“Change is in the air.” Nowhere is this more apparent than
in the automotive technology found in our new generation of police, special
service and admin vehicles. Ford, General Motors and Chrysler have all
incorporated fuel saving and power-enhancing features into almost every make
and model they support. From improved gasoline engines to a wider selection of
diesel platforms, all serve to deliver better power, performance and economy.
So what are the motivators for this change? One is the
ever-tightening noose of vehicle emissions. With the emphasis on environmental
stewardship gaining ground, all manufacturers are doing their part to reduce
their “carbon footprint.”
Coupled with this “green” wave, is the government push for
improvement in fuel economy (CAFE). As of mid-2011,
an agreement was reached between the U.S. government and 13 large automakers to
increase fuel economy to 54.5 miles per gallon for cars and light-duty trucks
by model year 2025.
To begin with, the automotive industry is able to deliver on
all these changes by reviewing current technology. From internal and rolling friction
to a variety of fuel, all areas of potential efficiency gains were evaluated.
In the end, some striking discoveries were made.
First, fuel injection and combustion dynamics have made vast
advances recently, thanks largely to the work of European automotive engineers.
Key areas like fuel injection, piston design, air control, frictional loss, and
air-to-fuel ratios have all undergone remarkable evolutions. It is no secret
that engine designs have remained somewhat stagnant in recent years. So how
best to reinvent what we have, while keeping the best of what we need? That is
where automotive innovation comes into play.
While adopting more powerful and leaner operating engine
configurations, OEMs have successfully created a balance between environmental
compliance, while delivering on operational demands. Older engine technologies
are being systematically sidelined in order to bring forth newer engine
configurations that surpass anything we’ve seen so far.
Taking center stage and the backbone of these technology
changes is Gasoline Direct Injection (GDI) and Turbo Diesel Injection (TDI)
engine. To review, previous fuel injection models relied on indirect injection
of the fuel spray outside the combustion chamber at a stoichiometric ratio of
14.7:1 air-to-fuel. Typical piston compression ratios were limited to about 9:1
in gasoline and 20:1 in diesels due to the limits of squeezing this finite
volume of incoming air.
However, Direct Injection has completely reinvented this
piece of physics by allowing for more air to enter the engine while reducing
the amount of fuel required for ignition. Ultra-lean fuel mixtures as high as
65:1 have been achieved in some models while the average ratios hover around
roughly 25:1 on average. This is a quantum leap from the 14.7:1 limit from which we came.
One good example of this new
direct injection (gasoline) engine is found within the Ford EcoBoost. The EcoBoost
model is well on its way to becoming the most popular engine in its class. The
3.5L EcoBoost achieves an impressive 355-365 hp @5700 rpm, and 350 lb·ft
torque, and delivers power like no other. It contains some truly impressive
From twin variable turbochargers
spinning at 170,000 rpms to fuel injection pulses varying from low-pressure
ultra-lean micro droplets to richer 3,000 psi squirts, this engine can make
gobs of power at the mere touch of the pedal. Even the pistons have a specific
concave indentation, to facilitate high turbulence within the combustion
chamber for optimum fuel-air mixing.
All this comes with a credible
fuel economy rating of 19 City and 29 Highway mpg. This equates into about 20
percent improved mpg and 15 percent reduced emissions as compared to normal air
aspirated (14.7:1 air-to-fuel) engines of similar displacement.
The real magic to this Direct
Injection engines lies within the controlled and exacting dispersal of smaller
and fewer fuel droplets to optimize (and not waste) fuel. Smaller fuel droplets
create more surface area for super-critical spark ignition. Even the piston
rings have changed. Older engines relied on piston rings “pushing out” or
“sealing” the cylinder at roughly 20 psi force.
New direct injection engines use
“lower tension” piston rings. These new LT rings reduce frictional drag within
the cylinder by only expanding with as little as 7-8 psi force. This reduces
the frictional drag between lubricating engine oil and cylinder wall. Direct
injection engines in general, and EcoBoost engines in particular, represent the
optimization of engine power and performance.
That is the good news. Here is the
not so good. For with every improvement, there usually comes with some degree
of compromise. Significant problems can quickly develop within the EcoBoost’s
high-pressure (2150 psi) fuel injection system and combustion chamber. Fuel
quality, oil evaporation and hydrocarbon deposits are the bane of these
engines. In order to maintain and reap the benefits of this highly advanced
engine, there is no room for disruptive fuel injector fouling or oily piston
In older port-fuel injection, the
fuel spray had a cleaning effect on the intake valves and pistons, since it
washed them with every injection fuel pulse. Clean valves are good, dirty
valves are bad, it’s that simple. When EcoBoost intake valves accumulate oil
and fuel deposits, this disrupts the ability of the engine to gobble air and
disperse fuel properly. Our study shows progressive loss of power and economy raises
Under the ultra-lean injection in EcoBoost,
it is paramount to maintain the quality and quantity of fuel spray and
air-swirl dynamics. If you don’t, then you are likely to set a misfire code or
experience engine stumble. Impede and rob the cylinder of enough air, disrupt
the precise turbulence required for fuel ignition, and you might as well speed
dial your tow service. Under continued operation in this condition, it wouldn’t
be long before you start to risk creating irreversible engine damage through
As countless online videos can
show, direct fuel injection engines do not have a mechanism to clean the intake
valves. The intake valves only shuttle incoming air, and air does very little
cleaning. Adding salt to the wound is the fact that evaporating engine oil
usually migrates back into the incoming air stream through the PCV, which
further increases the amount of nasty goop that dries rock hard onto the
valves. So much material eventually coats the valve stems and tulip area that
combustion chamber sealing can be compromised.
Studies have shown that normal
pump fuel has little ability to keep the intake valves and pistons clean. However,
the periodic use of high-quality fuel detergents was shown to greatly reduce
the build-up of these interfering deposits.
Don’t lose hope. While EcoBoost
and similar DI engine designs do have some valuable gains albeit unique
sensitivities, they can be well-maintained by understanding a few important
points. Number one is that quality in delivers quality out. From engine oils,
to fuels, all play a key role in keeping these engines operating at peak
(Ed. Note: Future articles will address the value and
protection offered by full synthetic engine oils, engine oil analysis, and fuel
treatment in maintaining these highly engineered direct injection engines.)
Michael Belluomo is the Technical Service Manager for BG Products, Inc. He can be reached at firstname.lastname@example.org.