After the dump pipe design was updated, it was time to finish the remainder of the exhaust system (full 2.25" from the turbo back). There's not much to it - flex joint, a couple of bends around the rear engine mount, catalytic converter, then a straight pipe to the centre mounted muffler. What I haven't done a this stage is weld in the bungs for the wideband O2 sensor and EGT thermocouple. This will be done at a later stage when I do the wiring install and figure out the final position of the sensors.
The catalytic converter I used is a metal spun, high-flow, Magnaflow brand and the muffler is a Berklee mild steel, universal sports muffler with single inlet and twin outlet. I specifically avoided a reverse flow "turbo" design muffler so the the free flow of exhaust gases was not affected.
I used some axle stands to hold everything in place while I measured/tack welded etc, and for the muffler I made up a simple cradle from MDF to sit on my trolley jack.
Once I had everything tacked together under the car and ready to fully weld, I realised that I couldn't remove the exhaust without removing the sway bar! The simple solution was to later add an additional flange just in front of the muffler so I could remove the muffler and the main pipe in separate pieces.
There are two points where the exhaust system is mounted. A fixed point at the front and rubber mounts at the rear. The fixed mount at the front of the exhaust is a bracket welded to the exhaust pipe just in front of the flex joint - where the exhaust does not move. This bracket helps support the dump pipe and front exhaust section, and prevents the weight hanging directly off the turbo and exhaust manifold. The exhaust bracket is bolted to the rear engine mount bracket via an 8mm thread I drilled and tapped.
In an attempt get as much ground clearance as possible, the catalytic converter was tucked up in the hump originally used the factory gear shifter mechanism. It is mounted approx 20mm away from the floorpan and because catalytic converters run very hot (in the range of several hundred degrees Celsius), I wanted to make a heat shield for it to limit the radiant heat reaching the floorpan. I used two 100mm stainless steel hose clamps as a base and made a simple frame over the top part of the cat. Some small pieces of steel rod was used to create some simple standoffs between the clamps and frame.
I had some heat shield material left over from when I made the exhaust manifold & turbo heat shields and this was rolled/bent and riveted to the frame pictured above. This heat shield can be easily installed (or removed) once the exhaust system is fitted.
The muffler mount is a design that is commonly used in Minis with centre mounted mufflers, which uses a rubber block mount in front of the muffler and two cotton reel mounts at the back of it. The forward mount is a standard Mini centre muffler mount bolted to some existing captive nuts in the rear subframe, with a hanger bracket welded to the exhaust pipe.
The rearward mount uses a custom bracket bolted to the back of the subframe, and a hanger bracket that loops under the muffler tips, isolated by two Mini cotton reel mounts. Premature wear/failure can result when cotton reel mounts are mounted in tension, hence I made the hanger bracket loop over the top and compresses them.
The stainless steel exhaust tips I used aren't huge (2.5" diameter) or anything fancy but I am extremely happy with how they look once the muffler was fitted. Because the tips are stainless steel and the muffler and bracket is mild steel, I changed out the standard wire in my MIG welder to a spool of stainless steel wire (borrowed from a fellow Mini guy). This was done to maximise the corrosion resistance in the weld for the dissimilar metals. After they were welded on and for a professional touch, I bead blasted the front half of the exhaust tips and painted everything in high heat satin black enamel, leaving the last 100mm of the polished tips exposed.
The last thing I had to do with the exhaust was modify the rear engine mount slightly. I removed a small corner section of the mount to prevent it fouling with the exhaust pipe bend. This change still allows all three mount bolts to be used, as per the factory configuration.
The rearward mount uses a custom bracket bolted to the back of the subframe, and a hanger bracket that loops under the muffler tips, isolated by two Mini cotton reel mounts. Premature wear/failure can result when cotton reel mounts are mounted in tension, hence I made the hanger bracket loop over the top and compresses them.
The stainless steel exhaust tips I used aren't huge (2.5" diameter) or anything fancy but I am extremely happy with how they look once the muffler was fitted. Because the tips are stainless steel and the muffler and bracket is mild steel, I changed out the standard wire in my MIG welder to a spool of stainless steel wire (borrowed from a fellow Mini guy). This was done to maximise the corrosion resistance in the weld for the dissimilar metals. After they were welded on and for a professional touch, I bead blasted the front half of the exhaust tips and painted everything in high heat satin black enamel, leaving the last 100mm of the polished tips exposed.
The final result :
The last thing I had to do with the exhaust was modify the rear engine mount slightly. I removed a small corner section of the mount to prevent it fouling with the exhaust pipe bend. This change still allows all three mount bolts to be used, as per the factory configuration.
Comments
Post a Comment