Using Evans Waterless Coolant in Rotary Engines

We often get asked whether Evans High Performance Coolant can be used in rotary engines.  So we have turned to the professionals for some sound advice and based on years of experience.

Pineapple Racing, based in Oregon, USA is one of the oldest and most respected custom engine builders specializing in Rotary Engines. They have been around for over 20 years and are still going strong. Pineapple Racing is a custom engine rebuilder, also specialising stock and performance parts.

Pineapple Racing pioneered using Evans in Rotaries and continues to offer up their observations of how Evans performs in all rotary engines including imported engines.

 

Pineapple Racing Rotary Truck Profile

For over a decade Pineapple Racing have been running Evans in their own rotary engines and well and customer’s cars.   Their very own 1974 rotary truck has had the same fill of Evans for 13 years, no top up, no replacement. With a large tube, high fin count core radiator installed in the stock tanks including the stock clutch fan to best take advantage of Evans cooling properties. On a 37⁰C day up a moderate grade hill it might see a 2⁰C increase in temp.

1974 Mazda Rotary Truck

It is the perfect work truck Rob Golden, engine builder and owner of Pineapple Racing. It has a 3/4ton capacity so 7 or 8 engine cores in the back is not a problem. It handles well for daily driving and with the 6 speed (2010 RX8) it is fun to blast through the gears.  

  • 13B, mild street port with highly modified stock carb and manifold
  • Electronic ignition and internal regulated alternator installed to look OEM
  • 2010 RX8 6 speed
  • Custom radiator based on the stock up/lower tanks with a 3 row, ¾”(19mm) tube and high fin count core. Stock 85 RX7 “dog nose” fan and fan clutch for reduced noise and higher air flow.
  • Custom exhaust system
  • Upgraded suspension including a “J bar” rear end locator

 When using Evans in any rotary engine compatibility with all components and seals are the most common concerns.

Water Seals

Despite using their own specially designed Water Seals, Pineapple Racing originally tested Evans with the OEM water seals. There are no adverse affects to the OEM water seals using Evans.

With conventional water based coolant the OEM water seals fail at about 101⁰C when measured at the stock sensor point in the rear plate. They suggest not to race an engine using conventional coolant above 96⁰C full throttle. A good aftermarket water seal, such as Pineapple Racings HD seals, have been tested to over 115⁰C. That said, customers are always reminded that with Evans, the coolant temperature to engine metal temperature does not correlate the same as conventional coolant. The real world proof is on-track horsepower with higher Evans coolant temperatures. No power drop will be experienced. With conventional coolant there would be a power drop at around 104⁰C.

With higher horse power comes higher loads to the cooling system. Improving the entire system as a team will give you the best results. 

Radiator

Most imported rotaries have small tube radiators.  In the early days, Evans was much thicker and there were issues with flow.  Since then, Evans have re-formulated to a much lower viscosity meaning that Evans will now work well in all OEM radiators.  Keep in mind that the radiator must match the power output/horsepower of the engine, and airflow is essential. A 38mm x 9.5mm tube is recommended for full race applications, smaller 25.4mm x 9.5mm tubes for street applications.

Experience shows that when it comes to radiators, the ability for air to flow through the radiator is vital. Frequently radiators have too high a fin count or too thick a radiator which impedes airflow through the radiator core. This airflow is the heart of the radiators efficiency. For belt driven fans, which all the 1st Gen and 2nd Gen rotary cars were equipped with, radiator design is rarely an issue. For electric fan equipped applications most aftermarket radiators are too thick or have too high a fin count to allow proper air flow through the radiator. Using Evans coolant makes radiator tube sizing less critical, however it is still best to run a large tube diameter.

High horsepower RX3 models RX4 or RPU radiators are suggested.

 HINT   Oil Cooling

In general, for circuit racing or similar, 2 stock oil coolers in parallel may be necessary to control the oil temp. Use a “Y” vs. a “T” splitter to greatly reduce cavitation and heat. Since oil cooler as usually denser than radiators, air tends to go around them more than through them. Ducting a 40mm – 60mm tall layer of air from the radiator opening to the oil coolers will greatly increase their efficiency. After the coolers the air can flow through the radiator. Make the best use of the air you have to let under the car as this air reduces downforce. Do this by sealing air leaks so all the air entering the radiator opening in the front end is forced through your radiators (oil or water).                                                                                                                              

Coolant Pump

The OEM water pumps in the early pre-RX7 rotary cars and the 1st and 2nd Gen RX7's have well designed water pumps with cast impellers. For these applications no additional work is necessary.  If you are fussy and are craving perfection, gently rounding the sharp edges of the impeller will better help prevent cavitation.  While the 3rd Gen RX7 and RX8 have decent water pumps, replacing the sheet metal impeller with a cast or CNC machined impeller is a good idea for racing applications.

Electric water pumps can be used in street or drag racing applications, however quality is key, and maximum flow rate is needed.  Keeping in mind that the flow rate listed on most EWP specifications are measured from one open container to another, not taking into consideration real world conditions such as thermostat restrictions and heat/pressure. 

So can Evans be used in rotary engines?

Evans can be used as a drop in replacement coolant with no other modifications in all the OEM rotary applications.

Experience shows that a properly designed cooling system should not see a coolant/oil running temperature difference Vs conventional coolant.

In applications where a properly designed system cannot be implemented, higher coolant temperatures will result. A good example of this from the track follows.

A 4 core off the shelf aluminium radiator installed into a circuit racing 2nd Gen RX7 with an electric fan replacing the OEM belt driven clutch fan. The Evans coolant would reach 137⁰C within 16 minutes during race conditions. To the credit of how well the Evans coolant works, the engine power loss was not experienced nor did the coolant seals (Pineapple Racing HD water seals) ever fail. This went on for about 6 races. The customer was convinced to re- install his OEM belt driven fan. The coolant temps never went over 90⁰C for the entire 30 min. race. Airflow is king! If the customer had installed a thinner radiator, they would have been fine with the electric fans.

If system limitations result in higher normal operating temperature with Evans, try to keep it below 115⁰C for daily use (using good quality aftermarket seals).

Running Evans at elevated coolant temperatures, the oil temperature will rise. Oil temperatures of 121⁰C should be considered maximum, in oil pan readings. It is recommended that oil temperatures stay within a range of 98⁰C - 105⁰C for best engine life.

If higher oil temperatures are experienced, more oil cooling may be necessary than an application with the coolant temperature better controlled.

In the rotary engine, the oil does 30% of the cooling, hence the reason for the very large oil coolers installed by the OEM.

For example, if a circuit racer does some "agricultural racing" - runs off into the grass, frequently the radiator will be plugged. This will drive the coolant temps up. With the Evans, the racer has the option to stay in the race and monitor coolant and oil temperatures. With a conventional coolant, at 96⁰C the driver should reduce the load on the engine to prevent the temperatures from doing engine damage, always ask your engine builder for the temperature limits your engine should see.

 HINT   Controlling Coolant Temperature when using Evans

With a properly designed system - the Evans equipped engine should run on or very near the thermostat opening temperature.

With a design compromised system - since conventional coolant failed, the customer is looking for a workable solution. This will mean using the Evans ability to run at higher temperatures (without engine damage) than conventional coolant to dissipate more heat, but at a higher working temperature. In rotary engines I recommend a maximum of 121⁰C(250⁰F) with stock water seals or 138⁰C(280⁰F) with our Pineapple Racing HD water seals. When using Evans amazing ability to run at very high temps without a pressured system, you still need to control the oil temperature to normal levels to prevent engine damage.

 So why Evans?

Evans Waterless Engine Coolants are a major step forward in engine cooling technology and are proven to work in the harshest of environments.

Eliminates Corrosion:  Unlike water, Evans Waterless Coolants contain no oxygen or minerals and so eliminates corrosion.

Eliminates Overheating:  With a boiling point in excess of 190⁰C, Evans prevents inefficient nucleate boiling and hot spots caused by pockets of steam.

Eliminates Pressure:  Evans also allows the cooling system to run at a lower pressure which in turn reduces stress on components. When using Evans steam/water vapour is eliminated completely.  The absence of steam reduces system pressure to approximately 5-7PSI.

Eliminates Freezing:  The waterless coolants will not freeze even at temperatures as low as -40 degrees Celsius.

Good for Life:  Evans coolants are designed to last the lifetime of the engine and never need replacing.

Less Toxic:  Owners switching to the new product also have further peace of mind as unlike traditional coolant solutions, it is classed as less-toxic.

 About Evans Cooling Systems Australasia:

Evans Cooling Systems Australasia is a 100% Australian owned company, based in Melbourne, Victoria, continually seeks to improve engine performance and efficiency, and to contribute to a cleaner and safer environment.  For more information on Evans Cooling Systems Australasia and Evans waterless engine coolants please visit www.evanscoolants.com.au or contact us on info@evanscoolants.com.au