IMHO svdo can support piggyback since it only works in closed loop +- 3500rpm..

Elaboration below

Piggyback will be able to work in open loop

Yup..closed loop means intake air is metered,fuel is calculated to satisfy ratio,combustion then checked (O2 sensor) to determine the incomplete combustion then fed back to ecu to regulate the fuel ratio again.Closed loop works to produce best economy and tries to obtain a complete combustion.Problem is its hard to keep the feedback loop constantly updating at higher rpms so it reverts to open loop around +-3500 rpm..when in open loop,the O2 sensors feedback is not taken into consideration.In this range it is possible for piggyback to work since it wouldnt revert back to the O2 sensors feedback.

Just my 2cents

This is a closed loop operation:



Lets assume
X(s) is the MAP/MAF sensor
G(s) is the ECU
H(s) is the O2 sensor
Y(s) is the output (or amount of fuel injected into combustion chamber to satisfy AFR)

When in open loop, H(s) is not in effect,so theres no feebback loop (from this diagram,negative feedback) so you can tap the piggyback between X(s) and G(s) and set it to work only during open loop operation


*waiting for sleepwalker to do the corrections *

This post has been edited by ryan_hustler: May 6 2009, 08:42 PM

As far as i know,the only way of reverting to factory setting is to disconnect the car battery...unless theres a limp mode im not aware of..

btw,you cant re-tune the factory ecu..

Drex,you sure the stock microP can be reflashed? Usually for mass manufacturing,the microP will be the type which can only be programmed once to save cost..like a dvd-r and dvd-rw..

y kenot?

yup can function above 3krpm without any problems..means can la

depends if got 02 sensor..i think the mmc 1.6 above is closed loop,1.3 and 1.5 is open loop..means no feedback sensor

02 sensor is what makes a system closed loop as there is feedback and correction..refer to my block diagram. The open loop part comes at a higher rpm as its not possible to correct the afr.(maybe some hi-tech stand alone can do so,im not too sure)
i think 1.6 got,but this im not too sure as well..but with 02 sensor is definitely closed loop

what ecu and wiring harness are you using? mmc 1.3,1.5 designed to run in open loop only what