Why the Xede is better than a full ECU replacement!

Installing a piggyback auxiliary computer between the factory ECU and its sensors and actuators provides bone-stock engine management during no-boost engine operations.  Aside from its legality advantages, the stock EMS with factory calibration has the overwhelming advantage that it provides unbeatable drivability on the street in ordinary driving.  Expert calibration engineers at the car companies spend many months or even years optimizing the calibrations for best power, efficiency, and drivability within the engine’s stock operating envelope—an effort justifiable in part because it’s required to meet emissions standards and in part because the cost will be leveraged across many thousands of vehicles.  The best supertuners in the country cannot do as well because they don’t have the time, clever though they be.  Even if you have the skills, you don’t have the time either.  Nor do you have the freezing arctic, baking desert, or high-altitude test facilities to get the calibration perfect under all conditions—resulting in expensive tuner cars with aftermarket engine management systems that refuse to cold-start the first time you drive from the palm trees of L.A. to a Sierra Nevada ski area.

A piggyback computer is designed to create a false virtual reality around the stock EMS during boost conditions, within which the stock EMS can be tricked into delivering turbo-conversion or higher boost turbo engine management.  The laptop user interface of a modern piggyback is typically very similar to that of a standalone aftermarket EMS, complete with fuel, timing, boost, and various other calibration maps, though timing and fuel numbers usually represent offsets from stock engine management.

How a piggyback/interceptor actually manages to retard the timing, for example, of selected boost-RPM points depends on the piggyback design and the way it’s wired into the stock EMS.  On a modern multi-coil engine equipped with sophisticated EMS diagnostics that are constantly looking for subtle changes in the electronic “ring” of an ignition circuit in order to detect the tell-tale signs of misfire, a piggyback might instead intercept and delay the signal from the crank position sensor such that stock EMS ignition event automatically becomes late in relation to the real crankshaft position.

With respect to engine management functions of ignition timing, fueling, boost controls, diagnostics, and a variety of engine variables influencing performance and durability for the extreme of street performance and anything less than full competition, the piggy cannot be seriously challenged by a full stand alone computer.  The key reason is the piggy uses the enormous programming experience of the OEM computer for all off-boost functions. 

The stock OEM programming has passed the various certification requirements set out by various state and federal organizations, else it would not be there in the first place.  The ability of the piggy to use this OEM programming permits the piggy to pass the same state and federal requirements while still offering precise engine management under boosted operation for your wildest performance objectives.  This is not even remotely possible with the stand alone engine management systems, for all the reasons outlined above.

Selecting an injector is a basic key to providing adequate fueling under boosted conditions.  Suppose the objective is 360 bhp, then one injector in the Miata must fuel 360/4 bhp worth of fuel, or 90 bhp.  To select the injector, multiply this number by .55 lbs of fuel per bhp and get 49.5 lbs/hr.  This number needs to be given a margin of safety on duty cycle, so divide by .85, for a 15% margin.  Or; 49.5/.85 = 58 lbs/hr.  To convert to the other standard of CC/min, multiply by 11, for 11 x 58 = 638 cc/min.

Dyno Charts

XEDE Downloads

*For Optimal Results - Dyno tuning is recommended