Ok, here’s what’s been going on since the first race weekend… My single biggest issue from the Feb. race(s) was a bad vibration. After thinking about it a lot I convinced myself that it was the exhaust touching the axle. Because of the 3-link and coil overs the guys at Johnny Franklin Mufflers routed the exhaust UNDER the axle. I jacked up one side of the car a bit (not enough to get the wheels off the ground, just enough to simulate the car leaning) and got the axle to touch the exhaust. I then looked at the axle and exhaust and felt like I could see evidence of rubbing. So, out came the sawzall and I cut the exhaust before the axle and re-used the chrome tips to direct the exhaust down and to the side. I was pretty happy with how it turned out and pretty confident that I had fixed the vibration.
But… I wasn’t sure. And the more I thought about it the more I felt like the vibration didn’t only happen when the car was leaning. For example, heading to turn 7 at Infineon. After coming down out of the carousel the run down to 7 is flat and yet I realized that I was getting the vibration at the end there just before the braking zone. I really didn’t want to go to the next race with that vibration so I decided to take the car to Evil Genius Racing in West Sacramento. They’re the guys who built the rollcage, seat mount, fuel cell mount and pedal box. I figured we’d run it on the chassis dyno and see if the vibration showed itself… well, it did. So, I was wrong and the exhaust was not the problem. John at Evil Genius suspected pinion and yoke angle mis-matches just from my description of the vibration. when we got there they measured and I believe the engine was down 4* and the pinion was basically at 0*. Aha! that must be it… so we adjusted the upper link and got a couple of degrees up on the pinion. The vibration was still there… next we took the rear wheels to a tire shop to re-balance the wheels. The wheels were going to take an hour to get done so we headed back to the shop. I was trying to think of anything else I could do to try to narrow down the vibration. I mentioned that I should really get the driveshaft balance checked when I get the car back. They said, “well there’s a driveshaft shop around the corner”. So we pulled the shaft and took it around the corner. As soon as we put the shaft on the counter the guy was looking like he didn’t approve. He said it was too long (53″) for the diameter (2 1/2″) to be safe above 3500rpm… he also pointed out that there were no weights anywhere on the shaft and said there’s no way it was balanced. We started talking about options and I asked if they made aluminum shafts. They did, so I decided to have them build me a 3″ alum. shaft.
By then it was getting late so we picked up the freshly balanced wheels and brought them back to the shop. I left the car with Evil Genius and went home. Hank picked up the driveshaft the next day, installed it and the wheels and did another pull. Bingo, he said the vibration was noticeably reduced. There was still some vibration that he felt probably shouldn’t be there but the really strong (he called it violent) vibration that came on at a bit over 100mph was gone. He had also figured out that the vibration was/is speed related, not rpm related. So, I picked up the car on Saturday and brought it back to Jeff’s shop and spent the rest of the day doing some odds and ends.
Here’s the list of things that go done since the first race:
-put on my AIX Outlaw stickers
-re-installed the power steering belt (which we removed because of my leak, with the belt off the pump didn’t turn on the dyno)
-sealed my shifter plate (Don said he felt I was leaking fluid out the top of the trans, so I checked and I had stupidly not used anything to seal the shifter. I laid on a bead of silicone and bolted it back down).
-installed a shorter alt. belt (the EGR guys said the one I had on wasn’t tight enough and I had the alt. as far out as the adjuster would go)
-fabbed a mount for my lap timer and started running some wires so that I can run it and my GoPro camera off the car’s battery (I’m sick of the camera or lap timer running out of batteries in the middle of sessions/races). I made the mount because the suction cup just wasn’t working on the lexan windshield and I don’t want the thing falling off and hitting me in the face or flying out the window when I’m on the track.
-swapped my left side net to a mesh style for better visibility
-put a 1/4″ piece of hard rubber between my trans and trans mount. The EGR guys (and other people also) had commented on the rigid mount and suggested I do something to add some compliance. Hopefully this will do the trick.
whew… so, that leaves me with the power steering leak and finishing off the wiring for the lap timer/camera. My plan for the leak is to switch the hard line that’s leaking for a -6 hydraulic hose. I ordered the fittings I needed for the rack from Summit. Jeff’s going to pick me up the hose and fittings I need to build the line. So Tues. night I’ll go to the shop and put that all together and, fingers crossed, that will fix the leak.
here’s a few pics: