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Evans High Performance Waterless Coolant Evaluation

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7 January 2015
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Cape Coral, Florida
Evans Waterless Coolant Evaluation – 1991 NSX Normally Aspirated.

A friend of mine had put me onto Evans Waterless Coolant and its benefits of 0 corrosive properties, less stress on cooling system components due to the fact that it can operate at atmospheric pressure due to its 375deg boiling point, and its ability to not degrade/breakdown over time and therefore last the life of the car. Since it was time to replace all the coolant hoses in my 91 NSX I decided it was a perfect time to give Evans High Performance Waterless Coolant a shot.


One of the problems with water-based coolants is its low boiling point temperature. Boiling coolant has poor heat transfer capabilities so the cooling system is designed to operate under pressure in order for the coolant to operate at a high temperature without boiling. The point at which coolant boils is determined by the coolant to water ratio and the pressure rating of the radiator cap. A normal 50/50 mix with a 15lb cap will boil at 265deg. Increase the coolant to water ratio to 60/40 and the boiling point increases; however, running higher mixes of coolant to water can result in a loss of heat transfer capability due to increased viscosity. 100% water provides the best cooling properties, but it’s corrosive and has a lower boiling point (257deg @ 15psi). Running with pure water with a standard 16lb cap could result in the water boiling in areas of the motor especially around the exhaust valves, which could lead to damage to the valves and large differential temperatures within the motor. Metal temperatures near the exhaust valves reach and can exceed boiling points of the coolant, but boiling along the metal surfaces can be beneficial to cooling as long as it remains in the nucleate boiling state and there is circulation. This is how nuclear reactor cores are cooled and why the bottom a boiling pot of water doesn’t melt (I’m very familiar with nucleate boiling due to my 10 years as a Senior Commercial Reactor Operator). When the surface temps reach a high enough temperature the ability of the circulation system and the coolant to remove the heat is exceeded and the state of boiling changes from nucleate to film boiling. At this point heat transfer rates drop dramatically as a vapor barrier forms between the metal surface and the coolant. Within the head there can be areas where temperatures and poor circulation will result in the phase change from nucleate to film boiling. When this happens there are some drastic temperature differentials that may be experienced along the metal surfaces. When the motor is shut down circulation ceases and metal temperatures continue to rise, which will result in film boiling causing excessive and uneven metal temperatures.

Cavitation from the formation of vapor pockets is other factor that can cause problems with wear and decreased cooling efficiency. The inlet of the water pump operates at a lower pressure than the outlet which results in a lower boiling point for the coolant entering the pump. If coolant temperatures are high enough boiling can occur within the pump resulting in cavitation. Cavitation will cause erosion and reduce the pump’s efficiency. This same low pressure condition can occur as coolant enters small channels or goes through sharp turns.

The point is that any boiling other than nucleate boiling is not good. Being that Evans coolant boils at 375deg, contact between metal and the coolant isn't lost due to the formation of boiling coolant vapor barriers except possibly under extreme conditions; therefore, metal temperatures stay more uniform throughout the motor during operation and after shutdown. Cooling system temperature gauges only provide a broad overview of how the cooling system is performing, but are a poor indication of what’s going on in different areas of the motor.
Evans does have a higher viscosity than water or a coolant 50/50 mix, but modern engines and cooling systems that are in good condition are not affected by the increased viscosity.


The other benefits of Evans:

· Totally non-corrosive
· Does not break down over time
· Operates at low pressure; therefore, reduced strain on cooling components

Detractions:

· Expensive – For an NSX the cost is approximately $395 including 4.5 gallons Evans Prep Fluid, 5 gallons Evans Coolant, and a Refractometer for determining water content. Does not include labor.
· Requires a time consuming complete flush of all water-based coolants. To see what’s involved it’s best to watch the videos on Evans’ website.
· Low Pressure/Hi Volume Air Pump is required to aid in flushing the system. A towable inflatable water toy hi volume air pump or the discharge side of a shop vacuum will work.
· Filling involves the same venting procedure used for any coolant on an NSX.
Note: For those who are interested in converting their cars to Evans I would be glad to advise in the process I went through for draining and flushing the system in order to remove 100% of the water-based coolant.


TESTING – All testing was done with the coolant tank pressure cap loose.
Test Run #1.

· Outside Temps 86deg, no rain, AC max cold.

· Driving Condition: Normal local traffic (stop & go and up to 55mph).
· Dash temperature gauge @ approximately 187deg (one pointer's width above the 3rd 185deg tic), which is within the normal operating range.

· Cylinder head temperature measured with a TACKLife IT-T05 infrared detector 3 minutes after shutdown indicated 173deg.
Test Run #2.
· Outside Temps 84deg, no rain, AC max cold.
· Driving Conditions: Normal local traffic with the majority of time at 55-60mph.

· Dash temperature gauge approximately @ 187-189deg.
· Cylinder head temperature measured at cam level @ 173-180deg.
· Cylinder head temperature measured just below the exhaust manifolds @ 247deg.
· Coolant temperature measured in coolant tank @ 189deg.
Conditions immediately following shut down.
· Cylinder head temperature measured at cam level @158deg.
· Cylinder head temperature measured just below the exhaust manifolds @ 215deg.

Final Test Run #3

· Outside Temps 94deg, no rain, AC max cold.
· Driving Conditions: Normal to no traffic. 3 hours total with 1.5 hours each way at speeds between 60 & 80mph. With numerous full throttle accelerations and 20 sec run at 140 and another at 120mph.
· Dash gauge never varied from 187-189deg
· Cylinder head temperature measured at cam level @ 193deg.
· Cylinder head temperature just below the exhaust manifolds @ 215 +- 5deg (burned myself too many times on the exhaust system trying to get an accurate reading)
· Total expansion of the coolant from cold to hot resulted in an approximately 1 inch increase in coolant level in the Dali tank.



CONCLUSION
At this point I feel that the testing proved that the coolant works as advertised and was well worth the investment and the time to make the conversion. One interesting observation was when I started the car up after stopping for a 15 min break at our ½ way point. The dash gauge read no temperature increase when the ignition was turned on and when the motor started. Usually when you shut a hot motor down and then restart it within a short period of time the temperature gauge will show a pretty sharp increase in temperature due to the lack of circulation within the hot motor. Temperature will return to normal once the cooling system starts to circulate and cools the motor back down.

If you feel inclined to do your own research this will save you some time. Here are links to an evaluation of Evans by a competitor No-Rosion and Evans UK Response to No-Rosion's evaluation. It’s pretty detailed but it should answer any questions you have.



Additional Photos are available here. Evans Waterless Coolant Conversion
 
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