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 Post subject: Water Pump Testing?
PostPosted: Sat Jun 11, 2016 5:02 pm 
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Mark, Scott or any other resident ME's:

I'm looking for anyone who has a rig to test engine water pumps. If I can't find anyone who provides the service, then I'll build one to pressure & flow test my 550's water pump in order to see a couple of things:

1. Flow & pressure at different RPM's and with different impellers. (I'm particularly interested in flow at an idle RPM, since that's when our V12's like to overheat.)

2. Power consumption

It would probably comprise a variable speed electric motor with an overdrive pulley for the pump so I could spin it at least as fast as the OEM drive setup (116mm crank pulley with 103mm pump pulley) so 1.13 x engine RPM.

I'd need to recirculate the water (probably would use backyard swimming pool :)) and would want to be able to vary the discharge backpressure and measure pressure & flow at different RPM's.

These little Sotera flowmeters aren't too expensive, and I'd probably put two of them in parallel to be able to measure up to 60 GPM: http://sotera.com/index.cfm/products/pr ... 507&ps=132

Power measurement would be by a wattmeter on the motor, and I'd have to get some efficiency curves from the motor manufacturer to convert to shaft HP.

I wouldn't be able to duplicate the NPSH that the pump would have when mounted on the engine, in the car, but am hoping this difference wouldn't make a significant change in the figures.

Thoughts?


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 Post subject: Re: Water Pump Testing?
PostPosted: Mon Jun 13, 2016 8:37 am 
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I've never actually done any real pump testing, more specing/ordering based on published pump curves. What you're saying sounds right to me in general but honestly I'm not sure how much you really car about the power usage and not looking at that will make your life a little easier

I think you are going to need to know a little bit about the what the cooling system's flow/pressure curve looks like before you will know what any pump curves means exactly and this means measuring on the car which is a bit harder. If you have a pump that you have the curves for, then all you need from the car is inlet & out let pressures at the a few rpms and you'll have what you need I think.

How serious is the overheating? Does it happen with a NEW radiator, as in actually new not just "I had it checked and its fine"? 308s are known for cooling issues but it seems only with questionable radiators, I had that when I first got my car, the radiator looked fine but it sure didn't cool fine. Working on the radiator and fan side of the setup is generally a whole lot easier than redesigned the pump for whatever that thought it worth to you.


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 Post subject: Re: Water Pump Testing?
PostPosted: Mon Jun 13, 2016 11:50 pm 
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hmm.. it's simple in theory but gets big and cumbersome in reality. Here's a youtube vid of a waterpump test rig...
https://youtu.be/IpmZfC3pNSQ

You'd need at least a 10hp electric motor preferably 3-phase, speed controller, and various pressure sensors and flow meters. Off the top of my head you'd also need to check dead head pressure for various 'rpm' points. Oh and don't forget that you'd also want to test it with the proper water/coolant ratio and at temp for the most accurate results. Suddenly the scope of the project gets BIG and nerdy :geek:

The motor alone is probably around $1k, It might be possible to rig something up for a couple grand. That's a lot to spend to find out if the pump is designed well. Might be cheaper and easier to find an outside facility to test the pump for you.

some googling found this,
http://www.advancedta.com/blog/2014/9/1 ... erformance

Probably not the answer you were looking for.

That said, there are ways to "calc on paper" or virtually to get a rough est. of the pumps capabilities and the flow restriction of the engines coolant system itself. Coolant systems are fairly complex, the flow has to be just right or thermal transfer doesn't happen as it should. And there are many many things to effect that flow.


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 Post subject: Re: Water Pump Testing?
PostPosted: Thu Jun 16, 2016 6:56 am 
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Thanks Mark & Scott, we had the pump test rigs at two of the big industrial engine manufacturers that I worked at in a previous life, but I couldn't remember exactly how they were instrumented.

Wish I had the pressure drop vs flow characteristics of the existing pump & engine cooling system - that would be half the problem solved (identifying if the flow is sufficient).

I went through a pretty exhaustive diagnosis and parts changing a few years ago with my 550, and wound up changing every component in the cooling system except the radiator, which I had professionally, and thoroughly cleaned, and then I inspected the interior with a borescope and the tubes appeared to be VERY clean, with no gunk or calcium left inside. I experimented with pulley ratios and different impellers for the newly rebuilt water pump, but that didn't seem to help.

The issue was the "system" was incapable of getting rid of the heat rejected to the coolant at idle on a hot summer day here in Houston with an ambient of 95-100F, and the top tank temps would climb without stabilizing. I would have to switch the car off when they reached 235-240F, and of course this only exacerbated the problem because the engine would then heat soak. With thermocouples on the radiator inlet/outlet lines, I was only getting perhaps 7-9 degrees deltaT across it (and this was with a squeaky clean radiator and brand new SPAL fans.)

Then I switched from a 50/50 coolant mix to a 90/10 (water/coolant) and I picked up 5-7 degrees more deltaT across the radiator, which dropped my top tank temps, and everything stabilized.

As we know from basic heat transfer, there are several things we can do to improve a cooling system:

1. Increase coolant flow
2. Increase air flow
3. Increase radiator size/efficiency
4. Increase efficiency of coolant

My next approach, once the 6.0 liter engine is finished for the car, will be to increase both air & coolant flow, and increase the size of the radiator, so that I can return to a conventional 50/50 coolant mix, or perhaps even go to an Evans type of coolant, since I've had liner cavitation issues with this engine.

I've been corresponding with Davies, Craig in Australia about using their largest EWP-150 as a cooling "booster" pump in series with the OEM mechanical, in order to improve coolant flow at idle, and that looks promising, however I was hoping I could get the OEM pump flow tested, in order to see really how well it works (or not).

Interestingly, the 550's pump is also used on the 355's engine, so I question whether it's really "man enough" for the 550's 5.5 liter engine, much less the 6.0 liter engine I'll have?

Scott, have those high output 355 engines you do for Nick had any cooling issues?


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 Post subject: Re: Water Pump Testing?
PostPosted: Thu Jun 16, 2016 9:31 am 
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cribbj wrote:

I experimented with pulley ratios and different impellers for the newly rebuilt water pump, but that didn't seem to help.


Then its the radiator or the fan or both. You can't flow more water and not reject more heat right? and you can't spin the pum faster without flowing more water right? and if spinning the current pump faster to make it flow more didn't help then a different pump that flows more won't help either right?

sometimes the answer is way simpler than we try to make it :)

cribbj wrote:
I went through a pretty exhaustive diagnosis and parts changing a few years ago with my 550, and wound up changing every component in the cooling system except the radiator, which I had professionally, and thoroughly cleaned, and then I inspected the interior with a borescope and the tubes appeared to be VERY clean, with no gunk or calcium left inside.


I played the same game with my 308 radiator....had it cleaned, it looked perfect and yet it didn't work well and I heard the same story for several other owners. The radiator was borderline when new and once surfaces in and out were no longer new it just didn't work....whether it was surface finish or more importantly surface roughness or oxide or similar layer from the cleaning process or the paint on the fins I never figured out, but a new larger radiator instantly fixed the problem and I suspect a new oem radiator would have as well.

Get a new radiator before you do anything else and I strongly suspect you won't need to do anything else.


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 Post subject: Re: Water Pump Testing?
PostPosted: Fri Jun 17, 2016 12:06 pm 
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Have a look at PWR's custom built radiators - a plug for an Aussie firm but probably the best there is when it comes to cooling

https://www.pwr.com.au/

And to keep the 550 almost OEM - pull the side pods off the current F1 Ferrari and you will find PWR radiators (and Red Bull and about 50% of the F1 grid, most of Nascar,WRC etc, they know their stuff). And I believe they now have manufacturing facilities in the USA.

John


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 Post subject: Re: Water Pump Testing?
PostPosted: Sat Jun 18, 2016 2:06 am 
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The big engines we're doing also used a monster sized radiator designed around the thermal output of the larger engine. We also use Evans coolant. Straight water would theoretically be best but in practical use it's not, corrosion being the worst problem.

Flow is a tricky one, too fast and transfer suffers, too slow and thermal loading occurs, both of which will have engine temps climbing. The biggest help is reducing surface tension. Unless you expose the vehicle to freezing temps 50/50 mix is not needed. Redline water wetter is more then adequate for temperate climates if you keep to water. Otherwise Evans is the other choice.

I wonder though if the issue is air flow at low speed, the engine is shoehorned and there is zero room for air flow. I'd imagine that once moving along the low pressure under the engine bay helps draw out the hot air and thus improve cooling. a bigger radiator will help but if the overall air flow is poor then it's still going to suffer.


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 Post subject: Re: Water Pump Testing?
PostPosted: Sun Jun 19, 2016 9:17 am 
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islerodreaming wrote:
Have a look at PWR's custom built radiators - a plug for an Aussie firm but probably the best there is when it comes to cooling

https://www.pwr.com.au/

And to keep the 550 almost OEM - pull the side pods off the current F1 Ferrari and you will find PWR radiators (and Red Bull and about 50% of the F1 grid, most of Nascar,WRC etc, they know their stuff). And I believe they now have manufacturing facilities in the USA.

John


Thanks John, yes I like PWR radiators & cores, and the new radiator that will be going into the 550 was made by C&R in Indianapolis, who use PWR cores exclusively. In fact, I think C&R were recently bought out by PWR.


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 Post subject: Re: Water Pump Testing?
PostPosted: Sun Jun 19, 2016 9:21 am 
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Madhatter wrote:
The big engines we're doing also used a monster sized radiator designed around the thermal output of the larger engine. We also use Evans coolant. Straight water would theoretically be best but in practical use it's not, corrosion being the worst problem.

Flow is a tricky one, too fast and transfer suffers, too slow and thermal loading occurs, both of which will have engine temps climbing. The biggest help is reducing surface tension. Unless you expose the vehicle to freezing temps 50/50 mix is not needed. Redline water wetter is more then adequate for temperate climates if you keep to water. Otherwise Evans is the other choice.

I wonder though if the issue is air flow at low speed, the engine is shoehorned and there is zero room for air flow. I'd imagine that once moving along the low pressure under the engine bay helps draw out the hot air and thus improve cooling. a bigger radiator will help but if the overall air flow is poor then it's still going to suffer.


Scott, I really do think it's both air AND coolant flow at low speed and idle. There's just not enough of either one to adequately 1) get the heat out of the engine, and 2) reject it to the atmosphere. I think the long term solution is 1) the bigger radiator as Mark suggested, and 2) better coolant flow at idle, and 3) better fans and a better shroud arrangement (the 550 shroud is not a full coverage design and leaves about 20-25% of the radiator surface uncovered, so no airflow through it from the fans at idle.)


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 Post subject: Re: Water Pump Testing?
PostPosted: Sun Jun 19, 2016 11:16 pm 
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cribbj wrote:
islerodreaming wrote:
Have a look at PWR's custom built radiators - a plug for an Aussie firm but probably the best there is when it comes to cooling

https://www.pwr.com.au/

And to keep the 550 almost OEM - pull the side pods off the current F1 Ferrari and you will find PWR radiators (and Red Bull and about 50% of the F1 grid, most of Nascar,WRC etc, they know their stuff). And I believe they now have manufacturing facilities in the USA.

John


Thanks John, yes I like PWR radiators & cores, and the new radiator that will be going into the 550 was made by C&R in Indianapolis, who use PWR cores exclusively. In fact, I think C&R were recently bought out by PWR.


Actually, if memory serves me, PWR's big break overseas was doing the Prodrive 550 race cars which also used Davies Craig EWP's.


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