Automatic barometric correction

[jsilva]

Hi there!

I've been digging through the vems funcionalities and I haven't found one: automatic barometric correction (in real-time).

What I want to ask is: there is such functionality in the vems system? If yes, how to configure?

[rob@vems.co.uk]

To turn on Barometric correction you need to use MegaTune and go: Settings->Constants and set Barometric correction to On
God knows how it works though!

[GintsK]

But it is not real time correction anyway. Looks like all developers live in low lands.

In my country max level difference is ~250m. I do not need real time correction... until my ECUs was on cars only. Now I have one aircraft . Not VEMS because of lack of barometric control.

[Sprocket]

The only pressure sensor is the MAP sensor, so I would expect that if you have MAP sensor installed and run Alpha N with Baro Correction on, it uses the MAP sensor which is not connected to anything to sense atmospheric pressure and compensate?


Thats what I would expect, but you never ever know, until one of the developers confirm this

I have seen the KPA change as you would expect with the weather

[PeepPaadam]

I would love to get real-time barometric correction as it makes a big difference in hillclimbing (not in my country that is).

We could use stock 3wire barometric sensors from many cars (mainly VAG ones).

[jsilva]

My problem is the hillclimbing, my idea to fix it is to runing alpha-n and use the map sensor for barometric(its possible?). the car have a ms whith barometric correction working at 100%,the ms was translated for ohter car i plan to use a vems.   

[rob@vems.co.uk]

It looks like this has been addressed in the newest firmware: http://www.vems.hu/wiki/index.php?page=GenBoard%2FUnderDevelopment%2FFirmwareChanges

[1.1.48] - testing only. AlphaN new strategy added (upgrade possible with 2009-01-08 VemsTune or newer)

    * to use AlphaN without MAP sensor:
          o hybrid_rpm_m=FE or lower, but not 0 (so the load is sent in position 4-5 byte of the realtime vars, not MAP)
          o important: fill mapcorr table with all 00 (hint: at least set the 4 corners).
    * new mapcorr (boost map correction) strategy available for AlphaN with a MAP sensor (eg. charged + ITB):
          o hybrid_rpm_a=FF
          o hybrid_rpm_m=FF
          o config13 bit5=0 to lookup ign and lambda according to kpa (even at low RPM).
          o config13 bit2=1 for no automatic "alltime" load multiplication (yes, this is no mistake: because you do not want load multiplication below 100 kPa!)
          o important: fill mapcorr table (i/I comm commands). All 100 means neutral. With this configuration *MAP/100 is also applied above 100 kPa, automatically, so table stays flat and tuning becomes very easy. Maybe a small slope is a good idea to start with: 100 @ 100 kPa (below 100 kPa the table is not used at all) and 110 @ 320 kPa. If you need more than +10% at high kPa, that suggests the fuel system is not up to the job.
    * the old "hyprid tps and kpa smooth gradient" strategy is still available: which uses TPS for lookup RPM<hybrid_rpm_a and MAP when RPM>hybrid_rpm_m and interpolation in between. However, at high gear, boost might appear at rather low RPM (especially in a streetcar). The mapcorr strategy is also easier to tune
          o hybrid_rpm_a=14 (2000 RPM for example)
          o hybrid_rpm_m=1E (3000 RPM for example)
          o config13 bit5=0 to lookup ign and lambda according to kpa (even at low RPM). On the countrary bit5=1 means load (tps or kpa or mix depending on RPM, hybrid_rpm_a, hybrid_rpm_m relation) is used, the only option for a normally aspirated engine without MAP sensor.
          o config13 bit2=1 for no automatic load multiplication

[Sprocket]

Maybe its just me, and programmer speak, but i dont see anything in there for barometric compensation. All i can see is Alpha N with MAP blending for the likes of ITBs and forced induction, where the map sensor is connected before the throttle, therefore only ever reads ~100kpa (atmospheric) or above (boost). what about stand alone Alpha N with barrometric compensation, where if you tun at sea level then drive up a hill atmospheric pressure drops and the engine runs rich.

Maybe it can be used for barometric compensation but thats not how I read it.

I confirmed yesterday that it doesnt need much for the barometric pressures to change. While sat at the top of the Great Orm in Llandudno North Wales (not very high) with gale force winds and rain, MAP sensor was reading 98kpa and the engine was running rich with a 8% correction taking place. Drove down to the sea front (couldnt get any closer without getting your feet wet) with the weather improving and the MAP sensor was reading 100kpa and corrections were down to 2 - 3%

What is strategy for the barometric compensation setting in Megatune Constants menue?

[rob@vems.co.uk]

I think they are saying that you can use the MAP correction to adjust the fuelling to compensate for the change in air density seeing that it adds fuel based on a modified SD algorithm.

Put it this way, I ask:
"How does Barometric correction work with AlphaN"

The answer comes back:
"You need to check the release notes on 1.1.48"

And that Gentlemen is how that works...