PORSCHES UN­DER PRES­SURE

Clas­sic Porsche re­counts the story be­hind Porsche’s leg­endary Tur­bos

Classic Porsche - - Contents - Words:keith Seume Photos: Porsche Archiv and KS col­lec­tion

T urbo – the very word con­jures up an im­age of power, be it in the form of Porscheʼs mus­cle­bound, wide-arched 930 coupé or the mighty 917 Can-am rac­ers driven to vic­tory by the likes of Mark Dono­hue and Ge­orge Fullmer. To­day it seems just about ev­ery other car on the road is tur­bocharged, be it a tiny Tdi-badged hatch­back or a Tar­ma­c­shred­ding su­per­car. But it has­nʼt al­ways been that way.

Tur­bocharg­ing as a way to ex­tract power from an in­ter­nal com­bus­tion en­gine has been with us since 1905, be­lieve it or not, when Swiss en­gi­neer Al­fred Büchi took out a patent for an ex­haust-driven su­per­charger. Ten years later, a tur­bocharged Lib­erty aero en­gine was dynoʼd at 360bhp, com­pared to just 220bhp of its nor­mally-as­pi­rated coun­ter­part. Pretty soon, tur­bocharged en­gines be­came widely ac­cepted in avi­a­tion cir­cles.

How­ever, it was­nʼt un­til 1962 that the first pro­duc­tion car pow­ered by a tur­bocharged en­gine was launched: the 215bhp Oldsmo­bile Jet­fire. This was fol­lowed soon af­ter by Chevro­letʼs 152bhp Cor­vair Monza, launched in 1962 and still in pro­duc­tion in 1966 as the 182bhp Monza Corsa. But wide­spread ac­cep­tance of the tech­nol­ogy in rac­ing cir­cles would take a lit­tle longer.

The first ap­pear­ance in Can-am of a tur­bocharged car was at St Jovite in 1969, when Joe Leonard fin­ished eighth in the wedge-like Mckee, us­ing a twin-tur­bocharged 389ci (6375cc) iron-block Oldsmo­bile en­gine. This gave his team the con­fi­dence to de­velop the con­cept fur­ther, en­ter­ing two new cars at Elkhart Lake. These amaz­ing ma­chines also fea­tured a chas­sis from Mckee, with new 455ci (7456cc) al­la­lu­minium en­gines, two-speed au­to­matic gear­boxes (with hi­and low ra­tios, to give four speeds) – and four-wheel-drive. Sadly, the cars were plagued with brake prob­lems and never turned a wheel in anger, a lack of fi­nances bring­ing the project to a pre­ma­ture end. But the die had been cast: tur­bocharg­ing had left its in­deli­ble mark on Can-am, a point that had not been lost on Porscheʼs engi­neers.

Porsche had what ap­peared to be the per­fect en­gine avail­able in the form of the Type 912 (def­i­nitely not to be con­fused with Porscheʼs four-cylin­der coupé…), a 630bhp 5.0-litre flat-twelve de­vel­oped for the 917 en­durance rac­ers. You could be for­given for think­ing that 630bhp in a car weigh­ing just 1638lbs would be enough to force the op­po­si­tion to eat Porscheʼs dust, but arch-ri­val Mclaren boasted in ex­cess of 700bhp from its fuel-in­jected Chevrolet en­gines, and con­sid­er­ably less weight. Porsche needed to go one bet­ter.

There were two op­tions avail­able, the first be­ing to in­crease the ca­pac­ity of the mo­tor, but the Type 912 en­gine had al­most reached its lim­its – the 86.8mm Nikasil-coated cylin­ders were al­ready tight up against each other, leav­ing lit­tle scope for in­creas­ing the bore. Us­ing 90mm pis­tons and cylin­ders, the ca­pac­ity could be in­creased to 5374cc, which saw the power out­put rise to 660bhp – bet­ter but still not enough to trounce the Mclarens.

Porsche also in­ves­ti­gated the con­cept of stretch­ing the 12-cylin­der Type 912 mo­tor even fur­ther by adding four more cylin­ders – in fact, they built 10 flat-16 pro­to­type mo­tors, rang­ing in size from 6.0- to a whop­ping 7.2-litres. The lat­ter pro­duced some 880bhp on the dyno, the­o­ret­i­cally more than enough to dis­pense with any­thing Mclaren had to of­fer. But it was a big en­gine – very big – and Penske-porsche driver Mark Dono­hue quipped that you could hear one end of the en­gine start be­fore the other. How­ever promis­ing the flat16 may have looked, its devel­op­ment was ter­mi­nated in favour of op­tion two…

It was clear that tur­bocharg­ing was an ob­vi­ous way to make sig­nif­i­cant power in­creases, but what made tur­bocharg­ing par­tic­u­larly at­trac­tive in Can-am rac­ing was

that, un­like in vir­tu­ally ev­ery other race se­ries, there was no penalty for run­ning a turbo- or su­per­charged en­gine. This lax rul­ing gave engi­neers carte blanche to ex­plore the very lim­its of turbo tech­nol­ogy – and ex­plore it they did. In 1971 Porsche built a car that would turn Can-am on its head: the 917/10 with a tur­bocharged Type 912 flat-12 en­gine, to be used in an all-alu­minium space-frame chas­sis.

The 917/10 fea­tured dual tur­bocharg­ers, one for each bank of cylin­ders, sup­plied by the Ger­man com­pany Eber­spächer, a name more fa­mil­iar to­day with petrol heaters used in campers and com­mer­cial ve­hi­cles. Eber­spächer worked closely with the Us-based Aire­search op­er­a­tion, which had con­sid­er­able ex­pe­ri­ence with race car in­stal­la­tions through its in­volve­ment with the USAC se­ries.

Itʼs Hans Mezger that we can thank for steer­ing Porsche down the tur­bocharg­ing route. He saw the po­ten­tial ben­e­fits of forced in­duc­tion and en­cour­aged one of his team, Valentin Schäf­fer, to look into tur­bocharg­ing a 4.5-litre ver­sion of the Type 912 en­gine. Schäf­fer ʼs so­lu­tion was straight­for­ward: you have two banks of cylin­ders, you use two tur­bos – just like on the Mckee-oldsmo­bile Can-am en­gine. To limit max­i­mum boost, and there­fore pre­vent the en­gine from over­boost­ing and de­stroy­ing it­self, a sin­gle waste­gate was fit­ted.

Early tests with the dual-blown Type 912 mo­tor in the 917/10 chas­sis were ʻin­ter­est­ingʼ. Jo Sif­fert was the test pi­lot and he found this first taste of tur­bocharg­ing un­pre­dictable to say the least. The tur­bos seem­ingly took an age to ʻspool upʼ, to use mod­ern par­lance, and equally as long to bleed off boost. The re­sult was that as Sif­fert ap­plied throt­tle ex­it­ing a cor­ner, there was a sizeable de­lay be­fore any­thing hap­pened – and when the mo­tor did come on boost, it hap­pened very quickly. Con­versely, when he lifted off the throt­tle at the end of the straight, the tur­bos con­tin­ued to spin at speed, pro­duc­ing boost when it was­nʼt needed. As a con­se­quence of this, itʼs said that Sif­fert vis­ited the veg­e­ta­tion along­side the Weis­sach test fa­cil­ity on more than one oc­ca­sion.

Can-am reg­u­la­tions, as men­tioned, were lax and placed no re­stric­tions on en­gine ca­pac­ity, nor did they fac­tor in a spe­cial index for tur­bos. How­ever, Porsche was not a com­pany renowned for ʻgo­ing for brokeʼ so lim­ited its Type 912 en­gine to just 1.5 bar (22psi) – still enough for 1000bhp at 7800rpm, and a mas­sive 725lb ft of torque at 6400rpm.

For ʻnor­malʼ use, Porsche re­stricted boost to 1.3bar (18psi), which lim­ited out­put to just un­der 900bhp – still al­most 200bhp more than the Mclarens.

In an ef­fort to com­bat the ef­fects of turbo lag, and over­boost on a trail­ing throt­tle, Porsche had de­vel­oped a sys­tem of air valves, some of which bled off man­i­fold pres­sure when the throt­tle was closed, while oth­ers opened to the at­mos­phere when the throt­tle was ap­plied at low rpm – ef­fec­tively turn­ing the car into a nor­mally-as­pi­rated con­fig­u­ra­tion un­til the en­gine pro­duced pos­i­tive boost. The re­sult was a car that could ac­cel­er­ate from 0–60mph in 2.1 sec­onds, 0–100mph in 3.9 sec­onds and 0–200mph in just 13.4 sec­onds!

No won­der peo­ple were sit­ting up and tak­ing notice when the Penske-porsches came to the line in 1972. How­ever, star driver Mark Dono­hue was in­jured in a crash at Road At­lanta, mean­ing that he was un­able to cap­i­talise on his devel­op­ment ex­pe­ri­ence, Ge­orge Follmer be­ing brought in to take his place for much of 1972, end­ing the year as cham­pion.

The 917/10 was clearly a mas­sive force to be reck­oned with, but Porsche had more up its sleeve for 1973. The 917/10ʼs chas­sis was cut in two and ex­per­i­ments car­ried out with dif­fer­ent ex­ten­sions to alter the wheel­base. Even­tu­ally Mark Dono­hue felt hap­pi­est with a wheel­base of 2500mm (98.4in), which had the added ben­e­fit of al­low­ing a larger fuel tank to be used, in­creas­ing fuel ca­pac­ity from 86 gal­lons to a whop­ping 106 gal­lons.

Fur­ther re­search was car­ried out on aero­dy­nam­ics, Porsche call­ing on the ser­vices of French aero­nau­ti­cal com­pany, SERA. The re­sult was a new body with a re­designed nose, which came to be re­ferred to as the ʻParis bodyʼ. The re­sult was a 212mph speed recorded at Paul Ri­card in France. Power was up for 1973, too, the 5.4-litre en­gine (Type 912/52) now pro­duc­ing 1100bhp, with 1500+ seen on the dyno. The driver now had con­trol of boost, too, with a large knurled knob in the cock­pit al­low­ing Dono­hue to to ad­just the waste­gate set­tings at will. With ri­vals fall­ing by the way­side, Porsche – and Dono­hue – walked away with the Can-am cham­pi­onship…

Porscheʼs dom­i­na­tion of Can-am was ul­ti­mately re­spon­si­ble for the se­riesʼ demise. The or­gan­is­ers, SCCA, went against their agree­ment not to alter rules with less than

“PEO­PLE WERE SIT­TING UP AND TAK­ING NOTICE…”

a year ʼs notice and talked of lim­it­ing en­gines to match those used in F5000 sin­gle-seaters. That meant a limit of 3.0-litres for cars with ʻrace en­gi­nesʼ (ie, non-pro­duc­tion-based, mul­ti­cam de­signs) or 5.0-litres for those with ʻiron-blockʼ pro­duc­tion-based mo­tors. Front-run­ners in Can-am, PenskePorsche and Shadow, both ex­pressed their dis­like and Porsche al­lowed Penske to opt out of its three-year con­tract a year early. Can-am strug­gled on for one more year be­fore SCCA pulled the plug on Novem­ber 19th 1974. But the ex­pe­ri­ence gained would not go to waste.

As far back as 1969, Porsche had looked into tur­bocharg­ing its flat-six en­gine, with ex­per­i­men­tal work be­ing car­ried out on a 2.0-litre 911. How­ever, al­though the en­gine ran, it was never in­stalled in a car (one can only imag­ine the re­sults had this line of devel­op­ment been pur­sued so long ago…). The con­cept of tur­bocharg­ing a road car was res­ur­rected in 1972, al­most cer­tainly kicked into life, not only by the news that BMW was about to launch its 2002 Turbo, but also that Porscheʼs Bavar­ian ri­vals had dis­played an ex­otic gull-winged sports car pow­ered by a tur­bocharged en­gine, which threat­ened to en­croach on ʻtheir ʼ ter­ri­tory.

Porscheʼs own ex­per­i­ments in 1972 were based around a 2.7-litre en­gine, that fea­tured an in­duc­tion sys­tem not dis­sim­i­lar to that of the con­tem­po­rary Can-am mo­tors. Dy­namome­ter tests held early in 1973 sug­gested that re­li­a­bil­ity would­nʼt be an is­sue, so the go-ahead was given to take the project to the next stage by in­stalling a ver­sion of the en­gine in a road car. Ini­tial tests at Weis­sach showed up two prob­lems, nei­ther of which was in­sur­mount­able: the chas­sis re­quired fur­ther devel­op­ment to han­dle the ex­tra horse­power, and the en­gine suf­fered from un­ac­cept­able lev­els of turbo lag. But power – of that there was plenty, with around 250bhp on tap.

Com­pany chair­man Ernst Fuhrmann was im­pressed with the ini­tial re­sults but, in an ef­fort to keep costs down, in­sisted that any fur­ther devel­op­ment work re­volve around the use of the new K-jetronic fuel-in­jec­tion sys­tem. With a sin­gle tur­bocharger lo­cated low-down to the left rear of the en­gine, close to the ex­haust pipework and help­ing to keep the cen­tre of grav­ity as low as pos­si­ble, the pro­to­type 911 turbo en­gine was one step nearer to be­ing pro­duc­tion-ready.

The task of tak­ing things to the next level was en­trusted to Her­bert Ampferer, who in 1985 would go on to file a patent for Porscheʼs Var­i­o­ram in­duc­tion sys­tem. The big­gest

prob­lems Ampferer faced were find­ing a cure for the one-off switch-like na­ture of these early turbo in­stal­la­tions and pack­ag­ing the whole sys­tem in a way that made it suit­able for pro­duc­tion. But by sum­mer 1973, Porsche felt it was ready to tell the world the news: a tur­bocharged 911 was on the hori­zon.

Type 930, as the new project was to be called, first saw the light of day at the 1973 Frank­furt mo­tor show. On dis­play was a 911 the likes of which had not been seen be­fore, with wider front and rear wings, stretched to cover deep 15in­di­am­e­ter wheels, a front air dam and a large ʻwhale-tailʼ rear spoiler. The body­work was ef­fec­tively that of the 3.0-litre RS and IROC cars, fin­ished in a pearles­cent sil­ver. Bold ʻPorscheʼ graph­ics in white along each flank left no­body in any doubt as to who had built the car, but even bolder ʻTur­boʼ let­ter­ing over each rear wing made it clear this was no or­di­nary Porsche… A quick glimpse in­side re­in­forced this as the car fea­tured a pair of Re­caro ʻlol­lipopʼ seats, trimmed in plaid, with full har­ness seat belts for driver and pas­sen­ger.

Cu­ri­ous vis­i­tors to the show stand en­quired what lay un­der the rear lid. The an­swer was not al­ways the same – some peo­ple ap­pear to have been told it was a 2.1-litre tur­bocharged en­gine pro­duc­ing 280bhp (pre­sum­ably of the type that would ap­pear in the forth­com­ing RSR Turbo) but most were in­formed it was a 2.7-litre en­gine ca­pa­ble of pro­pel­ling the car to a top speed of over 160mph. What no­body was told, though, was that the en­gine was a mockup, with a dummy in­duc­tion sys­tem, in­ca­pable of run­ning be­fore, dur­ing or af­ter the show.

The Frank­furt show car served as some­thing of a wa­ter­shed within Porsche, lead­ing to two sep­a­rate lines of devel­op­ment: one as a lim­ited-pro­duc­tion road car (Type 930), the other as a full-blown competition car (RSR Turbo). From this point on, the teams re­spon­si­ble con­cen­trated on their own in­di­vid­ual pro­jects – both would prove to be ul­ti­mately suc­cess­ful in their en­deav­ours.

Thereʼs lit­tle doubt the dis­play car cap­tured ev­ery­oneʼs imag­i­na­tion, but Porsche could­nʼt prom­ise it would be a full pro­duc­tion model. In­deed, the ini­tial plans were that it would serve as a way for the com­pany to go rac­ing in Group 4 GT competition, where there was a re­quire­ment to build a min­i­mum of 400 ex­am­ples. Once those rel­a­tively few cars had been built and sold, that was it – the 911 Turbo would have served its pur­pose.

But even the task of sell­ing 400 of these cars did­nʼt prom­ise to be easy, for as 1973 drew to a close, so OPEC im­ple­mented a boy­cott of oil sup­plies, which turned the au­to­mo­tive world on its head. With­out oil, there could be no petrol. With­out petrol, what mar­ket would there be for a high­pow­ered tur­bocharged sports car? It seemed as if the Type 930 was des­tined to be still-born. Even BMW had killed off its won­der­ful 2002 Turbo…

But Fuhrmann had other ideas. He was de­ter­mined to see things through, de­spite on-road test­ing be­ing cur­tailed due to the ban on Sun­day driv­ing im­posed in Ger­many, along with speed re­stric­tions on the au­to­bahns and, in­cred­i­bly, tracks such as the Nür­bur­gring, Hock­en­heim and even Porscheʼs own Weis­sach fa­cil­ity. The re­stric­tions were grad­u­ally eased, al­low­ing Porsche to flex the Tur­boʼs legs more of­ten. But the mat­ter re­mained of how to sell the con­cept to a mar­ket still reel­ing from the ef­fects of OPECʼS stran­gle­hold on oil sup­ply.

The de­bate cen­tred round pric­ing. There were two schools of thought, one be­ing that the 911 Turbo should be sold as a stripped-down model at a rock-bot­tom price. Al­though this may seem a strange idea now, bear in mind that a) there were peo­ple proph­esy­ing the end of per­for­mance cars as we know them due to fuel short­ages and b) it would be a quick way to get rid of 400 cars so that the fac­tory could ho­molo­gate the Grp 4 en­tries.

On the other side of the fence were those – Fuhrmann among them – who felt that the car de­served to be sold as a lux­ury item, a well-equipped range-top­ping model with a price tag that matched its ob­vi­ous qual­ity. Ul­ti­mately this was the win­ning ar­gu­ment and the de­ci­sion was made to mar­ket the 930 ac­cord­ingly. One year later, at the 1974 Paris Sa­lon dʼauto, the pro­duc­tion ver­sion of the 911 Turbo was shown for the first time – a well-equipped, highly-specʼd Porsche that marked the com­pa­nyʼs first ven­ture into the world of road-go­ing su­per­cars.

Jür­gen Barth re­calls that, while work­ing with the press de­part­ment in 1976, he was tasked with driv­ing the 911 Tur­boʼs first 400 cus­tomers to give them in­struc­tion on how to han­dle this pow­er­ful new model. ʻI drove each of them from the fac­tory on a high-speed run up to Heil­bronn, tak­ing the op­por­tu­nity to ex­plain the car in de­tail to the new own­ers. This was a spe­cial ser­vice I was asked to do by the sales de­part­ment.ʼ

Look­ing back, itʼs per­haps dif­fi­cult to ap­pre­ci­ate what a mon­u­men­tal im­pact the 911 Turbo had on those in­volved with Porsche in the 1970s. It was in a league of its own and proved once and for all that, on track or on the street, Porsche could run with the big boys. CP

Below: The pro­to­type 930 Turbo shared stand space with a hum­ble Vw-porsche 914 at Frank­furt, rep­re­sent­ing op­po­site ends of the Porsche spec­trum

Above right: Ferry Porscheʼs sis­ter, Louise Piëch, re­ceived a spe­cial Porsche Turbo for her 70th birth­day in Au­gust 1974. Note the use of a ʻnar­row-bodyʼ ʻshell

Above left: Blue­print for suc­cess. Porscheʼs 930 was launched in 1974, turn­ing the su­per­car world on its head

Below: Pro­to­type Turbo was first shown at the 1973 Frank­furt show, where it at­tracted enor­mous at­ten­tion. The non-run­ning show car (chas­sis num­ber 9113300157) still sur­vives, hav­ing later been con­verted to road-go­ing RSR spec

Above, left and right: 911 Turbo was an ex­er­cise in pack­ag­ing, with the turbo placed low down at the left rear of the car, help­ing to economise on pipework and lower the cen­tre of grav­ity

Above: The mighty 917/10 and 917/30 de­stroyed the op­po­si­tion in Can-am, ul­ti­mately bring­ing the se­ries to a pre­ma­ture end – no­body, it seems, could beat the tur­bocharged Porsches…

Below right: Al­though ul­ti­mately not a great rac­ing suc­cess, the 1974 Turbo RSR showed the way ahead

Below left: Mark Dono­hue test­ing 917/10-003 at Paul Ri­card in the south of France

Below left: 1969 Mckee CanAm en­try fea­tured twin­tur­bocharged Oldsmo­bile alu­minium-block V8 mo­tor

Top left: Tur­bocharged Lib­erty aero en­gine pro­duced 360bhp in 1915 Top right and above left: Gen­eral Mo­tors launched the tur­bocharged Oldsmo­bile Jet­fire and Chevrolet Cor­vair Monza in 1962 Above right: BMW beat Porsche into pro­duc­tion with its...

Below right: Porscheʼs re­sponse was the twin-turbo Type 912 flat-12…

Top left and above left: Porsche used the 930 as the base for two of its most suc­cess­ful rac­ers, the 935 (top) and the Group 4 934

Below left: ʻGhostʼ graph­ics helped to em­pha­sise the bru­tal look of the Turbo, ac­cen­tu­at­ing the width of the rear wings on this early pro­duc­tion model

Above: Orig­i­nal 3.0-litre mo­tor ran with­out an in­ter­cooler. This was added in 1978 with the ad­vent of the 3.3-litre en­gine

Below: Pro­to­type looks un­der-tyred from this an­gle. First cars were un­der­braked, too, with reg­u­lar 911SC discs and calipers

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