There are a couple(two that I know of) aftermarket exhaust systems that companies have made for this particular swap. The available units are well constructed, however I thought that I could build an exhaust system that suited this car better, and do so for a fraction of the cost. So far, it is looking as though I have done just that. My top priorities for this exhaust system were performance and ground clearance. Performance is self explanatory. Ground clearance is also important because this car will be low to the ground and having various parts of it, namely the exhaust system, scrape the ground under certain conditions will make unfortunate noises and potentially cause damage. Stressing over the ground clearance of the exhaust system also provides more space for the addition of a full flat underbody, which has aerodynamic benefits, in the future.
I built this exhaust system from 2.5″ aluminized steel pipe. I chose aluminized steel because I can weld it with equipment that I already have and it provides some corrosion resistance. The pipes were cut by a chop saw with a friction blade. Mandrel bent tubes of two different radii and straight sections of pipe were purchased. Unnecessary bends were minimized for the sake of performance. The welds were intentionally made with a cooler setting than what would normally be advised. I did this to avoid excessive penetration, which would likely result in some extra turbulence in the pipes.
The shape of the system was chosen to maximize consistency between both banks of cylinders. Since the passenger side header lets out further forward than the drivers side header, and has a sharper bend to clear the starter motor, the x-pipe was placed closer to the passenger side to help even out the length of the two runs of pipe that lead to and from the x-pipe. The x-pipe is present to even out the pressure between the two sides of the exhaust system, allowing the system as a whole to be used more effectively. The x-pipe also results in a scavenging effect which helps exhaust gasses leave cylinders. A V8 engine has two banks of four cylinders. They fire at different times, and with each firing, a pulse, or pressure front/wave, passes through the exhaust system. Since the firing in the two banks is offset, an exhaust pulse from one bank flows downstream and reaches the x pipe when the valve, of the other cylinder bank, opens to expel combustion byproducts. (The time between those events depends on engine speed.) The effect of having a pulse from one bank enter the pipe for the other bank, via the x-pipe, is a vacuum which helps draw combustion byproducts out of the cylinder with an open exhaust valve in the adjacent cylinder bank. That increases efficiency and efficiency is the key to making power.
The system nicely tucks into the bottom of the car and does not have any apparent points of vulnerability.
The midsection of the system is supported by u-bolts which attach to steel braces that attach to the transmission side of the transmission mount. That way, vibrations are isolated from the chassis.
You may have noticed that this system lacks mufflers so far, or perhaps assumed that I do not value my sense of hearing. This car will not have much muffling, but it will have some so that myself and those around me can maintain some sanity. Magnaflow 6″ round mufflers are being used. They are about 20″ long and have a straight through design. They are not currently installed due to my running out of time, however they will simply be welded onto the end of what I have already made. I will trim the bumper cover more before I install the mufflers so that they can be mounted higher. I want to mount them as high as is reasonable to maximize the space left over for a rear diffuser, another aerodynamic downforce adder that I would like to make and install in the future.
Before trimming the bumper, the mufflers leave just enough clearance for a diffuser mounted at 10*. 7-10* is the commonly accepted sweet-spot.
This is roughly how the mufflers will look coming out of the back of the car. As previously stated, the bumper will be trimmed more and the mufflers will be mounted higher. I think they’re going to look great and sound even better than they look once I’m done.
This is how the exhaust system ended up looking. I added flanges, a pair of flex pipes to take stress off of the headers, oxygen sensors, and I reshaped the back passenger side of the system for additional clearance against the transmission tunnel. This piping, paired with my pair of Magnaflow mufflers, sounds really quite good. Many have complimented the sound, and I have also gotten quite a number of comments on how it’s surprisingly quiet. Win!
I welded some steel dowel to the mufflers so that they retain their positions relative to one another, and so that I can mount them to the chassis. Hard-mounting the mufflers to the chassis has proven to be an effective means of attachment, and I can get away with it since the flex sections prevent the headers from being stressed.