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DTM S14 Slide Throttle Bodies
Minimum flow obstruction

S14 DTM Slide Throttle Bodies During the last years of the factory run BMW Motorsport E30 M3 racing campaign in the DTM series, things were very competitive. BMW felt outclassed in terms of horsepower to Audi, and to Mercedes in terms of aerodynamics. But the little M3's still had the advantage in the handling department. BMW held to it's comparatively small 2.5L 4-cylinder powerplant, and did everything they could think of to increase power.

One of the features they introduced was a swap from traditional butterfly throttle bodies, to a slide-throttle arrangement. Slide throttles operate just like they sound, the throttle plates slide sideways, instead of rotating about an axis as for butterflies. The advantage on paper is that when the throttles are fully open, the plates are completely removed from the airflow, and there is no obstruction blocking the inlet path to the combustion chambers.

There is a downside to slide throttles, which is that they have a reputation for offering poor driver control at part throttle. The modulation is not as good as with butterfly throttles, or barrel throttles for that matter. Perhaps for this reason, they are not all that common in motor racing, not even in F1. Personally I feel that BMW's resorting to slide throttles in the later part of the E30 M3's racing career shows how intensely they were trying to increase horsepower, and in fact, they did successfully achieve some impressive figures, with reports of as much (or more than) 365HP from 2.5 liters, naturally aspirated.

Markus Glaum in Germany has kindly provided these photos of a genuine set of DTM slide throttles2 for us to look at:


E30 M3 S14 Slide Throttle Bodies

E30 M3 S14 Slide Throttle Bodies

E30 M3 S14 Slide Throttle Bodies

E30 M3 S14 Slide Throttle Bodies

E30 M3 S14 Slide Throttle Bodies

These next few photos clearly show the throttle slide plate and the way it retracts from the intake path:

E30 M3 S14 Slide Throttle Bodies

E30 M3 S14 Slide Throttle Bodies

E30 M3 S14 Slide Throttle Bodies

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