- Growing up with an interest in motorsport, the German DTM racing series has always
been a series I've been interested in.
Particularly the close knit racing, along with the high aero downforce
on these cars always makes for an impressive scene.
However it's not that often that we actually get to dig in deep and find out a few
of the details about what makes these cars go.
We're here at Goodwood with this 2018 Mercedes AMG C63 DTM car.
Now it isn't the current model car and there have been some changes for the
2019 season.
However it's still a good opportunity to find out what went into last year's model.
While on the outside, these cars may resemble the factory road car that you
can buy off the showroom floor, and of course that's the sales point
for manufacturers such as Mercedes, once we dive in deep, we find out that
there's really not a lot of factory componentry in the cars.
It actually starts with a spec carbon fibre monocoque chassis.
And this is the same chassis used across all of the cars, irrespective of the
manufacturer.
This is done for cost cutting measures, along with achieving some kind of parity
between the different manufacturers.
Interestingly enough, this particular spec chassis is exactly the same as used in the
Japanese Super GT series.
Now that monocoque chassis is very similar to what we see in the likes of Formula 1.
It's very very strong and very very stiff.
Plus it also adds a safety element to protect the driver in the case of an
accident.
From here, the manufacturers are free to adapt their own bodywork onto
the spec chassis.
And of course that bodywork is all developed in carbon fibre to aid keeping
that weight as low as possible.
The aerodynamics are also tightly controlled and this is one of the areas
I've always loved with DTM.
You can see all of the aerodynamic appendages around the car.
In particular the intricate details that are used down the sides of the car,
along with the exhaust exits on each side of the cockpit.
An interesting aspect that I picked up on was the ability to quickly change the
angle of the rear wing.
This doesn't require much in the way of tools and can be done very quickly
in a pitstop.
There's guides on the uprights for the rear wings so that the mechanics
adjusting the wing, can really easily dial in an accurate angle for the wing
to suit a different track, or the specific driver's preferences.
The engine in this instance is a four litre Mercedes AMG V8 that produces
around about 500 horsepower naturally aspirated, revving to 8000 RPM.
Now we don't have a lot of details on the inner workings of that particular
engine, this is still closely guarded by Mercedes and that's understandable.
However in this form, to achieve some kind of parity between the different
engines used in the class, the engine does need to breathe through a pair
of 28 millimetre restrictors.
So ultimately this restricts the maximum airflow into the engine and then it's really
up to the manufacturer to do the best job possible of extracting as much
power from that air flow as they can.
What we can see is to aid weight distribution, the engine is mounted
very far back in the chassis.
And what this does is makes it impossible to fit a traditional transmission on the back
of the engine, there's simply not enough room.
It would be essentially sitting where the driver needs to be.
So in order to get around this as well as again to aid weight distribution,
there is a controlled spec transaxle fitted to the rear of the car.
In this case it is a Hewland six speed transaxle.
This is a paddle shift dog engagement gearbox.
It uses a conventional mechanical LSD fitted to that.
The gear ratios again are standardised across the entire class,
making sure that there is no advantage to be had between different manufacturers
in this area.
In order to get drive from the engine back to that transaxle, a prop shaft is used which
runs straight off the back of the crankshaft and the clutch which is only used for
getting the car off the start line, is also fitted to the transaxle in the
rear of the car.
This helps with achieving a weight distribution as close to 50/50 front
to rear as possible.
One of the obvious aspects with any of the DTM cars is the complexity of the
suspension arrangement.
What we can see though is the use of an in board mounted suspension damper
and this is actuated via push rods through a bell crank.
An interesting aspect to do with safety that we did pick up is that in the event
of a major accident, it isn't uncommon for the engine to end up separating from
the chassis.
And when this happens this can result in a potential for fire with fuel spilling
out of the ruptured fuel lines.
Now this is actually dealt with in the DTM class using dry brake quick release
connectors for the fuel lines.
These are set up so in the event that the engine breaks away from the chassis,
these are designed to break free and this will seal the fuel lines,
making sure that no fuel escapes which could create a fire.
In another attempt to control costs in the chassis, interestingly enough the entire
wiring harness for the chassis is again a spec part.
So this is the same spec wiring harness that is used across all of the manufacturers.
Now of course that's not going to allow you to attach that wiring harness to
a variety of different engines.
So here this runs up to a bulkhead connector at the firewall.
From here, each of the individual manufacturers will make up their own
wiring harness to adapt to their engines.
The electronics package in the car is complete Bosch from start to finish.
This begins with a Bosch MS 5.1 ECU which is in charge of the engine control,
along with the shifting for the paddle shift system with that Hewland six
speed transaxle.
Power distribution to all of the circuits in the car is controlled with a Bosch
PBX 190 so this replaces the traditional fuses and relays that we'd see in more
budget spec cars.
This is a solid state electronic system controlling the current flow and power
supply to all of the circuits in the car.
The final part of the package is the Bosch DDU driver display.
So this acts as a driver display, giving the driver all of the relevant information
that he needs to know, as well as displaying any warnings that may become active
while the car's out on track.
This also acts as a central logging hub, logging all of the relevant information
from the engine control unit, as well as any other chassis sensors that the race
engineers need in order to improve the car.
In an interesting aspect here, the data is logged into the dash itself,
but in order to quickly retrieve that data in a pitstop, there is a remotely mounted
military specification USB stick that can be quickly removed as the car comes
into the pits.
Looking at the steering wheel, there is a lot of adjustability there for
the driver.
It is interesting though to just note that these cars don't use any driver aids.
There is no ABS fitted to the car, there is also no traction control.
But the adjustability on that steering wheel allows various mapping options
to be controlled.
There are of course on the back of the steering wheel, paddles for upshift
and downshift.
There is also a third paddle which actuates a line locker and this is used on the start
line to prevent the car creeping before the start lights go out.
Now since aerodynamics are so important in the DTM class,
it's worth mentioning that the aero downforce on this car is a little hard
to get solid details on.
Talking to the Mercedes engineers, I was told that at around 200 km/h
the car produces enough downforce to drive upside down.
Given that we also know that with the driver and fuel on board,
these cars weigh around 1150 kg, it's not too difficult to do your own
maths and figure out approximately how much downforce the cars are
producing, probably one more reason why the likes of driver aids such as
traction control and ABS, maybe not quite so critical in the DTM class.
And of course this brings back some of the requirements for the driver to
actually work a little bit harder rather than relying on electronics to pick up
the pieces if they don't get it quite right.
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