Measuring Engine Torque with Alternative Fuels | How-To Guide

Click For Summary
SUMMARY

This discussion focuses on measuring engine torque using alternative fuels, specifically biodiesels, without access to a traditional dynamometer (dyno). Participants emphasize the necessity of applying a load to the engine to obtain accurate torque measurements, suggesting methods such as using a heavy flywheel and a torque transducer to record angular acceleration. The conversation highlights the challenges of calculating torque from horsepower figures and the importance of timing the engine's acceleration to peak RPM (3600) as an alternative method for performance comparison. A recommended resource on inertia dynos provides further insights into the measurement process.

PREREQUISITES
  • Understanding of engine specifications, including horsepower and RPM.
  • Familiarity with torque measurement techniques and tools, such as torque transducers.
  • Basic knowledge of biodiesel fuels and their impact on engine performance.
  • Experience with DIY engine testing setups, including flywheel and load application methods.
NEXT STEPS
  • Research how to build a DIY inertia dyno for engine torque measurement.
  • Learn about torque transducer calibration and usage for accurate readings.
  • Investigate the effects of different biodiesel blends on engine performance metrics.
  • Study the relationship between engine load, RPM, and torque output in small engines.
USEFUL FOR

Engine builders, automotive engineers, and hobbyists interested in measuring engine performance with alternative fuels, particularly those exploring biodiesel applications.

eoe
Messages
3
Reaction score
0
i've got an engine to work with, and i have the basic specs of it like peak hp @ an rpm. but, i don't have figures for torque. I need to know how i can measure the torque of the engine with different fuels. I calculated the torque of the engine from their hp figure, but I'm having trouble figuring out a way i can measure the torque once i put in various types of fuels (biodiesels).

the engine won't be in a vehicle, and i don't have access to a dyno. i know its possible to calculate torque from acceleration, speed, and time, but i can't seem to find it/figure it out.

thanks in advance
 
Engineering news on Phys.org
Your going to need a dyno if you want to do any meaningful measurements. Without putting a load on the engine there is just no way that you can accurately compare performance of different fuels or even take any actual torque measurements.

The only way I can think of doing is to connect the output shaft to an oversize flywheel in a torque transducer in between. Throttle up the engine and record the angular acceleration.
 
I don't even know how you have calculated peak torque from the peak horsepower figure. You definitely need some driven equipment (preferably a dyno) to measure torque. A heavy flywheel might give you a pretty good estimate unless the engine is turbocharged (which, given that you're talking about biodiesels, is a definite possibility).
 
You can't do it eoe, not without practical data.

Fuel is the worst possible variable as an accurate combustion model is incredibly difficult to find for simulations and requires vigorous validation.
 
i calculated the torque from looking at the formula for power. and i used the engine's measured stroke as the distance, but now I'm thinking that doesn't really work? all i'll have is a hand held tachometer (with a laser) that i will measure off the flywheel. and the engine isn't turbo'd, its a small engine rated at 6.5hp. If i can't measure torque, i can just think of another way to determine which fuel will let the engine be more powerful.

would it work if i were to time how fast it takes the engine to go from idle rpm to peak rpm (3600) with each fuel? I think i'd have to bolt something on the flywheel to put the engine under load in order to time it better.

thanks for the replies
 
Time to get building your own dyno then. A cheap and cheerful option would be to use a heavy flywheel and brake it somehow with a known amount of force. This will give the engine a load and you can measure the rpm drop, an engine with higher torque output will keep the flywheel spinning at a constant rate under a higher load.

You will nead to repeat this at several different rpm to get an indiation of the variation of torque. Also be sure to note the rpm fluctuations as you will also have some indication of the cyclic variation.

Edit found this site, not read it all but it looks useful: http://www.dyno-dynamometer.com/how_dyno_works.htm
 
Last edited by a moderator:
thanks chris, that site is extremely useful. I think I've got it figured out now. it has a part about an "intertia dyno" which is just like what i was describing, so i won't need to provide a load for on the flywheel besides its own weight. i really appreciate all the help
 

Similar threads

Specified Torque Specs on Automotive Fasteners -- Required or just suggestions?
  • · Replies 13 ·
Replies
13
Views
4K
Automotive "Engine fuel consumption map" without the torque possible?
  • · Replies 5 ·
Replies
5
Views
2K
Automotive How to plot a power and torque graph for an engine?
  • · Replies 18 ·
Replies
18
Views
7K
How much should I adjust torque when using anti-seize?
  • · Replies 22 ·
Replies
22
Views
6K
How do I calculate the torque of an Internal Combustion Engine?
  • · Replies 6 ·
Replies
6
Views
5K
Automotive Does vehicle weight have an effect on torque capacity of the gearbox?
  • · Replies 5 ·
Replies
5
Views
4K
Plotting a Power Graph using Torque & RPM
  • · Replies 3 ·
Replies
3
Views
4K
How to Measure Torque Required for motor to spin a rotating shaft?
  • · Replies 3 ·
Replies
3
Views
5K
Wedge Anchor Torque Spec vs Ultimate Tension Spec
  • · Replies 18 ·
Replies
18
Views
3K
A practical way to vaporize fuel for high MPG?
  • · Replies 35 ·
2
Replies
35
Views
2K