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My supercharged K8 project...

131766 Views 192 Replies 85 Participants Last post by  D.Man

The bike pictured above is my bone stock K8. A friend gave me a fantastic deal on this bike last year, and it has just under 2000 miles on the clock. I love this bike for the same reasons everyone does -- incredibly smooth, extremely capable and controllable, great power, and fantastic ergonomics for a supersport machine. The local Dynojet 250i says it puts down 152whp (SAE corrected), which is actually more power than a full-exhaust, PCIII-tuned '04 ZX-10R produced on the same dyno.

Now, normally the next step would be to add an exhaust, change the gearing around, or add some braided lines, and while I'll eventually get to those mods, I have something different in mind right now...

It's a Rotrex C15-60 supercharger, right off the plane from Denmark. This little unit can support over 230whp, and that's the number I'll be shooting for with my little project here. Also, the impeller wheel used to be cast, but these new wheels are apparently machined out of billet.

Before you ask, yes, I am a power junkie. There's just no going back once you've ridden a boosted literbike...

You can see how small it actually is compared to the bike. Somehow, some way, it will fit in there...

After staring at this sight for a couple of days, I realized the only place to put this thing is in-between the engine and the radiator, just below the frame. I'd love to stick it up higher, but the frame would get in the way of the belt (which is a dealbreaker) and the radiator fan would also have to be relocated. Placing it lower eliminates these problems, but makes it much harder to hide the drive behind the fairings and also places the inlet of the Rotrex very close to the header. I also do not want cornering clearance to be compromised at all, so it will be in as far (and up as high) as possible.

If anyone is wondering how I plan on driving this thing, take a look at the picture above. The M10 bolt currently fastened into the end of the crank will be removed and a machined adapter will take its place (this adapter has to locate perfectly off the crankshaft for this to work). A pulley will sit on top of this adapter and then drive the supercharger via an 8mm synchronous belt. The supercharger bracket will either take the place of the stock cast cover or locate off of it -- I'm not exactly sure yet which way to go.

There's a lot of work left to be done, but I'm looking forward to it. I plan on tuning the ECU directly and, of course, it will run on pump gas. In the meantime, wish me luck, and stay tuned...
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Yummy so Sweet :) I'm lusting for an AA performance kit :)
They are making kits for Gixxer k1 from 2000 on , I'm so down :) throw in a spacer and hang on 200 mph bike:)
Man that's gunna be a tight fit...cant wait to see more. I'm sure you've already hunted around and seen the other s/c GSXR's....they make some awesome power from some silly low boost numbers...
Man that's gunna be a tight fit...
Yeah it is. I don't think there's going to be any way to keep everything completely concealed behind the bodywork. Fitting the inlet tubing and filter is also going to be a major pain, but I think I have an idea on how to do it.
i just got hard. cant wait to watch this build
Subscribed, so nice to read a well thought out post; grammar, spelling, punctuation.

But still, this is a badass build!! :punk
Im sure you've probably seen this but TTS in the UK do a S/C kit for GSXR1000's as well..this PDF may or may not be of any interest!
Subscribed, so nice to read a well thought out post; grammar, spelling, punctuation.

But still, this is a badass build!! :punk
Thanks. No matter what it is that I do, I try to do it the right way.

I have some big plans for this bike...

Im sure you've probably seen this but TTS in the UK do a S/C kit for GSXR1000's as well..this PDF may or may not be of any interest!
Yep, I've seen it. I'll be doing things a bit differently than TTS, though.
I will be watching this thread closely as well.:burnout
Mock-up time.

I had just finished making a set of custom pulleys for a guy (who owns a K5, coincidentally), so naturally I wanted to see how they'd look on my bike beforehand. I grabbed an old generic bracket that was laying around and proceeded to bolt it to the frame and the Rotrex; naturally the offset is all wrong, but at least I can grab some measurements off of it.

Clearly there are interference issues with the blower mounted in this position (primarily the inlet contacting the header tube and the compressor housing touching the engine case bosses), but as I said before, there's no other place to stick this thing. Now, if I was able to mount the blower closer to the engine, I could stick it further in and have more room for the inlet at the same time, but the bosses prevent that from happening.

You can actually see where the inlet was rubbing on the header -- that's no good. The only option here is for a little surgery.

Using a sawzall, a file, some sandpaper, and a little elbow grease, those bosses are now history. Much more room to play around now.
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So whats the update? Is it boosting yet? Huh? Is it? Is it?
No, not boosting yet. There's still a ton of work to be done.

Removed the stock airbox from the TB...

All that clutter associated with the PAIR valve will have to go.

Much better. I pulled the reed valves out so that the block-off plates I'll be making will seal up flat against the rubber gasket of the base plate. I also took this opportunity to swap out the stock plugs for some colder NGKs. Eventually that black plastic panel attached to the front of the head will have to get yanked, too, to allow clearance for the intake tubing.

Now that all the crucial dimensions of the starter cover have been digitized, the next step will be to make a better mock-up bracket for the supercharger and see how everything fits.
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Since I know the output of the stock pump cannot support 250-260 crank hp, some upgrading will need to be done. I yanked the stock assembly to see if it's possible to shoehorn in a Walbro, but there's just absolutely no way.

The new style Mitsubishi pump is just about half the size of a regular pump, and without a completely new housing design (including a built-in filter), an in-tank Walbro is out of the question. The K6 and older bikes would not have this problem as they use the larger style pumps.

I do not want to go to an external pump, though, so for the moment I'm kinda stumped. I do have one idea that I'm going to try out, but it's going to take some careful experimentation; if it works, it will be a very elegant solution to this problem.
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good luck buddy and loving the pics and detail
Here in dominican rep. for some reason of the universe the K7 pumps have failed miserabily and my mechanic uses the K5 ones, since they are easy to find car pumps that fit. I think that mitsubishi lancer evo is the same or hondas.

If I where you I would use a external pump with a external presure regulator.

There is no other pump that fits like the K7 one.... they are small maybe that is the reason they are failing like that.
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