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Race Engine Technology issue 031 : JUNE/JULY 2008
FOCUS : SURFACE COATINGS Adding value Sonny Leonard: MOUNTAIN MAN THE COMMUNICATIONS HUB OF THE RACING POWERTRAIN WORLD
Ian Bamsey reviews the state of the art in surface coatings for race engine components and highlights cutting edge developments
MERCEDES-BENZ
GRAND PRIX V8 Inside the factory
ADVANCED COATINGS
GUIDE How to boost parts performance
Zircotec provides a plasma-sprayed, zirconium-based ceramic thermal barrier coating JORDAN-SUZUKI
SUPERBIKE Motorcycle race engine insight
JUNE/JULY 2008
recall some years ago a now familiar component treatment process was introduced to the racing industry by a paper given at an SAE Motorsports Conference. After the presentation I mentioned it to the representative of a Diamond-Like Carbon (DLC) coating specialist who was manning his company’s booth in the adjacent exhibition area. I asked him if this process could be complementary to his product. He remarked that there was indeed potential synergy and as soon as he could get away from his booth he went in search of the person who had given the talk. Today the treatment process in question is routinely used in conjunction with a DLC coating. A coating such as a DLC, which can help provide the hardest,
I
lowest friction surface available today is merely one of the factors that defi ne the overall characteristics of a given metallic race
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engine component. That component might be heat treated, nitrided, super-fi nished or what-have-you prior to application of a particular surface coating. In fact, if we go back to the manufacturing stage, the difference between forging and machining a piston from solid, for example, can help defi ne the characteristics of a fi nished item. In truth, use of the most appropriate manufacturing techniques can be more signifi cant in terms of component performance than the subsequent application of even an advanced surface coating. By and large, surface coatings are applied to engine components to reduce friction and wear, to increase performance and durability and in some instances to act as a thermal barrier or simply to assist the break-in process. Surface coatings can even be employed to induce friction. But coatings represent not only an additional cost they are also an additional element that can go wrong. DLC coatings are
typically extremely hard but with that, somewhat fragile. A 19,000 rpm Formula One V8 could not survive two consecutive races without the help of DLC, whereas there is no use of this type of coating in the most numerous LMP1 engine at Le Mans this year, the 9000 rpm, 5.5 litre Judd V10, which has to run over 5000 kilometres in that one event. Surface coatings are typically used to take performance beyond the potential of surface and other material treatments. Many race engine components undergo heat treatments the scope of which these days includes ultra low temperature cryogenic treatments (see ‘The Frozen Depths’, RET 028). Widely used surface treatments include nitriding, shot peening, hard anodizing, plasma electrolytic oxidation, phosphate conversion, superfi nishing and isotropic superfi nishing (see ‘The Ultimate Finish’, RET 026, and the sidebar: Surface Treatments). Through (and often from a combination of) such treatments it is
possible to achieve a component working surface that is signifi cantly harder wearing with reduced friction, without the issue of adhesion and sometimes of fragility that can accompany the addition of a coating. Moreover, any coating process will only be worthwhile if proper attention has been paid to all prior manufacturing stages and if it is complementary to the component to which it is applied. On top of this, the coated component needs to be complementary
to the environment in which it operates. As recently as the 2008 Daytona 500 there were instances of problems with DLC coated valvetrain components where such were running against other components having an identical coating. That is not to say that a DLC coated camshaft cannot run satisfactorily against DLC coated lifters but care has to be taken with the exact specifi cation of the DLC on each item to avoid the sort of problems that some teams ran into at Daytona.
BORE COATINGS In view of the normal deployment of aluminium pistons carrying steel rings, cast iron cylinders work perfectly well without any sort of bore coating, unlike aluminium cylinders. For a long while, to avoid the galling that can come when aluminium runs on aluminium, those designing aluminium blocks accepted the weight penalty of cast iron liners and the loss of piston/bore clearance implicit in the differential of rate of expansion with temperature of aluminium and cast iron. Back in the sixties, Porsche air-cooled its engines, and consequently
much needed the higher rate of heat rejection of aluminium over cast iron. Moreover, at this time it was on a crusade to save weight from its racing cars, which went as far as the development of copper-beryllium brake discs. Refusing to accept the use of cast iron, its aluminium cylinders were chrome plated, the process supplier rolling pinpoint recesses into the chrome surface after the electrodeposited plating stage, for the purpose of retaining oil (see accompanying COATINGS MENU). This solution was only partially successful. While the chrome plated
cylinder operated perfectly well, coating adhesion was always a worry. Normally there was no problem, but on the odd occasion, the chrome would lift, which quickly led to piston failure. Doctor Ferdinand Piech, who in the late sixties and early seventies directed the technical side of the Porsche racing programme, recalled this to the editor when explaining why the switch was made to a nickel silicon carbide coating. We noted in our last issue the fact that the early development of the
Wankel rotary engine was bugged by ‘chatter marks’ caused on the aluminium rotor housing’s working surface by the apex seals running against it. The rotary’s apex seals are akin to piston rings, and chrome plating the complex epitrochoidal surface on which they ran did not provide a satisfactory solution. It was the development of a nickel matrix/silicon carbide coating that overcame the problem. Like the chrome plating it superseded, this coating was electrodeposited. The process uses nickel sulfate and ultra-fi ne silicon carbide particles in liquid form. This metal/ceramic composite bore coating is normally 0.05 mm to 0.1 mm (50-100 microns) thick after fi nish machining, which
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031 contents
• RACESHOP: MERCEDES- BENZ HIGH PERFORMANCE
ENGINES We venture inside the Brixworth Technical Centre where McLaren’s Grand Prix winning V8 is built
• MOTORCYCLE: HONDA &
PVRS How Honda is targeting a major performance step through its second attempt at a Pneumatic Valve Return System in MotoGP
• INSIGHT: MOUNTAIN MOTORS For some 7.0 litres is not enough – only 14 litres will do in the ceaseless quest for raw power, as we find out
• FOCUS: SURFACE COATINGS Our definitive guide to all types of advanced component surface coating for pistons, bores, valves, cams and so forth
• SPECIAL INVESTIGATION:
F1 ENERGY RECOVERY What we can expect from Kinetic Energy Recovery Systems in 2009 and a pointer to future heat recovery systems
• INSIGHT: JORDAN-SUZUKI The technology of the American team’s racing Superbike engine and how it is tackling the might of the factories
• EXPO News from Engine Expo
• IRED: WORLD OF OUTLAWS The 2008 engine builders
www.highpowermedia.com
ISSUE 031 race engine TECHNOLOGY JUNE/JULY 2008
MERCEDES-BENZ HIGH PERFORMANCE ENGINEERING • MOUNTAIN MOTORS • SURFACE COATINGS • KERS • JORDAN SUZUKI • WORLD OF OUTLAWS
issue
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