ON HOME TURF
It has become a tradition in the Land of the Rising Sun: at its home race at Suzuka, Honda put its engine on display, exposing the layout of the RA618H that powers the Toro Rossos of Pierre Gasly and Brendon Hartley.
The Japanese V6 has retained the split architecture of its predecessors: turbine and compressor are dissociated and connected by a shaft on which is mounted the MGU-H. Since 2017, the compressor is no longer housed inside the "V" formed by the two banks of cylinders, but is installed at the front of the block, like the Mercedes V6. This positioning helped increase the size of the compressor and therefore the power, but it forced a redesign of the fuel tank, hollowed out like its counter-part on the Anglo-German engine.
As can be seen in the picture above, the compressor is fed with air by a periscope-shaped carbon duct, which passes through the oil tank, pierced in the middle (see the yellow arrow). On top are the two entries (purple arrows) through which compressed and cooled air (after passing through the intercooler) enters the air box.
One can also see one of the two direct injection pumps (red arrow). Driven by cam shafts, these pumps (one for each cylinder bank) deliver 500bar of pressure to the injector.
There are also three-phase cables (orange, as on all other engines) that transfer the AC power to the control box: it converts electricity to direct current so that the battery can store it. The green cable connects the MGU-H to the control unit, which is connected to the MGU-K by the blue cable.
Seen from behind, the Japanese six-cylinder shows the air box (yellow arrow), the two pipes of the wastegate (blue arrows), the turbine (red arrow) and the clutch, here hidden by a black cover (green arrow).
On the Honda block, the clutch is mounted on the thermal block rather than on the gearbox. The relatively low engine speed of the turbo V6 (limited to 15,000rpm) makes it possible to attach the clutch to the engine, a solution already seen in the past and preferable in view of the significant increase in torque compared to the previous atmospheric V8. This configuration is identical to the one used by Mercedes.