COOLANT TEMPERATURE

[maximNikenGT]

Had to pull out my book on Engineering Fundamentals of the Internal Combustion Engine by Willard Pulkrabek from engineering school to refresh my knowledge of heat transfer in engines. The section on Engine Warmup states:

"As a cold engine heats up to steady-state temperature, thermal expansion occurs in all components. The magnitude of this expansion will be different for each component, depending on its temperature and the material from which it is made. Engine bore limits the thermal expansion of the pistons, and at operating temperatures of a newer engine there can be very high resulting forces between the piston rings and skirt and the walls of the cylinder. This causes high viscous heating in the oil film on the cylinder walls during engine operation.

Figure 10-3 shows how the temperature of various automobile components increases with time after a cold engine is started. In cold weather, the startup time to reach steady-state conditions can be as high as 20-30 mins. Some parts of the automobile reach steady-state much sooner than this, but some do not. Fairly normal operating conditions may be experienced within a few minutes, but it can take as long as an hour to reach optimum fuel consumption rates. Engines are built to operate best at steady-state conditions, and full power and optimum fuel economy may not be realized until this is reached. It would be poor practice to take off with an airplane, when full power is needed, before the engine is fully warmed up. This is not as critical with an automobile. Driving before total engine warmup causes some loss of power and fuel economy, but if there is engine failure, the distance to fall is much less than in an airplane. A large percent of automobile use is for short trips with engines that are not fully warmed up. In Chapter 9, it was found that this was a also a major cause of air pollution."

 

Key point here is that any engine has a lot of factors that go into determining how long it takes to reach a steady-state (regular) operating temperature (heat losses from conduction, convection and radiation all play a role). 

With motorcycle engines, while smaller than an automotive engine, may take longer to heat up to steady-state engine temperatures if it's colder outside due to convection heat losses being more pronounced since typically the engine is more exposed to the cold air vs. a more typically enclosed automobile engine. 

To your question of whether the thermostat is operating correctly, had to reference what the point of the thermostat is in an internal combustion water cooled engine. Section 10-8 Liquid Cooled Engines states:

"To keep the coolant fluid temperature from dropping below some minimum value, and thus keeping the engine operating at a higher temperature and efficiency, a thermostat is installed in the coolant loop, usually at the engine flow entrance. A thermostat is a thermally activated go-no go valve. When the thermostat is cold, it is closed and allows no fluid flow through the main circulation channel. As the engine warms up, the thermostat also warms up, and thermal expansion opens the flow passage and allows coolant recirculation. The higher the temperature, the greater the flow passage opening, with the greater resulting coolant flow. The coolant temperature is , therefore, controlled fairly accurately by the opening and closing of the thermostat. Thermostats are manufactured for different coolant temperatures, depending on engine use and climate conditions. They generally come in ratings from cold (140 degrees F / 60 C) to hot (240 degrees F / 116 C)." 

Key takeaway here is that your thermostat is keeping your engine temperature at optimum range of operation as set by the computer based upon ambient conditions even though the thermostat may not be opened and the cooling fans not kicking in. Yamaha engineers have tested the engine in a wide range of ambient temperatures and adjusted the engine cooling software/hardware to trigger once its thresholds are breached across a variety of inputs/sensors. If there's one thing they taught us in mechanical engineering school, it was the study of heat transfer. And you can be sure that Yamaha Motors has some of the top heat transfer specialists in the industry testing and programming its engines. If your thermostat failed, typically you would know because your engine temperature would be overheating a lot and your check engine lights would trigger.  

 

 

[skipperT]

3 hours ago, maximNikenGT said:

Had to pull out my book on Engineering Fundamentals of the Internal Combustion Engine by Willard Pulkrabek from engineering school to refresh my knowledge of heat transfer in engines. The section on Engine Warmup states:

"As a cold engine heats up to steady-state temperature, thermal expansion occurs in all components. The magnitude of this expansion will be different for each component, depending on its temperature and the material from which it is made. Engine bore limits the thermal expansion of the pistons, and at operating temperatures of a newer engine there can be very high resulting forces between the piston rings and skirt and the walls of the cylinder. This causes high viscous heating in the oil film on the cylinder walls during engine operation.

Figure 10-3 shows how the temperature of various automobile components increases with time after a cold engine is started. In cold weather, the startup time to reach steady-state conditions can be as high as 20-30 mins. Some parts of the automobile reach steady-state much sooner than this, but some do not. Fairly normal operating conditions may be experienced within a few minutes, but it can take as long as an hour to reach optimum fuel consumption rates. Engines are built to operate best at steady-state conditions, and full power and optimum fuel economy may not be realized until this is reached. It would be poor practice to take off with an airplane, when full power is needed, before the engine is fully warmed up. This is not as critical with an automobile. Driving before total engine warmup causes some loss of power and fuel economy, but if there is engine failure, the distance to fall is much less than in an airplane. A large percent of automobile use is for short trips with engines that are not fully warmed up. In Chapter 9, it was found that this was a also a major cause of air pollution."

 

Key point here is that any engine has a lot of factors that go into determining how long it takes to reach a steady-state (regular) operating temperature (heat losses from conduction, convection and radiation all play a role). 

With motorcycle engines, while smaller than an automotive engine, may take longer to heat up to steady-state engine temperatures if it's colder outside due to convection heat losses being more pronounced since typically the engine is more exposed to the cold air vs. a more typically enclosed automobile engine. 

To your question of whether the thermostat is operating correctly, had to reference what the point of the thermostat is in an internal combustion water cooled engine. Section 10-8 Liquid Cooled Engines states:

"To keep the coolant fluid temperature from dropping below some minimum value, and thus keeping the engine operating at a higher temperature and efficiency, a thermostat is installed in the coolant loop, usually at the engine flow entrance. A thermostat is a thermally activated go-no go valve. When the thermostat is cold, it is closed and allows no fluid flow through the main circulation channel. As the engine warms up, the thermostat also warms up, and thermal expansion opens the flow passage and allows coolant recirculation. The higher the temperature, the greater the flow passage opening, with the greater resulting coolant flow. The coolant temperature is , therefore, controlled fairly accurately by the opening and closing of the thermostat. Thermostats are manufactured for different coolant temperatures, depending on engine use and climate conditions. They generally come in ratings from cold (140 degrees F / 60 C) to hot (240 degrees F / 116 C)." 

Key takeaway here is that your thermostat is keeping your engine temperature at optimum range of operation as set by the computer based upon ambient conditions even though the thermostat may not be opened and the cooling fans not kicking in. Yamaha engineers have tested the engine in a wide range of ambient temperatures and adjusted the engine cooling software/hardware to trigger once its thresholds are breached across a variety of inputs/sensors. If there's one thing they taught us in mechanical engineering school, it was the study of heat transfer. And you can be sure that Yamaha Motors has some of the top heat transfer specialists in the industry testing and programming its engines. If your thermostat failed, typically you would know because your engine temperature would be overheating a lot and your check engine lights would trigger.  

 

 

Interesting quote, @maximNikenGT  how old is that text?

Because there are 2 things that I take issue with: 

-modern thermostats DO have a position where they are partially open and not fully open or closed. Plus, bleed holes which allow slight coolant flow  

You can remove a T-stat and boil it in coolant or water and observe the mechanical opening as I alluded to earlier in my other post.  I guess a “go/no go situation” could be argued to exist where it’s fully closed and not open, but the opening begins at a fairly low temp.

my Armchair guess is that’s why a Tracer engine can read a cool 167 at highway speeds with good airflow @Jasperthedog and also gets as high as it does before fan operation. Maybe that partly answers your question, I dunno  

-modern engines are also brought to temp as fast as possible because of emissions targets. I don’t agree with the 30 minute requirement to reach operating temp, as it is wasteful on fuel and worsens emissions. I would think that today’s engineers have thrown that number out the window during design, choosing materials and fueling for fast warm-up and going to close-loop mode ASAP while idling.

FWIW the Tracer goes closed-loop as soon as the water temp changes from  Low to an actual number. (I have documents from Yamaha defining this…)

Anyway, just some coffee-sipping AM thoughts  

-S

[PhotoAl]

Sounds like normal operation to me.  On my 2020 Tracer 900GT only one time have i notice the temperature climbing a bit worryingly.  It was a hot day - 90sF and I was going uphill on a winding road with slippery tar snakes.  Never got too hot or turned the fans on but was getting a bit close for comfort.  Then I turned downhill and everything was good.  Climbing back out of the valley or canyon I was concerned but had stopped one enough for it to be cool so the temperature never got up.  I would not worry about it.  

[Jasperthedog]

So, as promised, I've done a bit of research.

1.) These engines should all run ABOVE 80C.

2.) The MT09 thermostat housing from 2021 owards seems to be splittable and the t'stat can be replaced (cost £7.95 as opposed to +£50).

3.) On removal the original 'stat 'rattled'. On investigation it can clearly e seen that the 'stat is loose in the housing, allowing water to bypass the control unit. Hence the cool running, with all that entails.

4.) The new Yamaha sourced 'stat in it's Yamaha box from a main dealer cost +£50, also rattled, was loose in it's housing and was just as useless.

With a German sourced MT09 'stat Part No. B7N-1241000 the bike now runs at a steady 80C and is slower to run up the temperature range as the radiator runs cool, giving a pool of cool water to blend in as the 'stat opens fully by 95C.

The splittable housing will also allow those who use the bike as a daily runner in cold climates to fit a 88C 'stat.

As I said in an earlier post, Yamaha have a duff supplier and have not checked the product.

 

 

 

[Jasperthedog]

The schematic cooling sytem shown above would result in the engine overheating and blow out gaskets, hoses and radiator in short order.

1.)The thermostat is NEVER on the 'cold' side of the radiator, i.e., the bottom, as it would never get hot as without it opening there would be zero flow past the wax bulb, but the cylinder head and top of the rad would be boiling. And

2). the 'stat bulb is shown on the 'cold' side of the unit and again will never get any heat.

BTW the little jigger in most 'stats is nothing to do with bypass flow, it's there to allow air to pass the closed stat when filling.

 

[skipperT]

On 7/11/2023 at 9:09 AM, Jasperthedog said:

So, as promised, I've done a bit of research.

1.) These engines should all run ABOVE 80C.

2.) The MT09 thermostat housing from 2021 owards seems to be splittable and the t'stat can be replaced (cost £7.95 as opposed to +£50).

3.) On removal the original 'stat 'rattled'. On investigation it can clearly e seen that the 'stat is loose in the housing, allowing water to bypass the control unit. Hence the cool running, with all that entails.

4.) The new Yamaha sourced 'stat in it's Yamaha box from a main dealer cost +£50, also rattled, was loose in it's housing and was just as useless.

With a German sourced MT09 'stat Part No. B7N-1241000 the bike now runs at a steady 80C and is slower to run up the temperature range as the radiator runs cool, giving a pool of cool water to blend in as the 'stat opens fully by 95C.

The splittable housing will also allow those who use the bike as a daily runner in cold climates to fit a 88C 'stat.

As I said in an earlier post, Yamaha have a duff supplier and have not checked the product.

 

 

 

Re: #3, I don’t think that you can make that assumption (also your conclusion about a “duff supplier”) unless you installed the Yammy T-stat  and observed it working differently than the German sourced product you installed and are now operating. 
my less you operated the bike with both parts, that wasn’t clear to me. Plus some gaskets swell under heat when being tightened up in their respective installation positional the “play” that you felt may have been situation normal, so to speak.  
 

Glad it’s fixed, I just disagree with some of your speculations. Whatevs…

-Skip

[Jasperthedog]

Skip,

The standard Niken t'stat is a sealed unit. There are no gaskets, no seals. The stat inside the housing rattles about and fails to seat thus allowing coolant to pass, irrespective of temperature. Both units, original and new had the same fault. Part number B7N-12410 is perfectly formed and perfectly sealed with zero movement of the stat. Until the correct operating temperature is reached no coolant passes the stat to the radiator. This is how they are supposed to work.

To have had one faulty stat is just how it goes, to have two from the manufacturer with the same fault and, from the replies on the thread, other people reporting low running temperatures points to a faulty supply chain.

It would not be the first time that a manufacturer supplied poor and faulty parts, Yamaha are not perfect.

Perhaps somebody else with a low temp running bike would like to try to get Yamaha to tell them the correct running temperature for this engine and explain why, with a specified stat opening temp of 84C, their bike runs at an indicated 66C.

I can confirm that with a correctly operating stat, stamped/calibrated at 82C, the bike runs at an indicated 80C on a cool (16C) day.

 

[Jasperthedog]

Just a bit of an update for those interested....

The two faulty thermostats were binned and the german spec unit fitted with an 88C  stat. The result is a bike that runs at the manufacturer's specified temerature ~86C and the fans come on later as the thermostat now opens fully. The engine immediately felt better, but far from perfect so the aid of BHP Power  was saught for a remap. This is done over the net after they sent down the controller. I loaded my map into the device and emailed it to BHP who sent back a map designed for a MT09 with an after-market, less restrictive exhaust. Qal, Bossman of BHP, assured me that it may not be perfectly matched, 'but would be lightyears better' than what I had. Oh,boy! Was he right!!

The difference was immediate and a huge improvement. The bike now warms up quickly, runs without any stutter and delivers proper mid-range power and full on top end.

I reset the data and noted that over the 7500 miles to date the consumption had averaged out at 48mpg. As it was three owners down the line , I have no knowledge of how it has been ridden. But since it had the original tyres (2019 date) only about half used, I'm guessing that it was not ragged.  I have now done 500 miles and using the full range available from the engine the average is 52mpg. I regard this as a solid result. The bike now runs as it was designed to do and is a pleasure to ride.

I'm just about to take it to Croatia, a round trip, avoiding all motorways, of around 2500 miles.

[skipperT]

Glad it’s sorted. 
-skip