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Tacoma Straight Pipes (pulling the cats baby!!)

Discussion in '2nd Gen. Tacomas (2005-2015)' started by Jeffman1991, Oct 4, 2008.

  1. Oct 4, 2008 at 9:24 PM
    #1
    Jeffman1991

    Jeffman1991 [OP] Active Member

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    Standard Profile Black Toolbox, Straight Pipes with Borla Tips, Secondary air filter removal, K&N Air Filter, CB Radio with 4 foot whip, 50 watt PA, two 8 inch JL Subwoofers, Pioneer Headunit, Jensen 400 watt speakers all around. 3 inch lift coming soon.
    I've got a flowmaster muffler with duals on my PreRunner. Its not as loud as Id like so I was thinking of pulling 2 of my cats therefore having straight pipes. Do you think that the sound will sound deeper and more v8ish, Or would it sound weak.
     
  2. Oct 4, 2008 at 9:26 PM
    #2
    tacomaman06

    tacomaman06 Carolina Alliance: Enforcer

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    getting there....
    you can get away with removing the 2 rear cats if you have the v6. it actually sounds pretty deep and has a nice growl to it, especially since you have a flowmaster already.
     
  3. Oct 4, 2008 at 9:47 PM
    #3
    Zombie Runner

    Zombie Runner Are these black helicopters for me?

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    it will def give it more resonance and sound alot better IMO.
     
  4. Oct 4, 2008 at 11:44 PM
    #4
    BulletToothTony

    BulletToothTony Space for rent

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    Whats the easiest way to have this done, just go to a muffler shop and tell them i want them to cut off the back two cat's and thats it?
     
  5. Oct 5, 2008 at 6:02 AM
    #5
    wiscdave

    wiscdave Lets Do It!

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    illegal!! find a buddy or do it yourself. Nobody in their right mind is going to risk their business for that..
     
  6. Oct 5, 2008 at 7:05 AM
    #6
    06BLUEDBLSPORT

    06BLUEDBLSPORT Well-Known Member

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    I have been told that a toyota engine needs back pressure to work so with out the cats the engine will eventually break. That's what I have heard
     
  7. Oct 5, 2008 at 7:40 AM
    #7
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine. Moderator

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    It wont break. The most important thing with exhausts is "scavenging".
    It is a common myth among drag racers and motor-enthusiasts that not enough back pressure in the exhaust will cause a loss of torque. This myth stems from the phenomena associated with exhaust scavenging. A diminished scavenging effect can result from lower velocity exhaust flow when using headers with large primary tubes. Most enthusiasts incorrectly conclude that their restrictive OEM exhaust provided more torque because of the back pressure it creates. The correct reason for the loss in torque is explained below.
    When an engine starts its exhaust stroke, the piston moves up the cylinder bore, decreasing the total chamber volume. At some point during the exhaust stroke the exhaust valve will open. The high pressure exhaust gas escapes into the exhaust header, creating an exhaust pulse. An exhaust pulse is a release of exhaust gas, containing three main parts, a high pressure "head", a medium pressure "body" and a low pressure "tail". The high pressure "head" is created from the huge pressure difference between the exhaust in the combustion chamber and the atmospheric pressure outside of the exhaust system. As the exhaust gases equalize between the combustion chamber and the atmosphere, the difference in pressure decreases and the velocity at which the exhaust is leaving the engine decreases. This forms the medium pressure "body" component of the exhaust pulse. The remaining exhaust gases form the "tail" component. This tail component may initially match in pressure to that of the atmosphere, however, the pressure is further reduced by the siphoning effect created by the momentum of the high and medium pressure components. The end result may be a pressure at the low end of the exhaust pulse that is less than the atmospheric pressure. This creates a greater pressure difference between the intake manifold and the combustion chamber, which increases the velocity in which air is brought into the engine. This increase in intake air velocity leads to an increase in the amount of air in the combustion chamber, which allows the engine to add more fuel and thus make more power.
    Modern naturally aspirated four-stroke engines usually feature valve-overlap where the benefit of exhaust scavenging is further increased by opening the intake valve while the exhaust valve is also open. This overlap helps purge the combustion chamber of any remaining exhaust gas, and may allow a small amount of intake air to escape out the exhaust port.
    The magnitude of the exhaust scavenging effect is a direct function of the velocity of the high and medium pressure components of the exhaust pulse. Performance headers work to increase the exhaust velocity as much as possible. One technique is tuned length primary tubes. This technique attempts to time the occurrence of each exhaust pulse, to occur one after the other in succession while still in the exhaust system. The lower pressure tail of an exhaust pulse then serves to create a greater pressure difference between the high pressure head of the next exhaust pulse, thus increasing the velocity of that exhaust pulse. In V6 and V8 engines where there is more than one exhaust bank, Y-pipes and X-pipes work on the same principle of using the low pressure component of an exhaust pulse to increase the velocity of the next exhaust pulse.
    Great care must be used when selecting the length and diameter of the primary tubes. Tubes that are too large will cause the exhaust gas to expand and slow down, decreasing the scavenging effect. Tubes that are too small will require additional force to expel the exhaust gas from the chamber, causing unneeded labor on the engine and ultimately a loss of power. This is true for all parts of the exhaust system. In competitive environments it's often required to select the header based on the specific application of the engine. Since engines produce more exhaust gas at higher RPMs the header will respond differently across the RPM range. Typically, large primary tubes offer the best gains in power and torque at higher RPMs, while smaller tubes offer the best gains at lower RPMs. Many people who put race headers on their vehicle experience a noticeable low-end torque loss. This is a result of insufficient exhaust gas output at lower RPMs. The exhaust expands once it enters the primary tube and slows down, reducing the scavenging effect. Many automotive mechanics and enthusiasts erroneously conclude the loss in torque was due to a lack of back pressure, when in fact the real cause was the expansion of the exhaust and resulting decrease in velocity. Despite the low-end torque loss, at higher RPMs the engine will produce more power and in race situations, the vehicle should be faster.
    Many headers are also resonance tuned, to utilize the low-pressure reflected wave rarefaction pulse which can help scavenging during valve overlap. This pulse is created in all exhaust systems each time a change in density occurs, such as when exhaust merges into the collector. For clarification, the rarefaction pulse is the technical term for the same process that was described above in the "head, body, tail" description. By tuning the length of the primary tubes, usually by means of resonance tuning, the rarefaction pulse can be timed to coincide with the exact moment valve overlap occurs.
     
  8. Oct 5, 2008 at 9:59 AM
    #8
    Zebra

    Zebra Well-Known Member

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    depends on where you live
     
  9. Oct 5, 2008 at 11:43 AM
    #9
    Black SR5

    Black SR5 Member

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    On my previous car, by me stating that the car was for "offroad" purposes only, they removed the cat and replaced it with a straight pipe. ;)

    was still illegal in my state to not have catbacks for "street legal" vehicles.


    of course when i traded the car in i had to put the cat back on.
     
  10. Oct 11, 2008 at 8:01 PM
    #10
    Jeffman1991

    Jeffman1991 [OP] Active Member

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    I took out my back two cats this weekend. Everything sounds great! Its a bit louder and much deeper. Thanks for the help!
     
  11. May 21, 2009 at 9:59 PM
    #11
    BigJohn12

    BigJohn12 New Member

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    Would you mind posting a video clip of the results? I also have dual flowmaster 40's and i am thinking about taking the cats off this weekend.
     
  12. May 21, 2009 at 11:35 PM
    #12
    S7ICKlVlAN

    S7ICKlVlAN Cpt. Bubbleguts

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    Any additional tuning need to be done to pull this off? Do you need to put in 02 simms or reflash a new tune?
     
  13. May 21, 2009 at 11:45 PM
    #13
    Okkine

    Okkine Well-Known Member

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    Depends where you live. When the cats went kaput on my Dads old Chevy, he just had the shop remove them since it was significantly cheaper than replacing them. But you should definitely check into the local laws before doing it.
     
  14. May 22, 2009 at 11:38 PM
    #14
    Kopland

    Kopland Rocket Scientist

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    Not to sound like a tree hugging hippie, but the cats are there for a reason... *shrug*
     
  15. May 23, 2009 at 12:37 AM
    #15
    tlmotorsport

    tlmotorsport Active Member

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    No, it is a federal law regarding the catalytic converters, some states however do not enforce the law as strict as others.

    Chris4x4: One of the best explanations I've seen short of doing the math yourself, which I did once(and only once and hopefully wont again) :p
     
  16. May 23, 2009 at 5:45 AM
    #16
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine. Moderator

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    Thank you. :)
     
  17. May 23, 2009 at 5:51 AM
    #17
    GT_Taco

    GT_Taco Newbie here

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    Yah I know many states have emissions testing.. in which case you will fail miserably without a cat on there. Some states in addition to the emissions test, have a periodic visual inspection to ensure that your cat is in fact real, installed properly, and functioning correctly. (CA does this) Some people will gut their cat and run a pipe through so it 'looks' like there is a cat there when in fact it is a straight pipe. Just make sure you know the laws where you live. . . .
     
  18. May 23, 2009 at 5:59 AM
    #18
    Brunes

    Brunes abides.

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    There are federal laws regarding the tamper with/modification of emissions/environmental systems. They would need a reason to look, but you can get nailed anywhere in the US if you have messed with the cats, etc.
     
  19. May 23, 2009 at 9:18 AM
    #19
    ClemsonTacoma

    ClemsonTacoma Well-Known Member

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    uuh u sure about that... any shop prettymuch will do illegal things, go ask em' your self. most of my friends have em off and almost all shops will illegaly tint your windows
     
  20. May 23, 2009 at 9:33 AM
    #20
    GT_Taco

    GT_Taco Newbie here

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    I know shops will illegally tint windows, they just wont provide a receipt for the work. I'd be willing to bet a muffler shop would cut them out for you for a price, they just may not provide an itemized receipt for the work they did.
     
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