Tailgate down - mythbusters!!!
#11
11-21-2005, 10:07 AM
RE: Tailgate down - mythbusters!!!
I have had my soft cover for about a month now and I picked up 2mpg overall. I got 14.5mpg last time and I norm get 12.5. I live in a windy area and with the tailgate up I know it is a huge speed brake when I drive into the wind. In the year I owned the truck I NEVER got 14.5mpg. So I'm here to tell you it DOES work if you cover your bed. The added MPG was a nice bonus but I mainly wanted to cover all the scratches in the bed. They dont do Line-x in Europe. I have to wait till I leave next summer to get it sprayed. A litte note on the soft covers. Get the one with the upward support ridges. Dont get the flat soft cover. Mine is flat and it holds water when it rains and the added weight makes the material sag. When it sags it stretches. When it streches it gets loose and flaps in the wind. If I could do it again I would get one that looks like a covered wagon so the rain wouldnt collect. I get tired of going out every few weeks and re tighting it. But I'll do it gladly for the extra 2mpg. That gives me a extra 40 miles to the tank. I fill up around quarter tank left and buy around 20 gallons.
With the flat soft cover I found as long as I park on a hill in my driveway the angle is good enough to allow the rain not to collect. So all is not lost.
With the flat soft cover I found as long as I park on a hill in my driveway the angle is good enough to allow the rain not to collect. So all is not lost.
#12
11-21-2005, 10:09 AM
RE: Tailgate down - mythbusters!!!
The Mythbusters TV show has a statistical science advisor,
so if that two truck comparison is all they did
it is unexcusable - but they don't tell us what they did before that televised test.
The correct proceedure
(Society of Automotive Engineers Type IV approved test)
is to run the two trucks un-modified at least three times over the same trip and make sure the two trucks don't differ more than a small amount in MPG - then run one one truck in the 'modified' condition with the other truck acting as a 'control' to see if things like wind, fuel, temperature has changed and thrown the results off.
As an additional check, it is recomended to swap the 'modification' onto the 2nd control truck and un-modify the first truck to let it act as the control on another run.
If you run a SAE/TMC Type IV fuel economy test this way you can detect down to 2% differences in MPG.
Since in the Mythbusters TV show the difference in mileage driven on one tank between the two trucks seems to be a lot less than two percent, you could also say the effect of driving with the tailgate down is so small THAT ONLY THE MOST CAREFUL OF TESTS WOULD BE ABLE TO DETECT IT.
Here's what some engineers students did on Ram truck aerodynamics,
and it was good enough to win a prize from SAE;
http://web.archive.org/web/200304141...affner/did.htm
More tech info on the SAE/TMC Type IV fuel economy test
(for geeks or statistically trained)
-----------------------------------
Testing...One, Two, Three, Four:
Determining Truck/Component
Fuel Efficiency
By CLAUDE TRAVIS
--------------------------------------------------------------------------------
A new, in-service, fuel efficiency test has been devised by members of The Maintenance Council of the American Trucking Associations. Here's a look at the Type IV procedure and its still-viable predecessors.
--------------------------------------------------------------------------------
Testing...One, Two, Three, Four: Determining Truck/Component Fuel Efficiency
Editor's note: Claude Travis, known to his peers at TMC as "Mr. MPG," has spent 37 years managing the operation, maintenance and testing of heavy-duty, on-highway vehicles. Highly regarded for his exhaustive research in the field of heavy-vehicle fuel-economy, he is principal of Claude Travis and Associates, Fleet Consultants, Grand Rapids, Mich.
While computer simulations can forecast truck fuel efficiency, a real-world test also has merit. In fact, a two-truck, on- road test remains a very practical and accurate way to determine how much a specific vehicle/component can boost fuel mileage.
In sharp contrast, a single-truck test is subjective, and of no real value, because too many variables (such as wind speed, wind direction and ambient temperature) are not controlled.
After the infamous 1973 fuel shortage, the Society of Automotive Engineers (SAE), Warrendale, Pa., and The Maintenance Council (TMC) of the American Trucking Associations, Alexandria, Va., jointly developed an initial, on-road, two-truck test procedure. In 1982, TMC/SAE In-Service Fuel Consumption Test ProcedureÂ*Type II was developed, and designated TMC Recommended Practice 1102.
A Type II test is well suited to multiple-run testing of major components, such as engines and transmissions. Basically, the Type II procedure involves repeatedly running a control vehicle in tandem with a test vehicle, and determining the amount of fuel used by each vehicle (ideally, via pre-trip and post-trip weighing of portable fuel tanks). Vehicles either are operated on a test track or on-road, using a route that begins and ends at the same location. Using this procedure, drivers do not swap vehicles.
Type III arrives
In 1988, the Type III test, designated RP 1103, was introduced. While retaining many elements of the still-viable Type II test, the Type III procedure is especially suitable for testing easily-swapped components/accessories. During a Type III test, the item being evaluated is switched from one vehicle to the other. If an entire truck is being tested, drivers swap vehicles.
Favored by fleets, tire companies, component/engine makers and vehicle OEMs, Type II/III tests have become American standards. But it was found that productive modifications to either procedure could be made.
For example, some testers have found it advantageous to greatly extend traditional 28 to 50 mile test runs to 200 miles or more, while actually hauling freight. That's a good idea, because it eliminates the expense of taking equipment and drivers out of revenue service to conduct short-haul tests. And accuracy is not sacrificed.
In fact, long test runs can retain a plus-or-minus 1% test accuracy (traditionally achieved with the use of portable fuel tanks) when using the truck's regular fuel tanks and a fuel island meter reading, provided that:
a correction is made for fuel temperature, which compensates for differences in fuel density;
the test run exceeds 200 miles.
To formalize that new approach, an extended-run test procedure, designated Type IV, has been devised. Designated TMC Recommended Practice 1109, the Type IV procedure is designed to supplement, not replace, the Type II/III procedures.
Now, to get a better handle on the topic, let's take a general look at TMC's fuel economy tests.
Essential controls noted
Typically, fuel-economy tests require that two test trucks run together but remain properly spaced, so that one does not influence the other. When conducting Type II/III tests, route selection also is very important.
Test Type II/III runs are short (28 to 50 miles) and, to be successful, each run must be a carbon copy of the preceding one. For example, each driver must make identical turn-arounds, and accelerate/decelerate at precisely the same time. A driver can't allow traffic-induced slowdowns: if that occurs, the run must be voided and repeated.
Ideally, an on-road route should be similar to a test track, with no traffic snarls. Tests require a one-hour warm-up. If the warm-up time is used to drive 60-plus miles away from an urban area, traffic usually will be light enough to get good test results.
In contrast, the 200 to 450 mile test runs characteristic of the Type IV procedure are slightly more forgiving. Still, both drivers must remain in voice communication so that each event affecting fuel consumptionÂ*such as shifting, or even turning the wipers onÂ*can occur simultaneously on both trucks. Like its predecessors, the Type IV test also requires a warm-up period, during which drivers can fine-tune their system of communication.
Generally, TMC tests require a minimum of three successful runs in each test segment. When conducting a Type II or Type III test, "successful" runs must fall within a 2% fuel-consumption-ratio window and a test-run-time window of .5%. More on that later. The point is that, when using the Type IV procedure, a 2% fuel-consumption window still applies. Time ceases to be a factor, because test vehicles are in voice contact and traveling the same distance while making the same maneuvers.
If necessary, however, Type IV test runs can be made serially on very long cross-country hauls.
Selecting test drivers
To conduct a test requires the services of two, highly-qualified drivers. Equally important is the need to select drivers who will work well with a test supervisor, and who are highly motivated to produce good test results. If conducted by disinterested drivers, testing can consume a lot of time.
When scientific tests are conducted in a laboratory, all data points are included in the calculation of results. When conducting on-road evaluations, however, tests must be repeated until three runs fit the previously-mentioned 2% fuel and .5% time windows. Test runs that don't fit the windows are thrown out. That safeguard is vital, because the test is exposed to all the variables of the real worldÂ*traffic, mechanical problems, driver error, etc.
Typically, however, sufficient data usually can be collected in three or four test runs. And the cause for unacceptable runs usually can be determined readily, using post-run vehicle inspection and driver interviews.
How did TMC validate Type IV?
Modified, extended-run versions of Type II and Type III testing initially were evaluated, with repeated success, by Jim Booth, fuel economy test supervisor at Caterpillar Engine Div., Mossville, Ill. His work provided the quantitative data that convinced TMC to pursue development of the Type IV procedure.
Two key validation tests were conducted. The first one utilized facilities and vehicles of Southeastern Freight Lines, Columbia, S.C. The second one used vehicles owned by Detroit Diesel and Caterpillar near Lexington, Ky. Essentially, those tests compared the Type II/III test-run distances and portable-tank method of measuring fuel consumption against the extended-run Type IV procedure, using a commercial pump meter, in tandem with calculated fuel-temperature correction.
The final method of fuelingÂ*and the procedure for fuel-temperature correctionÂ*was developed by Bob Wessels, Caterpillar's manager, 3400 customer value. To be considered valid, the results of a Type IV test had to fit within the 2% fuel consumption window of the Type II/III test results.
What does one test prove?
To an experienced tester, the results of a single test are a strong indication of the mpg-improvement potential of a vehicle, component, or system. However, the test result only reflects the performance of the test trucks on a given day, with specific loads and drivers. That is, tests must be repeatable in order to be fully validated. Multiple tests, using different vehicles at various locations, can result in very precise mpg figures.
Results typically are expressed in terms of the percentage of fuel saved, or the percentage of improvement.
On-road testing vs a test track
On-road testing can be as accurate as testing on a closed track. The key variable, however, is traffic volume. Traffic causes air turbulence. The denser the traffic, the greater the turbulence. Heavy volumes of truck traffic causes "dirty air" and easily can result in a test run fuel consumption ratio falling outside the required 2% window.
A test run on a private, seven-mile test track with sparse traffic all going in the same direction can result in repeatable data points within a .5% window. This also can be accomplished on-road, in clean air. The concern that some people have with track testing is that it's not "real world," which I have trouble understanding, because I don't know of a truck that knows where it is. However, if you want to test in mountainous terrain, it's necessary to test on the road.
Good test routes can be found anywhere in the United States. Use the interstate highway system or a four-lane, limited-access highway. But avoid routes with traffic lights, weigh stations or rush-hour slowdowns.
Choose a maximum test speed that's slightly slower than most trafficÂ*such as 63 mph in a 65 mph stateÂ*where most traffic is going 68 mph or more. This allows traffic to move slowly around the test trucks. Instruct the drivers to look ahead (to avoid being pulled into a slowdown by a slower vehicle), and to change lanes early to avoid being trapped.
The Type IV procedure
First, I want to strongly urge anyone who may wish to run a long- haul, two-truck, Type IV test to get TMC Recommended Practice 1109 and read it very carefully. It provides more detail than the following description. These tests are not difficult to conduct, but one must follow the procedure closely, paying attention to all hints and warnings.
Here's the basic Type IV procedure. Two tractor-trailer combinations are dispatched together. And, during the one hour warm-up period, the drivers practice speed management using visual and voice contact. In the following test-run example, both tractors and trailers are identical except for the component being tested; which, in this example, is a newly-designed air dam, mounted on the bumper of the first truck.
While not identical, gross vehicle weights are within 5%, as recommended by the Type IV procedure. Each truck has its left-side tank isolated, and its right-side tank drained. The right-side tank will be filled from the same pump, to assure equal heat content.
At the end of the warm-up period, both trucks pull into a truck stop and top-off their tanks, one at a time, from the same spot at the same pump. The fuel is brought up to a predetermined point in each tank very carefully, and the temperature is taken with a remote-reading, digital thermometer from a point near the center of the tank. Care is taken to assure that engine-on time and distances moved within the truck stop are equal.
Both drivers leave the fuel station together. The lead driver establishes and maintains the test speed while the following driver establishes and maintains a 15 to 45 second gap between the two vehicles.
Within 5% of the test run midpoint, the drivers pull into a facility that will permit dropping the trailers. The drivers swap tractors but stay with the trailers they pulled during the first half of the run. This eliminates any effect that drivers or trailers might have on the test results.
When the trucks leave the midpoint equipment-switch facility, the driver who led the first half of the test run must lead during the second half. The following driver must maintain the same gap used during the first half of the test run.
At the end of the test run, the trucks are again fueled, one at a time, from the same spot at the same pump. The fuel is very carefully brought up to the same, predetermined point on the filler neck (or, to the same point on a free-swinging dip stick scale).
After filling each tank, the gallons and tenths of gallons added are recorded, the fuel tank temperature is recorded and a correction to 60°F is calculated (see tables at left). The trucks have now completed one test run and are free to complete their revenue- producing trip.
These trucks and drivers make this same run every other day, the other two test runs of the required set of three can be completed within a week. A validation test would take another week.
The only cost to the trucking company to do this Type IV test would be the installation time of the air dam, plumbing the fuel tanks, draining and refilling tanks, and the supervisory time to plan/execute the test, plus the calculations/reporting after the tests. There also would be minor driver and vehicle delays, due to the pre-test and post-test fueling and the mid-point tractor swap.
If the same test were done using the SAE/TMC Type III procedure, both vehicles and drivers would have to be removed from revenue service. The tractors would be equipped with portable fuel tanks. And a ground crew of at least two tank handlers and one supervisor would have to accompany the scales, fuel and test trucks to a suitable test site. It would take a day to prepare the trucks. After the trucks were prepared, one complete test could be done during the second day. A validation test to demonstrate repeatability would take a third day.
Hopefully, this gives you some idea of the practical benefits of the Type IV test.
To order a copy of the Type II (RP 1102), Type III (RP 1103), or Type IV (RP 1109) test procedures, call TMC at (703) 838-1763. The Type IV procedureÂ*which is nearly 20 pages long, including numerous forms required for recording test dataÂ*sells for $20.
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Type IV Fuel Test Results Worksheet
This is the calculation form for fuel consumption comparison of two vehicles when a device, system, or component of a combination vehicle is switched from one vehicle to a second vehicle at test run mid-point. It is strongly recommended that Form 5: "Valid Ration Worksheet" appear on the reverse of this form.
Fleet: ABC Test Number & Description: 1 TYPE IV
Date: 3/11/96 Test Route:
Vehicle A is Unit No.: 718 Vehicle B is Unit No.:
The component(s) tested in Vehicle A is/are: The component(s) tested in Vehicle B is/are:
AIR DAM
<
NOTE: Always make sure Vehicle A is the vehicle with the lower fuel usage or the result will be a negative number.
Vehicle A Vehicle B
Gallons Fuel Consumed Gallons Fuel Consumed Indicate
Run Corrected to 60° Corrected to 60° Ratio A/B Valid Runs (1)
1. 29.45 30.52 1.0363 X
2. 29.79 30.89 1.0369 X
3. 28.84 30.64 1.0624 X
4. 28.91 29.76 1.0294 X
5.
(1) Minimum of three valid run ratios (within two percent of each other) are required.
Total Fuel Used During Valid Runs:
Vehicle A: 88.15 gal Vehicle B: 91.17 gal
Results:
[Fuel Used by Vehicle B] - [Fuel Used by Vehicle A]
% Improvement = ___________________________________________ X 100
[Fuel Used by Vehicle A]
[ 91.7 (B)] - [ 88.15 (A)]
= _____________________________ X 100 = 3.42%
[ 88.15 (A)]
[Fuel Used by Vehicle B] - [Fuel Used by Vehicle A]
% Fuel Saved = ___________________________________________ X 100
[Fuel Used by Vehicle A]
[ 91.7 (B)] - [ 88.15 (A)]
= _____________________________ X 100 = 3.31%
[ 91.17 (B)]
NOTE: A single test is only an indicator. Two totally independent tests with data within two percent of each other are considered good results.
To be valid, test results for each run must fall within 2% of each other. To establish a ratio, divide the amount of temperature-corrected fuel consumed by Vehicle B (30.52 gal in Run 1) by the amount of temperature-corrected fuel consumed by Vehicle A (29.45 gal in Run 1). The ratio is 1.0363.
Do the same for the other runs. In this case, Run 3 is not within the 2% window, and is therefore not valid.
Now take the total fuel consumed by Vehicle B during the three valid runs, subtract the total fuel consumed by Vehicle A, divide by Vehicle A's total consumed fuel, and multiply by 100 for a percentage improvement.
To calculate the percentage of fuel saved, again subtract A from B, but divide by B's total fuel, and multiply by 100. (Worksheet Source: TMC RP 1109)
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--------------------------------------------------------------------------------
Determining Fuel Group ASTM Group Number Specific Gravity Range API Gravity Range
1 0.8499 - 0.9659 15.0 - 34.9
2 0.7754 - 0.8498 35.0 - 50.9
3 0.7239 - 0.7753 51.0 - 63.9
4 0.6723 - 0.7238 64.0 - 78.9
Before using temperature-correction table, determine, by specific gravity, what group your fuel falls into. If this isn't possible, assume your fuel has an API gravity of 37, which is most common for U.S. diesel fuel. That means your fuel will most likely fall into Group 2.
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Fuel-temperature correction (shown for Group 2 fuel only) Fuel Temp (°F) Conversion (gal) Fuel Temp (°F) Conversion (gal)
40 0.9902 71 1.0055
41 0.9907 72 1.0060
42 0.9912 73 1.0065
43 0.9917 74 1.0070
44 0.9922 75 1.0076
45 0.9926 76 1.0081
46 0.9930 77 1.0085
47 0.9935 78 1.0090
48 0.9940 79 1.0095
49 0.9945 80 1.0100
50 0.9950 81 1.0105
51 0.9955 82 1.0110
52 0.9960 83 1.0115
53 0.9965 84 1.0120
54 0.9971 85 1.0126
55 0.9976 86 1.0131
56 0.9980 87 1.0136
57 0.9985 88 1.0141
58 0.9990 89 1.0146
59 0.9995 90 1.0151
60 1.000 91 1.0156
61 1.0005 92 1.0162
62 1.0010 93 1.0167
63 1.0015 94 1.0172
64 1.0020 95 1.0177
65 1.0025 96 1.0182
66 1.003 97 1.0187
67 1.0035 98 1.0193
68 1.0040 99 1.0198
69 1.0045 100 1.0203
70 1.0050
Table based on Tables 7 and 25 of "Petroleum Measurement Tables," published by the American Society for Testing and Materials, Philadelphia.
Temperature correction is necessary because fuel density, or energy content of a given volume of fuel, changes with temperature. A baseline of 60° F is used. TMC offers the following example of temperature correction to 60° F for Group 2 fuels: Assume a tank has a liquid capacity of 100 gal. A test run is made that uses 50 gal. At the start of the run, the temperature is 75° F. At the end of the run, the temperature is 95° F. At 75° F, according to the group 2 column, 100 gal of fuel at 60° F would need to be 100.76 gal to have equal energy. At 95° F, 101.77 gal would be needed to have the same energy. The difference is 1.01 gal (101.77 - 100.76 = 1.01). The temperature-corrected addition is 50 + 1.01 = 51.01. Thus, 51.01 gal is the amount of fuel that would be used for all calculations for this vehicle on this run.
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How to order reprints of this article
For a free single copy of this article, write on company letterhead to: Reprint Editor, Commercial Carrier Journal, 1 Chilton Way, Radnor, Pa. 19089. Additional copies $2 each. Send prepaid check or money order.
54 COMMERCIAL CARRIER JOURNAL June 1996
Go to CCJ's FEATURES listings.
--------------------------------------------------------------------------------
Go to CCJ's MARCH 1997 MAINTENANCE & TECHNOLOGY column about TMC/SAE Type IV procedure.
so if that two truck comparison is all they did
it is unexcusable - but they don't tell us what they did before that televised test.
The correct proceedure
(Society of Automotive Engineers Type IV approved test)
is to run the two trucks un-modified at least three times over the same trip and make sure the two trucks don't differ more than a small amount in MPG - then run one one truck in the 'modified' condition with the other truck acting as a 'control' to see if things like wind, fuel, temperature has changed and thrown the results off.
As an additional check, it is recomended to swap the 'modification' onto the 2nd control truck and un-modify the first truck to let it act as the control on another run.
If you run a SAE/TMC Type IV fuel economy test this way you can detect down to 2% differences in MPG.
Since in the Mythbusters TV show the difference in mileage driven on one tank between the two trucks seems to be a lot less than two percent, you could also say the effect of driving with the tailgate down is so small THAT ONLY THE MOST CAREFUL OF TESTS WOULD BE ABLE TO DETECT IT.
Here's what some engineers students did on Ram truck aerodynamics,
and it was good enough to win a prize from SAE;
http://web.archive.org/web/200304141...affner/did.htm
More tech info on the SAE/TMC Type IV fuel economy test
(for geeks or statistically trained)
-----------------------------------
Testing...One, Two, Three, Four:
Determining Truck/Component
Fuel Efficiency
By CLAUDE TRAVIS
--------------------------------------------------------------------------------
A new, in-service, fuel efficiency test has been devised by members of The Maintenance Council of the American Trucking Associations. Here's a look at the Type IV procedure and its still-viable predecessors.
--------------------------------------------------------------------------------
Testing...One, Two, Three, Four: Determining Truck/Component Fuel Efficiency
Editor's note: Claude Travis, known to his peers at TMC as "Mr. MPG," has spent 37 years managing the operation, maintenance and testing of heavy-duty, on-highway vehicles. Highly regarded for his exhaustive research in the field of heavy-vehicle fuel-economy, he is principal of Claude Travis and Associates, Fleet Consultants, Grand Rapids, Mich.
While computer simulations can forecast truck fuel efficiency, a real-world test also has merit. In fact, a two-truck, on- road test remains a very practical and accurate way to determine how much a specific vehicle/component can boost fuel mileage.
In sharp contrast, a single-truck test is subjective, and of no real value, because too many variables (such as wind speed, wind direction and ambient temperature) are not controlled.
After the infamous 1973 fuel shortage, the Society of Automotive Engineers (SAE), Warrendale, Pa., and The Maintenance Council (TMC) of the American Trucking Associations, Alexandria, Va., jointly developed an initial, on-road, two-truck test procedure. In 1982, TMC/SAE In-Service Fuel Consumption Test ProcedureÂ*Type II was developed, and designated TMC Recommended Practice 1102.
A Type II test is well suited to multiple-run testing of major components, such as engines and transmissions. Basically, the Type II procedure involves repeatedly running a control vehicle in tandem with a test vehicle, and determining the amount of fuel used by each vehicle (ideally, via pre-trip and post-trip weighing of portable fuel tanks). Vehicles either are operated on a test track or on-road, using a route that begins and ends at the same location. Using this procedure, drivers do not swap vehicles.
Type III arrives
In 1988, the Type III test, designated RP 1103, was introduced. While retaining many elements of the still-viable Type II test, the Type III procedure is especially suitable for testing easily-swapped components/accessories. During a Type III test, the item being evaluated is switched from one vehicle to the other. If an entire truck is being tested, drivers swap vehicles.
Favored by fleets, tire companies, component/engine makers and vehicle OEMs, Type II/III tests have become American standards. But it was found that productive modifications to either procedure could be made.
For example, some testers have found it advantageous to greatly extend traditional 28 to 50 mile test runs to 200 miles or more, while actually hauling freight. That's a good idea, because it eliminates the expense of taking equipment and drivers out of revenue service to conduct short-haul tests. And accuracy is not sacrificed.
In fact, long test runs can retain a plus-or-minus 1% test accuracy (traditionally achieved with the use of portable fuel tanks) when using the truck's regular fuel tanks and a fuel island meter reading, provided that:
a correction is made for fuel temperature, which compensates for differences in fuel density;
the test run exceeds 200 miles.
To formalize that new approach, an extended-run test procedure, designated Type IV, has been devised. Designated TMC Recommended Practice 1109, the Type IV procedure is designed to supplement, not replace, the Type II/III procedures.
Now, to get a better handle on the topic, let's take a general look at TMC's fuel economy tests.
Essential controls noted
Typically, fuel-economy tests require that two test trucks run together but remain properly spaced, so that one does not influence the other. When conducting Type II/III tests, route selection also is very important.
Test Type II/III runs are short (28 to 50 miles) and, to be successful, each run must be a carbon copy of the preceding one. For example, each driver must make identical turn-arounds, and accelerate/decelerate at precisely the same time. A driver can't allow traffic-induced slowdowns: if that occurs, the run must be voided and repeated.
Ideally, an on-road route should be similar to a test track, with no traffic snarls. Tests require a one-hour warm-up. If the warm-up time is used to drive 60-plus miles away from an urban area, traffic usually will be light enough to get good test results.
In contrast, the 200 to 450 mile test runs characteristic of the Type IV procedure are slightly more forgiving. Still, both drivers must remain in voice communication so that each event affecting fuel consumptionÂ*such as shifting, or even turning the wipers onÂ*can occur simultaneously on both trucks. Like its predecessors, the Type IV test also requires a warm-up period, during which drivers can fine-tune their system of communication.
Generally, TMC tests require a minimum of three successful runs in each test segment. When conducting a Type II or Type III test, "successful" runs must fall within a 2% fuel-consumption-ratio window and a test-run-time window of .5%. More on that later. The point is that, when using the Type IV procedure, a 2% fuel-consumption window still applies. Time ceases to be a factor, because test vehicles are in voice contact and traveling the same distance while making the same maneuvers.
If necessary, however, Type IV test runs can be made serially on very long cross-country hauls.
Selecting test drivers
To conduct a test requires the services of two, highly-qualified drivers. Equally important is the need to select drivers who will work well with a test supervisor, and who are highly motivated to produce good test results. If conducted by disinterested drivers, testing can consume a lot of time.
When scientific tests are conducted in a laboratory, all data points are included in the calculation of results. When conducting on-road evaluations, however, tests must be repeated until three runs fit the previously-mentioned 2% fuel and .5% time windows. Test runs that don't fit the windows are thrown out. That safeguard is vital, because the test is exposed to all the variables of the real worldÂ*traffic, mechanical problems, driver error, etc.
Typically, however, sufficient data usually can be collected in three or four test runs. And the cause for unacceptable runs usually can be determined readily, using post-run vehicle inspection and driver interviews.
How did TMC validate Type IV?
Modified, extended-run versions of Type II and Type III testing initially were evaluated, with repeated success, by Jim Booth, fuel economy test supervisor at Caterpillar Engine Div., Mossville, Ill. His work provided the quantitative data that convinced TMC to pursue development of the Type IV procedure.
Two key validation tests were conducted. The first one utilized facilities and vehicles of Southeastern Freight Lines, Columbia, S.C. The second one used vehicles owned by Detroit Diesel and Caterpillar near Lexington, Ky. Essentially, those tests compared the Type II/III test-run distances and portable-tank method of measuring fuel consumption against the extended-run Type IV procedure, using a commercial pump meter, in tandem with calculated fuel-temperature correction.
The final method of fuelingÂ*and the procedure for fuel-temperature correctionÂ*was developed by Bob Wessels, Caterpillar's manager, 3400 customer value. To be considered valid, the results of a Type IV test had to fit within the 2% fuel consumption window of the Type II/III test results.
What does one test prove?
To an experienced tester, the results of a single test are a strong indication of the mpg-improvement potential of a vehicle, component, or system. However, the test result only reflects the performance of the test trucks on a given day, with specific loads and drivers. That is, tests must be repeatable in order to be fully validated. Multiple tests, using different vehicles at various locations, can result in very precise mpg figures.
Results typically are expressed in terms of the percentage of fuel saved, or the percentage of improvement.
On-road testing vs a test track
On-road testing can be as accurate as testing on a closed track. The key variable, however, is traffic volume. Traffic causes air turbulence. The denser the traffic, the greater the turbulence. Heavy volumes of truck traffic causes "dirty air" and easily can result in a test run fuel consumption ratio falling outside the required 2% window.
A test run on a private, seven-mile test track with sparse traffic all going in the same direction can result in repeatable data points within a .5% window. This also can be accomplished on-road, in clean air. The concern that some people have with track testing is that it's not "real world," which I have trouble understanding, because I don't know of a truck that knows where it is. However, if you want to test in mountainous terrain, it's necessary to test on the road.
Good test routes can be found anywhere in the United States. Use the interstate highway system or a four-lane, limited-access highway. But avoid routes with traffic lights, weigh stations or rush-hour slowdowns.
Choose a maximum test speed that's slightly slower than most trafficÂ*such as 63 mph in a 65 mph stateÂ*where most traffic is going 68 mph or more. This allows traffic to move slowly around the test trucks. Instruct the drivers to look ahead (to avoid being pulled into a slowdown by a slower vehicle), and to change lanes early to avoid being trapped.
The Type IV procedure
First, I want to strongly urge anyone who may wish to run a long- haul, two-truck, Type IV test to get TMC Recommended Practice 1109 and read it very carefully. It provides more detail than the following description. These tests are not difficult to conduct, but one must follow the procedure closely, paying attention to all hints and warnings.
Here's the basic Type IV procedure. Two tractor-trailer combinations are dispatched together. And, during the one hour warm-up period, the drivers practice speed management using visual and voice contact. In the following test-run example, both tractors and trailers are identical except for the component being tested; which, in this example, is a newly-designed air dam, mounted on the bumper of the first truck.
While not identical, gross vehicle weights are within 5%, as recommended by the Type IV procedure. Each truck has its left-side tank isolated, and its right-side tank drained. The right-side tank will be filled from the same pump, to assure equal heat content.
At the end of the warm-up period, both trucks pull into a truck stop and top-off their tanks, one at a time, from the same spot at the same pump. The fuel is brought up to a predetermined point in each tank very carefully, and the temperature is taken with a remote-reading, digital thermometer from a point near the center of the tank. Care is taken to assure that engine-on time and distances moved within the truck stop are equal.
Both drivers leave the fuel station together. The lead driver establishes and maintains the test speed while the following driver establishes and maintains a 15 to 45 second gap between the two vehicles.
Within 5% of the test run midpoint, the drivers pull into a facility that will permit dropping the trailers. The drivers swap tractors but stay with the trailers they pulled during the first half of the run. This eliminates any effect that drivers or trailers might have on the test results.
When the trucks leave the midpoint equipment-switch facility, the driver who led the first half of the test run must lead during the second half. The following driver must maintain the same gap used during the first half of the test run.
At the end of the test run, the trucks are again fueled, one at a time, from the same spot at the same pump. The fuel is very carefully brought up to the same, predetermined point on the filler neck (or, to the same point on a free-swinging dip stick scale).
After filling each tank, the gallons and tenths of gallons added are recorded, the fuel tank temperature is recorded and a correction to 60°F is calculated (see tables at left). The trucks have now completed one test run and are free to complete their revenue- producing trip.
These trucks and drivers make this same run every other day, the other two test runs of the required set of three can be completed within a week. A validation test would take another week.
The only cost to the trucking company to do this Type IV test would be the installation time of the air dam, plumbing the fuel tanks, draining and refilling tanks, and the supervisory time to plan/execute the test, plus the calculations/reporting after the tests. There also would be minor driver and vehicle delays, due to the pre-test and post-test fueling and the mid-point tractor swap.
If the same test were done using the SAE/TMC Type III procedure, both vehicles and drivers would have to be removed from revenue service. The tractors would be equipped with portable fuel tanks. And a ground crew of at least two tank handlers and one supervisor would have to accompany the scales, fuel and test trucks to a suitable test site. It would take a day to prepare the trucks. After the trucks were prepared, one complete test could be done during the second day. A validation test to demonstrate repeatability would take a third day.
Hopefully, this gives you some idea of the practical benefits of the Type IV test.
To order a copy of the Type II (RP 1102), Type III (RP 1103), or Type IV (RP 1109) test procedures, call TMC at (703) 838-1763. The Type IV procedureÂ*which is nearly 20 pages long, including numerous forms required for recording test dataÂ*sells for $20.
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Type IV Fuel Test Results Worksheet
This is the calculation form for fuel consumption comparison of two vehicles when a device, system, or component of a combination vehicle is switched from one vehicle to a second vehicle at test run mid-point. It is strongly recommended that Form 5: "Valid Ration Worksheet" appear on the reverse of this form.
Fleet: ABC Test Number & Description: 1 TYPE IV
Date: 3/11/96 Test Route:
Vehicle A is Unit No.: 718 Vehicle B is Unit No.:
The component(s) tested in Vehicle A is/are: The component(s) tested in Vehicle B is/are:
AIR DAM
<
NOTE: Always make sure Vehicle A is the vehicle with the lower fuel usage or the result will be a negative number.
Vehicle A Vehicle B
Gallons Fuel Consumed Gallons Fuel Consumed Indicate
Run Corrected to 60° Corrected to 60° Ratio A/B Valid Runs (1)
1. 29.45 30.52 1.0363 X
2. 29.79 30.89 1.0369 X
3. 28.84 30.64 1.0624 X
4. 28.91 29.76 1.0294 X
5.
(1) Minimum of three valid run ratios (within two percent of each other) are required.
Total Fuel Used During Valid Runs:
Vehicle A: 88.15 gal Vehicle B: 91.17 gal
Results:
[Fuel Used by Vehicle B] - [Fuel Used by Vehicle A]
% Improvement = ___________________________________________ X 100
[Fuel Used by Vehicle A]
[ 91.7 (B)] - [ 88.15 (A)]
= _____________________________ X 100 = 3.42%
[ 88.15 (A)]
[Fuel Used by Vehicle B] - [Fuel Used by Vehicle A]
% Fuel Saved = ___________________________________________ X 100
[Fuel Used by Vehicle A]
[ 91.7 (B)] - [ 88.15 (A)]
= _____________________________ X 100 = 3.31%
[ 91.17 (B)]
NOTE: A single test is only an indicator. Two totally independent tests with data within two percent of each other are considered good results.
To be valid, test results for each run must fall within 2% of each other. To establish a ratio, divide the amount of temperature-corrected fuel consumed by Vehicle B (30.52 gal in Run 1) by the amount of temperature-corrected fuel consumed by Vehicle A (29.45 gal in Run 1). The ratio is 1.0363.
Do the same for the other runs. In this case, Run 3 is not within the 2% window, and is therefore not valid.
Now take the total fuel consumed by Vehicle B during the three valid runs, subtract the total fuel consumed by Vehicle A, divide by Vehicle A's total consumed fuel, and multiply by 100 for a percentage improvement.
To calculate the percentage of fuel saved, again subtract A from B, but divide by B's total fuel, and multiply by 100. (Worksheet Source: TMC RP 1109)
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Determining Fuel Group ASTM Group Number Specific Gravity Range API Gravity Range
1 0.8499 - 0.9659 15.0 - 34.9
2 0.7754 - 0.8498 35.0 - 50.9
3 0.7239 - 0.7753 51.0 - 63.9
4 0.6723 - 0.7238 64.0 - 78.9
Before using temperature-correction table, determine, by specific gravity, what group your fuel falls into. If this isn't possible, assume your fuel has an API gravity of 37, which is most common for U.S. diesel fuel. That means your fuel will most likely fall into Group 2.
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Fuel-temperature correction (shown for Group 2 fuel only) Fuel Temp (°F) Conversion (gal) Fuel Temp (°F) Conversion (gal)
40 0.9902 71 1.0055
41 0.9907 72 1.0060
42 0.9912 73 1.0065
43 0.9917 74 1.0070
44 0.9922 75 1.0076
45 0.9926 76 1.0081
46 0.9930 77 1.0085
47 0.9935 78 1.0090
48 0.9940 79 1.0095
49 0.9945 80 1.0100
50 0.9950 81 1.0105
51 0.9955 82 1.0110
52 0.9960 83 1.0115
53 0.9965 84 1.0120
54 0.9971 85 1.0126
55 0.9976 86 1.0131
56 0.9980 87 1.0136
57 0.9985 88 1.0141
58 0.9990 89 1.0146
59 0.9995 90 1.0151
60 1.000 91 1.0156
61 1.0005 92 1.0162
62 1.0010 93 1.0167
63 1.0015 94 1.0172
64 1.0020 95 1.0177
65 1.0025 96 1.0182
66 1.003 97 1.0187
67 1.0035 98 1.0193
68 1.0040 99 1.0198
69 1.0045 100 1.0203
70 1.0050
Table based on Tables 7 and 25 of "Petroleum Measurement Tables," published by the American Society for Testing and Materials, Philadelphia.
Temperature correction is necessary because fuel density, or energy content of a given volume of fuel, changes with temperature. A baseline of 60° F is used. TMC offers the following example of temperature correction to 60° F for Group 2 fuels: Assume a tank has a liquid capacity of 100 gal. A test run is made that uses 50 gal. At the start of the run, the temperature is 75° F. At the end of the run, the temperature is 95° F. At 75° F, according to the group 2 column, 100 gal of fuel at 60° F would need to be 100.76 gal to have equal energy. At 95° F, 101.77 gal would be needed to have the same energy. The difference is 1.01 gal (101.77 - 100.76 = 1.01). The temperature-corrected addition is 50 + 1.01 = 51.01. Thus, 51.01 gal is the amount of fuel that would be used for all calculations for this vehicle on this run.
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How to order reprints of this article
For a free single copy of this article, write on company letterhead to: Reprint Editor, Commercial Carrier Journal, 1 Chilton Way, Radnor, Pa. 19089. Additional copies $2 each. Send prepaid check or money order.
54 COMMERCIAL CARRIER JOURNAL June 1996
Go to CCJ's FEATURES listings.
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Go to CCJ's MARCH 1997 MAINTENANCE & TECHNOLOGY column about TMC/SAE Type IV procedure.
#13
11-21-2005, 12:19 PM
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RE: Tailgate down - mythbusters!!!
ORIGINAL: livinginh
Plus you dont have to chase your tool box down the road when it falls out for no tailgate. Just proves, bed covers do more for saving fuel then tailgate down.
Plus you dont have to chase your tool box down the road when it falls out for no tailgate. Just proves, bed covers do more for saving fuel then tailgate down.
#14
11-21-2005, 01:19 PM
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RE: Tailgate down - mythbusters!!!
I'm with the people who say it was a good test and its a myth, I watched the episode and it was sweet. Its not like the Discovery channel is playing with the cars when the cameras off just to screw people over...why the hell would they do that?
And it was a 30 or 40 miles diffrence I think, maybe not that much. But its not like the truck with the tail gate up ran out of gas 100 yards down the road...its was quite a ways away. So in my opinion driving with it down is a myth.
Forget science for 2 seconds and look at reality and you have proof
Science is obviously needed but some things reality is much better. I mean look at comunism, looks great on paper but it just doesn't work in reality 
Also I got 17 highway in my truck then a few monthes later I drove with the gate down and only got like 15.5.
And it was a 30 or 40 miles diffrence I think, maybe not that much. But its not like the truck with the tail gate up ran out of gas 100 yards down the road...its was quite a ways away. So in my opinion driving with it down is a myth.
Forget science for 2 seconds and look at reality and you have proof
Science is obviously needed but some things reality is much better. I mean look at comunism, looks great on paper but it just doesn't work in reality Also I got 17 highway in my truck then a few monthes later I drove with the gate down and only got like 15.5.
#15
11-21-2005, 01:31 PM
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RE: Tailgate down - mythbusters!!!
heh, I only watch Mythbusters to see Kari 
Seriously, The show is good for debunking stuff, but not to a grain of salt. It's good TV and like what was said above, you need to do repeated tests, and cross the tests between both trucks. Just a single test could be coincidental..
Seriously, The show is good for debunking stuff, but not to a grain of salt. It's good TV and like what was said above, you need to do repeated tests, and cross the tests between both trucks. Just a single test could be coincidental..
#16
11-21-2005, 10:16 PM
#17
11-21-2005, 10:38 PM
RE: Tailgate down - mythbusters!!!
One last thing to consider about all of this, having your tailgate down while in motion is actually illegal in some states. Riding around with it down is possibly a quick way to get a ticket. Again, this of course all depends on your city/state ordinances.
