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Old 01-05-2005, 06:23 PM   #1
aschen
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Default Stock STI EM tuning Question

Well I have always wondered this, and now that I have an sti I will ask it. STI's come from the factory in a relativly high state of tune. My evidence for this fact is that magazines have noted detonation and subaru reflashed all the 2004's. Many companies offer "software: upgrades for stock sti's that claim increased HP tq ect. My question is how is it possible to squeeze more power out of the stock mechanicals when it is already tuned on the edge? Now I am not an expert on tuning and I really only understand the basics of af ratios, timing, boost etc. It seems to me that companies get more performance by tuning more aggressively but still in a safe zone. Are there any parameters you can adjust to make the car safer and more powerfull (say by sacraficing mpg emissions etc).

Thanks,
Aaron
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Old 01-05-2005, 08:50 PM   #2
BigJ04STi
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Aggressive tune does not mean most optimal...

Remember factory tuning needs to keep within the environmental barriers ofthe country which the car is sold...Due to emmissions laws in the US...They would never push the car to it's true limits.

These is some play in the ECU tuning in stock form to create more power with fueling, boost, ignition timing etc...Of course with bolt ons too, you could see some really good power.

Honestly, from what I see and hear...going with a basic Cobb AP stage 1, are gaining some good power and most are even seeing a higher MPG from not running so darn rich.

Hope my newbie knowledge is right...
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Old 01-05-2005, 09:55 PM   #3
aschen
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Your answer does seem reasonable, And it agrees with what I think I have learned about ecus. However, I thought I understood that there are basically 3 parameters to adjust to gain power:

1. Add boost
2. add timing
3. Lean A/F

Each of these I would think would may a more agressive tune and more prone to detonation and damage. for the reasons I said above, I am under the impression that there is almost no room left in the stock ecu as it is on the verge of det stock. Unless some combination of these parameters can yeild more powere with out risking det? For example what if you pull some timeing and add enough boost to gain power. Is this a less det prone tune? i have a stealthback exaust sitting in my garage from my previous car and Im thinking about installing it, but everybody worries me with boost creep issues. I thought mabey Id sell it and get an AP stage 1 instead.
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Old 01-05-2005, 10:19 PM   #4
serendipity
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Many EM gains on stock cars are "area under the curve" type gains. Peak power may not rise much, but boost and torque will come on much sooner, making the car more responsive in daily driving. The factory makes it more linear because that's what people are used to, and people only look at peak power numbers anyway.

It is true that EM basically gains power by being more aggressive, but it's not true that just because the stock car detonates it's already at the limit. There are differing theories, but it seems to me that the stock ECU code is just broken. It tries to advance timing too far, detonates, and then falls back. My car would feel like a different car day to day, depending on where the Ignition Advance Multiplier was at the time. EM makes this more stable and produces more consistent power.
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Old 01-06-2005, 08:59 AM   #5
stanton
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Mr. Ignorance here. I really don't know the subject, but speaking out of logic...

The stock EM in any Subaru is smart/adaptive enough to keep an engine from detonating/knocking/pinging. Even if from "bad gas". Right? Am I missing something? The ECU manages it so you don't even hear it. SO, if a stock STis are/were pinging, maybe the reflash was a detune work-around to a faulty knock sensor design.
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Old 01-06-2005, 09:38 AM   #6
serendipity
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Quote:
Originally Posted by stanton
Mr. Ignorance here. I really don't know the subject, but speaking out of logic...

The stock EM in any Subaru is smart/adaptive enough to keep an engine from detonating/knocking/pinging. Even if from "bad gas". Right? Am I missing something? The ECU manages it so you don't even hear it. SO, if a stock STis are/were pinging, maybe the reflash was a detune work-around to a faulty knock sensor design.

It's just software. They made a mistake in the code or parameters, and the reflash (supposedly) fixed this.

The stock ECU does keep the car from detonating. It does this by bumping the timing up until it detects detonation (which is not really all that bad for short durations and at stock power levels), then it backs off. The problem is that it's too aggressive at bumping the timing up, and then too aggressive in backing off afterwards. This is mostly speculation - I don't think anyone knows exactly what the reflash change was.
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