Anyone who was around during the heyday of the Fox Body Mustang (back when they were considered “late model” not “classic”) remembers the challenges of upgrading your fuel injectors. There was no messing with the ECU to account for the new injectors (unless you were running an expensive piggyback system or standalone ECU). Your option was to buy a calibrated mass airflow (MAF) sensor for the injector size you were using.
You also had to be concerned with making sure your injectors were sized perfectly to your combination, since going too big on the top end would cost you idle quality on the low end. While that might seem like a relatively straightforward, convenient solution — match your injectors and MAF to your combo — if you planned your build in stages, you would have to factor in several sets of injectors and MAF sensors along the way.
While the Retro 5.0 engine build is to relive the 5.0 heyday, we’d like to avoid amassing a mountain of injectors and MAF sensors. Luckily for us, in the past several decades, technology has come a long way. Those advancements have really rendered a lot of those original concerns obsolete. Here, we’re going to dive into some of those previous concerns and their modern solutions.
Modern Fuel Injectors
Obviously, one of the big challenges in a project like this is that performance will be progressing in stages with the project. Our fuel demands in the first round of testing are significantly different than in the second, third, and fourth rounds of testing. Based on historical data, our first trip to the dyno would likely be handled by the OEM 19 lb/hr injectors, or possibly a set of OEM Corba 24 lb/hr injectors, which would give us a little more headroom.
For the next round of testing, we probably would have upgraded to 30 lb/hr injectors to make sure we had enough injector. Then, the typical path would have probably led us to 42 lb/hr injectors. Beyond that, we would have been getting into some more specialty injectors. Also keep in mind, that each one of those injector swaps would have had the associated cost of a recalibrated MAF sensor.
However, the concern of calibrating a MAF sensor to our injectors is a non-issue for two reasons, and both of those relate to the fact that we are using a Holley Terminator X to control the engine, right from the start. Besides eliminating the mass airflow sensor altogether, it also has the ability to control a large range of injector sizes.
Addressing our second concern of yore, we reached out to Deatschwerks to talk about injector sizing, and the concerns about going “too big,” and the potential pitfalls, only to learn our concerns were a thing of the past. “Due to advancements in injector technology and tuning ability, the landscape is different,” explains Deatschwerks Technical Specialist Dakota Bowman.
“No one wants to buy multiple sets of injectors and if you can ‘make do with an injector that is too large, why not? I use quotation marks, as injector data and injectors have improved so much in the last 20 years that an injector thought to be ‘too large’ before, will work perfectly fine most of the time. There is a limit but, that whole limit has shifted quite some distance.”
While discussing the issue of “too big” Bowman mentioned several scenarios where you can easily double the size of the injector without a second thought. “As an example, let’s use someone shooting for 400 horsepower from a naturally aspirated V8 build, but they have plans to eventually make 800 horsepower boosted on E85,” says Bowman. “At 400 horsepower I would recommend about a 35lb/hr injector yet at the 800 horsepower mark on E85 I would recommend in the neighborhood of 90 lb/hr. That is more than double the size yet, it would idle and cruise perfectly fine at both levels on the 90 lb/hr injectors.”
Shifting to our project in particular, the bone stock Retro 5.0 engine, as it came out of the Thunderbird, was equipped with yellow-top 19 lb/hr injectors. The 1993 Cobra, which we’ll be imitating in our first trip on the dyno came with 24 lb/hr injectors from the factory. Our ultimate goal, which I’m not sure has ever been publicly disclosed before, is to max out a centrifugal blower from the typical Fox Body kit. On paper that is about 750 horsepower at the crankshaft.
Using DeatschWerks handy calculator we see that 750 horsepower on gasoline would need a set of the 60 lb/hr injectors. But, Bowman asked us a question that we hadn’t even thought about previously “Are you going to play with E85 at all?” Our dumbfounded silence (since E85 is non-existent where we live, so never even came up in thought) was met with an audible smile. “You’re going to want the 78s [lb/hr], then,” he told us.
We’ve used Deatchwerks injectors on several projects in the past, and besides being built like tanks, one of the features we really like, is getting a set of injectors that is ready to go, out of the box. Now, “ready to go” can mean different things to different people, but to us, that means having every possible bit of attention to detail already taken care of for us.
At this point in the game, I think everyone expects some level of injector matching from a set of new injectors, but the Deatschwerks injectors take this to a totally different level. “Not only do we match our sets, but we also do what’s called dynamic balancing,” Bowman explains. “That means we test at idle conditions as well as cruising, high load, and static conditions. This ensures no random hesitations from inconsistent fuel delivery from injector to injector, no matter the demand. Nothing is more annoying than a car bucking while cruising through a parking lot or pitlane having everyone stare at you. Race cars no longer need to run rough or give up drivability.”
That testing isn’t something you just have to take the company’s word for, either. They include a test report with each set of injectors. Listed on it is the testing of each serial-numbered injector in the set. “Our standards fall within what most OE set’s match. Fortunately for them, matching at the flow rates they have is much easier. Variation is very little when the injectors are small. We make sure to keep the same standard from our smallest injector (35lb/hr) to our largest injectors (215lb/hr),” says Bowman. The proof is clear, as you can see on our test report.
Additionally, the company supplies a comprehensive list of tuning data, to be able to plug into your tuning software, be it a flash tuner or a complete standalone system. Since the Terminator X kit we’re using (which you’ll see profiled in an upcoming article) is designed as plug-and-play for an ’87-’93 Fox Body, we went with the standard EV1 connector, which is actually an adapter fitted onto the injector plug, keeping everything plug-and-play.
Old Reliable — Aeromotive Fuel Rail And Regulator Kit
While technology marching on is great for the enthusiast, in some areas, good technology is timeless. Because it was gotten right the first time, and still works to this day, Aeromotive’s fuel rail kit (P/N: 14102) for the 5.0L engine has remained largely unchanged over the past two decades. That kind of longevity tells you something about a product in a market full of competition.
Besides being a complete, reliable kit full of high-quality components, Aeromotive’s Fuel Rail System for 1986-‘95 Mustang GT and Cobra solves some issues for taking our project engine to the dyno, while offering easy installation in a factory vehicle. The kit comes with Ford quick disconnect to AN adapters so that you can connect to the OEM connections under the hood. But, for our initial purposes, it provides an easy, secure connection to the dyno’s fuel system.
Additionally, upgrading to the Aeromotive kit takes the OEM non-adjustable regulator out of the small OEM rail, and replaces it with a high-performance external fuel pressure regulator. This will not only better, more reliably regulate fuel pressure, but allow us to adjust it for our specific needs on the dyno over time. Let’s take a look at what all is included in the kit.
The core of the kit (and its namesake) is the pair of billet aluminum fuel rails (P/N: 14101). Anodized in Aeromotive’s signature red finish, the rails feature a 5/8-inch bore capable of flowing enough fuel for 3,000 horsepower along with ORB-08 ports on each end, along with a center ORB-08 port specifically for the Mustang application. The CNC-machining offers an unmatched fit and finish, while the steel mounting brackets make for easy, secure mounting of the rails to the intake manifold.
A1000 Return-Style Regulator
The A1000-6 fuel pressure regulator (P/N: 13109) is a far cry from the OEM piece. Aeromotive says that the A1000 regulator has logged more miles than any other performance regulator, and for good reason. It offers base-pressure adjustability from 40 to 75 psi and has a 1:1 rising ratio with boost. It comes with a 1/8-inch NPT gauge port and features two ORB-06 inlet ports and a single ORB-06 return port. The kit also includes a liquid-filled 0-100psi fuel pressure gauge for the 1/8-inch NPT port.
Fittings and Hose
The kit comes with all of the ORB and AN fittings in the -06 and -08 sizes you’ll need to complete the installation in the stock configuration. The fittings are industry standard construction, with a finish on the nicer side of the spectrum. The included 8 feet of -6 and 6 feet of -8 A1000 braided stainless hose leaves you with enough for a little oops here or there, but as in all aspects of life, measure twice and cut once.
As mentioned at the beginning of the section, the kit also includes fittings specific to the OEM fuel connections, allowing for a direct plug-and-play installation if you were installing this kit directly into a vehicle. Of course, we have to be difficult, and in order to make easy connections to the dyno, we modified the arrangement of the kit. This proved to be nothing difficult thanks to the kit’s flexibility, and while our final feed line looks a little goofy, it will make life easy on the dyno, as we take the engine on and off between dyno sessions.
One thing noted in the instructions is that you might potentially need an intake spacer to clear the slightly taller fuel rail. We were in exactly that boat, but the interference was easily rectified with a 3/8-inch-thick phenolic spacer purchased from eBay. Fortunately for us, the seller had them in both E7 and GT40 styles, so we ordered one of each for the future intake testing we’ll be doing. For the Holley SysteMax, instead of a phenolic spacer, we opted for an NOS spray bar spacer… because why not?
With that, we are one step closer to the initial dyno of Retro 5.0, along with a bunch of baseline testing. All that’s left is to replace all of the OEM sensors and “wire up” the Holley Terminator X and we’re ready to make some noise.