Normalization calculations Thursday, September 24, 2020

1/4 Mile Data Normalization
Drag strip numbers depend on atmospheric conditions. In order to be able to compare numbers from one outing to the next it is necessary to normalize the ET and MPH to standard conditions. Here are the equations to compensate for temperature and barometric.

Weather Normalization
ETstd = ETraw * Cet
Cet = 0.9986 + 0.0095 * (Baro-29.1) - 0.0002556 * (Temp-35.0)
MPHstd = MPHraw * Cmph
Cmph = 1.0003525 - 0.00975 * (Baro-29.1) + 0.0002667 * (Temp-35.0)
ETstd is normalized ET, ETraw is ET from time slip, Cet is the ET normalization factor, MPHstd is normalized MPH, MPHraw is MPH from time slip, Cmph is the MPH normalization factor, Temp and Baro are temperature and barometric at run time.
Though Relative Humidity is not included here, these numbers are better than raw data.

Altitude Normalization
BHPloss = (Elevation * 0.03) * BHPsealevel / 1000, or 3%HP loss per 1,000' elevation.
BHPloss = Brake HP measured at elevation,
Elevation = elevation above sea level in feet,
BHPsealevel = Break HP measured at sea level
HP calculation from 1/4 Mi Data
Crank HP can be calculated from 1/4 mile trap speed and vehicle weight.
CHP = (MPH / 234)^3 * Weight
ET = 1357 / MPH

Injector Sizing & Fuel Pressure
TPI fuel injectors are rated in lb/hr of steady fuel flow at 43.5psi. In an L98 engine the maximum injector duty cycle is 80%. Required injector size can be estimated from Brake HP (BHP). Assume a Brake Specific Fuel Consumption (BSFC) value of 0.50 for a TPI (the range
is 0.45 to 0.50 for normally aspirated engines). Then injector size (Flow Rate) is given by:
Flow Rate = (BHP * BSFC) / (8 * 0.8)
Maximum fuel flow capacity can be adjusted with fuel pressure as follows:
FuelFlow2 = FuelFlow1 * SQRT(Pressure2 / Pressure1).

Table A shows full capacity fuel flow at various fuel pressure values. The corresponding BHP values assume BSFC=0.50 (for TPI intake) and 80% fuel injector duty cycle.

Table A - Fuel Flow / BHP vs Fuel Pressure

 Flow@43.5psi 40 psi 45 psi 48 psi 50 psi 55 psi 60 psi Comments 19 lb/hr 18.1 / 232 19.2 / 246 19.8 / 254 20.3 / 259 21.2 / 272 22.2 / 284 stock LB9 22 lb/hr 21.0 / 268 22.2 / 285 23.0 / 294 23.5 / 300 24.6 / 315 25.7 / 329 stock L98 24 lb/hr 22.9 / 293 24.3 / 311 25.1 / 321 25.6 / 327 26.8 / 343 28.0 / 359 Ford SVO 30 lb/hr 28.6 / 366 30.3 / 388 31.1 / 401 32.0 / 409 33.5 / 429 35.0 / 448 Non-OEM