Time For The Exhaust System

Working out the exhaust system was interesting to say the least. Pace supplied the headers but from the headers forward required the fitting of Catalytic Converters then exiting through some form of muffler. I chose to go the live side pipe route because I like the sound they make and they look good. I struggled for a long time with live side pipes or non active ones as the hazards of red hot pipes and children is always on your mind not to mention getting out of the car for driver and passenger can be an issue.

As Individually Constructed Vehicles are required to meet Australian Design Rules emissions testing, it required the use of Catalytic Converters rated at a minimum of Euro3 specifications. Trying to find cats that will fit the limited space I had to work with was a challenge. Their are plenty of cats that have lower 100 and 200 cell counts in a 4" diameter cat but I needed 400 cell in a 4" dia cat. It had to be no larger than 4" other wise it would not fit. Fortunately for me, a supplier I was talking to said he may be able to get me a pair of Euro4, 400 cell cats which he dug up from somewhere and he delivered well, not cheap but I was in no position

to argue.

I also had them supply 1-5/8" to 2-1/2" to 4 pipe and 1-7/8" to 3-1/2" to 4 pipe merge collectors while I designed mounting flanges for the merge collectors to the pipes and had them laser cut at a local engineering shop. Pace supplied flanges to match the headers. I also made the gaskets to suit the flanges

Before the cats can be routed through the gap I had to have some idea of where the side pipes are going to sit and how far from the body they will be so I set up some boards on axle stands and presses them up against the under side of the car as I didn't want them hanging down. The side pipes had to be cut down so the correct length of the cats and merge collectors can be determined.

Once a rough idea of the length and angle of the cats is established it is only a matter of directing the angles and cutting the cats and merges at the right angle, sounds easy doesn't it but it ain't. Without going into blow by blow detail, their is a lot of small cuts on both the cats and merges taking care not to cut too much off as the cats on a pretty steep angle and it would be easy to make the cat too large for the merge

It is a bit of a trick getting the merges to point in the right direction so they line up with the opening in the body and have equal spacing around the pipes. After a lot om mucking around it was time to set up the side pipes. The cats are in the tacked up state at this stage. I wanted a more aggressive look so opted for the pipes to exit the body on as much angle as I could manage and you will notice the pipes fall away 30mm over their length. You can't see it here but they also slay out from the body 12mm but still remain inside the tyre line.

It's worth adding that the flanges are a very tight fit on the pipes and I was able to position the flanges on any angle to get the required look with out tacking. When I was happy all was sweet I took the cats to some gents who are a lot more competent with a TIG than me and they did a great job. I also drilled the holes for the O2 bungs and had them welded in.

In my next post I will show how the side pipes were mounted and the brackets used.

Until then,

Cheers
Russell.