Originally the Lexus IS-F was not part of any long-term strategy or corporate aim. It began with the enthusiasm of two engineers, Yaguchi-san and Sakamoto-san. Their personal enthusiasm for high performance had already led them to experiment with an older model Lexus IS300. With the debut of the new Lexus IS they continued to work upon advancing every aspect of the dynamics, while at the same time lobbying heavily at the highest management levels for support.
This level of commitment and expertise paid dividends. As the project grew and was presented to the higher executives, so internal feedback became more positive. The result was that in 2004 they were given the goahead for what had already become known internally as the ‘F' project.
Intense media, customer and distributor interest at the 2007 Frankfurt launch merely confirmed what many in the company already suspected: That the time was right for a real high performance challenger bearing the Lexus badge.
To create the Lexus IS-F several questions arose. The principle one is obviously what exactly a committed driver actually wants from his car. In fact what basic elements create driving excitement on the road and track? From this three wider areas of research arose: response: handling, engine and transmission response, sound and a feeling of unlimited acceleration.
Response
For a really discerning driver to fully enjoy the performance of his car three elements come immediately into play. Acceleration, braking and steering. The more directly the car responds to the driver's input, the more satisfying the experience becomes.
To power this dynamically refined response Lexus engineers developed a compact 5-litre V8 engine with advanced D-4S direct fuel injection, VVT-iE, hollow overhead camshafts, and electronic throttle, delivering 423 DIN hp. To ensure constant power delivery, even during 1G lateral acceleration turns, both a small fuel surge tank and high mounted oil scavenge pumps are fitted. Elsewhere racing technology also featured in the forged crankshaft, sintered con-rods and ultra rigid block casting techniques. The result is an engine which delivers instantaneous response anywhere in the rev range, giving the impression that the linear acceleration is virtually unending.
More important is the drivers feeling of control over this power. By developing the world's fastest 8-speed Sport Direct Shift (SPDS) transmission, which shifts in just 0.1 seconds, Lexus engineers delivered the kind of direct response formerly only found in motor sport. A major benefit of this transmission is that in M-mode the driver has complete control over these changes, and can hold any gear, using racing type paddles. However, for heavy traffic or relaxed cruising, in D-mode it performs like a normal (albeit very direct and precise) automatic transmission.
Full lock-up control is used during both acceleration and deceleration in 2nd gear and higher, without using the torque converter function. This enables changes in engine output to be transmitted directly, just like a manual transmission. If, however, engine speed is too low to allow lock-up, the torque converter function will also be used in 2nd gear and up.
The response and weight of the steering has also been fine-tuned for high performance driving. A new type of VDIM (Vehicle Dynamics Integrated Management system), automatically adjusts the setting of the power steering when the VDIM Sports mode is selected.
Also both the brakes and suspension were uprated. In fact detail lightening and modification of the suspension, brakes, wheels and tyres has reduced unsprung weight resulting in sharper, more directly responsive handling.
Sound
Finding the right sound for any exclusive car is a skilled and painstaking procedure. As a highly emotive area, the actual sound of the engine received high priority in developing the Lexus IS-F. The car's highly significant aural sound design falls into three distinct categories. In the low and medium speed range, the V8 engine creates a strong exhaust sound, while maintaining overall tranquility. When the higher speeds are reached, the second intake port opens, and the engine sound changes suddenly to an impressively powerful sound. As the engine approaches the maximum speed range, only the polished and pure mechanical sound of the engine can be heard, intensifying in synchronisation with the engine speed.
Acceleration
A car that accelerates, and then just goes on accelerating is the dream of many highly motivated drivers. To achieve this smooth and seamless feeling the size of the engine, the lightness of it's construction and the whole relationship between power, transmission and handling must be perfectly optimised with the overall weight of the vehicle. In delivering this accelerative performance the actual track testing of the Lexus IS-F, and the finely honed skills of some of the best test drivers in the world, have refined all of these aspects to produce both acceleration and a superbly balanced feeling of perfect control.
Engine
New directions in metallurgy and new developments in friction reduction are a major characteristic of the Lexus IS-F engine. Smooth, linear engine response involved providing a significant increase in the amount of valve lift and engine speed.
This has been made possible by the adoption of fixed pivots, lightweight high-rigidity roller rocker arms, and lightweight titanium intake valves. Friction in the camdrive system has been significantly reduced by using roller rocker arms with integrated low rolling resistance needle bearings. These improve rolling smoothness, contribute to improved fuel efficiency, and helped the engineers develop a more compact valve train layout. Lubrication for the rollers is provided through the pivot part of the roller rocker arms via an oil passage in the fixed pivot. High nickel content, heat resistant steel alloy has been used for the umbrella area of the exhaust valve increasing the overall high temperature durability.
Oil Cooler and Scavenge Pump
Maintaining valve train oil supply, especially under the high engine speeds and high cornering stresses generated by the Lexus IS-F has been efficiently ensured by a high mounted oil scavenge pump. This actively removes excess oil from the cylinder head area and returns it to the oil pan, so preventing oil surge problems even in 1G force turns during sporting driving. Keeping the oil supply at the correct operating temperature is also vital to maintaining reliable high engine speeds. For the Lexus IS-F a liquid-cooled oil cooler that uses the engine coolant is a major factor in both cooling the lubricant and preventing oil deterioration.
Advanced Camshaft Technology
Naturally the overhead camshafts that operate the valves have also been optimised for ultra-high performance. A composite camshaft that combines sinter forged cam lobes and hollow shafts has been developed, providing a significant weight reduction and durability bonus over conventional systems. In addition, using the hollow camshafts as oil passages allows the cylinder head oil passages to be simplified, further reducing weight.
Intake VVT-iE
To take maximum advantage of the advanced camshaft technology, the VVT drive has been uprated from hydraulic drive to an intelligent electric motor driven system (VVT-iE). As a result, the VVT operational control range has been extended to cover low engine speeds, where hydraulic pressure is at a disadvantage, making a major contribution to effortless low-range acceleration. As opposed to hydraulic systems, the VVT-iE's electric motor operating speed may be adjusted independently from the engine rpm level. This allows for very accurate camphase control.
Electronic Throttle
The electronic throttle uses a non-contact throttle sensor and DC electric motor. The throttle valve shaft has been machined down (from 10mm to 7mm) and the intake air passage area expanded to decrease intake resistance. this provides the Lexus IS-F with the dynamic throttle response expected for ultra-high performance, while also helping improve fuel efficiency.
Dual Intake System
Focusing on the sports characteristics of the engine, a dual intake system has been developed for the Lexus IS-F: for low and medium engine speeds, only the primary port is used. For high engine speeds, both the primary and secondary intakes are opened. As a result, in the low and medium engine speed ranges, calm smooth torque befitting Lexus is provided, while at high engine speeds powerful torque is provided, almost as if another engine has awakened.
Combustion Chambers
Increasing both fuel efficiency and power delivery demands sophisticated combustion chamber technology. The Lexus IS-F features pent roof combustion chambers with near centrally positioned spark plugs. By adopting a slanted squish profile swirl has been optimised resulting in more stable combustion, so that output performance and fuel efficiency have been optimised. Also air intake efficiency and output has been maximised by enlarging the valve diameter.
Piston Technology
Advanced piston technology, with steel-sintered conrods, has been instrumental in allowing higher compression ratios (11.8:1) and maximised combustion efficiency. A superior NV (Noise and Vibration) level has been realised by optimising the piston skirt shape and applying a highly wear resistant resin coating.
Crankshaft
For the high performance demanded of the Lexus IS-F, a matching higher level of crankshaft strength and rigidity was needed. This has been achieved by adopting a high strength, forged crankshaft. High frequency hardening was used for the fillet area to further ensure strength. Lightened and drilled balance weights have been optimally arranged and the permissible unbalance has been reduced to lower vibration and noise. A double torsional damper has been adopted for the crank pulley in order to reduce vibration and noise. The result is that the bottom end of the Lexus IS-F engine fully complements the smooth and quiet performance of the top end.
Timing Chain Cover
Keeping the V8 engine compact, yet delivering the highest power to weight efficiency was also a priority for the Lexus IS-F. By integrating the water pump, oil pump, and scavenge oil pump into the timing chain cover a significant weight reduction was achieved. Also, by optimally arranging the reinforcement ribs on the inner side of the timing chain cover, timing chain noise emission has been reduced without excessive weight penalties.
Transmission
The 8-speed geartrain of the Lexus IS-F has been specially developed to match and maximise the dynamic characteristics of the 5 litre V8. A transmission with a good balance of both close ratios and a wide ratio range, it has been designed to provide both seamless linear acceleration and fuel efficiency.
While 1st gear has been kept especially low to improve starting acceleration, 8th gear is set deliberately high to improve fuel efficiency at higher speeds. The intermediate gears are all close ratio, assuring smooth, powerful acceleration and optimum power and torque through the complete performance range.
The Direct change mechanism also enables changes to take place in much quicker time than any conventional or twin clutch system. In the case of the Lexus IS-F this takes just 0.1 seconds.
Torque Converter
To bring the Lexus IS-F powerfully and smoothly away from stationary, a newly developed torque converter, specifically designed for the greater torque of the 5-litre engine, but no larger than that of a 6 speed automatic transmission, has been adopted. In M mode, this torque converter functions only on 1st gear where the additional torque characteristics add effortlessness.
Weight Saving Design and Construction
As with all the mechanical elements of the Lexus IS-F, weight saving was a high priority in the transmission development. The adoption of a one-piece aluminium construction for the casing has achieved a meaningful weight reduction. The compact design ensures that the axial length and transmission diameter is the same as that of a conventional 6-speed transmission.
In view of the high demands of ultra-high performance driving, an air-cooled ATF (Automatic Transmission Fluid) cooler is adopted to ensure adequate cooling performance and unfailingly responsive gear shifting for circuit driving. Additionally, a new breather system will avoid loss of transmission fluid in very fast turns or under extremely hard braking.
Driving Pleasure and Stability
To endow the Lexus IS-F with the perfect blend of handling and control the Lexus state-of-the-art Vehicle Dynamics Integrated Management (VDIM) system has been specially adapted for ultra-high performance. By effectively managing control aspects such as the ABS, traction control, Electronically Controlled Brake LSD (Limited Slip Differential) and VSC (Vehicle Stability Control), this enhances every aspect of Lexus IS-F track performance and on-road behaviour.
It also controls the three distinct gearshift modes, Sport, Normal and Snow automatically adjusting the electrically driven power steering to match whichever of these is selected. In Sport mode the level of drift is such that the VDIM only cuts in as significant drift is achieved, allowing really spirited driving. In fact this aspect of the VDIM means that it actually assists drivers of all skill levels in achieving optimum lines, so helping increase driving performance. The result is that even the finest test drivers were able to lap the Fuji speedway faster with the VDIM in Sport mode than with it switched off.
And here lies another unique facet of the Lexus IS-F. For those who love to drive adventurously, the VDIM can be completely switched off allowing spectacular power slides. But naturally this does not leave the driver with an uncontrollable car, far from it. Even when the VSC is switched off, the Electronically Controlled Brake LSD remains activated, offering the driver similar handling and braking properties to those enjoyed by race and rally drivers.
Steering
Positive, precise and perfectly placed steering under all conditions is a pre-requisite of performance driving. The tilt and telescope column of the electrically powered rising rate steering of the Lexus IS-F is controlled by the 3-way seat position memory and automatically retracts for easy driver access. A new playless jointing system ensures that the feel is always direct and positive. The assist characteristics can be changed, offering a choice between Sport mode for a heavier steering feel, and Normal mode for everyday driving comfort. For extra comfort the leather covering has been tailored in just two sections. The audio, navigation and communication controls are all integrated into the spokes for optimum high-speed operating convenience.
Brakes, Wheels and Tyres
In creating ultimate driver confidence and satisfaction, extracting maximum controlled stopping power from the brakes received high priority. For this reason, 360mm ventilated and drilled, 6-piston front brakes coupled with 345mm 2-piston rear brakes were jointly developed together with Brembo. These deliver optimum braking performance and respond perfectly to mercilessly repeated demand under even the worst conditions.
Forged, sculptured 19-inch alloy wheels developed jointly with BBS also help reduce unsprung weight to near full-race efficiency. Together with ultra-low profile tires developed with both Bridgestone and Michelin they were essential in delivering the increased grip and flexibility, together with the special smooth road manners of the Lexus IS-F.
Suspension
Performance, power and braking are nothing without the control that transmits them to the road. To refine the suspension of the Lexus IS-F, engineers used a data gathering system more usually associated with racing cars to analyse the suspension behavior under every condition. This led them to re-evaluate every aspect, even the bushings. The result is a suspension system that has been lightened, reworked and fully optimized to complement the dynamic performance of the car.
Front Suspension
For precise steering with perfect turn-in, the front coil and wishbone suspension received a full-mechanical makeover. Weight was reduced using high tensile sheet steel for the suspension arms and aluminium for the steering knuckles.
High-rate springs with early activating bump stops were used to reduce roll angle when cornering and nosedive under braking. Also large-diameter anti-roll bars to increase roll rigidity, while simultaneously optimising roll posture, are complemented by hub bearings that have been exclusively developed for the Lexus IS-F. This whole assembly, matched by larger diameter monotube gas-filled shock absorbers, ensures not only reliability, but superb traction during high G-force corning.
Rear Suspension
The state-of-the-art multilink rear suspension for the Lexus IS-F also received the type of attention usually reserved for circuit racers. The result is a car that clings to the road under all road conditions, and every performance demand. To ensure this all-round precision, higher-rated springs were adopted to reduce both cornering roll, squat and braking dive. Again an early activated bump stop helps to reduce cornering roll, as does the adoption of high-pressure gas filled shocks, which also provide improved early linear response.
The length of the upper arms has been changed, optimising alignment and enhancing tire grip, while the characteristics of the torque control arm bushings have been tuned to offer optimum toe-in variation under cornering stresses. The rear suspension member cushions have been stiffened, both to reduce sway and increase stability when braking and accelerating. In addition, the whole mounting position of the rear suspension has been optimised to maximise every aspect of road holding.
Source: Lexus
