u dont need 6 months.. but AFAIK there are some piggyback that can tap the return signal to the ECU as well .. to trick the ECU that it is running FINE. But most DONT, they just alter the output from the ECU instead of the Input.
WilliamHoo has experience with BOT last time. They add on piggyback were meant to alter fuel injection and advance timing only. when boost boost boost.. CEL (Check Engine LIght) .. will comes ON .. hooray .. that is because there is a torque limiter mapping within the ecu to control the amount of torque being output from the engine, by BOT you successfully increase the amount of torque over 100% (NA) .. the ecu trying to retard it to get it back below 100% but the piggy just ignore it.. hence ECU says something is not right.. CEL
Put it this way.. the build in map have both the high side and the low side.. on stock .. let says the ignition timing.. let says the min is -10 while the max is +10 at 3000rpm at 100% load (just fix the 3000rpm and the 100% load now.. we want to focus on the -10 to +10 now)..
so let says at that RPM speed the ecu are running +5 which works well with the Ron95. (no knocking) .. if the ecu detects more than 6 knocks in a row, it will drop the timing to +4 .. all the way to -10 if require..
So at +5 .. the ecu send out the signal ..
well , the Piggy does not really give an output as mention, instead it ALTER what was sent out.. says +3 in piggy.. so the ECU +5 out .. halfway piggy pickup .. becomes +5+3 = + 8.. eeehahaaa.. u getting more power.. but actually it started to knock .. so the ecu will bring down the timing .. become +4+3 = +7 ... still knock ... become +3+3 = +6... still knock .. bring down further .. become +2+3 = +5 .. (Congrates you are back to square 1)..
The example above is for NORMAL condition.. says now u BOT with piggyback .. DYNO tune for a few hours.. the ecu try to retard the timing to fit the BOT .. let says the range -10 to +10 .. the ecu have readjust itself to run at -8 to compensate the BOT ... but at piggyback u push says +10 to get the most out of it
-8 + 10 = +2 ..
so when initial it start to run .. not fully boosting no issue.. the ecu will even try to get better timing..
but when full boost comes.. the ecu suppose to run it -8 ... but the piggy keep pushing -8 + 10 = +2
so ecu retard to -9 + 10 = +1 .. still knock ..
retard further .. -10 + 10 = 0 .. still knock .. (at this moment .. the ecu runs to the minimum timing -10 already, it cant go further down anymore.. so it turns on the check engine light .. faulty)