AIM MXL Map Output

[kungfuSiR]

Hey Guys,

I'm having some issues with the MAP sensor output to our MXL Pro dash. The output from my S300 is mbar, you can change the input type in the AIM software to PSI or KPA however I don't think the conversion is correct as I'm seeing boost values way higher then they are in my Hondata Datalog. It seems like the conversion that the AIM dash is doing is a differential conversion which is causing the value to be much higher then it should be. Instead the conversion should be a relative conversion relative to vacuum.

I saw that for the CAN output to the Motec dash you guys use KPA and I was wondering if we might be able to get the same type of output on the serial channel, or is there something I'm doing wrong in my setup in the Dash that's messing up the conversion factor? Any insights would be appreciated.

Thanks

[Hondata]

How is it connected - using CAN? The S300 does not do any unit conversion so the setting must be in the MXL software.

[kungfuSiR]

It's connected using the RS232 output. According to your packet description in the Help section the output is mbar, I've attached the screenshot from that section.

[Hondata]

This is a question for Aim.

[kungfuSiR]

Hmm, I thought it was more what you guys were transmitting to the dash? Based on your documentation it shows that the Hondata is sending the data in mbar, so I would think this has nothing to do with AIM.

[Hondata]

Yes, the MAP is in mbar, and the unit is fixed. ie there is no adjustment in the s300. If you want a different conversion ro the conversion is wrong then that has to happen in the Aim dash / software.

[kungfuSiR]

Just wondering why the output for AIM is in mbar when you guys chose to output it in kPa for Motec? I'd imagine everyone would have the same problem converting mbar to PSI or kPa, might be worth considering changing the output format or at least giving an option to select what is output from the Hondata.

Thanks

[Hondata]

We don't have a different output for Motec. It is the same serial packet, or if using CAN, the same CAN packets.

[kungfuSiR]

We don't have a different output for Motec. It is the same serial packet, or if using CAN, the same CAN packets.

I don't know if that statement is correct, based of your packet format in the documentation the format is different:

CAN Protocol:

Screenshot 2017-07-12 18.39.48.png

You can see this differs from what you have in your serial output packet format description, also from your documentation:

Screenshot 2017-07-12 18.40.42.png

From talking with AIM this is what they have said:

Okay, so I *think* we are reporting the right value - but not the value that Hondata is logging. We are displaying and logging manifold air pressure (MAP), not boost specifically. The difference in the two is current atmospheric pressure. A MAP sensor outputs absolute pressure rather than gage pressure, or that's typically how they are calibrated. Does your Hondata also log or display atmospheric pressure - and/or does it display/log 'boost pressure' separate from MAP? With our current loggers we can do on-board math, whereas we could create a math channel that would subtract atmospheric pressure from MAP to give you boost pressure - but we don't have these tools for the MXL Pro. Or if Hondata has the values and can output them on the data stream, we can extend our ECU protocol.

Which if I look at the packet description would make sense. If the Hondata is only sending the raw MAP sensor output rather then the amount of boost the vehicle is actually seeing it would explain why this value is off. The conversion can be done, by taking into account atmospheric pressure, but I would think it makes more sense to actually send the boost value rather then the RAW map value, I can't see that being useful to anyone really. Would there be any possibility to change this?

[Hondata]

You misunderstand - when you mentioned the Motec, I did not know if it was using serial or CAN, as you did not specify, so I made a statement that covered both cases. In either case, the packet has a fixed conversion for MAP (mbar for serial and kpa x 10 for CAN), and there is no difference between Aim and Motec output packets.
Getting back to the initial problem - it is up to the datalogger / dash / software to do the unit conversions. Aim already does this for all the other items in the packet. If the MAP conversion is wrong, then the solution lies with the Aim conversion.

[kungfuSiR]

You misunderstand - when you mentioned the Motec, I did not know if it was using serial or CAN, as you did not specify, so I made a statement that covered both cases. In either case, the packet has a fixed conversion for MAP (mbar for serial and kpa x 10 for CAN), and there is no difference between Aim and Motec output packets.
Getting back to the initial problem - it is up to the datalogger / dash / software to do the unit conversions. Aim already does this for all the other items in the packet. If the MAP conversion is wrong, then the solution lies with the Aim conversion.

I see, I did mention in the first post that it was the Motec CAN packet that was sending in kPa but must have been missed. I'll talk more with AIM and see what they say, still would be nice to change this as I don't really see how it's useful as it is today. Definitely something you guys should consider and I would imagine it would be pretty simple to change or at least have an option to configure how you want it output.

[kungfuSiR]

One thing to mention as well, with the format you guys are sending it would be nearly impossible for them to do the conversion correctly because they would need to know what atmospheric pressure is before doing the conversion. I'm assuming you guys are grabbing this at startup, but the dash wouldn't have that information available to it.

With the newer AIM dashes you can configure MATH channels to display on the dash, but again it would be impossible to have this be correct all the time since the atmospheric pressure will constantly be changing.

Anyway, I definitely think this is something that should be improved.

[Hondata]

The display device should do the conversion, not the data provider. We have no plans to change this.