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Engine Back Pressure

Discussion in 'Powertrain' started by jakejacobson86, Mar 9, 2005.

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    jakejacobson86 New Member

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    Back Pressure

    Hey whats up guys. I just very recently discovered that everyone moved to vvt-i.net as opposed to the old vvti.net! so im excited that i finally caught on! anyways, I own a 99 corolla ce auto. I have a generic stainless steel muffler that a local shop welded on to my stock pipes. Ive heard from a few people that unless I got a full cat-back pipe set up or FI of some sort, then loosing my back-pressure my stock muffler gave would be degrading to my performance. is this true? help is appreciated as Im thinking about buying an OEM muffler for about 130 shipped. thanks.
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    polo708 New Member

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    You don't need back pressure period. Others will post otherwise, im sure of it... but you don't need it.
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    jakejacobson86 New Member

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    so even on my N/A 4 cylinder engine, you're saying i should go with less restrictive piping no matter what? my uncle used to race for ford and he's tuned cars since he was like 15, and he swears that even my 1/4 mile time would be cut down if i still had my stock muffler. i dont mean to put down what you said, but i consider him a pretty reliable source.
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    polo708 New Member

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    Here you go, I dug this up for everyone:

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    Dr Tweak Mad Scientist

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    Let the Doc set this myth straight:

    *edit* Damn, polo708 beat me to it. Oh well this is what I was typing:

    An engine NEVER, under any circumstances, n/a, turbocharged, supercharged doesn't matter NEVER benefits from backpressure.

    So why the saying that you shouldn't go too big or you'll lose backpressure and that will hurt performance?

    By running exhaust piping that is too big, you will loose exhaust velocity. This will cause less power on the low end of the RPM band (less low end torque), however, the engine would still benefit when it gets to the upper RPMS.

    Also note: the problem of losing exhaust velocity does not apply at ALL when you are using a turbocharger. With a turbo you want big piping after the turbo because you already have too much backpressure from the turbine.
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    jakejacobson86 New Member

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    wow. that was freggin awesome. like seriously, it feels like the clouds parted and a bright light shined before me... lol... seriously, thanks for that post polo. Which brings me to my next question. instead of investing in a pricey cat-back setup, would it be benneficial for me to find a shop that will replace my stock piping with say, 2.5" piping? which parts should I get them to replace? sorry if that is a newb q.
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    Dr Tweak Mad Scientist

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    Yeah, but two things to keep in mind: always use Mandrel bends (instead of crush bends that most shops use) and use a high flow catalitic converter.

    If you use crush bends then at the bends the piping will only be like 2" instead of 2.5". Also, that's a little big IMHO, 2" would be closer to the number you want.

    What is it stock? 1.5"?
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    jakejacobson86 New Member

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    sweet, sorry if i come across as inexperianced about this, but well, yeah i am! so if i found a shop that could do exhaust work, just tell them that i want my stock exhaust pipes replaced with mandrel bent 2" piping? where would i come about the high flow cat converter? i really appreciate the help by the way Dr Tweak!
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    Dr Tweak Mad Scientist

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    Yeah, and a decent shop should be able to hook you up with a high flow cat as well. Otherwise you could get one off eBay or whatever.

    My pleasure :)
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    jakejacobson86 New Member

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    aight Dr Tweak, Im off in search for optimal exhaust flow! I have you to thank for the support. Thanks again. you're the bomb.
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    Vamp Gunmetal 2001 Corolla S

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    Stock is 1-7/8".
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    vortex Well-Known Member

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    2.5" is perfect for turbo applications. 2" seems to be sorta crappy. (i've experimented with both)
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    polo708 New Member

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    Yeah, I plan on doing a 2 1/4" custom job when I get back to the states in August.

    1 7/8's seriously?? god thats small, haha.
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    DjFrOsT New Member

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    you know...this post also helped me out alot...WOW...thanks Dr. tweak... :Nworthy

    thats why i love these forums...neebies...(like me)...learn alot...

    thanks!
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    Vamp Gunmetal 2001 Corolla S

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    You think 3" for turbo might be too much?
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    rainbow_star New Member

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    I thought turbo love 3" pipe? :p
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    vortex Well-Known Member

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    hehe i dont think it'll be too much, but ya might have issues routing that big of a pipe around. :) 2.5" was a pain enough for me.
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    Tamago New Member

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    RollaRyder1103 New Member

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    i have a 3" mandrel bent exhaust system...on my 78 280z turbo...that thing sounds like a beast now...it had a 2.5" mandrel when i bought it w/ a stock muffler, but I upgraded the piping and threw on a nice magnaflow muffler w/ 3" inlet and voila, my turbo inline 6 now sounds like a v8. it's also nice my car doesn't require a cat, so absolutely no restrictions from the turbo back.
    [IMG]
    [IMG]
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    CarbonB New Member

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    Good lord that's some large piping.
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    killer2239 Lift at 5700rpm

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    More like good lord thats a beast.
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    dw1986 New Member

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    nice car man :cool:
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    rice cracker VVT-i's Cracker

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    I had some 3" piping on my Thunderbird Turbo Coupe and it sounded awesome. I got many people asking if it had a V8 302 in it when it only had an I4 140ci!
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    alby13 New Member

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    LMAO

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