Anyone have a base "manifold pressure comp" (baro) map for Emerald?

[bsimon]

I'm adding a 1 bar MAP sensor to my ECU to be used for baro compensation. Does anyone have some starting values for the Emerald "Manifold Pressure Compensation" map? I can guess the ignition corrections but I'm a little at loss for the injection corrections.

[slomove]

I'm adding a 1 bar MAP sensor to my ECU to be used for baro compensation. Does anyone have some starting values for the Emerald "Manifold Pressure Compensation" map? I can guess the ignition corrections but I'm a little at loss for the injection corrections.

 

Hello Bob, that depends what kind of sensor you got. If you have it calibrated (i.e. slope and offset to create actual baro pressure readings) then it is simple as the mixture should be leaned out proportionally to the absolute pressure. This approximately -10% per 10kPa pressure drop (and vice versa for pressure increase).

 

I my case however I used a cheapo GM baro sensor with negative zero-offset voltage (the old Emerald M3D model can not do that) and I had to fudge the offset and slope values to simulate the proper reading. If you have such a situation I can provide you the spreadsheet with the calculation although after 3 years I have a hard time to understand myself what I did there. But it works well.

 

Another problem with the old M3D was the lack consideration of injector dead time in the baro compensation. When I was driving up high in the local mountains the idle was starved to the point of stalling. After I complained I got a special PC software and firmware version from Emerald that was never officially released. But I suppose they fixed it in the new K3 model.

 

Let me know if I can help.

 

Gert

 

P.S.: for the simple case mentioned above your reference pressure is whatever you can get on an average day from the local airport (I suppose you are already pretty high up in CO), assuming that is the altitude what your map is optimized for.

[bsimon]

Hi Gert,

 

-10% per 10kPa pressure drop

 

That's exactly what I was looking for!

 

My M3DK was one of the last to go out the door without the internal baro sensor. I'll contact Karl and see if I need the updated firmware for the injector dead time situation. Can the updated firmware be flashed onto the Emerald, or is it a chip change?

 

I know the proper thing to do is ship my ECU back to Emerald for the K3 upgrade. I just don't want to be without a car during the summer months. Maybe this winter...

 

Altitude comp became a goal after the trip to Aspen for LOG 2007. For the most part the car ran fine. Going over Independence pass it was a little down on power, being a tad rich, but very drivable. Over 8000 feet the idle became quite rich, loading plugs and such. I'm comparing this to earlier trips with Weber 48DCOEs. Surprisingly, the Webers worked quite well during the mountain pass segments of USA2005.

 

The pressure sensor I have in mind is the Freescale MPX4100AP. The output is linear, 105kPa =4.8vdc and 20kPa = .3vdc @5.0Vs. I think this should be rather easy to calibrate for.

 

I'll let you know how I get on.

 

 

 

 

[slomove]

Can the updated firmware be flashed onto the Emerald, or is it a chip change?

yes, can be flashed. The updated PC software (rev. 1.8) has an additional field in the "Events" tab for dead time (I use 1 ms) and there is a new firmware file that Emerald needs to send to you according to the serial number. I know they have done this for other folks, too.

 

I'm comparing this to earlier trips with Weber 48DCOEs. Surprisingly, the Webers worked quite well during the mountain pass segments of USA2005.

That is not too surprising, given Benoulli's law (IIRC). Carbs are kind of self-adapting to altitude.

 

The pressure sensor I have in mind is the Freescale MPX4100AP. The output is linear, 105kPa =4.8vdc and 20kPa = .3vdc @5.0Vs. I think this should be rather easy to calibrate for.

That should work but extrapolating this to zero absolute pressure it sounds like the zero voltage offset is also negative (like my GM compatible SU105 from Well's Manufacturing). This one has a theoretical -0.84V offset (which my Emerald software just would not accept) and a slope of 0.0547 V/kPa. That gives almost the values you mention, maybe the same sensor inside?

 

Gert

[bsimon]

Thanks for all the tips Gert.

 

After looking at the problems involved, I determined it would be easier to wait until winter and post my Emerald back to Karl and have the K3 update done.

 

It seems that serial numbers after 41272 can get the hardware/firmware upgrade to the K3 model for around 30 quid. My serial is 42379. I understand they also install an internal baro sensor that would render the whole external sensor exercise academic.

 

For the time being, I purchased a cheap, light weight Win2000 tablet PC to dedicate to the car. It's small enough to stash behind the victim's seat as well. Should work nicely for data logging. I plan to have a high altitude map available to flash the ECU when required.