[ric355]

Why I spend more money buying a second baro if I run pure alpha-n?

Agreed if you don't need the first one then you can just use that as the baro (but that is not what your software change does).

[RenanBecker]

I have done little more mods to changes the baro value when the algorithm is Speed density or Alpha-N.

With this mode the PW is ajusted by the variation of atmosferic air pressure when using "multiply VE value by map:baro" and Pure Alpha-N no matter where I start the engine, if is seal level or not.
So when go uphill the atmosferic pressure drops the PW get smaller and when go downhill the PW get bigger like the air density does.

Its needed to left the MAP sensor unconected
Mod in init.ino
The original 201905 firmware

Code: Select all

{
        currentStatus.baro = currentStatus.MAP;
        //EEPROM.update(EEPROM_LAST_BARO, currentStatus.baro);
        storeLastBaro(currentStatus.baro);
    }

The modified version, that allows baro correction using the internal map when Alpha-N is selected and no second baro sensor is added:

Code: Select all

 {
      if((configPage2.fuelAlgorithm == LOAD_SOURCE_TPS) && ( configPage6.useExtBaro != 1 ))
      {
        currentStatus.baro = 101;
           /* turns the pw multiplied by ( map/101 kpa) so when atmospheric pressure drops the PW well be reduced in the same way
         * example: 101kpa at 25Cº and 50% humidity Air density = 1.1766kg/m³
         * 90kpa at 25Cº and 50% humidity Air density = 1.048kg/m³ (1.048/1.1766)*100 =89,07% or 89% of sea level density
         * So with this the PW is reduced to 89% of the sea level PW
         * (90kpa/101kpa)*100 =89,10% 
        */
        storeLastBaro(currentStatus.baro);
      }
      else
      {
        currentStatus.baro = currentStatus.MAP;
        //EEPROM.update(EEPROM_LAST_BARO, currentStatus.baro);
        storeLastBaro(currentStatus.baro);
      }
      
    }

[Broke4speed]

To utilize the onboard MAP sensor for Baro correction instead of MAP-based fueling, could you re-route the signal from the sensor to one of the available Baro-in pins? Snip the signal pin on the PCB (or de-solder), and run a jumper to a useable input? If you're already Alpha-N, that is.

[edit]Posted too slow. I see your code above that means the physical method isn't required .

[PSIG]

Why I spend more money buying a second baro if I run pure alpha-n?

Multiply MAP when using Alpha-N should run the engine better than pure A-N. Unless you have tested to find that is not true, then it would be assumed you will use the primary MAP sensor for blended A-N, requiring a second sensor for real-time barometric corrections. Sensors are very inexpensive, with many examples online (new) for $5 and up. Your choice! But the ability to answer your concern is already here.

If not using the primary MAP for Multiply MAP, then you can reassign the sensor. Set your primary sensor as the External Baro Sensor as in the image above, selecting pin A3. In the init.ino file, change the default MAP sensor pin (under your board type) to an unused pin, e.g., change line pinMAP = A3; to pinMAP = A12;. The primary MAP sensor on Speeduino will now be used as the real-time baro sensor.

David

[RenanBecker]

If not using the primary MAP for Multiply MAP, then you can reassign the sensor. Set your primary sensor as the External Baro Sensor as in the image above, selecting pin A3. In the init.ino file, change the default MAP sensor pin (under your board type) to an unused pin, e.g., change line pinMAP = A3; to pinMAP = A12;. The primary MAP sensor on Speeduino will now be used as the real-time baro sensor.

David

I have tested this trick now, and noticed two things:
1) with "Multiply MAP" off, the changes in "second" baro read does nothing with the PW

2)with "Multiply MAP" on, it does the correction, but related to "map" so the trick in firmware doesen't work because its needed 2 sensors and need map conected to intake

So to have a constant baro correction is needed to have 2 sensors, 1 connected in manifold and 1 left open, but as i said before i don't what 2 sensors, because it's more sensors, more money spend, more things to fail.

"...In order of priority the specific aims are:

Low barrier to entry (ie price and availability of hardware...)."

By the end, I expect the modification done would be helpful to others who are running Pure Alpha-N.
I appreciate all the help.

Thanks to everyone.

Renan Becker

[theonewithin]

With table blending now available which is a better option than pure Alpha I don't see much need

And cost... $15 for a sensor.

If your worried about reliability then a Speeduino is NOT for you.

[PSIG]

Renan - correct, it is still sensing primary MAP from a dead-end source, and altering from there as baro changes, e.g., no fueling change if baro = 101.3 and less fuel if baro = 90. Because primary MAP is fixed at 101, MAP Multiply will have no effect (still pure A-N), but baro corrections will act against that value. If your dead-end is not reporting 101 kPa constantly, you may need a pullup resistor on your new primary MAP pin, and calibrate with 101.3 at full regulated voltage. In this way it should compare against the fixed MAP, and alter fueling based on the barometric reading. That's the theory anyway.

David

[RenanBecker]

Renan - correct, it is still sensing primary MAP from a dead-end source, and altering from there as baro changes, e.g., no fueling change if baro = 101.3 and less fuel if baro = 90. Because primary MAP is fixed at 101, MAP Multiply will have no effect (still pure A-N), but baro corrections will act against that value. If your dead-end is not reporting 101 kPa constantly, you may need a pullup resistor on your new primary MAP pin, and calibrate with 101.3 at full regulated voltage. In this way it should compare against the fixed MAP, and alter fueling based on the barometric reading. That's the theory anyway.

David

This is exactly what my code modification does, it does the baro correction compared to sea level pressure without add anything more in the hardware.

Edit:
Soon as I install the speeduino in the motorcycle I come back to post some datalogs to compare PW and lambda values from my mod to the original code.

[cornwallav8r]

I am following this thread a bit, as I am setting up my first Speeduino on a vw restoration I'm in the middle of. I know it's an old discussion, but it seems to me the issue is determining pressure due to altitude for air density correction correct? If you simply need a reliable altitude and temp for the gas law calc, why not just read exact altitude from a GPS instead of a second baro? Doesn't the Speeduino interface GPS somewhere? Or maybe I am missing something, my thermo dynamics and physics classes were a long time ago.

[PSIG]

The pressure (calculated density) of the air is required, regardless of physical altitude. The values can affect both fuel and spark, and potentially other sub-systems, but depends on which mode you're using.