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You should listen to me. No, seriously, listen to
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It's more than the fan blade hitting the radiator. It could also be that the fan motor bearing is failing. Suggest that you see how fast it turns with the engine off. Unfortunately I don't have an RPM spec.
 

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Dreaming of buttsecks for years...
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I've seen a few threads now saying "flashed so fan kicks on earlier" or something to that effect. Looking at a few wiring diagrams, the ECU has nothing to do with the fan.... it's a thermal switch. So I'm curious what bike we're talking about here???
 

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Captain Obvious ... because obviously it’s obvious
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Discussion Starter #23
I've seen a few threads now saying "flashed so fan kicks on earlier" or something to that effect. Looking at a few wiring diagrams, the ECU has nothing to do with the fan.... it's a thermal switch. So I'm curious what bike we're talking about here???
This is a 2006 GSXR 1000 or a 250
 

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You should listen to me. No, seriously, listen to
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^On K5 & later the thermal switch is gone and the ECM controls a relay that, in turn, controls the fan.
 

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I know things... A lot of things.
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By the way, have you checked the area of the radiator, that's in front of the fan for any signs of blockage or deterioration due to impacts, etc.?

And incidentally, since we're on the subject, why would one wish to lower the fan-on temperature anyway? Are there any more objective reasons to do this, than "I don't like my engine to get hot"?
 

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Dreaming of buttsecks for years...
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^On K5 & later the thermal switch is gone and the ECM controls a relay that, in turn, controls the fan.
Thanks. Wasn't aware of that. Most of my knowledge is dedicated to the middleweight bikes.
 

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You should listen to me. No, seriously, listen to
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"And incidentally, since we're on the subject, why would one wish to lower the fan-on temperature anyway? Are there any more objective reasons to do this, than "I don't like my engine to get hot"?"

That's the main argument, something along the lines of it's unnerving to see the temp climb from a stable 170°-175° to about 220° at a long stop light. A 45°-50° rise sounds like differential thermal expansion could start affecting clearances or the relative position of things, i.e. an aluminum block and steel crankcase & cams. You're still below the boiling point but 220° is getting up to where there will be some pressure buildup in the cooling system, with attendant stress on hoses. A downside is that these engines tend to accumulate condensate in the crankcase and a run up to 220° will get rid of it.


"Most of my knowledge is dedicated to the middleweight bikes."

As far as I know, 600/750 changed to an ECM controlled fan in K6.
 

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Captain Obvious ... because obviously it’s obvious
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Discussion Starter #28
By the way, have you checked the area of the radiator, that's in front of the fan for any signs of blockage or deterioration due to impacts, etc.?

And incidentally, since we're on the subject, why would one wish to lower the fan-on temperature anyway? Are there any more objective reasons to do this, than "I don't like my engine to get hot"?
Because sitting on a bike that's 220 degrees in 100+ degree weather, while in full gear, is beyond uncomfortable. And it gets there REALLY fast when it's that hot and you're creeping along in traffic or are waiting at a light. I wanted a 200 degree kick-on, but I'm not about to spend another $10 to ship the ECU and hope they don't fuck it up like last time.
 

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Captain Obvious ... because obviously it’s obvious
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Discussion Starter #29
By the way, have you checked the area of the radiator, that's in front of the fan for any signs of blockage or deterioration due to impacts, etc.?

And incidentally, since we're on the subject, why would one wish to lower the fan-on temperature anyway? Are there any more objective reasons to do this, than "I don't like my engine to get hot"?
Yup, looks to be nearly perfect. No crap blocking it, fins are all in good shape. I'll need to get a flashlight in there to verify that nothing got packed in around the fan area.
 

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Reluctant GDC camper.....
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Because sitting on a bike that's 220 degrees in 100+ degree weather, while in full gear, is beyond uncomfortable. And it gets there REALLY fast when it's that hot and you're creeping along in traffic or are waiting at a light. I wanted a 200 degree kick-on, but I'm not about to spend another $10 to ship the ECU and hope they don't fuck it up like last time.
Thats funny,I had my ECU flashed by Danos Perfomance and my fan was supposed to be 205/195,Its actually 201/195 with it sometimes coming on at 197 etc..Dunno why this is but it's a hell of alot better than the 220 that it comes on stock.
 

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I know things... A lot of things.
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Because sitting on a bike that's 220 degrees in 100+ degree weather, while in full gear, is beyond uncomfortable. And it gets there REALLY fast when it's that hot and you're creeping along in traffic or are waiting at a light. I wanted a 200 degree kick-on, but I'm not about to spend another $10 to ship the ECU and hope they don't fuck it up like last time.
I see. I wouldn't have expected that to make things any better, as the bike is prevented from getting any hotter, by having all that heat blown on your legs, so that you end up feeling it anyway. I'm probably missing something though; perhaps dealing with more air of lower temperature is subjectively more comfortable than less air of higher temperature.

That's the main argument, something along the lines of it's unnerving to see the temp climb from a stable 170°-175° to about 220° at a long stop light. A 45°-50° rise sounds like differential thermal expansion could start affecting clearances or the relative position of things, i.e. an aluminum block and steel crankcase & cams. You're still below the boiling point but 220° is getting up to where there will be some pressure buildup in the cooling system, with attendant stress on hoses. A downside is that these engines tend to accumulate condensate in the crankcase and a run up to 220° will get rid of it.
Yes, I have noticed the effect of condensate accumulation in the crankcase lately. After switching jobs, I'm now only 5-6km away, so the engine barely warms up. Besides seriously deteriorating my fuel efficiency, the oil covering the inspection port and, on colder days, the whole right-hand engine cover started getting white from condensation. You could see the oil behind it had its usual color and it would clear up after a short ride, but it would recondense after sitting overnight. After taking a couple of 350km trips, any trace of white oil/water mix is now gone.

I've been wondering though: what's the point of having a pressurized cooling system, if you're going to set the thermostat's set-point to well below 100°C? Perhaps the point is to prevent localized boiling near the hottest areas around the combustion chamber, which might be possible even when the average coolant temperature is well below the boiling point. Otherwise one could just set the fan-on temperature to below 95° or so and dispense with the complexity of pressurization.
 

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Dreaming of buttsecks for years...
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Prevents flash boiling of the coolant in hot spots and after shutdown (heat soak with no circulation).

I don't know why everyone keeps trying to "fix" cooling system technology that's been in use for nearly 100 years. Suzuki engineers think 220f-210f is perfectly fine, and I'm certain they're smarter than any of us.
 

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You should listen to me. No, seriously, listen to
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Don't know for sure but I suspect that the 220° level is related to lowering HC emissions. It also raises NOX but that wasn't an issue until the regulations tightened around 2007, and they addressed it with a cat converter.
 

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Dreaming of buttsecks for years...
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But the bike will only get to that temp when you're sitting still in traffic, so what's the problem again?
 

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Yes, I would have thought that, if coolant temperature was selected based on emissions-related considerations, it should apply more to the target value set via the thermostat and secondarily to the maximum value, controlled via the fan, unless there's some reason to assume that most pollutant emissions take place under conditions that promote engine overheating. For that matter, I can't really understand why one would design an engine and cooling system to be able to sustain elevated temperatures of 105°C without problem and then proceed to set the desired operating temperature much lower. From the aspect of efficiency, a higher temperature would only be beneficial, so perhaps this is (also) related to emissions control.
 

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Dreaming of buttsecks for years...
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Because a cooling system capable of maintaining the thermostat temperature would be too large and heavy for the intended application.
 

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I'm not sure what you mean by that; perhaps you misunderstood me. Since the bike is able to maintain the temperature below 105°C, both when standing still and, much easier, when moving at any reasonable speed, it should be feasible to set the thermostat to maintain that temperature all the time (or a little lower, if a margin of safety is needed). This would be beneficial in terms of efficiency, as far as I can tell, so why is the working temperature set 25-30°C lower?
 

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Dreaming of buttsecks for years...
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I don't think you understand how the thermostat works. It's basically a flow resistor. It's closed until a certain temperature, then it opens. The opening temperature is the beginning of the optimal range for the bike. Once it opens, you're just at the mercy of the radiator's capacity to expel heat. Which is why when you stop, the heat climbs until the fan is on.
 

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I don't think you understand how the thermostat works. It's basically a flow resistor. It's closed until a certain temperature, then it opens. The opening temperature is the beginning of the optimal range for the bike. Once it opens, you're just at the mercy of the radiator's capacity to expel heat. Which is why when you stop, the heat climbs until the fan is on.
Yes, that is my understanding of the thermostat's operation. What I wonder is why the optimal range is assumed to be at 85°C and not at, say, 95°C or even 100°C? From a standpoint of efficiency, it would be beneficial, as far as I can see and the engine is evidently designed to handle it (although perhaps only for shorter amounts of time, not permanently). Emissions considerations are theoretically a possibility, but I find it unlikely, at least for the pre-catalytic converter era bikes.
 

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Dreaming of buttsecks for years...
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I'm sure it's not assumed. Suzuki engineers know their shit. Also, the coolant temperature it below the actual temperature of the engine. These bikes even have oil coolers to help pull heat out. Also, you have to think about engine damage. What's the point where the manual says kill it? 235/112?
 
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