Originally Posted by JP@SI
FYI - the reason the XEDE piggyback unit cannot control or change the rev limiter is because these functions are hardset in the DME. There aren't any wires that you have to cut to get into the RPM system, it's "built-in". Nor can you undo any speed governors.
There's also another function called electronic throttle function (you can actually make it take off hard and pull instant, versus delayed). Sometimes manufacturers use this advantage to "make or kill power" (i.e. butt dyno). There are cars like Porsche (and BMW) that don't open at 100%... etc. There are other things here to take into account, but again, ALL DME functions.
At which point, you might be thinking, why not just do everything through a DME? Again, just FYI. Certain parameters just NEED to be done via DME.
P.S. This post was meant for informational purposes, not towards the pros and cons of a piggyback unit or DME functions.
We have successfully raised rev limiters with the Xede. This is because the Xede is capable of driving the coils and injectors directly if configured appropriately. This is what makes it a bit different from other piggy-backs.
The main reason we have opted to be as non-evasive as possible has to do with warranty and trace-ability concerns. Our goal, first and foremost, was to make the Xede completely undectable by the DME or anyone monitoring the DME. However, if we were to ever run into issues such as E-throttle bottlenecks, we will find a way to get around it. It just hasn't happened. It seems as if modern computers are getting easier, not harder, to be manipulated if the necessary measures are taken.
About half of our business is ECU reflashing (Subaru, Evo, etc,.). The other half is XEDE tuning. Either one can be a complete engine control solution. It's up to the user to determine what his constraints and needs are.