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MEFI 1 Definition Question

 
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Trash



Joined: 06 Aug 2011
Posts: 7

PostPosted: Sat Aug 06, 2011 6:56 am    Post subject: MEFI 1 Definition Question Reply with quote

Currently tuning a marine motor with MEFI 1. If I modify the RPM/MAP/BPW table by adding a additional MAP column and RPM rows will I be able to upload it to the MEFI 1 ECM?

Will the MEFI 1 ECM recognize the larger table and work correctly?

Would it cause any damage to the MEFI 1 controller by attempting to upload the modified MAP table?

Thanks for any input.
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cbernhardt



Joined: 18 Apr 2008
Posts: 64

PostPosted: Sat Aug 06, 2011 3:38 pm    Post subject: Re: MEFI 1 Definition Question Reply with quote

Trash wrote:
Currently tuning a marine motor with MEFI 1. If I modify the RPM/MAP/BPW table by adding a additional MAP column and RPM rows will I be able to upload it to the MEFI 1 ECM?

Will the MEFI 1 ECM recognize the larger table and work correctly?

Would it cause any damage to the MEFI 1 controller by attempting to upload the modified MAP table?

Thanks for any input.


In the MEFI controllers the file that is loaded into the computer is a fixed size. Only a certain amount of space in the file is allocated for each data item. In the MEFI1 file the BPW vs. MAP/RPM table is 14 rows x 5 columns of 16 bit data. That means the table is allocated 14 x 5 = 70 spaces of 16 bit data or 140 bytes. This table starts at address 0xB633. The next table in the MEFI1 is the Voltage Compensation vs Battery Voltage and it starts at 0xB6BF. 0xB6BF 0xB633 = 0x8C or 140 bytes. There is only 140 bytes allocated for this table which means that the number of rows and columns is not saved in the computer.

If you increase the number of rows and/or columns in the BPW table you will just overwrite the data in an another existing table.

Changing the number of rows and columns probably will not harm the computer, but you will not get the results that you expect.

Charles
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Trash



Joined: 06 Aug 2011
Posts: 7

PostPosted: Sat Aug 06, 2011 9:33 pm    Post subject: Reply with quote

Charles,

Thanks for the answer, that's the best response I've gotten yet!!!

As a follow on, since I don't believe my controller uses the Voltage Compensation vs. Battery Voltage table, would I then be able to increase the MAP/RPM table withing the 140 byte limit , allow it to write to that memory location and have the controller read the expanded data?

Thanks for your patience and time.
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cbernhardt



Joined: 18 Apr 2008
Posts: 64

PostPosted: Sun Aug 07, 2011 4:40 am    Post subject: Reply with quote

Trash wrote:
Charles,

Thanks for the answer, that's the best response I've gotten yet!!!

As a follow on, since I don't believe my controller uses the Voltage Compensation vs. Battery Voltage table, would I then be able to increase the MAP/RPM table withing the 140 byte limit , allow it to write to that memory location and have the controller read the expanded data?

Thanks for your patience and time.


You could probably expand the table, write it, read it back in, and it would probably appear in Tunerpro that it was correct. The problem is that the table expansion ( the number of rows and columns) is only saved in the XDF file, not in the MEFI1 controller, so the controller would expect the BPW table to be at the old addresses and use the same old number of rows and columns.

Charles
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Trash



Joined: 06 Aug 2011
Posts: 7

PostPosted: Sun Aug 07, 2011 6:17 am    Post subject: Reply with quote

Charles,

Thanks, that all makes sense. What happens when the motor goes outside the table in regards to RPM or low MAP? Does it interpolate in a linear manner?
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cbernhardt



Joined: 18 Apr 2008
Posts: 64

PostPosted: Sun Aug 07, 2011 1:50 pm    Post subject: Reply with quote

Trash wrote:
Charles,

Thanks, that all makes sense. What happens when the motor goes outside the table in regards to RPM or low MAP? Does it interpolate in a linear manner?


I don't really know. All my data logging has been with the MEFI4a and the engine has never been outside the MAP or RPM limits.

Charles
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Trash



Joined: 06 Aug 2011
Posts: 7

PostPosted: Sun Aug 07, 2011 8:35 pm    Post subject: Reply with quote

I assume it does a linear extension or slope as the MAP will dip into the 30s on decel which is below the cureent MAP table. I guess I'll spin the motor to 6000 and see.
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Trash



Joined: 06 Aug 2011
Posts: 7

PostPosted: Wed Aug 17, 2011 7:33 pm    Post subject: Reply with quote

Charles,

Would I be able to redefine the RPM/MAP points to different values but keep the table the same size?
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cbernhardt



Joined: 18 Apr 2008
Posts: 64

PostPosted: Thu Aug 18, 2011 5:40 am    Post subject: Reply with quote

Trash wrote:
Charles,

Would I be able to redefine the RPM/MAP points to different values but keep the table the same size?


As far as I know there is no way to change the RPM or MAP points.

Could you upgrade to the MEFI4? The MAP points are from 20 to 100 in 10 Kpa increments and the RPM points are from 200 to 9000 in 200 rpm increments.

What software are you using?

Charles
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Trash



Joined: 06 Aug 2011
Posts: 7

PostPosted: Thu Aug 18, 2011 6:20 am    Post subject: Reply with quote

MEFI Burn, ScannerPro and Tuner Pro. I've been able to 'create' or modify the rows and columns in TunerPro, but I'm not sure it's changing the row and column labels only or the actual values the ECM uses.

I made one table with more MAP and RPM points, but as per our discussion earlier you stated it would not be recognized because of memory address issues.

I have also modified a table keeping the size the same but changing the RPM points. I have not tried to load this and run it yet.
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cbernhardt



Joined: 18 Apr 2008
Posts: 64

PostPosted: Thu Aug 18, 2011 8:19 am    Post subject: Reply with quote

My assumption that you cannot modify the MAP/RPM points is based on the fact that there is no separate value saved for these points, only the MAP values; therefore the controller cannot know that these have been changed. Just because you can define a table with more rows and columns does not mean the controller can accept them.

Talk to Bob at MEFIBurn and verify this.

Charles
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Trash



Joined: 06 Aug 2011
Posts: 7

PostPosted: Thu Aug 18, 2011 12:23 pm    Post subject: Reply with quote

Bob doesn't know either regarding the larger table or changing the row/column values.

He said it interpolates in between cells and off the top and out the side of the table for low MAP/high rpm situations. I haven't been able to fully verify that yet.

Others have explained it this way:

"If this MEFI stuff (that I have not used myself) is anything like the GM and Ford stuff that I have seen, then it will take the last known value and run with it. So if you have PW of 10ms at 5200rpm and 100kPa, then go to 5500, but still at 100kPa, it will keep using the 10ms value until the kPa changes...it which case it will then move to whatever cell intersects the highest RPM value and actual kPa.

Think of the "cell trace" feature of many software packages, where a bouncing ball or highlighted cell moves around and following the current operating location...when you fall off the table somewhere, it just sits at that location in one axis direction, and follows the other axis as long as there is resolution to do so."

So I really don't know what the system does but both of the previous explanations seem plausible.

My current table has rpm points starting at 600 and stepping to 800, 1000, 1200, 1600 etc. in 400 rpm increments up to 5200. Map columns are 40, 60, 80, 90, and 100 kPa. Total table is 14 rows and 5 columns. I under stand from our previous conversations that by increasing the number of rows and columns it would not work with the current memory address locations. I haven't tried it yet but have a table built that I might just for kicks.

What I would like to do is keep the same table size, 14 x 5, and even keep the same MAP values while changing the RPM increments from say 400 to 475 rpm increments.

So the RPM rows would be 600, 800, 1000, 1200, 1675, 2150, 2625, 3100, 3575, 4050, 4525, 5000, 5475, 5950.

This way I could have a BPW value for the ECM to look up during higher rpm events while keeping the total table size the same, thus preventing any memory address issues.

I guess I'm out in uncharted waters on this. I'll try a few of the new tables and see how things go.
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cbernhardt



Joined: 18 Apr 2008
Posts: 64

PostPosted: Fri Aug 19, 2011 1:04 am    Post subject: Reply with quote

When the tune is written to or read from the controller only a fixed number of bytes are written/read. Theoretically you could define a MAP/RPM/BPW table that would be larger than the entire memory block that is written, so that is one reason I believe it will not work.

Another reason is that there are no user defined values that define the table limits in relation to the BPW table. The only MEFI4 table I can find that allows changing the table row/column values is the BLM table and even that one does not allow changing the number of rows/columns. I don't think this feature is available in the MEFI1.

Charles
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