ISSUE 024 race engine TECHNOLOGY AUGUST 2007
AUDI V12 TURBO-DIESEL • LE MANS 2007 • VANCE & HINES • CON RODS • F1 2007 • ENGINE EXPO 2007 • DESMODROMIC
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Race Engine Technology issue 024 : AUGUST 2007
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FOCUS : CONNECTING RODS
Byron Hines: HARLEY-DAVIDSON WARRIOR
THE COMMUNICATIONS HUB OF THE RACING POWERTRAIN WORLD AUDI V12
TURBO-DIESEL Inside the Le Mans winner
FORMULA
ONE 2007 The 2.4 litre V8s at 19,000 rpm
DESMO IN
MOTOGP Ducati’s
winning edge?
Making the connection
Glen Smale discusses racing engine con rod technology with specialist manufacturers from around the world
M
aking the connection necessary between the top end and the bottom end of the racing engine solid yet as light and efficient as possible has never been more crucial than it is today. Increased pressure on
performance and durability has forced connecting rod manufacturers to consider exotic materials and futuristic designs in the pursuit of total performance.
MATERIALS
Whether produced from aluminium, steel or titanium, forged or billet, con rod materials and manufacturing processes differ from one supplier to the next. Brian Crower, Managing Director of Brian Crower, Inc in San Diego, California says: “Aerospace grade 4340 steel is our preferred material for most connecting rod applications”. Some manufacturers use forged blanks and then machine to a billet finish while some machine from flat bar. Crower notes that 4340 steel rods are cost
AUGUST 2007
effective, reliable and deliver a time tested solution for high horsepower applications. Aluminium rods are used for certain disciplines like drag racing, where high boost and/or nitrous are commonplace. While steel and titanium are stronger in terms of overall tensile strength, the aluminium alloy delivers the required ‘give’ during violent operation. However, the aluminium rod is essentially a disposable part, requiring frequent replacement.
“Compared to steel, titanium is a great choice if you’re spending other people’s money”, noted Crower. “At nearly $600 per rod, the
USA $20, UK £10, EUROPE e15
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On.indd 50-51 Crower MX
lightweight properties of the material are normally far outweighed by the drastic increase in the price of aerospace quality 6AL4V titanium alloy… but it is a very nice rod for the price.” Stefan Asplund is Managing Director of MX Composites AB in Linköping, Sweden a company that makes con rods in aluminium based Metal Matrix Composite (MMC). “The increased specific stiffness in these materials compared to conventional materials such as steel, aluminium and titanium makes it possible to achieve significant weight savings. We can make savings of 50%, or of 25% when compared to titanium due to the high specific strength of our materials”, Asplund explained. This weight saving on reciprocating and rotating mass has a great impact on engine performance, as power is increased throughout the rev range with reduced friction and vibration. Asplund notes that the combined effect is a completely transformed engine character that runs more smoothly “with a softer and quicker throttle response”.
Arrow
nonferrous materials”. Titanium is sometimes used by Carrillo in applications where weight is the primary driver in the design. Most of the Ti found in connecting rods is from the 6AL-4V family, although Carrillo has made rods using variants of 6-4. However, Ti has never been the low cost alternative
and is generally less durable than steel.
With input material comprising forged plates, the MX Composites MMC con rods are machined by a patented High Speed Machining method. According to Asplund this results in cost effective manufacturing and outstanding finish. The fine surfaces created by the machining methods make it possible to run these con rods without bearings and bushings. According to Cindy Verkooij, Marketing and Promotions Manager of Carrillo Industries in San Clemente, California: “Carrillo has been and remains primarily a steel connecting rod manufacturer. We do employ other material types when the operating parameters suggest an improvement or necessitate the properties that can be obtained from
The design requirements of aluminium con rods primarily centre around weight and dampening issues. “The dampening effect is driven from the relatively low Young’s Modulus (‘stiffness’) of aluminium as compared to steel or Ti. The lower stiffness can also create difficulties in controlling the center-to-center (piston-crank) distance of the rod in tension as well as bore integrity,” Verkooij explained. However aluminium also requires a comparatively large cross-sectional area to achieve the necessary strength, putting space (clearance) at a premium. Carrillo’s ‘Gen IV’ high-strength steel is an excellent material for con-rods and would be used in applications that require high strength, low weight and durability (fatigue life), and given space limitations. Verkooij outlined that the yield strength of this type of material would suggest a possible reduction in cross-sectional area throughout the rod, as long as attention is paid to the modulus. A properly designed and manufactured forging can optimise the properties of the material to the con-rod design and reduce manufacturing time. By optimising the grain flow of the material around the crank-side (big end) of the con-rod, this increases performance. Verkooij summarises: “Steel is probably the best choice for connecting rods as many race series prohibit the use of other materials anyway. There are instances where other materials should be employed, but this generally leads to higher costs”. Roslyn Arnold, Sales Manager at Arrow Precision Engineering Ltd
in Hinckley, Leicestershire, says: “Arrow uses EN24V for the vast majority of our steel rods. This is double air re-melt steel that we have drop forged, ensuring a better grain structure and lower sulphur content (0.25%), which means fewer inclusions and faults”. When forged, imperfections are reduced to an absolute minimum, ensuring consistency and it is suitable for most race applications. Arrow uses 6AL-4V titanium forgings in extreme performance situations such as World Superbikes, where a light drive train and low reciprocating weights gives instant throttle response and much lower gyroscopic forces, allowing the bike to turn in quicker. A 30% weight saving over steel makes a huge difference to the reciprocating mass of the rod and cap assembly, however they
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024 contents
• INSIGHT: FORMULA ONE 2007 Ian Bamsey assesses the mid -season state of the art in powertrain technology
• REPORT: LE MANS How the 24 hour race engines fared
• MOTORCYCLE:
DESMODROMIC Neil Spalding assesses Ducati’s continuing use of desmodromic valve actuation
• SUPPLY CHAIN:
VANCE & HINES How the Harley-Davidson specialist works with its suppliers
• PROFILE:
AUDI V12 TURBO-DIESEL Inside the pioneering double Le Mans winner
• GRID The Race Engine Technology world
• EXPO News from suppliers to race engine builders
• IRED: LE MANS The 24 Hour race engine builders • PS
F1 horsepower
• FOCUS: CON RODS Glen Smale discusses racing engine con rod technology with specialist manufacturers from around the world
• LETTER FROM: ENGINE EXPO New and refreshed technology on show
www.highpowermedia.com
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