Tuning Topics

Turbocharging American Style From the Fifties to Today

The use of turbochargers in European road or track cars has been a comparatively recent development, though the original principles of placing a compressor in the path of outgoing exhaust gases has been evident since 1903. Then the idea was to extract extra performance from heavy engines like marine or factory applications.

Today interest in the turbocharger is at an unprecedented level and the signs are that many companies are looking to the turbo either to solve problems set by legislation (how to get power and pass emissions requirements); to make the diesel car a lot more competitive with quieter, improved, performance, or simply to rescue an aged car range from extinction before a revised model can be introduced.

Today we have turbocharged cars from Porsche (in fact Stuttgart have two examples; for soon we shall have the 924 as well in the UK), Saab, Ford Mustang, TVR, Buick and so on. Current production turbo diesel cars include models front Mercedes, Peugeot and Oldsmobile, the Mercedes diesel is part of Unterturkheim's commitment to improving consumption across the range of models available in the USA, while maintaining technical progress.

Working on turbo applications for introduction shortly in various roles are VW-Audi, Alfa Romeo and BMW. The VW group have produced a very nice prototype diesel turbo Golf (which we drove a couple of years ago) and are currently enmeshed in petrol-diesel research. Evidence for this programme lies in a number of prototype Scirocco-turbos at Wolfsburg, but they still have not had the courage to actually launch this now thoroughly developed "little flyer". Another group of engineers within the group are working hard on producing a turbocharged five-cylinder Audi. Such an engine would be proved in rallying use within a four-wheel-drive version of the new Audi 80 coupe, according to rumours from Germany. Then Audi are expected to head straight for the more luxurious market with the 200 and 300 series, all with front-wheel drive. I understand the 200 series will be launched in the autumn this year and that it too will have five cylinders with turbocharging.

Renault have done more for the prestige of the turbocharger outside America and inside motorsport with their Formula One cars and Le Mans winner last year. Even the adoption of twin turbos does not seem to offset their inherent 1 1/2-litre handicap on a circuit such as Monaco though, so we shall have to wait a little longer to see if this aspect of motorised sport will follow the turbo trend. It looks unlikely unless the turbo engine capacity is increased . . .

Another company with turbochargers and rallying in mind is the Autodelta concern. They have already put together a number of Alfetta GTV prototypes with exhaust gas boosted versions of the classic DOHC 2-litre, one of which provided Niki Lauda with some interesting motoring last year, before the factory came to take away the steaming remains! I was told earlier this summer that Alfa would contest a mainly European rally schedule with such cars, which would go on sale in Germany as the limited production run basis for their international homologation. Germany is the obvious place to market such a car, but it's interesting to note that Alfa Romeo also chose the KKK turbocharger. Saab are already committed to the turbocharger in rallying through their production vehicles.

BMW? We were semi-officially told that the Frankfurt Show in September will see the debut of a new 7-series saloon to top the saloon car range with a turbocharger fitment. Apparently the plan is not to do the same for the sportier coupe 6-series at present, for the saloons face the stern task of facing up to whatever the new S-class Mercedes brings next year.

In competition terms the turbo reigns supreme and unchallenged in USAC/CART American single-seater racing (usually attached to the Cosworth DFX today, we are glad to say) and in long distance events for Group 5 and 6 prototype machinery Porsche, Lancia and BMW would not dream of venturing a competitive car without one, or in Porsche or BMW's case, even two turbos.

So that is the situation in Europe, but recently we spent most of a day in a London hotel listening to an American present a very interesting talk on the turbo's progress in his homeland, since the fifties.

The American speaker was Hugh MacInnes, formerly of Garrett AiResearch and now of Roto-Master who reside in North Hollywood, California, but are represented in Britain through a company of the same name, based in Huddersfield.

MacInnes begun his dissertation by looking back to the 1952 Indianapolis 500. At that year's event the fastest qualifying time was put up by "a Cummins JT small truck diesel engine of 406 CI which was known as the JT motor. That diesel would turn 4,000 r.p.m. in a race with a turbo unit that weighed maybe 115 lb. and had the compresson/impellor unit fully shrouded. In the race the car picked up all the dirt of the track into the main airflow feed to the turbo and wiped-out all the bearings. But they had proved something, that a turbo truck engine could compete with a racing engine.

"Back in the fifties the equation went something like this. You could have a motor that gave 200 horsepower and weighed 2,300 lb., or you could have the same 200 b.h.p. from a smaller engine weighing maybe 950 lb. with a high boost turbo. That was the sales pitch, plus the fuel economy."

MacInnes explored how the difficulties encountered with conventional engines at altitude provided openings for the early turbo specialists like AiResearch. "At 10,000 ft. a normally aspirated gasoline engine will give some 70% of its true maximum power. With a turbo on, you can reach 7,000 ft. and, with a mild boost, the power is the same as at sea level. You can go to 40,000 ft. with a lot of boost and still have sea level power!" Aside from the obvious implications for the aviators, AiResearch also managed to sell one civil engineering concern a turbo installation for their high-altitude activities crushing rocks. "It worked so good, the damn rock-crusher broke," MacInnes concluded laconically.

By 1956 MacInnes was leading us through the intricacies of turbo selection based on the size of housing and its internal shaping. Basically, the bigger the unit the slower the response, but the more ultimate pressure can ultimately be generated. Then there was the late fifties revolution in bearings for turbos, taking in the use of fully floating bearings that rely purely on oil contact and the more common semi-floating bearings that were installed in Cummins, Roto-Master, Schwitzer, Holset and KKK units, the wall thickness of the bearing taking thrust. "So with this kind of semi-floating bearing the housing can be in alloy, but with a fully floating bearing the iron housing is still necessary," reported Mr. MacInnes.

For those who wish to explore the subject of matching turbochargers to a pre-conceived engine size, or those that simply want to read a practical guide to turbocharging for the sensible layman, I would recommend Hugh MacInnes' book "How to select and install Turbochargers," published by HP Books in the USA. It has a commercial bias from the author's background and does not cover the present European scene, but it is a sound starting point in some of the basics that do not occur to you unless you have the job to do yourself!

Back at the history lesson MacInnes recounted his story of how the World's first turbo petrol mass production car came to life. "In 1960 at GM they were testing the flat six engine used in the Corvair: 'a real dog', was Bill Mitchell's feeling about this engine." Why the chief of styling was telling the engineers how lazy their engine was is not for us to conjecture for, as MacInnes recalled,"he had some friends at the TRW speed business, and they put on a twin barrel Solex with a turbo on top: they chose Solex because you could get so many jets for it. Anyway TRW sent this set-up to GM to the chief engineer at Chevrolet. He had better things to do than listen to what the head of styling had come up with! So they reluctantly ran this Corvair-turbo on the bed . . . and the result was 150 b.h.p. at 4,000 r.p.m.

"That engineer just kept jumping up and down - they had never had more than 67 b.h.p. before! He just kept dragging people in out of the corridor and inviting them in to see this motor run!

"They put a Carter carburetter on for production," Mr. MacInnes remembered, adding that it was February 1962 when Chevrolet announced the 150 b.h.p. Corvair Spyder with its top-mounted turbo unit and tube feed to each bank: no wastegate was fitted. Oldsmobile were subsequently allowed to follow their GM brother into the turbo mass-production car field but MacInnes felt that "the Olds was too complicated: it just scared any mechanic away when the hood was lifted!" Sophistications that Oldsmobile introduced included a wastegate, water cooling and alcohol injection, with a third automatic carburation butterfly in case the wastegate tailed and over boost occurred.

By 1966 55,000 such turbo cars had been built in the US. "gas was 22 cents a gallon," and the big liquid cooled engines gave enough performance. Chrysler and Ford also investigated turbos in the early sixties, primarily through the tuning industry, according to MacInnes, who showed us some slides of big V8s with sophisticated twin turbo installations on as well as more straightforward conversions on the massive engines of that era.

Maclnnes then looked at other turbo applications today including those of the early 60s for the twin engine Piper Apache, the turbo allowing sufficient single engine power for safe emergency single engine flight. Rayjay appeared to be the pioneers in this field, but MacInnes did pay tribute to the work carried out on World War II bombers, though. as he said, it took a compressor wheel of some 18 in. in diameter to feed enough boost through to keep one of these monsters happy at 30,000 ft. We then goggled at a slide of a 50 m.p.h, powerboat equipped with four V8 engines, each of which could be de-clutched. Each of them was equipped with two turbochargers: try and locate the misfire in that little lot!

We were left with the assurance that tractors had been the biggest users of turbochargers until the recent upswing in popularity of turbos for passenger cars. To support the tractor story we were shown a film of a televised tractor weight and distance pulling contest in the American midwest. One typical installation on a John Deere diesel special had three turbochargers and two intercoolers "and a lot of ice and water," as Mr. MacInnes put it.

In action these monsters take off (well halfway, just the front wheels paw the air under full power) to the blare of their straining Allison V12s and the encouragement of both their portly owner-drivers and the crowd. It is a kind of drag racing with the vehicle pinned by enormous loads at the rear. One contestant described his engine's potency as "Well, we're meant to have about 2,500 horsepower right now, but I guess we've only got around 2,000 today!"

Turning to drag racing MacInnes obviously felt strongly: "Turbo lag is the invention of those who don't know enough." He cited the case of various drag racing Corvairs that were successful, ''beating allcomers at 110/112 m.p.h. in the quarter, and that means beating equal horsepower cars with normal aspiration engines." MacInnes felt that the only reason turbos had not caught on at the very top of drag racing - the fastest cars have Roots principle superchargers still - was that the top teams were too deeply committed to the supercharger and their big Chrysler-based V8s, though he was unusually confident that the day of the turbo would come to this branch of motorsport too.

He traced the present revival in interest in turbos in America to the aftermath of the fuel crisis, and the consequent interest in smaller cars and engines, pointing out that Bobby Unser's winning performances at Indianapolis in the late sixties had already pointed the way to the racing future ten years ago, and more.

An interesting selection of slides showed how Chevrolet had commissioned three tuners in an attempt to overcome the emission-strangled problems of the 1972 5.7-litre V8 via turbocharging. The answer was 200 b.h.p. or more from these specialists but the engines looked a nightmare for service with both turbocharging and emission-control equipment, sprawling lines, tubes and gadgetry across the huge engine bay.

Towards the close of this lecture we also saw how motorcycle turbocharging was proceeding in the USA, including the assertion that a Kawasaki 903 in street trim had proved capable of 150 m.p.h. in a quarter-mile from rest!

Finally Hugh MacInnes looked over the current car offerings on the American market with a quietly scathing aside about the Mercedes 300SD at the equivalent of £17,000, a word for Buick's V6 with wastegate and spark retard devices and the prophesy that 1980 would see the Mustang turbo joined by models from Audi, BMW and Pontiac.

It was a fascinating skip across a subject that is occupying motor manufacturers and the 50 plus specialists in this field in the USA at present. — J.W.