yz/wr 450 boyesen waterpump
Posted November 14, 2005 - 03:37 PM
Posted November 14, 2005 - 05:03 PM
Posted November 14, 2005 - 05:16 PM
i never said anything about restricting flow,i said the slower flow from the stock vs. boyesen seems to work better with more cooling surface area(fluidyne radiators) because of NPG-R's lower rate of heat transfer. maybe you misunderstood what i said about the MX guys cutting the impellars to reduce cavitation at higher rpm's,(at least the team suzuki mechanic i spoke to) resulting in less flow but better cooling in that rpm range, no restriction;just less flow. it probably wouldn't matter as much with us mortals
No problem. And just to clarify, you don't need to restrict flow for proper cooling, it's an old wives tale with a perfectly scientific explanation (the flow restriction also causes a signifigant pressure increase behind the flow restriction, which reduces the boiling point). They specifically mention this on the Evans website and even sell high flow accessories to get the most out of their coolants.
Posted November 14, 2005 - 09:15 PM
From how I read what you were saying it seemed like you were saying you wanted lower flow to counteract the lower rate of heat transfer, when in reality lower flow would lower the heat transfer even further. Is that what you were shooting for?
Posted November 15, 2005 - 05:16 AM
Posted November 15, 2005 - 08:27 AM
From Evans website:
Hi Performance Suggestions
Install hi performance aluminum tube radiator.
Remove the thermostat and plug all bypass hoses.
Install heater shut off valve.
Increase the pump drive ratio with a smaller pump pulley.
Maximizing Racing Systems
Convert the upper hose and thermostat housing to 1 3/4”OD.
Two -16 AN lines minimum upper hose size.
Install external lines from the rear of the manifold, bigger is better, line size should be -12 AN.
For intake manifold fill location use #E3340 Expansion tank.
Use maximum pump drive ratio possible 80% of crank rpm or more.
For safety reasons all overflow hoses must be connected to an overflow tank or catch can.
And more specifically, from their FAQ:
In order to increase COOLANT FLOW, the Evans manual suggests eliminating the thermostat and plugging the flow of coolant through the bypass. Will the resultant increase in coolant flow decrease the effectiveness of the RADIATOR?
NO. Slower coolant flow through the radiator increases the incidence of temperature drop (T), however, this same slower rate also allows for more heat to be added as coolant flows through the heads. Conversely, higher coolant flow rates through the radiator generate less heat loss with less heat being absorbed with flow in the heads. Important: If the thermostat is removed, the bypass must be plugged, or it will scavenge coolant (flow) away from the radiator which will result in the cooling system running warmer than normal.
So, in effect lower flow results in higher temps going into the radiator, lower temps going out of the radiator, and more importantly, higher temps in the head and engine. That's why I was surprised you got rid of your high flow water pump, and why I'm looking for one. Evans does a lot of nice stuff but they're pretty clear on their website that one thing they do need in general is higher flow. I called and asked why they list tons of modifications for flow in cars and list none for motorcycles and they told me they only say don't bother with modifications to motorcycles because most motorcycles have a pretty much self contained system that is difficult to modify (you often don't have high flow water pumps available and fitting larger radiators is not a trivial task) so they just say to leave it alone, but ideally higher flow water pumps and larger radiators complement their product nicely if you don't want higher engine temps.
Or so they're telling me.
Posted November 15, 2005 - 08:58 AM
well spending more time in the radiator is in esscence slowing the flow,and a comparison between automotive and dirtbikes aren't exactly in the same ballpark. yes,same; but yet not. it all sounds kinda contradictary to me? well anyhow you look at it i've solved my problem with heat with no boyesen pump maybe the pump would help more; maybe not.
Conversely, higher coolant flow rates through the radiator generate less heat loss with less heat being absorbed with flow in the heads.
So, in effect lower flow results in higher temps going into the radiator, lower temps going out of the radiator, and more importantly, higher temps in the head and engine.
Posted November 15, 2005 - 10:18 AM
I think the difference in how we're thinking about this is thinking that spending more time in the radiator is in essence slowing the flow. This is where I disagree, rate of transfer of heat is based on differential of temperature. As you speed the flow you get a more average temperature in the whole system. I'm struggling to think of a good way to describe this here...
Say you have three bottles of water you're trying to warm up by setting them in a pan of boiling water that is 212 degrees, one at a time. The water in the bottles is 40 degrees, (warning, bogus numbers coming up) and after setting it in the pan for 1 minute the water in the bottle is up to 60. After two minutes the water in the bottle is up to 70. After three minutes the water in the bottle is up to 75. The bottle heats less as time goes on because the temperature differential between the bottle and the pan is decreasing. After three minutes you have one bottle that is 75 degrees, and two bottles that are 40 degrees. If you mixed them all together you'd have one big container of fluid that is about 51.5 degrees.
Now if you did the same thing but had three bottles and changed them every minute (higher flow). After one minute you have a one bottle that is 60 degrees and two bottles that are 40. Now you change bottles, and after two minutes you have two bottles at 60 degrees and one at 40. Swap them again and you have three bottles at 60 degrees, for an average fluid temperature of 60 degrees instead of 51.5.
Some people would think this mean the bottles were cooling the pan better as evidenced by a lower reading on the thermometer stuck in the container that you poured all of the water into, but in reality the warmer water is cooling better because it pulled more heat out of the pan. Every second the same water is sitting in the head it's absorbing less and less heat, because it's becoming closer and closer to the same temperature as the head, and every second the same water is in your radiator it's dumping less and less heat for the same reason.
That's why engines run cooler with higher flow, and people often think their motors are running better with lower flow. Thermodynamics don't really care if it's a car engine, motorcycle engine, insulation in your house, or bottles of water.
Posted November 15, 2005 - 10:41 AM
Posted November 15, 2005 - 12:07 PM
Turbulence I don't see as an issue at all, can you elaborate on that one? As for cavitation, that's not really an issue with high flow, it's an impediment to achieving high flow. Higher flow doesn't cause cavitation, trying to achieve higher flow improperly (say through turning the water pump at a sub-optimal speed or poor impeller design) can cause cavitation but that really just means you've failed at achieving higher flow.