorb any fluid that may boil out. Or maybe they are called wrist sweat bands? Whatever they are called, motorcycle guys use them too on their fluid reservoirs. On the passenger side next to the strut tower is an aluminum looking box which I think is the coolant reservoir based on the low pressure hose going to it. It also has a hose going from it to what I believe is a swirl pot. Having the coolant related stuff mounted nice and high should allow for easy bleeding of the system to get all the air out. On a side note, one interesting difference between the GT3 and GTE versions of the Z4 is how the engine is restricted. The GT3 uses a restrictor plate (similar to NASCAR I suppose) while the GTE uses sonic restrictors.
In case you were wondering what the black bar going across the engine bay is for, it’s to allow the team to do an alignment using the tried-and-true string method. The M3 had some fancy dry carbon ducts to feed clean air to the passenger compartment; it appears the Z4 makes do with cruder neoprene ducting.
There is a lot of ducting going on as you can see with all the tubes. I’m guessing the fat one in the engine bay is for the A/C system which is required in the GTE car but not the GT3 car. Integrating A/C into these race cars is no simple feat as the cars are often optimized from the outset without them. So then it becomes a job of trying to fit a fair number of components into whatever nooks and crannies are still available; so props to the engineers for finding places for the A/C compressor, condenser, evaporator, receiver/dryer, tubing, ducting and wiring. It appears THREE tubes are used for the brake cooling with all of them connected to a single duct grabbing air from the front of the bumper. I’d guess the smallest of the three tubes (the top-most one) feeds the caliper while the two larger tubes feed the rotor. The AP Racing brakes look to be a carry-over from the M3 and you can see the temperature stickers and paint on the caliper and rotor. I’m guessing the brake pads are Project Mu based on their aqua blue/green color.