algorithms in their transmissions, and all systems, including the brakes, work at their best. Some trucks require ten or more brake applications. These systems require more work. The goal is to have the least number of brake applications as to not overheat and wear them out. There are two runaway truck ramps on this stretch of I-70 that serve as a constant reminder of the downhill danger. We monitor transmission and engine temperatures on all runs. Transmissions can heat up as they work hard on the way down.
Ike Gauntlet: The Way Up
A truck’s engine and transmission will be stressed to the maximum, gaining more than 2,300 feet of elevation over just eight miles. The maximum grade of the climb is 7 percent. The engine will be starving for oxygen and struggling to make power at the finish line, which is 11,158 feet above sea level. The test is to use maximum throttle input on the way up in order to maintain the 60 MPH speed limit (or the maximum speed the truck is able to maintain). The driver makes his or her best effort to not go over the 60 MPH speed limit. Cruise control systems do not work under these wide open throttle conditions. This is a serious test for the driver, as very slow moving semi-trucks and other vehicles are obstacles to maintaining momentum and staying at or near 60 MPH.
We reset each truck’s trip computer at the start of the test. We time each run up the mountain and record the trip’s MPG as reported by the truck’s computer.
At the end, each truck is scored on a scale of 100 points. The Ike Gauntlet scoring system allows a maximum score of 25 points for the downhill section, uphill time, uphill MPG, and average subjective score. The truck loses one point for each brake application on the way down. The benchmark time up the hill is eight minutes. Every five seconds over the benchmark time subtracts a point from the truck’s overall score. The truck cannot gain points for going under eight minutes. The benchmark MPG number is 6.0 MPG. Every 0.2 MPG below that, and the truck loses a point. The truck can gain points for doing better than 6.0 MPG.
2016 Ram 1500 and Ram 3500 HD Dually
The Ike Gauntlet test is extreme and may seem unreasonable to some. It is a challenge that many truck owners and truckers/transporters must deal with on a regular basis. If a truck does well towing on the Ike Gauntlet, you know you have an excellent towing machine, no matter where you live.
How Does Elevation Affect Horsepower?
We are based in Colorado, just north of Denver. We have easy access to the Rocky Mountains, be it a challenging off-road trail or the difficult Ike Gauntlet towing test. Still, we must deal with the negative effect of high elevation every day. You may not be worried about high altitude where you live, but you still need to consider negative effects of high humidity and hot temperatures.
An internal combustion engine is an air pump at its core. It sucks in air and the oxygen in it, adds fuel, makes power, and spits the remains back out as exhaust. Altitude, relative humidity, and ambient temperature are the three factors that can combine to kill horsepower and torque that your engine produces. You want to haul and tow a lot with your truck, and every horsepower and pound-foot of torque matter when you load up near the limits.
Should you care about this? If it’s a nice 70Fº morning with relatively low humidity and you are at sea level, then no. However, a hot summer day and high humidity will have a noticeable effect on acceleration and grade climbing ability, especially when your air conditioning is set on full blast.
The SAE provides standards by which trucks, and all vehicles in general, are measured against. The SAE J1349 standard (revision June 1990) provides a formula to calculate relative horsepower for naturally aspirated engines.
Turbocharged and supercharged engines, especially those with intercoolers, help alleviate negative effects of your surrounding environment. However, all turbochargers and superchargers are not created equal. Some are more efficient than others, but none are able to give you all 100 percent of power in heat or at high altitude. Thus, this formula only applies to naturally aspirated engines.
You can easily find relative horsepower calculators on the Internet. Just get the relative barometric pressure (measured in inches Hg/Mercury) and relative humidity percentage (percent) using your favorite weather information provider. You also need the current ambient temperature (degrees Fahrenheit) and the elevation (feet). Get these four numbers plugged into a calculator, and you get the percent of horsepower you are currently producing.
For example, our test track is located at 5,200 feet above sea level. Consider a barometric pressure of 30.08 in Hg, relative humidity of 25 percent, and temperature of 72Fº – the truck being tested produces only 82.4 percent of its rated horsepower. The big bad 6.2-liter EcoTec3 V8 in your GM pickup truck that is rated at 420 horsepower and 460 pound-foot of torque is making about 346 horses and 379 pound-foot of twist at our test track.
Okay, so you don’t live north of Denver, Colorado. How about Dallas, Texas? Elevation near downtown is 430 feet. A typical June day could bring a temperature of 95Fº, relative humidity of 89 percent, and barometric pressure of 29.96 in Hg. Your truck is making 93.4 percent of its power on that day. That same 6.2-liter V8 is now at 392 horsepower and 430 pound-foot of torque.
Naturally aspirated engines at the top of the Ike Gauntlet are losing about a third of their standard power rating. That big GM V8 is making 279 horsepower and 305 pound-foot of torque up there.
TOWING HIGHWAY MPG:
THE DAILY GRIND
The extreme Ike Gauntlet test is all well and good, but what about a more real-life example of how a truck performs? How does the truck do at the daily grind? Enter the towing highway MPG test! Why perform a towing MPG test on the highway?
Many truck owners spend time towing a trailer on a highway. They might be pulling a U-Haul trailer across country, hauling an equipment/supplies trailer to a job site, taking a camping trailer to the next adventure, or towing a boat for a relaxing day on the lake. People like Mr. Truck tow horses or livestock! Towing on a highway is something most of us can relate to.
Any meaningful test requires control of the environment. We picked a highway loop that measures precisely 98 miles on the Interstate I-76 northeast of Denver, Colorado. This stretch is not heavily traveled and the highway itself is relatively flat. It’s about as flat as an Interstate can get in Colorado.
2016 Toyota Tundra TRD Pro
We leave the truck stop and go forty-nine miles in one direction, and then return the forty-nine miles back to the same fueling station. We use cruise control set at 70 MPH for all runs. Although this stretch of the highway has a 75 MPH speed limit, we run all highway MPG tests at 70 MPH. This allows us a better margin of safety, as this stretch of highway can get windy.
The EPA rates midsize and light-duty (aka half-ton) trucks for city, highway, and combined MPGs, but they do not give a rating for trucks when towing a trailer or for heavy-duty pickups. This is where we come in.
We use a “double-click” method to top off the fuel tank before each run. We let the pump click the first time, we wait thirty seconds, and then manually add fuel until the pump clicks and stops for the second time. We use the same fill-up method when we return to the same pump after ninety-eight miles on the highway. We calculate the real-world MPG and also compare the results with the reading from the truck’s trip computer. The two results almost never match exactly. The number we finally
