Just as important as choosing the right fuel pump is selecting the proper fuel injector, and this is where Fuel Injector Clinic comes in. For our application we went with the firm’s big-boy BlueMax injectors rated at 2150 cc/min (205 lb/hr), which provide 4 times the stock flow rate of a stock Supra Turbo’s injectors!
If you’ve been living in the performance cave of the 80s and 90s, you might still be thinking that low-impedance (“low-z”) peak-and-hold injectors are the way to go with high horsepower applications. Because low-z injectors did previously generate a faster response and less operation heat when compared to high-z’s, they were widely used in high horsepower applications. In fact, pretty much any injector greater than 500 cc/min was low-z back then.
Low-z injectors work well, but their “peak-and-hold” characteristic means they use a high initial current to open the injector and then a low secondary current signal to keep it open until the end of the pulse, and then close quickly.
While this two-step signal made it popular to use low-z injectors in high horsepower applications, it didn’t provide the smoothness and drivability of a high-z injector, which uses a “saturated” single signal to both open and maintain the injector open. The result is a better response time and low pulse width predictability.
Fuel Injector Clinic still sells low-z injectors, but FIC reports their new high-z units outperform the low-z’s significantly. With the new technology available to FIC today, they’ve been able to create new designs with tighter manufacturing clearances, yielding much lighter moving parts.
For instance, a valve and spring assembly now only weighs a third of what they do in a low-z. This helps create a more linear flow throughout a high-z’s pulse range. Plus, the high-z injector is able to consistently create shorter pulse widths, which is great for part-throttle response and engine idling, while still being able to operate at higher maximum operating pressures (talk about having your cake and eating it too!).
Having just removed a set of low-z 1000 cc/min injectors from the Supra, it will be interesting to see just how much smoother the drivability will be. While a fun car until now, the drivability was more visceral, and not quite up to the full-range operating smoothness when compared to any factory vehicle. The improved characteristics of these high-z injectors, coupled with the capabilities of the new engine management system that is getting installed to the car as we speak (light shed on Page 8), is enough to give us a stupid-wide grin from the anticipation.
Each BlueMax FIC 2150 cc/min high-z injector has a 1-year warranty against defects and comes with an individual serial number and flow rate from FIC. The company also sells 1100, 900, 775, 650, and 525 cc/min high-z injectors, along with 750-1650 cc/min low-z units for the Supra.
Here’s a look at an FIC 2150 cc/min injector tip.
The reasoning behind our choice to go with 2150 cc/min when 1100cc injectors would suffice, given our 800whp power goal, was to leave room on the table for more in the future, in case we were to go for more power. Since we wouldn’t be sacrificing any significant drivability going with the biggest units, there really wasn’t any reason not to get the 2150’s, outside the additional cost. Using FIC’s seemingly conservative calculator, we’re good for over 1000whp on E85 with our setup, at a 43.5 PSI fuel pressure and 80% injector duty cycle.
With 1100 cc/min injectors, that number diminishes to 548whp on E85 (700+whp on gasoline). However, FIC reports one of its Supra customers, using 65 PSI of fuel pressure, was able to squeak 893whp on E85 out of the 1100’s with the same Precision 6766 turbo this car is using. While FIC does not recommend using such high injector duty cycle (which was at 98%, and the tuner did dial it back for the road), it just gives a real world example of where the limits are with the 1100 cc/min injectors on E85.
Each FIC injector includes a connector that needs to be wired in, which Modified by KC did for us here.