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Normalization calculations
Thursday, October 18, 2018
   
  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




 
   
 

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