This japanese article shows RA161H vs RA617H. (Chrome is good for autotranslate. Bad for memory/disc.)
https://motor-fan.jp/article/10002128
I thought Honda wanted the "log" exhaust manifold of the RA615H.
I thought most of the efficiency/power problem in the turbo hybrids is the ICE not the ERS. Brilliant obfuscation by Mercedes. We don't get to see any of the internals. Everybody else has been chasing ERS efficiency with limited tokens, whilst Mercedes was sitting on superior ICE combustion. (So do they use their daimler patent system and not Mahle's TJI??) Nobody can see what the ICE combustion concept is. And F1 should deregulate it more, since the regs stop further exploration.
I can't see why Honda can't leapfrog with a novel combustion concept. Would love to know what things they have tried in their single cylinder models on computer and in metal.