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Old 07-07-2012, 04:49 PM   #1
akuhner
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Join Date: Oct 1999
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Location: Westport, CT
Vehicle:
2000 Impreza 2.5 RS
SCCA Rally Cross Car

Default Saab 92X Aero not making power - Cobb AP v2

Hi - I have a 2005 Saab 92x Aero with an AP v2 that made 235hp at the wheels when I got it, but now seems to make a good 25% less, but runs fine overall. Here's what it has:
  • Custom dyno tune for the AP done by Agile Auto
  • Originally dynoed at just under that what a stock STi does on the same dyno. It's a very safe map, reliability/longevity was primary to making power.
  • Cobb Accessport v2
  • Turbo XS stealthback exhaust system (basically a full 3" turbo back exhaust that tapers to 2.5" at the axleback). Includes a highflow cat
  • STi axleback
  • Helix up-pipe
  • Perrin panel filter
  • Prodrive boost control solenoid
  • Snorkus removed and replaced with OEM elbow

Here's a log from a 3rd gear pull:
https://docs.google.com/spreadsheet/...JSUZSOWc#gid=0

At first I thought it had a boost leak, but I'm not sure.

Any thoughts?

Thanks,

Alex
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Old 07-08-2012, 09:57 AM   #2
Cobb Tuning
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Location: Austin, DFW, Portland, SOCAL
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Quote:
Originally Posted by akuhner View Post
Hi - I have a 2005 Saab 92x Aero with an AP v2 that made 235hp at the wheels when I got it, but now seems to make a good 25% less, but runs fine overall. Here's what it has:
  • Custom dyno tune for the AP done by Agile Auto
  • Originally dynoed at just under that what a stock STi does on the same dyno. It's a very safe map, reliability/longevity was primary to making power.
  • Cobb Accessport v2
  • Turbo XS stealthback exhaust system (basically a full 3" turbo back exhaust that tapers to 2.5" at the axleback). Includes a highflow cat
  • STi axleback
  • Helix up-pipe
  • Perrin panel filter
  • Prodrive boost control solenoid
  • Snorkus removed and replaced with OEM elbow

Here's a log from a 3rd gear pull:
https://docs.google.com/spreadsheet/...JSUZSOWc#gid=0

At first I thought it had a boost leak, but I'm not sure.

Any thoughts?

Thanks,

Alex
How are you determining that it is making 25% less power? I would contact your tuner as they know exactly how the map is supposed to respond.

Bill
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Old 07-08-2012, 01:43 PM   #3
akuhner
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Member#: 462
Join Date: Oct 1999
Chapter/Region: NESIC
Location: Westport, CT
Vehicle:
2000 Impreza 2.5 RS
SCCA Rally Cross Car

Default

Quote:
Originally Posted by Cobb Tuning View Post
How are you determining that it is making 25% less power?
Totally unscientifically via butt dyno, which I only believe because it was a sudden drop. One day it felt really fast above 3k rpm, so much so that in normal driving I tried to keep it under that, then the next day it felt gutless.

I'll contact the tuner, but it was the original owner who worked with them and they are too far to travel to. For the moment I'm just glad there's nothing glaringly wrong in the data.

Thanks,

Alex
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Old 07-08-2012, 02:48 PM   #4
Black94Snake
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Vehicle:
1994 5.8T Cobra
565rwhp @ 10psi

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Your DAM is only 4 when it should be 16! You are losing out on 75% of your knock correction advance max table. When was the last time you had the battery disconnected? When was the last time the ecu was reset, or the ecu was reflashed?
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Old 07-08-2012, 07:55 PM   #5
Cobb Tuning
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Quote:
Originally Posted by akuhner View Post
Totally unscientifically via butt dyno, which I only believe because it was a sudden drop. One day it felt really fast above 3k rpm, so much so that in normal driving I tried to keep it under that, then the next day it felt gutless.

I'll contact the tuner, but it was the original owner who worked with them and they are too far to travel to. For the moment I'm just glad there's nothing glaringly wrong in the data.

Thanks,

Alex
Still a good idea to contact the tuner. They will know how the car was running it when it left the shop and if there were any outstanding issues (mechanical or otherwise).

Looking at the log, as Black94Snake stated, the DAM is down to 4, which is extremely low. Only persistent perceived knock will drop the DAM that low, assuming the tuner did not set the initial DAM to 4, but that would be highly unusual. Your long-term fuel trims (A/F Learning 1) look fine, but if it hasn't been very long since you've reflashed a map, reset the ECU, or disconnected the car's battery, then they may have not populated accurately yet (give it about a tank of gas of normal driving). Fueling problems are a common source of severe knock of turbo Subarus, generally boiling down to post-MAF intake leaks, issues with the MAF sensor, or issues with the front o2. No evidence that this is the case yet, however, so give it some driving and avoid any heavy throttle runs for now. You can also experience false knock where something is rattling in the engine bay (such as a heatshield) that the knock sensor is picking up.

Bill
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Old 07-08-2012, 08:53 PM   #6
akuhner
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Member#: 462
Join Date: Oct 1999
Chapter/Region: NESIC
Location: Westport, CT
Vehicle:
2000 Impreza 2.5 RS
SCCA Rally Cross Car

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Bill - There actually is something rattling in the engine bay sometimes, sounds like a heat shield, but I've been too lazy to get to it. I had no idea that a small rattle could affect the ECU, but that makes sense.

I have not reset anything since I bought the car in January, and it came with the map loaded and everything working. The seller is a close friend who knew what he was doing, so I'm sure there were no known mechanical issues, but I'll contact Agile anyway. I'll also reset the ECU via the AP, and take it easy for a tank of gas (which takes me about 2 weeks as I generally drive it 8 miles a day, to and from the train ).

Thanks,

Alex
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Old 07-09-2012, 08:54 AM   #7
Cobb Tuning
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Quote:
Originally Posted by akuhner View Post
Bill - There actually is something rattling in the engine bay sometimes, sounds like a heat shield, but I've been too lazy to get to it. I had no idea that a small rattle could affect the ECU, but that makes sense.

I have not reset anything since I bought the car in January, and it came with the map loaded and everything working. The seller is a close friend who knew what he was doing, so I'm sure there were no known mechanical issues, but I'll contact Agile anyway. I'll also reset the ECU via the AP, and take it easy for a tank of gas (which takes me about 2 weeks as I generally drive it 8 miles a day, to and from the train ).

Thanks,

Alex
I would definitely isolate the location of that rattle if you can and fix it. It could be the entire cause of the DAM dropping. When you do find it and fix it, reset the ECU (if the DAM is not at 16) and then you can verify whether that was the problem or not.

Bill
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Old 09-11-2012, 10:37 PM   #8
akuhner
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Join Date: Oct 1999
Chapter/Region: NESIC
Location: Westport, CT
Vehicle:
2000 Impreza 2.5 RS
SCCA Rally Cross Car

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Turns out the cat was falling apart, and bits of it were cutting exhaust flow and causing the rattle. Here's another pull with a new cat and a retune from The Shop CT:

https://docs.google.com/spreadsheet/...Wc&pli=1#gid=1

And here's the dyno chart:
http://www.pbase.com/akuhner/image/145995786

It feels smoother, but less powerful - I did ask for a "very safe" tune, so that's what I get.
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