- When it comes to professional forms of motorsport, often these days it's a little
hard for us watching at home to really relate the sorts of cars we see out on the
racetrack with something that we can go and buy from the local dealership.
However if we revert back to the earlier days of DTM in particular, the likes of the
Mercedes-Benz 190E behind me is something that genuinely looks like your
factory road car.
And we're here with Gert from Mercedes-Benz Classic to find out
a little bit about the development of the 190E DTM car and find out in particular
how they made so much power out of such a small capacity engine.
So first of all Gert, just getting onto the body shape or the car that you based it on.
And if we look at the modern DTM cars, really it's completely different to what we
can buy, you're talking about a control monocoque chassis with a silhouette
body on it and a huge amount of aero.
The 190E predominantly looks like a production road car.
So what were the rules around what you could use?
- Basically we used a standard car and with the 2.5 litre car we also produced 500 cars
and it was called Evolution I.
And then a further step was Evolution II, always build 500 cars to use all the things
for racing to improve power and the output of the car.
- So this is one of the rules, you couldn't just go ahead and make a complete one
off special and call that your base for your race car.
In order to make it somewhat relatable to a production car, to use it, to homologate
it for racing use, there had to be a production run of at least 500 cars?
- Correct
So the homologation says, you have to produce 500 cars.
If you produce this as you want to catch up with the homologation,
it's fine in the regulation.
- Now let's talk about this engine.
We talked off camera before about the fact that when you were competing with this car,
you were competing against the likes of Audi using a 4.5 litre V8 and you're using
a relatively small 2.5 litre four cylinder.
Doesn't seem like a very fair fight.
Can you tell us for a start, what sort of power were you getting out of these engines?
- Finally in '92 we reached around about 350, 360 horsepower with a four cylinder engine.
The standard production Evolution engine had around about 235 horsepower.
Even if we had to compete against the V8, it was a big step forward.
- Now the rough line in the sand has always been, for a naturally aspirated engine,
if you can make over 100 horsepower per litre, generally you're doing pretty well.
So 360 horsepower from 2.5 litres, that's exceptional.
It's a little tricky to make a lot of power from a naturally aspirated engine.
Can you give us some insight into where some of those key aspects you focussed
on were for making that power?
- I think the main thing was to implement a Motronic system which was at that time
state of the art.
It was a difference to the production engines.
So there we reached quite a few more horsepower and also we had some little
bit lighter pistons and all these things around to rev higher.
We reached maximum revs around about 10,000 RPM which was also
a big step forward.
- And the production engine in the road car, what did that rev to?
- I would reckon, 7000, 7500 so that was also a big difference.
- Alright so you've just mentioned the Motronic system, so this is the electronics
controlling the fuel injection.
Again we're talking a long time ago in terms of our electronic control technology.
So this was just an advance over what came out in the production road car,
allowing you more configurability, more tunability with the fuel system?
- Correct, also you could rev higher because the igniiton was faster
and you could set up better programs, let's put it this way.
Much more flexible and you could set up also the program to the racetrack
or according to what the driver was requesting, all these little things.
And that made a difference to the standard production engine.
- Now there are a couple of things I want to focus on here.
And one of them which for the era is quite a step forward.
Over and above what the production engine had, you actually modified this to have
essentially variable cam control on both the inlet and the exhaust.
Now not continuously variable cam control but this was a switched system.
And how critical was that to getting the performance out of the engine?
- The idea was just to have also lower revs when you need more torque and on
the higher revs, the maximum output.
And therefore we developed basically a adjustable cams.
That was also a big step forward in power, also compared to the standard car.
- Now the other aspect we see there on the intake side of the car, the whole intake
system, completely different from what we'd see on the road car.
In particular it's got a slide throttle body arrangement.
Can you talk to us about the slide throttle body, what makes that an advantage
over a conventional butterfly style throttle body?
- OK a race car normally goes full flat most of the time so if you are full flat on the
throttle the opening in the manifold is always open.
There's nothing which can basically break the air to come into the engine.
That was the difference to a butterfly.
- Now with the slide throttle bodies when you're at wide open throttle,
sure you've got no interference to air flow but it's likely that at part throttle in
particular it may actually provide more turbulence.
Was there any downsides there or is the part throttle really just not a consideration?
- I think that wasn't really a consideration.
You also had the chance to basically have two or three injectors and you could set
up that with the Motronic system when you need the 1st or the 2nd or the 3rd injector
and then you could overcome this problem.
So I think this configuration which you can see here on the car was the maximum
you could reach at that time.
- And just talking about that, you mentioned the two or three injectors so what we
actually see there is there's one injector fitted right down by the cylinder head
and then you've got a second injector fitted further away from the inlet valve
up past the throttle body so you could change which injector was being used
based on the way the engine was operating?
- Yes correct, you can also trust the time, when it's coming, when it will inject.
So we had all the opportunities to set up your engine in the best possible way.
- Now another unique tuning aspect that we talked about briefly off camera is
the inlet manifold, sorry the inlet trumpets I should say, outside of that slide
throttle body arrangement.
Now this is all beautifully moulded in carbon fibre but do you have the ability to
actually change the inlet runner length based on the track?
How does that work?
- Basically depending on the length of the manifold, so you give the air more time
or not so depending if you want to reach high revs or maybe more torque on the
lower revs.
You can also trust the lengths of the manifold.
You have to set that up on a test bench and you have to think about what track
you want to go and maybe if you have a long distance ways, you have to trust
the manifold again against a short race.
All little things you have to keep in mind.
- Yeah look it was a lifetime ago in terms of the technology we have now but still
no mean feat getting 360 horsepower out of a 2.5 litre four cylinder.
It's been really interesting getting some insight into the development of that
engine so thanks a lot for your time there Gert.
- Pleasure.
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