There are two significant fuel saving techniques for Heavy Duty Engines:
- Use Evans Waterless HD Thermal Coolant to reduce fan-on time.
- Use Evans Waterless HD Thermal Coolant to increase the thermostat temperature.
The following points provide case studies and reports to explain how Evans increases fuel efficiency.
A. The engine fan is a significant consumer of fuel.
It is well-known that the fans for heavy duty diesel engines draw considerable horsepower. Cummins, for example, in its MPG Guide (February 2007), discloses that the fan for an ISX engine draws 17, 26, 37, 52 and 70 HP at 1300, 1500, 1700, 1900 and 2100 RPM, respectively. These horsepower numbers may be converted to fuel rates by the following methodology:
1 horsepower equals 2545 BTU/hour
1 gallon of diesel fuel contains about 139,000 BTU.
In a diesel engine, about 1/3 of the energy in diesel fuel is converted to horsepower. Each horsepower produced therefore requires a delivery of 7635 (three times 2545) BTU per hour from the fuel.
Each fan horsepower therefore requires a fuel rate of 7635/139000 = .055 gallon per hour.
The per hour fuel rates required by the Cummins ISX engine radiator fan for various engine speeds are shown below.
It is clear that minimizing fan operation leads directly to significant fuel savings. In the typical stock configuration, a fan clutch engages the fan in the coolant temperature range of 200o to 210o F. This report describes how Evans waterless HD thermal coolant (“HDTC”) enables the fan temperature to be safely raised, reducing fan-on time and resulting in reduced fuel consumption. When the fan-on temperature is raised, there is always a fuel savings.
A case study – The fan-on temperature was raised to 230o F. Fuel consumption dropped 5.5% during the spring 2008 test period and 8.5% during the summer 2008 test period.
The tests were conducted in Connecticut on two 2006 Mack Model MR688 trucks, both equipped similarly and having Mack E7 350 horsepower engines. One truck was retrofitted and the other kept in the stock configuration (water-based coolant and stock fan settings) for comparison. Both trucks were operated under similar conditions. (More information is available upon request.)
From Fuel Economy Report dated April 29, 2008 (Spring Period) The following data was collected during April 2008 Baseline data from Control truck:
| Eninge Hours: | 27.6 hrs | A |
| Fan-on Hours: | 8.0 hrs | B |
| Fuel Consumed during Period: | 131 gal | C |
| Baseline Fuel Rate (C/A): | 4.75 gal/hr | D |
| (1) Avg engine baseline HP (D * 18.2): | 86.38 hp | E |
| Avg horsepower as percent of rated HP (E / 350): | 24.7% | F |
| Percent of time fan is on (B/A): | 29% | G |
| Engine Hours: | 25.2 hrs | H |
| Fan-on Hours: | 2.5 hrs | J |
| Percent of time fan is on (J/H): | 9.9% | K |
| Estimated engine RPM when fan is on: | 1550 RPM | L |
| (2) Fan HP at est avg engine RPM when fan on: | 25.1 hp | M |
| Fan HP as a percent of avg engine HP (M/E): | 29.1% | N |
| Percent of baseline fuel used by fan during baseline (G*N): | 8.43% | P |
| Percent of baseline fuel used by fan after retrofit (K*N): | 2.88% | Q |
From Fuel Economy Report dated July 11, 2008 (Summer Period) The following data was collected late June-early July 2008 Baseline data from Control truck:
| Eninge Hours: | 151.2 hrs | A |
| Fan-on Hours: | 77.2 hrs | B |
| Fuel Consumed during Period: | 781 gal | C |
| Baseline Fuel Rate (C/A): | 5.17 gal/hr | D |
| (1) Avg engine baseline HP (D * 18.2): | 94.01 hp | E |
| Avg horsepower as percent of rated HP (E / 350): | 26.9% | F |
| Percent of time fan is on (B/A): | 51.1% | G |
| Engine Hours: | 133.8 hrs | H |
| Fan-on Hours: | 25.5 hrs | J |
| Percent of time fan is on (J/H): | 19.1% | K |
| Estimated engine RPM when fan is on: | 1550 RPM | L |
| (2) Fan HP at est avg engine RPM when fan on: | 25.1 hp | M |
| Fan HP as a percent of avg engine HP (M/E): | 26.7% | N |
| Percent of baseline fuel used by fan during baseline (G*N): | 13.64% | P |
| Percent of baseline fuel used by fan after retrofit (K*N): | 5.09% | Q |
The fuel economy figures shown above are for a trash-hauling truck. Refuse trucks repeatedly start and stop and frequently perform service in circumstances that lack ram air. A truck’s use and its working environment determine the amount of baseline fan-on time. The greater the baseline fan-on time, the greater are the opportunities for reductions in fan-on time.
B. Additional Fuel Economy is Available by Increasing the Actuation Temperature of the Coolant Thermostats to 230° F.
In January 2009 Auburn University’s PAVE Research Institute at Opelika, Alabama performed a fuel consumption test according to SAE J1321 (TMC RP-1102) Type II procedures under the direction of technical consultant Bob Rosenthal. Use of Evans waterless coolant and 230° F thermostats showed a fuel economy improvement of 3.04 percent!
The test was conducted with the coolant fans of both the test truck and the control truck locked 100% “on” in order to eliminate the fan from being a variable. In other words, the 3.04 percent improvement in fuel economy from using the 215° F thermostats is in addition to whatever savings are obtained by increasing the fan temperature to 230° F.
The full SAE Type II test report is available from PAVE’s website here.
C. A discussion of what Evans Waterless HDTC is and how it works as compared to water-based coolants:
All commercially available automotive antifreezes and coolants (more than 250 brands), except Evans coolants, are water-based. Water is good because it is cheap and because it has excellent thermal conductivity in its liquid state. On the other hand, water is a poor choice because the boiling point of water is too low. There is very little separation between the operating temperature of the coolant and the boiling point of water (for the pressure of the system). The boiling point of water is the failure temperature for a cooling system using a water-based coolant because water vapor has almost no thermal conductivity. Water is aggressive toward cooling system metals. Water acts as an electrolyte, promoting electrolysis between dissimilar metals within the cooling system.
Although water-based coolants are mostly 50% glycol and 50% water, the failure temperature is the boiling point of water, not the boiling point of the mixture. Some locations within the cylinder head generate so much heat that some of the nearby coolant boils, even though the bulk coolant is below the boiling point of the mixture of glycol and water. When local coolant boils, the resulting vapor is nearly 100% water vapor because of fractional distillation. The water portion is far more volatile and is liberated as water vapor. The glycol portion remains in the solution.
If the coolant that is surrounding the water vapor is above the boiling point of water, the water vapor cannot condense. Under this condition, the water vapor makes an insulating barrier between hot metal and liquid coolant, causing the temperature of the metal to spike to high levels. Graph 2 compares the thermal conductivity of Evans Waterless HDTC to the liquid and vapor phases of 50%/50% EGW.
Water-based coolant must be kept cold enough to avoid pump cavitation. Action of the coolant pump creates a low pressure area at the pump inlet. Pump cavitation occurs when coolant near its boiling point encounters the low pressure area and flash vaporizes within the pump. The gas pocket in the pump causes the pump to stop functioning and coolant circulation to stop. Coolant pump cavitation leads directly to catastrophic cooling system failure with the coolant being expelled from the system as steam pressure exceeds the pressure relief setting of the cap.
Water-based coolant must be kept cold enough to avoid afterboil. Afterboil occurs after shut-down of a stressed engine when the coolant is near its boiling point and residual heat remains in the cylinder head or in an auxiliary circuit such as an EGR cooler. Upon shut-down the coolant pump ceases to circulate coolant through the cooling system. Residual heat boils the stagnant coolant, making steam pressure that exceeds the pressure relief setting of the cap. Coolant is pushed out of the system.
A cooling system using water-based coolants is burdened by the requirement to keep the coolant below the boiling point of water for the pressure of the system under all operating conditions and after shut-down. This task is difficult because the coolant frequently operates close to the boiling point of water.
The primary purpose of any engine cooling system is to keep engine metal temperatures under control. In order to accomplish that with water-based coolant, significant energy must be expended to keep the coolant cold enough so that it remains functional. The most important operational feature of Evans Waterless HDTC is its huge separation between the operating temperature and the boiling point of the coolant, on the order of at least 100o F. [HDTC boils at 375o F (at atmospheric pressure) and freezes below -70o F.]
Graph 3 compares the boiling points of HDTC, 50/50 EGW and water:
The huge separation between the operating temperature and the boiling point of Evans HDTC unlocks a Reserve Capacity that already exists in systems designed for water-based coolants. Any cooling system designed to keep coolant below the boiling point of water for the pressure of the system under all operating conditions and after shut-down is liberated from those requirements when the coolant is changed to Evans HDTC. The same sized cooling system can accommodate a broader range of temperatures safely. When ambient temperatures happen to be higher, there are no failures due to the boiling point of water. In a 100o F environment a radiator that is 230o F can dissipate 22% more heat than the same one at 205o F.
Evans HDTC prevents hot spots in the engine. The huge separation between the operating temperature and the boiling point of Evans HDTC, on the order of at least 100o F, provides an environment where any locally generated coolant vapor immediately condenses into adjacent liquid coolant. Vapor cannot build into an insulating barrier and contact between hot metal and liquid coolant is maintained at all times. Metal temperatures are under control at all times.
Evans HDTC prevents afterboil because of the huge separation between the operating temperature and the boiling point of Evans HDTC. After shut-down, the coolant acts as a heat sink into which heat from hot metal parts of the cooling system can dissipate. Boiling is avoided and there is no build-up of pressure to force coolant out of the system. Stresses on cylinder heads and EGR heat exchangers are avoided as metal temperatures are kept under control.
Evans HDTC prevents pump cavitation, again because of the huge separation between the operating temperature and the boiling point of Evans HDTC. The low pressure area of the coolant pump is never at a low enough pressure to flash vaporize Evans HDTC. The pump never gets vapor bound and has the capability to pump coolant over a broader range of temperatures.
Evans HDTC prevents cylinder liner cavitation erosion in heavy duty engines. As the piston moves inside the cylinder there is vibration of the liner. The vibration of the liner against the coolant alternately makes low and high pressures. In systems using water-based coolant, vapor is created by flash vaporization during the low pressure instant. During the adjacent high pressure instant, the vapor collapses against the cylinder liner. This action is repeated at the frequency of the vibration, causing an attack against the metal liner. Cavitation erosion of the liner is a consequence of this action.
With Evans HDTC there is a huge separation between the operating temperature and the boiling point, on the order of at least 100o F. The operating temperature of the coolant is so much lower than the boiling point of the coolant that the flash vaporization does not occur during the low pressure instant and so there is no collapse of vapor during the high pressure instant. In this manner, cavitation erosion is avoided. In a recognized test (the “John Deere Engine Cavitation Test”) performed in April 2009 by a third-party laboratory, the results using Evans HDTC were so good that no water-based coolant formulations, even ELC formulations, regardless of additives or SCAs, come close.
Evans HDTC waterless coolant is an engineered fluid formulated from a proprietary blend of glycols and compatible additives. It will last the life of the engine as long as it does not become contaminated with water. The coolant does not require supplementary coolant additives (SCA’s) or filters that release additives. It contains no additive that requires water to dissolve the additive or to enable the additive to function.
In heavy duty diesel applications the water content is required to be no more than 3 percent. The most preferred installation of the coolant is into a dry engine and radiator. The water content can readily be determined by use of a refractometer. Any “Brix scale” refractometer may be used if it includes the range 50-60 degrees Brix. The following are refractometer readings of Evans HDTC with corresponding percentages of water content:
| Brix Reading | Percent Water |
| 55.70 | 0 |
| 55.00 | 1 |
| 54.70 | 2 |
| 54.40 | 3 |
| 54.00 | 4 |
| 53.50 | 5 |
Evans HDTC is low in oral toxicity. Although HDTC contains ethylene glycol, it also contains a substance that inhibits the metabolism of ethylene glycol, preventing its toxic metabolites from forming. In tests on rats according to EPA regulations, no rats died eating the ethylene glycol/inhibitor combination, even in quantities that completely filled the stomachs of the rats, indicating a very low toxicity. Evans HDTC carries ethylene glycol warnings on its packaging because of the U.S. Consumer Products Safety Commission requirement that all products containing over 10 percent ethylene glycol carry such warnings. Permission to waive the labeling requirement requires proof of safety by in-vitro testing on human tissue. The in-vitro testing is underway and is expected to be completed during 2009.
D. Maximizing the Fuel Economy Potential Means 215° F Thermostats, 230° F Fan-On Temperature, and Reprogramming of the ECM
Raising the thermostat temperature to 215o F requires the use of prototype thermostats that Evans Cooling Systems can arrange to provide. At 215o F there is huge separation between the boiling point of the coolant and the operating temperature of the coolant. The engine will not overheat and there will be no loss of control of metal temperatures.
Low fan temperature settings cause extended “fan-on” intervals as compared to higher fan temperature settings because heat transfers more efficiently from a hotter radiator to the ambient air than from a cooler radiator. The fan does not have to run as long to transfer the same amount of heat. With Evans HDTC there is ample capacity for the coolant to absorb residual heat from both the cylinder head and the EGR cooler without causing boiling or afterboil problems. With HDTC the fan temperature can be safely increased to 230o F, reducing the “fan-on” time.
The engine’s ECM requires re-programming of several items in order for the system to function without interference. In addition to the fan-on temperature, the fan-off temperature must be adjusted upward. De-rating and automatic shut-down temperatures must also be increased. The following temperature settings would be reasonable:
| Fan-on | 230o F |
| Fan-off | 220o F |
| Derating | 235o F |
| Shut-down | 240o F |
E. Why Aren’t the Engine OEMs Already Using Waterless Coolants?
In the foregoing it is explained how the features of Evans HDTC are superior to water-based coolants and how HDTC enables innovative techniques that save fuel. This section addresses the question, “If HDTC is so great, why is its use not widespread throughout the heavy duty engine industry?” In simple terms, the engine OEMs have been comfortable with existing cooling system arrangements. If no OEM moves, then no OEM has to. Everybody uses giant radiators and amazingly powerful radiator fans. OEMs have their own private-label products and at least one OEM has a major subsidiary producing its recommended consumables.
OEMs have requirements for coolant that fit only water-based blends. The ASTM testing methods for coolants are usable only for water-based products. Evans HDTC can pass ASTM standards but the test methods require modifications appropriate for waterless coolants. The factor keeping the OEMs in control of coolants for their engines has been the engine warranty. The threat of engine warranty invalidation has been the club by which the OEMs control their customers. But something has changed.
The change is the economic value of fuel economy. Five-dollar diesel was a wake-up call; the price has come down but the memory persists. Fleet owners are deciding that it is not worth thousands of dollars per truck per year to keep water-based coolant cold enough to maintain functionality. They are weighing the value of their engine warranties and deciding if that value is more important than thousands per truck annually in fuel savings. On a dollars and cents basis, the fuel savings trump warranty risk (particularly since Evans HDTC, higher temperature or not, won’t harm the engine).
The OEMs will eventually come around, but Evans Cooling Systems is working with fleet owners who want these savings now, not in 5 or 10 years. In the future large fleets will be specifying equipment to be delivered with Evans HDTC in the cooling system and to be equipped with 215o F thermostats and programmed for fan-on at 230o F.
As it becomes known that engines protected with HDTC waterless coolant aren’t rusty inside, aren’t caked with baked-on coolant additives, and don’t have cylinder liners damaged by cavitation erosion, vehicle resale value will increase. Fleet owners using Evans HDTC will get premium prices when it is time to sell.