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This is a discussion on Newbie needs tuning advice within the New Member Hangout forums, part of the Community - Meet other Enthusiasts category; Hello everyone, I just got a 2008 WRX sedan and wanted some help on tuning. I am looking for mods ...

  1. #1
    Registered User rc_wizard24's Avatar
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    Newbie needs tuning advice

    Hello everyone, I just got a 2008 WRX sedan and wanted some help on tuning. I am looking for mods that are effective and not too expensive. I've already got a K&N cold air intake, perrin light weight crank pulley, and subaru short throw shifter. I am planning on getting a custom 2.5" cat back exhaust system within a couple months. My car has 51,300 miles and is a daily driver. I would like to relatively keep the gas mileage.

    I've had someone tell me about a wideband o2 sensor and wanted more info about them. I know they tell the engine how much fuel to mix with the air. I've also had someone tell me about head work. I am mechanically inclined and have backyard experience, but never done anything that serious.

    Just looking for some tips. Anything is good

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    UnBanned Sinister's Avatar
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    get a 3" turbobaack exhaust and a tune
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    Supporting Member mjboudreaux77's Avatar
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    Not sure why you would get a 2.5 inch cat-back, I think that is what you have now - but even if you went with a larger cat back you will not see any performance gain. The easiest/cheapest performance "real" gain will be to go "stage 2" - you can do it with used parts and stay under $500. When I went stage2 on my 07 WRX, I left the stock muffler in place, and put in a 3inch downpipe to connect from the turbo to the stock muffler. I bought the COBB downpipe new ($600), and the COBB Accessport to load the tune on the car. Since I bought new, this was about $1100 and the install was very easy. The off the shelf COBB stage2 map won't work with that intake you have, so you would not be able to use their map and you would need a tune. People sell used COBB downpipes for $300-$400 all the time, and you can pick up an accessport used for about the same. Lots of people like the Perrin downpipes as well and they are cheaper.

    I don't know much about wideband sensors - but I can't imagine they are necessary until you get much more horsepower than stock.

    One thing... Any downpipe will technically fail EPA emissions since you are changing the stock CAT - but that is the only way to increase power that you will be able to feel.
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    Master Baiter EJ257's Avatar
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    If you're looking for power, get a used turboback exhaust from the classified section on here/Nasioc and a custom reflash from a reputable shop (my last tune was done by MPS in Washington).

    Quote Originally Posted by rc_wizard24
    I've had someone tell me about a wideband o2 sensor and wanted more info about them. I know they tell the engine how much fuel to mix with the air. I've also had someone tell me about head work. I am mechanically inclined and have backyard experience, but never done anything that serious.
    WBO2 is a gauge that tells you AFR readings. They are usually placed in an aftermarket downpipe; some downpipes come with a WBO2 bung, some don't (you'll have to weld one in).

    If you're looking for one, consider Innovate Motorsports or the AEM UEGO.

    If you're not doing your own tuning, I'd recommend other gauges at your modification level.
    2005 WRX STi (Mods | Virtual Dyno)

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    Registered User rc_wizard24's Avatar
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    Quote Originally Posted by mjboudreaux77 View Post
    Not sure why you would get a 2.5 inch cat-back, I think that is what you have now - but even if you went with a larger cat back you will not see any performance gain. The easiest/cheapest performance "real" gain will be to go "stage 2" - you can do it with used parts and stay under $500. When I went stage2 on my 07 WRX, I left the stock muffler in place, and put in a 3inch downpipe to connect from the turbo to the stock muffler. I bought the COBB downpipe new ($600), and the COBB Accessport to load the tune on the car. Since I bought new, this was about $1100 and the install was very easy. The off the shelf COBB stage2 map won't work with that intake you have, so you would not be able to use their map and you would need a tune. People sell used COBB downpipes for $300-$400 all the time, and you can pick up an accessport used for about the same. Lots of people like the Perrin downpipes as well and they are cheaper.

    I don't know much about wideband sensors - but I can't imagine they are necessary until you get much more horsepower than stock.

    One thing... Any downpipe will technically fail EPA emissions since you are changing the stock CAT - but that is the only way to increase power that you will be able to feel.
    I am definitely considering a new perrin up-pipe and down pipe. I'm usually not one to buy used parts. But I would think that stuff is reusable, right? I just like knowing when I buy something, it's in the best possible shape.

    So a "stage 2 package" is basically a down pipe and an ECU tune?

    If I got the Accessport tuner and took it to a reputable shop with a dyno, they should be able to create a custom map?

    I'm not too worried about the emissions cause the county I'm in doesn't require emissions tests but would a down pipe with a high flow cat pass a emissions test if I ever had to take one?

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    Registered User rc_wizard24's Avatar
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    Quote Originally Posted by EJ257 View Post

    If you're not doing your own tuning, I'd recommend other gauges at your modification level.
    No I won't be doing my own tuning, I'm no where that good yet lol. Are you talking about like a boost gauge or oil temp or pressure gauge?

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    Registered User rc_wizard24's Avatar
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    Quote Originally Posted by Sinister View Post
    get a 3" turbobaack exhaust and a tune
    I've had some people tell me to stay with a 2.5" system just to keep some back pressure. Why would you suggest a 3" system?

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    Registered User rc_wizard24's Avatar
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    So I definitely need a tune after some mods then.

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by rc_wizard24
    If I got the Accessport tuner and took it to a reputable shop with a dyno, they should be able to create a custom map?
    If the shop has the software to tune on the AP, yes. Some shops will also tune OpenECU, which saves you the $600 you'd spend on the AP. The guy who tunes at MPS does OpenECU, so instead of AP+tune, you only pay for the tune itself.

    Quote Originally Posted by rc_wizard24
    I've had some people tell me to stay with a 2.5" system just to keep some back pressure. Why would you suggest a 3" system?
    Backpressure isn't wanted on a turbocharged engine. You want as little restriction as possible.
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    Supporting Member mjboudreaux77's Avatar
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    Lots of questions...

    1.) you need some amount of back pressure for some models. The 07 wrx had an issue with a catless turbo-back that caused boost surging (very bad for these cars). The pre-tensioning of the wastegate actually required some pressure to open. I do not know if this is a problem on the 08s - but I wouldn't think so because I don't think you have a TD04 turbo.
    2.) You don't need an up-pipe for your model - total waste of money and the install is challenging (unless you were already planning on putting a new turbo in).
    3.) An aftermarket High Flow Cat'd downpipe will fail emissions "sniffer" tests if the engine is cold when they run the test, otherwise it should pass. You will notice the smell of gas when your car starts cold once you put a new pipe on. However, if you live where they do "visual" checks for OEM CATs - you will fail because even if you go with a High-Flow cat system, you are still down to only 1 (and, your new downpipe will be shiny - brings their eyes right too it.) I am hearing rumors that some states are testing EGT - if that is the case, an aftermarket pipe will always fail because the exhaust is way too hot.
    4.) Yes - stage 2 is a downpipe (or turbo-back exhaust plus a tune)
    5.) For my 07 I bought a new downpipe, and new accessport. I bought a used STI TMIC and a used VF39 turbo. I got lucky and they were fine, but I knew there was a risk when I bought them.

    Do you have a warranty on the car? All of this totally voids that.
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    Registered User rc_wizard24's Avatar
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    Quote Originally Posted by EJ257 View Post
    If the shop has the software to tune on the AP, yes. Some shops will also tune OpenECU, which saves you the $600 you'd spend on the AP. The guy who tunes at MPS does OpenECU, so instead of AP+tune, you only pay for the tune itself.



    Backpressure isn't wanted on a turbocharged engine. You want as little restriction as possible.
    Is open ECU tuning where they just hook up their computer straight through the OBD port in the car?

    So no back pressure to let the turbo spool free?

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    Registered User rc_wizard24's Avatar
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    Quote Originally Posted by mjboudreaux77 View Post
    Lots of questions...

    1.) you need some amount of back pressure for some models. The 07 wrx had an issue with a catless turbo-back that caused boost surging (very bad for these cars). The pre-tensioning of the wastegate actually required some pressure to open. I do not know if this is a problem on the 08s - but I wouldn't think so because I don't think you have a TD04 turbo.
    2.) You don't need an up-pipe for your model - total waste of money and the install is challenging (unless you were already planning on putting a new turbo in).
    3.) An aftermarket High Flow Cat'd downpipe will fail emissions "sniffer" tests if the engine is cold when they run the test, otherwise it should pass. You will notice the smell of gas when your car starts cold once you put a new pipe on. However, if you live where they do "visual" checks for OEM CATs - you will fail because even if you go with a High-Flow cat system, you are still down to only 1 (and, your new downpipe will be shiny - brings their eyes right too it.) I am hearing rumors that some states are testing EGT - if that is the case, an aftermarket pipe will always fail because the exhaust is way too hot.
    4.) Yes - stage 2 is a downpipe (or turbo-back exhaust plus a tune)
    5.) For my 07 I bought a new downpipe, and new accessport. I bought a used STI TMIC and a used VF39 turbo. I got lucky and they were fine, but I knew there was a risk when I bought them.

    Do you have a warranty on the car? All of this totally voids that.
    1. How would I find out what turbo I have in my car?

    2. I was looking at Perrin's up pipe and they show about 10 whp gains with their up pipe. Why do you say up pipes are pointless?

    3. There are no emissions tests at all where I live. But by the time I move I plan on having the exhaust wrapped so they don't see the shiny new down pipe. And, I don't know how it works, but if my car is registered in one state, can another state still emissions test me? I move a lot being in the military.

    No, my warranty is almost up and not really worried about it.

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    Registered User rc_wizard24's Avatar
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    Quote Originally Posted by EJ257 View Post

    Backpressure isn't wanted on a turbocharged engine. You want as little restriction as possible.
    If there is little or no back pressure on the turbo, wouldn't that lead to a possible turbo surge or am I wrong?

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    Supporting Member mjboudreaux77's Avatar
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    1.) I had to google it, but you have a TD04 turbo, not sure if it still has the issue I mentioned about boost surge though since it is a modified version to fit the new intercooler. COBB's stage 2 map notes state that if there is low enough pressure, you will get boost surging for the 08s. Not making a mountain out of a mole hill here... If you are going to use a CAT'd downpipe - you should be fine with any cat-back exhaust. If you go CATless, you will most likely run into issues that you can't tune out.

    EJ257 is right though - all else equal, in an ideal world, back pressure is the worst thing for turbo spool. In fact, that is what is currently holding your turbo back now, and why you would upgrade the exhaust. This is just a downside of the TD04.

    2.) I have no idea why Perrin would say their up-pipe will gain any horsepower for your car. Are you sure you were looking at the 08?

    3.) Only the state that you are registered in will perform inspection services. However, out here on the East coast, people on this web forum are saying they will get tickets in Connecticut and New Jersey for not having the stock mufflers - even though they aren't registered there.
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    Quote Originally Posted by rc_wizard24 View Post
    If there is little or no back pressure on the turbo, wouldn't that lead to a possible turbo surge or am I wrong?
    Technically the turbo itself provides all of the exhaust back pressure you will need. But, a 2.5" exhaust will be just fine.

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