TWIN TURBO
Expert
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Your temperature gauge is merely giving you the average water temperature of the engine, some places in the engine are hotter than indicated.
Yamaha did a great job engineering/updating the Apex cooling system. The RX1 system is adequate for a stock engine but adding turbo’s and superchargers changes the cooling requirements.
For those of you who haven’t taken a good look at the Apex/RX1 cooling systems, we need to review just how water flows through the system. If we start at the water pump, water is pushed out through a gold plated pipe, which also has a small tee supplying water to the oil cooler, into a large rubber hose around to the rear of the engine under the exhaust pipes to what I call a water manifold, Yamaha calls it a joint. When water enters the manifold, the water flow is currently favoring the right side, or mag side of the block because of the velocity it has entering the manifold, thus flowing more cooling around what would be cylinders 3 and 4. Most of the water, once in the block, then flows around to the intake side of the engine through the internal block cavity then up into the head through holes in the head gasket. It then exits the head through 2 outlets between the number 1 & 2 and 3 & 4 spark plugs into another gold plated pipe on top of the valve cover and flows over to the bottom cavity of the thermostat housing. When the engine is cold, the thermostat is closed and water then moves out the bottom of the housing into another large black rubber hose, the bypass, down to the underneath of the engine through the frame side and into a tee connected to the front heat exchanger. Here is where some I have talked to get confused. Some think water changes direction of flow at this point, it does not. When engine is in bypass, cold, water continues through the tee into a gold plated steal pipe that makes a 90 degree turn into a rubber 90 and into the pump. The beauty of this system is the volume of water flowing through the engine never changes in order to keep the engine at a constant temperature, no hot spots. This is extremely important. After engine warms to about 165 degrees, the thermostat begins to open. As it opens, some water flows to the top side of the thermostat housing and into the plastic water tank where the pressure cap is located and then on to the right side heat exchanger. Water flows back to a crossover pipe, or on some models a rear heat exchanger, into the left side exchanger and then forward into a large rubber hose, under the clutches, that turns 90 degree into a fitting in the left side of the front heat exchanger. The water flows through the front exchanger to the right side of it to the TEE we mentioned earlier where it joins the bypass system and blends cold water in with bypass water depending on just how far the thermostat opened. If the temperature of the water leaving the top of the engine is over 180 degree’s the thermostat will have opened far enough to block the bypass hose, the large hose exiting the bottom of the thermostat housing, thus directing all the water to follow the path to the heat exchangers and around the system. At this time only water leaving the front heat exchanger will feed water to the TEE and on to the water pump. There are also some small diameter hoses, one on the right top of the front heat exchanger and another under the carbs on the block coming from the water pump. They are simply air bleeds so as not to trap air in their respective locations. One other small hose returns back to the water pump from the carbs that keeps them from freezing water vapor and building in the venturi’s. This hose comes from a small tee in the large gold steal pipe coming out of the top of the head.
I hope I haven’t confused anyone but if you follow the path you will see what I’m talking about. Under no circumstances should you remove the thermostat. It will destroy how the system functions. The majority of the water will take the path of least resistance and flow through the bypass most likely overheating the engine. I’ve found that these 4 strokes like some heat anyway. A temperature of 175 degrees is not too hot. Don’t confuse them with 2 strokes that like colder temps.
I have spent many hours of dyno testing and watching temperatures to find that the water stays hotter on the exhaust side of the engine with the current Yamaha head gasket. I’ve designed a head gasket that will direct the flow of water coming in the block, at the rear of the engine, to the head so as to move more water into the hotter sections of the head where it is much needed. By doing this you can keep the temperatures more even and remove more heat so as not to create hot spots in the combustion chamber, which I believe lead to pre-ignition with detonation to soon follow. Water temps exiting the head will actually increase which is a good thing, you are removing more heat.
If anyone has any questions, or interested in my update kit, PM me. Best $129.00 you can spend on your project. Your comments are always welcomed.
Greg Santry
Yamaha did a great job engineering/updating the Apex cooling system. The RX1 system is adequate for a stock engine but adding turbo’s and superchargers changes the cooling requirements.
For those of you who haven’t taken a good look at the Apex/RX1 cooling systems, we need to review just how water flows through the system. If we start at the water pump, water is pushed out through a gold plated pipe, which also has a small tee supplying water to the oil cooler, into a large rubber hose around to the rear of the engine under the exhaust pipes to what I call a water manifold, Yamaha calls it a joint. When water enters the manifold, the water flow is currently favoring the right side, or mag side of the block because of the velocity it has entering the manifold, thus flowing more cooling around what would be cylinders 3 and 4. Most of the water, once in the block, then flows around to the intake side of the engine through the internal block cavity then up into the head through holes in the head gasket. It then exits the head through 2 outlets between the number 1 & 2 and 3 & 4 spark plugs into another gold plated pipe on top of the valve cover and flows over to the bottom cavity of the thermostat housing. When the engine is cold, the thermostat is closed and water then moves out the bottom of the housing into another large black rubber hose, the bypass, down to the underneath of the engine through the frame side and into a tee connected to the front heat exchanger. Here is where some I have talked to get confused. Some think water changes direction of flow at this point, it does not. When engine is in bypass, cold, water continues through the tee into a gold plated steal pipe that makes a 90 degree turn into a rubber 90 and into the pump. The beauty of this system is the volume of water flowing through the engine never changes in order to keep the engine at a constant temperature, no hot spots. This is extremely important. After engine warms to about 165 degrees, the thermostat begins to open. As it opens, some water flows to the top side of the thermostat housing and into the plastic water tank where the pressure cap is located and then on to the right side heat exchanger. Water flows back to a crossover pipe, or on some models a rear heat exchanger, into the left side exchanger and then forward into a large rubber hose, under the clutches, that turns 90 degree into a fitting in the left side of the front heat exchanger. The water flows through the front exchanger to the right side of it to the TEE we mentioned earlier where it joins the bypass system and blends cold water in with bypass water depending on just how far the thermostat opened. If the temperature of the water leaving the top of the engine is over 180 degree’s the thermostat will have opened far enough to block the bypass hose, the large hose exiting the bottom of the thermostat housing, thus directing all the water to follow the path to the heat exchangers and around the system. At this time only water leaving the front heat exchanger will feed water to the TEE and on to the water pump. There are also some small diameter hoses, one on the right top of the front heat exchanger and another under the carbs on the block coming from the water pump. They are simply air bleeds so as not to trap air in their respective locations. One other small hose returns back to the water pump from the carbs that keeps them from freezing water vapor and building in the venturi’s. This hose comes from a small tee in the large gold steal pipe coming out of the top of the head.
I hope I haven’t confused anyone but if you follow the path you will see what I’m talking about. Under no circumstances should you remove the thermostat. It will destroy how the system functions. The majority of the water will take the path of least resistance and flow through the bypass most likely overheating the engine. I’ve found that these 4 strokes like some heat anyway. A temperature of 175 degrees is not too hot. Don’t confuse them with 2 strokes that like colder temps.
I have spent many hours of dyno testing and watching temperatures to find that the water stays hotter on the exhaust side of the engine with the current Yamaha head gasket. I’ve designed a head gasket that will direct the flow of water coming in the block, at the rear of the engine, to the head so as to move more water into the hotter sections of the head where it is much needed. By doing this you can keep the temperatures more even and remove more heat so as not to create hot spots in the combustion chamber, which I believe lead to pre-ignition with detonation to soon follow. Water temps exiting the head will actually increase which is a good thing, you are removing more heat.
If anyone has any questions, or interested in my update kit, PM me. Best $129.00 you can spend on your project. Your comments are always welcomed.
Greg Santry
rxrider
Jan-Ove Pedersen
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- 2014 Phazer XTX, 2013 Phazer RTX, 2008 Apex RTX, 2007 Warrior, 2006 Attak
Thank you for investigating the coolant system of our sleds 
I take it the upgrade is only needed on the RX-1 engine. Is it needed on the Apex engine?
I take it the upgrade is only needed on the RX-1 engine. Is it needed on the Apex engine?
TWIN TURBO
Expert
- Joined
- Aug 30, 2005
- Messages
- 317
- Reaction score
- 2
- Points
- 721
- Location
- Chicago IL.
- Website
- www.powerbygns.com
Sorry, I failed to mention,
The Apex cooling system has most of what I'm suggesting, not enough change to justify modifications. I've checked both, the Apex is much better than the RX1.
All should be aware YOU CANNOT USE A RX! HEAD GASKET ON AN APEX AND YOU CANNOT USE A APEX HEAD GASKET ON AN RX1. The head castings are different and the gaskets don't interchange !!!!!!!!!!
The Apex cooling system has most of what I'm suggesting, not enough change to justify modifications. I've checked both, the Apex is much better than the RX1.
All should be aware YOU CANNOT USE A RX! HEAD GASKET ON AN APEX AND YOU CANNOT USE A APEX HEAD GASKET ON AN RX1. The head castings are different and the gaskets don't interchange !!!!!!!!!!
