More Ford Coyote Engine Tech!
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In-depth Look at The Evolution of The Coyote Engine
It’s payoff time. For the last two installments in the “Fake Snake” project 1999 Mustang GT, we’ve detailed the process of swapping the original 4.6 two-valve Modular motor for a new second-gen Coyote crate engine from Ford Performance.
The actual swap itself was pretty easy. With Paul Connor at Pro Dyno leading the way, we had the 4.6 out and the Coyote in its place and hooked up to the T45 transmission in less than a day and half, but that was only a small part of the story.
Much more time and effort was required getting all the support systems back online to get the Mustang running properly. That included an upgraded radiator from Fluidyne and a pair of 12-inch SPAL electric fans to improve cooling, a new in-tank fuel pump system from Aeromotive to feed the beast, and all the wiring necessary to keep components communicating properly. The idea was to over-spec all the supporting components to be able to handle at least 750 hp.
By far, the trickiest task was the wiring. Along with the Coyote engine, we also used one of Ford’s engine control packs that provides a wiring harness, engine control module, throttle pedal, and other components to power the engine and its drive-by-wire throttle. The control pack also comes with clear instructions for installation, but since Ford cannot know the particulars of every car and truck the engine will be swapped into, the instructions cover only the engine and control pack.
If we had endeavored to swap this combo into a carbureted car, this would have been a piece of cake. Nevertheless, our 1999 Mustang GT already had a computer of its own that needed to remain, thus adding months of complexity. It would have been nice to throw out the original ECM with the 4.6 engine, but it is used to control non-powertrain functions on the car, so Connor worked until he had both computers controlling their appropriate jobs—the new ECU running the engine, and the old ECM running everything else in tandem.
With that, the car fired up for the first time with its new Coyote powerplant. It wasn’t perfect. With long-tube headers, a crossover pipe from BBK, and a free-flowing intake from JLT, the engine still ran, but struggled finding a consistent idle speed. It also ran so rich you could tell with just your nose.
After 300 or so easy miles to allow the engine to break-in, we took the Fake Snake back to Pro Dyno so that owner Dan DeSio could work his magic. Pro Dyno specializes in Fords and draws cars to Fort Mill, South Carolina, from all over the eastern seaboard.
To protect the new Coyote, DeSio didn’t make a power pull when we knew the tune wasn’t right. Ford rates the 2nd gen 5.0L Coyote with 11.0:1 compression at 435 hp (at 6,500 rpm) and 400 lb-ft of torque (at 4,250 rpm). Allowing 15 percent drivetrain loss for the T45 five-speed manual trans and 9-inch Quick Performance rearend, that predicts approximately 370 hp at the rear wheels.
With this place-holder goal in mind, DeSio started by loading up one of his own tunes based around parameters specific to our modifications he knew would be safe for a primary pull. After that, he brought the air/fuel ratios into line, fixed the surge at idle, improved the overall driveability, and increased the power output significantly.
DeSio uses both SCT and HP Tuners depending on the situation, and stresses that he only tunes engines in person. Tunes over the Internet are popular, but DeSio says he feels you can miss a lot when you are tuning an engine from another state and you can only go by the gauges. “I’ve been doing this a long time,” he says. “And not to brag, but I can feel a lot sitting in the driver seat while I make a pull. That has helped me a lot of times find potential issues more quickly than I could have if the car was in another state. The data is important, but you are limiting yourself if that is all you use.”
Besides simply sitting in the seat, DeSio says he also likes to be able to look the car over himself. Some things, like the location of the blow-off valve and mass air sensor on a turbocharged engine, or the type of fuel pump or injectors used, can affect how he attacks the tune.
“I run into a lot of people who think new cars are very generic and you can fix anything with the keyboard, and that’s just not true,” he explains. “New cars are very different.” For example, DeSio warned us ahead of time that the Coyote would feel sluggish at low engine speed. Part of that comes from the relatively small displacement (the 5.0L Coyote is smaller than any LS) with a short 3.65-inch stroke. This has mostly been overcome in modern Mustangs with transmission and rear-gear choices, but the T45 five-speed in our 1999 GT simply isn’t geared to work best with the Coyote’s high-revving torque curve. We’ve gone with a lower 3.70 gear ratio (compared to the stock 3.27), but a TREMEC or MT82 pulled from a wrecked Mustang might be something to consider in the future.
DeSio says before he ever sees a car, he prefers a new customer spend some time with him on the phone discussing both his or her goals, and the car’s equipment as it currently sits. Typically, he wants to know such details as the injectors, the location of the mass air sensor, the fuel pump type and manufacturer, and other modifications that have been done since the car came off the production line. The idea is to eliminate any potential problems and make necessary changes before hauling your car to the dyno and then finding out you’ve got work to do before you can actually start making power numbers.
“The mechanicals on your car have to be right,” says DeSio. “You can’t just throw a bunch of parts at it and expect your tuner to be able to work miracles and get it all to work together. You can’t fix everything with a keyboard.”
One area we were concerned with was the drive-by-wire throttle. This requires a new fuel pedal to replace the old mechanical linkage. We used an aftermarket billet adaptor to bolt it into the ’99 Mustang, but there were concerns we might not see full engagement of the pedal. DeSio then “sped up” the throttle response for snappier engagement, but he also confirmed we were—more importantly—getting wide-open throttle at the correct time. Interestingly, you don’t want the throttle body blade opening a full 90 degrees. Instead, DeSio sets it to open 85 degrees at WOT. Because of the width of the throttle blade shaft, you don’t see any more airflow beyond 85 degrees, and keeping a slight angle on the blade helps keep the throttle from sticking, and we’re big fans of not having to worry about uncontrolled acceleration.
So how did we do? After making several dyno runs with the numbers increasing each time, DeSio squeezed out a surprising 432 hp at 6,500 rpm and 397 lb-ft of torque at 4,300. That’s at the rear wheels, which means we are somewhere around 475 hp and 455 lb-ft of torque. That’s an improvement of 40 hp and 55 lb-ft.
On the street, the upgrade in power is quite noticeable. The throttle is crisper, and the power just keeps climbing as the revs increase. This worn-out Mustang that we picked up for $1,500 has turned out to be a lot of fun!
Dig Into the “Fake Snake” Coyote-Swap Archives Here!
How-To: Coyote Swap in a 1999 Ford Mustang
Status Update: Project Fake Snake Coyote Swap
The Swap Begins: Project Fake Snake Gets It’s Coyote Crate Engine
Prepping a Coyote Crate Engine for an SN95 Mustang Swap
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