Reverse Flow/Electric Water Pump Cooling System
05-31-2009, 02:07 PM
#21
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If the car is moving, the pump is running, there it no t-stat, and the fans are off, the engine can still overcool.
The electric pump is a lower power pump than the typical mechanical water pump. I'm not saying it's "inferior" - I'm saying it needs to run without a t-stat, and a consequence of this is the lower pressure in the cylinder head - which may mean Evans coolant would be needed to counteract this downside. I measured the actual coolant pressures years ago, and I found that when an engine is revved, the pressure rises significantly, even with a full open t-tat. If you look at the pressure-flow curves of the DC (I had to ask for the curves years ago), it can't build more than a couple of psi.
Second, I ran calculations of the required coolant flow given a certain amount of heat rejection, the DC pump cannot work with more than a certain amount of pressure head.
The electric pump is a lower power pump than the typical mechanical water pump. I'm not saying it's "inferior" - I'm saying it needs to run without a t-stat, and a consequence of this is the lower pressure in the cylinder head - which may mean Evans coolant would be needed to counteract this downside. I measured the actual coolant pressures years ago, and I found that when an engine is revved, the pressure rises significantly, even with a full open t-tat. If you look at the pressure-flow curves of the DC (I had to ask for the curves years ago), it can't build more than a couple of psi.
Second, I ran calculations of the required coolant flow given a certain amount of heat rejection, the DC pump cannot work with more than a certain amount of pressure head.
Lower power pump? Nonsense. Needs to run without a t-stat? Nonsense.
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05-31-2009, 03:02 PM
#23
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mrtonyg, Jason's assertion is that the volume of water flowed by a pump in free space is much greater than the volume flowed against a restriction (such as a thermostat).
In order to satisfy him, you will need to post a picture of the pump throwing a stream of water while its outlet is restricted by something having approximately the same passage area as a fully open thermostat, such as an overdrilled fender washer or a partially closed ball valve. +1 for measuring the volume of water pumped per minute before and after, by measuring the time taken to empty a bucket containing a known quantify of water. +2 if you can figure out how to run the same test on a stock Miata water pump for comparison.
In order to satisfy him, you will need to post a picture of the pump throwing a stream of water while its outlet is restricted by something having approximately the same passage area as a fully open thermostat, such as an overdrilled fender washer or a partially closed ball valve. +1 for measuring the volume of water pumped per minute before and after, by measuring the time taken to empty a bucket containing a known quantify of water. +2 if you can figure out how to run the same test on a stock Miata water pump for comparison.
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05-31-2009, 05:36 PM
#24
-G-
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05-31-2009, 05:56 PM
#25
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how long have you ran this situation on the street?The ultimate test is running on the street(or track) in a heat soaked or winter time run.then you will KNOW whats what.In Albuquerque N.M.,Ive ran a coolant reroute that would not allow the engine to see full warm up,motivating me to return to stock.
-G-
-G-
My claim is that reverse flow cooling has allowed me to run a more aggressive timing curve... nothing, more nothing less. It achieved my goal.
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05-31-2009, 06:12 PM
#26
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mrtonyg, Jason's assertion is that the volume of water flowed by a pump in free space is much greater than the volume flowed against a restriction (such as a thermostat).
In order to satisfy him, you will need to post a picture of the pump throwing a stream of water while its outlet is restricted by something having approximately the same passage area as a fully open thermostat, such as an overdrilled fender washer or a partially closed ball valve. +1 for measuring the volume of water pumped per minute before and after, by measuring the time taken to empty a bucket containing a known quantify of water. +2 if you can figure out how to run the same test on a stock Miata water pump for comparison.
In order to satisfy him, you will need to post a picture of the pump throwing a stream of water while its outlet is restricted by something having approximately the same passage area as a fully open thermostat, such as an overdrilled fender washer or a partially closed ball valve. +1 for measuring the volume of water pumped per minute before and after, by measuring the time taken to empty a bucket containing a known quantify of water. +2 if you can figure out how to run the same test on a stock Miata water pump for comparison.
If you look at the design of the factory pump you being to wonder how it can circulate coolant. Factory pumps actually "pump" very little. If fact, almost all factory cooling systems that utilize mechanical pumps use gravity and the properties of hot coolant to help in circulation.
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05-31-2009, 07:30 PM
#28
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However, knock threshold has a lot of variability, thus the CHT measurement that Reverend Greg suggested would be a great way of double checking for improved head cooling. For example, IAT, fuel octane, and probably oil temperature, all would move the knock threshold around.
Now because you just dig your heels in and say "nonsense" to the stuff I investigated years ago, I will just patiently wait for other datapoints from you, such as temperatures at the track.
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05-31-2009, 07:31 PM
#29
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If you look at the design of the factory pump you being to wonder how it can circulate coolant. Factory pumps actually "pump" very little. If fact, almost all factory cooling systems that utilize mechanical pumps use gravity and the properties of hot coolant to help in circulation.
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05-31-2009, 07:48 PM
#30
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Copying myself from
MX-5 Miata Forum - View Single Post - Skunk2 trick: Electric water pump
I did some calculations and this water pump may flow enough to cool a turbo miata motor on the track:
http://www.daviescraig.com/main/display.asp?pid=8
note: the above link which I think was to the pump curve, is gone.
Mechanical water pumps are designed to be lossy, so that at low speed it flows enough to cool the engine, and at high speed have enough "leakage" so that they don't build too much pressure and draw too much power. They probably draw a few hp at high RPM. (Compare this to 100W for the Davies Craig 80 l / min model)
The Daviescraig pump draws ~8A and flows 80 li/min at zero pressure drop, and 50 li/min at 3 psi of pressure head.
At around 50 l/min flow rate, flowing water, it can carry away 50 hp of heat (average heat generated, not peak wheel hp) with a 10*C rise in water temperature. So far so good.
The real attraction is not the hp saved, but two things - you can get max flow at idle, possibly solving overheating at low speeds, and more importantly, being able to run your coolant in reverse as mentioned above.
Running coolant in reverse reduces temperatures in the head, all else being equal, helping prevent detonation. However, according to a patent by Evans (Evanscooling.com), you can get water vapor bubbles trapped in the head if you simply convert a conventional engine. His patent was violated by GM, according to his website, which shows using special little traps to get the vapor bubbles circulating. (I looked at the patent).
Another way to solve the vapor bubbles issue running coolant in reverse, is to use hi temperature coolant, NPG and NPG+, which have a 350*F boiling point. So, the combo of electric pump, reverse flow, and NPG seems synergistic.
MX-5 Miata Forum - View Single Post - Skunk2 trick: Electric water pump
I did some calculations and this water pump may flow enough to cool a turbo miata motor on the track:
http://www.daviescraig.com/main/display.asp?pid=8
note: the above link which I think was to the pump curve, is gone.
Mechanical water pumps are designed to be lossy, so that at low speed it flows enough to cool the engine, and at high speed have enough "leakage" so that they don't build too much pressure and draw too much power. They probably draw a few hp at high RPM. (Compare this to 100W for the Davies Craig 80 l / min model)
The Daviescraig pump draws ~8A and flows 80 li/min at zero pressure drop, and 50 li/min at 3 psi of pressure head.
At around 50 l/min flow rate, flowing water, it can carry away 50 hp of heat (average heat generated, not peak wheel hp) with a 10*C rise in water temperature. So far so good.
The real attraction is not the hp saved, but two things - you can get max flow at idle, possibly solving overheating at low speeds, and more importantly, being able to run your coolant in reverse as mentioned above.
Running coolant in reverse reduces temperatures in the head, all else being equal, helping prevent detonation. However, according to a patent by Evans (Evanscooling.com), you can get water vapor bubbles trapped in the head if you simply convert a conventional engine. His patent was violated by GM, according to his website, which shows using special little traps to get the vapor bubbles circulating. (I looked at the patent).
Another way to solve the vapor bubbles issue running coolant in reverse, is to use hi temperature coolant, NPG and NPG+, which have a 350*F boiling point. So, the combo of electric pump, reverse flow, and NPG seems synergistic.
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05-31-2009, 07:51 PM
#31
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Yes you showed that data and I did note it when I first read your post.
However, knock threshold has a lot of variability, thus the CHT measurement that Reverend Greg suggested would be a great way of double checking for improved head cooling. For example, IAT, fuel octane, and probably oil temperature, all would move the knock threshold around.
However, knock threshold has a lot of variability, thus the CHT measurement that Reverend Greg suggested would be a great way of double checking for improved head cooling. For example, IAT, fuel octane, and probably oil temperature, all would move the knock threshold around.
Obviously, there are many variables that affect the knock threshold, and those were kept to a minimum during my testing.
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05-31-2009, 08:11 PM
#32
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I am sorry you disagree.
Do you know that some of the early water cooled systems for automobiles didn't used water pumps at all? They relied on the temperature differential of the water to establish flow.
The colder water would sit at the bottom of the block, as it heated it would rise up as colder water would take its place thus establishing flow. The same basic system is still employed today.
Do you know that some of the early water cooled systems for automobiles didn't used water pumps at all? They relied on the temperature differential of the water to establish flow.
The colder water would sit at the bottom of the block, as it heated it would rise up as colder water would take its place thus establishing flow. The same basic system is still employed today.
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05-31-2009, 08:55 PM
#33
Joe, at this point in the design, I doesn't make any sense for me to perform this test.
If you look at the design of the factory pump you being to wonder how it can circulate coolant. Factory pumps actually "pump" very little. If fact, almost all factory cooling systems that utilize mechanical pumps use gravity and the properties of hot coolant to help in circulation.
If you look at the design of the factory pump you being to wonder how it can circulate coolant. Factory pumps actually "pump" very little. If fact, almost all factory cooling systems that utilize mechanical pumps use gravity and the properties of hot coolant to help in circulation.
I am sorry you disagree.
Do you know that some of the early water cooled systems for automobiles didn't used water pumps at all? They relied on the temperature differential of the water to establish flow.
The colder water would sit at the bottom of the block, as it heated it would rise up as colder water would take its place thus establishing flow. The same basic system is still employed today.
Do you know that some of the early water cooled systems for automobiles didn't used water pumps at all? They relied on the temperature differential of the water to establish flow.
The colder water would sit at the bottom of the block, as it heated it would rise up as colder water would take its place thus establishing flow. The same basic system is still employed today.
-G-
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05-31-2009, 09:59 PM
#34
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Tony I don't disagree the reverse flow will result in reduced head temperatures, all else being equal.
The big question is whether or not the Davies Craig has enough flow/pressure to handle a turbo miata on a hot track day. I think it won't be, with a t-stat in place, and may be, if the t-stat is removed.
The big question is whether or not the Davies Craig has enough flow/pressure to handle a turbo miata on a hot track day. I think it won't be, with a t-stat in place, and may be, if the t-stat is removed.
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05-31-2009, 11:11 PM
#35
I am using a Mezeire pump intended for SBC's it has more than enough to pump a swimming pool through a straw,plus I am fabbing an air bleed that will exit at the plugs in the head under the Valve cover.may take a week or so to get to,I am finding this a very helpful intercourse.Thanx to all.
-Greg-
-Greg-
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05-31-2009, 11:45 PM
#38
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I am using a Mezeire pump intended for SBC's it has more than enough to pump a swimming pool through a straw,plus I am fabbing an air bleed that will exit at the plugs in the head under the Valve cover.may take a week or so to get to,I am finding this a very helpful intercourse.Thanx to all.
-Greg-
-Greg-
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