Barometric correction error?

[MK]

Hi folks,
I suspect I have run into a bug with the barocorr - feature.

I have a MS1, V2.2 board using the ms_extra, Code 29v.
I run on AlphaN and thought it'd be a good idea to use the MAP sensor to have const barocorr active.

Unfortunately the bike (RZ350 twostroke) is running like crap above 500 m ... much worse than ever with carbs. At home (90 m) everything is fine.

I did a test with the stim where I set it to a medium load state and just changed the MAP.

When MAP is going down (simulating uphill cruise) the barocorr gauge is going up. Same with the injector pulse widths they raise and richen instead of leaning out.
The range is some 99% correction at 99 kpa and some 103% at 92 kpa.

What I expect would be the exact opposite - when going up the air density is going down, so I need to lean out the fuel supply.

Can anybody confirm my suspect and maybe guide which code line I have to hack.
(I'm used to Fortran and C/C++ from work, so I assume hacking, recompiling and loading it to the MS would be possible for me)

Thanx in advance
Martin

[richyvrlimited]

I may be wrong here but I don't think Barro correction works like that.

AFAIK two MAP sources, one off the engine pressure/vacuum (which you don't have) and one of the atmostphere pressure.

On startup MS takes a reading from the main sensor and this is the 'base' setting, then as your elevation changes it correlates this 'base' against the 2nd MAP sensor and adjusts the fueling based on the differences.

[slow_hemi6]

Not if you read the manual.
http://www.msextra.com/manuals/MS_Extra ... tm#conbaro
Martin if you have it set up the way it is shown, (Hardware and software) then maybe there is a problem.

[richyvrlimited]

Not if you read the manual.
http://www.msextra.com/manuals/MS_Extra ... tm#conbaro
Martin if you have it set up the way it is shown, (Hardware and software) then maybe there is a problem.

doh... that'll teach me not to scroll down

[MK]

Yep - I have the std. MAP sensor, I have AlphaN and I used the settings shown (const Baro corr in AlphaN to yes and second sensor to not fitted).
And it's surely not connected to the intake manifold ;-)

Do you need the msq & log posted, or can you reproduce the behavior?

[newtyres1]

Martin,

What you are seeing is correct. For cars running speed density it was assumed that more fuel was needed at higher altitudes due to lower exhaust back pressure making the engine more efficient. However this has been the subject of much debate and many people have questioned this approach. In MS2 I believe that baro correction is adjustable. In your case you may have to alter the values in the barofactor4250.inc or kpafactor4250.inc files, but I am not sure whether this information is correct or which file to edit. A bit of bench testing might sort it out. Maybe someone will chime in, I'm sure at least one person has done this, maybe search the forum if you haven't already. On my bike running alpha-n I see approx 0.5 AFR drop at 500m compared to sea level, I do not use baro correction, or any correction actually, straight open loop. Baro correction that works properly would be a very handy thing to have.

Ian.

[MK]

Thanks for that clarification. So it's not a bug it's a feature ;-)

I'll have a look into the inc files and see what I can tweak
(up to then: Goodbye, barocorr!)

BTW: Somebody advised to put the inc's into the source dir, recompile the code and load it to the MS. Is that right, or is it just enough to hack the inc's in the MegaTune directory and put the msq on the ECU?

[jsmcortina]

To change the way the fuel is calculated based on baro correction, you must change the file, recompile and re-download the firmware.
Also, copy those files to Megatune.

James