I need somebody to double check my work I think my math is wrong somewhere

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SUMMARY

The discussion centers on verifying calculations related to horsepower and torque derived from vehicle data. The user reports a discrepancy where their calculated horsepower is approximately 25% higher than the expected value of 447 horsepower and 396 torque. Key formulas mentioned include the relationship between power and torque, specifically Power = Torque * (rotational speed). The user also notes the importance of using the correct units for torque, which is typically foot-pounds in the U.S. and Newton-meters in the metric system, and emphasizes the conversion of revolutions per second to radians per second for accurate calculations.

PREREQUISITES
  • Understanding of basic physics principles related to power and torque
  • Proficiency in Excel for data manipulation and calculations
  • Knowledge of unit conversions, particularly between foot-pounds and Newton-meters
  • Familiarity with dyno correction factors and SAE standards
NEXT STEPS
  • Review the formula for calculating horsepower from torque and rotational speed
  • Learn about the SAE correction factors used in dynamometer testing
  • Explore Excel functions for unit conversion and error checking
  • Investigate the significance of using radians per second in rotational dynamics
USEFUL FOR

Automotive engineers, performance tuners, and anyone involved in vehicle data analysis or dyno testing will benefit from this discussion.

soundengineer
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I need somebody to double check my work...I think my math is wrong somewhere..

so I've been working on a spreadsheet to take some data from a vehicle's data port...
and to transfer it into a Horsepower chart...
basically making a street Dyno...

I've gotten everything to work together...including graphing
but I know that my math has to be wrong somewhere and I need some help to get it right...

I think I've done all the conversions correctly...
I know I've done all the lookup from my data page correctly...

The Data I used is from a vehcile on the dyno...this vehicle made 447HorsePower and 396 Torque
but my excel math seems to say it s a lot higher...a lot higher..my end result is 25% or so higher than what it should be...
I've even added in dyno correction factor that every dynomometer uses to get an SAE corrected valueMy link to my excel spreadsheet...in a zip file...
too big for me to post it...
http://www.audiohelix.com/physics/
 
Last edited:
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In a consistent system of units we have:

Power = Torque * (rotational speed)

You stated that your are measuring power in units of horsepower (instead of, for example, watts).

When you say 396 Torque, you are ommiting the units. The most likely possibility in America is foot-lbs, whereas with the metric system torque is measured in Newton-meters.

The metric unit for angular speed is radians per second (not revolutions per second, as engines are often quoted). To convert revolutions per second to radians per second multiply by 2*pi = 6.28.
 

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