beautifully engineered

The Lexus LFA is Beautifully Engineered

If any road-going car deserves recognition for its engineering, the LFA makes the top spot by a mile.

Concept

The Lexus LFA is a 2-seat exotic sports coupe produced by Lexus as a concept car, “halo” vehicle, racing prototype, and production model. It is the second model in the F marque line of performance vehicles from Lexus, following the IS F. Three concept versions have been shown, each debuting at the North American International Auto Show with the LF-A designation as part of the LF Series concept line. The first LF-A concept premiered in 2005, followed in 2007 by a second LF-A with a more completely furnished interior and exterior. The third version of the LF-A, a roadster model, premiered in 2008. The production model, trademarked LFA, was shown at the Tokyo Motor Show in October 2009.

The production Lexus LFA features a new V10 engine and a carbon fiber-reinforced polymer (CFRP) body. CFRP materials account for 65 percent of the LFA’s body composition by mass. The LFA went into production in late 2010, with a projected run of 500 vehicles at the base price of US$375,000. A circuit-tuned variant, named “Nurburgring Edition”, has just been released. This variant holds the fastest Nurburgring Nordschleife time for a production car; 7:14.64 (as of 10/25/11).

Engine

The Lexus LFA is powered by a 72-degree bank angle 4.8-liter V10 engine equipped with dual VVT-i carrying the 1LR-GUE designation with a maximum output of 412 kW (560 PS) delivered at 8,700 rpm. Its maximum torque output of 480 N·m (354 lb·ft) arrives at 6,800 rpm, 90 percent of which is available from 3,700 rpm. The engine redlines at 9,000 rpm, but with a fuel cutoff set at 9,500 rpm, and is constructed using forged aluminum pistons, forged titanium connecting rods, and solid titanium valves. The V angle of the LFA’s V-10 engine is set to 72-degrees (as opposed to the 90-degree V angle present in a Dodge Viper’s V-10) to fully balance the firing force from the pistons. This 72-degree angle allows for even firing from the pistons without the use of a split-journal crankshaft, thus improving engine efficiency as well as lowering overall weight. Dry sump lubrication prevents engine oil starvation through high speed corners and lowers the engine’s center of mass. Air is fed directly from beneath the hood through a visible slit passing into a dual stage variable intake manifold and then into ten individual throttle bodies before finally exiting from a dual stage titanium muffler.

The LFA’s engineers selected a V10 engine over an equivalent displacement V8 engine for its ability to rev higher, and over a V12 for its lower reciprocating mass, allowing for more rapid engine response. Lexus claims their engine can rev from idle to its redline in 0.6 seconds and an analog tachometer needle could not accurately track the LFA’s changes in engine speeds. This necessitated the use of a digital tachometer which can instantly display engine speed. The engine reportedly weighs less than the manufacturer’s own 3.5-liter 2GR-FE V6 engine. Engineers attempted to make the engine sound like that of a Formula One car with high revs, while at the same time maintaining reliability and vibration control. Along with other manufacturers such as Ferrari, Toyota had produced their own F1 engines and chassis designs. The exhaust note has been described by Toyota engineers as the “roar of an angel”, and a US television spot later used the engine sound to shatter a champagne glass via resonance frequency.

Transmission

The gearbox itself is a six-speed Automated Sequential Gearbox (electrohydraulic transmission) operated with paddle-shifters developed and constructed in-house by Toyota. The driver can select from four settings: auto, normal, sport, and wet. The manufacturer quotes minimum up-shift times of 200 ms in the sport mode. According to Tanahashi a dual-clutch transmission was tested but the design team felt gear changes were overly smooth, resembling that of a traditional automatic and they preferred more abrupt and mechanically engaging shifts. This shifting experience was also favored despite Lexus vehicles’ typical emphasis on smooth operation. The auto mode and low speed performance suffer as a result. A Torsen limited slip differential is also applied on the LFA, and a launch control system is available. An offset gear mounted to the crank (a world first) sends power via a torque tube to the transmission. The carbon-fiber torque tube system was developed because of the rear placement of the transmission and low engine layout.

Chassis

The Lexus LFA’s frame is made from an in-house designed and manufactured carbon fiber-reinforced polymer (CFRP) center monocoque with aluminum front and rear subframes. The subframes, which can be removed and replaced minimizing potential repair costs, are joined to the monocoque using a newly developed aluminum flanged collar designed to create a stronger joint. According to the manufacturer, the quality of the CRFP material matches that of aeronautical grades and is woven by a laser monitored circular loom, one of only two in the world. Overall 65% of the vehicle’s total body mass is CFRP material while the remaining 35% is aluminum. Manufacturer data indicates that the use of CFRP saves 100 kg (220 lbs) over equivalent aluminum materials.

Performance