Closed loop Cooling system for Challenger 1800

[Cronullalad]

Hi all,
Has anyone had experience with converting 787 engines in a Challenger 1800 to a closed loop cooling system ?? In principle I was thinking it should be relatively simple if parts taken from appropriate Jet skis can be used. Would appreciate everyone's thoughts.

Cheers

 

[racerxxx]

Not quite sure why the open system isn't working for you. Can you elaborate on why you're thinking about this? The big problem is you need a heat exchanger. The closed loop systems use a jacketed ride plate on the newer skis, that can't be adapted to these boats due to the different pump. You'd need an exchanger that you could mount into the hull flush that would be cooled by the water you're riding in. Similar to the ones used in the new Seadoo spark



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[Sportster-2001-951C-Stock]

Gonna need more than just a heat exchanger, also will need an engine driven recirculation pump to move the coolant through the engine and heat exchanger. Then there's the problem of separating the engine cooling from the exhaust pipe.

Not gonna happen, IMO.

 

[howie099]

Its going to a ton of woek

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[howie099]

The cost and time would be a lot. If you can't put a cooling plate on the hull you need a radiator, fan, water pump how to mount it. Just to much to try to fit in.

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[Cronullalad]

Thanks for the feed back.
The reason I'm thinking this is that I now have my Challenger moored in a Sea Pen and was looking to further protect the engines internally from salt water corrosion after a run. I recognise there need for there to be a seperate pump for the heat exchanger which can be electric...initial thought was to plum the current sea water inlet to the new pump, then to the heat exchanger then back out through the exhausts to cool them. The engines existing pump will do the job for circulating the closed loop engine coolant.
Any other thoughts or knowledge would be greatly appreciated.
Cheers
Cronullalad

 

[Coastiejoe]

An electric pump would likely require more amperage than what the output of the rectifier is I would think.


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[ialonso]

My concern would be the exhaust cooling. No idea how you would overcome that. if it was engine head only you could in theory pull it off with a heat exchange and a pump. No clue how to accomplish the same for the exhaust since the heated water leaves the boat via exhaust.

 

[Sportster-2001-951C-Stock]

Thanks for the feed back.
The engines existing pump will do the job for circulating the closed loop engine coolant.
Any other thoughts or knowledge would be greatly appreciated.
Cheers
Cronullalad

The engine's existing pump is outside the boat hull, it pumps a great amount of sea water to propel the boat.

Honestly, you could sell your Seadoo and buy another boat with this type of cooling system already factory installed for the amount of time and money involved.

Here's another idea; purging some amount of fresh water through the cooling system using an electric pump or shore-supplied fresh rinse-down water after each use, can't hurt. Perhaps, maybe 5 gallons or more if possible.... Valve off the salty jet pump cooling water in favor of pressurized shore freshwater and let the engine run on that substitute water source for a few minutes to try purging the salty water from the cooling jackets and exhaust system.

 

[Cronullalad]

Hi all,
Thanks for your ideas and comments.
Maybe I wasn't so clear....my use of the term "Pump" was referring to the engines existing Water Pumps....not the propulsion unit.
As for an electric motor pump to circulate sea water around the closed loop heat exchanger and out through exhaust, something the capacity of the current bilge pump would work so no big draw on the current electrical circuits.
This was just a conceptual idea that I though was thought provoking and worth exploring on the forum.
Best regards,
Cronullalad

 

[racerxxx]

Well, unless you installed water pumps to cool your engine your jet pump is the only one in there doing the work. That is how it's been for many years. As water is sucked thru the pump it passes by small holes that feed the engine by pressure of the impeller pushing the water into those small holes. Here is a water flow diagram for a 787, the line coming from the pump is the water inlet to the engine.

The colored diagram will further explain the pat of the cooling. The lines pointing towards the engine are the cool water coming in, the ones with the arrows pointing away are the warm water leaving the system. No where in the engine is there a water pump, it's all done from the jet pump.

 

[racerxxx]

If you look in the lower left of thsi pump you will see a series of holes, that is the water in of the pump to get cool water into the engine.

 

[Sportster-2001-951C-Stock]

my use of the term "Pump" was referring to the engines existing Water Pumps....not the propulsion unit.

Yes, the jet pump is also responsible for producing the pressurized cooling water supply so there is only one pump on the entire system. Aside from the bilge pump, that is.

Aside joke FWIW, a very leaky boat is sometimes called a bilge recirculation pump, as opposed to a bilge pump. (get the joke?)

Anyway, RacerXX just provided the diagram you seek, it's a once through cooling system and there is no recirculation pump such as can be found on a Mercruiser stern drive system, for instance. In the case of a Mercruiser, a closed-loop coolant setup is possible due to the engine-driven recirculation pump. It's possible but not advisable to eliminate the Mercruiser recirculation pump thus converting the Mercruiser into a once-through system similar to the Seadoo.

Neither of these systems are terribly complex once you become familiar, remember though these engines produce insane amounts of heat that must be carried away, a low power bilge pump wouldn't come close to providing enough flow to compensate while underway.

Back in the day, we used to place a scoop pickup under the "race" boat hull and this provided the cooling water supply only as the boat was moving, and in most cases an engine-driven recirculation pump to keep water moving through the block but using this system at low/no speed or stopped, the engine didn't receive enough supply of cold water for adequate cooling. These boats didn't have reverse at the time, either! :O

So here's the basic diagram of a raw-water cooled Mercruiser which does use an engine driven recirculation pump for comparison, you can see the differences AND I bet you can guess where the system could be isolated and heat exchanger would be inserted:

 

[Cronullalad]

Many thanks for the new info. I just assumed that the engines had an internal water pump..........so, if the existing sea water pickup (in jet pump) is redirected to cool closed loop heat exchanger and then on exit re enters the exhaust system to cool it as it does now then the only additional water pump needed is to pump and recirculate the coolant inside the closed loop heat exchanger. Sounds practical ???

 

[ialonso]

Many thanks for the new info. I just assumed that the engines had an internal water pump..........so, if the existing sea water pickup (in jet pump) is redirected to cool closed loop heat exchanger and then on exit re enters the exhaust system to cool it as it does now then the only additional water pump needed is to pump and recirculate the coolant inside the closed loop heat exchanger. Sounds practical ???

Not at all, because most of the corrosion damage occurs in the exhaust. There would not be much to gain, in my humble opinion.

 

[Sportster-2001-951C-Stock]

Many marine engines do recirculate glycol coolant through both the exhaust manifold cooling jacket + engine block through the heat exchanger. In these, the seawater exiting the heat exchanger is injected (into the "riser") at the "salty end" of the manifold log to cool hot exhaust gasses before exiting the through-transom section.

The idea is there should be no parts of the exhaust system that can reach >100C/212F, boiling water is no longer a liquid and thus temp control (heat absorption) becomes unreliable due to air pockets.

Hot components in an enclosed bilge are a major cause of bilge fires, add a bit of spilled fuel vapor for the clincher.

Glycol circulation through block + manifold cooling requires an even larger heat exchanger than a block-only recirculation system. Both configurations are available, one costs a little more of course and takes up a bit more bilge space.

The block+manifold type would be actually be necessary on the Seadoo system I think, b/c these are already plumbed for series flow inherent to the casting design.

In the case of the Seadoo, some of the seawater exiting the heat exchanger(absorbed manifold+block heat) would be plumbed into stinger expansion pipe and waterbox to keep them from overheating before discharge overboard. Respectable flow balance would need to be empirically tuned I think, so this requires somebodies time and expense.

Still gonna need a hefty recirculation pump, I don't see how it could be electric considering there isn't but ~300W (0.4 HP) total capacity in the existing charging system? I bet you'll need at least a few HP to power the recirc pump?

Thus, recirculation pump requires a good deal of power. IMO a deck full of solar cells + a couple of low capacity magnetos ain't gonna cut it. Instead, place a pulley drive on the PTO shaft and connect a belt or direct drive to an 200A(2400W=3.2HP) alternator or a simple mechanical engine driven circulation pump would be the best choice IMO

This system will require a lot more work and expense than swapping over to a boat that has this design (For instance, factory air conditioning installed by the air conditioned factory is best).

If you want to get an idea of maybe a fraction of the cost, go price out a marine coolant recirculating system retrofit (With these off the shelf kits from Mercruiser/Volvo/Caterpillar/Yanmar BTW, the recirc pump is resident already, all the design and fabrication costs, empirical testing, rework, unknowns, bugs and premature failure risk are completely factored in).

Alternative choice is to enjoy your Seadoo as is till something pukes, then replace whichever parts corroded into chloride powder.

 

[Cronullalad]

Thanks Sportster for your input......seems like your final conclusion may be the smart move going forward.
Thank you all
Best regards,
Cronullalad

 

[Premix]

I'm wondering if open loop cooling would be advantageous for my 4-Tec Speedster. The bilge gets seriously hot on this thing.

 

[Sportster-2001-951C-Stock]

I'm wondering if open loop cooling would be advantageous for my 4-Tec Speedster. The bilge gets seriously hot on this thing.

I wouldn't expect so myself, considering Bombardier spent a great deal of effort, time and money designing these powertrains as a packaged system. You're best off making certain it's well cared for, IMO.