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7.3 and 6.0 Powerstroke Diesel Tech Talk
HEUI Fuel Injection System
The Powerstroke Diesel Direct Injection Turbo (DIT) Engine utilizes a unique fuel injection system. Absent from a normal fuel injection system are a mechanical injection pump and injection lines. The components which replace the traditional mechanical injection pump include a high pressure oil pump and reservoir, pressure regulator for the oil and passages in the cylinder head for flow of fuel to the injectors.
Fuel is drawn from the tank by the tandem fuel pump which circulates fuel at low pressure through the fuel filter/water separator/fuel heater bowl and then fuel is directed back to the fuel pump where fuel is pumped at high pressure into the cylinder head fuel galleries. The injectors are then fired by the Powertrain Control Module (PCM), which are controlled by the PCM but are hydraulically actuated by the oil pressure from the high pressure oil pump. This is what Ford Motor Co. calls a Hydraulic Electronic Unit Injection system, or HEUI system. The control system for the fuel injectors is the PCM and the injectors are fired based on various inputs received by the PCM.
What has happened since this system has been released on the Powerstroke Diesel is that poor performance and driveability issues are often blamed on engine oil that has foamed, thus preventing the oil from acting as an effective hydraulic fluid to operate the HEUI system.
Based on my experience what I have determined is that the concern with the oil foaming is not a major issue. Back in 1994 Ford used a silicone which leached into the oil and caused it to foam. When the customer experienced poor performance, stumbling on acceleration, hesitation and lack of engine they took it to the dealership and the mechanic at the dealership changed the oil and the problem went away.
Then what followed is many mechanics assumed that whenever a poor performing Powerstroke Diesel came in for service that there was an oil foaming issue and they told customers that the oil has to be changed often so it can act as a good hydraulic oil. Then Ford and International determined that a special anti-foamant additive had to be added on initial engine build oil fill only to eliminate the chemical reaction while the silicone was curing or when an oil pan is serviced and new silicone is used. The specific product that is used for this is Fleetrite Anti-Foam Concentrate CH1824392. That is how the oil foaming myth started.
Then what followed is that many mechanics would tell customers that oil foams and that Rotella T has to be used and that it must be changed often (typically every 3000-5000 miles) and whenever a Powerstroke is not running properly the first thing to suspect is the oil that needs to be changed. The fact is Rotella T and many of the other popular oils they like to recommend do not perform as well as AMSOIL in the ASTM D892 Sequence 1 and 2 Foaming Test while AMSOIL passes with flying colors. But even the oils that do not perform well on foaming tests, still perform well in the Powerstroke for operation of the injectors. Foaming is not a major problem in these Powerstrokes as the silicone leeching problem has been fixed. It is possible that under certain very extreme and rare conditions a performance problem can occur with a low quality oil that does not pass the ASTM D892 Tests, but it is rare. The anti-foamants do not rapidly deplete and are replenished with oil top-offs and filter changes.
In this first phase of the foam measurement test air is blown through a sample of oil that is maintained at a specific temperature for a specific period of time. When the air supply is shut off the foam volume is measured. This is called the foaming tendency. In the second phase of the test, the foam is allowed to dissipate for ten minutes and then the volume of foam is measured and reported as the foam stability. The foam tendency and foam stability can change with time in service. New oils will have lower tendency to foam and lower foam stability values while oils that are contaminated can have increased values. The additive package in a particular oil is critical in the oils ability to reduce/eliminate foam both when the oil is new and after extended time in service. Certain manufacturers oils have highly effective anti-foaming additive packages and should be considered in applications where foaming is of critical importance (AMSOIL is one of these manufacturers that performs exceptionally well in the ASTM-D892 Test).
Note that all oils will foam to a certain extent when agitated, however excessive foaming can lead to problems such as starvation at the oil pump inlet, or foam being drawn into the oil pump inlet with the oil. Foam is also detrimental to hydraulic valve lifter operation and the degree of oil film protection afforded by the oil. Certain motor oils, such as motor oils intended specifically for small high RPM engines typically have a special defoamant blended in the oil formulation. It is also important to note that excessively overfilling an engine crankcase can cause oil foaming, even with defoamants.
How does AMSOIL Synthetic Diesel Oils perform vs. Shell Rotella T:
Take a look at the varnish deposits in this picture below. These are the results of a severe high temperature deposit test. The one at the far right is AMSOIL Synthetic 15W-40 Diesel oil and the others are major brand petroleum diesel oils. (left to right: Chevron Delo 400, Cummins Premium Blue, Shell Rotella T,
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