High Excavenging Exhaust

Breathing keeps alive, right? Well, imagine a runner that can inhale air normally, but when it comes time to exhale, has to do it through a straw! A lot of that exhale would stay in the lungs and eventually the runner would collapse from rebreathing the same carbon dioxide waste over and over. This analogy perfectly illustrates the exhaust efficiency of marine engines that are fitted with traditional cast iron manifolds.

One very important feature for a marine engine is to be able to efficiently eliminate all the combustion gases so that the cylinders remain empty after the exhaust cycle. If proper exhaust is accomplished, several important benefits are realized:

  • The engine runs much cooler as it has time to “empty” in between the combustion and exhaust phases
  • More true power is produced since only fresh gasoline is being burned instead of a mixture of gasoline and burnt gases
  • Less gasoline is used since the engine is more efficient
  • Less toxic gases are spewed onto the environment
  • No harmful deposits accumulate in the engine.

Thus, it is of fundamental importance that a really effective exhaust system is fitted to a marine engine. Sadly, that is not the case with a typical cast iron exhaust, which is what you see on most marine engines nowadays, including the “state of the art” ones from Mercruiser, Volvo Penta and most other brands. Cast iron exhaust manifolds are very cheap to build, but with that convenience come severe disadvantages.

The exhaust manifolds are the hottest part of the engine, and iron being a “soft” metal, it expands and contracts a lot, shortening its useful life cycle until it is no longer able to withstand those drastic expansion/cycles. That heat also demands that exhaust manifolds be water cooled, and with iron having such high susceptibility to corrosion, the repeated contact with water leads to rust spots that eat away at the metal and wreak all kinds of havoc. In fact, it is that weakening that produces cracks in the metal and leads to water intrusion into the actual engine block and catastrophic failure of the engine. Lastly, iron manifolds are shaped in a way that actually restricts the flow of exhaust gas from the cylinders, leading to the “hot cylinder syndrome” that destroys so many engines prematurely. And still, cast iron manifolds have been used for decades and continue to be used by the biggest companies in the business. Who knows why large corporations use low quality parts in their products, but when it came time to design our exhaust, we went in a completely different route.

Medusa Engines uses a system called "High Scavenging Exhaust" which, as the name indicates, extracts all the gases from the cylinders at very high speeds, creating a sort of vacuum that completely empties out the cylinders. This is accomplished through the use of a racing header that is carefully chosen to compliment each of our engines and their set up. This way, the headers provide gains of 20% in HP and Torque over cast iron exhausts and even other high performance automotive exhausts. The headers are made from stainless steel, which costs about 4 times more than cast iron but is simply the best material. The inner surface of the tubes has an ultra smooth finish that eliminates friction as gases flow trough, something that the more porous, irregular iron surface cannot do. Stainless steel is also much less susceptible to heat deformation and, of course, to corrosion. It is called stainless steel for a reason. The headers are then encased in a stainless steel water jacket that is either raw o fresh water cooled, and dissipates heat so well the assembly is always cool to the touch (don’t try that with a cast iron manifold please).

By using these exhaust systems, we allow our engines to actually reach the performance levels they were designed for, instead of robbing them of it, while extending their life expectancy well beyond that of other engines. This is one of the components that increases the cost of our engines substantially, but it is of such importance that instead of choosing an inferior system like the big companies, or charge our customers accordingly, we chose instead to decrease our profit margin so we could deliver a superior product at a great price.