In one bay door goes the raw material: sheets of stainless steel, aluminum extrusions and castings, tubes of carbon fiber, and of course miles (and miles) of titanium and stainless steel tubing. Out another bay door flows a steady stream of finished product: exhaust systems some would call art more than performance accessories. Inside the 56,000-square-foot facility, artisans-- both human and machine--ply their craft: cutting, machining, stamping, bending and welding the raw material into its finished form. Follow along as we tour Yoshimura R&D;'s new Chino, California, production facility shortly after its completion to find out just how exhaust systems are made.
While most of Yoshimura's exhaust systems are delivered to your door almost completely assembled, there are a surprising number of component parts that need to be manufactured. Aside from springs, raw castings and carbon muffler sleeves, all the individual parts are fabricated in-house. Header tubing must be bent into shape and welded together. Spigots and flanges are stamped or machined. Canister end caps are manufactured using a variety of methods, depending on the shape and material required. Inner silencer cores are rolled and welded together, as are the metal outer skins. And finally, all the component parts are assembled. During the entire process, constant inspections for quality are made, as are between 20 and 30 checks for fitment. It's a complex process with an incredible number of detailed operations.
Now we know the how behind exhaust pipe manufacture, but not the why--as in why the individual tubes and parts have the size and shape they do. For all the automation and advanced technology on the manufacturing side, exhaust-pipe design is still mostly a trial-and-error process, and in fact the design team at Yoshimura is largely based on the experience of CFO Mr. Watanabe--who still welds the race-team pipes himself.
Development of a new pipe begins with a close study of the stock exhaust pipe from the model the system is for--manufacturers themselves are so advanced in header technology that the Yoshimura design team can often begin with that as a starting point. In many cases, the final pipe layout is determined more by packaging requirements than performance--getting the individual header pipes around the engine, radiator, bodywork, sump and suspension linkage leaves only so much room to work with.
There are many aspects of an exhaust pipe that can change performance. The diameter and length of the header and S-bend tubing, the location and size of any crossover pipes (between the individual headers) and the silencer dimensions can all play a part. Once a preliminary design has been finalized, a prototype will be constructed on the bike. Dyno testing and experimentation commences, with changes made based on past experience. It all seems fairly straightforward, but there are nuances involved, and in many cases the Yoshimura staff looks to the experience of Mr. Watanabe (or even Fujio Yoshimura, who visits twice yearly) rather than computers and notebooks for answers.