Knock on 2009 Legacy GT + stage 1 Cobb tune -     subaru gift, subaru calendar


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Old 08-13-2018, 09:09 AM   #1
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Join Date: Aug 2018
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Default Knock on 2009 Legacy GT + stage 1 Cobb tune

My setup:
2009 Legacy GT 5MT
~59K miles
Bought it Oct 2017 with ~52k miles, bone stock
Always use 93 octane. I stop wherever for gas, but most of the time it's b/w Exxon, QuikTrip, or Walmart/Murphy station.

I just bought an AccessPort (AP3-SUB-003) and flashed the stage 1 93 oct map to my car yesterday. I drove it with that map for the first time this morning from home to work (~5 mi total). The first ~0.5 mi is residential, then ~3.5 mi highway @ 65mph, then 0.5 mi.

I put up the knock sum and fine knock learn. I noticed ~8-16 on knock sum through the first residential part. For the highway part it got up to I think 27 total, then the last portion it got up to 34. Then it reset itself (I came to a full stop for a few seconds, maybe that's why?) I drove up two levels in a parking garage and then backed into a space. When I parked, it was up to 27 again, most of that I believe was when backing up.

Also, I never saw fine knock learn move. It stayed 0.0 the whole time.

I did NOT notice a knocking sound, but I did feel it idle a bit rough (not really rough, but definitely noticeable). Though, I have noticed the same rough idling for months under the stock map, so I'm not sure if it's related to the stage 1 map at all. I've run only 93 oct since I bought it in Oct 2017 with 52k miles. I went ahead and reverted to the stock map b/c I wasn't sure if the knock was normal or not (new to tuning). After I started it up with the stock map again, for a minute or so in park, it dipped to ~500 rpm maybe 3 times, but never stalled.

I mostly have used Exxon and QT and haven't used Walmart in a while, so I'm not sure if it's a bad quality gas issue, though I'm thinking to start only doing Top Tier gas in the future to be sure.

Since, then I've been reading forums and a Cobb knock article on their website, so I do wonder how much is false knock and how much may be of concern. If I flash the stage 1 before going home, then log the data, what should I be paying attention to on the way home? Also, with the 500 rpm dips on the factory map, is that likely just the ECU relearning or something else?
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