Hayabusa radiator,fan, and cooling questions

[masterfabr]

I do agree tho with the points about anticavitation * .

[Hambone]

If air locking in your cooling system is the cause of your heating problems try installing a swirl pot on the return water hose from the engine.
When I was racing the CM36 Armstrong two stroke engines we used to use 100% antifeeeze which helped but that got banned because if it was spilled onto the tarmac circuit it was slippy and had caused accidents in the past but as has already been stated you would be better addressing the main cause first.

[opsled]

Hi, I am no expert on Busa's and I'm not sure how many questions I will be answering here but I have worked on many different kinds of 2 and 4 stroke gas and diesel engines and the basic principals of liquid cooling systems are almost all the same. All systems with a water pump and a T-stat need some sort of a bypass to allow some fluid to circulate untill the T-stat opens. Some have an internal bypass in the T-stat housing with a direct link back to the water pump and others will do it through a bypass hose that will go from the engine side of the T-stat to the intake side of the water pump or radiator. Without a bypass system the coolant (loop) is completly closed until the T-stat opens which can cause the pump to cavitate as it has no place to push coolant to untill the T-stat opens. It can also cause (hot spots) on cylinder walls or heads because no coolant would circulate untill the coolant in the water jacket got hot enough to open the T-stat. These bypass loops are usually just large enough to stop both those problems but small enough to allow the engine to warm up properly. So plugging *(deadheading) the bypass system is not a good idea unless you have the thermostat removed and don't plan on putting it back in. Most T-stats will also have a small hole (1/8th" or less) in the flat plate to allow air to pass so there isn't an air pocket trapped under the T-stat after the coolant has been drained and refilled. T-stats don't react to air temp the same way they do to liquid temps and can stay closed to long on initial startup after a refill if they are surrounded by air. I will always drill a small hole in any that don't have one before I install it.
* Most coolant temp sensors for gauges, idiot lights or engine management systems will be located in the hottest spot in the system which is almost always on the engine side of the T-stat. There are certian (hi idle) and other systems that will have the sensor mounted in other locations for various reasons but most will be found by or near the T-stat. If you mount the sensor for a temp gauge or light in the wrong place you won't get a true reading and could be overheating your engine and not know it.
* Electric fan sensors/switches are tipically mounted near the out going side of the radiator to monitor the job the radiator is doing after the coolant has passed through it. In that position if the radiator is doing a good enough job without the fan it won't come on. If the sensor is mounted on the in coming side of the radiator it is not monitoring the radiator performance it is monitoring overall coolant temp of the system which can cause the fan to run more than it really needs to.
* *Radiators can be mounted anywhere they can do the job of cooling as long as all air the can be purged or bled out of them but the rad cap needs to be the highest point in the system to allow any trapped air to get out. *Alot of systems with a low mounted radiator have a seperate manifold for the radiator cap that is mounted in a higher location just for this purpose (very common in snowmobiles).
*Alot of cooling systems will have hills and valleys in the coolant flow and usually will have provisions to bleed the air out of those hills when you are filling the system. When you are building your own system you need to leave yourself a way to bleed off any air from those hills or you could have air in the system for a long time. *
*And finally on gauges. I have some experiance in the sprint car world and at the time alot of people went away from gauges for the driver because of durability reasons and the simple fact that the driver just didn't have the time or ability to monitor them during a race. Alot were going with "go-no-go" systems or what some called a god-damit light. The go-no-go were green lights that would be on when you had oil preassure and a red that would come on when the engine got to hot or some other combination that they preferred. Some just had one big red light (god-damit light) that would come on if any system failure was detected. When the light came on you just said god-damit and headed for the pits. Some kept the gauges but would also add the lights just t help the driver.

[dlisabeth]

Thanks for all of the replies, there is some good info in them. *The information I am most interested in is where everyone is mounting their temp sensors. *I believe two people stated that their fan sensor is located either in the radiator tank near the outlet or in the hose leaving the radiator. *I understand how this would definitely reduce the amount of time the fan is running which is one of my goals. *But wouldn't it also increase the overall temperature of the cooling system which my fan that now runs almost non-stop can hardly control? *Or is the idea to feed the motor coolant which is between 190-200 degrees (or whatever the thermoswitch is designed for) and really not worry about the increased temperature of the coolant as it passes through the motor? *In that case the main concern is cooling the fluid back down to the appropriate temp before it makes its way back in to the motor. *I have a feeling the fan may run just as long but it will probably cycle on and off quite a bit (which I don't mind) with the thermoswitch in this location. * *

Now as far as the location of the temp sensor for the gauge. *It sounds like it should be as near as possible to the thermostat in order to get a reading on the coolant leaving the motor. *Is this correct? *I guess this tells you how hot the coolant entering the radiator is and if the radiator alone can cool it back down to under 200 degrees it will otherwise the fan will kick on to ensure that the coolant being sent back to the motor is cool enough. *

I don't think anyone answered my question in regard to the stock temp sensor. *Is it needed in a sandrail application as a sensor for the ECM or was it only used for the stock bike gauges?

Thanks Again,

Derek

[Rorty]

Originally Posted by dlisabeth\";p=\&quot

I don't think anyone answered my question in regard to the stock temp sensor. *Is it needed in a sandrail application as a sensor for the ECM or was it only used for the stock bike gauges?

I'm pretty sure the bike sensors were only matched to the bike's gauges and not specific to the ECM. In which case, you would want to obtain a sensor to match whatever brand of gauge you're using, but make sure it's the same temp range as the original bike's sensor.

[dlisabeth]

[quote=Rorty\";p=\"36776]

Originally Posted by "dlisabeth\";p=\"36774":1anxtw50

I don't think anyone answered my question in regard to the stock temp sensor. *Is it needed in a sandrail application as a sensor for the ECM or was it only used for the stock bike gauges?

I'm pretty sure the bike sensors were only matched to the bike's gauges and not specific to the ECM. In which case, you would want to obtain a sensor to match whatever brand of gauge you're using, but make sure it's the same temp range as the original bike's sensor.[/quote:1anxtw50]

Thanks Rorty that is what I am hoping. *I already have the new sensor and wanted to install it in the stock location as the Suzuki engineers must have thought it was the best option. *I looked at the wiring diagram for the bike and it shows the sensor as part of the Fuel injection system so I am not sure.

[masterfabr]

The busa ecm uses coolant temp to adjust fuel delivery.You should keep the signal going to it.

[Rorty]

I'm glad someone knows what they're talking about! *

As soon as I posted that I realised the ECU requires the temp.

[opsled]

Originally Posted by dlisabeth\";p=\&quot

Thanks for all of the replies, there is some good info in them. *The information I am most interested in is where everyone is mounting their temp sensors. *I believe two people stated that their fan sensor is located either in the radiator tank near the outlet or in the hose leaving the radiator. *I understand how this would definitely reduce the amount of time the fan is running which is one of my goals. *But wouldn't it also increase the overall temperature of the cooling system which my fan that now runs almost non-stop can hardly control? *Or is the idea to feed the motor coolant which is between 190-200 degrees (or whatever the thermoswitch is designed for) and really not worry about the increased temperature of the coolant as it passes through the motor? *In that case the main concern is cooling the fluid back down to the appropriate temp before it makes its way back in to the motor. *I have a feeling the fan may run just as long but it will probably cycle on and off quite a bit (which I don't mind) with the thermoswitch in this location. * *

Now as far as the location of the temp sensor for the gauge. *It sounds like it should be as near as possible to the thermostat in order to get a reading on the coolant leaving the motor. *Is this correct? *I guess this tells you how hot the coolant entering the radiator is and if the radiator alone can cool it back down to under 200 degrees it will otherwise the fan will kick on to ensure that the coolant being sent back to the motor is cool enough. *

I don't think anyone answered my question in regard to the stock temp sensor. *Is it needed in a sandrail application as a sensor for the ECM or was it only used for the stock bike gauges?

Thanks Again,

Derek

Hi Derek, In a properly designed system the fan switch should be mounted in the out going side of the rad. It really doesn't matter if it is tank or hose mounted as long as it is near the out going side. The fan is there to assist the rad (if needed) in cooling the engine so it needs to monitor rad temp not engine temp. If the rad is to small and can't handle the engine's heat output the fan will be running all the time no matter where the switch is mounted. Factory locations for engine temp sensors should be used whenever possible unless you have really modified the engine or it's stock assessory systems (fuel, ignition, exhaust, cooling). If you have engine management systems (fuel ingection/ignition) that require input from a coolant temp sensor to perform their jobs you should have the proper T-stat installed so they do there jobs as originally designed by the factory. Without a T-stat your engine temps will vary more than designed and the engine managment systems will not perform as well as they should.
* The internal engine temp is what is important to the engine not the temp of the rad. If the rad was sending back coolant to the engine that was 100 degrees cooler it wouldn't matter. The T-stat would close down and restrict the flow enough to compensate. It would only allow enough coolant flow through the engine to keep it at the proper operating temp. *The T-stat is the controller of internal engine temps and the rad is there to provide a means to get rid of excess heat. If the rad is oversized the T-stat can compensate for it but if the rad is undersized and can't provide coolant back to the engine at a temp that is lower than the proper operating temp of the engine it will overheat. You must have a radiator that is capable of getting rid of heat faster than the engine can produce it or you will have problems.
* The fan helps the rad do it's job but it also has limits. You can only push so much air through a rad at one time. That amount depends on the size of the rad and the size of the fan but the temperature of that air is a huge variable in how much good it is doing.
* My opinion is that your problems are being caused by a radiator that is undersized. I have no experiance with a Busa engine but from what you are descibing and what others have said here my opinion would be the same no matter what you were running for an engine.
*My suggestions would be to #1 get a bigger rad (I would rather have one that is oversized for the job), #2 install the proper T-stat for your engine, #3 get your bypass line routed into the in coming side of the rad, #4 make sure your factory engine sensors are in the proper place and hooked up, #5 get a fan that is sized to the rad with it's controler switch mounted on the out going side and # 6 try to find a spot for your temp gauge sensor that is as close to the engine side of the T-stat as possible.
* If you are having trouble finding a spot for your gauge sensor there are other options. I have included a pic of a factory Yamaha snowmobile setup that installs the gauge into the bypass line. It would not be my first choice but it will work.
* Good luck, Phil (opsled)

[Gene]

This is a great thread and I am learning with every post. The picture in Phil's last post was very helpful since it showed the Yamaha sensor and in-line receptacle.

I had not consdered that the T-stat bypass was to prevent water pump cavitation while the engine is beleow T-stat operating range. Makes perfect sense.

It makes perfect sense to install a sensor on the outbound side of the radiator to monitor coolant temp that controls the fan for additional cooling.

It makes perfect sense to install a temp gauge sensor as close as possible to the T-stat/cylinder head so you know what coolant temp is after it has performed work.

I have a Haybausa manual on CD that I can't find and a printed copy that is difficult to read because the pictures are to small and I'm aging. I see from the manual that the Engine Coolant Temperature sensor is located on/in/near the T-stat housing so it monitors head coolant temp. *If anyone has a clear picture of where the sensor goes it would help.

I don't remember how mine was setup but I have not found a port/plug/receptacle similar to what is shown in Phil's Yamaha picture in the previous post. I suspect the sensor was just hanging around in my wire loom without a home. The Hayabusa gauge cluster has the ususal automotive display Normal to Hot so it is little more than a God-damit-light. I'm installing a gauge with numbers.

On the stock Hayabusa where is the sensor that controls the fan?