Evans Waterless coolant in V6/V8s?

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

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  1. Jun 15, 2019 #21

    pictsidhe

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    Next time, just report it? Now we need to ask a mod to remove your post saying that you reported something that is no longer here. Which is now as off topic as this one!
     
  2. Jun 16, 2019 #22

    pfarber

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    I'll just leave this here. Hopefully you'll read it.

    HBA Code of Conduct

    1. Participate - Be yourself, have fun, invent, innovate, chat, plan, day-dream, and enjoy any other activity associated with this wonderful sport.

    2. Respect Others
     
  3. Jun 16, 2019 #23

    Himat

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    I would consider this a moth point, if the pressure in an engine cooling system burst a hose, the hose is defective anyway. My impression is that leaks in a pressurized engine cooling system seem to come from lack of maintenance on well-engineered systems.

    Evans proclaim their coolant do prevent corrosion due to water in the cooling system. Now, water is not necessary to make an electrolyte to get galvanic corrosion going. Other chemistries are possible. Engines are designed for the standard coolant/antifreeze, with bad luck you just replace known failure modes with unknown failure modes.
     
  4. Jun 29, 2019 #24

    pfarber

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    One issue I can see being a problem that auto engines have is core plugs (you may know them by the very wrong term of 'freeze plugs'). Not having any pressure would reduce this. Also the various seals and gaskets, hoses and fittings in the system would have zero pressure and you have few failure modes to consider. With zero galvanic corrosion issues head gaskets should last to whatever TBO you set.. definitely 1000 hours. Gone would be the worry of coolant jacket clogs.

    Also, since the synthetic coolant can operate safely above the boiling point of water, you never have to worry about it. It simply boils off through the vent. You completely remove the single largest catalyst to galvanic corrosion. Most of the additives in 50/50 are there to stop the problems water creates.

    The only reason we have a t-stat in a motor is to control the water temp. Removing the 212F limit allows the engine to run hotter which is actually a good thing. If you remap the the engine to run hotter, it actually runs better (of course there is a limit, but the 212F is only there for the water).

    While these may seem like 'less than 1% chance of actually happening' issues, ruling them out with a simple coolant change is well worth the expense. Yes, 50/50 coolant may cover you 95% of the time... but for the one time cost of a synthetic coolant you are in the 99.999% range.

    So yes, I agree that these are really 'worst of the worst case' scenarios. But that's what aviation safety covers. On a cost vs reliability standpoint for $250 you eliminate, yes ELIMINATE so many (agreeably small in actual probability) failure modes.
     
  5. Jun 29, 2019 #25

    rv6ejguy

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    Design a proper radiator system and use 70% water, 30% EG and a bit of Redline Water Wetter. I ran Evans for 6 years, didn't like it (ran hotter)and went back to water/EG. I use a 17 psi cap, stock water pump and dynamic vent line from the highest point in the engine to the header tank. I can idle indefinitely on the ground at +27C, coolant never exceeds 180F in the climb. 16 years of use and no corrosion, no leaks, no blown hoses.
     
  6. Jun 29, 2019 #26

    pfarber

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    27C idle is 80F. Is that a correct number?

    Evans is not a drop in replacement for water. So temp rise would be normal.

    Planning for worst case doesn't mean it will happen, only that you take steps to mitigate it actually happening. Cooling and coolant issues are the #1 reason auto conversions fail. Do you not agree? And since I am using a new, untested motor, taking lessons from dissimilar setups would be, at best, a recommendation.

    Think about all the weigh that can be removed by going pressureless... no more overflow tank and hoses, no more pressure cap. No risk of leaks due to fatigue. All pluses, with very few minuses.

    New, factory rebuild motors die all the time. The stat I hear is that the first 500 hours are the most dangerous for certified motors. And since they cannot make any changes without the cost of certification, they have to live with the limitations. As E-AB I have no such restrictions. So reducing weight, increasing performance and mitigating as many risks as possible is my main goal. Items like electric water pumps and synthetic coolant have been time tested in factory automobiles for decades. Its time those advancements make it to the E-AB world.
     
  7. Jun 30, 2019 #27

    tspear

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    1. Why do you think temp rise is optimal? Auto companies spend millions to get almost every last efficiency they can for EPA and competitive reasons. Why would they be wrong?
    2. A larger radiator likely offsets the weight savings you mention.
    3. Weight is the enemy of fuel mileage in cars; cars have been getting progressively lighter over the years. Therefore if a pure EG solutions like Evans was better, auto companies would use it.

    Tim
     
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  8. Jul 5, 2019 #28

    pfarber

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    1. IC engines like it hot. The limiting factor is head temps and steam (coolant flashing off). Even at pressure, 50/50 still boils at 260-ish. Synthetic coolant is find up to 375. No steam, hotter temps, better efficiency (an ECU would need to be programmed), or just let it ride if you use a carb.
    2. 20% more radiator is what is cited. But many people (cars) use it without a new radiator and it works fine. Since most cars use mechanical water pumps, at low/slow speeds there is not enough flow. Since I will be using electric water pumps I will have full flow at low speeds my initial plan is to run a 'standard' sized radiator. I also plan on other efficiencies to make up for it. If ground testing shows I need a bigger radiator, its a small expense.
    3. Weight is the enemy in airplanes. By bringing the cooling system in 2019 (electric pumps, pressureless coolant) I think there are significant weight savings and performance gains to be found. Electric water pump saves ~15lbs. Lithium battery saves 10lbs+ removing the overflow tank and extra coolant could save another 5-10lbs. Who doesn't want to chop 20-30lbs off their AC as long as it works??

    On the engine stand I will have probes at several places to monitor and calculate temp deltas. The goal is to reduce weight and increase reliability. So far no one has mentioned anything that is a show stopper. The bigger radiator is a concern, but if may not be that big an issue considering what is gained.
     
    Last edited: Jul 5, 2019
  9. Jul 5, 2019 #29

    rv6ejguy

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    PSRU issues are probably #1, cooling #2 but it's near the top for sure. These issues are usually caused by air remaining in the system I've found (been doing this stuff now for 20 years with hundreds of customers).

    You won't lose any weight as the extra rad volume needed with Evans will be made up in coolant weight and a bigger rad/ heavier ducting. You will have more drag from the bigger rad too so that decreases performance.

    Evans works, I flew with it for 6 years but there is no magic there and cooling performance and weight was inferior to using conventional EGW. Think again why the auto OEMs don't use it. Think why RR went from similar 100% EG to an EGW mix to improve cooling margin in 1942 or so as Merlin engine power was steadily being increased.
     
    Last edited: Jul 5, 2019
  10. Jul 5, 2019 #30

    rv6ejguy

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    Engines are not designed to run at 300F. You'll find out pretty quickly what happens if you do. Cars of today have massive cooling margin. You can't fit rads that size in your plane without more weight and packaging problems.

    Ground testing only shows the cooling margin on the ground which is important but may have no bearing on climb cooling.

    You won't save any significant weight with an electric pump, certainly not 15 pounds and as I've stated, performance will be reduced, not increased, using Evans. I know, I've done it so I'm not speculating here.

    My pump weighs just shy of 3.5 pounds but also contains the timing belt idler pulley, tensioner mount and thermostat housing so would be difficult to eliminate those things. Call the actual weight 2.5 pounds.

    Yes, my ground cooling test was run at 27C which is 80/81F. I'm in Canada and it rarely gets over 85F here. The point was, very few Experimental liquid cooled aircraft can ground cool for this length of time without electric fans and certainly not with the small inlet area I have.
     
    Last edited: Jul 5, 2019
  11. Jul 5, 2019 #31

    pictsidhe

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    You will need a larger radiator which is more weight and drag. You will need to re-optimise coolant flow rate. You will still need a header tank as Evans/EG also expands when hot. Car engines are designed to run at 50/50 coolant temperatures. Increase it, you are very likely to be pushing the metallurgical limits of current highly optimised engines. There is a reason that air cooled engines use different alloys than liquid cooled engines. I know that there are engines that use a heat treated cylinder head alloy that will soften at 300F. Evans would result in a replacement head being required, not just a change back to the specified coolant.

    If you want to experiment, go ahead. But telling those of us who have already successfully worked on our own cooling systems that we must be wrong when you have only read adverts, is not convincing. Ross is the foremost authority on auto conversions in here. Many others have done quite a bit of greasy-hand work, too.

    Perhaps this thread should be in manufacturer announcements?
     
  12. Jul 6, 2019 #32

    mm4440

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    I believe Rotax recommended Evans in the 912 series after problems cooling the engines in low speed pusher applications. Not enough airflow through the radiator led to boiling in the cylinder heads and engine failures. Evans will run hotter without steam vapor blanketing. The higher coolant temps with glycol allow increased heat dissipation from the radiator for a given airflow. The Devil is in the details. Water is an excellent heat transfer fluid until it turns into steam. At Wright Field between the Wars, they were able to cut radiator size (and drag) in half running at 250 F with glycol. I think they were running unpressurized water at the time. Many car engines have higher than 180 F thermostats. Many racers run water at much higher pressures than street engines to suppress boiling in the heads. Engineering, in part is dealing with pesky details. Running an engine hotter will reduce power due to increased heat transfer to the intake charge. Racers often run 160 F thermostats for more power. Run hot with less drag or cooler and have more power. No free lunch with physics.
     
  13. Jul 6, 2019 #33

    pictsidhe

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    Cooler temps can help power. The amount varies with engine. But running cooler also tends to accelerate wear. Wear doesn't help power.
    Rolls Royce found that they could stop overheating and also radiator size after changing from pure glycol to a water/glycol mix. There are lots of devils in the details. When I was trying to ameliorate my overheating car, I found that speeding up the water pump made the problem worse, not better, as seems 'obvious'. It was 15 years before I found the maths to explain that. I have failed to explain it on HBA, but I have watched the temperature fall then rise again while throttling coolant flow with a gate valve after finding the maths. There is most definitely an optimum coolant flow, should you test it, or do the maths ;). It does depend on radiator air flow, just to make things more obscure. More air flow is always better for cooling, but not for drag...
    Corrosion? My truck is 25 years old and has the original radiator. I'm guessing that the coolant has been changed when it should. Do that, AND KEEP THE OUT, corrosion is not a problem. 20+ year cooling system life is quite normal now. An ex-boss had a panel van with a leaky pressure cap. I tried to tell him that oxygen would dissolve in the water and rot the sytem. Oh boy, did I change a lot of parts on that thing.
     
  14. Jul 6, 2019 #34

    rv6ejguy

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    Extremely low temps may accelerate wear because of clearance mismatches on the pistons to cylinder walls and not getting the oil hot enough to get rid of condensation which can form nasty and corrosive compounds but anything over about 180F or so is fine (given a decent run duration) and most thermostats in modern cars are set to maintain 190-205.

    Speeding up the water pump may cause cavitation which would actually reduce the volume pumped. Pumping more coolant will always increase heat rejection, especially if it takes flow from laminar to turbulent which scrubs the surfaces to reduce boundary layer shielding and increases heat transfer even more. Higher mass flow, all else being equal, means higher Delta T and higher heat transfer rates.
     
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  15. Jul 6, 2019 #35

    rv6ejguy

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    The devil is in the details however my flight data suggests that that no, Evans, even running at higher temps, is not more efficient than 30/70 EGW, in fact quite a bit worse. Look at the specs on thermal conductivity. If I recall, Evans is about 38% worse than 30/70 EGW. You'd have to run it about 275F compared to 200F for EGW to have equal heat transfer rates. Unfortunately running the coolant here will be bad for engine longevity and may increase the likelihood of pre-ignition. We as homebuilders, can't easily increase the metal temps in the heads without a lot of thought and revised clearances and materials.

    Modern race cars actually run the coolant pretty hot to reduce drag (smaller rad possible) and increase power. More is done to reduce heat transfer to the intake charge by proper intake design.
     
  16. Jul 6, 2019 #36

    pictsidhe

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    Ross. Next time you have an engine on the dyno or swinging a club, reduce radiator airflow to barely enough. Then slowly reduce coolant flow by clamping the top hose in stages. Then see how much air is barely enough to keep head temp (not coolant) at thermostat wide open. Or pull the thermostat and watch the head temp instead of messing with air flow. You may find the experiment enlightening. Or, get hold of a copy of Kays and London and flip to page 27.
     
  17. Jul 6, 2019 #37

    rv6ejguy

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    I actually looked up the numbers at work here today:.

    Thermal conductivity EG /PG= .00055, EGW 30/70= .0012
    Specific heat EG= .574, PG (Evans)= .60, EGW 30/70= .95

    The boiling point of 33/67 EGW with a 15 psi cap is 257F which is higher than you should be running anyway.
     
  18. Jul 6, 2019 #38

    pfarber

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    Making a PRSU is just not something I want to do. There are very reliable units out there that fit the bill. Right now my eye is on a Stinger PSRU. I like that they have a 'softdrive' but I would rather a clutch. Right now they fit the bill at my price point.

    I know that the radiator size is a POSSIBLE downside. Without knowing the specific configuration of the cooling systems already tested (sq in of rad, rows, pitch of fins, single or double pass, Al or brass/Al, etc etc) these statements are not very informative.

    From what I can figure, increasing the coolant flow could possibly offset the thermal inefficiency of the synthetic coolant. Using a single pass, horizontal, two row aluminum radiator with an electric water pump I should be pumping more GPM than stock at cruise.

    From what I can find, and LT1 water pump pushes .17 gal/min/hp Assume that the LV3 is 3/4ths of the LV3 is based off the LS block, but really there is not much difference between the LS and LT engines (besides the switch to all Al).

    Figure 285hp @ 5300 RPM thats 285*.17 48GPM at 5300 RPM (48GPM is probably high as the LT1 water pump is larger). Limiting HP to 200hp (4200RPM-ish) lowers it to 34GPM. A 55 GPM water pump should move heat away fast enough to stabilize the temp without the increase in radiator size. Again, the LT1 pump is larger than the LV3 pump so I would expect lower GPM performance with a mechanical pump. If I move 30-40% more coolant I should increase the cooling rate enough to mitigate the 20% radiator increase. I will also see if the engine tuner can adjust the ECU to not thow a code or enter limp mode if the motor sees higher temps. Running between 200-240 should not be a problem. The only limits we have now are due to the 50/50 mix engines run now.

    Along with ceramic coated headers and a sane intake/cowl flap setup my initial designs put the radiator under the motor with a combo of chin/cheek scoops to move air. I believe I can keep the engine cool without a belly scoop.

    Comparing this to Rolls Royce is a non-starter, please stop. Also car companies need to make a profit. Ford made over a million F150s in 2018. Do you think they want to add $100-$200 (x 1,000,000) to the production costs for synthetic coolant when 50/50 works well for a few dollars? Profit is their motive, not making the best vehicles. Comparing a one-off experimental motor to the entire production capacity of a car manufacturer for what reason now??

    Ninja-edit - Louvered fins may also help.. but concerned about drag.
     
    Last edited: Jul 6, 2019
  19. Jul 6, 2019 #39

    pictsidhe

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    You're right. I'm sure that Rolls Royce were also just trying to save a few pennies on their aeroplane engines. Not like they were trying to save the free world from being overrun.
     
  20. Jul 6, 2019 #40

    pfarber

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    Stock water pumps suffer from this now, and almost no flow at idle. So I think one of the first improvements would be to switch to an electric water pump that has removed these two limitation OR at least switch to a close tolerance impeller with a sweep to eliminate the pump inefficiency.

    I would think you want turbulent flow. Laminar flow would create a slow moving insulating layer that decreases heat transfer.

    All things equal, more fluid flow moves more heat removal. Even if EWC has less thermal capacity than 50/50, more moving mass removes more heat. Yes, effectively you are simply fighting to return to the same cooling performance as 50/50, but once there, you get a lot more benefits: no corrosion, higher flash point, run an un-pressurized system (less weight - no expansion tank or hoses).

    Yes you can simply run 50/50. Feel free to do so. But I think a thorough re-think of automotive conversion cooling is long overdue.
     

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