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- Jun 18, 2001
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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:
Inside the limp mode menu, you can see the option to enable the fallback table:
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:
This is the table Eric pre-loaded for me:
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:
There's a tab along the top called "Histogram/Table generator" Click it.
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:
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...
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:
Inside the limp mode menu, you can see the option to enable the fallback table:
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:
This is the table Eric pre-loaded for me:
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:
There's a tab along the top called "Histogram/Table generator" Click it.
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:
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...
