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Regardless of the engine type, exhaust and engine builders are presented with a very challenging spatial problem when designing a tubular exhaust header system. Multiple complex branches made of arbitrary straight and bent sections of preset ODs and lengths have to be arranged in the best possible way to create a compact package that is also easy to fabricate. But determining which one is the best layout among all the possible pathway combinations the runners can follow is the real challenge . If we define the solution to this problem as devising a method to explore as many combinations as possible and zeroing in on the most feasible, at minimal cost and in the shortest period of time, a strategy to tackle it can then be drawn.
	By breaking up the overall solution to this problem into a finite number of partial solutions that can be solved one by one, the design problem is dramatically simplified. icengineworks^TM , earning a patent in the process, has successfully turned these partial solutions in our problem into modular, interconnecting straight and curved plastic modeling elements or blocks of certain OD and same length that faithfully represent round metal sections in an exhaust header design.
When assembled, these blocks form long strings that serve as 3D models of actual primary runners. By carefully choosing and positioning each block added to an assembly while keeping its total length in check, the designer gets closer and closer to finding and completing the optimal design. If an interference is found, the blocks simply get rearranged. This new design capacity to do and undo freely, opens up an unprecedented opportunity to quickly create more efficient, tighter and seemingly more complex designs than before. And the savings in terms of unnecessary labor and wasted materials start piling up right away.
	It now becomes possible to design, revise, correct and rearrange, almost endlessly, at no extra cost, without waste, any design of yours until every aspect feels right. Minimize number of sections per runner, plan for location of welds, or diameter steps, etc. Previewing is always unlimited, in real-time, in full-scale and in 3D! When the design model is ready, icengineworks^TM will aid you in fabricating an exact metal version just as easy, quickly and confidently.
SIMPLIFIED FABRICATION
	Our experience has shown us that only J- or U-bends are all it takes to turn your plastic model into a full metal version thanks to the fabricating tools and aides icengineworks^TM has developed to complement the system (please see the header fabrication tools page). Partial angle bends are no longer necessary, which drastically reduces your required metal inventory. By utilizing precision U-, or J-bends of matching CLR, available from this website on March 15th (please see the pre-bent metal tubing page), it is very easy to transfer your design model into metal, section by section. When using a large commercial vertical band saw (14" or more) for cutting, our aluminum Pivoting Table attachment and sets of high performance DELRIN® plastic Tube-Cutting Spacers simplify the task of cutting the bent sections. This is briefly how it works:
Start by downloading your design, section by section, inch by inch on the Metal Control Sheet which will become the recipe and shopping list for your design. Check it out here (PDF file). Mark the metal tubing for sectioning by simply securing a metal U- or J-bend tubing around its matching CLR plastic icengineworks^TM Tube-Cutting Spacer and placing the desired section of modeled blocks over it using the edges of the plastic spacer as support. Then, with a marker, indicate both ends of the plastic section on the metal tubing (It is recommended to use spare modeling blocks to avoid breaking your model apart at this point). The depth of the plastic cutting spacer is designed to be more that 1-1/2 times the tubing OD so that the blocks can sit over the metal comfortably for marking. Indicate also the modeling blocks' witness arrows on the metal tubing sections with the marker .
Place the Tube-Cutting Spacer and the marked metal bent section on the Pivoting Table over the band saw's worktable. Adjust the band saw's rip fence so that the blade aims at the center of the pivot on the aluminum table. Lock the Tube-Cutting Spacer in place with the wing nut and then start the cut by gently pushing the assembly against the running blade.
	This process yields all the parts to assemble each of the modeled sections, so it is important that each section gets labeled with information such as the cylinder they correspond to, the section number in that runner, and its orientation, for example indicating which ends point downstream and their witness lines.
One at a time, and for each runner, replace each model block sections with their metal version by aligning their witness lines and tack-weld. Continue until the entire design is completed.

Click on the features link to review in more detail the design possibilities the icengineworks^TM exhaust header modeling block systems have to offer.