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Altitude Density Tuning - Horsepower In The Air

What every car crafter needs to know about air, pressure, temperature, and humidity-because there's horsepower in the air

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Get Converted
These conversions come courtesy of the HP Books Auto Math Handbook by John Lawlor. Some data also came from Metals Progress Databook.

To Convert Multiply By
Atmosphere to inches of mercury 29.921253
Atmosphere to kilopascals (Kpa) 101.325
Atmosphere to psi 14.69595
Inches of mercury to atmospheres 0.0334211
Inches of mercury to kilopascals 3.37685
Kilopascals to atmospheres 0.0098692
Kilopascals to inches of mercury 0.296134
Kilopascals to psi 0.1450377
Pascal to psi 0.0001450
Psi to atmospheres 0.068046
Psi to inches of mercury 2.036021
Psi to kilopascals 6.894757
Parts List
Description PN Source Price
PerformAire weather PAE Summitracing.com $599.95
PerformAire weather PAE-O2 Summitracing.com $799.95
PerformAire weather comp PA2 Summitracing.com $399.88
PerformAire weather comp PA2-O2 Summitracing.com $699.88
Summit Logbook G5155 Summitracing.com $4.95
NHRA Correction Factors
Altitude Above
Sea Level (Ft.)
E.T. Factor MPH Factor
1,500 0.9835 1.0171
2,000 0.9770 1.0241
2,500 0.9705 1.0311
3,000 0.9640 1.0381
3,500 0.9575 1.0451
4,000 0.9510 1.0521
4,500 0.9445 1.0577
5,000 0.9380 1.0661
5,500 0.9315 1.0731
5,800 0.9276 1.0773
Pressure Vs. Altitude
Altitude Above
Sea Level (Miles)
Percentage Of
Sea-Level Pressure
3.5 50%
10.0 10%
19.4 1%
29.9 0.1%
40.4 0.01%
49.2 0.001%
SOURCES
AltalabRacing Systems Analysis
Renick, WVPhoenix, AZ
304/497-2756602/992-2586
altalabinstrument.comquarterjr.com
  
AltronicsSummit Racing Equipment
Schaumburg Park, ILAkron, OH
88/464-2587800/230-3030
altronicsinc.comsummitracing.com
  
NHRA 
Glendora, CA 
626/250-2485 (tech) 
NHRA.com 
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