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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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Patience gents, some big updates are coming any day now...

Alright, here's the deal -- I have a ton of updates to post, but no more image space left on my profile. Does a membership unlock more space? Anyway, the last pictures I was able upload are of the construction on my custom underbelly exhaust.

I plan on extending the lower fairings out, and I played around with a bunch of different exhaust designs before settling on a slash cut. I first made a mock-up out of cardboard, then tweaked the design in Autocad before finally taking the plunge into stainless. I cut all the bends on our bandsaw and machined an inlet piece for attaching to the stock header.

A friend of mine builds nostalgia funny cars for a living, so he has all the metal fab tools (shears, brakes, rollers) at his place, not to mention his son is a rather good TIG welder. So, I loaded up my supplies and headed over there for a long day (or two) of fab work. I used .049" stainless sheet for the body, stainless perforated sheet for the core (which we rolled into a 2.5" tube), and a 2.5" mandrel bend on the outlet.

The core was wrapped with long-strand stainless wool and was welded into place. Then, we popped the top on while simultaneously stuffing the box with Bristol Core muffler packing -- this step was not easy at all, but somehow we got everything in there.

We cut the stainless pieces so exact that we were able to fusion weld (no filler) almost every seam on the box itself. I also added an O2 bung on the pipe. The completed unit weighs less than 6 lbs and should outlast the bike.

Once I figure out how to upload more pics, I'll have lots more to share. Things get very interesting...
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I was cringing early on when you cut the boss off the block but you clearly are no cobbler. The throttle body adapter is beautiful. Does it attach to the throttle body with clamps like the OEM style? I originally thought that the inlet was aluminum but I now see that it's aluminum filled nylon. I hope that you don't have any header heat issues with it. It's fascinating what complex shapes can be made by laser sintering. The undercuts in the PAIR plates will tend to be a place for crud to accumulate. I'm suprised that you didn't put them on the underside. However IMO that's a perfect place for carbon/epoxy, which is lighter and won't need the undercuts. But I think that you may need special tools to do them by CNC because it's so abrasive.

The adapter is held on with silicone connectors and low-profile hose clamps. Obviously a direct bolting method & o-rings would be preferred, but I've had no issues with any boost leakage using this method in the past.

I baked the inlet in the oven for an hour at 300 degrees with no ill effects at all (it wasn't even soft). Once I can post up some more pictures, you'll see how I'm dealing with the heat from the header.

Also, the contour on the PAIR plates is mainly for appearance. Once anodized they are super easy to clean, and it's not like you see them anyway without lifting the tank. Also, I'm so done with carbon -- way too many bad experiences with vendors to go back down that route (especially for no real gain).
I apologize for the lack of updates lately; I've been going through some major changes in my personal life and could not find the time to post everything. However, I have time tonight, so I will bring you all up to date...

Here's the completed exhaust...

That's an O2 bung for the wideband datalogger. Not pictured here are the tabs that were later welded onto the top that mount the muffler in the same spot as the stock cat. The 4-way split inlet is a snug fit onto the header and, once clamped, everything seals up rather nicely. I played with the finish of the stainless and decided to leave it brushed for that no-nonsense works look.

Everything prepped and ready to bolt onto the bike. That's kevlar-lined thermal shielding and it reflects an extreme amount of heat. I actually had to buy a special pair of scissors just to cut the stuff.

Mounted on the bike. So far, so good...

Crank pulley mounted and belt installed.

Intake tubing in place, BOV mounted, and airbox firmly secured onto the throttle body. The Rotrex canister will go in the empty space on the right. The BOV vacuum reference is sourced from one of the big ISC lines on the front of the TB, since all the other ports are restricted and would not operate the BOV properly.

Here's how the inlet tube and filter is set up. The filter gets fresh, cool air directly from the ram air port, and the filter clears both the steering and the bodywork once mounted. Thermal barrier abounds everywhere, so despite the incoming air running directly behind the header, it should stay relatively cool across that short distance.

The radiator has been spaced out up top and the inlet hose has been spliced with an extension elbow to work around the supercharger.

Priming the Rotrex oiling system. There is a custom curved oil cooler mounted at the top of the radiator to help cool the traction fluid -- Rotrex superchargers do not like it when the fluid gets hotter than 180ºF, so the cooler ensures that does not happen. You can also make out how the exhaust fits on the bike with the O2 sensor mounted up.

The Rotrex oil canister mounted up. Thankfully there is plenty of room under the tank to clear these components.

Now, at this point you might be wondering if it all worked out...

...and that is a story for another day (when I can get some time to edit video)...
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Thanks guys. Since I only plan on running 9-10psi peak, I'm not worried about an intercooler. The time and expense that goes into designing an air-to-water system just wouldn't be worth it. If I feel I need extra protection, I'll add a water/meth-injection setup or run better gas. I don't do top speed runs, so this engine should handle my style of riding and 9-10psi just fine.
The stock header should be fine for all intents and purposes. I've left the SET valve in there, but have it fully open. Since the Rotrex doesn't provide tons of power down low, the smaller tubes of the stock header will certainly help keep a snappy feel with the higher velocity of the exhaust gases. Besides, the stocker is not too shabby when it comes to power. Take a look at this dyno chart -- the green line is a full Leo Vince system, and the red line is the stock header with slip-ons. There's only a 5hp difference up top. The purple line is with MR9 race gas, btw.

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As I've mentioned before, my plan for this bike was to tune the ECU directly, mainly thanks to the incredible amount of customization possible. I know there is open-source stuff out there, but Guhl Motors is only about 1.5hrs away from me, so I loaded the bike up and spent a day out in Lancaster...

We did about 20 pulls, tuning the air/fuel for each throttle position (and there are a lot of positions that the ECU reads from). Actually, the sheer number of maps present in the stock ECU is almost mind-boggling -- every condition you can think of is basically represented, and if you take the time, you can really have one killer running bike.

After everything was tuned, we decided to do a final power pull before taking it for a road test:

It produced 200whp @ only 10000rpm -- stock it made a max of 152whp. Keep in mind, too, that on Guhl's dyno, the S1000RR & 2011 ZX10R make 170whp. The sound of the thing was absolutely unreal, and it shot one and a half foot flames out the tailpipe due to eliminating the stock fuel cutoff at the rev limiter. We were having some issues with the power starting to flatline above 10.5k, and that final run there actually tapered off up top, at which point I thought that we might be leaking some boost...

Now comes the part of the story that usually never gets told in builds like this, and will hopefully teach you all a valuable lesson about assumptions. More specifically, just don't make them!

Here is how the bike looks now:

If you look very carefully at the last few seconds of the video in the bottom right corner of the screen, you'll see the coolant overflow purge. I wasn't sure at first what was going on, but after another quick pull with power now really dropping, we deduced that the head gasket must have given way. A compression test sealed its fate -- the first two cylinders were noticeably down compared to the others. So, after all the work I had done, the engine had to come out.

Before I yanked it out, though, I took it for a spin back at the shop. You could not tell it was down on power at all, as it was silky smooth and absolutely impossible to give any more than 40% throttle in first gear (with stock gearing, no less). The datalogger told the true story though -- the engine was seeing between 15-17psi at redline! On pump gas!

Now, I have designed quite a few supercharger systems over the years for all kinds of engines, and I can usually predict the final boost within a psi or two, but this bike completely threw me for a loop. It apparently just runs out of steam up top, causing the Rotrex to pack serious amounts of air into the cylinders. On pump gas, this is not a good thing.

3 mistakes ultimately led to this failure -- 1) no boost gauge as I thought I knew the boost curve ahead of time, 2) datalogger was not recording while tuning since we used my O2 sensor, and 3) I was not personally handling the tuning on the road where I would have caught the insane boost levels before anything bad would have occurred.

Here's where the gasket failed:

The cylinders looked pretty good, but there's some discoloration and aluminum buildup at the top of the bore, meaning the pistons are shot. There's almost no sign of detonation, but the intense heat led to scuffing.

Lots of work to be done.

Stay tuned for the (hopefully) grand conclusion to this build...
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Your headgasket is a sign of detonation, i would check your big end bearings too
Lucky the runs were short enough not to damage the cyls
Your belt drive is obviously a very sound system to make that much psi without too much belt slip, a guy i know built a supercharger kit and could only get about 12 psi, so he changed to toothed belt and got 19, ... same result as you at that point ...

Going to make any changes while its apart ??
Yep, there was detonation (and I'm sure that's why the power was flatlining up top instead of climbing to redline), but it was really quite minor for that amount of boost. You can barely see some tiny pitting on one side of the piston crown, but that's it. Checked the bearings, they're absolutely beautiful.

Definitely no belt slip with a synchronous belt. The amount of boost is surprising as I had logged the boost up to 7k rpm before taking it to Guhl, and it matched the 10R perfectly (I couldn't rev it any higher as it was going way too lean). With this same pulley setup, the 10R made 9psi peak -- again, you just can't make assumptions, even if you think you know something really really well...

Sounded like it went bad at 36 seconds, just before he chopped the throttle or was that rev limiting?. Bad luck. I am sure it will be right second time around.
That's just the limiter. When you leave the fuel on until the ignition cut, it can almost sound like a gunshot at times. I don't have the chart, but it started losing some power at the very top of 2nd gear on that pull. The pull we did after that just started nosing over after 11k rpm.

When this goes back together, it will have a new stock MLS head gasket, pistons, and rings. The engine doesn't even have 3000 miles on it yet, so it's still very fresh. I am going to get the pistons coated at Swain Tech, though. This thing should handle 9-10 peak psi all day long as it is, so as long as the boost stays in that range, it should be smooth sailing.
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Did you put rods in it? With that kind of power stock one's probably won't last long.
I'm not worried about rods at all. Believe it or not, there's actually less stress present in the rotational assembly under low to moderate levels of boost than there is naturally aspirated, thanks to increased cylinder filling and the combustion process taking place over greater range of crankshaft rotation (the additional compression force counteracts the inherent inertial tension force of the piston accelerating down in the bore).

One of the first things you notice when you supercharge one of these bikes is that the whole engine gets smoother, almost like an electric motor, and it's not just a feeling -- it actually does smooth out for the reason I just said. For a 50% power increase, there's still far greater stress due to rpms than there is due to additional power, so as long as you keep the redline the same, the stock rods are fine. Now, if you add enough boost, then the compression forces override the tension forces, and you end up with pretzel shaped rods.
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Are you the guy that does the vfr800 supercharger kit? I'm guessing so from your avatar?
That would be me. I've had one guy net 200whp on a 6th-gen with stock internals and pump gas. That's a 100% gain from 11psi. Not a single failure, either -- those engines are bomb proof.

What fuel and ecu mods have you done , all tps mapping with the flash or is there some pressure based influence too ??
What a/f were you targetting,
Good question Maj750, I was wondering the same thing when it was explained it went lean up top but forgot to ask. I have seen on the turbo websites where they offer a 3 bar pressure sensor. Think it was a GM one.

toro are you going to reduce the drive to the compressor?
Fuel system is bone stock. Earlier in the thread I talk about testing the pump and finding out that it can support plenty of power; bump up the voltage and it can handle nearly 400hp, too. Once the injectors are set at a 50/50 split, they deliver tons of fuel -- more than enough for this power level.

The ECU tuning was all done at Guhl using their proprietary software. I'm not basing the tune off of manifold pressure as it's not a transient response with a supercharger and stays constant for a certain RPM & TP (unless, of course, you encounter major elevation changes). Every bike I've done up to this point has used nothing other than a Power Commander, and they've run perfectly. Ease of tuning is one major advantage a supercharger has over a turbo. We did talk about possibly adding in a 3-bar at a later date to handle slight boost variances, but it's not necessary for a spot on tune.

The bike did not go lean up top. It actually had no trouble nearly dipping down into the 9s on the AFR, but that is way, way too rich. I like to start with a 13:1 ratio and taper down to mid 11s up top. In this case, failure only occurred because I was running pump gas with nearly 17psi!

I am not going to change the pulley setup as the entire system was designed around those pulleys. Since this bike has such a high redline, if you underdrive the Rotrex too much, the rest of the powerband will suffer. I've already tested & figured out a solution -- an inlet restrictor. The restrictor creates a pressure drop at the front of the inlet (which alters the PR), and gradually tapers the boost off to a certain level. In this case, I ran some calculations and figured out what size hole was needed to bring the boost down to 9-10psi at redline. It works awesome. You still have great boost response down low and in the midrange, but instead of constantly climbing, it gently noses over up top. Even with the bum pistons and gasket, it was amazingly fast when I tested it.
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I bet it was amazingly fast :)
I have talked to the local guy with Rotrex about "boost control" aiming at the same thing you are. to overgear and externally control pressure improving the mid range and limiting top end, we were discussing using either a BOV with pressure porting below the diaphram (instead of the usual Vac on top ) or a turbo wastegate on the inlet and a E Boost or similar to pwm a solenoid and have total control over pressures either gear based or manually triggered ,
At 10 psi your probably going to have the same problem turbo guys do when they put too high a wastegate spring in and have a bike you cannot utilise fully in the lower gears
Your A/F plan sounds similar to mine, except i start mid 12's as i have gapped my plugs down and runs less smooth if too lean
Knew lots of supercharger installs used only TPS /rpm mapping , makes it much easier than turbo
I think the ultimate solution for boost control on a supercharged application would be a servo operated butterly valve placed before the inlet of the supercharger (I bet you could even use the stock SET servo to control it). Restricting the inlet is a much nicer solution than venting the pressure afterwards as you do not waste any power in compressing air & then just dumping it to atmosphere. I eventually plan on making a another map (you can remap the A-B-C mode to whatever you want) that utilizes the secondary throttle plates and modified ignition timing on a per gear basis so that I can go WOT and keep the front end just barely hovering off the ground.

BTW, I don't mind if things get a bit crazy in the first few gears -- it makes riding around town a blast. My VFR was too insane with the gearing I originally had on it, though; it would power wheelie in 5th gear, so I had to change it to something more manageable.

So how is the stock IAP running with your setup?
No problems. The nipples on the throttle body are restricted, so the boost does not affect the MAP like it does on other bikes where I have to use a separate restrictor and one-way valve to vent pressure. The thing starts up and idles like a stocker and throws no error codes.
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A few control questions since I didn't study the thread in detail.

- How is boost control done?
- Are there any means to reduce IAT, meth injection or IC?
- How is fuel demand vs. boost controlled?

I took a quick glance through the thread and got the impression the engine went south due to over boost and no boost gauge was available. I have to say this sounds utterly silly but thanks for being open and honest to help others avoid this.
Boost is set by the pulley ratio, but I am now using a restrictor plate to limit the amount of air that enters the engine. Also, to the earlier poster, using a restictor plate lessens the load on the Rotrex -- think of a shop-vac: when you place your hand over the top and cover the fan, what happens? It spins faster due to the fact that there is less air present that it has to move and/or compress. This is the same situation. Any additional heat introduced into the system is far less than the heat generated in the combustion chamber by compressing 17psi worth of air.

If need be, I'll run a water/meth setup, but I do not do sustained top speed runs and only planned on running 9psi, which should not be an issue with the Rotrex and pump gas. The new pistons have been ceramic coated, though. The tuning is handled solely by modding the fuel and ignition tables in the ECU. The boost response is not transient like a turbo, so once you have a tune ironed out, nothing changes.

Finally, I logged the boost a little past the halfway mark before I took the bike out for tuning, and the boost curve was exactly in line with what I was expecting and what I have witnessed on other bikes. I ASSumed that the curve would continue on in a fairly linear fashion (like the other systems I've developed) and did not monitor it during tuning, but for some reason this engine is different and the boost skyrocketed. Oh well, it was a costly mistake, but at least it happened to my bike and not someone else's. I can say with certainty, though, that the stock GSXR engine can handle upwards of 17psi on stock internals and pump gas (for a very brief period of time!).
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I hope you guys are ready for pictures, because I have a lot of them coming up right now...

I sent the brand new OEM pistons out to SwainTech for coating. They ceramic coated the tops and put an anti-friction coating on the skirts. Since the old pistons scuffed in the bore, I figure reducing the heat they see and making sure the skirts don't stick in the case of a lubrication breakdown is a good thing. I also kept the compression ratio stock.

I was able to swap the pistons without removing the crank, but every other part of the engine had to be disassembled. I bought a torque angle gauge to tighten the fasteners to factory spec.

The engine finally all bolted up. I figured that as long as I had it out of the bike, I might as well wrap the tops of the header tubes to reduce the heat even more. Also, that engine you see in the background is going to be a killer -- 375ci small block Chevy, SB2.2 heads (NASCAR stuff), dry sump, all roller drivetrain, all forged internals, 9000+ rpm redline, supercharged and fuel injected. Should be a fun little street car if I ever get it done.

Engine getting bolted back into the bike. This was a 2 person job.

Another shot of the airbox...

Ready for her maiden trip around the parking lot. This thing was a smoke machine on startup. Smoke was everywhere; out the pipe, under the tank, it looked the bike was on fire.

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I let it warm up, then took it out for the first spin. I altered the engine rpms the whole time and made sure to keep the new rings loaded. Within a mile or two the smoke was gone. 20 miles later I brought it back to the shop and changed the oil.

I did a bunch of custom, cost-effective mods while I had it apart. I found another swingarm on ebay, stripped it, polished it, brushed it just right, then cleared with some epoxy paint. I threw on a 520 sprocket set (stock ratio), RK chain, Galfer wave rotor, HEL brake lines, and swapped the wheels to freshly powdercoated RC51 5 spokers.

It was not easy making the wheels work, and the swap required new bearings, seals, spacers, and some machining to the wheels themselves. The front calipers are R1 units with custom spacers, grabbing 1000RR rotors. I love those calipers, and just might have to swap the master cylinder for the stock Brembo unit (I have that setup on my VFR and the feel is better than this current setup).

The exhaust sounds awesome on the open road. Really deep while cruising, aggressive while revving up, and the smoothest, sweetest, most insane sound near redline. Can't even describe it.

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I still have to get the fairings done (I'm modifying them, too), but promise to post pics once they're back on the bike.
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Almost forgot the best it rides...

A W E S O M E - O

That about sums it up. Way, way, way more controllable than the 10R. If you want to feel like you're riding a bucking bronco, find a 10R, add boost, and try to hold on. Impossible to go WOT in the first 3 gears or you point skyward. Absolute blast around town (probably the most fun bike I've ever ridden), but hard to go fast. This thing is not like that at all, even with the stock wheelbase and ride height. First gear will point the nose as high as you want, at any time, simply by how far you twist your wrist. It's like direct wheelie control. However, once you're out of first, you can keep the front end hovering just inches off the ground while still accelerating at an alarming rate. That shift into second under boost, too, is amazing. It's like someone kicks the bike in the rear with a giant steel-toed boot. The only other bike I've ridden that has that kind of instant kick is a worked M109R, and that thing is shaft drive.

Smooth, smooth, smooth. Liquid, electric smooth under boost. You can pretty much shift into 6th-gear and leave it there -- it'll pull from 2500 without issue, and accelerates really hard from 4500 on up. I'm almost tempted to add a tooth up front the pull is so good. To top it all off, I haven't even touched the tuning from the day of destruction at Guhl. We dialed it in pretty well that day, and there are no hiccups anywhere in the powerband. There's just a slight whistle to let you know the Rotrex is there, and you don't even hear the BOV like you do on some other bikes. Overall the thing rides, behaves, idles, and performs like a stocker (better than a stocker, actually) when you want it to, but is just begging to be opened up at every opportunity you get. Also, the gas mileage is identical if you stay out of the boost.

I will try to get some ride footage some day, but until then, I'm going to be out riding, finally getting to enjoy this thing.
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DAN....YOU ARE A GENIOUS(did I spell that right??? lol) in other words...YOU ARE THE FUGGING MAN!!!! Awesome detail,frome the wheels to the calipers to the swingarm and everthing in between...i'm speechless...this how I'm looking right about now:biggrin:biggrin:biggrin
Many thanks, dude. It all came together nice. Just wait until I finish the bodywork...

Love it! what a great job! That machine looks awesome. Great write up!!!!

Just a question. I see that you have the SET valve still in the exhaust. Any reason for that?
The valve is disabled and thus permanently open. There's not enough of a power gain to warrant ripping it out, so I left it there.

This is such an awesome bike project. Look like you know your shit about putting to gether a supercharged bike and also creating your custom parts. Everything looks amazing except I'm not sure why you polished the swing arm? It just doesnt seem to go with the flow or theme of the bike, do you have any other plans on polishing? Keep up the good work.
The swingarm has a brushed finish - it's a little hard to see in the photos, but it is not shiny. I had to sand & polish it to get all the casting grain out, but after it was smooth, I was able to finish it the way I wanted. I was going for that Aprilia/superbike look of the fabricated swingarms.
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