Flowkooler water pump for RV8
Discussion
Well, it's that time of year again in the American West. Temperatures above 100*F, humidity at 30% or less, and I'm driving at freeway speeds one mile above sea level in my 4.6L Discovery 2. The cooling system fails to keep up, to put things mildly. I've posted here before about it and got some good help figuring out what to do about it. I'm going to get a bigger radiator, but I've been looking at some options for the water pump, and thought the Pistonheads community might be interested in what I came up with.
Flowkooler makes a high-flow water pump for the Buick 215 and the older Rover 3.9L V8s, but they don't currently produce one for the later 4.0L and 4.6L RV8. I've talked to the folks at Flowkooler, and they are willing to develop one, but they need orders for 10 of them with an $80 refundable surcharge to finance the development costs and demonstrate that there is a market for the product. I've placed my order. Their order link is here:
Flowkooler Land Rover water pump
Flowkooler has a good reputation among the hot rod crowd, and Jeep folks. I have one in my Jeep, and it makes a big difference. According to their specs, the Flowkooler pumps use a CNC-machined impeller to increase pump efficiency at low RPMs, so that they have roughly double the flow rate of OEM pumps at idle. Pressure and flow continue to increase until about 3300 RPM, where the impeller stalls at about the maximum working pressure of the OEM pump, so that working pressure does not exceed the cooling circuit design specs and it doesn't reduce engine horsepower at max revs. This helps cool the engine when it's working hard intermittently or at low RPM (for example, with the A/C on in traffic, or in off-road and towing applications).
I'm pretty excited about the possibility of a high-flow pump for my Rover. I'm hoping other people might be as well.
Flowkooler makes a high-flow water pump for the Buick 215 and the older Rover 3.9L V8s, but they don't currently produce one for the later 4.0L and 4.6L RV8. I've talked to the folks at Flowkooler, and they are willing to develop one, but they need orders for 10 of them with an $80 refundable surcharge to finance the development costs and demonstrate that there is a market for the product. I've placed my order. Their order link is here:
Flowkooler Land Rover water pump
Flowkooler has a good reputation among the hot rod crowd, and Jeep folks. I have one in my Jeep, and it makes a big difference. According to their specs, the Flowkooler pumps use a CNC-machined impeller to increase pump efficiency at low RPMs, so that they have roughly double the flow rate of OEM pumps at idle. Pressure and flow continue to increase until about 3300 RPM, where the impeller stalls at about the maximum working pressure of the OEM pump, so that working pressure does not exceed the cooling circuit design specs and it doesn't reduce engine horsepower at max revs. This helps cool the engine when it's working hard intermittently or at low RPM (for example, with the A/C on in traffic, or in off-road and towing applications).
I'm pretty excited about the possibility of a high-flow pump for my Rover. I'm hoping other people might be as well.
Pupp said:
Always interested and supportive of something nice being developed but there's a nagging thought in the back of my mind that increasing flow doesn't necessarily equate to better cooling - ie if the coolant flows too quickly for heat transfer to occur... ?
Thanks for the supportive words. If you achieve more flow by reducing back pressure (i.e., by removing the thermostat), that can cause problems. But increasing flow by increasing pump pressure will always increase cooling. I've posted on another site this explanation of why more flow is better, I'll just cut and paste here: Neil said:
More flow, as long as you don't reduce the system pressure, will always mean more cooling. The more trips the coolant takes through the system per minute, the more heat it will move. I've heard people say more flow makes things worse, that coolant needs sufficient time in the radiator to get cooled down, but that's wrong.
Heat flows from hot things to cold things. The hotter the hot thing is, and the colder the cold thing is, the faster the heat flows. All other things being equal (meaning, if you aren't increasing flow by reducing back pressure, like removing the thermostat or putting in a high-flow radiator), as flow increases the coolant temperature will increase less as it goes through the engine, and its temperature will decrease less as it goes through the radiator and *that is a good thing*. That means that all the way through the engine, the coolant is absorbing more heat, because there is a greater temperature difference between the block and the coolant. All the way through the radiator, the coolant is shedding more heat, because the temperature difference between the coolant and the radiator fins is greater. And it's making more trips in the same amount of time through the circuit, so the overall heat rejection is higher. The end result is a more stable engine temperature.
Heat flows from hot things to cold things. The hotter the hot thing is, and the colder the cold thing is, the faster the heat flows. All other things being equal (meaning, if you aren't increasing flow by reducing back pressure, like removing the thermostat or putting in a high-flow radiator), as flow increases the coolant temperature will increase less as it goes through the engine, and its temperature will decrease less as it goes through the radiator and *that is a good thing*. That means that all the way through the engine, the coolant is absorbing more heat, because there is a greater temperature difference between the block and the coolant. All the way through the radiator, the coolant is shedding more heat, because the temperature difference between the coolant and the radiator fins is greater. And it's making more trips in the same amount of time through the circuit, so the overall heat rejection is higher. The end result is a more stable engine temperature.
neillr said:
increasing flow by increasing pump pressure will always increase cooling
I'd add a caveat to that - the RV8 needs (and already has) very generous coolant flow through the heads to prevent hot spots, and if the engine is revving enough to be anywhere near the power band then the thermal mass flow rate of the water side is likely to be huge compared to the thermal mass flow on the air side. In other words, if you're looking for better cooling under power, getting more and cooler air flow, and improving the connection between the air and water, is probably going to give better benefits than increasing the coolant flow.GreenV8S said:
...if the engine is revving enough to be anywhere near the power band then the thermal mass flow rate of the water side is likely to be huge compared to the thermal mass flow on the air side.
I think that's probably true, and I'm getting a bigger radiator as well. But I do think the OEM pump doesn't provide sufficient flow below about 2250RPM, which is a problem in the truck application where you spend a lot of time running the A/C and lugging the engine due to terrain or towing.Increasing flow at idle can also help in intermittent applications, where you run in the power band for short periods, and then have longer periods of idling in which the engine could cool off if provided with sufficient flow to do so. This can apply to off-road, towing, or hot rods.
Edited by neillr on Monday 14th August 23:44
neillr said:
I do think the OEM pump doesn't provide sufficient flow below about 2250RPM, which is a problem in the truck application where you spend a lot of time running the A/C and lugging the engine due to terrain or towing.
That makes sense and is consistent with my experience. I don't spend much time lugging at low rpm, but I have noticed that coming off load and dropping down to a hot idle the cooling system really struggles despite big fans and radiator - even a small increase in coolant flow from a booster pump made a significant difference at very low rpm. GreenV8S said:
That makes sense and is consistent with my experience. I don't spend much time lugging at low rpm, but I have noticed that coming off load and dropping down to a hot idle the cooling system really struggles despite big fans and radiator - even a small increase in coolant flow from a booster pump made a significant difference at very low rpm.
Yes, that's my experience too. It's exactly the kind of situation that Flowkooler pumps are good for, and should be more reliable and less hassle than a booster pump. As I said, I put one in my Cherokee, and along with a bigger radiator it keeps the engine temps fantastically stable.
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