Fuel Pressure gauge - "bar" conversion done wrong in TS?

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Fuel Pressure gauge - "bar" conversion done wrong in TS?

Postby David_G » Wed Jan 25, 2017 12:36 pm

Hi,

My car has a vac-referenced pressure regulator and a "gauge style" sensor (referenced to atmospheric).

I made a custom.ini so the fuel pressure gauge is not only reading the raw pressure in kPa but directly displaying the differential fuel pressure across the injectors in bar instead of kPa.
I came up with the following code:
Code: Select all
[OutputChannels]

    Fuelpressure = { (sensor03 - map + barometer) / 100 }

where sensor03 is set as my Fuel-pressure sensor in generic sensor inputs.

However I just found out, that TunerStudio has implemented that gauge already, so creating the custom.ini actually was unnecessary.
The thing though is, that my selfmade gauge is showing different values than the one already implemented in TS.

I altered my formula until the two values matched and this is what I came up with:
Code: Select all
[OutputChannels]

    Fuelpressure = { (sensor03 - map + barometer) / 101.35 }


Can somebody explain to my why the conversion from kPa to bar would be done by dividing by 101.35 instead of 100 ?
1 bar = 10^5 Pa = 100kPa

So why 101.35? Seems to me that this is wrong in TS?

Thanks, David
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Re: Fuel Pressure gauge - "bar" conversion done wrong in TS?

Postby David_G » Fri Jan 27, 2017 11:18 am

Any input on this?
I guess the 101.35 come from some reference to sea level. But that should'nt be a division and it also would'nt make sense to refer Fuel pressure to sea level.
When setting the gauge to display kPa units, there is no such sea-level reference...
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Re: Fuel Pressure gauge - "bar" conversion done wrong in TS?

Postby ol boy » Sat Jan 28, 2017 8:54 pm

Each bar is 101.35 worth of kpa at sea level. Using baro for your current altitude helps reference the math then gets divided by 101.35.

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Re: Fuel Pressure gauge - "bar" conversion done wrong in TS?

Postby slow_hemi6 » Sun Jan 29, 2017 4:02 am

ol boy wrote:Each bar is 101.35 worth of kpa at sea level. Using baro for your current altitude helps reference the math then gets divided by 101.35.

Sent from my SM-G920V using Tapatalk


I thought 1 bar is 100kpa, 101.35kpa is 1Atmosphere (atm).
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Re: Fuel Pressure gauge - "bar" conversion done wrong in TS?

Postby jsmcortina » Sun Jan 29, 2017 5:51 am

What firmware?

:msq:

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Re: Fuel Pressure gauge - "bar" conversion done wrong in TS?

Postby motthomas » Sun Jan 29, 2017 5:53 am

ol boy wrote:Each bar is 101.35 worth of kpa at sea level. Using baro for your current altitude helps reference the math then gets divided by 101.35.

Sent from my SM-G920V using Tapatalk

I'm afraid that is incorrect. 1 bar is 100 kPa. 101.35 kPa is a reference to ISO standard atmosphere sea level conditions only. It is NOT to be used in unit conversion and I'm very surprised this was done by Tunerstudio.
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Re: Fuel Pressure gauge - "bar" conversion done wrong in TS?

Postby David_G » Sun Jan 29, 2017 7:45 am

Thanks for the input everyone!
Exactly my thinking. Pure unit conversion doesn't need any sea-level reference.

jsmcortina wrote:What firmware?

:msq:

James


Thats on the current 1.5.0 firmware.
But its also the same on the previous 1.4.1
Do you want me to post a .msq? I just thought that's not needed as this is a TS issue independent of Tune file.

I already had a look at the mainController.ini and this is where the "conversion" obviously happens
That also explains why there's no error when displaying in kPa - no conversion happening here!
Code: Select all
;fuel pressures
  fuel_press1_psi = {fuel_press1 * 0.147 }, "psi"
  fuel_press2_psi = {fuel_press2 * 0.147 }, "psi"
  fuel_press1_bar = {fuel_press1 / 101.35 }, "bar"
  fuel_press2_bar = {fuel_press2 / 101.35 }, "bar"
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Re: Fuel Pressure gauge - "bar" conversion done wrong in TS?

Postby jsmcortina » Sun Jan 29, 2017 8:10 am

Yes that looks to be an error in the firmware ini file. Nothing to do with TunerStudio.

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Re: Fuel Pressure gauge - "bar" conversion done wrong in TS?

Postby David_G » Sun Jan 29, 2017 8:26 am

Thanks for clarifying, James!

That means I can just move on and use my own gauge.
The "psi" values must be slightly off too then as 1kPa = 0.145psi and not 0.147

edit:
Also thanks for moving the thread to the right sub-forum, i thought that was a TS thing
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