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Author Topic: Explanation of terms please.  (Read 8647 times)
woo
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« on: September 17, 2012, 02:05:39 PM »

Could you please explain the following items that appear in the information box underneath the dyno plot.  I have some experience with math and statistics, and have some ideas, but prefer not to make assumptions.

If I understood more about the smoothing algorithm I might be able to pre-massage the log to reduce bumps in the plots for very short runs.


Sample rate: 17 samples/sec
Smoothing: 5 @ diameter 6
Torque mult: 14.88

That last one seems to be the overall engine to wheels drive ratio, but I'm not sure how it is being calculated/estimated since the tire diameter is not known to the program.

 Huh
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« Reply #1 on: September 17, 2012, 03:38:11 PM »

Could you please explain the following items that appear in the information box underneath the dyno plot.  I have some experience with math and statistics, and have some ideas, but prefer not to make assumptions.

If I understood more about the smoothing algorithm I might be able to pre-massage the log to reduce bumps in the plots for very short runs.


Sample rate: 17 samples/sec
Smoothing: 5 @ diameter 6
Torque mult: 14.88

That last one seems to be the overall engine to wheels drive ratio, but I'm not sure how it is being calculated/estimated since the tire diameter is not known to the program.

 Huh

The sample rate is, on average, how many samples were present each second in the data log.

Smoothing is # passes @ window width.  So yours above means it had to do 5 passes averaging a window of 6 samples.  It is adaptive meaning it looks at how much variation exists (how spiky the data is) and adjusts accordingly until the graph is reasonable without spurious spikes along the way.

The torque multiplier is nothing more than engine speed versus vehicle speed.  Tire diameter doesn't come into play here: all you need to know is how fast the vehicle was moving at what RPM and you can get the torque multiplier.  It is not final drive ratio, although if the diameter of your tire was exactly 2 feet (unlikely but probably close), it would be!

Mike
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woo
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« Reply #2 on: September 17, 2012, 04:04:48 PM »

... The torque multiplier is nothing more than engine speed versus vehicle speed.  Tire diameter doesn't come into play here: all you need to know is how fast the vehicle was moving at what RPM and you can get the torque multiplier.  It is not final drive ratio, although if the diameter of your tire was exactly 2 feet (unlikely but probably close), it would be!

Mike
There you have it.  My tire diameter is ~ 24.3".

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The sample rate is, on average, how many samples were present each second in the data log.
The DashDaq log has about 30 lines per second.  But typically only one signal changes per line.  And mph, being an integer  Sad , less frequently than that.  So I wonder where the 17 came from?

Quote
Smoothing is # passes @ window width.  So yours above means it had to do 5 passes averaging a window of 6 samples.  It is adaptive meaning it looks at how much variation exists (how spiky the data is) and adjusts accordingly until the graph is reasonable without spurious spikes along the way.
How does it choose the window width?


Thanks for the reply.
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