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2010 XT Limited 4EAT
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1,447 Posts
Discussion Starter · #1 ·
A question that has been on my mind for quite some time while doing all my research: Why does the engine come tuned the way it does from the factory if there is so much more power to be exposed, even with the stock set-up? Is it there to protect the engine? Make it more user friendly to drive?

Looking for anyone who knows the answer, or people much more knowledgeable than me to give opinions!

(Sorry if this is in the wrong area, I was between this and tuning and ultimately chose this)
 

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2005 Forester XT 4eat
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4,581 Posts
It's done mostly for safety. Some very good tuners can extract more power safely, but most things that are done in the tune (boost target increases, timing advance, changing a/f ratio) are pushing it closer to less safe parameters. This does not mean that it is not safe, but it needs to be done carefully and monitored closely. The factory does not have time to individually tune each car, so the factory map is designed with a bigger margin of safety.
 

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Premium Member
2008 Forester X Premium 5MT
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8,064 Posts
The factory map is also there to:

- Accommodate every car that comes off the assembly line
- Accommodate a wide array of drivers and styles
- A wide array of environments.
- A wide range of fuel quality

Sure your tuner may be able to get more power out of your car at a few hundred feet above sea level in a dry state like Arizona, for a driver who likes shifting late on 93 octane.

Will that same tune be good at 7,000 feet in a more humid Colorado for a driver who doesn't like to wind it out and is lucky to find 89 octane in their area?
 

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07 FXT
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828 Posts
the factory also has to worry about emissions and fuel economy, so they make some compromises that the majority of people on these forums would rather not have. The worst is probably the tendency to run lean up until peak torque, and then dump in a bunch of gas. A custom tune will typically run richer at the onset of boost, which will reduce the likelihood of detonation, which should be a safer tune.
 

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2005 Forester XT 5MT
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60 Posts
How about Stage 1 from COBB? It is still a 'general' tune to fit many different cars, is there still a margin of safety.. Has anyone experienced engine failure or reduced life just off stage 1?
 

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2009 2.5xt 6 Speed Swap version 8 6 speed sti trans with r180
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4,150 Posts
Most will agree that Cobb Stg 1 is very generic and doesn't produce the same results for everyone. It's still really rich as well. A pro tune for your car will produce better results and you can have it exactly the way you want. I'm sure many people have experienced failures at just cobb stg 1 as have many people with no tune whatsoever. I don't think that the cobb tune is unsafe in general though.

I myself had my stock engine pushed very hard with a different turbo and it failed. I think it would have failed with just the cobb tune or stock though due to some QA problems Subaru had around that stop sale in 08-09. It probably would have lasted longer though without me pushing on it.
 
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