Just to throw another variable in which I havnt seen mentioned in this thread , when I did the stage 2 Morgan upgrade , it came with an unlocked ECU letting me , and the tuner I used tweak it futher as required.
I suspect , and have never read otherwise, all Morgan staged upgrade ECU's are supplied open.
I have no idea if third party ECU's do this, worth checking before purchase.
Its possible they could load their map then lock it.
Unfortunately MMC Stage upgrades do not guarantee an unlocked ECU. My Stage 1 (Air filter and exhaust) was supplied and fitted by MMC but my ECU was returned locked. It appears luck of the draw whether they left an ECU unlocked.
To pick up on a few other points:
The ECU simply needs to be powered on to apply a reflash so this could be done without the car. For official MMC changes they provide dealers with a file which unlocks the ECU, applies the new map and then relocks the unit. For info several have tried to work out how to unlock an ECU but as far as I know without success.
The definition of Stage varies by the source of the upgrade. The typical definition is Stage 1 is air filter and exhaust, Stage 2 adds higher lift cams (596 being the most common upgrade as they boost power and torque but remain non interference).
Stage 3/4 can refer to higher lift cams, stronger valve springs to raise the rev limit and the 128 cubic inch big bore kit.
