improve on dual cooling

[freestylegeek]

If you think about it, it seems like if you run it that way you will have air pockets with the water flowing down...

Hence the need for a check valve. I found one on Mcmaster Carr (p/n 7933K33) that had a 1 psi cracking pressure, and barbed fittings for 3/8 line.

I'm thinking it's worth a try this summer.


My biggest concern with cooling is with the pipe though. I've always ran a hot engine and a cold pipe. The cold pipe gives me the slowest returning sonic wave (since I have a short mod chamber that I run fairly dry).

 

[#ZERO]

If you think about it, it seems like if you run it that way you will have air pockets with the water flowing down. You will want to run it into the manifold so the flow will be up out of the head. The same for the pipe, water in at the bottom of the headpipe and exit out the top. Thats just the way I do it.

If you think about it, the water has to travel back up the head pipe and the fitting on top is higher then the cylinder head, so there will always be water inside the engine.

Also two feed lines and one pisser will ensure there is always adequate pressure in the system.

 

[crammit442]

Hence the need for a check valve. I found one on Mcmaster Carr (p/n 7933K33) that had a 1 psi cracking pressure, and barbed fittings for 3/8 line.

I'm thinking it's worth a try this summer.


My biggest concern with cooling is with the pipe though. I've always ran a hot engine and a cold pipe. The cold pipe gives me the slowest returning sonic wave (since I have a short mod chamber that I run fairly dry).

This is all very interesting, but unlike automobiles, we have a constant source of (relatively) cold water. If the warmer water of summer is putting you over the edge for deto, you need to adjust some of the parameters on your motor or use more appropriate fuel. Considering these are freestyle motors and not race boats, deto should NEVER be an issue since our motors are ridden very gently compared to sustained WOT race boats. Dual cooling run in one of the many normal configurations is MORE than sufficient for any of our motors. I'm not trying to be a party pooper, I just don't believe there's any reason to over "technify" or reinvent the wheel. What we have now works very well.

 

[Mike W]

I agree. There are 100 different ways of doing it. Most will work. We tend to get too far in the weeds with this subject just like "what oil to use"

 

[cookerq62]

I tried a number of configuration on my sj with a b pipe. The setup that worked best was:
2 lines to the exhaust manifold and 2 out of the head
one line goes to the bottom of the pipe one goes overboard
From the top of the pipe to the stinger
I think warming up the water in the engine before it goes in the pipe helps and haveing the water going in the stinger as hot as posible also helps. I supose you could run cooling from the top down so long as your pisser was higher than the top of the head to keep it filled with water.

 

[SUPERJET-113]

A lot depends on where you ride.
I have to have dual cooling here in the hot desert or I would burn it up. Its over 100* for usually 2 months in the summer(July/Aug.) and some of the water on the lake we ride in is 2-3' deep and its like bath water, but when it gets that hot, we go up the river and the water is 65 vs. 85-90 degrees. Nothing like laying in the water sweating!

When i moved here from the midwest i only had single cooling and it was not enough. I was running hotter than hell. In the spring i just block one to get it up to good running temp.

 

[#ZERO]

By routing the hose or hoses to the bottom of the exhaust manifold the water always drains back out of the pump when the ski is out of the water.

With the top feed setup water always stays in the engine since it has to exit out the top of the head pipe and enter through the top of the head.

This should also help eliminate some corrosion because there is less chance of salt buildup before flushing the ski.

I'm going to try this setup this summer on a spare 62T/61X engine with 210psi compression on pump gas just to prove my theory, that the domes need to be cooled first and the exhaust needs to be even hotter. :firedevil:

 

[teton]

By routing the hose or hoses to the bottom of the exhaust manifold the water always drains back out of the pump when the ski is out of the water.

With the top feed setup water always stays in the engine since it has to exit out the top of the head pipe and enter through the top of the head.

This should also help eliminate some corrosion because there is less chance of salt buildup before flushing the ski.

I'm going to try this setup this summer on a spare 62T/61X engine with 210psi compression on pump gas just to prove my theory, that the domes need to be cooled first and the exhaust needs to be even hotter. :firedevil:

This system makes me wonder, it sounds like a really good idea, however it may be a better idea in a 4 stroke. because hot air always travels to colder areas, so if the cylinder head was made colder and the exhaust manifold hotter, wouldn't more of the exhaust gases remain in the cylinder after the exhaust port opens, I know that the pressure difference is the primary reason the exhaust gases are expelled.....but doesn't the temperature difference help too......i always figured this is why the cooling lines where run to the exhaust manifold first....

 

[SUPERJET-113]

Thats an old racers trick to run the cooling basically backwards(going into head first)..

 

[sjetrider]

.
In the automotive world, a few racing teams have implemented reverse cooling systems on the ultra high compression, high boost forced induction engines to keep their cylinder heads' combustion chamber from developing hot spots, which can lead to detonation. I've heard that some racing teams were able to run extremely high boost pressures with this type of system that were not possible with conventional cooling systems. The heads would always develop what's called nucleate boiling, where the coolant actually boils off inside the cylinder head impeding the cooling process in that area, causing even more hot spots, and eventually causing detonation or cracks in the combustion chambers.

I'm just wondering if anyone has tried this with jet-ski engines. You almost always see detonation around the edges of the domes and on the top edges of the pistons when it occurs. It seems like you would be able to run higher compression with smaller cc domes by cooling them first to eliminate any hot spots. The only problem that I can foresee with this setup is, after starting a heat-soaked engine, there might be a possibility of cracking the domes with the sudden rush of cool water. This setup may not work with certain types of cylinder heads because some have restrictor holes built into the head shell, but I think it might be worth a try.

It's a very simple cooling circuit where two lines come into feed the cylinder head and exit through the exhaust manifold. Then the bottom of the head pipe gets fed with warm water, and then dumped into the stinger inlet with the excess water going overboard. There will probably be no need for cooling restrictors because it only uses one overboard bypass fitting.

Here's a diagram of the cooling line routing.
.

Interesting concept, but I would be concerned with possible cold siezer with this set up as you are throwing alot of cool water at the cylender. The preasure in the pipe would be much greater though. I would be afraid to even try that set up.

 

[sjetrider]

By routing the hose or hoses to the bottom of the exhaust manifold the water always drains back out of the pump when the ski is out of the water.

With the top feed setup water always stays in the engine since it has to exit out the top of the head pipe and enter through the top of the head.

This should also help eliminate some corrosion because there is less chance of salt buildup before flushing the ski.

I'm going to try this setup this summer on a spare 62T/61X engine with 210psi compression on pump gas just to prove my theory, that the domes need to be cooled first and the exhaust needs to be even hotter. :firedevil:

I thought race gas burned faster & cooler then 93 octane? I never knew cylender heat cause deto of cylenders just siezing as will too cold?????

 

[dbrutherford]

My $0.02 If you run dual cooling, you are essentially increasing the pressure of your system. So you will need to adjust your screws accordingly or else you will be forcing more water through the screws.

I was once told that a lot of seizures came on race engines because you go racing to a turn WOT. Then you let off the gas which causes a drop in the cooling water system pressure. Then when you get back on the gas WOT coming out of the turn, the engine is hot, there isn't any water pressure, you get a seizure.

I have tried cooling both "dual cooling" setups. These are two seperate systems (one line for pipe only, and one line for engine only) The other setup is to run both lines to the exhaust manifold just as the stock setup is. You simply add pissers to compensate for the additional water.

Now, my question goes back to heat transfer class which I hated in college... Is it better to have the water stay in the cooling passages a little while ot asorb the heat. Or is it better to just flow as much water as possible without giving it any time to asorb heat? I will have to look up the formulas and let you guys know.

 

[crammit442]

My $0.02 If you run dual cooling, you are essentially increasing the pressure of your system. So you will need to adjust your screws accordingly or else you will be forcing more water through the screws.

I was once told that a lot of seizures came on race engines because you go racing to a turn WOT. Then you let off the gas which causes a drop in the cooling water system pressure. Then when you get back on the gas WOT coming out of the turn, the engine is hot, there isn't any water pressure, you get a seizure.

I have tried cooling both "dual cooling" setups. These are two seperate systems (one line for pipe only, and one line for engine only) The other setup is to run both lines to the exhaust manifold just as the stock setup is. You simply add pissers to compensate for the additional water.

Now, my question goes back to heat transfer class which I hated in college... Is it better to have the water stay in the cooling passages a little while ot asorb the heat. Or is it better to just flow as much water as possible without giving it any time to asorb heat? I will have to look up the formulas and let you guys know.

Save yourself the trouble of looking up the formulas. If the goal was heating the water, slowing the flow would be the way to go. Since we're attempting to cool the motor, a constant fresh supply of cold water(faster flow) will always be vastly superior. In the real jetski cooling world, there is no way to move the water too fast to effectively transfer heat. Restrictors(giving the water time to absorb heat) are used to allow the motor to run hotter. To keep the motor from being over cooled. Hope that makes sense.

 

[SuperJETT]

Now, my question goes back to heat transfer class which I hated in college... Is it better to have the water stay in the cooling passages a little while ot asorb the heat. Or is it better to just flow as much water as possible without giving it any time to asorb heat? I will have to look up the formulas and let you guys know.

The answer depends on what you're trying to achieve. Are you trying to heat the water or remove heat from the cylinder/head?

Heat Transfer/Fluid Flow was a fun class in Navy Nuclear Power School. I actually learned it too...

 

[dbrutherford]

If you are heating the water, you are removing heat from the cylinder and head. Energy only transfers from a high potential (high heat) to a lower potential (low heat). It is just the way it works in nature.


I also forgot to mention that I once read an old Dirt Rider MX magazine about the late 80's "works" Honda MX bikes. They had two seperate water pumps and radiators on the bike. This was because they had one cooling system for the head, and one cooling system for the cylinder. The reasoning was because system (head or cylinder) like to be ran cool, and the other ran hot. I just forget which was hot or cold.

 

[crammit442]

If you are heating the water, you are removing heat from the cylinder and head. Energy only transfers from a high potential (high heat) to a lower potential (low heat). It is just the way it works in nature.

If the goal is to heat the water, the approach will be different than if the goal is to cool the motor. Keeping water in the motor longer will be a more efficient way to heat the water. If the goal is to cool the motor,(which it is) moving a fresh supply of cold water through the motor is more efficient.:fing02:

 

[#ZERO]

I thought race gas burned faster & cooler then 93 octane? I never knew cylender heat cause deto of cylenders just siezing as will too cold?????

Detonation occurs when there is excessive heat in the combustion chamber and it causes the fuel mixture to auto ignite. This produces multiple flame fronts within the combustion chamber instead of a single flame kernel. When these multiple flames collide, they do so with explosive force that produces a sudden rise in cylinder pressure that can cause a sand blast appearance around the outer edges of the squish band. If these hot spots could be eliminated, high compression ratios would be possible, running the same octane fuels.

I really don't think that cold seizure would be a problem with these two-stroke engines because of the excessive piston clearance they run. A piston seizure can only occur when something burns or scrapes away the oil film that exists between the piston and the cylinder wall.

 

[ANT]

I thought race gas burned faster & cooler then 93 octane? I never knew cylender heat cause deto of cylenders just siezing as will too cold?????

race gas burns slower, it's more complex, chemically its more to break down.

As far as the cooling thing, it seems like it's pretty simple, why would you want to heat water? are you gonna cook some pasta or something? boil eggs? you wanna get water in and out as fast as you can, it will run cooler that way. the heating water thing would be equivalent to if you were to run single 1/4" cooling line to cool your ski water wouldnt move as fast, it would heat up, and your motor would run hot. a rule of thumb is if you have a head and pipe, go with daul cooling.

you could definetly cold sieze the two-stroke. the cold siezing depends on what kind of pistons your running too, cast or forged. the forged needs more clearance.

 

[dbrutherford]

I think you guys misunderstood me some. If you are cooling the engine, the engine is heating the water. The heat has to go somewhere which is from the heated combustion gases to the engine metal then from the engine metal to the to the water in the engine.

True if you wanted really hot water, you would keep it in the engine longer. My point was more along the lines of which scenario was better.

A lot of water running through the cooling system where the contact time between the water and engine is less.

Or a longer contact time between the water and the engine.

There are many factors that can play into this such as water density (salt or fresh), dual cooling (changes water velocity), water temperature, ect...

That is why I was going to find what formula would be used to calculate the heat transfer energy where I could vary the formula parameters and see which had the biggest effect on the final result.

Speaking of cooking foods on your engine, did anyone watch the Winter X games where teh guy was lookign for a muff pot? Look on espn.com videos for the explanation

 

[madscientist]

the kawie gaskets have smaller holes than the size of the jackets just for the purpose of restriction ie: slowing the flow.

by increasing the volume of the flow it has a similar effect to a low temo thermostat used in automotive performance.

reduces cyinder temps and helps prevent detonation. leaving room to tune out a little more power at the same operating temp or lower than stock.

my 0.02