Episode 6: Fuel Injectors Explained — How to Choose the Right Size (And Avoid Costly Mistakes)
About this episode
Fuel Throttle Podcast breaks down how to choose the right motorcycle fuel injector size without common tuning mistakes. The hosts focus on ECU log interpretation (pulse width and duty cycle), explain why “don’t go too big” matters for idle, light-load drivability, and on/off throttle control, and give practical rules of thumb for Harley applications. They also cover minimum pulse-width nonlinearity, the role of fuel pressure and spray pattern, how to verify injector behavior in logs/dyno pulls, and why cheap eBay/Amazon injectors often fail.
Fuel injectors are one of the most misunderstood—and most important—components in your Harley’s performance. In Episode 6, Jamie and Lucas break down how to properly choose the right injector for your build using real-world data, not internet myths.
They cover OEM injector sizing across Twin Cam and Milwaukee-Eight platforms, how to read ECU data like duty cycle and pulse width, and why bigger injectors don’t mean more power. You’ll also learn the often-overlooked factor that can make or break drivability: minimum pulse width and low-speed control.
Whether you’re building a mild cam setup or a high-horsepower engine, this episode gives you the knowledge to avoid common mistakes, improve tuning accuracy, and get the most out of your combination.
In this episode:
- Why injector size should be based on your engine—not guesswork
- How to log and interpret duty cycle and pulse width
- The truth about the “80% rule” (and what actually works for Harleys)
- Why oversized injectors hurt low-speed performance
- Real-world guidelines for Twin Cam and M8 injector sizing
- The importance of spray pattern, fuel pressure, and injector quality
If you’ve ever wondered whether you actually need bigger injectors—or how to choose the right ones—this episode will save you time, money, and frustration.
Alpine A110
"All those cable bikes have four inches. So you would see duty cycles in the 90s in cams and a 110 twin cam, like the 07 to 10 CVOs baggers, they would peg the duty cycle right to 100. So they needed bigger injectors, but even the screaming eagle kits and such didn't use bigger injectors."
Lancia Lambda
"...cent more fuel mass to achieve the same commanded lambda. So that's something to appreciate and understand..."
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