Evans Waterless coolant in V6/V8s?

Discussion in 'General Auto Conversion Discussion' started by pfarber, May 23, 2019.

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  1. Jul 14, 2019 #81

    Winginitt

    Winginitt

    Winginitt

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    Sounds simple but like most things its never that easy. Electrical wiring and connections introduce points of failure which can occur without warning. A marginal battery can suddenly become an issue. Simple mechanical driven pumps are very reliable and usually give some indication of problems before failing. I guess what I'm saying is I would prefer something that has a gradual failure probability to something that has more chances of an immediate and unforseen failure. That being said, most things manufactured today are pretty reliable if properly installed and maintained.
     
    Last edited: Jul 14, 2019
  2. Jul 14, 2019 #82

    pictsidhe

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    If I was hell bent on efficiency, I'd do the following:
    Water flow rate proportional to radiator air flow rate. Sensing the pressure drop across the radiator core, as well as air density and pressure could do that. The thermostat would be the radiator exit flap, controlled by a servo from head temp.

    However, that's not simple and adds multiple extra failure points to a vital system. Yes, overrides can be added.

    Less complex, pick the right water pump pulley for best climb cooling. Maybe a servo'ed flap with a blinking big red overheat light and manual override.
     
  3. Jul 14, 2019 #83

    mm4440

    mm4440

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    Hi,They are doing what they can to speed warm up for smog, likely bypass control. I am sure they test thoroughly under adverse conditions. Restrictions on suction side of pumps is not a good idea.
     
  4. Jul 15, 2019 #84

    pfarber

    pfarber

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    The flight profile of an airplane varies wildly. The worst case of taxi in high temps is the real stress test. If you optimize for cruise, then you better hope that you are always #1 for the active.

    Why is cooling so poor at taxi? Well, first is that the water pump simply isn't moving much coolant. The electric water pump solves that. Next is that low air flow can reduce the amount of BTUs exchanged, so now we need a coolant that will not boil or make steam in the head or overpressuize the system. Synthetic coolant solves this, with a small trade off. It will run warmer, but again, we have much more cooling mass being put through the heat exchanger to mitigate the lower airflow. And with proper ducting, capture of propwash and electric cooling fans can by added to increase airflow. So now we have the low air flow problem addressed.

    The addition of cowl flaps allows the optimization of air for high speed cruise.

    That addresses all the typical liquid cooling issues, we have a lighter system that costs us less HP to run, with fewer moving parts.

    I did order about 6 back issues of Contact! where they deal with liquid cooling. Hopefully these articles will help point out anything I've missed or have made incorrect assumptions about.

    Your idea is basically an extension of my thought removing the t-stat completely. Automating the flaps would be the hard part. A PLC and some sensors is all you need electronically.
     
  5. Jul 15, 2019 #85

    Winginitt

    Winginitt

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    It's good that you are investigating other ways to do things, but I think you are following the wrong assumptions for your basis. The coolant side of the systems is factory engineered and tested. It already works well. You don't need to expand the temp range of the coolant so the engine can operate at a higher temp, as that would still be detrimental to the engine over time......maybe even a short time.
    Auto engines routinely idle in traffic jams for hours with a sun baked hood hot enough to fry an egg. The asphalt highway radiates heat up under the engine while its driving an alternator,power steering pump, torque converter, and air conditioning. All of this at an idling speed. There isn't any problem with the coolants ability to absorb heat, the ability of the engine to transfer heat, or the pumps ability to move the heated coolant fast enough. That part of the system is already proven and effective.
    The problem is with the home builder engineering(?) on the air transferring side of the system. If you get the air side of the system correctly designed, you should have a reliable system.
     
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  6. Jul 17, 2019 #86

    pfarber

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    I agree that systems designed FOR A CAR, works well IN A CAR. Installed in a car you can add dual cooling fans, larger radiators, more coolant etc. But all that is extra weight. At 180kts cruise I don't need (or want) a car sized radiator to ensure idle cooling performance. Weight is of little consequence in a car.

    Early attempts of putting a car engine in a home built mostly failed and gave the conversion process the black eye it still has today. Yes, engines from aluminum are lighter, but most successful installs address the cooling system more than any other part.

    My calculated radiator size is 400sq in or ~ 20x20x1. look at the radiator in your car, then figure out how to push it through the air at 180kts. And another thing, the fin spacing in a car radiator is much to close to pass air at high speed. IIRC 2.5mm or more is the best fin height to pass air and increase transfer.

    If you study the problem, water in the engine block creates a ton of issues that simply can be done away with. No more steam tubes, no more steam, no more additives to stop corrosion, no more additives to preserve the water pump, no more overflow tank, pressure cap or pressurized system at all. No more thermostat. That's right. Buh-bye you little wax pellet filled harbinger of engine overheating death. Yes, its much more expensive, but for aviation use I can get rid of almost a dozen issues caused specifically by water in the coolant by switching to synthetic.

    On top of that, BMW has, for years, run electric water pumps. They are replacement items at approx 80k miles. Yes, mechanical ones are pretty reliable, but also have significant issues with low flow, cavitation, and stealing horsepower.

    One thing I will add, if this little experiment fails there is no real issue with going back to a mechanical pump, a pressurized system and a t-stat. The mods don't alter the engine one bit. Its a simple process of bolt on, test, tweak. If its not worth it, then unbolt and make a 'conventional' install.

    At then end of the day I am out maybe $500 (synthetic coolant and electric water pump).
     
  7. Jul 18, 2019 #87

    mm4440

    mm4440

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    Unless you can perfectly fill and seal your system to keep air out you will still need high point vents and an expansion tank. In some racing classes they use an accumulator for expansion and pressure control.
     
  8. Jul 18, 2019 #88

    Winginitt

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    You don't seem to be accounting for the fact that an engine must operate in a limited temperature range with the pressurized boiling point of water being at that maximum allowable point. If you build a system that will not boil even at extreme temperatures, the engine will still be in danger because the oil temp will elevate to the point of destruction.Think about the effects of higher temperatures on head gaskets,exhaust valves and oil and bearings. You don't need to build something for higher temps, you need to build something that has no trouble with staying below acceptable boiling temps.You seem concerned with losing a few hp with the water pump, but in most water cooled conversions you have enough displacement to simply increase the engine speed a 100 rpms and easily offset those HP.
    When you build a cooling system you have to build it for satisfactory operation in worst condition situations. Those conditions are usually while waiting on the tarmac and full power takeoff. If your system needs a larger radiator or redesigned air intake or adjustable cowl flap, then that's what it takes. Making a system that allows the engine to reach extreme temps is not the best solution. That's my suggestion, and I hope you will think about the risks that elevated operating temps pose.
     
    Last edited: Jul 18, 2019
  9. Jul 20, 2019 #89

    tspear

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    Weight is a problem in cars. Aluminum costs more than Iron or Steel. Why have so many models switched to it? Weight; weight hurts efficiency which affects MPG. So cars are sensitive to weight; and have been getting lighter every year for a couple of decades now.

    The impeller (usually) moving the water does not care where the mechanical source comes from. It can be electric, it can be mechanical, it could be thermal expansion for all the fluid cares.
    If you have two identical impellers; one powered directly off the ICE and one powered via an electric motor which pulls power from the alternator. Then the electric will by the nature of physics actually "steal" more power as you transition energy from mechanical to electric and back again. These transformations are not free.

    The only way you can have an electric pump be more efficient is if the pump speed required is non-linear and you expect to operate over a wide range for extended periods of time. As in racing, not something you will run into in a plane.

    Tim
     
  10. Jul 20, 2019 #90

    mm4440

    mm4440

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    Hi, one of the uses for the electric pumps is to keep coolant circulating when the engines are off with the start-stop systems. Might not have the capacity or life for main pump use. I do not have detailed info on their use, so might be in error.
     
  11. Jul 20, 2019 #91

    BJC

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    It sounds like the electrically driven pump being discussed is a positive displacement pump. Is it?


    BJC
     
  12. Jul 20, 2019 #92

    rv6ejguy

    rv6ejguy

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    Tell that to the professional engine designers and engineers of every major OEM in the last 30 years... The same designs work just fine when these engines are heavily boosted to triple or quadruple the factory outputs. There isn't much restriction when the thermostat is open and when it's closed, the bypass is active and provides enough flow to cool the engine during low power or warmup conditions.
     
  13. Jul 21, 2019 #93

    pfarber

    pfarber

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    BMW uses electric water pumps for years. Its replaced as a maintenance item at about 80k miles.

    Its a more expensive option than a $50 mechanical pump, but it also has significant advantages

    No cavitation
    Precise control of coolant based on load
    Uses significantly less HP to run
    Less weight

    Disadvantages:
    Doesn't last as long
     
  14. Jul 21, 2019 #94

    pictsidhe

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    Could you please show some proof or even just physics for your claim that electric pumps don't cavitate, use less power and are lighter?
    They can indeed be highly controllable.
     
  15. Jul 21, 2019 #95

    pfarber

    pfarber

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    No. It is a centrifugal pump with a standard water pump impeller. The main advantage is that at idle/low RPM a mechanical pump is also spinning slowly. An electric water pump allows you to spin at any speed regardless of engine RPM. Its this movement of cooling mass that gives you the 'extra' cooling at low RPM. Historically, low speed/low RPM at taxi is the biggest cause of cooling system failure for E-AB auto conversions.

    You could change the type of pump, even use an external pump (some cars do) because you are no longer tied to a belt for power.

    One of my ideas is to have each head with its own electric pump and radiator. This would reduce pressure and allow for higher flow rates. It would also allow for a 'backup' water pump (using a cross connect) to allow a 'limp home' type mode of cooling.
     
  16. Jul 21, 2019 #96

    BJC

    BJC

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    Thanks. The size and shape of the housing appear not to be those of a centrifugal pump.


    BJC
     
  17. Jul 21, 2019 #97

    pictsidhe

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    It isn't low water flow that causes the poor cooling, it is the low airflow through the radiator. I even posted a spreadsheet for people to play with that demonstrates this. Increasing water flow rate past the optimum will result in less cooling, not more.
    Water has about 4x the specific heat of air. Best cooling will be when the mass flow of water is 1/4 of the mass flow of air through the radiator. Both need to be significantly higher than the mass flow of air through the engine.

    The temp rise of the radiator air for typical engine efficiencies is around 1000*Me/Mr in K

    Me mass flow of air throught the engine.
    Mr mass flow of air through the radiator.

    Note that at idle, engines are less efficient. Thye are consuming much less air and fuel, so will still need less cooling than when actually working.

    Yes, you can run the engine much hotter and use a smaller cooling system, but you need an engine that CAN run much hotter without an early death. Modern aluminium car engines are very unlikely to do that. A lot of them, such as newer GM, use heat treated aluminium heads. Those will soften and creep if run hot. The fix after they blow their head gaskets is not to skim them, you have to replace them.
    You would be much better off designing a low drag cooling system than trying to run an engine really hot. Have a look at the Meredith effect. Homebuilts are unlikely to get any thrust, but some attention to detail does dramatically reduce the drag over a crude system. Look at systems that are proven to work, not ones that defy their physics.

    Wen I have a new and totally awesome idea, i try to find out why nobody else has thought of it. If a whole bunch of people with relevant practical experience tell me why, they are generally right...
     
  18. Jul 21, 2019 #98

    pfarber

    pfarber

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    You're jumping in mid way and most of these questions have been answered. Please re-read the entire thread and if you still have questions I'll try to explain.

    Please read this (sorry if its a little basic, not sure of your level of understanding) http://ricksfreeautorepairadvice.com/water-pump-cavitation/

    Electric water pump cavitation can be controlled because it's operated independent of engine RPM. My physics is simple. By not spinning the impeller faster than required, I can eliminate cavitation. In the Navy we detected cavitation with hydrophones, not math. If you wanted to be 100% sure, you could rig up a cavitation sensor (like a knock sensor) and a plc and eliminate caviation. My solution is vastly simpler. If you run the electric motor in proportion to cooling need, not engine RPM, you can eliminate the impeller overspeed and cavitation.
     
  19. Jul 21, 2019 #99

    pfarber

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    External water pumps can use whatever they want. Compare a Mezier to a Davies Craig. Both use centrifugal impellers... but different styles.

    Heres a video of the Meziere pump jump to 0:45 for the money shot.
     
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  20. Jul 21, 2019 #100

    pfarber

    pfarber

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    Yes, cooling air is required. I'm kinda sad that this is not obvious.

    Do this simple test. Start your airplane (you have one, right?) and then stand behind it at idle. You'll be surprised that a propeller is pretty good at moving air, even at idle! I KNOW, CRAZY RIGHT!!!??!!?! So lets pretend that we will, at idle have a source of cooling air.

    Now the issue is that the WATER PUMP, at idle, is not moving enough coolant. Why? Because its directly tied to engine RPM. So you're idling at 600 RPM. Maybe you're moving 5-8GPM. Why? Slow impeller speed means low flow rates. Now, what if I told you that at idle, you can move 55gpm (or less, if needed)? Do you not think, all thing being equal, that the higher coolant rate will remove more heat from the engine? Say yes.

    You seem to be stuck on the idea that simply moving more mass will not result in any additional cooling. But step one is GET THE HEAT TO THE RADIATOR. If you simply are not moving enough mass THROUGH the radiator then you are leaving it in the engine. THIS IS THE PART YOU ARE MISSING. REALLY. PLEASE SAY YOU UNDERSTAND THIS.

    So no, I don't need some wacky spread sheet to understand that if the coolant never makes it to the radiator, it cannot be cooled. At idle, the issue is not the delta of the radiator. The issue is that the coolant isn't making to the radiator.

    At cruise, you have the exact opposite condition. At 5000RPM you are moving to much coolant, the t-stat restricts flow to modulate flow(temp). What if I told you that by modulating the RPM of the coolant pump you can remove this restriction and actually increase the flow rate by removing a restriction (pumps create flow, restrictions create pressure). Which also helps with low speed cooling.
     

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