What size injectors do I need for my LS?
Quick answer (Speedway Motors chart, 43.5 psi base pressure, 85% max duty, deliberately conservative):
| Crank hp | NA gas | NA E85 | Supercharged gas | Supercharged E85 | Turbo gas | Turbo E85 |
|---|---|---|---|---|---|---|
| 400 | 40 lb/hr | 50 | 47 | 56 | 52 | 62 |
| 600 | 63 | 75 | 71 | 85 | 78 | 94 |
| 800 | 84 | 100 | 95 | 113 | 104 | 125 |
| 1,000 | 104 | 125 | 118 | 140 | 130 | 156 |
Do the math yourself: injector lb/hr = (crank hp × BSFC) ÷ 8 cylinders ÷ 0.80 duty. Conservative BSFC values from LSX Magazine: gasoline 0.55, E85 0.80, methanol 1.20. Size for gross power (include supercharger drive losses) and round up to the next available size.
Fitment matters too: LS injectors come in several heights and three connector styles (USCAR, Mini Delphi/Multec 2, Jetronic). Spacers ("top hats") and O-rings adapt taller or shorter injectors. OEM LS injectors are high-impedance (~12 Ω), which OEM ECUs require. Any injector change needs a tune.