PDg1
Published by Emo on 2005/5/15 (3914 reads)
Portable Dynamometer 1-st generation
PDg1 (Portable Dynamometer 1-st generation)
This project involves developing a small device that when used in conjunction with a laptop will let users Test&Tune their engines. It was inspired by a few articles on the internet.
The main goal is for us to get an HP/Torque curve of an engine like those from a real Dyno, get repeatable results to allow tuning the engine and to obtain as precise data as possible.
Some GOOD News:
- The prototype is ready and functional. The data is quite accurate and repeatable. ( more specific data will follow soon)
- The project will be mostly ( if not fully) open-source.
- Already tested on my 4gen Honda Civic Hatchback and Ivo's BMW 318 touring
Some BAD News:
- This is NOT a tool for morrons! It needs attention if you want to get accurate and usable results.
- This 1-st generation of the device requires a laptop to log and analyze the data.
Simplified theory of operation: First of all, let me say that this tool measures HP and Torque at WOT. There are some tweaks one can do to measure and tune part-throttle acceleration, but more on that later. If we want measure power, we should first measure torque. Torque * Time = Power. But how can we measure torque??? By doing a power run at WOT from almost idle to rev-limit, without using the clutch, we can assume that the engine RPM is proportional to the wheels RPM. If we know the physical dimentions of the wheels and their acceleration rate in time, we can calculate the vehicle's acceleration and how it changes during the run. We now know how the car was accelerated and by knowing its mass, we can calculate the force that was needed to create such an acceleration. Going back to the tyre dimentions, we can now calculate the torque on the tyre: R * F = Tq. Since we also know the tire rotation speed, we also know the power that is produced on the wheels. And since we recorded how that HP and Torqe changed in time while we were building RPMs, we can draw the HP as a function of RPM and Torque as a function of RPM.
One thing I'm intentionally leaving out is the wheel-spin. We have to avoid it in any cost as it WILL mess up our measurment. Therefor, one should choose such a gear that will first, accelerate without wheel-spin, and second, the engine will be able to go up to rev-limit it about 15 seconds. 2-nd and 3-rd gear are good candidates, but have in mind that the higher the gear, the more space you'll need for the run and the bigger the aerodinamic errors. I'm currently testing in 2-nd gear and it takes me 10s to rev from below 1000 to 7000 RPM.
PLEASE STAND BY FOR MORE...... there WILL be :)
PDg1 (Portable Dynamometer 1-st generation)
This project involves developing a small device that when used in conjunction with a laptop will let users Test&Tune their engines. It was inspired by a few articles on the internet.
The main goal is for us to get an HP/Torque curve of an engine like those from a real Dyno, get repeatable results to allow tuning the engine and to obtain as precise data as possible.
Some GOOD News:
- The prototype is ready and functional. The data is quite accurate and repeatable. ( more specific data will follow soon)
- The project will be mostly ( if not fully) open-source.
- Already tested on my 4gen Honda Civic Hatchback and Ivo's BMW 318 touring
Some BAD News:
- This is NOT a tool for morrons! It needs attention if you want to get accurate and usable results.
- This 1-st generation of the device requires a laptop to log and analyze the data.
Simplified theory of operation: First of all, let me say that this tool measures HP and Torque at WOT. There are some tweaks one can do to measure and tune part-throttle acceleration, but more on that later. If we want measure power, we should first measure torque. Torque * Time = Power. But how can we measure torque??? By doing a power run at WOT from almost idle to rev-limit, without using the clutch, we can assume that the engine RPM is proportional to the wheels RPM. If we know the physical dimentions of the wheels and their acceleration rate in time, we can calculate the vehicle's acceleration and how it changes during the run. We now know how the car was accelerated and by knowing its mass, we can calculate the force that was needed to create such an acceleration. Going back to the tyre dimentions, we can now calculate the torque on the tyre: R * F = Tq. Since we also know the tire rotation speed, we also know the power that is produced on the wheels. And since we recorded how that HP and Torqe changed in time while we were building RPMs, we can draw the HP as a function of RPM and Torque as a function of RPM.
One thing I'm intentionally leaving out is the wheel-spin. We have to avoid it in any cost as it WILL mess up our measurment. Therefor, one should choose such a gear that will first, accelerate without wheel-spin, and second, the engine will be able to go up to rev-limit it about 15 seconds. 2-nd and 3-rd gear are good candidates, but have in mind that the higher the gear, the more space you'll need for the run and the bigger the aerodinamic errors. I'm currently testing in 2-nd gear and it takes me 10s to rev from below 1000 to 7000 RPM.
PLEASE STAND BY FOR MORE...... there WILL be :)
