exhaust water injection elbow

[wescarroll]

When I first got my boat the injection elbow, the custom made one with the little pipe welded on had been replaced by the PO. He used a standard elbow for the exhaust, and a tee below for the water injection. I used this setup for 5 years, and only recently replaced it with the injection elbow. My question is why do we use the special elbow when it is so expensive comparatively?

[negrini]

There are several conceptual points behind a marine exhaust elbow. Nigel Calder says to comply with all these points, an elbow should be made of Tungsten, unnaceptable due to price. In fact, diesel exhaust combined with saltwater produce a strong jet flow of sulfuric acid at just the elbow. That's why even stainless steel can't hold the punishment. Even risking an internal puncture on a water-cooled elbow, injecting water way below the elbow will create an unwanted high temp spot.