Stand alone XEDE
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From: Danville/Blackhawk, California
Stand alone XEDE
Hi guys,
In case, for some bizarre reason, you feel that you need stand-alone control over all engine control parameters, there are a few things that you can do to acheive this with your XEDE.
As far as fuel control goes, the XEDE currently intercepts the MAF sensor signal, modifies it, and sends it along its way to the ECU. This is standard for an interceptor-based (or piggy-back) computer.
Wanna get rid of that MAF and run a MAP sensor? Uh..okay, no problem.
On the XEDE harness, there are three terminals for adding an external 3-bar MAP sensor. They are for 12v, GND and MAP signal. Simply hook up a 3 Bar MAP sensor to it. Now, go to your MAF table and convert it over to MAP load referencing. In the "Load Variable" section, change MAFin to MAPin.
Go ahead and remove the MAF sensor. Now, the ECU still expect to see a MAF sensor signal. Unlike a 0-5v MAP sensor, the MAF is frequency based. Easy, the XEDE can handle this. In the MAF table, change "Offset" mode to "Absolute" mode. This means that the XEDE will now generate a MAF signal from scratch and not simply modify the original one. So, looking at your fuel table, the Y-axis is not MAP, X-axis is RPM (like usual) and what you are sending to the ECU is a user-defined MAF signal. Just like a stand-alone. Pretty neat, huh?
So that's takes care of fuel. Now on to boost: Well, not much to say here since 99.99% of XEDE users are running boost in "absolute" mode, meaning that the XEDE is generating its own PWM (Pulse Width Modulate) boost solenoid signal and driving the solenoid directly.
And now on to timing: Now, this is the cool stuff. With an ECU reflash, we can flatten out the factory on-boost ignition maps and use the XEDE to build on top of it. By flattening out the ignition maps, we can make on-boost ignition timing completely insensitive to MAF input (which is tweaked to control fuel delivery). And through creative reflashing, we can also define the authority range and sensitivity of the factory knock sensor. More importantly, knock sensor activity can easily be tracked by watching raw advance numbers through the diagnostic port with a simple OBD-II logger. Bingo, game over.
What's neat is that you are still relying on the factory ECU to charge the coils which eliminates the charging and coil failure issues often seen with stand-alone computers. More importantly, the factory knock control system and multi-map logic is still in effect which is far more effective in supressive knock and adapting to different operational conditions than any stand-alone I've used. Also neat is that the factory computer still controls the injectors in full sequential firing mode.
So, why would we want to do all this? Well, we don't. Not until we program in a MAP switchover point to transition from intercept to absolute mode. Otherwise, we'll be running open loop fuel control even at idle and cruise which isn't ideal for emission or fuel economy. Luckily, that code is pretty easy to write. It would also be good idea to have some sort of temperature compensations for fuel since the XEDE's fueling is no longer piggy-backing off of MAF. Fortunately, this shouldn't be too hard to do either.
Mind you, this whole post is just to show that the XEDE has enough flexibility to do just about whatever you want it to. Just because it can, however, doesn't mean it should
Of course, we're always in the process of unlocking new features and functions so down the road, who knows what it will be capable of doing
Cheers,
shiv
In case, for some bizarre reason, you feel that you need stand-alone control over all engine control parameters, there are a few things that you can do to acheive this with your XEDE.
As far as fuel control goes, the XEDE currently intercepts the MAF sensor signal, modifies it, and sends it along its way to the ECU. This is standard for an interceptor-based (or piggy-back) computer.
Wanna get rid of that MAF and run a MAP sensor? Uh..okay, no problem.
On the XEDE harness, there are three terminals for adding an external 3-bar MAP sensor. They are for 12v, GND and MAP signal. Simply hook up a 3 Bar MAP sensor to it. Now, go to your MAF table and convert it over to MAP load referencing. In the "Load Variable" section, change MAFin to MAPin.
Go ahead and remove the MAF sensor. Now, the ECU still expect to see a MAF sensor signal. Unlike a 0-5v MAP sensor, the MAF is frequency based. Easy, the XEDE can handle this. In the MAF table, change "Offset" mode to "Absolute" mode. This means that the XEDE will now generate a MAF signal from scratch and not simply modify the original one. So, looking at your fuel table, the Y-axis is not MAP, X-axis is RPM (like usual) and what you are sending to the ECU is a user-defined MAF signal. Just like a stand-alone. Pretty neat, huh?
So that's takes care of fuel. Now on to boost: Well, not much to say here since 99.99% of XEDE users are running boost in "absolute" mode, meaning that the XEDE is generating its own PWM (Pulse Width Modulate) boost solenoid signal and driving the solenoid directly.
And now on to timing: Now, this is the cool stuff. With an ECU reflash, we can flatten out the factory on-boost ignition maps and use the XEDE to build on top of it. By flattening out the ignition maps, we can make on-boost ignition timing completely insensitive to MAF input (which is tweaked to control fuel delivery). And through creative reflashing, we can also define the authority range and sensitivity of the factory knock sensor. More importantly, knock sensor activity can easily be tracked by watching raw advance numbers through the diagnostic port with a simple OBD-II logger. Bingo, game over.
What's neat is that you are still relying on the factory ECU to charge the coils which eliminates the charging and coil failure issues often seen with stand-alone computers. More importantly, the factory knock control system and multi-map logic is still in effect which is far more effective in supressive knock and adapting to different operational conditions than any stand-alone I've used. Also neat is that the factory computer still controls the injectors in full sequential firing mode.
So, why would we want to do all this? Well, we don't. Not until we program in a MAP switchover point to transition from intercept to absolute mode. Otherwise, we'll be running open loop fuel control even at idle and cruise which isn't ideal for emission or fuel economy. Luckily, that code is pretty easy to write. It would also be good idea to have some sort of temperature compensations for fuel since the XEDE's fueling is no longer piggy-backing off of MAF. Fortunately, this shouldn't be too hard to do either.
Mind you, this whole post is just to show that the XEDE has enough flexibility to do just about whatever you want it to. Just because it can, however, doesn't mean it should
Of course, we're always in the process of unlocking new features and functions so down the road, who knows what it will be capable of doing
Cheers,
shiv
Last edited by shiv@vishnu; Oct 17, 2003 at 04:41 PM.
