I might well be the only person here who’s even slightly interested in the following, but on the offchance, here goes. The Mercedes C111, shown above, was an experimental car that was used to attack a series of world records for diesel powered cars back in 1978. It was fitted with a standard 5 cylinder, 3 litre diesel engine, similar to those found in all those cabs and passenger cars that you see everywhere, I’ve owned three. I’ve long been a diesel fan and ever since this event I’ve been curious about it and some years ago I wrote this piece; what intrigued me was that though they came incredibly close, they were never able to break the 200mph average speed record though they came within .0055mph of doing so, but that record eluded them.
Now pay attention back there, this is dull and uninteresting and it might require a little concentration, turn on the music if it helps. It’s a piece from that era that the drivers might have been listening to, assuming someone thought to fit a cassette player in the car.
Autobahn – Kraftwerk

The 1978 Mercedes-Benz C111-III in pursuit of diesel world records at Nardo.
Daimler-Benz set out in 1978 to demonstrate the power potential of the diesel engine on the lightly banked 12.6-kilometer circuit at Nardo, Italy on April 29/30. The C 111-III car, which had been optimized not only in aerodynamic terms, with a sensational drag coefficient of 0.195, was fitted with a three-liter five-cylinder diesel engine developing 230 hp with exhaust turbocharger and intercooler. Nevertheless, it consumed an average of only 16 liters of diesel fuel per 100 kilometers. In the course of the 12-hour record-breaking run, six world best performances were clocked up over distances from 100 kilometers to 1000 miles, with a further three best performances over 1, 6 and 12 hours. Over the entire 500-km distance, an absolute top average speed of 321.860 km/h was measured for this record-breaking car which was designed for speeds of up to 325km/h.
The drivers were Rico Steinemann, Paul Frere, Moch and Dr. Hans Liebold and records achieved during the 12-hour record drive were:

100 km at 316.484 km/h
100 miles at 319.835 km/h
500 km at 321.860 km/h — ie 199.99453 mph.
500 miles at 320,788 km/h
1000 km at 318.308 km/h
1000 miles at 319.091 km/h
1 hour at 321.843 km/h
6 hours at 317.796 km/h
12 hours at 314.463 km/h

Some technical data:

Manufactured in 1978, a 5-cylinder inline OM 617 A, placed before the rear axle, longitudinally and standing upright, a four-stroke diesel with pre-chamber injection, a mechanically operated Bosch injection pump, turbocharger and intercooler, bore x stroke 90.9 x 92.4 mm, 2999ccm = ca. 183.2 cu in, compression 1:17.5, maximum power output 230 PS (NOT 320 PS!) = 169 kw at 4.200-4.600 revs, maximum torque 403 Nm at 3.700 revs, engine block made from grey cast iron, cylinder head made out of light alloy, detachable, 2 valves per cylinder, one overhead camshaft driven by duplex-chain, firing order 1-2-4-5-3, one glowplug per cylinder, electrical Bosch starter, vented disc brakes front and rear, rear-wheel drive, double plate dry clutch, ZF 5-speed manual transmission with integrated axle drive, central floor shift, recirculating ball steering, length 5380 mm [17.6ft], width 1715 mm [5.62ft], height 1045 mm 3.42ft], car weight 1400 kg [3086 lb], engine weight 244 kg [538 lb], one seat place, fuel tank 140 litres [37 gal], top speed 325 km/h = 202 mph, ((other sources report a top speed of 327.3 kmh = 203.4 mph)), drag coefficient 0.183, another DC source says 0.195, diesel consumption was ca. 16 litres/100km = ca. 17.6 mpg UK = ca. 14.7 mpg US.

You will notice that all those records were above 314.463 km/hr [195 mph] and that the highest average speed attained was for 500 km, 321.860 km/hr, ie 199.99453 mph. The average speeds declined after that to 198.273 mph for 1000 miles and to 195.398 mph for 12 hours. No matter how hard they tried, their lap speeds dropped every lap ’til the end, they were unable to break the 200 mph average speed barrier.

So the question is why were they not able to do so even though the cars max speed was 325 km/hr – [202 mph] and the car constantly lost substantial weight due to fuel usage and what simple modification to the engine would have allowed them to break the elusive 200 mph average barrier?