When asked about the key to modern performance, many enthusiasts point to the turbocharger as the harbinger of horsepower. Alfred Buchi invented the turbo with the patent description of “an axial compressor, radial piston engine and axial turbine on a common shaft” in 1905, many years before the technology to make it operate existed.

In fact, electronic fuel injection is the key to modern performance. The move from carburetors and subsequent advancements in the injectors and the computers that drive them paved the way for mainstream turbocharging. The Buick Grand National of 1986 – ’87 can be looked at as a tipping point where the efficiency of fuel injection and an ECU that could be accessed and altered (chipped) opened the door to quick, effective power gains. The 1990’s saw evolution on both the injector design and engine management fronts. In the 21st century the power output and fuel efficiency of performance engines rose as emissions were reduced.

More recently, the advent of gasoline direct injection is probably the biggest change in automotive fuel injection. From the fuel system side, the main difference is fuel pressure, which is many times higher in the Gasoline Direct Injection (GDI) systems at around 2,000 psi versus 43 to 60 psi in conventional injection. On the tuning side, GDI cars are so new that there is limited aftermarket potential. Jens von Holten, owner of Fuel Injector Clinic, says that while this is changing rapidly, direct injection systems are typically built at almost full capacity for the stock horsepower, meaning that many components would need to be replaced at the same time to significantly bump power. He also reports seeing fuel pump delivery shortfalls long before the stock injectors are maxed out.




So the leaps and gains in aftermarket fuel injection are still in port injection where injector flow rates are at record highs, engine management has gone 3D, and the emergence of E85 ethanol setups is opening the door to ungodly boost.

The Emergence Of High-Flow, High-Impedance Injectors

As recently as 2005, high-impedance injectors over 1,000cc/min were a rarity and most didn’t work all that well on the street. Today, von Holten says 1,100cc/min and much larger can be run in street performance cars that are daily-driven. The stumbling block has always been the ability of these four-digit injectors to accurately dispense the small amounts of fuel needed at idle or cruise.

This is no longer the case. When it comes to modifying an injector for higher flow, von Holten says it’s all about the starting point. And for Fuel Injector Clinic that starting point is the Bosch EV14. “The tighter tolerances in manufacturing and significantly lighter moving internals,” says von Holten, “has allowed aftermarket injector companies like Fuel Injector Clinic to modify and then rematch these injectors to much tighter flow tolerances than the Bosch factory. When it comes to lighter moving internals, we have measured the combined spring and valve weight on older generation injectors at 5.1 grams and on typical EV14 injectors those parts are 1.65 grams.”

The beauty of this is with their lighter weight the valves can be made to fire fast enough to idle and cruise while the injector retains its very high overall flow rate. We’re talking about very minute amounts of fuel in the order of .002 cc per pulse at idle. To put this into perspective, von Holten says it would take 2,000 such pulses to fill a teaspoon.




Von Holten believes that the most important part of large injectors is the proper matching. “Our Data Match Technology,” continues von Holten, “ensures equal fueling for each cylinder and that the data supplied with your set of injectors will guarantee the ECU can control them accurately. Then the tuner can do his job to the fullest.”

See the impressive Fuel Injector Clinic Data Match Technology in action. Click the picture above and check out the video.

“Short pulsewidth fuel mass that’s consistent enough to idle a street car running 2,150cc/min injectors and a stock ECU hasn’t been around for very long. It’s tip of the spear stuff. Even with the matching, if you pick our largest injector (2,150cc/min) and try to run that injector on pump gas you might have to idle it at 13.0 AFR instead of the preferred 14.7 to get a stable idle. We provide short pulsewidth data for the newest ECU’s, which are now accepting compensation data for the non-linear zone of the largest injectors to help idle and cruise. But this remains an area of significant challenges.”

In short, too big still exists.

Working The Engine Management Side Of The Equation

“Of course this evolution is about more than the fuel injector,” says von Holten. “As OE engine tuning strategies have become more and more complex because of newer processors and other electronic aids, the fuel maps evolved into 3D modeling and ever more complex sub-maps for special conditions like cold start, tip-in throttle enrichment, and compensating for accessory draws like air conditioning and other heavy electrical loads. This part of the fueling evolution has put a very high emphasis on the data that needs to be collected about each injector type and flow size that we sell. In order to test the injectors, our company invested in custom flow bench equipment that had to be designed from scratch because no one sold equipment sensitive enough to provide the huge amount of data we wanted quickly enough.”

Fuel Injector Clinic Flow Testing Machine.

“Collecting the data was just half of the battle. We then had to partner with re-flash software companies and aftermarket ECU manufacturers to reverse-engineer the fuel strategy and the layout of the tables for each brand of car or ECU that we intended to provide the data for. The amount of man-hours dedicated to this is staggering. The end result however are injectors and systems that work together as intended, seamlessly, and this enables tuners to at least closely mimic OE levels of drivability.”

Popular Injector Options For Popular Imports

When it comes to electronic fuel injection, imports have embraced the technology. There are two reasons for this. First they have no carburetor legacy to hold them back. Secondly, import owners are traditionally younger and more willing to ride the wave of the latest technology.

Fuel Injector Clinic 1,100cc High-Z injectors.

“Our 1,100cc/min injectors,” says von Holten,” are a very popular solution for many modified Subarus, Evos, GT-Rs, and Supras because they just happen to support a common horsepower range for these vehicles on both gasoline and E85.”

“To get an idea of which injector will be the best solution for a customer, we typically ask them what their power goals are, what type of fuel they will be using, and what base fuel pressure they will be running. Each of these things has an effect on fuel requirements. We also like to get an idea on how the vehicle is used; as a daily driver, dedicated race car, or a combination of the two. We offer injectors for any top-feed port injector application out there and have supplied injectors for applications ranging from a 150 horsepower daily driver to a 3,000 horsepower speed boat.”

The Fuel Injector Clinic also has a rolling laboratory. Its wicked drag Civic conducts tests a quarter mile at a time. The Honda is impressive, with a personal best run of 8.61 at 180 mph. It is motivated by a Honda B18 GSR race-fortified engine punched out from 1.8 to 2.0-liters. Boost is set at 48 psi and eight Fuel Injector Clinic 1,650cc High-Z injectors fuel the fire. Top end output is approximately 1,200 wheel horsepower.

E85: Big Digit Power Production Vs. Real World Accessibility

Ethanol or E85 is a perplexing path to ponder. Its ability to burn cool and allow outlandish boost levels opens the door to huge power. But it takes a much greater volume of fuel to make the magic happen, so you’ll most likely need a bigger fuel tank whether you run on the track or use the car in question as a daily driver. Additionally, the availability of E85 can be a tough find. While station density has improved, availability can still be a deal-breaker for many. Clear these two hurdles and then you can zero in on making power.

This can be too much of a good thing type scenario. “With the way the performance world is going,” relates von Holten, “it’s possible to run out of injector even using our largest E85 injectors, like the FIC 1,650cc/min or the FIC 2,150cc/min. It’s not uncommon any more for a four cylinder to need eight injectors to make the power demanded. Since E85 uses about 27 percent more fuel by volume to generate the same horsepower, it’s easy to run out of injector. Fortunately, there are a variety of standalone ECUs that can control two sets of injectors to meet the demands of those looking to make extremely high horsepower…for the street, E85 is still the ‘poor man’s race gas!’”




E85 requires more maintenance than normal pump gas since it is hygroscopic and therefore absorbs water, which leads to corrosion and clogging filters. So you need to keep an eye on the entire fuel system. Von Holten says a black gooey buildup on the injector tip caused by the different electronic charges in the E85 particles is another issue that requires maintenance. Over time these deposits can have an effect on the spray pattern of the injector. He’s quick to point out that running a tank of gasoline every once in a while will eradicate the buildup.

Variation in ethanol content is also an ongoing concern. While the pump may say ‘E85’, the mix percentage varies significantly due to seasonal considerations, which can be a real issue for racers who “tune” for a set fuel mix. This is why many high end race cars either mix their own E85 or buy race E85 that is much more exact in its ratio. If you want to fill up at the pump, von Holten recommends installing a system that uses a flex-fuel sensor.

Finding the correct filter for E85 applications can be a challenge. There are not that many filters out there that are compatible with E85 and are also able to filter out small enough particles to keep the injectors clean. Von Holten mentions that a product like Fuelab’s 6 micron fiberglass element filter meets both of these requirements.

Whether fueling with pump gas, race fuel, or E85, size matters, and thanks to recent innovations in fuel injector technology and the savvy of aftermarket injector gurus, enthusiasts can generate stratospheric levels of power and still retain truly streetable idling, off-throttle performance, and light-load cruising. It’s a Best of Both Worlds time in performance tuning…let’s make the most of it.