Underdrive pulley recommendations?

[davemon]

Looking at adding a UDP, has anyone had any issues with engine temp from spinning the pump more slowly? I live in hot a$$ texas.

I saw Jake's post about cooler temps but either that is counter-intuitive or I'm missing something, and I'm comfortable admitting I may be missing more than just something here . Shouldn't less spinning = less cooling???

[amondc]

I live in hot ass Texas also. No problems here. Where are you at?

[davemon]

Originally Posted by amondc

I live in hot ass Texas also. No problems here. Where are you at?

I guess I'm amongst the folks trying to keep it weird.

[amondc]

Well if you are near southlake and want to come check one out let me know.

Chris

[Boxtaboy]

I found this read on Underdrive Pulleys interesting: http://www.streettostrip.com/content/view/82/40/

[Wingnut2u]

Originally Posted by davemon

Looking at adding a UDP, has anyone had any issues with engine temp from spinning the pump more slowly? I live in hot a$$ texas.

I saw Jake's post about cooler temps but either that is counter-intuitive or I'm missing something, and I'm comfortable admitting I may be missing more than just something here . Shouldn't less spinning = less cooling???

davemon

I also live in Texas and I have installed Chris' (amondc) underdrive pulley and I can tell you first hand that my temps are cooler. It is also a daily driver for me and I have had no ill effects.

One of the best bangs for your buck in my opinion.

[mikefocke]

I presume you are reading the temps off the guages.

Driving the accessories at a slower rate would spin the water pump slower which would evacuate heat slower which would mean that the water getting to the radiators would be hotter wouldn't it?

What am I missing here? Make any other changes?

[JFP in PA]

While it may seem counter intuitive, slowing down the water pump can actually produce lower coolant temperatures (within limits). In any cooling system, there is an “ideal” coolant flow rate, at which the heat source is exposed to the coolant for the optimum amount of time for heat transfer to be accomplished. The radiators also have an “ideal” flow rate to get rid of the heat as well. In an Ideal application, the pump would run at a constant speed to provide the best possible cooling (this is one of the several reasons why a lot of race cars use electrically driven water pumps). Unfortunately, because most street automotive cooling systems are mechanically driven (by the belt), once the thermostat is open, the coolant is typically either moving too fast or too slow for optimum transfer due to the range of RPM’s them pump is seeing, resulting in suboptimum heat transfer.

In years gone by, a lot of racers used to pull the thermostats out of engines using belt driven water pumps, assuming “the more flow, the better”, only to find the engine actually ran hotter. But when they replaced the thermostat with a restrictor plate, the engine ran cooler. It had too much flow without the restrictor or the thermostat………..

[davemon]

Originally Posted by JFP in PA

While it may seem counter intuitive, slowing down the water pump can actually produce lower coolant temperatures (within limits). In any cooling system, there is an “ideal” coolant flow rate, at which the heat source is exposed to the coolant for the optimum amount of time for heat transfer to be accomplished. The radiators also have an “ideal” flow rate to get rid of the heat as well. In an Ideal application, the pump would run at a constant speed to provide the best possible cooling (this is one of the several reasons why a lot of race cars use electrically driven water pumps). Unfortunately, because most street automotive cooling systems are mechanically driven (by the belt), once the thermostat is open, the coolant is typically either moving too fast or too slow for optimum transfer due to the range of RPM’s them pump is seeing, resulting in suboptimum heat transfer.

In years gone by, a lot of racers used to pull the thermostats out of engines using belt driven water pumps, assuming “the more flow, the better”, only to find the engine actually ran hotter. But when they replaced the thermostat with a restrictor plate, the engine ran cooler. It had too much flow without the restrictor or the thermostat………..

Thanks for the responses.

Suspected that running through the radiators too fast wouldn't create the exposure long enough to cool effectively... but then also suspected that these engines were designed to cool optimally at 4500-6500 rpms, when the cooling is needed more. Or maybe they were designed with more umm "average driving conditions" in mind with the rpms typically in the 2k-4k range and not catering to the enthusiast-type crowd who wants to feel their backs against the seat all the time, but again this is counter intuitive to a lot of other things that are designed to run a hard. Then I suspected I should just ask the experts Well whatever the ideal range, nobody seems to have any issue with hot engines, even those of us that that live in the heat.

[blue2000s]

Originally Posted by JFP in PA

While it may seem counter intuitive, slowing down the water pump can actually produce lower coolant temperatures (within limits). In any cooling system, there is an “ideal” coolant flow rate, at which the heat source is exposed to the coolant for the optimum amount of time for heat transfer to be accomplished. The radiators also have an “ideal” flow rate to get rid of the heat as well. In an Ideal application, the pump would run at a constant speed to provide the best possible cooling (this is one of the several reasons why a lot of race cars use electrically driven water pumps). Unfortunately, because most street automotive cooling systems are mechanically driven (by the belt), once the thermostat is open, the coolant is typically either moving too fast or too slow for optimum transfer due to the range of RPM’s them pump is seeing, resulting in suboptimum heat transfer.

In years gone by, a lot of racers used to pull the thermostats out of engines using belt driven water pumps, assuming “the more flow, the better”, only to find the engine actually ran hotter. But when they replaced the thermostat with a restrictor plate, the engine ran cooler. It had too much flow without the restrictor or the thermostat………..

Faster flow rates keep temperatures more uniform. There's less temperature difference between the inlet and outlet of the engine if coolant is moving faster. This will translate into component temperatures directly. Flow a fluid over a surface and if you don't change the fluid temperature or the surface heat output, the surface will be cooler with faster fluid flow. But the fluid temperature rise decreases as it's speed increases.

An ideal flow rate will keep the most sensitive component below it's critical temperature for any given load/speed/environment condition. This may be faster or slower flow depending on where the component is or even if it's always the same component.

The important point here is that the temperature of the coolant at the radiator outlet isn't telling what the component temperatures are inside the engine. The temperatures have to be directly measured or at least modeled with some very expensive software.

Is there a reliability impact from a smaller diameter pulley? I suspect there is, but I don't know. All I know is what's happening when the smaller pulley is installed and if I personally am comfortable with the risk.

[chaudanova]

Has anyone paired one of these underdrive pulleys along with an oversized power steering pulley as well?

Would that be too much of an underdrive, or would that be a good pairing?

[The Radium King]

i was wondering the same thing after seeing both on the cheetah website.

[blue2000s]

Originally Posted by mikefocke

I presume you are reading the temps off the guages.

Driving the accessories at a slower rate would spin the water pump slower which would evacuate heat slower which would mean that the water getting to the radiators would be hotter wouldn't it?

What am I missing here? Make any other changes?

You have to look at this as a temperature difference situation. If the engine is dissipating a set amount of heat, it is true that the slower the coolant flows, the higher it's temperature rise will be. However, the heat then runs through the radiators, and the slower the coolant runs through the radiators, the more heat they can drop into the air. The radiators can bring the coolant temperature closer to the outside air temperature at lower flow rates.

The balancing act is controlled by the flow rate of the coolant. It is conceivable that the coolant temperature is actually reading lower if the sensor is at the inlet to the engine. Chances are that the temperature at the outlet of the engine and into the radiators is running higher with the underdrive pulley.

Where you measure anything is always important to consider.