StoneBridge & K-Syran - Starry Night

Herbert Ampferer is Austrian, and as soon as he finished his engineering studies at Steyr, his only thought was to get away to avoid military service which, 25 years after the war, had become extraordinarily unpopular. “I went to Sweden – thought I might find engineering work there. One evening I met a fellow Austrian in a bar in Stockholm, and over a beer I said to him I had two priorities: a girlfriend and a job.

“He thought he could help with the second and suggested that a sports car company in Stuttgart where he worked could probably find a place for me. It was called Porsche. I had never heard of it, but within a few weeks I had swapped Stockholm for Stuttgart and found myself employed at Zuffenhausen. I went straight into the engine department. I liked it immediately because of its ‘Austrian’ atmosphere.”

This was just as well because his first task was Entwicklungsauftrag EA 266, the project to build a small VW with an air-cooled engine beneath the rear seat: “It was horribly complicated,” recalls Ampferer. “Bent drives, drives running round corners… unbelievably complex.” It was a relief to move to the 924 project, intended as a joint venture with Audi which Porsche ended up taking over. In doing so it inherited the VW water-cooled four-cylinder engine: “It was a high-compression OHC unit with a long stroke that gave good mpg. But the cast-iron block was heavy. It was the beginning of Porsche’s learning curve with in-line water-cooled engines.”

It was the beginning of Ampferer’s learning curve too; the Audi unit would be reworked: “We put in a forged-steel crankshaft and extra-large main bearings, and we used screws for valve adjustment rather than Audi’s shims; we cut recesses into the pistons to avoid damage if the cam belt broke. We also had to redesign the manifold to fit the 924’s limited space. A deep sump kept the engine height low, and I finned it, which saved fitting an oil cooler.”

As well as working on all versions of the 924, including the GT, he would go on to develop the 2.5 for the 944: “A very interesting project that was much more than just half a 928 engine. We had to design the 2.5 to fit the front suspension. The inspiration for the balancer shafts came from Mitsubishi; they added 12kg, but there was negligible additional friction. We built a prototype 924 engine with balancer shafts – you’ll find my signature on the first drawings of them!”

Chief of the engine department was Robert Binder; he recognised the young Ampferer’s raw talent early and put him to work on turbocharging. At that stage in early 1973 Porsche was studying the use of turbochargers – proving so successful in the Can-Am 917 racers – in road cars. “Valentin Schäffer had already done most of the development on the racing turbo. My job was to draw the concept for the road cars. The main difference is packaging: racing cars are open everywhere, so heat dissipation isn’t difficult, but acceptable styling for road cars meant we had to find ways of defusing this heat. There was also the problem of drivability – a racing car has the throttle either wide open or closed, but for road use you need part throttle openings. The turbochargers we had then were basically made for diesel engines, and they were not readily mappable to the requirements of petrol. When we had gone as far as we could with that, we then had to design the wastegate to retain exhaust pressure within the system so that when the throttle was released, the turbo did not stop turning.”

For the full interview with engineer Herbert Ampferer on Weissach’s secrets, pick up your copy of Total 911 issue 176 in shops now or get it delivered to your door via here. You can also download a digital copy with high definition bonus galleries to any Apple or Android device.