Tuesday, March 31, 2009


The 18 tooth CB750 sprocket arrived today. It replaces a wobbly hack job that someone created from the hub of one sprocket welded onto another smaller sprocket at a 5 degree angle. More importantly, it means we can start the fan up under motor power, and start it we did. It's hard to describe the feeling of "this is a really bad idea" that washes over you as you see the fan start to spin.


Only 4 days until the race. There is still much to do. On the plus side, much has gotten done. the car itself is pretty much race ready. Only a few minor details like roll bar padding remain on making the base civic ready for the race.

The fan system needs a bit more work. The fan itself is installed and we have a sprocket for it. The mating sprocket for the CB750 motor should arrive today. That means tonight we potentially can have the motor turning the fan and creating more noise and safety risk in my driveway. The motor is mounted and seems to run OK on most of it's cylinders. We still need to armor the fuel lines so they don't get torn apart by bits of gravel.

The manifold is close to complete. I've welded up 90% of the frame. Mark is halfway done with the lightening/air passage holes in the center spar. Once he's done we just need to weld it in place and put on the skin. The sleeves that it mounts to on the car are already welded in and I've made the shackles, so it will be ready to hang tonight.

The big thing remaining is the ductwork. My dad came by on Sunday and Monday and helped us get a head start on it, but there's a lot of stuff to figure out. We've got to cut the hole in the floor and get some kind of bellows between the body and manifold.

Wish us luck!

Monday, March 30, 2009

Our Lady's Skirt

So part of the secret sauce of this project is to do something that nobody in racing has before: build a suction downforce rig that channeled the force directly to the wheels. The Chaparral and Brabham cars came after the rules had tightened, so they used the body of the car as the "manifold" on which the suction forces could act, requiring a very stiff suspension to keep the car from dragging on the ground when the fan was on.

We are building a completely separate manifold. Imagine an upside-down John Boat hanging off of the suspension by shackles near the wheels. Initially I thought we might make it out of plywood like a homemade boat, but the high forces, low profile and proximity of the cat lead to an all steel design. Needless to say it's not light.

I had hoped to use the shock mounts as a mounting point for the manifold. It seemed like a convenient way to hook in to the suspension fairly close to the wheels. Unfortunately in the front there is not a lot of clearance around the shock mounts, and the shackles that support the manifold would rub the front tire. We also noticed that the shock mounts move a bit more than we hoped, about 1" over the full travel of the suspension, which would in turn change the air gap around the manifold. So instead of using the shock mounts we welded sleeves to the lower suspension arm on the wheel side of the shock mount. This gave us more leverage to resist motion and also allowed the front shackles to be better positioned to avoid rubbing the wheels.

Check out the crappy cell phone video of the system in action. I'm pushing on the car to move the suspension, and the front beam of the manifold hardly changes its height relative to the ground!


Trevor went to the pull-a-part today for mufflers. It was pretty evident to us even before the CB750 motor was running that the straight pipes weren't going to make it past the 95dB@50ft@WOT noise restriction. It seemed a shame, as the pipes looked pretty awesome sticking out of the back of the Civic.

What he came back with was mostly rust. One of the mufflers had been packed full of acorns by an enterprising chipmunk. I was initially dissappointed with Trevors haul, as the mufflers seemed too heavy to put one each onto the pipes, but Trevor and Nick managed to turn it into a work of art.

Fuel woes fixed?!

So at some point we had, in addition to the regular fuel system, an additional electric fuel pump, a by-pass style regulator and a dead head style regulator all hooked up with a maze of tubing in a vain attempt at supplying the motorcycle motor with fuel. Fuel was everywhere. We eventually gave up on regulators and decided to buy a fuel cell so we could gravity feed the CB750. This lead to our next problem.

Without building a fuel bulkhead of inpenetrable steel, we would need to buy an FIA approved fuel cell. These are high ticket items with an internal bladder that has to meet FIA specs. Summit Racing doesn't even carry them. Unfortunately that didn't keep them from selling us one. After noting the lack of certification labels I got worried and started poking around the internet to learn the details of what makes an FIA cell. I confirmed with Jay and Dan at LeMons HQ. All seemed hosed.

But today: success! I think we fixed the problem! And ironically we did it by removing nearly everything we added. I think it was Nick and John that found this incredibly elegant solution. All we did was move the return line so that it had a curcuit that ran higher than the carb intake. We then tee'd off the return line at that point and voila, we had a fuel system delivering at low-low pressure.

Saturday, March 28, 2009


We finally got the CB750 engine running on all cylinders today. We(I) had a pair of wires crossed coming from the doohicky that triggers the spark units. In my defence, the wires were colored in pairs (2 yellow, two blue) so I didn't think it mattered if the yellows or blues were switched with another wire of the same color.

Thursday, March 26, 2009

Me and My Buddy

As Mark said when we opened up a package: "It's full of WIN!"

Our flailing arm inflatable tube man has arrived. I think we got it from this guy:

Tuesday, March 24, 2009

Fuel Blues

We worked on the wiring last night, hooking up the kill switches and start buttons for both the Civic and CB750 motors. The reward at the end should have been the thunderous roar of both motors. The actual result was fuel everywhere.
The Civic motor started up fine. The fan motor at first was not getting spark. After some wiring troubleshooting we got the plugs sparking and moved on to the next problem: no fuel.
Our plan to get fuel to the fan motor was to tee into the high pressure fuel line and run it to a regulator so that the carbs wouldn't get flooded with fuel. With no gas coming we took another look at our setup and realized we had plumbed into the low pressure return line. Another tee into the correct line and we tried again. The result: fuel everywhere. It was leaking from the carbs and from the regulator.
Turns out the cheap Holley regulator we bought is only intended for use with a low pressure fuel pump and can only handle a few psi of input pressure. The fuel injection on the Civic runs closer to 50psi and was overpowering the regulator which in turn overfilled the carbs.
So now we need to find a new regulator that can handle the high input pressure but still deliver only a couple of psi to the carbs.
Update 5 hours later: the tech guy at Aeromotive pointed out that we don't understand how fuel regulators work and put us on the right track. The key is that the bypass type regulators allow fuel to pass until the UPSTREAM pressure has dropped to the set point. Thus, even if we had a regulator that could handle the input pressure, it would have short-circuited all the fuel headed for the Civic motor. He suggested putting a bypass regulator on the return side of the Civic regulator, forcing all of the return fuel through it and raising the return fuel pressure to the 4psi setpoint to feed to the carbs. This will probably boost the Civic FI pressure a bit as a side effect. Either way, the Holley non-bypass regulator was not the one for the job.

Sunday, March 22, 2009

Look upon my works and despair...

Our big challenge for the last couple of weeks was figuring out how to mount the fan securely. I was imagining a big water-jet cut piece of .25" steel that we could bolt the fan to that would extend out and attach to the roll cage. This made me sad, as it would be time consuming and expensive.
Then a big lightbulb smashed against my head while I was scrounging scrap metal in the shop. I came across a steel ring we had gotten when we were trying to mount a better vent fan in the server closet. It was essentially a piece of angle iron that had been rolled into a hoop. Fortunately McMaster had a large variety of sizes including a 24" diameter that would perfectly fit our fan's bolt circle. After adding some .125" gusseting around it, I'm pretty sure the car would have to be completely destroyed for that fan to move.

Thursday, March 12, 2009

Need New Belts

We've had our racing harness sitting around for a while now. The cage needed to be in before we could install it. More recently we've been putting it off because we still had various bits to be welded, and we didn't want to risk damaging the webbing.

Now that we finally got them in.... they're too long. We have the kind with the bolt plates at the end of the shoulder harnesses and there's too much slack for the adjustment to take up. I've got the ones that loop around the cage on order.

We also noticed that the angle they make with our shoulders is much more than the 15 degrees in the LeMons rules. Partially because the SCCA rules specified 0-20 degrees, and also due to the fact that our shoulders come over the point on the seat back to which I measured. We'll be cutting out those tubes and putting the proper height ones in this weekend.

Magic Hub

Now that the motor runs we need to connect it to our fan. The simplest way seems to be to use the motorcycle's chain and turn the fan like it was the rear wheel of the bike. This lets us use the transmission to have some control over the motor/fan speed and to use the clutch if we need to.
The only trick is to find a way to mount a sprocket on the fan. Unfortunately the fan shaft is a 1-13/16" diameter: not exactly a stock size for a Honda chain ring. Thus we need an adapter hub. This one is designed to be built from a 3" piece of round stock and a 3/8" plate. We're having it built by a local fab shop because we don't want to spend $200 just to buy a broach.
Update 3/24/09: McMaster carries bushing mount sprockets for ANSI 50 chain which is compatible with the 530 chain that most motorcycles use. While McMaster doesn't carry 1-13/16" Taper-Lock bushings, Grainger does.

Saturday, March 7, 2009

It Lives!

Our motor lives! After peeling off all of the electrical tape and tracing wires that were joined by twisting together the stripped ends and covering with said tape, we finally got some cylinders to fire! Not all of the cylinders, but enough, and we think we can get the rest going too if we get the ignition wiring figured out.