Quote Originally Posted by exist3nce View Post
^ The Haltech Sprint 500 is a good ECU to run... but it is a standalone at the end of the day... which means your car will more than likely have some CEL codes unless you could manage to simulate all the inputs and signals the stock ECU wants to see. Just off the top of my head (since I run the Sprint500 in my Optra), I have codes for injectors and ignition coils, as the stock ECU is totally cut off from those. There are ways to simulate/emulate those signals so the stock ECU thinks its running the injectors/coils but then you will likely run into more codes which take longer for the ECU to recognize such as O2 response related codes.

If you need OBD2 compliance.... what about that Trifecta tuning option that everyone was talking about? Flashed ECUs are the easiest way to maintain OBD2, if the flash has the capabilities to do what you need. Otherwise a piggyback system to intercept and modify signals as they are going in/out of the ECU is the other way... but this can get complicated if no one has done the setup with your particular ECU. Since you are trying to manipulate these signals in just the right manor, a thorough understanding of how both ECUs work, and what they want to see is critical to the setup working properly. You essentially have to trick the stock ECU in such a way that it doesn't know anything has changed lol.

Thats good advice. One of the reasons I am such a VW fan still is the stock ecus can be modified for almost any mods, and stay/modify the obd2 compliance. The whole piggyback, trick tuning is why I haven't dived into a big mod in my aveo. It just seems like such a compromise that should have been left in the 90s at this point. I've used piggybacks and stand alone in the past, but the emissions I have to pass makes it impossible to get what I want/need.

For the OP. I would definitely try the trifecta route. I would probably start with looking for a "Stock" tune that would be close to your set up. Vauxhall has turboed 1.6 liters, so you find one with the same set of sensors you have and that would be a possible base tune to modify from. Although that again is my VW background talking where that stuff is all available.

I am sure any good tuner could build you a tune from scratch as well.