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Manifolds should only be used when there is no other option.?Ǭ†?Ǭ†
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Manifolds on twin cylinder engines channel the exhaust gases into one outlet. Several 90 degree bends and weld joints are used to achieve this,?Ǭ†resulting in higher backpressure. Higher backpressure results in loss of performance and an increase in fuel consumption.
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Manifolds typically increase the cost of an exhaust system by 25% to 50%. This extra cost includes?Ǭ†material?Ǭ†and labor to manufacture the actual manifold. It also includes the extra hardware required to mount the muffler to the manifold such as clamps, mounting brackets and heat shields. Finally, there is the added cost of the muffler itself which now requires a mounting bracket and extra heat shielding due to its close proximity to air filter housings?Ǭ†and, in?Ǭ†some cases, fuel pumps.
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On?Ǭ†manual start engines, the?Ǭ† manifold/muffler is often located dangerously close to the recoil starter assembly. An inattentive or tired operator could easily use the hot muffler as a support while starting. In fact, rumor has it that there are a number of landscapers operators?Ǭ†with “TOH” (think of “HOT” in a mirror)?Ǭ†branded in the palm of their left hand.
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The advantages?Ǭ†of a dual mount muffler.
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Among the advantages of a dual mount muffler over a manifold are the following:
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Lower cost
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Increased horsepower
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Better fuel consumption
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Quicker installation time
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Better sound performance due to larger muffler can volume
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Less heat shielding required
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Regarding the last advantage, BS EN 836 Garden Equipment – Powered Lawnmowers – Safety section 4.1.3 states;
“A guard shall be provided to prevent accidental contact with any exposed engine exhaust ?Ǭ†components larger than 10 cm2 which have a surface temperature greater than?Ǭ† 80OC at (20+/-3)OC ambient temperature during normal starting, mounting and operation of the machine.”
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This means that as long as the operator cannot touch a hot surface during normal starting, mounting and operation of the unit, a heat shield is not required to meet CE requirements. Over-shielding of the muffler?Ǭ†always results in extra cost and?Ǭ†makes the muffler susceptible to backfiring and/or after-bang.
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Conclusion
SES has successfully designed a dual inlet muffler for?Ǭ†many applictions where formerly a manifold/muffler combination was the only option for an exhaust system.
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