The Kneeslider

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Supercharged Honda VFR800

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VFR800 with Rotrex supercharger

VFR800 before the crashThink of the number of great motorcycle projects starting with accident repairs. You know how it goes, the bodywork comes off, a few pieces are removed and then you think, “well, as long as I’m doing this, why not modify that …?” This VFR800 with forced induction is a case in point.

The owner originally bought the Honda as a theft recovery and did a nice job fixing it up. Unfortunately, while on a short ride, he had a moment of inattention and the bike went down, undoing a lot of his hard work. Off comes the bodywork and he starts thinking, maybe it would look better as a naked bike and maybe a custom exhaust and why not add a blower? Why not, indeed.

Honda VFRs are really nice bikes but there isn’t a lot of room for a supercharger and you’re pretty much on your own coming up with mounting brackets, intake manifolds and all of the associated plumbing and wiring. What would the world be like without CAD and CNC? It would be like it used to be, naturally, but these days those problems can be figured out on a computer screen and machined exactly like you want them which helps a lot of builders pull off projects like this.

This particular build is covered in great detail over on the VFR forum with loads of step by step photos. It gives you an idea of what goes into a project like this, in case you were thinking about attempting a build of your own.

The final photos here are minus the lights which have since been installed but I think he did a really neat job, the blower fits in there very well. Power comes up to 140 horsepower with 63 foot pounds of torque, not to mention those 3rd and 4th gear power wheelies. Nice bike!

The VFR discussion forum looks like the place to be if you have one of these bikes, check ’em out.

I was pointed over to this VFR by Andy, who has not only been sending in some great tips but also has a really nice project of his own going on. When he’s a little further along, we’ll give everyone a look. Thanks, Andy!

UPDATE: Dan, the builder of this VFR, has posted final finished photos on the VFR forum with the bodywork back on plus he’s discussing progress on upcoming kit versions of this blower setup. Cool!

More photos and link below:

VFR fabricated blower intake manifold

VFR800 with Rotrex supercharger

Link: VFR Discussion forum
All photos: VFR discussion forum

Comments

  1. Thanks Kneeslider for the coverage. This has been an Epic thread on our site. Dan, the owner/builder of the “Torocharger” bike has done a superb job fabricating all the necessary parts and putting it all together.

    There is a lot of aftermarket support for full-on sportbikes and if you want more performance, there are bolt-on turbo kits and the like for Gixxers, Busas and the like, but if you live for the song of a V-4 like the VFR, you’re pretty much out in the wild by yourself.

    Rob McKinnon
    Moderator
    Vfrdiscussion.com

  4. I’m having a hard time figuring out where the turbo is. Everything looks so stock, I’m really impressed.

  5. Sean, it is supercharged, not turbocharged .
    The supercharger looks to be mounted above the front cylinder head.

    A little old school fab work always gets my respect!

  6. The quality of work is amazing! Owners of 5th and 6th generation VFR’s are hoping that he’ll be able to productize his work.

    It’s a cult thing…

  9. Maybe someone can explain to me why turbochargers have been more commonly adopted on cars & bikes instead of superchargers. I have always thought that superchargers represented a more elegant solution… no lag, better powerband (for street), simple parts, no excess heat,… Sure the supercharger consumes some engine power, but this is much more than compensated for by the power gains it creates. Any insights or theories why superchargers have been so scarce?

  11. That bike is great and the reverse cone exhaust is way cool. Plus it’s built on the best VFR ever, the late, great model with gear driven cams.

  12. One advantage of a turbo is it can be designed to have low or close to no boost at low rpm’s, helping keep gas mileage high. At high rpm when more power comes on, the turbo spools up and creates boost and the power we want.

    A manufacturer can somewhat under size a motor for peak power, and then add a turbo to get back to the wanted power level and get higher mileage with lighter weight than a larger normally aspirated motor.

    Superchargers “tend to” get lower mileage as the boost “comes on” at lower rpm’s. Boost at low rpm’s essentially wastes fuel as higher power levels aren’t usually needed there. This however as you said makes for a more drivable car, and can make certain superchargers more favorable for drag racing.

    Please note I am REALLY generalizing here, and it’s all about the design goal is, but this is how it’s usually implemented.

    And that is a really slick install, it looks factory the way it’s tucked right in!

  13. D’oh! I saw the modified exhaust and the drive chain and immediately thought “turbo”, instead of reading what’s in front of me! I could see where the super was, but the way it was installed made it look like it was just another factory gewgaw.

  14. What type of Super Charger is being used? Is it centrifugal or PD? (looking at the manifold I would say Centrifugal) I did a couple of GSXR’s back in the early 90’s with Sims and Rohm kits using a KF Engineering (Roots Type PD) blower, and while they made tremendous HP and torque, they were difficult to ride as the under seat heat generated by the blower was not conducive to long rides on hot days, nor was the nearly 100 ft-lbs of torque at 6000 rpm from the 1100.

  16. tubos hurt low RPM fuel efficiency. The turbo vanes are an exhaust restriction and there is actually some mechanical loss due to pumping restrictions as well.

    From what I remember of older superchargers is that sealing of the internal vanes was an issue. Often an oiler was implimented to help the seals live a long, healthy life. Oil in the intake charge reduces combustion efficiency and increases pollution. With today’s modern seal materials this may no longer be much of an issue.

    I think the choice with auto manufacturers to go with a turbo is more of a marketing ploy. Turbos are more “high tech”, jet turbines and all, and super chargers were pure gear-head braun; not sophisticated. Mercedes recent choice of supercharger in some of its cars has had a positive benefit to their rather stodgy brand image.

    Turbos can be more easily addapted to existing engine design since there is no requirement for external drive trains.

    Both can be made to work well with the same results.

    -todd

  18. That’s beautiful. I’ve got a 6th gen VFR, and I was thinking how nice it would look cleaned up as a streetfighter, but that blown one is impressive.

  19. “turbos hurt low RPM fuel efficiency. The turbo vanes are an exhaust restriction and there is actually some mechanical loss due to pumping restrictions as well.

    Turbos can be more easily adapted to existing engine design since there is no requirement for external drive trains.

    Both can be made to work well with the same results.”

    Very good points Todd! The first one is a good reminder is that a turbo isn’t gaining something for nothing! The exhaust isn’t free, as too much back pressure reduces horsepower when you aren’t making boost.

  21. Superchargers are actually less efficient than turbos. They represent an omnipresent drag on the engine as any other crank driven accessory does, and that drag increases exponetially as the rpms go up. Although the power benefits greatly offset the parasitic losses, they are less efficient than an appropriately sized turbo.

    Pumping losses are negligeable on a turbocharged engine versus the drag of a supercharger. And the restriction at lower rpms actually helps low end torque, right where you need it when the turbo hasn’t spooled yet (while not providing a torque increase as instantaneous as a supercharger would).

    I’ll take whatever’s available for my VFR (namely this kit which to my knowledge is the only one of its kind for the moment), but if I had a choice, I’d go for a turbo kit rather than a supercharger. A bike’s engine is meant to be reved at high rpms and in terms of exhausts flow, that’s were turbos feel right at home. Don’t need the drag when you’re coasting.