RPM/s²
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Re: RPM/s²
Still wondering why RPM/s^2
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James
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Re: RPM/s²
Agree that rpm already has factors of distance (traveled in 1 rotation) and time (in mins so /60 for S) so that covers Velocity.
Acceleration is deltaV/t so, rpm/s seems to be appropriate for deriving m/s^2.
Acceleration is deltaV/t so, rpm/s seems to be appropriate for deriving m/s^2.
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Re: RPM/s²
I suspect some additional filtration for RPM or vss is needed.
The sensor lags might be sufficient for RPM, haven't tried.
The vss input likely lacks those software filters, so its raw data.
When I first tried using the TQ/HP info in TS it was all over the place, so I stripped out the same RPM data from the logs and pasted it into another dyno "program" that runs in excel or libreoffice... VDR?
Had to play around with its filter a bit but it then produced sane numbers and very consistently.
I suspect vss data really needs a filter to be useful in this way.
The sensor lags might be sufficient for RPM, haven't tried.
The vss input likely lacks those software filters, so its raw data.
When I first tried using the TQ/HP info in TS it was all over the place, so I stripped out the same RPM data from the logs and pasted it into another dyno "program" that runs in excel or libreoffice... VDR?
Had to play around with its filter a bit but it then produced sane numbers and very consistently.
I suspect vss data really needs a filter to be useful in this way.
Always doing things the hard way, MS2 sequential w/ v1.01 mainboard, LS2 coils. 80 mile/day commuter status.
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Re: RPM/s²
Yes a lot of filtering, especially when using RPM.piledriver wrote: I suspect vss data really needs a filter to be useful in this way.
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Re: RPM/s²
That helps confirm your configuration. You're worried about unreasonable calculation results, but without knowing your configuration it's impossible for anyone else to know if the calc results are reasonable.
Re: RPM/s²
voila
Re: RPM/s²
How often does your GPS speed update? Having a delay in speed updating of even half a second will throw off the correlation between speed and RPM and mess up the power calcs.
Re: RPM/s²
I don't use a gps for speed, I used the VSS.
Re: RPM/s²
Why is your msq set up for GPS then?
Re: RPM/s²
The results with GPS were even worse than vss. No GPS was connected since the summer of 2015.Laminar wrote:Why is your msq set up for GPS then?
What's even more strange is that last time I drove while logging speed, I had changed that to VSS. No idea why that changed back.
Re: RPM/s²
So this is or is not your most recent configuration?
Re: RPM/s²
Look at the date
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Re: RPM/s²
I think what you are looking for is something like
([RPM]-[RPM-25])/([Time]-[Time-25])
Here is a screen shot of a dyno pull
http://www.nbs-stl.com/CRX/Dyno%20Sweep ... %20Sec.png
I do the same trick with MPH, KPH or VSS to get acceleration. 20 MPH Per Sec is accelerating hard.
Andy
([RPM]-[RPM-25])/([Time]-[Time-25])
Here is a screen shot of a dyno pull
http://www.nbs-stl.com/CRX/Dyno%20Sweep ... %20Sec.png
I do the same trick with MPH, KPH or VSS to get acceleration. 20 MPH Per Sec is accelerating hard.
Andy
Last edited by whittlebeast on Tue Apr 12, 2016 5:00 am, edited 1 time in total.
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Re: RPM/s²
That's RPM/s (i.e. first derivative of RPM) the OP says he wants RPM/s² (the second derivative)
James
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Re: RPM/s²
Which would be "jerk" or 1/smoothness. Could maybe be useful for drivability tuning, like overrun fuel/spark return etc.
Joachim
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Re: RPM/s²
I don't understand this.subwoofer wrote:Which would be "jerk" or 1/smoothness. Could maybe be useful for drivability tuning, like overrun fuel/spark return etc.
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Re: RPM/s²
Which part don't you understand?
RPM/s² (RPM dot dot) is likely related to TPS/s (TPSdot)
i.e. the rate of change of acceleration is related to rate of throttle opening.
James
RPM/s² (RPM dot dot) is likely related to TPS/s (TPSdot)
i.e. the rate of change of acceleration is related to rate of throttle opening.
James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk
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Re: RPM/s²
Yves, you're on speedtalk, right? The derivatives are described in detail in many cam motion discussions there. SchmidtMotorWorks had a great thread going for a while with a program to play with, even.
You have an object with a position.
If it is changing position that change is described by velocity.
If the velocity is changing, that change is described by acceleration.
If the acceleration is changing, that change is described by jerk.
So you are not using acceleration in your proposed calculation, you are using jerk, which describes how the slope of the acceleration rate is changing.
You have an object with a position.
If it is changing position that change is described by velocity.
If the velocity is changing, that change is described by acceleration.
If the acceleration is changing, that change is described by jerk.
So you are not using acceleration in your proposed calculation, you are using jerk, which describes how the slope of the acceleration rate is changing.