Precise Injector Matching Tames Powerful Street Cars

If you are into modern performance cars, you just don’t know how good you have it compared to owners of older fuel-injected vehicles, who were forced to completely trade drivability for performance. Thanks to advanced factory and aftermarket engine management systems, it’s become commonplace to turn up the performance and restore the drivability with a custom calibration.

Sure, you might have to put up with a bit more exhaust noise or a minor idle stumble because there is a limit to a huge injector’s ability to release small amounts of fuel. And small amounts of fuel are what you need for a smooth idle. Tuned at its best, though, the car will drive much like it did when it was new.

Fuel Injector Clinic offers matched injector sets from 42 to 200 lb/hr hour flow rates. The company’s unique, short-pulse-width matching really shines on injectors that flow more than 100 lb/hr.

That’s why we traveled to Fuel Injector Clinic in Hobe Sound, Florida, to learn more about the company’s unique Data Match Technology, which now includes short-pulse-width fuel injector matching. In fact, Fuel Injector Clinic’s Data Match Technology is used by Holley and the NHRA on all of the injectors that are used in the Pro Stock class.

Smooth Cruising

“People want a 1,500-horsepower car that they can run around in with their wife and kids and the A/C running,” Tim Jilg, general manager of Fuel Injector Clinic, deadpanned.

People want a 1,500-horsepower car that they can run around in… — Tim Jilg, Fuel Injector Clinic

And, when you start pushing toward four-digit power numbers, that means delivering a lot of fuel. That’s the kind of fuel that only race cars used to need, but it’s becoming more common every day as enthusiasts push the envelope and blur the line between street cars and race cars.

Delivering fuel at a higher rpm is not such a big deal. Delivering and keeping that fuel under control at idle and part throttle or cruising, where most street driving takes place, is the challenge when tuning these high-horsepower daily drivers. While calibration is crucial here, the fuel injectors are often an overlooked piece of the puzzle.

When you order a set of injectors for a specific vehicle they arrive packaged in a high quality box with the wiring and adapters needed for drop-in installation into your vehicle. The company also offers highly detailed custom flow rate and dead time information specifically for your set, and the data that tuners need to quickly incorporate the new injectors into your combination. These injectors also carry a limited lifetime warranty, which provides the kind of peace of mind you don’t often see on high-performance gear.

“The key is delivering the accuracy needed — meaning smaller amounts of fuel — for idle and cruise on your street beast from its big old injectors,” Tim added. “These big injectors want to vomit fuel, which is great for track racing, but all you need for cruising is little accurate spits.”

The Part-Throttle Challenge

“Typically speaking, on most small or OE injectors, you are always running in the linear phase of injector operation, meaning that the injector valve opens fully during each pulse. That’s easy to tune,” Jens von Holten, owner of Fuel Injector Clinic, said. “With the big injectors that the ‘street beasts’ use these days, we are no longer opening the valve fully at idle and cruise. But this is what we do in the performance world, right? We move outside the original design parameters and make the parts work. Same with a big fuel injector; we are forced to see how we can make the engine run smoothly while the injector valve is only partially opening.”

Rather than simply flowing the injectors wide open, Fuel Injector Clinic tests its injectors at multiple data points to look at how the injectors flows across the full pulse width range as well as how quickly the injectors open in order to find the most precisely matched sets of injectors for high-performance applications.

So when you start moving into the 100-plus-lb/hr injectors needed to feed those four-digit street beasts, the window of injector operation — or pulse width — at idle gets pretty narrow, making it very difficult to control misfire at idle and cruise.

Wanting to correct this injustice, Fuel Injector Clinic developed Data Match Technology, which it says is the most complete flow matching and latency value information available in the aftermarket performance industry. To describe the laborious and technical DMT operations, we first need a bit of technical background.

Delta Flow

The time that the computer has to add for the injector’s valve to fully open minus the time at the end of the pulse that it takes to fully close is called latency or dead time. It is the delta, or difference, of those two actions on either end that has to be added to every pulse so that the flow amount from the injector is correct. The typical delta time to add is roughly one millisecond. (To put that into perspective, the blink of an eye is around 300 to 400 milliseconds.)

In order to precisely match injectors across their full pulse width, Fuel Injector Clinic had to create its own test stand, which maintains precise electrical and temperature parameters to ensure consistent, accurate results. “We developed these flow benches and their precise technology using expert software engineers. This expertise enables us to take the flow meter’s measurements and the injector driver outputs and display the results graphically, which is unique to the FIC test bench,” Jens said.

And if the flow isn’t right, the engine doesn’t run right.

“Keep that 1-millisecond latency value in mind when you consider the .5-millisecond effective idle pulse width of our 200 lb/hr injector — which is our most common ‘big street’ injector,” Jens said. “At half a millisecond, you now get an idea of the scale of how accurately you need to work. These operating conditions are our daily challenges and are why we developed Data Match Technology.”

Three-Zone Matching

Of course you want each injector to flow the same amount. Dynamic matching is the first stage of the Data Match Technology process requires pulsing the injector at multiple points through the entire linear operating range and matches the injectors that flow within 1 percent of each other. Fuel Injector Clinic provides precise data on a sheet with each serialized injector set.

Next, Fuel Injector Clinic makes sure the injectors have precisely matched latency values. The second of Data Match Technology is ensuring latency values of injectors in a set are within 2 percent of one another.

Essentially, the Fuel Injector Clinic team flows thousands of injectors and, using the data from that testing, selects sets of injectors with precisely similar performance behaviors. The company doesn’t just consider wide-open flow, they go into much greater detail, examining how the injectors flow across the full pulse width as well as how quickly the injectors open.

Why is this important?

Remember, the injector may only need about half a millisecond to provide the correct amount of fuel needed at idle. In OE the latency time within a set can vary by as much 40 percent. Let’s say your average latency time is 1 millisecond and latency varies by as much as 40 percent.

If one injector in the set is almost half a millisecond slower to react, then one injector is giving you zero fuel and another is giving you a full pulse width. Suddenly, you have a misfire at idle. Fuel Injector Clinic’s precise latency matching is said to deliver synchronized pulsing, which equates to a smoother idle.

We want our injectors to give the tuner a better result. — Jens von Holten, Fuel Injector Clinic

As mentioned earlier, at idle and cruise large injectors are forced to operate with the valve only partially open. This is a far more inconsistent operating area than the linear zone found at high RPM. So Fuel Injector Clinic, as a third step, tests injectors at multiple, short pulse widths to determine two crucial criteria: when the injector first starts to open and when the valve finally hits its limit stop. Via engine and bench testing, Fuel Injector Clinic selects injectors with more consistent fuel flow, which should deliver a smoother-running engine.

Testing short-pulse rates is time consuming. It may take as many as 1,500 pulses to get a measurable amount of fuel even on Fuel Injector Clinic’s sensitive flow meters.

“We want our injectors to give the tuner a better result, saving the customer money through shorter tuning time and making a happy enthusiast for the tuner when that customer walks out the door with a car that runs right in all conditions,” Jens said. “If your injector company doesn’t provide you with these steps completed for every set of injectors, maybe you should try a set of FICs.”

For even more precise matching, the company created this research and development bench, which tests injectors one at a time to even more exacting standards. By using this bench, Fuel Injector Clinic is able to provide sets of injectors that perform the same in the critical range when cars are at idle or part throttle, which can significantly improve drivability on high-horsepower street machines.

The company specializes in providing matched sets of fuel injectors that all have precisely similar characteristics, which is crucial for predictable performance at idle and part throttle, allowing even a heavily modified vehicle to perform more like a car that was just driven off the dealer’s lot.

In addition, the rise of high-ethanol fuels like E85 for street performance machines has enabled high levels of performance thanks to its affordable octane. However, E85, with its longer pulse widths, might mask short pulse issues that can pop up on gasoline if you are flexing back and forth between E85 and straight pump gas.

“A lot of times with ethanol you can run injectors and never have a problem. Then you have guys say, ‘Well, it ran great on E85, but I put it on 93-octane and now the car doesn’t run right, ’” Tim said.

Equal Billing

For FIC, the foundation of minimizing these drivability and performance problems is ensuring that each injector offers similar actuation and flow characteristics.

“It starts with the flow matching. A lot of companies will do what’s called a ‘static flow test,’” Tim said. “They just hold the injector open for 20 seconds, a minute, or however long and tell you how much it flows in that amount of time and claim they are selling you flow matched injectors.”

This is how tightly Fuel Injector Clinic matches its injector sets. While a matter of milliseconds might not seem like much, it can mean the difference between misfires and poor idle and smooth-running, predictable performance on a high-horsepower car with large fuel injectors.

Pro Stock Balance

While our focus here has been the street performance application of Fuel Injector Clinic’s injectors, the company is also a supplier at the highest levels of racing, including NHRA Pro Stock racing, where FIC used its precise Data Match Technology to flow match the Holley injectors used in the Pro Stock fuel-injection systems.

“Holley’s standard injector offerings for street vehicles are consumer-grade pieces, which have been proven to work well in many applications. In Pro Stock, however, the decision was made to use an injector that could be inspected easily for modifications. For that reason they do not have any type of diffuser at the tip,” Robin Lawrence, Director of EFI Business Development at Holley Performance Products, said. “We knew that the Pro Stock Teams would tune each cylinder for fuel and timing per gear with the Holley EFI. We believed that a flowed injector from Fuel Injector Clinic would offer the tolerances required to hit their tuning targets on a consistent basis.”

Having worked with Fuel Injector Clinic on other projects, the Holley team knew FIC could provide matched units that would get the job done.

“The first consideration was that we use a quality built injector with quality parts,” Robin added. “The injector is built by Bosch with components specified by ASNU. It is not a Bosch Motorsport Injector. Because it doesn’t have a diffuser it can be visually inspected for any modifications.”

While static flow will let you know how much power the injectors can support, it’s not the best indicator of how well matched the injectors are in all other areas of their operation, including idle and part-throttle RPM. To find that out, Fuel Injector Clinic created its own fuel injector testing equipment that keeps all the particulars under tight control to ensure its flow data is as accurate as possible. As far as they know, there are only two companies in the world that can flow and characterize injectors at this advanced level.

“For accuracy, the voltage on the Fuel Injector Clinic flow bench is held within .1 volt. The temperature has to be within .3 of a degree. And the pressure has to be within .1 of a psi. The voltage and pressure are precisely set and the data are stored for every test run,” Jens said of the FIC test stand’s operation.

For the short-pulse-width research and to create the myriad of data needed for the OE injector characterization that Fuel Injector Clinic provides, the company also created another injector flow bench that tests one injector at a time. It does so with even more exacting tolerances.

“We have a secondary bench that’s called our R&D bench, where we control things even tighter than the production flow bench,” Jens said. “There, we actually watch the whole profile of the pressure drop to see how much it influences the flow rates.”

Not only are the FIC injector sets precisely matched, but the company provides the data that tuners need to plug into EFI software to calibrate for the exact set of injectors you are running. This means less work for the tuner and a greater chance that your car will run the way you want it to.

Collecting the OE tables data is a time-consuming process, which can take as many as 20 hours per injector type, but this bench allows Fuel Injector Clinic to precisely document each injector’s characteristics so they can provide this “ease of use” tool to tuners everywhere. This OE-level data makes the tuning process much easier and more predictable. Rather than chasing the calibration because of those variances, the tuner can instead eliminate one tricky variable and work on other facets of the calibration.

“It’s a fact that tuners can be under a lot of pressure. When they are tuning a vehicle that isn’t put together well it can be a real challenge to tune. One of these potential issues is a poorly matched set of injectors, or injectors that don’t include proper tuning data. When the tuner struggles to produce great tuning results, it could fall on the their lap. Their expertise may be questioned because of something they have no control over,” Jens said. “We are taking that variable out of the equation. We are saying — here’s a set of injectors you can count on being reliable and consistent, and every time you put your tune in, your tune is going to be repeatable.”

Street Power

While the concept of these injectors sounds pretty impressive, you might wonder how they work in a real-world street car. The team at MAK Performance in Hialeah, Florida, has experience with Fuel Injector Clinic’s injector technology and has seen positive results.

“Our reputation for the longest time has been that we are not ones to follow the cookie-cutter mentality when putting together combinations. We are the pros; we should be the ones trying new stuff out! We did it once already with the S550 platform and Fuel Injector Clinic low-pulse width matched injectors, and on our first go around we made 700-plus rear-wheel horsepower on 10 psi…” Willy Diaz, owner of MAK Performance, said.

Building high-powered street Mustangs is something that MAK does on the regular and trying something new to get the desired result is not something its crew shies away from.

“For the longest time there has really only been one option in the high-end injector market on the street-car side of things. When it came time to turn up the power once again with our new setup we needed to up the injector size once more and this time make sure we wouldn’t have to do it again,” Adrian Gomez, manager at MAK Performance, said. “That’s when Fuel Injector Clinic came in. We had been talking for a while, they are local to us, and the right situation arose, so we all agreed on their FIC1650s with their short-term matching, as our car is driven daily, and we wanted the best possible drivability we could manage. They claimed it, and we were going to put it to the test.”

MAK simply wanted predictable fueling that was easy to tune, as taking one variable out of the equation simplifies the process.

“Flow matching and data makes it so that what we pull out of the box and put into the car works as intended from the start. These types of injectors cost more than your bulk-packaged stuff, but the performance difference out of the box is unimaginable. The problem with bulk-packaged stuff is that you may get a set of eight injectors that may flow drastically different from one cylinder to the next,” Willy explained. “That is basically impossible to tune correctly. For many years that was all we had in the street car world and everyone made it work. As technology evolves, so must we, and that brings us to today’s age of flow-matched injectors with viable tuning data. Life on the tuning front has become easier, and that’s a welcome change when the OEMs have made things exponentially more difficult everywhere else.”

MAK ordered a set of new, flow-matched injectors from FIC for its S550 project car, which is also slated for an automatic transmission swap, and the upgrade was seamless.

“We were able to take 1,650cc injectors, drop them in the car, fire it up and almost immediately have a car that was well-mannered,” Adrian added.” The power end of the job is easy, getting a big injector like this to idle and drive like a stock, 47lb/hr injector was unheard of years back. FIC matching was a great perk to have on this front.”

Big power and great drivability is definitely a perk we can get excited about.

Of course, just because FIC can help you run huge injectors, doesn’t mean you should run them if you don’t really need them. Instead you should consult the FIC team and your tuner to strike the right balance between power capability and drivability. You can also use Fuel Injector Clinic’s horsepower calculator to help you determine what size injectors you might need.

“Can we help you run in the big injector area? Yes, and if you do its imperative that you select a company like FIC that offers the most advanced injector characterization and matching on the market. But you shouldn’t necessarily run these larger size injectors if you don’t need to do so to reach your power goals,” Tim said. “If your goal is to make 1,700 horsepower, you don’t have a choice, you are going to have to run larger injectors. FIC has the best technology that is currently available and you will notice a huge difference with our short-pulse-width matched injector sets over the standard flow-matched injectors that our competitors offer.”

If the idea of a better running, easier-to-tune combination sounds intriguing, you can learn more about the company’s matched fuel injectors right here.

Article Sources

About the author

Steve Turner

Steve Turner brings decades of passion and knowledge in the world of Ford performance, having covered it for over 20 years. From the swan song of the Fox Mustang to the birth of the Coyote, Steve had a front-row seat.
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