What size injectors do I need for E85?
Size for power × E85 fuel consumption, with duty-cycle headroom.
- LSX Magazine's sizing formula: minimum injector flow per cylinder = (target power × BSFC ÷ number of cylinders) ÷ 0.80. For E85 they use a BSFC of about 0.80 lb/hp-hr, versus 0.55 for gasoline.
- Example (our arithmetic with their formula): 500 hp on E85 → 500 × 0.80 ÷ 8 ÷ 0.80 ≈ 62.5 lb/hr per injector. The same engine on gasoline works out to about 43 lb/hr.
- Duty-cycle ceiling — sources differ: LSX Magazine treats 80% as the industry-standard maximum for continuous use; Performance Racing Industry says to keep E85 injectors at or below 90%. The formula above uses 80%.
- Fuel pressure: injector ratings are at a stated pressure (commonly 43.5 or 58 psi), so check the flow at the pressure you'll actually run.
- Pump: keep 10–20% headroom (Performance Racing Industry).
See fuel, E85 & boost.
Confidence: medium — sources disagree or are limited; check the sources below.
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Sources
- Fuel For Thought: Sizing Port Fuel Injectors for High-Performance Engines — LSX Magazine
- PRI Education: Converting From Pump Gas to E85 — Performance Racing Industry