The BSFC chart thread (post 'em if you got 'em) is a good start
Formula for efficiency from BSFC is Efficiency = 79.3/BSFC (based on petrol energy density of 46.5 mj/kg.)
| g/kwh | Efficiency |
| 200 | 39.6% |
| 210 | 37.8% |
| 220 | 36.0% |
| 230 | 34.5% |
| 240 | 33.0% |
| 250 | 31.7% |
| 260 | 30.5% |
| 270 | 29.4% |
| 280 | 28.3% |
| 290 | 27.3% |
| 300 | 26.4% |
| 310 | 25.6% |
| 320 | 24.8% |
| 330 | 24.0% |
| 340 | 23.3% |
| 350 | 22.7% |
| 360 | 22.0% |
| 370 | 21.4% |
| 380 | 20.9% |
| 390 | 20.3% |
| 400 | 19.8% |
| 410 | 19.3% |
| 420 | 18.9% |
| 430 | 18.4% |
| 440 | 18.0% |
| 450 | 17.6% |
| 460 | 17.2% |
| 470 | 16.9% |
| 480 | 16.5% |
| 490 | 16.2% |
| 500 | 15.9% |