Mudflap wrote: ↑10 Dec 2017, 20:27
I bought the autosport magazine and they have a pretty good report on what went on with Honda throughout the year. There are quite extensive Hasegawa quotes - I'll try to summarize the ones I find important.
In 2015 their H recovery was very poor, so for 2016 they increased the turbine size and as a result had to move the turbo up. This however increased the CG height so for 2017 they decided to go for the split turbo. As the compressor housing was now forward of the block, the oil tank had to be redesigned into a mercedes-like crescent shape. Unfortunately this caused all the issues they had in pre-season testing and took 2-3 days to fix.
Now the way I see it, McL would have provided Honda with the oil tank accelerations. Honda would then have tested the oil tank on a shaker rig (I think these are also known as rodeo rigs) to validate the design. I don't think it can be determined from the statements whose blame it was - either McL's for miscalculating acceleration (or not providing any at all) or Honda's for not testing the oil tank correctly.
On the issue of power Hasegawa explicitly states that
top end power (at the start of the season) was virtually the same as 2016 while bottom end power was lower. He describes a significant torque hole between 9000-10000 rpm which combined with higher than expected driveline inertia created very strong oscillations during gearshifts. Essentially, the engine side inertia was very low compared to driveline inertia, causing it to bog down under upshifts. As a consequence the driveability was very poor due to low end torque and having to shift at non-optimal engine speeds.
I see Honda as being solely responsible for the lack of engine performance, however in my view McL should take all responsibility for the issue of driveline inertia. It is very unlikely that they had communicated correct driveline specifications and Honda had chosen to ignore them.
Hasegawa then goes on to say that the low speed torque issue was addressed by a change in inlet manifold design (introduced in Barcelona). I suppose this had to do with the poor performance noted in media when testing the complete engine rather than the single cylinder. They also mention altering clutch settings - these I suppose have to do with reducing the clutch preload to allow a bit of slip and alleviate the torque spike.
Finally Hasegawa attributes the MGUH bearing failures to a new 'oil blowing' used for 2017. This is not explained at all but I suspect that oil blowing is just an air line from the 'foam side' of the oil tank that allows the bearing cavities to be scavenged. Unlike the crankcase which can be scavenged without an air line due to blow-by, other cavities typically require a 'breathing' orifice with a restrictor that is adjusted to achieve the required cavity pressure.
These scavenge breathers have been used for a very long time in dry-sump racing engines and are very well understood. I fail to see what could have gone wrong - most likely the oil was not well separated in the tank and made its way into the air line, effectively preventing the bearing from being scavenged? Could the excess oil on the bearing and shaft increase dynamic loads and cause bearing failures ?
Anyway, according to the article, it took Honda quite a long time to understand what was happening and in the end they had to modify the oil tank to stop this 'oil blowing' and increase the size of the bearing.
Unfortunately the way I see it the MGUH failures were entirely Honda's doing.
