What size injectors do I need for 500 hp?

One of the most common questions in performance builds is: what size fuel injectors do I need for 500 horsepower? Choosing the correct injector size is critical for making reliable power, maintaining drivability, and protecting your engine from lean conditions.

The good news is that 500 HP is a very achievable goal with the right injector setup—if you size it correctly.

Why Injector Size Matters at 500 HP

At 500 horsepower, your engine requires significantly more fuel than stock injectors can provide. Undersized injectors can lead to:

• Lean air-fuel ratios

• Detonation and overheating

• Power loss at high RPM

• Engine damage

Properly sized injectors ensure your engine receives enough fuel under load while keeping injector duty cycle within a safe range.

The Basics of Injector Sizing

Injector size is typically measured in lb/hr or cc/min. The required size depends on:

• Horsepower goal

• Fuel type (gasoline vs E85)

• Number of cylinders

• Desired injector duty cycle (usually 80–85%)

As a rule, you always want some headroom—running injectors at 100% duty cycle is unsafe.

Injector Size for 500 HP on Gasoline

For most gasoline engines making around 500 HP:

• Recommended size: 50–60 lb/hr injectors

• Common choice: 60 lb/hr (650cc) injectors

60 lb injectors are extremely popular because they:

• Support 500 HP comfortably

• Maintain good drivability

• Leave room for future upgrades

This size works especially well for street builds, mild boost, and LS engines.

Injector Size for 500 HP on E85

E85 requires roughly 30% more fuel than gasoline.

For 500 HP on E85, you’ll typically need:

• Minimum: 70 lb/hr injectors

• Recommended: 80 lb/hr injectors

Choosing 80 lb injectors provides safer duty cycles and more tuning flexibility.

Why Many Builders Choose 60 lb Injectors for 500 HP

Even though smaller injectors can support 500 HP, 60 lb injectors are often the smartest choice because they:

• Run at lower duty cycles

• Improve reliability

• Are easier to tune

• Work well for future power increases

Modern 60 lb injectors offer excellent low-pulse control, meaning you don’t sacrifice idle quality when tuned correctly.

Do You Need a Tune After Installing Injectors?

Yes — always.

Upgrading injectors changes how much fuel enters the engine per pulse. A proper tune recalibrates the ECU for:

• Injector flow rate

• Injector latency

• Idle and part-throttle fueling

Without tuning, even correctly sized injectors can cause drivability issues.

Final Answer: What Size Injectors Do I Need for 500 HP?

Gasoline:
• 60 lb/hr (650cc) injectors — ideal choice

E85:
• 80 lb/hr injectors — recommended

This setup delivers reliable fueling, strong performance, and engine safety with room to grow.