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 Post subject: Re: Road Dyno
PostPosted: Mon Jan 07, 2019 2:06 am 
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Joined: Thu Nov 15, 2018 11:00 am
Posts: 716
Location: Europe, France (French/English)
two times seems about right to me.

I may sound stupid, but which format is the RR dyno reading? how should be the column sorted? and is there a particular file where I can retrieve these value you gave me?

Thank you for your time and help.


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 Post subject: Re: Road Dyno
PostPosted: Mon Jan 07, 2019 5:24 pm 
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Experienced

Joined: Thu Nov 15, 2018 11:00 am
Posts: 716
Location: Europe, France (French/English)
Okay I'm getting insane I think.

I attached one log of a pull I made. When I use the button "load from file" and then read from file, loading this doesn't work.

What should be the column format for it to work?
I did try to change the time format to 00:00:00.000; 00:00.000 and 00.000 without any success, always getting blank dyno or numbers like 104000hp.


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 Post subject: Re: Road Dyno
PostPosted: Tue Jan 08, 2019 5:55 pm 
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RomRaider Developer

Joined: Wed May 20, 2009 9:49 pm
Posts: 7031
Location: Canada eh!
I provided the files to load in the correct format in my previous post. Save each run to csv comma separated format.

You may need to use US number format to read from a log file rather than semi-colon separated and . for decimal.


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 Post subject: Re: Road Dyno
PostPosted: Tue Jan 08, 2019 7:05 pm 
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Experienced

Joined: Thu Nov 15, 2018 11:00 am
Posts: 716
Location: Europe, France (French/English)
yeeeesssssssssss.

I'm really sorry to have asked again. I misinterpreted your former post!

so I simply converted the time to a simple integer like this
Code:
Time   Engine Speed (RPM)   Throttle Position (%)
0   1300   10
1   1328   100
82   1345   100
162   1393   100
242   1408   100
322   1442   100
402   1478   100
525   1522   100
652   1586   100
764   1643   100
891   1695   100
1004   1756   100
1131   1808   100
1249   1878   100
1361   1929   100

or like this
Code:
Time   * Engine Speed (RPM)   * Throttle Position (%)
25168   1377   99
25280   1327   99,5
25408   1423   100
25529   1423   100
25641   1478   100
25769   1530   100,5
25881   1568   100
26012   1620   100,5
26117   1662   100,5
26196   1702   100
26283   1741   100
26410   1783   100
26528   1842   100
26640   1895   100
26761   1940   100


and it does work! Thank you!!!!!!!


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 Post subject: Re: Road Dyno
PostPosted: Tue Jan 08, 2019 9:48 pm 
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RomRaider Developer

Joined: Wed May 20, 2009 9:49 pm
Posts: 7031
Location: Canada eh!
The time needs no change as it will use the first entry as the reference time.


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 Post subject: Re: Road Dyno
PostPosted: Thu Mar 26, 2020 1:49 pm 
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Newbie

Joined: Fri Sep 27, 2019 5:08 pm
Posts: 13
Location: Germany
Hello, i tried to understand how the road dyno calculates the wheel power. I dont get the same reults as the dyno.

I gues the programm calculates from engine speed change per time the vehicle speed change per time wich would be the acceleration. With what Newton said F=m*a we can now calculate acceleration force. Multiplied with vehicle speed it gets acceleration power in kW. The power which works in opposite direction is roll- and air resistance which have to be added to the calc. acceleration power.

The problem i see is that i dont calculate same accleration as the dyno does. I have to know which dv/dt is used. I have table from log attached, grey cells are interpolated, i wonder that the rpm for calc peak power wasnt in the table, so i guess the dyno interpolated this rpm point. I interpolated the time at calc peak power an then i tried with interpolated values 500ms before and after peak power, i took this 1 sec period and calculated from engine speed change in this 1 sec the vehicle speed change, but i dont get exact same kW numbers as the dyno.

Another question i would have is which number the programm takes for air density.


Here my calc in detail:

From table attached(500ms before and after peak power):
∆n = 638,773 (1⁄min)/sek

gives:
∆v = (638,773 1/min * 2π * 0,31715 m)/(60 sec/min * 2,49 * 2,93) = 2,908 m/s
which ist vehicle speed change per sec = dv/dt = a = 2,908 m/s²

Wheel radius for 225/45R17:
r_Rad = 17''/2 *0,0254 m/zoll+0,225*0,45 m = 0,31715 m

with:
F = m*a
F_B = 1542kg*2,908 m/s^2 = 4483,914N
P_B = F_B*v

Now vehicle speed at peak power:
v = (n*2π*r_Rad)/(i_G*i_D )
v = (5645 1/min * 2π * 0,31715 m)/(60 sec/min * 2,49 * 2,93) = 25,698 m/s = 92,511 km/h

Accelerationpower P_B:
P_B = 4483,914 N*25,6998 m/s = 115,225 kW

Power against the car:
P_W = m*g*f_Ro*v+ρ/2*c_w*A*v^3
P_W = 1542kg*9,81 m/s^2 *0,012*25,698 m/s+((1,227 kg/m^3 )/2)*0,29*2,09m^2*( 25,698 m/s )^3
P_w = 10,975 kW

Wheelpower P_Rad:
P_Rad = P_B+P_W = 115,225 kW+10,975 kW = 126,2 kW

The difference is (126,8 - 126,2)kW = 0,6kW which is quiet close already.
Uncertainties are air density and acceleration.
My question is mainly if anybody knows how the dyno calculates the car acceleration?

EDIT: wrong dynograph attached
2nd-5th: I am very sorry i messed something up in the calculations.
:oops:


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Last edited by Ned Fenders on Thu Mar 26, 2020 3:19 pm, edited 5 times in total.

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 Post subject: Re: Road Dyno
PostPosted: Thu Mar 26, 2020 1:57 pm 
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Joined: Thu Nov 15, 2018 11:00 am
Posts: 716
Location: Europe, France (French/English)
probably due to the fact that it is averaging on more than just one value that you calculated.

and 2kW is like less than the error induced by slight slope on the road, so nothing to be worried about.


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 Post subject: Re: Road Dyno
PostPosted: Thu Mar 26, 2020 2:11 pm 
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Joined: Fri Sep 27, 2019 5:08 pm
Posts: 13
Location: Germany
Yes, your right. I know the value for wheel power will only be correct if there is no slope and also no wind while logging.

I also tried with the 50 and 10 ms period but my result got worse.

Maybe someone knows how the dyno calculates the value for acceleration.


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 Post subject: Re: Road Dyno
PostPosted: Thu Mar 26, 2020 6:22 pm 
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RomRaider Developer

Joined: Wed May 20, 2009 9:49 pm
Posts: 7031
Location: Canada eh!
The raw data collected to determine acceleration depends on whether the car is AT or MT.
You can see the raw data in the rr_system.log if you used the Dyno feature live while driving. Otherwise it looks for the time, etc. from the log file you provided it to calculate HP.
The curve is based on a polynomial fit, selecting a smooth factor changes the degree of the polynomial.
This tool is for tuning comparison only. From a baseline, make changes and then test under the same conditions as the baseline to see you results. It will never match the results of a dynamometer.

https://github.com/RomRaider/RomRaider/ ... i/tab/dyno

Image
Dots represent the calculated values plotted on the graph, from which the curve is derived.


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 Post subject: Re: Road Dyno
PostPosted: Fri Mar 27, 2020 7:13 am 
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Newbie

Joined: Fri Sep 27, 2019 5:08 pm
Posts: 13
Location: Germany
Thanks a lot! This really helped me.
How did you mange to make those dots visible?
Is there the possibillity to get the polynomial out of the logger somehow?


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 Post subject: Re: Road Dyno
PostPosted: Fri Mar 27, 2020 8:33 am 
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RomRaider Developer

Joined: Wed May 20, 2009 9:49 pm
Posts: 7031
Location: Canada eh!
Its been a long time since I worked on that, I'd have to go and look at the code for a while.
You could probably do the same in a spreadsheet.


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 Post subject: Re: Road Dyno
PostPosted: Sun Jun 28, 2020 2:22 pm 
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Experienced

Joined: Sun Jun 03, 2007 12:08 pm
Posts: 222
Location: Gig Harbor, WA
I have avoided spending time with the logger due to my ancient tuning computer. Recently got a new tuning rig and finally spent some time figuring out how to get the dyno working from some old logs.

Pretty cool feature. Thanks for the work that has gone into this!

Question and or request: Is there a way to scale the dyno plot HP and TQ values? It auto selects these values and this causes the lines to not cross at 5250. Its strange to look at after years of comparison.

Thanks!


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 Post subject: Re: Road Dyno
PostPosted: Sun Aug 16, 2020 6:14 am 
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Newbie

Joined: Fri Sep 27, 2019 5:08 pm
Posts: 13
Location: Germany
dschultz wrote:
Its been a long time since I worked on that, I'd have to go and look at the code for a while.
You could probably do the same in a spreadsheet.


Thats what i have done now, it was quiet easy actually. But excel can only interpolate polynomial function up to 6.degree.

Does anybody know if the smoothing factor is equal to the degree of the polynomial?


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 Post subject: Re: Road Dyno
PostPosted: Sun Aug 16, 2020 8:55 am 
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RomRaider Developer

Joined: Wed May 20, 2009 9:49 pm
Posts: 7031
Location: Canada eh!
Ned Fenders wrote:
Does anybody know if the smoothing factor is equal to the degree of the polynomial?
Yes it is.


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