BMW is claiming this to be the third generation of M6 vehicles, tracing its origins back to the original 1987 E24 model, even though it only bore the M635csi designation in Europe.
Pedantics aside, owners of the previous V10 model should appreciate 10% more power with 30% more torque, yet fuel consumption and emissions are reduced by 30%.
As we said, it does this with the M5’s V8, which in turn is based on the S63 motor found in the X5 M and X6 M SUV models. A higher rev limit (200rpm more at 7200rpm), software, exhaust and intercooler changes allow the revised engine (known as S63Tü). It also develops slightly more boost –21.7psi against 17.4psi for the S63. This allows it to produce 560hp at 5750rpm (versus 555hp at 6000rpm for the S63). Maximum torque is the same at 500 lb-ft but it runs to 5750rpm versus 5650rpm in the SUVs.
The instant power delivery results in acceleration figures of 0-62mph in 4.2sec for the Coupe and 4.3sec for the Convertible. The sprint from 0–124mph (0-200km/h) takes only 12.6sec for the Coupe, 13.1 for the Convertible. The top speed of both models is electronically limited to 155mph.
Both 4.4-liter engines use a similar reverse-flow V8 layout where the two twin-scroll turbos are placed in the vee between the cylinder heads (along with the cats). This results in an unusual engine where the intake is moved outboard and the exhaust inboard. The lengths of intake and exhaust tracts are therefore reduced and their diameters increased, reducing pressure losses on the exhaust side. A further advantage is a quicker warm-up of the cats to reduce cold-start emissions.
The direct fuel injection also plays a role in the combination of high performance and fuel efficiency. The injectors spray fuel at a maximum pressure of nearly 3000psi, with new solenoid valve injectors allowing multiple injections per combustion cycle to achieve a precise mixture. The fuel also has a cooling effect on the combustion process, making a 10:1 compression ratio possible.
Other engine technologies include individual throttle plates and BMW’s Valvetronic variable valve control system as well as the Double Vanos variable valve timing system. In addition, a volume-controlled oil pump and a range of other EfficientDynamics measures deliver efficiency, such as Brake Energy Regeneration and Auto Start-Stop.
The new V8 is mated to a newly developed seven-speed double-clutch transmission designed to handle the high torque of the engine. The M DCT with Drivelogic System has been tuned to the performance characteristics of the engine. It delivers fast changes in both automatic mode (D) and manual mode (S) using the shift lever of paddles. No clutch pedal is required for manual gearshifts and the driver can keep their foot on the accelerator during gear changes. Comfort is further enhanced by the new Low Speed Assistance function, which smoothes power delivery in stop-and-go traffic with a light touch of the accelerator pedal.
M DCT with Drivelogic offers three shift programs in both automatic and manual mode. The driver selects the desired mode using the rocker switch below the shift lever. The D1 program is selected automatically, tailoring gear selection to deliver the most efficient possible driving style. D2 supports laid-back cruising with gear changes carried out according to engine revs and load. And, to promote a sporty driving style, shifting in D3 mode allows the engine to climb higher up the rev range.
Drivers can also adapt the shift characteristics to their requirements in Manual mode. S1 mode generates comfortable and smooth gear changes. S2 is noticeably faster and accompanied by significant shift kick at higher revs. S3 enables sportier gear changes and is required to initiate the Launch Control function.
When the stability control system is switched off, Launch Control allows the driver to achieve maximum acceleration from a standstill as permitted by conditions. During Launch Control acceleration, each gearshift takes place automatically and at the optimum engine speed.
Chassis
The Active M Differential in the new M6 is an electronically controlled multi-plate limited-slip diff programmed to optimize traction, stability and sporting character.
The LSD control unit is connected to the Dynamic Stability Control (DSC) system via FlexRay high-speed data transfer technology and cross-checks data collected by its sensors with feedback from DSC. It then uses this information to calculate the locking force required to deliver optimum traction and stability. The locking force of the differential is varied continuously between 0-100%.
The data provided by DSC to the Active M Diff also accounts for throttle position, wheel speed and the car’s yaw rate. Every driving situation is analyzed so any loss of traction is identified at an early stage. The degree of diff lock is adjusted as required within a fraction of a second, enabling wheelspin to be prevented on slippery surfaces and in tight corners.
The integral rear axle subframe of the M6 is rigidly bolted to the body to maximize rigidity and handling precision. Reinforced chassis mountings at the front and rear axles ensure dynamic forces are passed through to the body structure. New forged aluminum suspension components boast strength and less weight to meet the requirements of everyday driving and the demands of track use.