When we spec’d out the engines for our LS3 vs Coyote Budget Shootout series, we established some overall guidelines for the builds. Among the criteria, a few aspects weighed heavily on the parts list – natural aspiration, street-friendly behavior, and more or less stock displacement played key roles in our directive.
We also wanted the engines to be durable, high-revving, and provide a canvas for easy modification beyond our original configuration for the shootout. For the Coyote, part of that plan included a set of 95 lb/hr fuel injectors from DeatschWerks. These injectors are capable of flowing significantly more than the stock 38.5 lb/hr pieces, which helped us future-proof the fuel system for subsequent modifications down the line.
Ford really did their homework on the mod motors, and the 5.0’s ECU can actually take a lot of tuning. – Chris Mills, DeatschWerks
But in gearhead circles there’s a common misnomer that using oversized fuel injectors serves as a detriment to performance and drivability in motors that can’t use the injector’s additional flow capabilities.
We sat down with the folks at DeatschWerks to get some information from fuel system experts about whether or not there’s any credence to the myth, find out more about the tuning capabilities of the injectors on our Coyote, and get a better overall view of the upgrade path for the fuel system of Ford’s venerable DOHC 5.0-liter V8.
The Coyote In Question
DeatschWerks 95lb (1,000cc) Fuel Injectors For Ford Mustang GT 2005-2015
For Ford, in particular, this had a fairly significant effect on the potential parts list. You can get all the details on the Coyote build here, but some of the key items of interest are the forged Manley Performance pistons (PN 598010-C), a set of street-friendly hydraulic camshafts from Comp Cams Stage 3 XFI NSR (PN 191160), and Aeromotive billet fuel rails (PN 14130).
In conjunction with the rest of the upgrades, the result was a peak output of 510.4 horsepower at 7,600 rpm and 398.4 lb-ft of torque at 5,400 rpm – a substantial bump up from stock 5.0 in a new S550 Mustang GT but still well within the realm of typical street performance.
“The stock fuel injectors on the Coyote 5.0 are, of course, dialed in for stock engine output,” says Chris Mills, senior technical specialist for DeatschWerks. “Once you start moving into basic bolt-on modifications, an injector upgrade isn’t a bad idea.”
While the larger injectors we selected for the Coyote are probably starting to make more sense now, the 95 lb/hr size we selected is still substantially larger than the fueling requirements of our modified 5.0. But there’s a method to our madness, and it involves not only testing a number of additional bolt-on parts with this motor, but also potentially throwing some boost at it in the future as well.
In the meantime, we still want the Coyote to behave as expected despite the perceived mismatch between the engine’s fueling requirements and the fuel injectors we have installed.
Fact Versus Fiction
“Ford really did their homework on the mod motors, and the 5.0’s ECU can actually take a lot of tuning,” Mills explains. “Using a typical handheld tuner like an SCT, a bone stock Coyote could run 95 lb/hr injectors – just change the calibration data and you’re good to go. The validation on these injectors was done on a showroom stock vehicle.”
But, it’s also important to realize that swapping out stock injectors for large ones does not automatically net performance gains.
“Until the original equipment injectors can no longer provide the fuel for the power your engine makes you don’t need to replace them. But once you start to introduce enough air into the equation that the fuel system can’t keep up and starts running lean, you’ve reached the point where an injector upgrade would be needed,” Mills notes. “With the Coyote, you often reach this point when you start swapping camshafts.”
It’s also important to keep in mind that injectors aren’t really considered a wear item – provided they’re used under normal conditions, they should function as intended throughout the life of the engine, so simply swapping out an old injector for a new one of the same type is unlikely to provide much improvement in horsepower and drivability.
However, moving from one injector technology to a newer one will yield benefits in some situations. For instance, moving from the older Bosch EV1-style fuel injectors used in the pushrod 5.0 found in Fox-body Mustangs to the newer Bosch EV14 MPFI injectors will provide improvements, as the EV14 provides better reliability, faster response, and improved fuel atomization.
Dialing It In
When it comes to fuel system upgrades on the Coyote motor, the injectors represent the first bottleneck in the equation. “The stock fuel pump is a pretty stout piece,” says Mills. “Unless you’re planning to run E85 fuel, which the stock fuel pump doesn’t particularly like, the fuel injectors are the first place to start.”
To help enthusiasts determine when they’re ready for an upgrade and what injectors would best suit their application, DeatschWerks offers online calculators to help remove the guesswork.
Since the idea behind larger injectors is to provide additional fuel beyond the capability of the stock system, the benefits in the power band are most often seen at higher RPM, near peak output levels. It makes sense when you consider that this is the point at which the stock component will have run out capability, and the larger injectors’ improved flow rate can continue to provide additional fuel to the mixture to create more power.
When it comes time to tune the injectors, DeatschWerks has made the process significantly easier for tuners by providing calibration summaries and injector data developed in-house on its website for every set that they sell.
“People sometimes ask why we don’t include this information in the packaging,” Mills told us. “And there’s a very good reason for that – we update this data regularly, and we don’t want to give our customers outdated information. A great example is Ford’s recent changes to the ECU values, which now measure fuel pressure in kPa rather than PSI, which caused some initial confusion for tuners. We want to ensure our customers have access to the latest and most accurate information available.”
As critical as proper fueling is, Mills says these components are often the unsung heroes of the performance equation. “Fuel system components do their work more or less behind the scenes,” Mills explains.
“It’s not like bolting on something like a supercharger, where you can pop the hood to show your buddies this shiny new performance part. But without the right amount of fueling, you may be leaving some performance on the table that you could easily acquire by simply installing the right injectors for the application.”
And while choosing the right injector for your build might seem like a task fraught with uncertainties if you’re not already a fuel system guru, DeatschWerks’ online fuel system calculators, up-to-date tuning information, and customer support for every step along the way certainly makes getting this upgrade right the first time around substantially easier.