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Turbo "Busa" Kart

10/13/08- Once I mounted the new engine into the 'Busa frame, and put on the exhaust manifold, turbo, throttles, and intake manifold, I was now ready to begin the difficult process of joining the 'Busa end to the chassis. I first brought the two units into position to get an idea of where they would sit in relation to one another. The front of the Busa frame fits in between the roll bars, and the turbo tucks down at the base of the roll bar. The goal was to bring the 'Busa end as far forward as possible and also as low as possible. I had to reposition the compressor housing so the discharge was facing upward to make it fit.

After visualizing how they will go together, I created a support frame utilizing 1/4" thick plate and chrome moly tubing, and joining them together with the chassis spars from the original Beetle frame.

I will be supporting the Hayabusa end three ways. The first is to use the roll bars as a sort of triple tree. I will fabricate two brackets and weld them between the roll bars, and the 'Busa frame will slide between the brackets and get pinned. I fabricated a pin out of aluminum stock that will hold the front mount together. The second support will be to utilize the chassis spars to support the engine and frame from underneath.

The third and final way will be to make a subframe of chromemoly tubing from the rollover structure to pick up the rear of the 'Busa frame. Since the 'Busa frame is aluminum and I will be supporting it with chromemoly tubing, I had to fabricate two sideframes from steel plate, which get bolted on to the rear of the frame. Now I can weld my chrome moly tubing to these sideframes. All of these supports will be bolted to the chassis so that they can be removed. Since the engine can only come out of the bottom, I will need to be able to take the chassis apart to get the engine out in case it needs to be replaced.

I expect to finish the joining of the chassis together in the next couple of weeks. Once I have accomplished this, I will have finished the most challenging part of this project, and then I can get to the fun stuff, like wiring and plumbing.

9/26/08- I finally received the engine from Downs Engineering, and what an impressive lump it is! Better late than never, and worth the wait. The block is basically the same although the internals have undergone extensive modification. However the thing that helps the engine make all that power is that massive turbo. I've seen smaller turbos on a Mack Truck. This turbo will push around 21 psi of boost through a massive air to air intercooler to produce 428 horsepower at the crank.

Now that I have the new engine, I can mount it into the 'Busa frame and then begin the complicated process of joining the motorcycle rear end to the front end of the vehicle. I will get started on this immediately. It's a good thing I decided to wait for the new engine to come in before doing this, as the turbo sticks out much further than it does on the other engine. Watch this space! Next Entry

6/15/08- According to the engine builder, the engine should be here by the end of this month. In the meantime, I am working on designing the wiring of the vehicle, and I also designed and built the instrument panels. As shown in the picture below, there are two instrument panels. The first panel contains most of the engine and vehicle function gauges, including oil pressure, oil temperature, water temperature, fuel level, and battery volts. It also contains the ignition key, the starter button (sourced from a Honda S2000), and switches for headlights and hazards. The switch under the red cover is to engage the reverse motor, which will be electric. The big red knob adjusts the brake bias at the pedal assembly, while the red handle is the rear brake proportioning valve. The second key switch on the right will be to switch between pump fuel and race fuel programs on the engine.

The second panel is the dash panel, containing the tachometer, speedometer, and boost gauge. Also, there will also be a blue neutral light, and a red low oil pressure warning light. On the left side of the panel will be a basic turn signal switch and pilot light. Eventually I will finish the instrument panels with a carbon fiber trim to match the seats and the interior trim of the car. Next Entry

5/04/08- Since I am still waiting for the new engine, I decided to continue making the controls for the vehicle. On the last update I finished the steering control. The remaining controls are for the brake, accelerator, clutch, and gearshift.

The Hayabusa engine, like most sport bike engines, has an integral transmission. The 'Busa's 6-speed transmission is shifted sequentially. On the motorcycle, the rider pushes the left pedal either up or down to change gear. I designed the gear shift linkage as a rod linkage which would move the Hayabusa shift lever in order to shift gears.

Since my chassis already had a rod shift linkage in the central tunnel, I decided to work off of that rod. I fabricated a shaft which connected to a heim joint as shown in the pictures below. As the shift rod moves back and forth, it moves the heim joint in an out. The heim joint moves a reversing bellcrank that I fabricated from steel rod and plate, supported by two larger heim joints. The bellcrank serves three purposes. First, it offsets the shift linkage so it lines up with the shift lever on the 'Busa engine. Secondly, it reverses the movement of the shift lever so it works in the direction I want it to. Finally, because the bellcranks are of different lengths, it increases the range of motion on the shift lever, so a small movement of the shift handle will result in a large movement at the bellcrank.

On the cockpit end of the shift rod, I also had a lot of fabrication to do. The trickiest part was making the shift lever and fulcrum. The fulcrum started as a piece of 7/8" thick steel plate. With an oxyacetylene torch I cut it into a basic shape of what I needed, and then ground it smooth. Next, using a die grinder, I hand shaped the bottom end into a ball which would fit smoothly into the socket of the VW shift rod. Then I drilled a hole for the fulcrum pivot point, and drilled another hole in the top to fit and weld in the 1/2" steel rod which would become the shift lever. Next, I fabricated a base for the shift lever and bolted it to the chassis.

Next, using a bench vise, a little heat, and a long piece of pipe, I bent the shift rod into the shape that I wanted. The goal was to get the shift knob right next to the steering wheel so I would never have to take my hand too far away from the wheel to shift. I topped it off with a nice MOMO shift knob, and finished off the bottom with a leather shift boot. It should all look really nice when I put the finishes on the car.

The shifter seems like it should work like a charm. Just pull back for an upshift, push forward for a downshift, just like an Indy Car.

Then, it was on to the pedals. I finally received the master cylinders for the car. The car will have a total of three master cylinders. The first, largest one, will be used to operate the front brakes, actuated by the balance bar on the brake pedal assembly. The smaller cylinder will be used to operate the rear brake, also driven off of the balance bar on the brake pedal. Finally, a third cylinder, as small as the rear brake cylinder, will be used to operate the hydraulic clutch. Once I mounted all three cylinders to the pedal assembly, I was then able to mount the pedals in the car. I had to cut away a small part of the VW frame to get the pedal assembly to fit where I needed it to be for maximum comfort. I realized I would have to raise the pedals off the floor somewhat, so I constructed a floor plate to raise the pedals and the driver's feet off the floor about 1.5". Then I drilled holes in the plate and mounted the pedal assembly. Finally, I mounted the whole assembly to the floor of the car. That gave me brakes and clutch. All that was left was the throttle pedal. I spent a great deal of time to locate the throttle pedal so it would be in the perfect spot for heel and toe downshifts. Then, I welded two brackets to the cowl bar and hung the pedal, which is the same pedal that came with the Tilton pedal assembly. I left it so I can adjust the position of the accelerator pedal from side to side to accomodate a wider foot. Later on I will connect a throttle cable to the top of the pedal and run it back to the engine.

With that, I have completed the primary controls for the vehicle. I have started ordering the gauges, switches, and instrumentation, and have begun to think about the wiring of the vehicle while I wait for the new, more powerful engine to arrive. Next Entry

4/09/08- Progress continues on the Turbo 'Busa Kart. While we continue to wait for the new motor to come in, we shifted our focus on the steering system. Since I was utilizing the front suspension from a Chevrolet Corvette, I also used the Chevy rack and pinion steering system. Attached to the steering gearbox via a rag joint and a universal joint is the aluminum Chevy intermediate steering shaft. I had to work out the steering system from the intermediate shaft up. Basically, I needed a steering column.

I turned to Speedway Motors and quickly found the Sweet Manufacturing collapsible steering column. This column was just what I needed, but I had to make some modifications to it to get it to work.

I started by modifying the splined end of the steering column to accept the coupling on the intermediate shaft. I used a block of thick steel plate, machined out a notch to fit the splined shaft, and then welded the plate to the shaft. I cut a rounded contour into one side of the steel plate so that it would fit snugly into the coupling.

After that, I test mounted the steering column into the vehicle to get a rough idea of how it would sit, as well as where it would place the steering wheel for maximum comfort and control. Once I got a rough idea of how the column would sit, I used cardboard to mock up the dash bar, which will support the steering column bearing. I used my tube bender to bend a section of chromemoly tubing into the dash bar, and tack welded the bar to the chassis.

Once again I moved the steering column into position, and then fabricated a bracket out of angle iron to support the steering column bearing. After some adjustments I welded everything up solid.

Below is a picture of the excellent Momo steering wheel I purchased for the car. I had to machine a hub adapter out of aluminum to mount the wheel to the Sweet Manufacturing quick release hub. Like a race car, the quick release hub will allow me to remove the steering wheel to make it possible to get in and out of the vehicle. The hub adapter also provides enough space to mount perhaps the most important vehicle control for a New York driver: The horn button!

Below is a clear shot of the quick release hub, as well as the completed steering column, supported by bearings in two places. I ended up shortening up the steering column by approximately 4 inches in order to put the steering wheel a more comfortable distance from the driver, as well as to take advantage of the collapsible steering column, which is an important safety feature.

Though it took a long time, the steering wheel is now in the ideal location. Although the steering wheel comes in to the driver at a slight angle, once in the seat the steering feels perfect. This is because the narrow pedal box will force the driver to sit at a slight angle toward the center of the car, and as a result I mouted the seats with a slight angle to them.

Speaking of pedals, I received my pedal assembly, which is a Tilton floor mount 3 pedal assembly, made of steel and aluminum. The three pedals together do not fit in the footwell of the car, so I removed the accelerator pedal, which I will later hang from the cowl bar. Remaining are the brake pedal and clutch pedal. The brake pedal operates a balance bar, which acts on two individual master cylinders, one for the front brakes and one for the rear brakes. There are a couple of nice things about this. First of all, it allows me to use two completely separate cylinders for front and rear. Since the front brakes are much larger, and there are two of them, I can use a large cylinder up front, and a very small one for the rear brake. The other great thing is that by adjusting the balance bar, you have total control over front to rear brake bias. Tilton even offers a remote adjusting kit, as shown on the picture to the right. The remote adjustment allows you to adjust the balance bar via a knob that you can mount on the dashboard, for brake bias adjustment on the fly. To further insure accurate control of brake balance, I also purchased this brake proportioning valve. The proportioning valve sits in the rear brake line and can be used to reduce the pressure to the rear brakes, without reducing pressure to the front.

I am just waiting for the master cylinders for the rear brake and the clutch slave cylinder, and then I will be able to mount the pedals into the car. I am also beginning to design the transmission shift linkage.

Next Entry

3/10/08- We got a lot of work done for this update, and the vehicle is really starting to take shape. A couple of developments happened this month:

First, I received my wide tire swingarm kit from Randy over at Chrome Addiction. Check them out on the web for all kinds of custom sportbike accessories. Randy was super helpful at putting a kit together for my project, and in general they were a pleasure to deal with. As you can see, the kit includes the wide tire swingarm with jackshaft, the 360 size Monster tire and wheel, and all the necessary hardware to make it all work. All I have to say is that the kit is super trick, and really adds to the custom feel of this project. More importantly, it gives me as much tire as possible so I at least have a shot at putting some of this turbo horsepower to the pavement. The wide tire swingarm kit adds around 57 lbs. of weight to the total vehicle.

If that wasn't enough excitement, I also received a package from the United Kingdom, which had my 2 race car seats from Tillett. These seats are made of a layup of carbon fiber and glass reinforced plastic and weigh only 9 lbs. They are finished off with alcantara padding and have a nice reclining position. I selected these seats for the Tillett high quality, as well as the fact that they were one of the only seats available that would actually fit into the tight driver's compartment. The seats come with aluminum mounting brackets and sliders. All I had to do was create a flat surface out of strips of thin steel plate and steel box tubing, and then bolt the sliders down into the chassis. It took a little longer than I expected to get the driving position perfect, but wasn't too difficult. The seats are so comfortable I feel like taking a nap every time I sit in them.

With the seats in place, I can now locate the steering column and weld in the dash bar to the chrome moly frame to finish off the cockpit. I will also working on installing the pedals.

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Important engine developments...

Regarding the new "Mark II" engine that is being tuned by Downs Engineering over in California: After extensive dyno testing, Mike Downs informed me that he does not feel that the engine can safely and reliably produce 400 horsepower on 93 unleaded gasoline, despite the larger turbo and large intercooler. I said no problem, I'll run it on race gas. The final solution is an engine which I can either run on pump gas or race gas. On race gas, the engine will produce 385 horsepower at the sprocket, which, if you consider a 10% drivetrain loss, amounts to around 428 horsepower at the crank! And, if I want to run on pump gas, I simply flip a switch which reduces the boost and provides a richer fuel and ignition map, and the engine will run safely on pump gas, at a reduced power of around 360 bhp at the crank, or 325 at the sprocket. By comparison, the older engine with the smaller turbo was putting out 290 bhp at the sprocket which equates to around 320 at the crank. I will keep the old engine as a spare. The work on the new engine should be nearing completion very soon. I am waiting to receive this engine before I mount the rear end to my chassis. With 428 horsepower, this car will have a power to weight ratio of around 2.6:1, which, in plain english, means this car will flat out haul ass.

Stay tuned for more updates soon. Next Entry

To see the first part of this project, please click here.