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It’s no secret that the most effective exhaust systems used on naturally aspirated (non-supercharged) race engines feature merge collectors - Burns Stainless merge collectors, predominantly, in professional racing classes.

What is less obvious is that the premier racers and engine builders utilize an entire engine breathing technology, carefully designed and specified to produce near-ideal torque and horsepower curves.

Burns Stainless has developed X-design*, our parametric exhaust system modeling computer program, that has demonstrated remarkable success in predicting optimal header and collector dimensions in an extremely wide variety of applications.

The program uses as input an engine’s bore, stroke, and compression ratio, camshaft and cylinder head dimensions, horsepower and torque numbers, and the customer’s design targets, and renders detailed specifications of the ideal exhaust system parameters. In the case of a cylinder head with 4 ports, both a 4 into 1 and a 4-2-1 system will be configured.  If it’s a 6 port head, we can model three possibilities: 6-2-1 (usually the best solution), 6-3-1, and 6 into 1 (rarely recommended except in some turbo applications because the excessive collector volume diminishes the merge effectiveness).

This essential service is included in the purchase of our Merge Collectors and we strongly recommend that racers take advantage of this service, as a kind of guarantee that the results are consistent with the state of the art in exhaust system tuning.

If you’re interested in enhancing your engine’s horsepower and torque curves, please complete our Race Engine Specification Form . The results may surprise you.







* a short X-design history and rationale


X-design has evolved from our extremely successful DesignSYS program in response to a growing need in the community of motorsports racers and engine builders to effectively manage the incredible amount of information and data essential to a competitive effort.

Our core business of designing and building racing merge collectors and  header systems has demonstrated that current race engines respond dramatically to small variations in the exhaust tract when volumetric efficiency exceeds 100%.

The most critical area is the outlet of the merge collector - its shape and diameter.  In a highly developed racing engine, the collector outlet interacts in an organic way with elements as far removed as the intake valve and camshaft and all the way to the tailpipe.

In a typical mass-produced drag header, for instance, the header tubes are frequently about 10 to 20% longer than necessary and joined into a large, straight, “cannister” style collector.   This setup can produce good horsepower in a relatively narrow rpm range, and is usually sized to maximize the horsepower peak.

You can win races with headers like this, but conditions have to be just right, and you may need to play around with 2 or 3 different sets of headers during a weekend of racing.


Merge collectors change the game.  When properly designed, they keep or augment the horsepower peak, and fill in the power curve from the torque peak on up.  It is not uncommon to see gains of 15 to 25 hp with a good merge collector system, compared to a mass-produced cannister setup.

The rub is that the merge collector must be designed for your particular engine. Your camshaft and valves, your combustion chamber, compression ratio, exhaust port, and your header configuration, all communicate intimately with the merge collector, especially when your motor is working at greater than 100% volumetric efficiency.  If the basic collector parameters are not designed with these factors in mind, your motor won’t realize its potential.

X-design, used in concert with our Race Engine Specification Form, virtually assures you (and us at Burns Stainless) that our merge collectors will provide you with state-of-the-art performance.  We are constantly refining and updating the program, and based on feedback each week from our customers, the success rate is very high. In a community where the state of the art changes at a dizzying pace, X-design is an essential tool in the quest to compete.