Honda Underseat Exhaust Patent Hints at V4 Supersport


Categories: Technology, Racing, Design, Sportbikes

Honda Underseat Exhaust Patent Hints at V4 Supersport

Hey! Remember the awful underseat exhaust trend on sportbikes? Honda does, and if these newly released patent drawings are anything to go by, Big Red is eager to bring those days back.

But that’s only part of the story here. Take a close look at the drawings and you’ll see there are, in fact, two exhaust banks: one ending with a muffler on the right side and the other with a convoluted underseat muffler that hides within the rear fairing.

Underseat exhausts first started showing up on bikes in the 1970s, with the aim of allowing engineers to extend the exhaust pipe without having to curl it here and there. Engineers back then felt this was a good idea for the same reason Honda’s engineers do now; as the patent filings claim: “It is desirable that the tail pipe be formed as long as possible to increase flow velocity of exhaust air in the final stage.”

The trend hit its peak in the 90s and early 2000s, when underseat exhausts were thrown onto just about every sporty-looking machine, even those with no actual track-day intentions. There’s some debate as to whether the set-up actually helped in racing; arguably it delivered no discernible performance benefit. One assumes the real reason for the trend was that some people thought it looked cool.

It certainly didn’t feel cool, however. Underseat exhausts are notorious for roasting the derrières of riders and, in particular, passengers. I have no doubt that underseat exhausts have been the root cause of countless divorces over the years. Indeed, the only benefit of an underseat exhaust was that you could pick up a frozen burrito on your way home, throw it in a tail bag, and have it steaming hot upon arrival.

OK, maybe things weren’t that bad, but when the trend started to die out about a decade ago most folks weren’t sad to see its demise. Most, but not all it seems.

Honda’s proposed muffler thing hides all the emissions business in the rear cowl of the bike, in that awkward space that – at present – normally houses a half-hearted toolkit and just enough room for your wallet. Designed to work with a V4, hot air from the engine's rear bank runs a kind of gerbil’s maze in a bedpan-shaped muffler then exits from a single pipe. Meanwhile gases coming from the V4’s front bank is routed through a more traditional side exhaust.

It’s a convoluted system, to say the least, which makes me think (prepare yourself for speculation) that the target application for this fancy patent could be the fabled homologation special that Honda is said to be working on to celebrate the corporation’s 70th anniversary next year. You certainly wouldn’t put this much effort into an everyday commuter. The 70th anniversary bike is said to be following in the footsteps of the RC30 (aka VFR750R) and RC45 (aka RVF750R) – bikes that wowed the European market, in particular.

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