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The 3xMAP/MAF tables

Hi All,

So as part of my ECU discovery I had to find out what these tables do.

I haven't nailed this down 100%, but I think I have a "good enough" level of understanding.

Currently you might see these tables called something like:
MAP Mass Air Flow Scaling #1
MAP Mass Air Flow Scaling #2
MAP Mass Air Flow Scaling #3

Well this is not really correct. I will explain what these tables actually do.

When the ECU calculates Load it uses a complex algorithm based upon the current MAF voltage AND these 3 tables.

Remember "Load" is the amount of "air" ingested per cylinder, per intake stroke.

#1 is Hot Interpolated
#2 is Cold Interpolated
#3 is Interpolated AFTER #1 and #2 have been interpolated - I am not really sure how #3 is interpolated in, but I don't think its that important yet..

This is what I think should appear in the evo10base.xml:

Code:

<scaling name="Loadify" units="%" toexpr="(x*10/512)*10/32" frexpr="(x*32/10)*512/10" format="%.1f" min="0" max="300" inc="1" storagetype="uint16" endian="big"/>

<table name="MAP based Load Calc #1 - Hot/Interpolated" category="Fuel" type="3D" level="2" swapxy="true" scaling="Loadify">

        <table name="MAP" type="X Axis" elements="19" scaling="JDMMAPpsi"/>

        <table name="RPM" type="Y Axis" elements="19" scaling="RPM"/>

</table>



<table name="MAP based Load Calc #2 - Cold/Interpolated" category="Fuel" type="3D" level="2" swapxy="true" scaling="Loadify">

        <table name="MAP" type="X Axis" elements="19" scaling="JDMMAPpsi"/>

        <table name="RPM" type="Y Axis" elements="19" scaling="RPM"/>

</table>



<table name="MAP based Load Calc #3" category="Fuel" type="3D" level="2" swapxy="true" scaling="Loadify">

        <table name="MAP" type="X Axis" elements="19" scaling="JDMMAPpsi"/>

        <table name="RPM" type="Y Axis" elements="19" scaling="RPM"/>

</table>

So this means that these 3 tables actually output a Load number based upon psi/rpm.. So it's ALSO a VE table...

On to how these tables are actually used.

Basically the ECU chooses the MIDDLE value from the following 3xMAP_interpolated_with_0, 3xMAP and MAF_per_cyl

Now the MAF above is a "per cylinder, per stroke" calculated number from the MAF Scaling tables (not directly the same number)

Now because 3xMAP_interpolated_with_0 is always going to be LESS than 3xMAP then the above REALLY means "the ECU chooses the LOWEST value from the either 3xMAP or MAF"

https://img529.imageshack.us/img529/382/3xmap.png

Excuse the small resolution, and the big jumps - Later I might get a full pull with fewer items being logged...

You can see how the Load value follows the lowest value from MAP or MAF.

Ok so what does this mean? You know how some of you are chasing your tails with the Load dropping around peak boost/peak torque?

Well think about it - when the turbo psi levels off there is a sudden and quick reduction of air being sucked into the air intake. This means the MAF value drops just slightly, which means the final Load Number will also reduce.

Also these tables are ECT/IAT/BARO compensated...

I will update this post when more information comes to hand...

Cheers
D.

Ah yes, it's all coming together, lol :)

Good post, was a good read, when I have a car again I am going to start messing with ECU stuff, being an electrical/computer engineer I probably should, lol.

Honestly though, it makes sense :)

Do you have the "JDMMAPpsi" scaling?

- Bryan

Quote:

Originally Posted by GST Motorsports (Post 8653142)

Do you have the "JDMMAPpsi" scaling?

- Bryan

I am curious, why do we call it JDMMAP and not just MAPpsi?

Quote:

Originally Posted by murlo26 (Post 8653145)

I am curious, why do we call it JDMMAP and not just MAPpsi?

No idea, looks like tephra is using a custom scaling for something...

FYI, I posted this before but the Ralliart uses totally different numbers in these tables then the Evo 10.

It had me scratching my head a bit when I swapped in the AEM intake and BBX lite on my 2010 RA and the car ran like crap, would run really weird low load and would trip codes and such when going WOT.

Moving over the Evo 10 numbers cured it all.

Now it makes more sense to me if these are acting like VE tables.

- Bryan

Tephra might be working on the Omni 4 bar I sent him, perhaps he has that in already not sure if he got it yet, I sent it to Jon @ HB to ship it to him since he was shipping him other stuff too.

If he is playing with the omni 4 bar, i would be happy :) THen I can run moah boost.

Tephra, any reason to call it JDMmap?

Quote:

Originally Posted by GST Motorsports (Post 8653142)

Do you have the "JDMMAPpsi" scaling?

Code:

<scaling name="JDMMAPpsi" units="psig" toexpr="((x/4)*0.19347)-14.5" frexpr="((x+14.5)/0.19347)*4" format="%.2f" min="-15" max="35" inc="0.05" storagetype="uint16" endian="big"/>

No reason - just a CT9A-ism!

Code:

<scaling name="StockXMAP in kPa" units="StockXMAP in kPa" toexpr="((x*2556/3800)+0.5) / 2" frexpr="((x*2)-0.5)*3800/2556" format="%.2f" min="-15" max="35" inc="0.05" storagetype="uint16" endian="big"/>

<scaling name="StockXMAP in psig" units="StockXMAP in psig" toexpr="((x/4)*0.19347)-14.5" frexpr="((x+14.5)/0.19347)*4" format="%.2f" min="-15" max="35" inc="0.05" storagetype="uint16" endian="big"/>

I have renamed it to "StockXMAP in psig"... Bit more consistency :)

Quote:

Originally Posted by GST Motorsports (Post 8653153)

Now it makes more sense to me if these are acting like VE tables.

Yep I think it does!

On Boba's car I bumped these tables up 10%, for the 2.2L - that seemed to have made things a bit better. Although I need to log the individuals to see how they compare.

hey Mr T got it in evo10base but greyed out . . . definition for my rom u have ?

Great work tephra! I've always been a little puzzled by this. It makes sense that the engine would react this way, but there was a disconnect between whats in the tables and what ends up in the logs. Thanks!

The relationships here when thinking about psi-based boost control a blowing my mind a little right now :) throttle + rpm = psi; psi + rpm = load. if you're using the factory load-based boost control, isn't there a circular relationship between throttle and psi? throttle + rpm = load; psi + rpm=load. throttle implies psi. You seem to lose that with psi-based boost control, right? And while it opens the loop, that should allow for more flexibility? eureka!

Any more updates?

If this is the cause for the load dip post spool, I'd love to hear more about it (and how to make it stop)!

Also, why do you think only some cars are seeing it? MAF scaling perhaps?

I think its how quick you spool the turbo up...

too quick and when the gate finally opens there is a really short period where the turbo sux less air in...

thats what I think is happening anyways :|

I like my quick spooling turbo...

Quote:

Originally Posted by tephra

these 3 tables actually output a Load number based upon psi/rpm.. So it's ALSO a VE table...

This is awesome and troublesome at the same time. So ultimately we'll need to rescale 'StockXMAP in kPa' and 'StockXMAP in psig' for the 4-bar to work (with these tables at least) and then hack orig values back in, just like changing MAP16bit scaling and then re-importing the human-readable/scaled values when moving an SD evo8/9 from the JDM3.3/EvoX map sensor to the omni 4-bar.

precisely...

When my 4bar gets here it will be one of the first things I test (i've already done the xml) :)