Photos and Words by Jim McCraw; above photo courtesy of Ford
Ford Motor Co. made some history over the weekend when it did a complete engine tear-down and inspection of a "torture tested" 3.5-liter EcoBoost twin-turbo V-6 used in the latest F-150 at the 2011 North American International Auto Show in Detroit.
Auto shows, like NAIAS, typically showcase the latest metal in fancy displays bathed in brilliant lights and staffed with beautiful spokesmodels. They’re about as far as you can get from the garages that all cars and trucks will eventually require a visit to for service and maintenance. But for an hour Saturday, Ford turned part of its spotless blue and white display space inside Detroit’s Cobo Hall into a service bay for the last chapter of the F-150 EcoBoost torture test.
The front of the 3.5-liter EcoBoost V-6 prior to the start of the teardown in front of an estimated audience of more than 1,000 people at the 2011 Detroit auto show.
In case you’re one of the three or four people who haven’t been following the F-150 EcoBoost torture test story online, here’s a recap:
A production EcoBoost V-6 engine, serial number 448AA, was randomly selected off the assembly line at Ford’s Cleveland engine plant. The dual-overhead-cam power plant was shipped to dynamometer cell 36B in the Ford Dearborn engine labs and run for 300 hours to replicate the equivalent of 150,000 customer miles, including repeated temperature-shock runs when the engine was cooled to minus 20 degrees Fahrenheit and then heated to 235 degrees.
The engine was then shipped to Ford's Kansas City truck plant and installed in an F-150 4X4 crew-cab pickup. It was driven to Nygaard Timber in Astoria, Ore., and put to work as a log skidder, dragging a total of 110,000 pounds of logs across the ground to demonstrate its 420 pounds-feet of torque.
The front engine cover, intake manifold and heads are removed from the engine to expose the valvetrain.
From there, the truck was driven across the country to Homestead Miami Speedway, where it was hooked up to a trailer carrying two of Richard Petty’s Ford Fusion racecars, a load of 11,300 pounds, and run continuously around the track for 24 hours, averaging 82 mph and covering 1,607 miles.
It was then taken to Davis Dam in Arizona, where it bested both the 5.3-liter Chevy Silverado V-8 and the Ram 5.7-liter Hemi V-8 in an uphill towing contest pulling 9,000 pounds up a 6 percent grade on Highway 68.
Finally, the 3.5-liter twin-turbo EcoBoost engine was shipped to Mike McCarthy’s race shop in Wickenburg, Ariz., and installed in his 7,100-pound F-150 race truck. McCarthy practiced locally for 1,200 miles and raced the truck in the SCORE Baja 1000, the toughest off-road race in North America, finishing first overall in the new Stock Engine class after 1,062 race miles.
A close-up photo of three pistons still inside their cylinders. Note the carbon buildup on the piston crowns.
McCarthy said the engine’s fuel economy was so good compared with his previous V-8 engines that he was able to skip two planned fuel stops during the Baja event, which helped him win the class.
After Baja, the thoroughly thrashed and raced engine was shipped back to Ford headquarters in Dearborn, Mich., and dyno-tested once again. It was found to produce 364 horsepower and 420 pounds-feet of torque, just one horsepower less than its rating and exactly the same output as its nominal torque rating, according to Ford.
A leakdown test was performed to measure how well the engine’s 24 intake and exhaust valves and piston rings were still able to seal the cylinders. One cylinder was found to have a cautionary 13 percent air loss past the combustion chamber’s seals, while all other cylinders were acceptable with single digits of air leakage.
Pistons and crankshaft displayed on a parts table.
Oil pressure at idle on the dyno was normal, in the mid-40 psi range.
After the dyno, engine 448AA, which had never been opened or inspected, was shipped to the Detroit auto show where, on Saturday, it was torn down for inspection in front of a live audience of more than a thousand Ford engine enthusiasts and their families.
The teardown was narrated for the audience by Jim Mazuchowski, Ford’s chief engineer for V-6 engines. Powertrain engineer Phil Fabien explained the advantages of things like turbocharging, direct fuel injection and twin independent variable cam timing while engine technicians Chris Brown on the right bank and Chris Rahill on the left bank took the engine apart using a pair of air wrenches and hand tools.
The engine's four camshafts - two per cylinder bank to control intake and exhaust valve timing.
As they went, the engine parts were laid out on three huge tables so that when the tear-down was complete, the engineers and the audience could take a closer look. During the tear-down, engineers Steve Matera, Kirk Sheffer and Jeanne Wei organized the parts and made some key measurements.
Valve lash, which measures valvetrain clearance between the camshafts and valves, was checked at 0.17 mm on the intakes and 0.38 mm on the exhausts. That’s well within normal range for both, according to Ford. Crankshaft end play was measured at 0.12 mm, also acceptable.
The timing chain, which controls valve timing and synchronizes engine operation, was still within normal tolerances. With age, a timing belt loses tension, and a hydraulically operated timing chain tensioner is used to compensate for slack. The tensioner has 10 teeth that work like a ratchet to maintain tension. The EcoBoost V-6 used three teeth, well within the timing chain’s operating specs.
Exhaust side view of one of the engine's two turbo assemblies.
We didn’t get a photo of the valves, but they had carbon deposits similar to that found (and seen in pictures) on piston combustion surfaces.
Visual inspection of the cylinder heads, twin turbos, piston crowns, ring lands, rod bearings and cylinder bores by the engineers and your correspondent showed no major signs of anomalous wear after 163,000 miles of endurance testing. The main bearings showed cosmetic grooves but not excessive wear through the metal.
Engineer Wei said each and every part would be taken back to Ford’s labs to be checked with scales, cameras, lasers, micrometers and other measuring tools to get the final details on the rich, full life of EcoBoost V-6 engine 448AA.
You can see the disassembled engine with your own eyes until Jan. 23 at NAIAS.
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