The engine rules say:
A maximum of 4MJ per lap can be used from the battery per lap by the MGU K
A maximum of 2MJ per lap can be harvested from the MGU K to the battery.
A unlimited amount of energy may be harvested by the MGU H.
The MGU K can only use 4 MJ per lap from the battery, but it does not prohibit direct transfer from harvest from the H to the K, so you can get around the max 4 MJ per lap on the K this way.
The MGU H does not provide any real torque to the drivetrain, all it does is spool up the turbo faster to eliminate it's natural lag.
These turbo's the teams have might very well run perfectly enough pressure for the allowed fuel mixture at around 75000 rpm depending on the size, weight and inertia of the turbo, sofor max ICE efficiency going any higher would be useless, since you are not allowed to use more fuel for the extra air higher RPM's of the turbo's would entail. So what if you placed a blow off valve before the plenum that would control the exact amount of pressure you want for the fuel allowance you have, this would allow the turbo and thus the mgu h to spool up to it's maximum 125000 rpm allowed.
So the car gets 2 MJ per lap back from the MGU K. So per lap it generates 50% of it's allowed use from the battery That leaves 2 MJ extra it can take from the battery gathered by the MGU H. But after these 2 MJs it's pointless to put more energy in the battery from the MGU H. So what if Ferrari figured lets bypass the battery and feed the extra energy we get by running the turbo/mgu H this much faster then it's optimum ICE window and feed that extra energy straight back into the MGU K, which bypasses the 4 MJ limit.
So if this is what they are doing now then we're likely to see a massive rush by the teams to oversized turbos with massive mass in them to get as high an inertia and potential energy in the MGUH/TURBO shaft.
This would also explain the very high pitched Ferrari downshifts in qualifying mode, it sounds like the turbo has lots of overspeed and the blow off valve is wide open. I think Ferrari has a massive turbo in mass and thats whats doing it for them.
I mean, just the sound difference between the two, here is Ham's pole lap in Paul Ricard
https://www.youtube.com/watch?v=8D_uhuf3UkI
Vettels pole lap in Germany:
https://www.youtube.com/watch?v=Bs_LIBPTAdg
You can just hear the massive turbo sound in the Ferrari all the way through the gears and on downshifts compared to the Mercedes.
This also explains the Ferrari smoke machine on start up, to run things at 50k rpm more then others would require alot thinner oil, and alot more of it. Especially to prime it before start up.
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