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A chassis dynamometer at Alban Tractor Company in Baltimore, Maryland was used to determine power and many other characteristics of the Caterpillar engine of a Kenworth diesel truck. Tests of the GTA fuel additive in diesel fuel were made at concentrations (units are parts per million by mass (ppm)) of 0, 2.6, 7.8, 20.8, 41.6 and again at an estimated 2.6. The last concentration was calculated using a fuel filter capacity of an estimated one gallon, and assuming that it held fuel at a concentration of 41.6 ppm from the previous test. Fifteen gallons of diesel fuel in the weigh tank (described below) when mixed with one gallon of 41.6 ppm additive compute to be 2.6 ppm. The actual concentration was probably between 2.6 ppm and 1 ppm, during the last dynamometer test.
The engine was a turbo diesel with an engine computer receiving data from several sensors. The data were processed by an onboard computer. That computer system should not be confused with the computer controlling the "Superflow" dynamometer. The vehicle computer controlled the sequence advance and duration of fuel injection. This system uses a gear pump to build fuel pressure. The engine had 90,421 miles on it: and is considered to be "new." The Caterpillar engine model number is 3176.
The baseline fuel dynamometer run was the first test in the morning when it was cool. The ambient temperature therefore favors the baseline fuel rather than the additive-containing fuel. The higher concentrations of additive were run under the worst ambient conditions, e.g., at higher air and fuel temperatures. Another difficulty with this open air chassis dynamometer test is that the tires do not transfer force to the rollers as efficiently when they are approaching a slick melting condition. Tire temperatures were coolest for the initial test with baseline fuel, and increased in the runs with additive. It was necessary from time to time to allow the tires to cool down as they approached a soft "melt" condition. Since each test involved seven maximum torque determinations at seven constant RPM settings, heating of the tires was substantial after a run at a particular additive concentration. Nevertheless, the accompanying data shows that the additive was effective. Both dynamometer corrected data and raw data showed that the additive substantially increased engine performance.
A tachometer sensor was attached to the transmission. The "Superflow" brand dynamometer system controlled the test protocol and the acquisition and processing of the raw data. A feedback loop resulted in the computer setting the engine speed to a constant value, and load was applied to the "lug" point where the speed could no longer be maintained. As mentioned previously, after the first "lug." Additional "lugs" were obtained at other constant speed settings.
The vehicle carries two fuel tanks having the same diameters but different lengths. They are connected to drain simultaneously into a common manifold to the suction inlet of the fuel pump. These tanks were bypassed to facilitate fuel testing. The circulating fuel management system was routed directly to a 15 gallon weigh tank in the dynamometer unit. This made the logistics of fuel handling for multiple runs with additive much easier than having to attempt to mix proportionate additive concentrate aliquots in a 60 gallon tank and a 100 gallon tank. In addition, the volumes of fuel required would have been too large to conveniently handle.
Additive was mixed as follows: Four gallons of diesel fuel were pumped from the 100 gallon (initially full) vehicle tank into a 5 gallon gas can. The required amount of additive was then added to the fuel in the can. The can was capped and shaken to disperse and mix the additive concentrate with the fuel. This mixture was then transferred into the weigh tank using the system's internal pump. Then enough additional diesel fuel from the 100 gallon tank was transferred into the weigh tank to obtain a reading of 100 % full on the dynamometer equipment. The final concentrate is then based on the mass of additive added to the can and the total mass of fuel in the weigh tank. Mixing was assumed to go to completion during the final transfer of the fuel to the 100 % full condition (15 gallons total).
Since the full tank was on a weighing suspension, a continuous record of fuel weight was obtained for each dynamometer run. The raw data was pounds of fuel used in real-time. Corrected values of fuel consumption employed fuel temperature and APE gravity detection through programmed compensation algorithms. Although each concentration generated two dynamometer runs, only the first run at each concentration provided data for the coolest fuel temperature and coolest tire temperatures. Since the fuel is used to cool the injectors, the temperature of the fuel increased during the first run at each concentration. Since the fuel volume was substantially less than 15 gallons at the start of each second run, and the fuel had been heated during the first run, the fuel temperature was very much above ambient after the completion of the second run. Taking the fuel heating and tire heating issues into consideration, only first run data were reasonably free of confounding influences.
The accompanying charts have the format of a series of clustered bars, with one bar per concentration tested. There are eight sets of bars covering eight constant RPM tests. The first bar (2100) RPM is the beginning idle condition before the first "lug" test is run, and the data are of little value. The data show that, for this particular vehicle, the effect of the additive reaches a maximum at 21 ppm or less, but more than 8 ppm. The greatest effect, relative to baseline fuel is at 21 ppm. Due to time constraints, concentrations between 8 ppm and 21 ppm were not run. It was only in retrospect that the region between 8 and 21 ppm looked particularly interesting.
The accompanying "Exhaust Pressure" chart shows that the exhaust pressure decreased about 27 % with 21 ppm additive at 1900 RPM. The exhaust pressure was measured in the exhaust pipe between the engine and the muffler. The pressure reduction with additive suggests more efficient engine operation, and most probably, less exhaust gas and associated pollutant emissions. Unfortunately, the engine was not instrumented with a thermocouple near the exhaust valve for simultaneous recording of exhaust temperature.
The Chart entitled "Intake Manifold Pressure" shows a reduction in the demand for turbo boost with additive in the fuel. This correlates well with the reduction in exhaust pressure, and the reduction in fuel consumption to be shown later. A 14 % decrease in turbo boost pressure required was seen at 1900 RPM at 21 ppm additive.
The "Fuel Mass per Hour" Chart shows the raw data for fuel consumption from the dynamometer instrumentation. The Raw data show a decrease in fuel consumption of 8 % at 1900 RPM. This correlates closely with uncorrected and corrected decreases in brake specific fuel consumption.
Horsepower is taken into account in the Chart entitled "Corr. Brake Specific Fuel Consumption." The Superflow dynamometer contains compensation algorithms which correct for fuel temperature, air temperature, and ambient air pressure. These data show the fuel consumption for equal work outputs. There was an 8.3 % decrease in corrected brake specific fuel consumption at 1900 RPM.
The "uncorrected Vehicle Horsepower" chart shows that raw horsepower data, uncorrected for the hot conditions during the additive runs, still managed to increase as a whole with additive in the fuel. In other words, the additive overcame some of the power-robbing effects of increased fuel and air temperatures, and tire slip.
As expected, the dynamometer system's algorithms increased the horsepower values for the runs during the heat of the day. Correction is used as a substitute for running tests under standard environmental conditions, which is very costly to do. There was a 9 % increase in corrected horsepower at 1800 rpm with 21 ppm additive. Unfortunately, the dynamometer does not provide values calculated for 1848 and 1900 RPM conditions.
These constant RPM tests show that the additive substantially improves the operation of a Caterpillar turbo-diesel engine with computer-controlled fuel injection. The test does not cover the possibility of further substantial operational improvements under transient conditions encountered in the "real world." Fleet tests or advanced dynamometer tests would be required for more real-world-like performance data. Emissions composition and pollutant emissions per brake horsepower hour are entirely lacking. Visually, there was no discernible exhaust soot during any of the tests described in this report.
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