By G.R. Whale and Mike Levine, Photos by Greg Whale
In response to reader comments about observed low-end power output (or rather, the lack of measured output below 2,000 rpm) during our earlier dyno test of Ford’s all-new 3.5-liter EcoBoost V-6, we’ve rerun the test.
This time, we combined engineering resources from Ford and our friends at K&N Engineering. Ford graciously flew in an engineer from Dearborn, Mich., to participate in the testing at K&N’s headquarters in Riverside, Calif.
We also made sure we had two 2011 F-150s to compare on the same day on K&N’s SuperFlow chassis dyno – an EcoBoost V-6 and a 5.0-liter V-8. Both trucks were 145-inch-wheelbase models with four-wheel drive and 3.73 rear axles. The EcoBoost F-150 ($41,300) was a SuperCab FX4 with a 6.5-foot cargo box and 4,650 miles on its odometer. The 5.0 F-150 ($40,715) was a SuperCrew with a 5.5-foot cargo box and 3,130 miles. All the tires were identical: Wrangler SR-A P275/65R18 114T.
The SuperFlow eddy-current dyno is different from the Dynojet inertia-type dyno we’ve used in the past. Whereas an inertia dyno measures engine power at a vehicle’s rear wheels based on how fast it can spin heavy drums, an eddy-current dyno adds the ability to simulate a load on the trucks by using electro-magnets to add resistance to drum spin, as if they were pulling a trailer.
EcoBoost 3.5-liter V-6 F-150 on the Superflow dyno.
Both trucks were run in two-wheel drive, lashed down securely on the SuperFlow’s four spinning rollers.
Conditions were favorable the entire day. It was cloudy with a light drizzle. The temperature in the dyno cell was 68 degrees, barometric pressure was 29 inches and humidity was 45 percent. K&N used industry-standard SAE correction factors to determine the power ratings from both trucks, which account for environmental factors at the time of testing.
To keep both trucks cool, we used seven fans: three in the forward room wall, two squirrel-cage fans aimed at the radiator, one squirrel targeted at the EcoBoost’s turbo intercooler in the lower bumper and one directly under the right side exhaust.
EcoBoost on the Dyno
The EcoBoost gasoline twin-turbo direct-injection engine required more than six hours to test properly on the dyno because measuring its low-end power output was difficult.
At first, we encountered an issue accurately reading engine rpm on the dyno, even after the Ford engineer identified a specific wire for the dyno to "listen" to. Eventually, Ford and K&N decided to use vehicle speed to determine power output because the Ford engineer could receive the same data on his laptop that was plugged into the truck’s onboard diagnostic system as K&N measured with the dyno.
Both trucks were run in "2" gear on the dyno from a rolling start all the way to redline.
The GTDI truck was run with the F-150’s six-speed automatic transmission set in the "2" gear position. Ford’s engineer believed that 1st gear in the EcoBoost F-150 was too short to make low-end power, though there was lots of high-end power, 2nd was just fast enough to get the cams moving while 3rd tended to get the emissions catalyst too hot, which started to affect backpressure reducing power. K&N has also run a similar 2nd gear setup testing a 3.5-liter V-6 EcoBoost Ford Taurus with front-wheel drive.
Multiple combinations of throttle tip-in, inertia and time-per-pull and load tests were tried. Too much eddy-current dyno load to help the engine’s twin turbos build boost early started to smoke the tires. Tipping into the accelerator too quickly didn’t agree with the dyno, tripping a mode where the dyno reduced its load on the truck. Starting from a 9 mph rolling start at 1,400 to 1,600 rpm got around the dyno load reduction issue but didn’t allow time for the 3.5’s intake manifold air pressure to build to the desired level (48 inches, according to published output data compared with about 37 inches measured on the early rolling starts) until around 2,500 rpm.
Manifold pressure is measured like barometric pressure. It describes how much air will be mixed with fuel in the cylinders. The greater the air pressure, the more fuel and air can be mixed during combustion to provide extra power.
There was also the delicate balancing act of trying to keep the torque converter from slipping at low rpm under heavy load, so full power could be sent from the engine to the rear wheels, and keeping other engine power management variables, like cam and spark timing, in their sweet spots.
The torque converter in an automatic transmission takes the place of a clutch in manual transmission. It smoothly transitions gear shifts and disconnects the driveline from the engine at stops, so the engine doesn't stall. The TC has to be locked to push full power from the engine to the rear wheels.
EcoBoost’s advertised power runs are started from a rolling start with engine speeds as close to idle as possible, according to Ford.
Finally, after 10 setup runs circling the optimal dyno technique, we were able to reliably measure power output below 1,000 rpm all the way up to engine redline around 6,000 rpm.
The Superflow dyno data was exported "as is" or we would have plotted both engines on the same graph as we've previously done for easier comparison.
Peak horsepower was measured at 302.7 hp at 5,203 rpm, and peak torque was measured at 360 pounds-feet at 2,900 rpm. A steady-speed load test measured 400-plus pounds-feet of torque at the rear wheels.
After all the dyno finessing, our impression is that EcoBoost may not grunt out its full torque potential at low rpm in lower gears in full auto shift mode. It may do this so it doesn’t overwhelm a driveline component if a tire slips and then finds traction again. We might see full torque only at higher speeds, as we did in our original dyno runs on the Dynojet. However, we're not saying that EcoBoost doesn't make its published torque on the road in the real world because we've consistently seen EcoBoost F-150s outperform closely configured 5.0-liter F-150s when we've put both against the clock measuring zero to 60 mph times empty and pulling a heavy trailer (with identical and different rear axles). But in our tests, we've also repeatedly clocked the 5.0 with faster zero to 20 mph starts before EcoBoost really turns on the power from 20 mph to 60 mph. Slower zero to 20 mph times could also be caused by turbo lag, not torque management.
Ford's engineers say EcoBoost's torque is not limited at anytime.
We're also publishing Ford's engine dyno data (measured at the crankshaft instead of the rear wheels so you won't see parasitic losses from the drivetrain) for all of its 2011 engines, provided by the company. These are the same graphs Ford is using in its advertised power and torque figures. They were measured on an engine dyno according to the Society of Automotive Engineers International's J-1349 standard, which many vehicle manufacturers follow to rate engine numbers. SAE J-1349 requires the presence of an independent witness to be certified. It also uses simulated engine calibration and exhaust back pressure data from a chassis dyno to run the test, so the engine is tested as if it were in a vehicle.
5.0 on the Dyno
The 5.0 required significantly less time and effort to "hook up" on the dyno.
Three runs were conducted within an hour of completing EcoBoost testing. Peak horsepower was measured at 285.5 hp at 5,913 rpm, and peak torque was measured at 284.9 pounds-feet at 4,290 rpm. That’s about 10 to 12 percent less power and torque than we observed on the Dynojet.
Why the drop in power and torque from our original 5.0 dyno session a few weeks ago? It’s possibly due to several factors, including wholly different dynos were used, we didn’t run the 5.0 on the Dynojet with a load on its rollers and it took six hours to dial-in the GTDI truck for best power. The same setting was copied for the 5.0, which might not be ideal for a naturally aspirated engine.
Throughout the tests, the 5.0 demonstrated a healthy torque curve that looks broader and less peaky than the EcoBoost, though at a lower level of power. It also shows off the engine’s ability to steadily wind up power all the way up to redline.
We continue to be big fans of the 5.0 as an excellent all-around engine. We think this is supported by the on-road data we collected during our full drive test and earlier Dynojet session at K&N.
We look forward to seeing other magazines and enthusiasts test their EcoBoost V-6 and 5.0-liter V-8 F-150s on chassis dynos around the country. We think they may also encounter some of the same challenges we had trying to find the best way to test a rear-wheel-drive twin-turbo gasoline direct-injection engine. We have no doubt that the EcoBoost engine is delivering the power. It's measuring it accurately, especially at lower RPMs, that's tricky.
Regardless of where peak power output was measured on the dyno, both the 5.0-liter V-8 and EcoBoost V-6 are incredible performers on the highway. They are engines the F-150 has long deserved to have. To determine which is best for you, be sure to read our in-depth road tests of both engines. And if you think one engine has an advantage over the other, it’s good to know that F-150 buyers have this kind of choice in capable half-ton powertrains.
The 5.0-liter V-8 F-150 on the Superflow dyno.
Special thanks to K&N Engineering and Ford Motor Company for providing the trucks, facility and assisting with this test.