Okay. Starting off with some background. I bought a prelude with a spun rod bearing and I needed to replace the bearing, but there was scoring in the bores so I got it bored out 0.25mm. Got oversize high compression 11:1 pistons, and I want to get stage 1 crower camshafts. Do I need a tune for this? I have an '00 prelude so it is obd2. I live in a CARB state and county so I do need it to pass that stuff. Will the ecu adjust for any differences in the camshaft? Just give me a quick rundown of what I should need.

 

You will absolutely need a tune which means you will have to convert to OBD1 and run an OBD1 ecu. When you have to get smogged you can just swap back to your stock ECU and stay out of VTEC for the duration.

 

What brand of pistons did you get ?
You MUST tune the car once you make the changes that you have outlined... the factory ECU cannot compensate for the increased compression and lift/duration of the camshafts.

 

I have nippon 0.25 oversize 11:1 pistons

 

Sounds like a plan. Any ECU reccomendations?

 

hondata is the best

 

To go deeper on that question, use an ECU that you can get good tuning and support on in your area. Hondata is good software and very widely used, so it is generally a great option. But some guys like Neptune, some like to burn chips each tune, some people want to spend tons of money and go with AEM, Motec, etc as well.

Personally, having used a few different software's on a few different platforms, I really like the Hondata interface, and there are so many tuners and end users that have experience with it, that there is generally always going to be an easy way to find help if you run into an issue. The newest version of S300 has a ton of awesome features as well. Beware of older versions or knock-offs though.