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Written by Ian Adcock
Ferrari engineers have further refined the 458 Italia model with a new turbocharged and downsized engine and revised aerodynamics to create the 488 GTB. The company downsized its all-new dry-sump V8 not only for emissions, but also to increase engine power by turbocharging, explained Michael Leiters, Ferrari"s Chief Technical Officer. The headline figures for the 3902-cm engine are 493 kW (661 hp) at 8000 rpm and 760 N m (561 lb ft) peak torque in seventh gear. "It"s very important with a downsized turbo engine that the performance and response is the same as a naturally aspirated engine, with no turbo lag." To achieve that, Maranello"s engineers fine tuned the sizing and tuning of the turbos, including light weight titanium-aluminum (TiAl) twin scroll turbines for minimum inertia and using ball bearing mounted shafts specially designed by IHI for this installation. Leiters explained that the equal-length inlet manifolds not only helped with turbine response but, together with the flat plane crankshaft, retained Ferrari"s distinctive engine note. "We"re very proud to have created a typical sound you"d expect from a Ferrari. In addition, the twin-scroll technology directs exhaust gases from each cylinder through separate scrolls, increasing the efficiency of the exhaust pulses for maximum power. A specially designed seal on the turbine housing ensures a minimum gap between it and the compressor wheel for maximum efficiency. All these solutions, claims Ferrari, contribute to the class-leading response time with no turbo lag. For instance, throttle response time is just 0.8 s at 2000 rpm in third gear. Consequently, the 488 GTB sprints from 0-62 mph (0-100 km/h) in 3 s flat and from 0-124 mph (0-200 km/h) in just 8.3 s with a top speed of 205 mph (330 km/h). Additionally, opting for a flat-plane crankshaft architecture helps to achieve maximum compactness, lowers mass, and helps to improve the engine"s internal fluid dynamics by ensuring equal pulse spacing and, therefore, balance between the cylinders. A compression ratio of 9.5:1 is combined with a maximum boost of 1.8 bar (26 psi), but Leiters explained that each ratio has a unique engine map to simulate the acceleration of a normally aspirated car while achieving maximum torque in seventh gear: "We did this for the California T, but we"re the only manufacturer who does it this way really to get this instant response." The multi-nozzle direct fuel injection runs at 2900 psi (20 MPa), delivering up to four injections per combustion cycle. As a result combined fuel economy on the European cycle is a claimed 24.8 mpg with CO2 emissions of 260 g/km. New high-tumble intake ports are specially shaped to optimize the flow coefficient and swirl motion in the combustion chamber for a homogeneous charge even at high revs. The new V8 also has an ion-sensing system that measures ionizing currents to control ignition timing and adaptively predict misfires. A multi-spark function enables the spark advance to be maximized at all revs. Mechanical efficiency is further enhanced by an oil pump that supplies lubricant variably at high or low pressure, reducing hydraulic power requirements by up to 30% compared to a conventional pump. Cylinder heads with roller finger followers reduce the power absorbed by the valvetrain by 10% at low revs thanks to the reduction of friction between the valve stems, tappets, camshafts, and finger follower rollers. Large bore exhausts with bypass valves have been engineered to contribute towards maximizing the exhaust note. Future developments, predicted Leiters, would include higher pressure injection systems, mapping and turbo packaging would allow Ferrari to reduce emissions even further, and there will be (at some point) electrification of ancillaries, including air conditioning and oil/water pumps. "I don"t believe that, in the next 5 to 8 years, there will be such dramatic demands that we can"t continue to offer a naturally aspirated V12, although we will have to continue to work on emissions." Maximized acceleration is achieved by Variable Torque Management that deliver increasing amounts of torque through the gears so maximum in fourth gear is achieved in 6 s from standstill. Ferrari"s Side Slip Control System, SSC2, has been enhanced to be more subtle and boost longitudinal acceleration out of corners by 12%; it also controls the cars active magnetorheological dampers as well as the F1-Trac and E-Diff. The dampers are now controlled by a faster ECU with three new sensors on the body, while the ESP is 8% quicker than before thanks to new soft and hardware. Integral to the car"s performance is its aerodynamics, with Maranello claiming a 50% increase in downforce over the outgoing 458 model despite drag being reduced. The front of the car is dominated by its central Aero pillar and an F1-inspired double spoiler, the top element of which is designed to work in conjunction with the duct and manage airflow into the radiator. The larger, lower section generates suction which pulls the air flow towards the lower part of the underbody, generating downforce. The Aero pillar"s job is managing the powerful air flows striking the front of the car and distributing them along both the longitudinal and transverse planes. On the longitudinal plane on the lower section, it accelerates and directs an extremely fast flow to the central underbody, while on the upper section"s transverse plan flow is deflected towards the radiator opening, controlling its expansion to improve the efficiency of the radiating masses. The 488 GTB also has an innovative aerodynamic underbody that incorporates vortex generators, special curved aerodynamic appendages that accelerate the air thereby reducing pressure. The result is that the car"s underbody is "sucked" down to the ground, increasing downforce but not drag. The front section of the underbody is flat, generating downforce, which pushes the car lower to the ground while having the smallest possible impact on the flow arriving at the front strakes, contributing to an overall downforce of 716 lb (325 kg) at 155 mph (250 km/h). A large rear diffuser with curved fences optimizes the expansion of the huge amount of air channeled under the car, boosting downforce. They also protect the diffuser"s internal channels from the turbulence generated by the rear wheels, thereby reducing drag. The rear diffuser features variable flap geometry controlled by a CPU, integrated with other vehicle control systems, which modifies the expansion of the diffuser. Depending on the driving conditions, this adjusts the balance between increased downforce (with flaps closed, in corners and under braking) and drag reduction (with flaps open, on straights and under acceleration). The blown spoiler is a new solution. Air enters an intake at the base of the rear screen and exits via the bumper. This geometry enables the surface taking the aerodynamic load to have a more pronounced curvature that, in turn, increases the upward deflection of the flow on the rear screen, again boosting downforce. This solution avoids having to extend the height of the rear spoiler and thus helps keep drag low. The base bleed air intakes on the car"s sides are divided by a central flap. The flow over the upper part of the flap, which is also used for the engine air intake, is deflected and exits from the tail area to reduce the drag caused by the low pressure wake directly behind the car. The effect is created by the airflow exiting under pressure at the rear, which energizes the wake that forms at the end of the car"s tail, moving it further from the tail where it interferes less with the car"s aerodynamics. The flow from the lower part of the flap goes to the intercoolers to cool the intake charge.
Date: 12-Mar-2015 11:34 EDT
More of this article on the SAE International website
ID: 1235
Ferrari engineers have further refined the 458 Italia model with a new turbocharged and downsized engine and revised aerodynamics to create the 488 GTB. The company downsized its all-new dry-sump V8 not only for emissions, but also to increase engine power by turbocharging, explained Michael Leiters, Ferrari"s Chief Technical Officer. The headline figures for the 3902-cm engine are 493 kW (661 hp) at 8000 rpm and 760 N m (561 lb ft) peak torque in seventh gear. "It"s very important with a downsized turbo engine that the performance and response is the same as a naturally aspirated engine, with no turbo lag." To achieve that, Maranello"s engineers fine tuned the sizing and tuning of the turbos, including light weight titanium-aluminum (TiAl) twin scroll turbines for minimum inertia and using ball bearing mounted shafts specially designed by IHI for this installation. Leiters explained that the equal-length inlet manifolds not only helped with turbine response but, together with the flat plane crankshaft, retained Ferrari"s distinctive engine note. "We"re very proud to have created a typical sound you"d expect from a Ferrari. In addition, the twin-scroll technology directs exhaust gases from each cylinder through separate scrolls, increasing the efficiency of the exhaust pulses for maximum power. A specially designed seal on the turbine housing ensures a minimum gap between it and the compressor wheel for maximum efficiency. All these solutions, claims Ferrari, contribute to the class-leading response time with no turbo lag. For instance, throttle response time is just 0.8 s at 2000 rpm in third gear. Consequently, the 488 GTB sprints from 0-62 mph (0-100 km/h) in 3 s flat and from 0-124 mph (0-200 km/h) in just 8.3 s with a top speed of 205 mph (330 km/h). Additionally, opting for a flat-plane crankshaft architecture helps to achieve maximum compactness, lowers mass, and helps to improve the engine"s internal fluid dynamics by ensuring equal pulse spacing and, therefore, balance between the cylinders. A compression ratio of 9.5:1 is combined with a maximum boost of 1.8 bar (26 psi), but Leiters explained that each ratio has a unique engine map to simulate the acceleration of a normally aspirated car while achieving maximum torque in seventh gear: "We did this for the California T, but we"re the only manufacturer who does it this way really to get this instant response." The multi-nozzle direct fuel injection runs at 2900 psi (20 MPa), delivering up to four injections per combustion cycle. As a result combined fuel economy on the European cycle is a claimed 24.8 mpg with CO2 emissions of 260 g/km. New high-tumble intake ports are specially shaped to optimize the flow coefficient and swirl motion in the combustion chamber for a homogeneous charge even at high revs. The new V8 also has an ion-sensing system that measures ionizing currents to control ignition timing and adaptively predict misfires. A multi-spark function enables the spark advance to be maximized at all revs. Mechanical efficiency is further enhanced by an oil pump that supplies lubricant variably at high or low pressure, reducing hydraulic power requirements by up to 30% compared to a conventional pump. Cylinder heads with roller finger followers reduce the power absorbed by the valvetrain by 10% at low revs thanks to the reduction of friction between the valve stems, tappets, camshafts, and finger follower rollers. Large bore exhausts with bypass valves have been engineered to contribute towards maximizing the exhaust note. Future developments, predicted Leiters, would include higher pressure injection systems, mapping and turbo packaging would allow Ferrari to reduce emissions even further, and there will be (at some point) electrification of ancillaries, including air conditioning and oil/water pumps. "I don"t believe that, in the next 5 to 8 years, there will be such dramatic demands that we can"t continue to offer a naturally aspirated V12, although we will have to continue to work on emissions." Maximized acceleration is achieved by Variable Torque Management that deliver increasing amounts of torque through the gears so maximum in fourth gear is achieved in 6 s from standstill. Ferrari"s Side Slip Control System, SSC2, has been enhanced to be more subtle and boost longitudinal acceleration out of corners by 12%; it also controls the cars active magnetorheological dampers as well as the F1-Trac and E-Diff. The dampers are now controlled by a faster ECU with three new sensors on the body, while the ESP is 8% quicker than before thanks to new soft and hardware. Integral to the car"s performance is its aerodynamics, with Maranello claiming a 50% increase in downforce over the outgoing 458 model despite drag being reduced. The front of the car is dominated by its central Aero pillar and an F1-inspired double spoiler, the top element of which is designed to work in conjunction with the duct and manage airflow into the radiator. The larger, lower section generates suction which pulls the air flow towards the lower part of the underbody, generating downforce. The Aero pillar"s job is managing the powerful air flows striking the front of the car and distributing them along both the longitudinal and transverse planes. On the longitudinal plane on the lower section, it accelerates and directs an extremely fast flow to the central underbody, while on the upper section"s transverse plan flow is deflected towards the radiator opening, controlling its expansion to improve the efficiency of the radiating masses. The 488 GTB also has an innovative aerodynamic underbody that incorporates vortex generators, special curved aerodynamic appendages that accelerate the air thereby reducing pressure. The result is that the car"s underbody is "sucked" down to the ground, increasing downforce but not drag. The front section of the underbody is flat, generating downforce, which pushes the car lower to the ground while having the smallest possible impact on the flow arriving at the front strakes, contributing to an overall downforce of 716 lb (325 kg) at 155 mph (250 km/h). A large rear diffuser with curved fences optimizes the expansion of the huge amount of air channeled under the car, boosting downforce. They also protect the diffuser"s internal channels from the turbulence generated by the rear wheels, thereby reducing drag. The rear diffuser features variable flap geometry controlled by a CPU, integrated with other vehicle control systems, which modifies the expansion of the diffuser. Depending on the driving conditions, this adjusts the balance between increased downforce (with flaps closed, in corners and under braking) and drag reduction (with flaps open, on straights and under acceleration). The blown spoiler is a new solution. Air enters an intake at the base of the rear screen and exits via the bumper. This geometry enables the surface taking the aerodynamic load to have a more pronounced curvature that, in turn, increases the upward deflection of the flow on the rear screen, again boosting downforce. This solution avoids having to extend the height of the rear spoiler and thus helps keep drag low. The base bleed air intakes on the car"s sides are divided by a central flap. The flow over the upper part of the flap, which is also used for the engine air intake, is deflected and exits from the tail area to reduce the drag caused by the low pressure wake directly behind the car. The effect is created by the airflow exiting under pressure at the rear, which energizes the wake that forms at the end of the car"s tail, moving it further from the tail where it interferes less with the car"s aerodynamics. The flow from the lower part of the flap goes to the intercoolers to cool the intake charge.
Date: 12-Mar-2015 11:34 EDT
More of this article on the SAE International website
ID: 1235
