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Hand made impeller with stainless steel vanes yadda yadda.




"Look at this fan blade with the leading edge facing the wrong way!
Chop the leading edge off to improve fans performance!!"
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I looked at a few posts from him on fb built a tester ect. Few guys loving his pumps also has a book on cooling systems. His pumps are upwards of $600

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I looked at a few posts from him on fb built a tester ect. Few guys loving his pumps also has a book on cooling systems. His pumps are upwards of $600

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Testing a pump on a generic tester is not ideal. This may give you an indication of pump performance, but the one critical aspect it misses is the pump vane to timing cover clearance. It is more often than not this critical clearance which is the cause of cavitation. This is why it is critical to test pump operation in situation to ascertain the root cause of poor pump performance.
 

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I understand why Derk has a universal pump tester as he offers upgraded pumps for many various engines. To have individual testing of all of his modified pumps the logistics and costs would be prohibitive.

I have mentioned before the critical criteria for pump operation.

1. No cavitation.
2. Must make pressure.
3. Must have good flow.

There is a 4th that I have not mentioned, because most can't get past the 1st criteria.

4. The pump MUST NOT make vacuum.

Vacuum is as critical as any of the other 3 pump criteria.
Measuring pump vacuum is telling you the pumps demand/feed for water.
If the pump makes a vacuum, then this has effectively lowered the boiling point of the cooling system.

This is counter productive to establishing a stable cooling system.
 

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festerGU have you cut the leading edge off your fan and noticed any difference ?
If so how much did you end up removing.?

Sounds like you may be onto something that may help a bit it makes sense if it has a curve at the leading edge to start with, when it's running with air picked up at the tail edge of the blade it will cause it to twist a bit more especially being a plastic fan in a heat soaked area unlike metal fans in older vehicles be interesting to see if it does help thanks.
 

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What is your reference point for "vacuum"? Immediately before the pump compared to atmospheric pressure or to radiator tank pressure?

I think I've previously mentioned (I think) that all of the readings are taken at the end of the cooling system. This is under the thermostat.
Being at the end of the system if you have pump pressure here than you have pump pressure through the entire system. Same with flow, same with vacuum. Also water quality (cavitation) is measured here.
 

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I think I've previously mentioned (I think) that all of the readings are taken at the end of the cooling system. This is under the thermostat.
You have to have a lower pressure just prior to the water pump than at the thermostat otherwise water will not flow through the radiator to the pump. Lowest pressure will always be just prior to the pump and highest pressure will be just after the pump. There will be incremental pressure loss throughout the system until the water gets back to the pump which will always be the point of lowest pressure.
 

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What is your reference point for "vacuum"? Immediately before the pump compared to atmospheric pressure or to radiator tank pressure?

Pressure.

In the cooling system we have system pressure, and hopefully pump pressure.

The two should not be confused.

System pressure-
This is purely the expansion of the coolant in the cooling system.

Pump pressure-
This is the measurent of the water pump discharge.


System pressure can be used to calculate your cooling system efficiency. Simply squeezing the top radiator hose will give an indication of the cooling systems 'health'.
If the top hose is rock hard during normal operation, then your cooling system has issues.
Surprising water doesn't really expand much before boiling.
But.... when you have localised boiling, bubbles are produced and this takes up room in the cooling system causing system pressure.

In a perfect cooling system with a pump that makes good pressure and flow, localised boiling will be absent and cooling system pressure will be extremely low. It is so low that the radiator cap can be removed at operating temp with no eruption or overflow at the radiator.
 

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You have to have a lower pressure just prior to the water pump than at the thermostat otherwise water will not flow through the radiator to the pump. Lowest pressure will always be just prior to the pump and highest pressure will be just after the pump. There will be incremental pressure loss throughout the system until the water gets back to the pump which will always be the point of lowest pressure.
Water will only flow from the radiator to pump when the thermostat is open.
When the stat is closed, water flows through the bypass.
In a closed system, if the pump makes pressure you should have PUMP pressure everywhere.
Obviously directly after the pump should be the greatest flow and pressure, and this will diminish as it passes through the block then the head and out to the thermostat.
 

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Water will only flow from the radiator to pump when the thermostat is open.
When the stat is closed, water flows through the bypass.
Water will still only flow from the thermostat housing to the pump, regardless of whether it is through the radiator or bypass, if the pressure at the pump inlet is lower than at the thermostat housing.

In a closed system, if the pump makes pressure you should have PUMP pressure everywhere.
Obviously directly after the pump should be the greatest flow and pressure, and this will diminish as it passes through the block then the head and out to the thermostat.
I don't see how the flow directly after the pump will be any greater than the flow into the pump or from the block to the head etc. You have a fixed volume of water moving through a closed system so the rate of flow has to be the same everywhere (except for the radiator and bypass arrangement where there is parallel flow).

My point about pressure is that system pressure just before the pump will always be lower than at the thermostat housing or anywhere else in the system for that matter. This means that any water pump, regardless of its efficiency, will be running at a vacuum at its inlet point if you are using the bottom of the thermostat as your reference point..
 

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I would think that pressure and flow would diminish as it passes throughout the engine,especially going from block through the transition holes into the head galleries.

Having measured pressure under the thermostat, there would be pressure fed into the pump, but as the water is squeezed out of the pump it would have more pressure outside of the vanes.
 

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Testing a pump on a generic tester is not ideal. This may give you an indication of pump performance, but the one critical aspect it misses is the pump vane to timing cover clearance. It is more often than not this critical clearance which is the cause of cavitation. This is why it is critical to test pump operation in situation to ascertain the root cause of poor pump performance.
The excess clearance doesn't cause cavitation, it causes lower pump efficiency.
 

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The excess clearance doesn't cause cavitation, it causes lower pump efficiency.
Well when we did pump devolpment, our pump produced bubbles. Tightening the clearance improved pump performance and reduced bubbles. It was only with a impeller modification that cured the bubbles.
 

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Pressure under the thermostat with what reference point?


Once again, pressure with what reference point?

This part of the system we have modified from standard and it also allows testing of the pump flow, right before it re-enters the pump.
 

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festerGU have you cut the leading edge off your fan and noticed any difference ?
If so how much did you end up removing.?

Sounds like you may be onto something that may help a bit it makes sense if it has a curve at the leading edge to start with, when it's running with air picked up at the tail edge of the blade it will cause it to twist a bit more especially being a plastic fan in a heat soaked area unlike metal fans in older vehicles be interesting to see if it does help thanks.
That's not me. That is actually off that derk's facebook site. I posted it as I thought it was completely dodgy. There was a BIG fan thread (size of thread not fan) a couple of years ago with tech info and lots of fan comparisons and I don't recall any mention that our basic fan design was bad. I'm sure that thread went into blade design quite a bit and there are reasons for the design. You would be better off asking @OldMav as he was a major contributor as usualand I don't remember the name of the other guy but i don't think he's been on here much for a while. If I recall he owned 2 GQ's a white and a blue or red.
 

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That's not me. That is actually off that derk's facebook site. I posted it as I thought it was completely dodgy. There was a BIG fan thread (size of thread not fan) a couple of years ago with tech info and lots of fan comparisons and I don't recall any mention that our basic fan design was bad. I'm sure that thread went into blade design quite a bit and there are reasons for the design. You would be better off asking @OldMav as he was a major contributor as usualand I don't remember the name of the other guy but i don't think he's been on here much for a while. If I recall he owned 2 GQ's a white and a blue or red.

Was it Chicken?

I think he showed that the gq fan was more efficient with its straight blades than that of the curved gu blades.

I think the consensus was that Nissan were trying to quieten the fan noise on the gu at the expense of its efficiency.
 
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