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Boost Tapers Below Target Threshold, Any Input?


Zymos
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I recently got an Accessport V3 and flashed the Cobb OTS Stage 1 93 Octane tune onto my 2005 LGT (only mod is an Invidia Q300 catback, otherwise stock). I've driven ~200 miles with the flash and decided to run a few datalogs to make sure everything was operating as it should. When looking at the logs I see that I'm reaching peak boost (15psi +/- 0.8), but I'm tapering all the way down to ~11psi when I'm supposed to be only tapering to 13psi +/- 0.8psi. It makes me think that it could be a boost leak, but I would think if that were the case then I wouldn't be reaching peak boost and maintaining the ~15psi to ~13psi as my RPM increases. I'm somewhat at a loss for ideas currently :confused: and it shouldn't be an elevation issue since I live in MA (elevation above sea level is 400').

 

But based on my limited knowledge the rest of my logs look alright. There is -1.4 fine knock learn at certain RPMs, but according to Cobb's Subaru Datalogging Guide that's in the normal range at WOT. I'll see if that changes on my next fill up, as my last tank was from a cheaper gas station since that's what was available (still 93 octane and 10% ethanol content).

 

If anyone has any input on the boost issue and/or how the rest of my logs look I would greatly appreciate it!

2nd Gear.csv

3rd Gear.csv

2nd(7k) to 3rd (5.7k).csv

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I wouldn't call that a boost issue. Pretty good, really about as good as you can expect from an OTS tune. You wanna go from really good to perfect, get a custom tune (e-tune or dyno tune) with a 3-port boost controller.
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I plan on doing an e-tune this summer (I'm thinking Torqued Performance or Cryotune) once I get an intake and catless up-pipe, but figured Cobb's Stage 1 OTS map would hold me over for the time being. I was just a bit confused why it's tapering down so low in comparison to Cobb's numbers, but hey I'm still enjoying the bump in power and the smoothness that came with it over stock
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I plan on doing an e-tune this summer (I'm thinking Torqued Performance or Cryotune) once I get an intake and catless up-pipe, but figured Cobb's Stage 1 OTS map would hold me over for the time being. I was just a bit confused why it's tapering down so low in comparison to Cobb's numbers, but hey I'm still enjoying the bump in power and the smoothness that came with it over stock

 

Just can't let the "so low" go. Your boost is really close to target all the way through. Getting that close with a stock boost controller is nothing to complain about, and expecting any better from an OTS tune is unrealistic.

 

When you get tuned (I like Cryo, obviously), the 3-port boost controller is money well spent.

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I'm thinking Invidia or Cobb on the up pipe and going to be doing the banjo filter bolt soon as the weather is finally starting to become decent

 

I advise against solid up-pipes. I have personal experience of the Invidia causing leaking, and I have complaints about their sensor bung as well. I hesitate to criticize any Cobb product, but I think it runs the risk of the same problem as any solid UP.

 

Your best bang for the buck by far is a low-mileage used UP from any year of STi. You can score one for like $60-70 on NASIOC. OEM quality, flex section, and won't attract the eye of an emissions inspector.

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I'll keep my eye out for one, I really appreciate the suggestion. I know the Grimspeed one also has a flex pipe so if I can't find an STI one near me I'll look up some reviews
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