In order to run the engine inside, I had to set up an external exhaust to get the fumes outside. This had been done with a big exhaust manifold attached to a flexi rubber marine exhaust hose, and then poked through a hole in the wall. This was ok operating the engine at idle and under low loads, but the rubber hose would get extremely hot under high load high speed conditions. It then began to melt internally and was causing the whole building to smell of burning rubber.
To try to cool the exhaust off, we wrapped some copper pipe around it and connected it up to a water tap to run cold water through it. This may have helped a tiny bit, but I think that the heat transfer between the walls of the exhaust pipe and the copper pipe was just too little.
So now, I’ve got an Exhaust Gas Recirculation cooler hooked up instead. This is basically a exhaust – water heat exchanger, and is much much more effective. The post – exchanger exhaust temperature without running water through creeps up to 150 degrees C, and with the water cooling, stays down at 40 degrees C under all load and speed conditions.
More pictures here: http://www.flickr.com/photos/gadgit/sets/72157634497137933/with/9218975404/