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Thermostat question.

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Woofentino Pugrossi

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Thermostat question.
« on: April 11, 2004, 01:29:05 pm »
Has anyone run their bike without the thermostat in it? I was wondering if that would bother it and help it stay a tick cooler.
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Rob
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Eric Kelcher

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Re: Thermostat question.
« Reply #1 on: April 12, 2004, 11:39:05 am »
Well there are two areas of thought one that the water will flow faster and then give more cooling by passing over radiator fins and head faster.
The other, that I subscribe to, is that without the resistance and backpressure that the water pump can cavitate at high RPM. Also water has a better transfer of heat when the differnce in temps is greater and by holding water from circualting real fast it goes to greater temp extreme (cooler in radiator, hotter in engine). What you are really trying to remove is BTU not degrees of temp but if you have a 70* day and engine is at 220* then you move water fast through motor it may only rise to 180* water temp then you have a 110 * temp difference whereas slower moving water rises to 210 you now have a 140 differnece. Now the water when it gets to radiator on fast moving nonthermostat bike the water is cooled to 150* on the thermo bike it is cooled 160* well the non-thermo bike runs cooler! well not really the thermo bike removed more BTU (the change in water temp was greater 50* vs 30*) so the bike is going to overheat as the metal just cannot transfer the heat to water fast enough when it passes by so quickly. The greater the temp difference the faster the transfer of BTUs from one medium to the other.  So without a thermostat you may see lower temps as the water is not being raised as high temps as it circulates through motor initially or when not under a load (IE racing)but it also returns to motor with hotter water and the temp keeps rising, this can be offset by an oversize radiator (thus slowing down the flow in cooling section) or by greater temp diff by more air flow over radiator or cooler day, but you still do not have the chance for as much heat to transferred to water from the motor. Wheras the thermostat equipped bike will raise to a temp and then stay there. Now granted there are some motors that imporoved by removing the thermostat that had design flows (genrally older motors)or flow restriction from buildup or other issues but in general the engineers that built these bikes know the heat output and design radiators and water pumps to work together to maintain proper operating temps.

Now you can remove the thermostat just to eliminate a item that could fail but then you should gut the internals or install a washer so you maintain the flow restriction. When doing this you will need to use duct tape on radiator to maintain proper engine temps.
« Last Edit: April 12, 2004, 03:11:19 pm by Eric_Kelcher »
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Eric Kelcher
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Eric Kelcher

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Re: Thermostat question.
« Reply #2 on: April 12, 2004, 11:43:31 am »
NOTE
Most everything I have mentioned is theory and each individual bike can vary but the designers of bikes in quest for lighter weight have been edging closer and closer to having the minimum cooling needed for a bike to reduce weight (less water and less metal with smaller radiators)
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Eric Kelcher
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dwilson

Re: Thermostat question.
« Reply #3 on: April 12, 2004, 11:58:15 am »
I'd leave it in.  Like Eric said, you need the proper rate of flow, too fast and the water can't draw the heat out of the metal.  On BMW cars, the thermostat is also used to route the water into the jacket.  You'd also have the problem that the motor would take a long time to get up to operating temperature if you took it out...  Besides, how much does a thermostat weigh? (an ounce or two...)
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duc995@aol.com

Re: Thermostat question.
« Reply #4 on: April 16, 2004, 08:31:20 am »
I race an APrilia RS 250 and have removed the thermostat.  However there is still a restrictor plate...so the true change in restrictione is from the move turbulent flow of going around the thermostat being removed.  I personally can't tell a difference, but tried it due to the low capacity stock radiators that these bikes have.  I even tried reconfiguring the radiator from a single-pass to a triple-pass without any noticeable effect from control...
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tzracer

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Re: Thermostat question.
« Reply #5 on: April 16, 2004, 09:22:52 pm »
I installed a small radiator in the by pass circuit of an RC51. It dropped the temps about 20F to 30F.

One thing you can do is to remove the guts of the thermostat and reinstall the part with the hole and the rubber gasket.
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Team_nuclear123

Re: Thermostat question.
« Reply #6 on: May 11, 2004, 09:00:20 am »
Removing the thermostat on the ZX6rr and replacing it with a washer with a 7/8th in hole size was a 45 deg drop in temp.

The GSXR was a 65deg drop, we had to use tape on the radiator in Vegas.
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Jeff

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Re: Thermostat question.
« Reply #7 on: July 21, 2004, 10:31:55 am »
So with all of this in mind, what is the optimal temperature of the motor for power?
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Eric Kelcher

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Re: Thermostat question.
« Reply #8 on: July 21, 2004, 10:44:01 am »
Depends on jetting and motor. The Honda 600RR seemed to like more heat,205-210 the Yamaha R6 about 190-195 the Suzuki GSXR600 seemed to range the most 185-200 Kaw not enough expereince.

This is measured on stock guages and some with water others with antifreeze which could be a variable that I had no control over.
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Eric Kelcher
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