Engine Cooling: Water Pump Flow Data

General engine tech -- Drag Racing to Circle Track

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Tom68
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Re: Engine Cooling: Water Pump Flow Data

Post by Tom68 »

blown265 wrote: Sat Jun 25, 2022 5:05 am G'day all.

I have a Davies Craig EWP150 40gal/min electric pump installed in the lower radiator hose, adding flow to the factory mechanical pump, on my personal 1971 street/strip car.

On the subject of cavitation, does this electric pusher pump before the OEM mechanical, raise the rpm cavitation threshold?
For example, if the factory (pressed impeller) mechanical item thrashes the water at 5000rpm, does the added EWP150 electric raise this rpm point appreciably 6000rpm?

The reason I ask, is if the above premise holds true, I was considering raising the mechanical pump speed with a smaller pump pulley for more low rpm flow, and then relying on the electric pump to maintain reasonable system flow at redline. (minimal cavitation) The current cooling is good, but I'd like more safety margin for the occasional worst street situations eg, 110 degf summer days on a slow car cruise, or peak hour traffic jam.

I use the EWP150 thermatically switched on at 185 degf, off at 175, and have an indicator light on the A pillar, showing when the electric pump is running. Interestingly, the majority of the electric pumps' use/need is at low rpm, suggesting the factory mechanical is a poor performer at idle and low rpm.

Thanks
Paulie
Low speed normally means you have a fan inefficiency since at higher speed, speed creates air flow without a fan.

Low speed low power production creates coolant temp rise if your ignition point is too late and you end up heating the cylinder more than pushing the piston down.

I'd dump the Davies Craig, OEM wouldn't use them and neither should we.
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Re: Engine Cooling: Water Pump Flow Data

Post by RevTheory »

Who are we to assume is Stewart's "closest competitor?" Edelbrock maybe?
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Re: Engine Cooling: Water Pump Flow Data

Post by Rick! »

fabr wrote: Fri Jun 24, 2022 8:22 pm
RCJ wrote: Fri Jun 24, 2022 3:06 pm I've used both the Stewart and prw. They both worked fine,they were on different motors but both motors ran at acceptable Temps. The block and heads are probably setting the flow rate just like a cylinder head port.
and the head gasket,flow losses/restriction in hoses,radiator flow restriction,etc. all add to total head and that is what determines flow rates SFAIK.
The design head of the pump never changes. I've measured the pressure at the inlet and outlet of the impeller and when the design rpm of the impeller is hit the design head is achieved, no matter the total system restriction. The items you mention will shift flow to the left (lower flow) on the Stewart graphs and lower the inlet pressure which will let you know if the pump is at risk for cavitation.

A key piece of information to matching a pump and a cooling system is measuring the flow and pressure drop across the vehicle's system. Then this curve is plotted on the water pump curves and one can verify if the pump is operating in its "happy" spot for efficiency or if the system is too restrictive. Since most folks don't have access to data acq and turbine flow meters, it's a bit of a challenge to get this data.

For water pump technical data on the web, other than industrial data, it is nearly non-existent for automotive water pumps. The Stewart data is the first I've seen. The only thing I found was that Nascar pumps were putting out 90gpm at 9000rpm (engine) some time ago. Edelbrock does use a pump dyno as stated in a 2009 Motortrend article. Aside from that, there is minimal available data that I've been able to find. Maybe Kevin can do some of his magic SAE searches and sort through the myriad papers to pull out some nuggets of information.
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Re: Engine Cooling: Water Pump Flow Data

Post by chimpvalet »

Tom68 wrote: Sat Jun 25, 2022 5:26 am
blown265 wrote: Sat Jun 25, 2022 5:05 am G'day all.

I have a Davies Craig EWP150 40gal/min electric pump installed in the lower radiator hose, adding flow to the factory mechanical pump, on my personal 1971 street/strip car.

On the subject of cavitation, does this electric pusher pump before the OEM mechanical, raise the rpm cavitation threshold?
For example, if the factory (pressed impeller) mechanical item thrashes the water at 5000rpm, does the added EWP150 electric raise this rpm point appreciably 6000rpm?

The reason I ask, is if the above premise holds true, I was considering raising the mechanical pump speed with a smaller pump pulley for more low rpm flow, and then relying on the electric pump to maintain reasonable system flow at redline. (minimal cavitation) The current cooling is good, but I'd like more safety margin for the occasional worst street situations eg, 110 degf summer days on a slow car cruise, or peak hour traffic jam.

I use the EWP150 thermatically switched on at 185 degf, off at 175, and have an indicator light on the A pillar, showing when the electric pump is running. Interestingly, the majority of the electric pumps' use/need is at low rpm, suggesting the factory mechanical is a poor performer at idle and low rpm.

Thanks
Paulie
Low speed normally means you have a fan inefficiency since at higher speed, speed creates air flow without a fan.

Low speed low power production creates coolant temp rise if your ignition point is too late and you end up heating the cylinder more than pushing the piston down.

I'd dump the Davies Craig, OEM wouldn't use them and neither should we.
True, high vehicle speed should equate to good rad cooling unless something is disastrously poorly designed. On the other hand, we can have a situation wherein the car is moving slowly yet at high power conditions, eg - climbing tight switchback roads on a mountainside incline, and there we can truly see whether cooling is up to par. As to the Davies-Craig pumps, what's the knock? I'd expect the Aussies know their way around engine cooling.
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Re: Engine Cooling: Water Pump Flow Data

Post by NewbVetteGuy »

blown265 wrote: Sat Jun 25, 2022 5:05 am G'day all.

I have a Davies Craig EWP150 40gal/min electric pump installed in the lower radiator hose, adding flow to the factory mechanical pump, on my personal 1971 street/strip car.

On the subject of cavitation, does this electric pusher pump before the OEM mechanical, raise the rpm cavitation threshold?
For example, if the factory (pressed impeller) mechanical item thrashes the water at 5000rpm, does the added EWP150 electric raise this rpm point appreciably 6000rpm?

The reason I ask, is if the above premise holds true, I was considering raising the mechanical pump speed with a smaller pump pulley for more low rpm flow, and then relying on the electric pump to maintain reasonable system flow at redline. (minimal cavitation) The current cooling is good, but I'd like more safety margin for the occasional worst street situations eg, 110 degf summer days on a slow car cruise, or peak hour traffic jam.

I use the EWP150 thermatically switched on at 185 degf, off at 175, and have an indicator light on the A pillar, showing when the electric pump is running. Interestingly, the majority of the electric pumps' use/need is at low rpm, suggesting the factory mechanical is a poor performer at idle and low rpm.

Thanks
Paulie
My experience with brewery liquid pumps, makes me think that the extra electric pump should help with cavitation. -The reduction in pressure on the suction side lowers the boiling point, increasing the pressure helps to increase the boiling point. When I'm circulating liquids at 210F and I get cavitation, simply restricting the flow on the outlet a little bit increases the pressure on both the outlet and the inlet and little bit and that little bit of increased pressure on the inlet side normally raises the boiling point high enough that the cavitation stops. (Sanitary brewery pumps are magnetic drive and when they cavitate you INSTANTLY know about it as they let out a TERRIBLE, TERRIBLE sequealing sound, so you have a real-time feedback loop that cavitation is happening and it makes it easy to quickly figure out what helps stop cavitation/ move it further away from your operating conditions.)

I'd think that the EWP150 would increase the pressure on the inlet side of your mechanical pump to help keep cavitation at bay a bit longer because the increased pressure on the inlet side of the mechanical pump means an increased boiling point.

Adam
Last edited by NewbVetteGuy on Mon Jun 27, 2022 1:02 pm, edited 1 time in total.
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Re: Engine Cooling: Water Pump Flow Data

Post by NewbVetteGuy »

RevTheory wrote: Sat Jun 25, 2022 6:30 am Who are we to assume is Stewart's "closest competitor?" Edelbrock maybe?
That's my working theory. I can't see it being anyone else.

Who cares about water pump flow that's also a decent volume business? -The circle track guys sure do, and Stewarts and Edelbrock seem to loom large there. I wonder how much of Stewart's business is circle track racers; probably not a tiny percentage..


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Re: Engine Cooling: Water Pump Flow Data

Post by blown265 »

Quote:
"I'd think that the EWP150 would increase the pressure on the inlet side of your mechanical pump to help keep cavitation at bay a bit longer because the increased pressure on the inlet side of the mechanical pump means an increased boiling point."

Thanks Adam- exactly the information I was looking for.
Cheers
Paulie
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Re: Engine Cooling: Water Pump Flow Data

Post by NewbVetteGuy »

blown265 wrote: Tue Jun 28, 2022 5:51 am Quote:
"I'd think that the EWP150 would increase the pressure on the inlet side of your mechanical pump to help keep cavitation at bay a bit longer because the increased pressure on the inlet side of the mechanical pump means an increased boiling point."

Thanks Adam- exactly the information I was looking for.
Cheers
Paulie
It DOES seem kinda weird that you're adding an electric pump to a mechanical pump that cavitates before your peak HP RPM, though...

To me you'd still want a mechanical pump that flows well at higher RPM and doesn't significantly cavitate until your HP RPM is reached. My understandings is the impeller design trade-offs that favor higher RPMs without cavitation, slightly hurt low RPM, so then you'd have the electrical pump helping out at low RPM where the mechanical is weak, and the mechanical doing what it's naturally good at at higher RPMs, no?

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Re: Engine Cooling: Water Pump Flow Data

Post by Walter R. Malik »

NewbVetteGuy wrote: Mon Jun 27, 2022 12:55 pm
RevTheory wrote: Sat Jun 25, 2022 6:30 am Who are we to assume is Stewart's "closest competitor?" Edelbrock maybe?
That's my working theory. I can't see it being anyone else.

Who cares about water pump flow that's also a decent volume business? -The circle track guys sure do, and Stewarts and Edelbrock seem to loom large there. I wonder how much of Stewart's business is circle track racers; probably not a tiny percentage..


Adam
I have a feeling the RPM level of those race engines is a lot higher than highway cruising speeds.
Different scenarios usually need different pumps.
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Re: Engine Cooling: Water Pump Flow Data

Post by blown265 »

NewbVetteGuy wrote: Tue Jun 28, 2022 1:52 pm
blown265 wrote: Tue Jun 28, 2022 5:51 am Quote:
"I'd think that the EWP150 would increase the pressure on the inlet side of your mechanical pump to help keep cavitation at bay a bit longer because the increased pressure on the inlet side of the mechanical pump means an increased boiling point."

Thanks Adam- exactly the information I was looking for.
Cheers
Paulie
It DOES seem kinda weird that you're adding an electric pump to a mechanical pump that cavitates before your peak HP RPM, though...

To me you'd still want a mechanical pump that flows well at higher RPM and doesn't significantly cavitate until your HP RPM is reached. My understandings is the impeller design trade-offs that favor higher RPMs without cavitation, slightly hurt low RPM, so then you'd have the electrical pump helping out at low RPM where the mechanical is weak, and the mechanical doing what it's naturally good at at higher RPMs, no?

Adam
Cheers Adam, and I agree. Unfortunately this engine isn't common by world standards, and there are zero aftermarket options aside from the factory replacement designed in the late 60's.

In truth, I'm not aware of any Australian company that has documented water flow testing on this engine (I6 265ci), and therefore established exactly where the pump cavitates. Given the stamped 90deg impeller, I'd suggest it's below max rpm. Having said that, there was a National Touring Car circuit race category these factory stock vehicles competed in during the late 60s and early 70s. Sustained engine speeds were in the 4000 to 6000rpm range depending on year/spec/etc. I'm not aware of pump mods (if any) these cars employed. Stock pulley ratio is approx 1:1 (I'll check later tonight)

For my engine (supercharged, and on propane), the addition of the EWP150 improved the engine temps particularly in adverse conditions. The car kept its cool well prior (in slow and high speed conditions) with a ducted aftermarket radiator, well shrouded 40Amp twin electric fans, and standard pump, but the additional electric pump added consistency and lowered max temperatures. Now the engine, on two gauges taking readings from two different locations, runs consistently between 180 - 190degf in all conditions to date. (170degf t-stat fully open at 180degf)

However, the approach mentioned in my previous post, is intended (if viable) to add a further safety margin for worst case scenarios.
Your thoughts?

Thanks
Paulie
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Re: Engine Cooling: Water Pump Flow Data

Post by NewbVetteGuy »

Just to keep this all in one place, came across an interview from 2001 with Jim McFarland where he addresses many of the items brought up in this thread directly.

Coolant flow speed, some allusions to Smokey findings, why Winston Cup teams and Circle Track racers use AN lines, how some head mfgrs have tried to address issues with the internal coolant passages.

https://www.motortrend.com/how-to/95238/



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Re: Engine Cooling: Water Pump Flow Data

Post by fabr »

Nice article.
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Re: Engine Cooling: Water Pump Flow Data

Post by chimpvalet »

Great article, reads as correct top to bottom IMO.
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Re: Engine Cooling: Water Pump Flow Data

Post by Tom68 »

blown265 wrote: Sat Jun 25, 2022 5:05 am G'day all.

I use the EWP150 thermatically switched on at 185 degf, off at 175, and have an indicator light on the A pillar, showing when the electric pump is running. Interestingly, the majority of the electric pumps' use/need is at low rpm, suggesting the factory mechanical is a poor performer at idle and low rpm.

Thanks
Paulie
Where do you have the sensor/switch that turns the pump on plumbed in ?
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Re: Engine Cooling: Water Pump Flow Data

Post by blown265 »

G'day Tom

The brass 185f/175f Tridon switch is tapped into the thermostat housing, and triggers separate relays for the electric fans and pump. The t-stat is a high flow 170f Tridon for a GM-H vehicle, but fits the Chrysler housing as well.

The mechanical pump pulley has been modified to make clearance for the blower belt (belt is off in the pics), but its that pulley that I'm considering making smaller for more mechanical pump contribution at low/medium revs.

I like Adams thought process as well (m.pump geared for high rpm and using the e.pump for low rpm flow), but this car spends more time on the street than strip, hence the m.pump gearing propsal for low rpm.

Regards
Paulie
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