It started off innocently enough.
We've ridden countless turbo-equipped sportbikes, and marveled at their unbelievable acceleration and horsepower, coupled with personalities as docile as pussycats when not on the boost. But these were motorcycles fully prepped by the creators of said turbo kits, which meant any teething problems and installation hassles were taken care of long before we were allowed to throw a leg over the finished product. After all, nobody wants to put his worst foot forward.
The stock-bodied CBR900 turbo...
The stock-bodied CBR900 turbo project was looking a bit second-hand after the editor's little incident with the car.
So we pondered the inevitable question: How difficult would it be for Joe Average to install a turbo kit on his motorcycle? No special tools or diagnostic machinery allowed, just an adequate set of shop tools, a basic grasp of a motorcycle's components and their functions, and the mechanical aptitude to install/remove those parts with confidence. Would it be a nightmare to get things dialed in, with numerous hours spent burning the midnight oil? Or would everything slide into place, allowing us to hit the starter button and go?
And what is a turbo sportbike like to live with on a daily basis? Can it handle the humdrum of stop-and-go traffic without fouling the plugs or overheating? And how rideable would the bike really be?
The guinea pig for this experiment manifested itself in the form of a '98 Honda CBR900RR sitting in the lavishly appointed Sport Rider garage. One of the best sportbikes around, the CBR already boasts mid-10-second quarter-mile times, a 161 mph top speed, and 600-class agility, by virtue of its 111 horsepower motor pushing a 448 pound (including a full gas tank) package with a wheelbase of only 55.1 inches. Right. Just the bike you want to spike the powerband with some 60-odd extra horsepower.
These are the major components...
These are the major components of the Mr. Turbo kit. With the exception of the intake plenum, most of the installation was fairly easy and straightforward.
The stock Honda clutch couldn't...
The stock Honda clutch couldn't hold up to the added strain of 172 horsepower so we opted for a Barnett Kevlar clutch with heavy-duty springs.
The company gave us the option...
The company gave us the option of both 65- and 70-pound springs, but we ended up using a combination of the two.
Our next move entailed dialing up renowned turbo-meister Terry Kizer of Mr. Turbo in Houston, Texas, (281/442-7113; www.Mr.Turbo.com) for one of his bolt-on CBR900RR kits. Kizer has a long history with turbo-related horsepower, and numerous dragracing titles to his credit, as well as the current AMI Horsepower Shootout record. Retailing for $5395, the kit includes an Aerodyne turbo unit, a fabricated aluminum intake plenum complete with its own electronic fuel injection system, a high pressure fuel pump, and an exhaust [but no muffler; we bolted up a Micron (888/963-1212; www.micronexhaust.com) carbon fiber canister], air and oil filter setup, boost gauge, and all necessary mounting hardware.
After perusing the instructions, it became apparent that we'd need a few special tools. Two different sized hole saws are necessary (one for the boost gauge that is mounted in the left front fairing dash panel, and the other for the fuel injection return feed underneath the gas tank), and there are numerous electrical connections that require a soldering gun, some 18-gauge wire, and heat-shrink tubing.
Drilling for the fuel injection...
Drilling for the fuel injection return feed requires a hole saw and careful preparation of the gas tank to prevent it from exploding due to the sparks from the drill.
Getting the intake plenum...
Getting the intake plenum to slide over the cylinder head manifolds was a major hassle, since the fit was pretty tight and it was difficult to see if the hoses were mounted correctly. The hose clamps used for sealing were a pain to get to also.
The completed turbo installation...
The completed turbo installation is crammed in pretty tightly in front of the engine, but other than omitting the lower "inner chin" portion of the fairing, fits under the stock bodywork with no modifications.
The biggest hassle involved installing the intake plenum on the cylinder head. Since the silicone rubber hoses connecting the plenum to the intake port spigots have to hold 8 psi of boost without leaking, the fit is rather tight, and hose clamps are necessary to tighten things. It took us approximately two hours of pushing, shoving and cursing before we were able to get all four hoses correctly fitted and sealed.
There were some other niggling problems that cropped up, but they were easily handled. Making sure all the fuel lines and fittings were tightly sealed took a little time (since the 50 psi pressure from the fuel pump revealed any leaks instantly), and some careful maneuvering was necessary to tighten the EFI return feed elbow fitting inside the gas tank. There were some minor problems with the exhaust system mounting also, but everything else went together easily. And once everything was hooked up, dialing in the fuel injection took minimal adjustments to get the bike running smoothly.
A Micron slip-on mounts to...
A Micron slip-on mounts to the Mr. Turbo exhaust pipe. The Eurobikes rear fender had to be trimmed to clear the 190-section Avon/6.25-inch rim combination.
The Toby steering damper mounts...
The Toby steering damper mounts to the front fairing bracket, tucked away from any potential crash damage.
The stock CBR brakes are accented...
The stock CBR brakes are accented nicely by the RC Components Daytona spun-aluminum wheels. Avon's Azaro Sport tires handled traction duties superbly.
Kizer warned us about the hazards associated with turbocharging a light, short wheelbase motorcycle such as the CBR. "Even though we've got the boost regulated down to 8 psi to enable running on pump gas, you'd better be careful about how you twist the throttle on that thing, especially in the first few gears," advised Kizer, "otherwise you'll be wearing that Honda for a hat." And after taking our first few bursts through the gears on the turbo CBR, we couldn't agree more: The Mr. Turbo kit transformed our bike into a beast that doth not suffer fools lightly.
Dabbling in the boost (which begins to build at 4000 rpm, then quickly becomes ferocious by 6000 rpm) at full throttle for more than a nanosecond in the first two gears is a recipe for smacking yourself in the head with the windscreen, or looping over backwards. Even third gear requires judicious use of the throttle until at least 80 mph, since the boost builds quickly enough below that speed to spit an unwary rider on his head (as the editor found out by almost looping the CBR heading downhill).
Attack Performance's exquisitely...
Attack Performance's exquisitely machined aluminum rearset and shifter assemblies replaced the mangled stockers, while Factory Tuning Components' billet alternator cover spiffed up the engine cases.
And yet, like most of the turbos we've previously experienced, the Mr. Turbo-equipped CBR900RR is docile as a kitten when off the boost. Throttle response is good, the bike idles fine, and there is enough low-end torque available to squirt off traffic lights and such without ever having to place a call to the turbine room. Even the drudgery of stop-and-go city traffic was taken in stride by the Mr. Turbo CBR, with no hiccups or ornery manners in slow going.
Everything seemed to be going smoothly as we experimented with highway roll-on tests from third, fourth, and fifth gears at various speeds before the inevitable dragstrip sessions the following day. But when the editor found himself cranking off a 120-mph wheelie in fourth gear, he decided to quit and park the bike before a) he ended up in jail, or b) he would be tempted to try even faster wheelies. The editor did notice, however, that the telltale needle on the boost gauge was reading 13 psi, a bit over the 8 psi preset maximum. A phone call to Kizer ruled out the possibility of a boost gauge malfunction, prompting him to remark, "That must've been a wild ride; you were probably cranking out around 200-plus horsepower at that boost pressure." It's a testament to the CBR's bottom end integrity that it held up just fine at those power levels.
Unfortunately, when we began our warm-up for the dragstrip runs the next morning, we found there was something dreadfully wrong with the CBR. It was not making boost, and there was a nasty metallic rattling sound emanating from the turbo unit. The turbo was sent back to its manufacturer, where a teardown revealed that some of the turbo vanes had come apart. The cause, however, was the subject of some debate. The Aerodyne turbo is unique because it doesn't use a "wastegate" (a device that bleeds off excess pressure) to control boost levels. Instead, the Aerodyne unit uses an innovative "variable vane" setup that uses a diaphragm-actuated controller to change the turbo vane's angle--which affects how much exhaust energy is transferred to the turbo, thereby affecting how fast it spins--which in turn determines boost level.
All of the parties involved in this project (and many turbo experts we spoke to) were in agreement that an overboost condition occurred, but the actual cause of the malfunction--and whether it played a role in the turbo's failure--was never fully answered. Explanations ranged from a vane controller problem to a kinked pressure line to said controller. We spoke with many turbo owners who never encountered problems with this setup, and they were just as baffled at our dilemma. Whatever the reason, we received a new turbo unit, and it has since performed flawlessly.
We were ready to get back to the dragstrip for speed testing when yet another setback occurred, though this had nothing to do with the bike. An encounter with a wayward motorist sent both bike and editor skittering down the road, with brutal consequences for the CBR. Although there was no major chassis damage Tom Muckie (626/355-7058) checked and straightened the frame and fork tube for us. The bodywork took major hits also, and OEM replacement body parts are prohibitively expensive. However, rather than slapping some stock-appearing accessory bodywork on the Honda, we called up Eurobikes (703/257-9500; www.eurobikes.com) for some of its trick custom-styled fiberglass body parts, while Jim Tatone of Gerard Design (818/703-6589) laid on the liquid coats of paint. And since the CBR's front wheel sustained a nasty divot, we looked to RC Components (270/842-6000; www.rccomponents.com) for a set of its new Daytona spun aluminum wheels. Attack Performance (562/903-7757; www.attack-perf.com) donated a set of its beautifully-machined rearsets, Lockhart/Phillips (800/221-7291; www.lockhartphillipsusa.com) stepped in with a carbon front fender, turn signals, Toby steering damper and windscreen. The punctured alternator cover was replaced with a Factory Pro (415/721-4964; www.factorypro.com) machined piece, while Avon (800/624-7470; www.avontyres.com) provided a set of its latest Azaro Sport rubber. We decided to quickly abscond to the dragstrip before the accessory impulse spiraled completely out of control.
Launching a short, tall, light motorcycle such as the turbo CBR with TK horsepower (measured on the Bartel's Dynojet dyno) is a lesson in "throttle control or die" in the first two gears. Since we wanted to dragstrip the Honda in fully streetable form, we didn't lower the suspension or tie down the front fork; but considering how short the CBR's wheelbase is, it may not have mattered much. After struggling with keeping the front tire near the tarmac, we ended up with a best run of 10.18 seconds @ 147.91 mph. Note our high mph reading, indicating serious horsepower.
With this much power, the top speed runs were basically a joke, since we didn't have time to grab alternate gearing tall enough to keep the CBR from slamming into the rev-limiter at every opportunity. We'll try to get the gearing sorted and inform you of our final top speed in a future issue.
All in all, despite the interruptions that caused some delay in finishing the test, we were quite satisfied with the Mr. Turbo Honda CBR900RR kit. Although we'd recommend that anyone who doesn't have a good grasp of a motorcycle's componentry and a good mechanical aptitude send this kit and their motorcycle to a reputable shop to have it installed, the end result will still be a bike with unbelievable acceleration that retains all the driveability of the stocker. Given the amount of work necessary to modify the motorcycle, and the resulting horsepower increase, it's pretty tough to beat a turbo kit. And in this age of convenience and instant gratification, you can't ask for more (well, maybe just the common sense and riding skill to keep it under control.)
This feature originally appeared in the April 2000 issue of Sport Rider. Click here to see the April 2002 update.