ECUGN and the fallback MAP table

Turbo6inKY

Short Guy
One of the banes of our existence after converting to a speed-density system is a MAP line blowing off, which makes the ECM think you've only got 100kpa in the manifold, and then it pulls fuel, and blam, your engine is toast.

On many systems, tuners will create a "shelf" in the VE map so that if you're at a certain TPS or above a certain RPM and the KPA registers 100, it floods the engine. Effective, but crude.

The ECGN (and MS3 based things in general) have a better way: the fall back MAP table.

Now, if you've got your ECUGN, Eric probably already enabled this feature for you. If he didn't, talk to him BEFORE mucking with it. He probably had a reason. But if you're typical, he enabled this feature and loaded the MAP table.

What is a fallback MAP table? It's a table that contains MAP values that *should* be experienced at certain TPS and RPM points. If the MAP sensor fails or the MAP reading is wacky, the ECU will switch to this MAP table and the car will keep running. I can verify this functionality works. At Barber Motorsports Park last weekend, I kept melting my MAP line shut (exhaust leak in the engine bay). The car would stumble, then switch to the fallback table and keep going.

This post is how to take your log data and make that fallback map table look like what your engine is actually doing. So let's go.

First, the dialog to enable it is under the CAN-Bus/Testmodes menu, Limp mode:

1534114566985.png


Inside the limp mode menu, you can see the option to enable the fallback table:

1534114601725.png


You don't have to change anything here, just showing you where it's turned on. Just below the Limp mode item in CAN-Bus menu is the MAP table itself:

1534114636644.png


This is the table Eric pre-loaded for me:

1534114702465.png


Now, as it turns out, my engine behaves bit differently than this map at low RPM ranges. So, when that MAP line melted shut, it ran great at WOT, but when I lifted, it would stall. Annoying.

So what we're going to do is use a datalog of an autocross run to generate a histogram of value I can plug in to this table to make it more closely match what the car actually does. This will require an additional piece of software: MegaLogViewer. It's available for a small fee from EFI Analytics. It's HIGHLY recommended. Those of you with Powerloggers should already have a copy, it's way more powerful than PLC when it comes to charting stuff, as you'll see in a moment.

At any rate, make sure the car is healthy, and then go flog it while logging the flogging. Then load it into Megalog viewer:

1534114887059.png


There's a tab along the top called "Histogram/Table generator" Click it.

1534114931987.png


Now, in the TunerStudio Fallback table, RPM is the X axis, TPS is the Y axis, and the Z axis (the value int he boxes) is going to be the expected MAP value. It'll fill in the table for you:

1534115024971.png


You'll also see a chart at the bottom. If you position the cursor in the chart and move it around, you'll see where in the histogram the car was operating. It's really cool.

So, what you can do here is take these values and transpose them into the fallback MAP table. If there are gaps in your histogram, it just means the car never got to that spot in the map. No big deal.

Now, back to tuner studio. We can see that at the low end of the table, the MAP readings in the tunerstudio table above are way lower than what the car actually experienced. The upper end is pretty close, so that explains why at part and low throttle, it'd die, but it kept screaming at WOT. Now, the readings at 501 RPM? That column is from when I cranked it while starting it. Don't use those. You can probably leave the 0 RPM column in tunerstudio alone.

But 800 and 1000? That's idle. Let's fix that.

To be continued...
 

Attachments

Turbo6inKY

Short Guy
Continued...

So at 800 RPM and 15% TPS, the engine actually read a MAP of 50.55. So at 1000 and 0 in the fallback table, let's change it. Select the cell and hit '=':

View attachment 326258

When you hit = you'll get a popup:


So at 800 RPM and 15% TPS, the engine actually read a MAP of 50.55. So at 1000 and 0 in the fallback table, let's change it. Select the cell and hit '=':

1534115639110.png


Now, we don't have data for 1000RPM and 100% throttle, but we do up to 35%, so repeat this procedure with the numbers you have.

Moving on to other portions. At 6000RPM and 0% throttle, the fallback table says a MAP of 48. But my log say at 5400 rpm, I was at 92.44. So we'll fix that the same way we fixed the others. Select the cell closes to the X and Y values, and set it. Set the extremes. After you get 6000 RPM at 0%, find the right value for 6000 RPM at 100%. In my case it was 200.86 at 5400.

My table had a lot of data around the 60% throttle point, so I transposed all of that in, too:

1534115964799.png


Compare this to the default table and you can see where I've changed stuff.

If you click the "3D view" box, you'll get a visual representation that can be helpful:

1534116007133.png


So, you can see the dip in the middle of that map. We're going to fix that. Since we've input values we know, we can have the software smooth out the map for us:

Uncheck 3D view, then select the entire map with the mouse, then right click:
1534116075520.png


select "Smooth Cells"

It will then average out the entire map between the edges that you've already filled in.
Go back to the 3D view and you'll see your newly smoothed fallback map table:

1534116140140.png


Burn this to the controller. Voila. You have a fallback MAP table customized to YOUR engine.

Disclaimer: This is HOW to do it. DO NOT COPY MY MAP VALUES INTO YOUR TUNE! Follow the steps and generate valid numbers for YOUR car! If you have any doubts, ask before touching! If you're not comfortable with this or it's over your head, don't mess with it!
 

Reedogg

TB since 1996
Those of you with Powerloggers should already have a copy, it's way more powerful than PLC when it comes to charting stuff, as you'll see in a moment.
Hi Andrew, do you have experience using MagaLogViewer with Powerlogger files? I'm stuck uploading the current tune. Powerlogger logs can be downloaded in csv format that MegaLogViewer can read, but the table generator also needs your current tune. The tune isn't in a format that MegaLogViewer can read. Eric says the tune file can't be converted to anything else.

I'm getting closer to just switching over to ecu-GN...
 

Turbo6inKY

Short Guy
Hi Andrew, do you have experience using MagaLogViewer with Powerlogger files? I'm stuck uploading the current tune. Powerlogger logs can be downloaded in csv format that MegaLogViewer can read, but the table generator also needs your current tune. The tune isn't in a format that MegaLogViewer can read. Eric says the tune file can't be converted to anything else.

I'm getting closer to just switching over to ecu-GN...
Megalogviewer does view Powerlogger files just fine.

But dealing with the table generator and the VE analyzer is a Megasquirt feature, and it requires a Megasquirt tune file so the program has a VE and AFR table to run the analysis against.

So yeah, you're stuck there. Apples and oranges, so to speak. The factory ECM doesn't use a "tune" the same way as a Megasquirt.
 
Top