We had a chance to get the Coupe up on the lift today to explore designs for the exhaust. The factory exhaust leaves a bit to be desired. The exhaust is approximately 2 3/8″ OD (60mm) and is even crushed down to 1 3/4″ to clear the factory body brace in one spot.
But anyway…. a quick description of the factory exhaust system.
Starting at the turbo, there is a cast O2 housing / catalitic converter / down pipe. This is something that we will work on very soon.The down pipe attaches to the mid pipe which is stainless steel and has a very nice flex section in it.
The mid pipe attaches to a secondary cat. This secondary cat is post O2 sensor so deleting this will not throw a check engine light. The pipe between the secondary cat and muffler is also stainless steel and has a bullet style resonator in it. I suspect that the ID of the resonator is smaller than the rest of the exhaust system. The muffler section appears to be mild steel. It is large and looks heavy.
The good news is that there is room for improvement. We did some careful measuring and feel that a 3″ system will fit very well and still be routed cleanly. The muffler(s) will need to be positioned in the rear of the vehicle or ground clearance will suffer. The factory system is already slightly below the level of the pinch welds in several places so any muffler positioned forward of the rear differential will be a speed bump scraper for sure (worse on lowered cars).
We are going to explore several possibilities including a side entrance dual end outlet like we are using for our BMW 335i exhaust, a dual muffler straight shot setup, and possibly a tunable exhaust like we are producing for the Evo X.
As with all exhausts we produce, the AMS Gen Coupe exhaust will use 100% stainless steel and mandrel bent tubing. Our exhausts always use stainless steel flanges and not slip joints which are known to leak and blow apart. We also only use 100% stainless steel high flow mufflers so you are ensured years and years of rust free use.
I will have more info including the weight of the factory exhaust system for you tomorrow.