9.86 or 10.44 E85 compression ratio..?
TECH Fanatic
Joined: Feb 2015
Posts: 1,080
Likes: 178
Just using it as an example, It has some validity but not a bible by any means. There are many other variables and now with computers controlling timing and fuel it's possible to get more power than you could have with the same combination pre-computer since you can control fuel and timing in individual cylinders.
Launching!
Joined: Mar 2019
Posts: 267
Likes: 171
Inertia dynos measure work, not torque. They measure the acceleration of large drums during a pull and using newton's 2nd law of motion (force = mass x acceleration), they calculate the torque output from horsepower (tq = hp x 5252 / rpm) and then plot both curves. Since steeper (numerically higher) gears increase the acceleration rate, this reads as higher horsepower (work) at the rear wheels, skewing the results. Correction factors do their best, but they are never going to make it 100% accurate.
Loading dynos use a steady resistance using a strain gauge to measure torque output. This gives you the raw torque output at the rear wheels and then horsepower is calculated from torque (hp = tq x rpm / 5252).
Going from a heavy crank/rod/piston assembly to a much lighter crank/rod/piston assembly will show an increase in power on an inertia dyno, but a decrease in power on a loading dyno due to the changes in rotating mass and how it's measured. Going from heavy wheels and tires to light wheels and tires will show up as a horsepower increase on an inertia dyno.
This is why I advise using the dyno as a tuning tool only, not for real world power numbers. If you want to know how well an engine runs, take it to the track.
Loading dynos use a steady resistance using a strain gauge to measure torque output. This gives you the raw torque output at the rear wheels and then horsepower is calculated from torque (hp = tq x rpm / 5252).
Going from a heavy crank/rod/piston assembly to a much lighter crank/rod/piston assembly will show an increase in power on an inertia dyno, but a decrease in power on a loading dyno due to the changes in rotating mass and how it's measured. Going from heavy wheels and tires to light wheels and tires will show up as a horsepower increase on an inertia dyno.
This is why I advise using the dyno as a tuning tool only, not for real world power numbers. If you want to know how well an engine runs, take it to the track.
TECH Enthusiast
Joined: Mar 2013
Posts: 503
Likes: 38
Inertia dynos measure work, not torque. They measure the acceleration of large drums during a pull and using newton's 2nd law of motion (force = mass x acceleration), they calculate the torque output from horsepower (tq = hp x 5252 / rpm) and then plot both curves. Since steeper (numerically higher) gears increase the acceleration rate, this reads as higher horsepower (work) at the rear wheels, skewing the results. Correction factors do their best, but they are never going to make it 100% accurate.
Loading dynos use a steady resistance using a strain gauge to measure torque output. This gives you the raw torque output at the rear wheels and then horsepower is calculated from torque (hp = tq x rpm / 5252).
Going from a heavy crank/rod/piston assembly to a much lighter crank/rod/piston assembly will show an increase in power on an inertia dyno, but a decrease in power on a loading dyno due to the changes in rotating mass and how it's measured. Going from heavy wheels and tires to light wheels and tires will show up as a horsepower increase on an inertia dyno.
This is why I advise using the dyno as a tuning tool only, not for real world power numbers. If you want to know how well an engine runs, take it to the track.
Loading dynos use a steady resistance using a strain gauge to measure torque output. This gives you the raw torque output at the rear wheels and then horsepower is calculated from torque (hp = tq x rpm / 5252).
Going from a heavy crank/rod/piston assembly to a much lighter crank/rod/piston assembly will show an increase in power on an inertia dyno, but a decrease in power on a loading dyno due to the changes in rotating mass and how it's measured. Going from heavy wheels and tires to light wheels and tires will show up as a horsepower increase on an inertia dyno.
This is why I advise using the dyno as a tuning tool only, not for real world power numbers. If you want to know how well an engine runs, take it to the track.
This is very true, a dyno is only a tuning tool. I always tell everybody to not get hung up on any dyno number and to take it to the track. The track doesn't lie but dynos do every day.
