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Old 09-09-2019, 04:29 AM   #1
Scooby Newbie
Member#: 505930
Join Date: Sep 2019
Chapter/Region: NWIC
Location: Seattle
2018 WRX STi Limited
Crystal White Pearl

Default Tuning required when briefly switching to OEM components on a Stage 2 STi?

Hello everyone,

I bought a 2018 STi Limited from Copart (13k miles). The damage (front left) is minimal and will be fixed as soon as I get the car insured. While I was not able to locate an accessport, the vehicle appears to be Stage 2, and I have pointed out the following modifications:

-COBB SF Intake System + Airbox
-Grimmspeed Electronic Boost Control Solenoid
-IAG Air/Oil Separator
-Invidia Catted Divorced Wastegate Downpipe
-Invidia Q300 Catback Exhaust
-(Interior) AEM Oil Temperature Gauge

The insurance company will not insure the vehicle until I replace the downpipe and air intake system with the OEM parts. I have the intention of putting both aftermarket components back on the vehicle once it is insured. Since the car did not come with an accessport, I believed that it was a possibility that this car was openly tuned without it. Since I need to replace these parts, and the OEM parts will be on only for a short period of time until I get the OK from the insurance, will I cause any engine harm if I leave the car without a tune for this while? Furthermore, will I need to re-tune the vehicle after I put back on the initial (aftermarket) components after swapping the OEM? I intend to purchase an accessport after I get this sorted first.

Thank you for your help.
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Old 09-09-2019, 02:37 PM   #2
Scooby Specialist
Member#: 447898
Join Date: May 2016
Chapter/Region: BAIC
Location: W Sac, CA
2016 WRX (traded)
2019 STI CWP


At the very least, the car should have an AccessPort for a Cobb Stage 2+ OTS map for those modifications. There's a few scenarios that you should consider.. only the 1st being acceptable:
  1. It's entirely possible that the owner reverted the car back to the OEM map and unmarried the Cobb AP after the accident to sell it. The car wasn't driven at all after the accident and no harm came to the engine as a result.
  2. The previous owner had the proper stage 2 map flashed (or custom tune), kept the AP, but didn't revert back to the OEM tune (and didn't unmarry the AP). The ECU will be locked to the stage 2 tune and you won't be able to revert back to stock or modify the tune. You would have to reach out to Cobb, but you may need to end up replacing the ECU in this case. The stock intake won't play nicely with a stage 2 tune that's intended for the Cobb intake (due to MAF scaling)
  3. The previous owner ran those "stage 2" mods on the stock tune (without the AP) and likely did some level of damage to the engine.
Your best bet is to see if you can contact the original owner to get an idea on the state of the engine/tune. If not, see if you can borrow (or buy) an AP and marry it to your ECU. It will let you know if the ECU is already married to another AP.. in which case you're in scenario #2.

Good luck!
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