The honda 4.0L is a v10 estimated at 510hp, its been confirmend that its going to be in the new NSX. Honda puts an amazing amount of R&D into the engines it builds, because they have the money and the drive to. look at their presence in F1. when your talking about hp per litre is more a argument on effiency, and the technology thats in the engine. if honda put the technology that they put into their performance 4cyl and made a v8 or in this case a 4.0L v10.. just look out.