Exhaust System
The exhaust system is the same as last year - Hooker long tube headers, and pair of 3" cats from Internet Racers Supply, and a 4" Mufflex cat-back. That's header wrap on the over-axle tube, placed there in my ongoing effort to keep the gas cool. I also added a layer of thermal insulation to the existing gas tank heat shield, as shown on the right. The y-pipe was bent and welded by a now-defunct muffler shop in Santa Rosa, CA, which was recommended to me by Flowmaster, who supplied the two-3" to one-4" adapter. This exhaust is LOUD.
Spring 2003 update: The exhaust has changed over the past few years. The Morflow cats from IRS took one too many speed bumps and spilled their guts, so they got replaced with a pair of 3" inlet/outlet Car-sounds. My ground clearance was pretty poor so local f-bud Alan Blaine (Blaine Fabrication) welded up a new y-pipe that resulted in at least another inch of clearance under the driver side cat. Alan added a pair of O2 sensor bungs for my wideband setup.
I had to shove the fuel lines around (again) to get them away from the raised cat as shown below. The last big change was to replace the heavy and drone-y Flowmaster with the vastly lighter (and better sounding IMHO) 4" Borla XR1. Alan sliced off a bit of tailpipe so that the exhaust is barely visible from the rear. What is visible in the bottom pic is the 4" hanger holding up the Mufflex cat-back, which is *heavy*. The bolt from that hanger goes through a hole under the rear seat bottom cushion. This exhaust sytem is as solid as a rock!
The driver's side cat motivated another heat shield, shown below left, along with the complete rerouting of the fuel and brake lines in the tranny tunnel. See Fuel Delivery for 600 hp for pix showing the reroute. Because there is no clearance for anything in these cars, especially big exhaust pipes, routing and locating the pipes is a big deal. I added the hanger that is near the right edge of the right hand pic to keep the y-pipe from resting on the BMR torque arm crossmember. That's the positive battery cable emerging from the floorpan near the center of the pic.
Spring 2003 update: The hanger described above didn't work out very well. Heat from the cat toasted the rubber part to a crisp about every 3 months or so. I got tired of the maintenance it, so replaced it with the hanger shown above.
While the engine was out following its demise at Sacramento (Boom #3), I rerouted the ABS wheel sensor wire on the passenger side as well as the bundle containing the knock sensor wire, starter solenoid wire, and a ground wire that had been too close to the Hooker long tubes for comfort. To further protect these bundles, I added the small aluminum heat shield shown below, and glued insulation mat to the a/c box. The bundle can just barely be seen between the 2 aluminum tubes emerging from behind the left side of the pop-riveted heat shield. I reused the factory aluminized tape on the bundle. The heat-shield-wrapped wire popping out from underneath the a/c box in the left hand pic is the passenger side O2 sensor wire. It routes under the stock cat heat shield.
I have not had any success with metal gaskets, either aluminum or copper. I tried Percy's aluminum collector gaskets for a while, but apparently a blown car generates too much exhaust heat for them. The pic below left shows what they looked like the last time I removed them. I just took 'em off and shot the pics, honest! The other 2 pix show the result of my 1 week experiment with SCE copper header gaskets. To be fair, I need to mention that I had to open these up a bunch to fit Blackstone's latest exhaust port shape, but still... They were on one week, and the car had a chuff-chuff-chuff exhaust leak sound from the get-go. I've never seen header gaskets so thoroughly blown out.
