Calculating engine torque/horse power from datalogs

In summary, the conversation discusses the use of datalogs to calculate horsepower and torque. The given information includes rpm, mass, and time. The formula for drag is mentioned, as well as the equation for determining horsepower based on velocity and mass. The concept of energy and power is also brought up, with a mention of integrating to account for changing variables. The equation for determining tire diameter is also discussed, with explanations for the role of tire cross section, aspect ratio, and the number 25.4.
  • #1
bigwig
1
0
The idea is using datalogs to calculate horsepower/torque. The given information is rpm, mass, time...

Here is what I have so far:
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DragA=.5 * densityAir*Area of the front of the car*velocity^2

DragT=Weight*.7

rpm=given

Axlerpm= Engine Rpm/(Gear*final drive)

Diameter(inches)= Rim+ 2(tirecross section * Aspect Ratio/100)/25.4

v(ft/min)=(diameter/12) * pi * Axlerpm

Now 1hp=33,000ftlb/min so could I simply say HP=v*mass ? That does not seem correct at all, but the units work.

If I do F=MA, I get units of lb*ft/min^2 which is definitely not correct. Basically I'm confused and any help would be appreciated it.

Thanks in advance for any help.
 
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  • #2
RE: "HP=v*mass ?"

Energy is the product of Force applied over a distance.

Power = rate of energy (produced/consumed) = product of Force and speed.

Actually energy and power would be found by integrals, but I am assuming in this case that the force and speed are constant to simply the problem.

Torque is a product of force and moment arm.

The drag puts a force on the car. The tires must provide the force in balance, and in the opposite direction (assuming constant speed and not accounting for friction).

The driving axle must provide the torque, and the engine provides a torque to the driving axle (hence the gear ratio).
 
  • #3
"Diameter(inches)= Rim+ 2(tirecross section * Aspect Ratio/100)/25.4"

Could some explain this equation please? How does the tire cross section come into play and what is aspect ratio in this case? And 25.4?

Thanks!
 

FAQ: Calculating engine torque/horse power from datalogs

How do I calculate engine torque and horsepower from datalogs?

To calculate engine torque, you will need to use the formula: Torque = Force x Distance. The force can be measured by the engine's torque sensor, while the distance can be determined by the engine's rotation angle. To calculate horsepower, use the formula: Horsepower = (Torque x RPM) / 5252. The RPM can be found in the datalogs.

What is the difference between torque and horsepower?

Torque is a measure of the rotational force and is typically measured in pound-feet (lb-ft) or Newton-meters (Nm). It indicates the engine's ability to do work, such as accelerating the vehicle. Horsepower, on the other hand, is a measure of the engine's power output and is typically measured in horsepower (hp) or kilowatts (kW). It indicates how fast the engine can do work, such as reaching a certain speed.

Can I use datalogs from any type of engine to calculate torque and horsepower?

Yes, you can use datalogs from any type of engine to calculate torque and horsepower. However, the accuracy of the calculations may vary depending on the quality and completeness of the datalogs, as well as the performance of the engine itself.

How often should I calculate engine torque and horsepower from datalogs?

The frequency of calculating engine torque and horsepower from datalogs depends on your specific needs. If you are conducting experiments or making modifications to your engine, you may want to calculate it more frequently to track the effects of those changes. If you are just monitoring the overall performance of your engine, a less frequent schedule may suffice, such as once a month or every few months.

Are there any other factors that can affect the accuracy of calculated engine torque and horsepower?

Yes, there are several factors that can affect the accuracy of calculated engine torque and horsepower, including temperature, humidity, altitude, and fuel quality. It is important to take these factors into consideration and make any necessary adjustments to ensure accurate calculations.

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