Originally Posted by sunchaser
It makes sense that the engine HX would have to be larger when converting from RW to coolant cooled exhaust manifold.
If you could lay your hands on a Perkins Sabre engine flow chart you'd likely have the flow sheet you need. Mine are on the boat, left yesterday so now 1300 miles away. Boat diesel has them I'd guess. Try an internet search too. BTW I have only one RW pump, and a coolant pump of course. Works just fine.
I've got 2 new transmission RW coolers that should work just fine for that purpose.
Good points. I would think the ideal flow is to keep the manifold in the loop while warm-up, then divert flow to the exchanger as the thermostat opens. I'll research the Sabre and try to find out if that's how it works.
I think with this engine's architecture there's no way to obtain this ideal. At WOT my EGT is 900+ F., so this is significant heat being dumped into the cooling system. While at cruise it's less than half this but still contributing heat.
I've scoured the Bowman site.
I think it might come down to some experimentation and see which setup works best for my boating style. With a semi-planing hull it's nice to get over the hump at WOT and boogie (well, 12 knots). Especially when transiting choppy areas, like crossing SF Bay when exposed to the entrance, and the passengers want to get past the chop as soon as possible.
I have just totally overhauled the fresh and raw water circuits and the cooling system running at highest efficiency. It is back together as stock (raw water cooled manifold) the temp stays solidly at 180, regardless of load. The manifold is cold to the touch, as are the jacketed parts of the elbow. Interestingly, the freshwater water return pipe from the HX is much colder than I would have thought. Water going into the exchanger is around 180 degrees and comes out well under 100.
My guess is with a very efficient cooling system there is adequate capacity with the stock HX. However that's not a fair test since every day both cooling circuits slowly become less efficient until the next major service. Since the raw water circuit loses it's efficiency the fastest, just getting the manifold into the FW circuit should increase time between overhaul (since there would be fewer component in the raw circuit). I'll definitely add the air charge cooler to the annual maintenance since that thing was a mess. Would be nice to convert that to a plastic housing since the cast iron creates a swollen scale.
Thanks for the advice and please keep it coming,