BLOWN AM­BI­TIONS

How the mighty Turbo RSR never quite lived up to ex­pec­ta­tions

Classic Porsche - - Contents - Words: Keith Seume Pho­tos: KS Col­lec­tion and Porsche Archiv

“KEEN TO MAKE THIS NEW RACE CAR AS RAD­I­CAL AS POS­SI­BLE…”

You could day it all started with a fuel cri­sis. Porscheʼs dom­i­na­tion of the Can-am se­ries, with the all-con­quer­ing 917s driven by the likes of Mark Dono­hue, Milt Min­ter and Ge­orge Follmer, was brought to an end by the SCCAʼS de­ci­sion to ef­fec­tively out­law the mighty tur­bocharged ma­chine. The Arab-is­raeli war had re­sulted in fuel short­ages, with a con­se­quent rise in petrol prices, giv­ing the SCCA due cause to make rule changes so as to be seen to be what we might to­day call ʻpo­lit­i­cally cor­rectʼ.

Of course, we all know the real rea­son: Porsche had de­stroyed the op­po­si­tion and there was ev­ery like­li­hood that no­body else would come out to play if the 917ʼs win­ning ways were to con­tinue. The SCCA, keen to pro­tect its do­mes­tic in­ter­ests, sub­tly rewrote the rule book, re­duc­ing the fuel ca­pac­ity of each car thereby mak­ing it im­pos­si­ble to run a tur­bocharged 917 com­pet­i­tively.

In Europe, there was talk of a new FIA Pro­to­type class for 1975, based around ʻsil­hou­et­teʼ pro­duc­tion-based ma­chines which bore a closer re­sem­blance to the cars you could buy from the dealer. But the in­tro­duc­tion of the new class was de­layed un­til 1976, the class evolv­ing into what be­came known as Group C, en­tries for which bore ab­so­lutely no re­la­tion to any pro­duc­tion car.

But, of course, Porsche had al­ready been one step ahead of the game and had set about de­vel­op­ing a new pro­duc­tion-based racer that could not only com­pete in the pro­posed new class but also serve to pro­mote the all-new road-go­ing Porsche 911 Turbo – Type 930.

The race depart­ment was keen to make this new race car as rad­i­cal as pos­si­ble, ex­ploit­ing ev­ery loop­hole in the reg­u­la­tions it could find.

The idea of a sil­hou­ette for­mula gave the race en­gi­neers a great deal of lat­i­tude to cre­ate a ground-break­ing new car. There was much talk of build­ing an out­ra­geous glass­fi­bre­bod­ied 911, the shell of which would be mounted on a light­weight alu­minium tubu­lar chas­sis. A sort of Can-am 911, if you will, but rear-en­gined in line with pro­duc­tion mod­els. It would have been a win­ner, of that there can be lit­tle doubt.

But Dr Ernst Fuhrmann had other ideas. As head of Porscheʼs race depart­ment, he had the ul­ti­mate say over what di­rec­tion this and any other project should take. His rea­sons were twofold. First, the cost. By em­bark­ing on a to­tally new chas­sis de­sign from scratch, the bud­get would have to be very gen­er­ous in­deed. This was a pe­riod when Porsche could ill af­ford to make a ma­jor in­vest­ment in a new race pro­gramme as the com­pany had, like so many oth­ers at the time, taken quite a hit thanks to the oil cri­sis.

Sec­ond, Fuhrman­nʼs preference to base the new car, how­ever loosely, around the pro­duc­tion model would, he felt, also help to act as a sales pro­mo­tion tool for the new 930.

How­ever, be­cause the new car – gen­er­ally re­ferred to as the Turbo RSR – was con­ceived to com­pete in the FIAʼS new Pro­to­type class, the way was open for Porsche to de­velop the 911 to a level pre­vi­ously un­seen.

The big­gest de­par­ture was in the area of the sus­pen­sion. Gone were the tor­sion bars, which had been a fea­ture of ev­ery pro­duc­tion model from day one, and in their place were coil-over damper units at each cor­ner. These con­sisted of pro­gres­sively-wound ti­ta­nium coils over Bil­stein damper units.

At the front, the stock-style Macpherson strut lay­out was re­tained, but with spher­i­cal joints, as was the semi-trailin­garm de­sign at the rear. These rear sus­pen­sion arms, how­ever, were fab­ri­cated from alu­minium, hand-formed and welded to ma­chined alu­minium up­rights. The tor­sion bar mount­ing and tubes were also no­table by their ab­sence. In to­tal, the Turbo RSRʼS set-up was some 66 pounds lighter than that of its pre­de­ces­sor.

Sus­pen­sion ge­om­e­try was heav­ily re­vised com­pared to stock, with the front struts fea­tur­ing raised spin­dles to lower the nose of the car – a trick first used on the orig­i­nal non­turbo Car­rera RSR pro­to­type back in 1972.

The sus­pen­sion was also set up to in­duce anti-squat un­der ac­cel­er­a­tion, and anti-dive un­der se­vere brak­ing. To­day, all these mod­i­fi­ca­tions seem rel­a­tively sim­ple – af­ter all, you can now buy coil-spring con­ver­sions for al­most any tor­sion-bar 911 – but at the time they were ground­break­ing.

The bodyshell it­self was heav­ily mod­i­fied. Although the cen­tral ʻtubʼ re­mained clearly iden­ti­fi­able as that of the 911/930, it was de­rived from that used on the nor­mallyaspi­rated Car­rera RSR. The rear pan­el­work was cut away to make way for an alu­minium sub­frame to sup­port the en­gine and an­cil­lar­ies. The body­work was far lighter than stock thanks to the ex­ten­sive use of glass­fi­bre pan­els.

Both doors, the front and rear ʻlidsʼ, and the front and rear valances were all light­weight mould­ings, while the side and rear win­dows were Plex­i­glas. The bulky rear panel sur­round­ing the rear win­dow, and which swept back to­wards the huge rear wing, fea­tured a for­ward-fac­ing air-scoop to di­rect cool air into the en­gine bay. The first pro­to­type ac­tu­ally fea­tured a sep­a­rate wing mounted on struts, so that it could quickly and eas­ily be ad­justed at the track. Fuhrmann, how­ever, dis­liked the de­sign.

To his way of think­ing, it was im­por­tant that the over­all look of the car re­flected that of the pro­duc­tion 930, so the rear wing was re­designed to be­come some­thing of a car­i­ca­ture of the 930ʼs whale-tail spoiler. Dur­ing a trip to the wind-tun­nel in Stutt­gart, the team, led by Tony Lap­ine, tried var­i­ous ideas to meet Fuhrman­nʼs de­mands. The first com­prised a pair of two sail pan­els that reached back from ei­ther side of the rear win­dow to sup­port the wing, with a flat panel that bridged across be­tween them.

This sat­is­fied Fuhrman­nʼs wishes but proved to be far from ef­fi­cient in the wind tun­nel, as the de­sign dis­rupted air­flow over the wing it­self. The so­lu­tion was to gen­tly lift the rear edge of the roof and flush-mount the win­dow in a slightly raised po­si­tion. Note there was a full-width rear apron, the cen­tre sec­tion of the rear body­work be­ing dis­pensed with to make room for the huge sin­gle tur­bocharger and as­so­ci­ated plumb­ing.

The new wing and rear body­work be­came the RSRʼS trade­mark fea­ture, along with the mas­sively-ex­tended rear wheel-arches nec­es­sary to cover the huge cen­tre-lock wheels and tyres. And huge they were! They re­tained the same 15-inch di­am­e­ter of the road-go­ing 911ʼs Fuchs wheels, but mea­sured a healthy 11.5ins wide at the front and ei­ther 15 or 17 inches at the back, depend­ing on track con­di­tions. As a con­se­quence of the wide wheels and cor­re­spond­ing arches, the Turbo RSR was some two me­tres wide – some 15.5 inches more than the orig­i­nal nar­row­bod­ied 911.

The brakes and steer­ing were the same as those of the

Car­rera RSR, with ven­ti­lated cross-drilled discs fit­ted with four-pot calipers. They had proved to be per­fectly ad­e­quate on the ear­lier car and there was felt to be no need for change on the Turbo RSR.

The in­te­rior, how­ever, came in for some ma­jor re­vi­sion. To be­gin with, the fuel tank which had pre­vi­ously resided in the front ʻlug­gageʼ com­part­ment was now re­lo­cated to the right side of what would have been the rear pas­sen­ger seat area. This was to help im­prove weight distri­bu­tion in the left­hand drive RSR – and, be­cause it was more cen­trally lo­cated fore and aft, as the fuel level (and hence weight) fell dur­ing the course of a race, there would be less of an ef­fect on han­dling.

Most of the re­main­der of the in­te­rior was taken up with a sub­stan­tial alu­minium rollcage, which added much­needed rigid­ity to the light­weight bodyshell. The dash­board was still recog­nis­ably ʻ911ʼ in de­sign, but the ped­als and gear shift as­sem­bly were be­spoke.

But what of the en­gine and trans­mis­sion? The lat­ter was based on the pro­duc­tion 915-se­ries fivespeed transaxle and, de­spite a stronger side­plate to help keep the ring and pin­ion to­gether, proved to be the weak­est link in the whole car. Sim­ply put, the unit was not quite man enough to with­stand the torque gen­er­ated by the tur­bocharged flat-six… For most races, a solid ʻspoolʼ was used in place of a dif­fer­en­tial.

The en­gine was a new ven­ture for Porsche. Not in terms of the use of tur­bocharg­ing, but be­cause through­out their par­tic­i­pa­tion in the Can-am se­ries, the race depart­ment had been free of any form of re­stric­tions re­gard­ing en­gine ca­pac­ity. That led to a train of thought that went ʻif enough is good, then more has to bet­ter ʼ.

But the FIA took a dif­fer­ent view, im­pos­ing a dis­place­ment fac­tor of 1.4 on all turbo- or su­per­charged en­gines. The CanAm mo­tors had a dis­place­ment of 5.4-litres, and pro­duced a mas­sive 1100bhp. The FIA rules lim­ited en­gines to 3.0-litres nor­mally-as­pi­rated, or 2143cc blown. If all else was equal, by fol­low­ing the les­sons learned from the Can-am pro­gramme, that would equate to a power out­put of 437bhp. There was con­cern that this would­nʼt be enough to get the job done, as nor­mally-as­pi­rated 3.0-litre en­gines were ca­pa­ble of pro­duc­ing around 480bhp.

To fit within the rules, Porsche came up with a 2142cc en­gine – a flat-six, nat­u­rally – that com­prised a 66mm crankshaft from the 2.0-litre 911, in con­junc­tion with 83mm Nikasil cylin­ders and ti­ta­nium con-rods ʻbor­rowedʼ from the old 906/Car­rera 6. The heads fea­tured 47mm in­let valves and 40.4mm ex­hausts, the for­mer be­ing of ti­ta­nium. All valves were sodium-filled, a trick learned dur­ing the Can-am days. Com­pres­sion ra­tio was a mod­est 6.5:1 in def­er­ence to the KKK turbo. In an ef­fort to save weight, the Turbo RSR en­gine was based around a mag­ne­sium crank­case, rather than the stronger alu­minium type then in pro­duc­tion.

The en­gine in its ini­tial form was shown to pro­duce be­tween 400 and 450bhp, depend­ing on boost lev­els. This was con­sid­ered promis­ing, but the Achillesʼ heel was heat. All tur­bocharged en­gines will tend to run hot­ter than their nor­mally-as­pi­rated coun­ter­parts as the in­let air be­comes heated by the ex­haust gases flow­ing through the tur­bine hous­ing. This not only has a detri­men­tal ef­fect on power, but also, in­evitably, on cylin­der head tem­per­a­tures, lead­ing to early fail­ure of the seal be­tween heads and cylin­ders.

To com­bat this, Fuhrman­nʼs team de­signed an alu­minium in­ter­cooler that sat above the rear of the en­gine, fed by large NACA duct ahead of the rear wing. It was in­stalled on one of the two de­vel­op­ment cars, which were sched­uled to ap­pear

“IF ENOUGH IS GOOD, THEN MORE HAS TO BE BET­TER…”

at the Le Mans test day on 23 March 1974.

The test ses­sion showed the Turbo RSR to be con­sid­er­ably faster than its pre­de­ces­sor, lap­ping some 11 sec­onds quicker than the best time set by a non-turbo Car­rera RSR in 1973. In a four-hour race the next day, the two cars drew a lot of at­ten­tion and un­de­ni­ably showed prom­ise. But the RSR driven by Koinigg and Schurti broke a rocker arm in the first heat, while the num­ber one car of Gijs van Len­nep and Her­bert Müller ran out of fuel on the last lap in the first ses­sion and then de­stroyed a turbo in the sec­ond.

The team re­turned to Stutt­gart with mixed emo­tions and im­me­di­ately be­gan work on pre­par­ing the cars for their first cham­pi­onship ap­pear­ance at Monza in April. The in­let man­i­fold was re­vised, as was the de­sign of the in­ter­cooler. With 450bhp avail­able at 8000rpm, the two cars (chas­sis num­ber 911 460 9101 R12 as num­ber one team car, and chas­sis num­ber 911 460 9016 R9 en­tered as a ʻT car ʼ – for backup) were loaded and driven to Italy.

Driven by van Len­nep/müller, the Turbo RSR qual­i­fied in 12th po­si­tion, lap­ping some seven sec­onds faster than the first of the Car­rera RSRS back in 22nd on the grid. In the race it­self, the sin­gle­ton Turbo RSR fin­ished a cred­itable fifth over­all.

At Spa in May, the same cars and driv­ers were en­tered for the 1000km race, qual­i­fy­ing in sev­enth place on the grid (the ʻTʼ car was ninth). In the race it­self, van Len­nep/müller fin­ished a wor­thy third. Things were start­ing to look up for the Mar­tini-backed team.

At the Nür­bur­gring two weeks later, two cars were en­tered, the sec­ond driven by Schurti/koinigg. Müller/van Len­nep qual­i­fied in 12th po­si­tion, just over 3 sec­onds quicker than their team mates in 14th. In the race, the Turbo RSRS fin­ished in 6th and 7th po­si­tions, de­spite both hav­ing been in­volved in ac­ci­dents in both prac­tice and the race it­self.

At the be­gin­ning of June, two Turbo RSRS ap­peared at Imola, one of which cre­ated con­sid­er­able in­ter­est in the pits: it wore a ʻflat-fanʼ cool­ing ar­range­ment, as op­posed to the orig­i­nal ver­ti­cal fan lay­out pre­vi­ously used. This dif­fered from the flat-fan sys­tem used on ear­lier race en­gines, which were gear-driven. On the Turbo RSR, the fans were to be driven by a shaft ro­tated by a V-belt off the crank pul­ley.

How­ever, things did not go well for Porsche in Italy, for the flat-fan car (the en­gine of which was re­ferred to as the ʻPhase 3ʼ de­sign) was de­layed by oil leaks, a faulty fan and an ail­ing tur­bocharger. Its sis­ter car broke its gear­box and was left stuck in fourth gear. Nei­ther Turbo RSR was clas­si­fied as fin­ish­ing the race.

All eyes were now on Le Mans, where the team had high hopes of head­ing the field against op­po­si­tion in the form of the scream­ing Ma­tras and thun­der­ing Gulf-mi­rages. The cars were clocked at a frac­tion un­der 190mph on the Mul­sanne Straight with the boost wound up to ʻmax­i­mumʼ.

Af­ter qual­i­fy­ing, the Mar­tini-liv­er­ied RSRS of van Len­nep/müller (run­ning the new Phase 3 en­gine) and Schurti/koinigg (with the ver­ti­cal fan Phase 2 unit) found them­selves in 7th and 11th on the grid, re­spec­tively. Ma­tras took four of the top six places, with the re­main­ing two grabbed by a pair of Gulf-mi­rages.

In pre-event press cov­er­age, the two Porsches were hardly given any ʻinkʼ, all eyes be­ing fo­cused on the Ma­tras and John Wyer-prepped Gulf-fords. In­deed, as the race got un­der­way, the Ma­tras be­gan pulling away from the field, the Gulf-fords strug­gling to keep pace. And the Porsches? By the sec­ond hour, the van Len­nep/müller en­try was a lap

down on the lead­ers, their progress hav­ing been slowed by their pit space be­ing blocked by a 908 which was un­der­go­ing ma­jor ʻsurgeryʼ.

As night be­gan to fall, the two Turbo RSRS found them­selves in third and fourth places be­hind the two Ma­tras, but then dis­as­ter struck when the num­ber two team car (wear­ing race num­ber 21) of Schurti/koinigg threw a rod, spew­ing oil over the hot ex­haust sys­tem. The back of the car was en­veloped in flames, prompt­ing some fancy foot­work by the mar­shals as they sprinted to the res­cue.

Hold­ing onto third po­si­tion, six laps be­hind the lead­ing Ma­tras, the van Len­nep/muller Turbo RSR bat­tled on through the night un­til the news broke that two of the Ma­tras were out, one be­ing the sec­ond­placed car of Wollek/jas­saud/dol­hem, which blew up in spec­tac­u­lar fash­ion. This pushed the Mar­tini Porsche up into sec­ond place, which it held un­til the fol­low­ing morn­ing.

Le Mans is al­ways a war of at­tri­tion, and no­body dared take any­thing for granted – least of all Porsche who were painfully aware of the RSRʼS weak­nesses. But van Len­nep/müller kept on plug­ging away, hold­ing off the pur­su­ing Jabouille/mi­gault Ma­tra snap­ping at their heels in third place, de­spite its en­gine be­gin­ning to tire in the heat.

And the RSRʼS Achilles heel struck again: van Len­nep brought the car into the pits hav­ing lost the first three gears! A cou­ple of laps later, it was back in again to in­ves­ti­gate a prob­lem with the steer­ing. Müller took the car out and later re­turned to the pits when he was left with just one gear!

With just 90 min­utes to go, the rain came (as it al­ways seems to at Le Mans) but it did­nʼt last long. Into the fi­nal hour and the lead­ing Ma­tra had a mar­gin of five laps over the Turbo RSR, which now had only third and fourth gears func­tion­ing. Luck was on Porscheʼs side, though, and the van Len­nep/müller en­try man­aged to hold on to its sec­ond place, fin­ish­ing some 75km be­hind the win­ning Ma­tra of Pescarolo/larousse.

The rest of the sea­son brought mixed re­sults for the Turbo RSRS. In July, van Len­nep and Müller grabbed an­other sec­ond at Watkins Glen, fol­lowed by a sixth at Zeltweg and a fifth at Brands Hatch. At the fi­nal round of the cham­pi­onship at Paul Ri­card in Au­gust, the van Len­nep/müller car fin­ished sev­enth, de­spite only hav­ing one ra­tio (sec­ond, at that) left work­ing in the gear­box.

Porsche fin­ished the sea­son in third place in the cham­pi­onship be­hind Ma­tra and Gulf-ford. The Turbo RSR had shown prom­ise but was not quite fast enough to keep up with the more rad­i­cal com­peti­tors, nor re­li­able enough (thanks largely to the gear­box) to out­last them if they hap­pened to run into trou­ble.

Porsche de­cided not to con­tinue com­pet­ing with the Turbo RSR past the 1974 sea­son. The new sil­hou­ette for­mula would not come into play un­til 1976, mean­ing that 1975 would have promised more of the same ʻal­most but not quiteʼ sit­u­a­tion that bugged the teamʼs ef­forts in ʼ74. Porsche was even re­luc­tant to sell any Turbo RSRS to pri­va­teers for fear of poor re­sults af­fect­ing sales of the 911.

So the car which many have come to re­gard as one of the ul­ti­mate 911s, in re­al­ity did not have the most il­lus­tri­ous of ca­reers. With just one sea­sonʼs use, and no out­right vic­to­ries, the Turbo RSR still re­mains, how­ever, one of the most mem­o­rable ma­chines ever to come out of Stuttgartʼs race depart­ment.

“PORSCHE WAS EVEN RE­LUC­TANT TO SELL ANY TURBO RSRS…”

Left: It was­nʼt of­ten that Porsche was in the po­si­tion of only be­ing able to boast about a sec­ond place… With­out gear­box prob­lems, things may have been dif­fer­ent at the 1974 Le MansBelow: Gijs van Len­nep pulls out of the pits dur­ing the 1974 Nür­bur­gring 1000km. Shar­ing with Her­bert Müller, van Len­nep fin­ished sixth over­all in RSR Turbo R12

Above: Surely there has not been a more bru­tal-look­ing 911 de­riv­a­tive than this? Body­work was ap­prox­i­mately 2 me­tres wide at the rear

Below, left and right: Le Mans 1974 and a me­chanic drives R12 through the pad­dock. Driven by Man­fred Schurti and Hel­muth Koinigg, en­gine prob­lems forced re­tire­ment in the sev­enth hour while run­ning 14th

Below: R13 makes a colour­ful splash at Le Mans Clas­sic, with Gijs van Len­nep at the wheel

Below: So near, yet so far. Müller and van Len­nep might have won the 1974 Le Mans had it not been for trans­mis­sion prob­lems which, at one point, left the car with just one gear. Steer­ing prob­lems dur­ing the race had­nʼt helped, ei­ther

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.