Retune accesport tune

After watching, Aftermarket Injector Scaling - Subaru, I have a serious problem. I have a 2003 wrx hybrid (2.5 block). 3 inch intake, 1050 ID injectors, ect. It was etuned with a accesport. I had wanted to just modify this tune but trying to access it with romraider, I couldn't open the map. Maybe I missed something? If not I was going to re-tune starting from factory tune, removing accessport. From the webinar this sounds impossible unless I go back to stock and tune injectors and then MAF, ect.

Yeah, this is a common issue with Cobb Accessport tunes. Since AP stores maps in a proprietary format, you won’t be able to open your current tune in RomRaider unless you have the original ROM before flashing it.

If you just want to tweak the tune, you’ll need Cobb’s Accesstuner software. But if you're switching to open-source tuning, you’ll have to unmarry the Accessport, revert to stock, and start fresh. That means:

1. Reverting to stock with the AP.
2. Pulling the stock ROM and saving it.
3. Scaling injectors first, then MAF, then everything else in RomRaider or ECUFlash.

Thanks for the reply. Going back to stock just isn't a option. I'd have to buy a new 2.2 engine. Change out headers, up pipe, turbo, exhaust and redo all air intake plumbing to put air filter back in? Getting the E-tune I sent a list of upgrades and got back a general tune to start with, and so on. Any other ideas?

I get that going back to stock isn’t an option with all the changes you've made. Since you already have an E-tune, the best way to proceed would be to use Cobb’s Accesstuner to modify your existing map. You can fine-tune fuel tables, injector scaling, and other parameters without having to redo everything.

If you’re really set on moving to open-source, you'd need to find a tuner who can pull your current tune from the Accessport and convert it to a compatible ROM for RomRaider or ECUFlash, but that's not always possible or easy to find.

If your tune is pretty close to what you need, it might be easier to stick with Accesstuner and just make some tweaks from there.

I'm set on open-source tuning. From this info I'm confused as to how the E-tuner was able to tune it. Leading me to believe it's a low quality tune?

After some though I may have been overthinking my situation. If I go back to stock tune and consider changing injectors would change fuel for all main engine systems. All I need is stock MAF sensor to have correct air flow for ecu calculations? If that's true. MAF sensor in stock diameter intake with smooth flow is all I need? Air filter would only cause resistance of flow but not change volume of air, meaning without it I'd be okay? Thanks

If your E-tuner was able to work with it, they likely used Cobb’s Accesstuner, which is why you can’t open the map in RomRaider. That doesn’t necessarily mean it was a low-quality tune, but without seeing the actual calibration, it’s hard to say.

You’re on the right track with the MAF. If you go back to a stock tune and stock-diameter intake, the ECU will have the correct MAF scaling for airflow calculations. The key is making sure the intake piping is smooth, with no turbulence or leaks.

As for the air filter, you're correct that it mainly adds resistance, not changes in air volume. Running without it technically wouldn't affect airflow readings much, but it’s a bad idea long-term—you’ll be pulling in dirt and debris, which can mess up the MAF sensor and engine over time.

If you're set on open-source, getting a clean ROM and properly scaling your injectors and MAF should be your next steps.