What is Pilot Injection?
Pilot injection is a small shot of fuel before the main injection event that quiets the engine and
helps with mileage on a diesel engine. The HEUI Fuel System in the 6.0L was originally designed
around electronic Pilot Injection, but was removed early in the release of the truck(mid 2004) due
to issues with rolling idle and rough cold starts. Ford also updated the Injectors in the truck,
which greatly increased reliability but PI was gone forever...or was it? Through the years, we've
spent a lot of time testing PI in the 6.0L trucks and have offered it as an option. However, due to
the need for both PCM and FICM tuning, it's not easy to make sure each truck is up to spec to
accept it. Also, quality of the injectors and injection system(fuel and oil) can cause PI not to
operate well. Even the type of oil used can impact Pilot Injection.
Below are snippets from a Ford Motor Company Press Release:
"Pilot Injection: By delivering small quantities of fuel into the combustion chamber prior to the
main injection event, the combustion process is both smoother and quieter."
"The new diesel will offer up to 10 percent better fuel economy and 20 percent lower emissions.
The new diesel also has reduced noise levels and has improved speech intelligibility while driving
by more than 20 percent."
Leading these is the introduction of the first closed-loop control system for diesel engines, called
Accelerometer Pilot Control (APC), which allows the Engine Management System to ‘analyze the
quality of the combustion.
Information from the APC allows injection to be adjusted as conditions change, ensuring that the
system is always correctly calibrated. The major benefit of APC, combined with Delphi’s new
generation, fast-acting compact solenoid injector, is that it allows exceptionally precise control of
pilot injection.
These tiny volumes of fuel, injected before the main injection pulse, smooth the start of
combustion, eliminating the pressure spikes that produce the ‘clatter’ associated with previous
generation diesels.
Existing technologies can provide a single pilot-injection event with a volume of around 1-2 mm3
at low injection pressures, but typically suffer from reduced metering accuracy during their life on
the car, at idle or higher pressure.
Engine designers need both low pressures for a quiet idle and higher pressures because this
allows cylinders to be fueled more quickly and to have a better spray pattern, leading to improved
torque and reduced smoke.
The Delphi system allows pilot volumes across the pressure range that remain stable between
injectors throughout the engine life.
The pilot injection on the 6.0 is controlled by the PCM whereas the split shot injection on some
7.3's is a mechanical function of the injectors.
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