Calculate Horsepower & Torque w/ Break-In Stand for 68 Mustang

[stryped]

Is there a cheap and easy way to calculate horsepower and/or torque for an engine out of a car? I am restoring a 68 mustang and would like to run an engine on a break in stand I will build. It would be nice to be able to use it to tune the engine.
I read somewhere something about placing a magnet on the engine flywheel, measuring the rpm, then somehow calculating torque out of that but I am not sure.

 

[NFuller]

I don't think cheap and easy will get you anything precise or reliable. If you are looking to accurately measure horsepower as a function of the engine rpm, then I think you are in for a big project. If you are looking to just ballpark the max horsepower of the engine, you could do the following. Find a long straight road that is not in use, floor the gas, and accelerate the car over some distance $d$. After you cross that distance, record the car's speed $s$. Also look up the car's mass $m$. The average power will be
$$\bar{P}=\frac{ms^{3}}{4d}$$

 

[berkeman]

Is there a cheap and easy way to calculate horsepower and/or torque for an engine out of a car?

Have you looked at inexpensive in-car "dynomometers"? Here's an article testing their accuracy and discussing tradeoffs. If you are looking mainly to do A/B tuning comparisons, they may be a viable way to go...

http://www.caranddriver.com/features/do-inexpensive-performance-meters-work-feature

 

[NFuller]

Have you looked at inexpensive in-car "dynomometers"? Here's an article testing their accuracy and discussing tradeoffs. If you are looking mainly to do A/B tuning comparisons, they may be a viable way to go...

http://www.caranddriver.com/features/do-inexpensive-performance-meters-work-feature

Interesting, I did not know about these. It says most use an internal accelerometer. I wonder if there are any phone apps which would work the same way.

 

[berkeman]

Yes, when I did the Google search that led me to that link, one of the other links was comparing an iPhone app to those in-car products. I think my Google search was something like In-Car Dynamometer...

 

[cosmik debris]

Interesting, I did not know about these. It says most use an internal accelerometer. I wonder if there are any phone apps which would work the same way.

There are quite a few apps that give HP, quarter mile times etc, there are even dedicated devices in automotive stores. These all depend on accurate calibration and making consistent runs but are OK for development purposes. If you want to build a dyno, you will need to think of the best way to dissipate the power and measure that power or the torque. Mechanically you can use a brake or electrically a load bank, either way there will be heat. With an electric load it is probably easier to measure the power.

 

[stryped]

I don't think cheap and easy will get you anything precise or reliable. If you are looking to accurately measure horsepower as a function of the engine rpm, then I think you are in for a big project. If you are looking to just ballpark the max horsepower of the engine, you could do the following. Find a long straight road that is not in use, floor the gas, and accelerate the car over some distance $d$. After you cross that distance, record the car's speed $s$. Also look up the car's mass $m$. The average power will be
$$\bar{P}=\frac{ms^{3}}{4d}$$

The engine is not in the car. I wanted to make an engine break in stand and be able to utilize some sort of torque/poer messurement on that. I am just looking for a way to do befoe and after tuning comparing different mods

 

[CWatters]

Without a load on the engine the torque will be pretty much zero. So first problem is to make a load/brake that can handle the likely power. Then if you mount the engine so that you can measure the reaction torque you can calculate the power as...

Power = torque * angular velocity

(In the right units)

 

[jack action]

What you are looking for is called an inertia dynamometer. This site gives the fundamentals to build your own.