After fighting Maine rust all my life it was a no brainer to use stainless steal for the exhaust. The pipe would be single 2.5″ mandrel bent stainless from the collector all the way thru the stainless muffler. I know I’ve probably given up a tad in performance but having had header issues in the past it was decided to stick with the original TR6 twin pipe exhaust manifold. The header issues I’m referring to are poor fit, leaks, noise, and once again my old favorite- rust. The new pipes are made from Dynomax mandrel “J” and “U” bends then TIG welded together.
Finally the car is pretty well along and and running well with the supercharger. I’ve wanted to take it to the dyno for sometime but it seemed a waste of money until the exhaust had the capacity to handle the flow without excessive backpressure. Earlier I had done some backpressure tests and found the stock twin pipe system had no more than a about 1 psi of back pressure even at redline. That was without the supercharger, it was another story under boost with backpressure topping out at 9psi!
The very first pipe in the system is not stainless. Not that stainless wasn’t my preference but I couldn’t locate stainless mandrel bends in 1.75″ pipe in time. The original twin header pipe was made of 1 and 5/8th tubing and there was just enough room to up that to 1 and 3/4″ and still get it down between the engine and the frame. The flange to the intake was cut from 3/8″ steel plate and the twin pipes merged into a single 2 and a 1/2″ pipe and ended at a stainless three bolt flange. There are two O2 sensor bungs in the collector, one for the car’s O2 sensor and a second for the dyno’s sensor. The flanges were custom cut by Harbor Propeller of Cundy’s Harbor, Maine. As it turned out we didn’t use the dyno bung. From there back it was simply a matter of fitting and welding.
Using 2 and 1/2″ pipe is about the max that will fit and it does hang down a tad as it goes under the overdrive mount. Got to think that 2.25″ tubing would suffice in most instances. Anyway there is a splice in the system just past the differential joined by a band clamp. Between the band clamp and the flange at the rear of the header, the pipes can be easily disassembled.
The muffler started out as a Dynomax Ultra Flow and had it’s spouts trimmed way back in order to make the very tight bends. Ultra Flow is a perfect description of this muffler as you can look right thru it and drop tennis balls right thru. The tailpipe exits at the left rear corner heading straight back. It’s been left a bit long as the old system used to give me a whiff of exhaust at times. No fumes from this set up.
No fumes doesn’t mean no noise. The car is loud- well at least I think so and REALLY loud with your foot on the floor when running the blower! I have been ready to cut it off and start over but my friends and even my wife tell me it’s not offensively loud from outside the car. I must be getting used to it and even like the sound now. Vroom Vroom
Finally in October the went for dyno tuning and you can hear the exhaust on the video clip. From the front you hear the howl of the supercharger and from the rear you really hear the exhaust roar. Soon a page will be put up with the dyno video (it’s now December of 06 and I’m working on it).