New Holley Module Allows Coyote Swaps To
Keep Ti-VCT
Depending on the application, a Coyote engine swap could possibly
compromise one of the motor’s best selling points: its variable cam timing
control or Ti-VCT.
Designed to widen the engine’s torque band and eventually improve the
vehicle’s drivability, variable cam timing—also called variable valve
timing in other engines—requires specific instructions from the engine’s
ECU to operate properly. When a hot rodder planning a swap pulls a used
Coyote engine from a salvage yard or purchases a new Coyote crate motor,
he or she usually goes with an aftermarket ECU to keep the cost down or
provide more tuning flexibility once the engine is installed.
While aftermarket ECUs are great at controlling the fuel and spark along
with nitrous, boost and other engine features, they aren’t programmed to
handle the dedicated phasers that adjust cam timing to achieve optimum
power as the RPM and load change. Unless the user adapted a Ford ECU to
the swapped Coyote, the most sensible solution was to lock the cam phasers
so they wouldn’t default to an undesirable setting.
Two views of the Holley Ti-VCT module.
A new Coyote Ti-VCT control module from Holley EFI designed to work with
the company’s popular HP and Dominator ECUs now solves this problem. Not
only does it provide a solid baseline program that increases power and
torque over a locked-cam setup, but it offers the option of custom
programming if the user wants to play with the cam timing.
“Basically, this unit was developed for those who purchased a Coyote crate
engine but don’t want to remove the cam covers,” sums up Robin Lawrence,
director of EFI business development at Holley. “Most people don’t know
how to degree a single cam, let alone four cams. We were really looking to
offer a product that was plug and play.”
Pros and Cons of VCT
While there is always a debate over the pros and cons of variable cam
timing in a racing engine, benefits in a street engine are rarely
disputed.
“Most VCT isn’t good for over 8,000 rpm,” says Lawrence.
“On an all-out drag race car, I would not bother with VCT, and the reason
being your operating range is very small, usually a couple thousand RPM,”
says Holley engineer Ryan Witte. “In that small RPM range the cam movement
becomes quite minimal to maintain peak power, a couple degrees of
movement, and only relates to a couple percent in power at best. So, the
benefit versus the risk on that doesn’t add up.
The Holley Ti-VCT module eliminates the need to lock up the phasers if the
Coyote engine isn’t controlled by a Ford ECU.
“On a road race motor, there is a lot more benefit to it. You have a wider
RPM range with the lower RPM, low speed corners for example,” continues
Witte. “But there is a limit to what camshafts we can control. Once you
pass a certain point on the aggressiveness of the cam lobes, you cannot
control the cam movement anymore. The valvespring pressure and the rate of
the camshaft lobe will outrun what the oil pressure and the cam phaser can
reasonably control.”
Just what is Ti-VCT? Short for Twin Independent Variable Cam Timing, Ti-VCT
is Ford’s version of adjustable cam-timing or valve timing technology that
is now very common throughout the automotive industry. Early variable cam
timing was developed for single-cam applications and advanced or retarded
the cam from its standard orientation to boost low-end torque or improve
top-end performance—much like a knowledgeable tuner would do when setting
up an engine for a specific application.
Remember, engine performance is affected not only by how long the valves
stay open, but also when the valves open and close during their respective
cycles. And we also know that engines have different airflow requirements
at different speeds and loads. When the camshaft or the cam timing is
fixed, then airflow through the engine is an efficiency compromise between
high and low speeds, or there’s an emphasis on low- or top-end
performance.
The phasers can adjust cam timing up to 70 degrees on some Coyote engines.
What is a Cam Phaser?
With variable valve timing on a single-cam engine, a phaser actuated by
engine oil pressure advances or retards the cam position relative to the
“straight-up” position. That means that the intake and exhaust valves
advance and retard at the same time. The one notable exception to this
limitation is the “cam-in-cam” technology used on the Dodge Viper V10. It
was basically a hollow cam with a separate shaft inside. The outside tube
controlled the exhaust valves and the inside shaft controlled the intake
valves—which, in effect, established independent variable valve timing for
that application.
The Ford Coyote is a popular swap option for
street rods, older trucks and ’60s muscle cars because there are plenty
available in the salvage yards and Ford offers a performance-minded crate
option. There are also numerous induction options through the aftermarket.
With a 4-cam configuration like the Coyote, such intricate cam design is
not necessary to achieve independent control of the camshafts. The
Coyote’s Ti-VCT system is based around BorgWarner’s new CTA cam phasers.
Just what is a cam phaser? There are two basic components: an outer
sprocket meshed with the timing chain, and an inner rotor that is bolted
to the camshaft. As the inner rotor is moved and the rotation angle of the
camshaft is changed, the valve timing changes.
The inner rotor is basically a set of lobes. Oil fills the space between
the outer housing and the lobes. When there is no action, the rotor will
spin at the same rate as the outer housing. But if pressurized oil is
added to one side of the lobe and removed from the other side, the rotor
will move and change the position of the camshaft.
Understanding Phaser Operation
The BorgWarner system developed for the Coyote is more advanced than
conventional phasers that use just oil pressure to move the rotor. Called
Cam Torque Actuated (CTA), this system captures torsional energy in the
valvetrain to help actuate the cam movement along with the oil pressure.
This system requires less engine oil to operate than conventional variable
valve timing systems. These advanced features help the phaser respond
quicker off idle and don’t require special high-pressure oil pumps that
drag power down from the engine.
“Solenoids still operate the phasers, and the Holley module controls the
solenoids,” stresses Witte, noting that there is a difference in the
amount of control flexibility, depending on which engine is used. “It’s 50
degrees on Gen I Coyote engines and 70 degrees for the intake on Gen II.”
Independent control of each phaser allows engineers to manipulate the
engine’s breathing for the most efficiency or power. Variable valve timing
doesn’t change the duration or lift of the camshafts, it just changes the
timing when the valves open and close. Much of the strategy involves
adjusting the overlap period when both the intake and exhaust valve are
open at the same time at the end of the exhaust stroke. In fact, Ti-VCT
can eliminate overlap, if needed, to improve fuel economy or reduce
emissions.
“Overlap is what you really want to tune. Because you have a dual overhead
cam motor, you can play with the exhaust lobe and intake lobe
independently of each other, which gives you a lot more freedom on how to
affect the torque curve of the motor,” says Witte.
Improved Drivability is the Key
The beauty of the Holley Coyote Ti-VCT control module (PN 554-145) is that
the user doesn’t have to worry about programming in a cam timing strategy.
“The unit plugs into the Dominator or HP ECU and into Coyote sub-harness
that connects to the phasers and cam sensors,” explains Lawrence.
Shown are the phasers in place and the required electrical connections.
Because of changes between Gen 1 (2011-2014) and Gen 2 (2015-present)
Coyote engines, the Holley module must be set up so that the correct
pre-programmed table will be used at start-up. There is a bank of dip
switches on the back of the controller that the user adjusts according to
the instructions. A laptop is then connected to the ECU.
“You would load a base tune that we supply,” adds Witte. “It’s in the V5
software for either the early or late motors. In the V4 software, it’s the
early motor, only. For a stock motor, it would be–open the laptop, select
the tune, either ’11 to ’14 or ’15 to ’17, load it, do your TPS auto set,
start it up and drive it.”
Holley set up the base maps with certain compromises for the best power
and drivability in addition to reliability. And the base maps were
developed using the factory Coyote cams.
The Holley Ti-VCT is designed to be a plug-and-play companion to the HP or
Dominator ECU. In other words, you don’t have to go inside the engine to
lock up the phasers.
“A stock engine doesn’t allow you to do anything that would hurt the
motor. It may not make as much power if the cams are moved way too far in
one direction, but there’s no mechanical interference,” says Witte. “The
valves will never hit each other, or the pistons. In that regard, it’s
just tuning fuel and timing for the chosen cam position.”
Holley has tested its base map with aftermarket cams for the Coyote,
specifically the NSR cams from Comp Cams that don’t require stiffer
valvesprings.
“We have found we can control those just fine,” says Witte.
Default Positions Aren’t Performance Minded
The Holley module can deliver up to 50 degrees timing variance on both the
intake and exhaust cams for the Gen 1 engines and 70 degrees on the intake
side for the Gen 2 engines. Should the user want to change cams and
develop a custom map for the cams, the Holley module offers that option.
“If you were using one of the no-spring-required (NSR) cams, you would
flip the switch on the controller and use the tables in the Holley EFI,
and you could remap it for optimum performance,” says Witte. “With an
aftermarket cam, there is likely going to be some benefit to remapping the
cam positions.”
The primary motivation, however, for developing the Holley Ti-VCT control
module was serving builders who swap a Coyote engine into a hot rod or
musclecar and don’t want to lock the cams. Such a stance also begs the
question: What if I just leave the phasers and cams alone—don’t hook up
any wires or change anything?
“The Ti-VCT on the Gen I defaults to a retarded position, so they don’t
run very well,” says Lawrence. “On the Gen II Coyote, if you unplug the
VCT it will default to a central position, so they run pretty good. I
think our numbers are 40 horsepower down in default, but the engine will
run.”
The Holley control module also features diagnostic LEDs to inform the user
if a cam or crank sensor fails. The module does require the installation
of an external MAP sensor.
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