- 1969 Porsche 917 Kurzheck Coupe engine

The Birth of Porsche Turbo

Porsche perfected the application of turbocharging in the production of road-legal cars, made it reliable, and good enough to use on an everyday basis.

32w ago
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Ferdinand Piech, the ever-ambitious engineer and the head of Porsche racing development, was planning to dominate the World Motorsport Championship events.

In mid-1968, Valentine Schaffer and Hans Mezger were working on a new 180-degree V12 engine to power a prototype race car developed by Ferdinand Piech's ambitious racing department. The new engine was to power the car that was intended to compete in the World Manufacturers Championship in the coming years.

Hans Mezger developed a new engine for the Porsche 917 derived from the 3.0-liter eight-cylinder Type 908 engine. What Hanz Mezger did was combining a Type 908 engine with another half of a Type 908 engine to create a 4.5-liter V12. The power output was 520hp. This engine was designated as Porsche Type 912/00.

The head of internal project designation management, Karl Rabe decided to label the new engine as Type 912 to confuse the competitors and suppliers to make them believe that the project was all about some series production model.

1969 Porsche 917

1969 Porsche 917

The new Porsche 917 race car was unveiled at the Geneva Motor Show in early March 1969, and it was intended to compete in World Endurance Championship events. This same car won the 24 Hours of Le Mans event and effectively broadcasted Porsche's intentions to the motorsport world.

With Porsche 917, Porsche won the 24 Hours of Le Mans in 1970 and 1971.

Porsche 917 engine

Porsche 917 engine

The Commission Sportive International (CSI) had authorized a Group 5 category for endurance racing events. To qualify for the 1971 and 1972 racing seasons, it required the manufacturers to make at least 25 identical cars with a minimum curb weight of 1760 pounds per each. The maximum engine displacement was limited to 5.0-liter.

Hans Mezger developed the 4494cc Type 912/00 engine packing 520 horsepower. Further development was done to increase the maximum power output of the engine.

Engine displacement was eventually increased up to 4907cc, now the engine was designated as Type 912/10. Type 912/10 engine delivered a maximum power output of 600hp at 8300rpm. It was further enlarged to become the Type 912/11 engine.

Type 912/11 4999cc V12 engine delivered 630hp maximum. This engine was used to compete in 1970 and 1971 24 Hours of Le Mans events.

Commission Sportive Internationale (CSI) then decided to end the dominance of Porsche by restricting the engine limit to 3.0-liter for the 1972 24 Hours of Le Mans.

Ferdinand Piech and Ferry Porsche decided to focus on the Canadian and American Challenge Cup. This is an event organized by the Sports Car Club of America (SCCA) and due to its popularity, SCCA organized its European equivalent called Interserie from 1970 onwards.

SCCA had no restrictions on engine displacement or specific aerodynamic aids featured in the bodywork, and Porsche decided to fully exploit the opportunity to make a name for themselves in the Interserie event. SCCA specified that the competing cars must have enclosed wheel bodywork and two-seat layout to qualify for Group 7 events.

Hans Mezger decided to further increase the displacement of their Type 912/10 V12 engine. Now the engine displacement of the V12 was 5347cc and it was internally known as the Porsche 912/12. Power delivery maxed at 660hp at 8300rpm.

In comparison, the Lola, Ford, and McLaren were powered with bigger engines, and by the 1970 racing season, most of the competitors were using 8.0-liter or larger engines and the power delivery was somewhere between 650hp to 700hp.

1971 Porsche 917K

1971 Porsche 917K

Ferdinand Piech with the financial backing of Gulf, ran Porsche 917K coupes in the Can-Am and six hours of Glen. Porsche 917 Spyder driven by Stiffer won second place in the Can-Am event, 28 seconds behind a McLaren driven by Denny Hulme. Two Porsche 917K coupes driven by Richard Attwood and Vic Elford achieved the third and fourth overall places.

Ferdinand Piech being himself, wasn't pleased with the results and asked Hans Mezger and Valentine Schaffer to develop an even more powerful version of their V12 engine. This led to the development of a new V16 engine. What Hans and Valentine did was adding two pairs of cylinders to each end of the V12 engine.

The all-new V16 engine delivered 760hp maximum, not enough to compete against McLaren. Ferdinand Piech insisted that Hans Mezger should press on to squeeze more power out of it. Despite every method tried by Hans Mezger and Valentine Schaffer, it wasn't a possibility.

Porsch 917 Spyder

Porsch 917 Spyder

Porsche 917 Spyder was equipped with the new V16 engine. It was test-driven by Porsche team driver Willi Kaushen, who went on to achieve a new lap record at Weissach test track. However, he experienced serious body roll and rattling, therefore suggested that the chassis needed extra strengthening to cope with the improved power delivery and torque. Eventually, it was decided that the engine was too heavy for the chassis of the Porsche 917 Spyder.

D​evelopment of the Porsche 917-10 Spyder

Helmut Bott and Ferdinand Piech decided to make a new turbocharged variant of Type 912. Hans Mezger was tasked with seeking expert advice on turbocharging, a technology widely used in the aerospace industry.

He came across a company called Eberspacher, barely 10 miles from Zuffenhausen. Eberspacher had been in the turbocharging business since 1947 and since Ferdinand Porsche told him to be discrete about this project, he was told not to tell about this to anyone. To accomplish this task, he told the Eberspacher workforce that he needed at least 800hp and nothing more.

Eberspacher staff believed that this all about a speed boat engine and recommended using the two largest turbochargers they had.

Hans Mezger came back to Weissach with two turbines, and he teamed up with a mechanic to concentrate on intakes and exhaust. Since Ferdinand Piech asked them not to tell anyone about this project, Hans Mezger and Valentine Schaffer had to rely on their own expertise and intuition to make things work. Ferry Porsche had observed his father, Ferdinand Porsche designing an air-cooled turbocharged sixteen-cylinder diesel engine for German war tanks about a decade ago.

Ferry Porsche, Ferdinand Piech, Hans Mezger, and Valentine Schaffer kept working on the turbocharged engine, but the boost was uncontrollable and resulted in blowoff.

Valentine Schaffer left the team to participate in the pre-testing of Porsche 917 racers that were being prepared to compete in 12 Hours of Sebring. Gulf-sponsored cars were taken to be dyno tested at their dynamometer lap at their Pittsburg headquarters, and Valentine Schaffer was invited to witness the process.

Gulf sponsored Porsche 917 cars finished the 12 Hours of Sebring with fourth and fifth overall victories. Valentine Schaffer was asked to revisit them before the next endurance racing event in the USA, and he came back to Germany and resumed his efforts on the turbocharged engine.

Valentine Schaffer and Hans Mezger had to work with bare minimum tools and they used a 2m tall pipe filled with mercury to measure the pressure of the exhaust gases. They measured only on the intake because, every single time they started the engine, the internal pressure blew all the mercury out of the 2m tall pipe and onto the ceiling, raining down on their heads. Eventually, Valentine Schaffer decided that they should measure exhaust-side pressure by drilling holes in the pipes.

They went on to perform periodic tests with more holes, easing on the throttle, measuring, and recording each increment. After several weeks of continuous testing, they decided that it works but there was always room for improvement.

Valentine Schaffer returned to the USA to race prepare the Gulf-sponsored Porsche 917 cars and this time they had twenty-five active dynamometers at their disposal. Engineers tested a turbocharged inline-four Offenhauser and Valentine Schaffer realized that they had some weird mechanical component in the turbocharging system. An engineer explained to him that it was a wastegate that they were using to get rid of extra exhaust pressure.

He returned to Germany with a wastegate that he purchased from the Offenhauser engineering team and applied it to the system that they were testing. Suddenly, the turbo boost became manageable. Soon Hans Mezger and Valentine Schaffer began working on their own wastegates and eventually developed lightweight yet more efficient wastegates.

The turbocharged 4494cc V12 engine was now internally designated as Type 912/50. It produced 850hp at 8800rpm. Eventually, this engine was equipped in a new Spyder variant of the Porsche 917 called Porsche 917/10.

1972 Porsche 917-10

1972 Porsche 917-10

Porsche factory racing team manager Roger Penske and his team driver Mark Donohue were asked to fly back to Weissach to test the Porsche 917/10 prototype.

Mark Donohue stayed at Weissach for an entire week, test driving the Porsche 917/10 working with Valentine Schaffer on improving the engine and Helmut Flegl on chassis, suspension, and aerodynamic improvements.

Regular tests and development made them more confident due to the steady improvements in terms of handling and speed.

Eventually, Porsche 917/10 was unveiled at Motorsport International Raceway outside Toronto in 1972. Porsche 917/10 ran four seconds quicker than McLaren's lap record on its first day. Many competitors disregarded this as a rumour, but the next day they were the fastest at qualifying. Mark Donohue raced ahead of others and soon build up an impressive lead and kept on his lead until the end of lap 18. On the 19th lap, he came back to the pits and told them that there was no boost at all. While Valentine Schaffer and his engineers investigated the usual possibilities, the rest of the competitors went on to lap Mark Donohue thrice.

Finally, Valentine Schaffer disassembled the engine and realized that the special throttle that opens to allow the turbo work has stuck open due to extreme heat generated during the racing, thus resulting in no boost at all. So, he asked for a hammer and banged it on both sides until it released.

Mark Donohue went on to lap McLaren driver Peter Revson twice and Denny Hulme almost twice, finishing seconds behind Hulme on the same lap. Porsche team drivers Miltt Minter and Peter Gregg finished the race with fourth and fifth overall places.

Mark Donohue had a massive crash while testing the car at Atlanta before the season's second race. With him being hospitalized, Roger Penske hired George Follmer to do the driver's duty behind the wheels of Porsche 917/10. George Follmer previously competed in 1967 Can-Am for his team.

1​972 Porsche 917/10

1​972 Porsche 917/10

It took George Follmer to get familiar with the car as he has never before driven anything with that sort of power, which he estimated to be 850-900hp.

However, his car was equipped with a Type 912/51 engine with many improvements, resulting in a maximum power output of 1000hp at 7800rpm.

Proving his skills as a professional driver, he got used to the car, and at the practice race for Sunday's race, George Follmer went on to set the fastest lap time in the qualifying race.

George Follmer won the Atlanta event with a lead of a full lap over the Denny Hulme.

By September, Mark Donohue was back to his usual shape and assumed his driving duties for the Porsche racing team. Roger Penske got him another car because George Follmer was on his way to claim the 1972 Can-Am Driver's Championship. He won the two final events in California, winning the 1972 driver's championship.

P​orsche 917-30

Mark Donohue, Helmut Flegl Valentin Schäffer, and Hans Mezger were working full time on the next generation of the Can-Am Spyder. This project was called 917/30.

1973 Porsche 917 30

1973 Porsche 917 30

Porsche 917/30 received a variable wheelbase, an invention of Helmut Flegel. Now the wheelbase was 98.4, almost eight inches longer than the previous 917/10. This helped much to stabilize the car.

Hans Mezger and Valentine Schäffer were working on further improving the engine. The engine was now developed into 917/52. The displacement was increased up to 5374cc.

By 1972, the Eberspacher turbocharger company was absorbed into Kühnle, Kopp & Kausch A. G. Soon, the new management introduced the KKK turbocharger series. Porsche further strengthens their relationship with the Kühnle, Kopp & Kausch A. G.

In October 1973, with OPEC enforcing an embargo on oil supplies, the economies of the European Union, and the USA suffered a serious blow and as a consequence, many nations enforced strict restrictions on oil to keep the demand low as possible.

SCCA canceled its 1974 Can-Am series after five events due to the lack of spectators as well as the decisions of manufacturers and sponsors to abandon racing events to keep the costs down. In 1977 the Can-Am Series was continued.

P​orsche 917-30

P​orsche 917-30

In the meantime, Porsche focused on the European Interserie rally series, equality of the SCCA series. Porsche driver Herbert Muller in a prototype Porsche 917/30 -001 won the championship in 1973, 1974, and 1975. Porsche withdrew from Interserie as they have proven their point.

2​21mph Record-Breaking Porsche 917-30 003

Donohue's experience with the twin-turbocharged Porsche 917/30 convinced Porsche engineer Roger Penske that the car hasn't reached its full potential.

In 1975, Roger Penske teamed up with Helmut Flegel, Valentine Schaffer, Hans Mezger, and Mark Donahue to attempt a world speed record run on a closed circuit.

Roger Penske and Mark Donahue had previously tried such an attempt in March 1972 at Daytona with Penske's naturally aspirated Ferrari 512. The 2.5-mile oval track at Daytona is the longest closed oval track in North America. The 31-degree banking elevation within the 1st and 3rd turn makes it the steepest. They achieved 199mph top speed, establishing a new track record the wasn't beaten until two years later when the Dodge NASCAR team achieved 201mph top speed in the hands of a Talladega.

Since the Porsche 917/30 was designed to run on closed track events, it was given a lot of aerodynamic downforce, and a big amount of power. Despite the higher amount of power, and downforce to keep the car planted to the ground, the top speed never exceeded much over 200mph. The solution for this was the aerodynamic drag of the car.

Helmut Flegl returned to the task of reshaping the body of the car to reduce aerodynamic drag even further.

The engine overheating issue lead to complete engine destruction at their second attempt to set the world speed record. Mark Donohue informed Valentine Schaffer regarding this issue. It was evident that the engine wasn't suitable for a third record attempt and that it wasn't powerful and strong enough to withstand two laps of full open throttle. The cooling system for the engine was also not adequate, requiring lifting the engine lid to let it cool.

Valentine Schaffer advised Mark Donohue to use a 5.0-liter engine as it was much stronger. This engine had more cylinder wall thickness, better cooling, and small cylinders. Despite not being powerful as the previous engine, it could withstand more boost pressure according to Schaffer.

Mark Donohue then asked for a new intercooler design, and Schaffer received a drawing by Mark depicting a system built by a California-based supplier, kinergetics, Inc. The drawing was a plan for an aftercooler system for a turbocharger, to be installed vertically below the car body.

However, the proposed system had long insulated hoses from the intercoolers to intakes. This can result in a significant lag between the throttle inputs and engine reaction. But, this was not a problem for throttle happy Mark Donohue as he never lifted his feet until he achieved the top speed.

Valentine Schaffer has previously used an intercooler system on a prototype before. After testing for some time, Schaffer discovered that he can keep the engine temperature much lower than before by placing the cooler behind the engine rather than placing it on the top and turbocharger on the top instead of being in the bottom. This allowed him to further increase the power output of the engine.

Helmut Flegl and his team then began fabricating intercooler platforms behind the 5.0-liter engine. The team then came up with a revised Can-Am nose, tonneau cover to cover the passenger seat section, and fitted flat wheel covers to improve aerodynamic efficiency. The suspension system was strengthened to cope with extra stress.

The intercoolers were cooled using the air taken in through the tunnels on the surface of the rear deck.

Porsche 930 30 003 driven by Mark Donohue. Image credit goes to Porsche

Porsche 930 30 003 driven by Mark Donohue. Image credit goes to Porsche

The Porsche 917/30 003 packed 1100 horsepower when the air ducts were filled with ice to keep the engine temperature even low.

On August 9, 1975, Mark Donohue attempted the world speed record run at the Talladega Superspeedway in Talladega, Alabama, after several previous attempts. With this day being colder and it was about to rain when he raced, he didn't ease on the throttle and ran the car around the Talladega straight in 43 seconds with an average speed of 221mph.

With this new record, it was evident that Porsche has implemented a practical, reliable, and proven turbocharging system for its cars.

This newfound technological advancement allowed Porsche to cement a legacy that is legendary by its own rights.

The Porsche 917-30 with its dominance of the Can-Am series was now nicknamed as the Can-Am Killer.

As for Mark Donohue, things only got worse.

After his successful record-breaking attempt at Talladega Superspeedway in Alabama just a few days earlier, he had arrived in Austria to compete in the Austrian Grand Prix at the Österreichring race track.

During a practice session for the race, Mark Donohue lost control of his March 751 following a tyre failure, sending him into the catch fencing at the fastest corner on the track.

The debris from the accident killed a track marshal called Vöest Hügel Kurve. At first Mark Donohue was thought to be unharmed, but it is said that his head struck either the bottom of the wood frame for an advertising billboard located alongside the track or a catch fencing post.

Mark Donohue went to the hospital the next day to get treatments for his worsening headache, only to be lapsed into a coma due to a cerebral hemorrhage. He died on August 19, 1975, at the age of 38. His son David Donohue now races Porsche 911 variants in the annual Pikes Peak Hill Climb event.

Reference

Porsche Archives

treksamurai.com/1972-1973-porsche-917-10-and-porsche-917-30/

treksamurai.com/1969-1972-porsche-917k-and-porsche-917l/

W​ikipedia

rrdc.org/

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