Blowin' Smoke

An Editorial by dieselmann
Volume 18; March 07: 6.4 PowerStroke

Released in February of 2007 in the 2008 Ford Super Duty, this newest version of the PowerStroke engine has been designed to meet the more stringent EPA emission standards for diesel engine, while maintaining the performance levels customers have come to expect from the Ford version of the International direct injected turbocharged diesel engines. Horsepower is 350 at 3000 RPM and torque is 650 ft/lbs at 2000 RPM. It has been said the 6.4 was developed to replace the 6.0 becuase of the problems with that smaller engine, but in actuality it was already being developed back in 2003 in anticipation of the emission regulations.

The 6.4 base engine is of the same design as the 6.0--two-piece crankcase with aluminum upper oil pan/windage tray; cylinder heads with four-valves per cylinder; single pushrod/rocker arm actuating two valves through a bridge; rear timing gear set. But that is where the similarities end.

Probably the most interest is focused on the new sequential turbocharger assembly. Often mistakinly called twin-turbo, the 6.4 has a standard (low pressure) turbo that feeds compressed air into a variable geometry (high pressure) turbo, which compresses the air further. Minimum boost is 26 PSI, but watching the factory boost gauge on the dash, peak boost is typically at 30 PSI.

The vanes in the high pressure turbo are electronically controlled with an electric actuator, and not with oil pressure as in the 6.0. The variable vanes and unison ring have been designed to reduce the chance of sticking. The VGT actuator is liquid cooled by a separate system from the engine cooling system. Compressed air from the high pressure turbo passes through a vertical intercooler before entering the intake manifold.

The intercooler has been moved to just behind the grille in front of all the other heat exchangers. The grille is attached to the hood on the 2008 Super Duty, and the front bumper has a integral step on top of it. This makes if very easy to damage the intercooler fins with your feet when standing on the bumper. Ford has said they will not warranty intercoolers for this type of damage. Place a thick pad or fabricate some sort of guard to protect the intercooler if you perform your own services or repairs, and monitor the condition of the intercooler if you have the truck worked on by someone else.

The fuel supply system on the 6.4 is basically the same as the 6.0, with a primary fuel filter/separator/fuel pump assembly on the frame, and a secondary filter on the engine. Both filters are replaced at the same interval. The water separator now has an actual drain lever instead of the plug used on the 6.0. Rotating the lever opens the valve to drain the filter. The secondary filter is larger than the one used on the 6.0, but still has the same 4 micron rating.

New for the 6.4 is the high pressure common rail fuel injection system with piezo-electric injectors. While technically the 7.3 and 6.0 PowerStrokes had a common rail system (all injectors fed from a common fuel rail and not individual lines), it was classified differently due to the high pressure oil system used to actuate the injectors. The high pressure oil pump has been replaced by a high pressure (up to 26,000 PSI) fuel pump driven off the camshaft at the rear of the engine. Built into the high pressure pump are computer-controlled fuel pressure and volume control valves. The high pressure pump supplies the injectors fuel through fuel rails under the valve covers. Fuel returns from the rails back to the tank through the same cooler used by the VGT actuator.

The piezo-electric injectors are designed to provide more precise fuel control through multiple injection (up to 5 injections per combustion event) with reduced noise. Fuel is supplied to two chambers in each injector: the high pressure (delivery) chamber at the nozzle, and the control piston chamber. The nozzle needle is held closed by a spring and by fuel pressure in the control chamber. The injector is actuated when the engine control module (ECM) sends a high-voltage signal to the piezo actuator at the top of the injector. The piezo discs in the actuator flex and press on a hydraulic check valve, which causes fuel pressure in the control chamber to bleed off. Fuel pressure in the high pressure chamber causes the nozzle needle to lift off its seat and fuel passes through the spray holes at the nozzle tip. The ECM deactivates the injector by reversing polarity to the piezo discs. This allows spring pressure to close the check valve, fuel pressure builds in the control chanber, and the nozzle needle closes, ending injection. The ECM alone controls injector operation, with no extermal IDM/FICM as found on the 7.3 and 6.0 PowerStrokes.

Most of the exhaust system on the 6.4 is an emissions device. Starting at the turbo inlet Y-pipes, there is a mini catalytic converter that is used to dry out the exhaust fumes running to the EGR system. Hopefully, this will eliminate any more problems with coked EGR coolers or valves or plugged up or erratic EBP sensors. There are two EGR coolers to reduce the exhaust gas temperatures before they reach the intake manifold through the valve. Since the function of the EGR vlave is to reduce oxides of nitrogen emissions by lowering combustion tempertures, the exhaust gasses have to be cooled before entering the intake. To monitor the effectiveness of the EGR coolers, there is an exhaust gas temperature (EGRT) sensor before and after the EGR coolers. The EGR valve has been redesigned and has a much stronger return spring than the one on the 6.0, to reduce sticking. The valve is cooled by the engine cooling system.

Exhaust gases flow from the manifolds into the high pressure variable turbo. The high pressure turbine outlet is attached to the low pressure turbine inlet. The turbo downpipe is 4" ID, double-walled. This is to retain exhaust heat to aid the function of the main catalytic converter. The ECM monitors exhaust temperature on two EGT sensors, one before and one after the cat, to determine converter efficiency.

After the cat converter is the diesel particulate filter. The DPF is a soot trap. It is designed like the PowerCore air filter, with alternating open and closed tubes to catch the soot and prevent it from passing out to the atmosphere. Periodically the soot in the DPF is regenerated, or burned. The ECM monitors exhaust pressure at the DPF inlet to determine if regeneration is required. To burn out the soot, the ECM will command fuel injection during the exhaust stroke of the engine. The ECM will monitor exhaust temperature at the EGT sensor after the cat converter, and at a third EGT sensor after the DPF to limit the internal tempertures to 1200 degrees. Regeneration converts the soot to ash.

DPF regeration frequency and duration is determined by drive cycle. Typically frequency is 100-600 miles between occurances and will last 10-40 minutes. Duration time is less if a constant speed over 30 MPH is maintained. Normal characteristics during regeneration include elevated idle of 1100-1200 in park/neutral that drops when the brake pedal is applied, increased white smoke in cold ambient temperatures, reduced engine response and power limited to 325 HP, change in engine, exhaust and induction sound, flutter on deceleration or shut-down, increased exhaust smell and temperatures, and lower economy.

Eventually, the DPF will plug up with ash and it will need to be replaced, but it is estimated this should not happen before 150,000 miles. However, oil consumption problems or poor combustion can cause it to plug up faster. The ECM will detect excessive regenertion events and set a code to that effect. Using fuels other than ULSD, ULS Biodiesel over B5, and/or engine oils that are rated other than CJ-4 may cause excessive regeneration or DPF plugging. In these cases, Ford will not warranty the DPF if it requires replacement.

Even the tailpipe on the 6.4 is part of the emissions system. Because of the high temperatures during regeneration, the dual tailpipes have louvers cut into them to draw outside air into the pipe and cool the gases exiting the tailpipes.

On the up side, the muffler on the 6.4 is more of a resonator, but I would not expect to see preformance exhausts for the 6.4 in the near future.

Maintenance is going to be an issue with warranty claims on the 6.4. Using engine oils with an incorrect API rating can result in engine damage and plugging of the catalytic converters or diesel particulate filter. Engine oils should be API service rating CJ-4 or CJ-4/SM or higher. If you are doing your own oil changes, check the bottle for these ratings. If you have your oil changes done for you, verifiy the shop doing the service uses the correct oil.

Oils I have verified with the CJ-4 API rating are:

Oil changes under normal driving conditions are performed at 10,000 miles. Under severe conditions (towing, long idle times, frequent short trips, off road, dirty/dusty conditions, using biodiesel) it should be changed at 5000 miles. Expect Ford to start requiring oil samples/analyses for base engine warranty claims.

Fuel filters are changed at 20,000 miles for normal use, and 10,000 miles for severe. The water spearator should be drained monthly. The air filter element is similar to the one used on the 6.0. It is recommended to inspect the filter at each oil chnage, regardless of the filterminder indication.

Trucks with the 6.4 engine only use the Motorcraft Premium Gold coolant, Zerex G05 (gold bottle), Peak Global Extended Life (gold bottle) or Peak Extended Life CF-EXL (silver bottle), with no added SCA/FW-16*. The VGT actuator/fuel sysytem cooler uses the same antifreeze as the engine cooling system. The coolant should be checked every six months for pH balance and freeze protection**. The service life on the Premium Gold coolant is five years or 100,000 miles*** on the initial factory fill. If the cooling system is repaired or serviced and tap water is used to dilute the coolant, the service life is reduced to 50,000 miles. To maintain the 100,000 service life, only use distilled water to dilute the Gold coolant. Do not use antifreezes that claim to mix with any color antifreeze, as these may not have the correct cavitation inhibitors needed in diesel engines.
*Trucks subjected to severe duty/special operating conditions should now have the gold coolant checked for nitrite level using the same strips as testing SCA in green coolant (disregard molybdate pad), and adjusted with FW-16 as needed. Levels should be more than 800 ppm/0.8 units per gallon. If the level is below 300 ppm/0.3 units/gallon, the coolant should be changed.
**Testing under severe duty/special operating conditions is six months/20,000 miles.
***Service life under severe duty/special operating conditions is 60,000 miles.

The 6.4 PowerStroke was designed to run on Ultra-Low Sulfur Diesel (ULSD) fuel. Biodiesel is permitted, providing it does not exceed 5% (B5). Biodiesel blends also have to be ULSD. If using biodiesel, in any percentage, oil changes should be performed at 5000 mile intervals, and fuel filters replaced at 10,000 miles. Using low-sulfur or high sulfur fuels will cause damage to emission components, particularly the diesel particulate filter and catalytic converters. Ford may require fuel samples if warranty claims are filed for these components or for fuel injectors.

Charles David Ledger; dieselmann2007

Questions or comments:
dieselmann@intellidog.com

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Previous Volumes:

May 99: Add-ons

June 99: Towing

July 99: Synthetic lubes and ELC's

August 99: Choosing a shop or mechanic

September/October 99: Fresno PowerStroke Rally;
dieselmann's Store

November 99: Winterization

December 99: Cooling system maintenance

January 00: Helping your mechanic

Summer 00: Prolonged Idling Damage

February 01: Fuel Economy

April 01: Diesel Motor Oil Comparison

July 01: Fuel Additives

July 02: 2002 Factory Transmission Temp Gauge

November 02: The Dreaded Cackle

February 03: 6.0 PowerStroke and Torqshift Transmission

December 03: Fuel Contamination

December 06: Ultra Low Sulfur Diesel Fuel

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