Engine exhaust

[onenyala]

I am replacing the water injected cast iron drop pipe on an MD1B. These drop pipes corrode and crack after about 5/6 years and cost in the order of £100.
The replacement is a stainless steel injected pipe. The length of the new pipe is the same as the cast iron one.The point at which the water enters the pipe via a spigot at right angles to the flow of gas is nearer the end of the pipe where the flexible armoured rubber hose is connected to.
The pipe will undoubtedly getter hotter than the cast iron one as the cast iron one enables the water to runalong about half of its length before mixing with the exhaust gases.
I am considering making a sort of heat sink out of a piece of aluminium which I would clamp on to the pipe to disipate the heat.
Modern engines come with stainless steel exhausts. Any information on the subject would be appreciated.
Stuart jones

 

[VMALLOWS]

I can only talk about the exhaust bend on BUKT, but the principle will be the same.
The cast water injection elbows tend to last anything from 2 to 6 years. The failure will invariably be a split somewhere opposite the water injection point, due to corrosion caused by the hot water entering. I consider the water should enter as near the exit as possible....its purpose is to cool the exhaust from that point on. There is no point in trying to cool the exhaust bend before the injection point.

My local supplier has experimented with stainless-steel bends specially fabricated.
Apparently the first generation were not succesful. I have had a 'second generation' version for 3 years now and it seems to be standing up well. (will report back in 5 years!!).

 

[PeteMcK]

Conductivity

Stainless has a thermal conductivity a FIFTH of that of grey cast iron. Your new elbow is, in effect, insulating the hot exhaust gases until they reach the injection nozzle. I wouldn't bother to modify it.