Setting up Boost on wideband

[Ellisd]

Can anyone tell me how to setup the "analoge in" in megatune to record boost?  I've managed to get the gauge to display 0 - 2bar (0 - 200 kPa) but i assume their's more to it than that?, as the neddle doesn't move at all.  I'm guessing i'll have to measure voltages from the map sensor at certains pressures to get some sort of scale.  I'm planning on using my greddy boost controller for this

Thanks in advance 

[rob@vems.co.uk]

Analog in is a tricky one to setup, you certainly need to measure the voltage range, then setup the values in the Analog input section of MegaTune

[Ellisd]

well this is a far as got so far,



Like i said i've got it looking the way a i want it, i just need it to work the way i want ha ha ha

Since i've wired the 'analoge in' in the gauge's button won't change modes.  Is this something you've heard of before?  It's spliced into the map input for the ECU through a 1 - 10k variable resistor

[rob@vems.co.uk]

Yes, the button shares the same converter channel as the analogue in, there is a setting for the button threshold, that you should look at - also make sure that you are not pulling the analogue channel down to ground through the resistor.

[z0tya]

unfortunatelly the analog input has a pullup to 4v. So difficult to use it correctly, but read this thread, maybe help you:
http://195.159.109.134/vemsuk/forum/index.php/topic,337.0.html

[Ellisd]

Yeah i have read through it a few times.  I'm going to get the button/display problem sorted 1st then i'll move onto measuring pressures and voltages and see about getting the boost logged.  I've managed to get something logged but the numbers have no relevence to actual values.  It works out roughly as 5.29 units = 1kPa  gauge reads about 500 at idle (-60 kPa on boost controller)  and 1400 at a 110 kPa

60 + 110 = 170 kPa
1400 - 500 = 900 units on analoge In gauge (scale 0 - 2047)

900/170 = 5.29 units per kPa (2dp)

[z0tya]

With the offset ang gain you can play to read something friendly.
Take some measurement pont like me.

Yeah i have read through it a few times.  I'm going to get the button/display problem sorted 1st then i'll move onto measuring pressures and voltages and see about getting the boost logged.  I've managed to get something logged but the numbers have no relevence to actual values.  It works out roughly as 5.29 units = 1kPa  gauge reads about 500 at idle (-60 kPa on boost controller)  and 1400 at a 110 kPa

60 + 110 = 170 kPa
1400 - 500 = 900 units on analoge In gauge (scale 0 - 2047)

900/170 = 5.29 units per kPa (2dp)

[Ellisd]

That's my job for the weekend  .  I'll be breaking out the multimeter and footpump to measure my voltages and pressures.  I'll let you's know what my result are

[Ellisd]

Ok i've finally had some spare time and broke my multimeter out.  Here's what i found:

kPa             volts           gauge reading

110             3.80
100             3.67
090             3.52
080             3.37
070             3.24
060             3.10           1323
050             2.95           1274
040             2.80           1213
030             2.67           1165
020             2.52           1102
010             2.38           1054
000             2.22           0995           


Input calibration 255    offset 158

I couldn't get the gauge reading any higher up the scale because i wasn't quick enough to read them    But 100kPa was about 1400 units on the gauge.  Can anyone help me make the gauge in megatune read what i want?  i'll send the megatune MSQ file if that helps


http://www.yousendit.com/download/WnBUbUpURnd3TGpIRGc9PQ

[rob@vems.co.uk]

Are you working from the .ini configuration example I gave here?
http://195.159.109.134/vemsuk/forum/index.php/topic,337.msg3373.html#msg3373

If so you may be able to use:
{ ((5/255)*analogIn) - 995 }

[z0tya]

Hello!

The kPa is absolute or relative pressure?

[Ellisd]

I can't really remeber what i did to get these values now as i've been playing about that much.  The INI file i'm using is in the attached link if thats any help?

http://www.yousendit.com/download/WnBUbUpURnd3TGpIRGc9PQ

The values are relative to pressure (110kPa is equal to 1.1 bar boost)  the gauge drops to about 600 when in vacuum (-60kPa on my boost gauge).  I'm assuming it will still be linear

[rob@vems.co.uk]

I see that you have
map      = {analogIn/10.235}

So I did a few calcs:

kpa   value/10.235   Raw value      
60   1323   13540.91   3357.08   55.95133333
50   1274   13039.39   2855.57   57.1113
40   1213   12415.06   2231.23   55.78075
30   1165   11923.78   1739.95   57.99833333
20   1102   11278.97   1095.15   54.75725
10   1054   10787.69    603.87   60.3865
0    995    10183.83      0.00   
         Average =    56.99757778
   So if we use kpa = (Raw value - 10184) / 57         
   Raw value   minus 10184   divide 57   
   12748   2564   44.98245614   
         45kpa   

So you can try:
map      = {(analogIn-10184)/57}

[Ellisd]

Thanks for this.  I have no idea where i've got the the /10.235 from lol.  Probably just playing about sticking random numbers in and seeing what happened.  I'll give this a bash tonight and see what happens. I wish you could calibrate it like the full version of megatune.  Where it asks you how many kPa = x amount of volts.  all these mathematical equations are just beyond me lol.  A B grade at GCSE doesn't get you very far nowadays ha ha ha

[rob@vems.co.uk]

Experimentation is where I've learnt it all from (that's suggesting that I got the numbers right, they could be waaaaay off!) - I got a grade C GCE (GCSEs came in the year after I left school) if they'd made maths based on.

We could get a better value if the measurements were taken with Raw values and if we could get accurate pressure readings from a known pressure source.

I agree that it would be great if you could punch in a calibration value, and have a simple way to sort this out, but unfortunately usability is lacking in that area.