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Blog: E36 318Ti Build: Turbo-Back Exhaust System

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E36 318Ti Build: Turbo-Back Exhaust System

Now that the turbo is located where it needs to be, it's time to begin fabricating an exhaust system for the 318ti! Exhausts come in all shapes and sizes, ranging from an obnoxious hood or fender-exit, to a subtle OEM style system.

Factors including personal preference and performance goals ultimately narrow down the design to its final form, these are a few of the most significant influences:

  • Exhaust volume - (Track requirements, neighbors, wife & kids, etc.)
  • Desired power level - (Dual vs single piping, diameter)
  • Budget - (Materials and brands)
  • Look and feel - (Low key street vs "look at me")

We've all been in this situation; Peacefully asleep, only to be mercilessly woken up by the howl of your local straight piped Honda or Subaru making its way back to its nest. Replay this sound in your head right now, and understand that this is the baseline noise level that is generated from your engine. When starting from scratch to create a full exhaust system, every decision that is made can augment the tone and volume drastically. 

  • Header runner length (Equal length = even tone, greater inequality results in a greater 'pulsed' rumble)
  • Exhaust diameter - (Larger generally provides a deeper, louder tone)
  • Resonators - (Decrease high frequencies and result in a deeper tone with a minor decrease in volume)
  • Mufflers - (Decrease the overall decibel level of the sound, while retaining the tone characteristics)

For the 318ti, I will be designing the exhaust to be relatively quiet, flow 400+ horsepower, and look slightly more aggressive than factory.

I started by drafting up and laser cutting a flange to match the outlet of my TD06H-20G turbo, and welded on a 2.5" to 3" transition section. From this point back, the exhaust will be 3" in diameter. After test fitting and making some cuts to the piping bends, here is part of the downpipe coming to fruition:

From this point, the rest of the exhaust is basically a straight shot back to the rear bumper! Next, I am adding a Vibrant resonator, and Vibrant muffler to the mix. Both of these components have a straight-through design, which will result in very little restriction to flow, and a fairly aggressive sound. 

Not only do I love data, but I am also impatient, so I want to romp this car in naturally aspirated form to get the most accurate pre-turbo baseline possible. So, how in tuner-nation is that possible when the turbo is already in the mix? 😉

I was surprised to find that the above👆block off plate managed to survive dozens and dozens of anti-lag fireballs.😶

I removed the exhaust after a week of running to inspect everything, so please enjoy the following images of the fully-heat cycled setup: