primotipo…

Rainer Schlegelmilch’s artistry lays bare the clinical beauty of the 1991 McLaren Honda at Silverstone on 14 July…

Whilst this article is a summary of McLaren’s ultimately successful 1991 season of changing fortunes with its new Honda V12 powered McLaren MP4/6- all of the photographs are by Rainer Schlegelmilch and were taken over the Silverstone British GP weekend of 11 to 14 July.

This was Honda’s third different type of engine in four seasons- a new 3.5 litre 60˚ V12 unit with greater piston area than the outgoing V10 it replaced and therefore it had a potentially higher rev limit. More revs, all things being equal, results in more power. It was not without its chassis design and packaging issues, the motor was longer, heavier and thirstier than the V10 it replaced but the anticipated 720bhp should have been more than enough, on balance to make the car faster.

When first tested by Ayrton Senna in an MP4/6C test-mule, he was far from impressed and said as much to the Japanese. The Honda people persevered of course, and McLaren’s season got off to a great start with four wins on the trot. The increased engine weight was partially offset by the latest development of McLaren’s six-speed manual, transverse Weisman/McLaren gearbox.

 

Whilst visually similar to the outgoing MP4/5B, the new cars aerodynamic profile was different as designer Neil Oatley and his team had received fresh perspective and input from Henri Durand who had jumped ship from Ferrari to McLaren in mid-1990.

Many changes had to be made to the chassis to accommodate the longer engine and enlarged fuel cell needed to satisfy its greater thirst. Despite additional length, the new tub was much stiffer in terms of torsional rigidity and comprised fewer basic components than its predecessors.

There were changes to the suspension too. The  pushrod-activated coil-spring/dampers were now mounted on top of the chassis ahead of the cockpit instead of being installed vertically on either side of the footwell.

The increased fuel consumption presented lots of challenges. Despite plenty of development on the engine management system, Senna twice ran out of fuel (at Silverstone and Hockenheim) but the Brazilian Ace and his new car remained unbeaten up to and including Monaco- giving McLaren a comfortable lead in the Constructors‘ Cup at that stage of the season.

This margin was to prove crucially important as the team’s performance began to slip and Williams Renault began to gather pace with Nigel Mansell and Riccardo Patrese threatening as the Williams FW14 Renault V10’s reliability improved.

‘In Montreal two things quickly became apparent. The first was that the Honda’s extra power was simply to offset its greater weight relative to the V10s, particularly when its internal frictional losses continued to rise. The other was that the Williams FW14s, particularly Mansell’s, were really getting into their stride’ wrote McLaren.

Honda, of course continued development of its V12. The ‘Spec 1’, which won at Phoenix, Interlagos and Monaco was replaced by ‘Spec 2’- introduced ahead of Monaco offered better mid-range punch thanks to a new induction system. The friction problems were addressed in the ‘Spec 3’ variant here at Silverstone.

In addition the cars suspension was evolved, new linked rocker arms were fitted to reduce roll and a cockpit-adjustable ride-height mechanism was deployed.

The fuel metering issues so obvious during the British and German Grands Prix weekends were mainly caused by Shell’s experimentation with different fuel densities and viscosities.

 

 

 

 

 

 

 

 

 

 

At Silverstone Nigel Mansell and his Williams dominated at home, other than for part of the first lap- Senna jumped from grid 2 and led until Mansell passed him into Stowe, the Brit led from start to finish.

Nigel and Ayrton drove away from the rest leaving Berger, Prost and Alesi scrapping over third, a duel settled in Jean’s favour, he lost the place later in the race in a collision with Aguri Suzuki. Mansell won from Berger’s McLaren and Prost’s Ferrari 642 V12 with Senna classified fourth having lost his hard-raced second after running out of fuel, as written above.

‘At Paul Ricard, another inaccurate readout forced Senna to drive conservatively, although following this Honda’s research and development effort accelerated dramatically so that by the time he arrived in Hungary he had a car which could be safely revved to 14,800 rpm, albeit only for short bursts’

In Budapest McLaren regained its form in order to able to save its season.

With great chassis balance and another reworked engine comprising lighter cylinder heads, camshafts and connecting rods, Senna pulled out some of the magic only he possessed and pushed the Williams FW14 Renault RS3 3.5 V10 duo back to second and third places.

Despite a ‘box failure he did it again at Spa where he nursed the failing car home and saw his lead over the Williams boys grow significantly after another Mansell retirement due to an electrical problem lost the Brit a ‘sure win’.

Then Williams had two wins- the Portuguese (Patrese) and Spanish GP’s (Mansell) in a season of changing fortunes, in Spain Senna struggled on the wrong tyres.

‘At Suzuka the order flipped again, the correct tyres and yet more successful engine development leaving Senna in an unassailable position on 96 points. He returned to Brazil with a resounding third title, while Berger finished fourth with 43 points, having been handed victory by Senna in Suzuka. McLaren again took the Constructors World Championship’.

An historic sidebar to MP4/6 is that it was the last car to win an F1 World Championship powered by a V12 engine and using a traditional manual gearbox. Whilst McLaren tested a semi-automatic ‘box during the season it was not deemed race-worthy so was not used, Williams and Ferrari were the only teams so equipped that season.

The 1992 championship winning Williams FW14B Renault was ‘an orgy of technology’- semi-automatic transmission, active suspension, traction control and for a while, anti-lock brakes whilst still using the evolved but tried and true Renault RS3/4 engines, a story for another time…

 

 

 

 

Credits…

Rainer Schlegelmilch, Getty Images, mcLaren.com

Tailpiece…

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