Results 1 to 15 of 15

Backpressure opinions!?!

This is a discussion on Backpressure opinions!?! within the External Engine forums, part of the LSx Technical Help Section category; Alright,so my 00' SS 6spd has Hooker longtube headers,3" Texas X-pipe,NO cats & bullit race mufflers.Under the hood is the ...

  1. #1
    TWISSTED
    Join Date
    Mar 2006
    Location
    SARATOGA,N.Y.
    Age
    42
    Posts
    78

    RED
    00' Camaro SS/6spd

    Backpressure opinions!?!

    Alright,so my 00' SS 6spd has Hooker longtube headers,3" Texas X-pipe,NO cats & bullit race mufflers.Under the hood is the SLP Flowpac system as well.

    Some say there is not enough backpressure while others say that is outdated info so I'm just curious what your input is on the subject?

    HOPEFULLY someone can prove one way or the other?????

    Thanx!

  2. #2
    Senior Member bills98ta's Avatar
    Join Date
    Feb 2007
    Location
    St Thomas, PA
    Posts
    5,047

    White
    1998 Trans Am

    The X pipe, H pipe, and Y pipe all reduce exhaust scavenging. Therefor, I think you have nothing to worry about !!!

  3. #3
    Member danziger's Avatar
    Join Date
    Aug 2006
    Location
    Chesapeake, VA
    Age
    49
    Posts
    570

    Le Mans Blue
    2004 Z16

    You don't need backpressure at all. The less restrictive exhaust may cost you some low-end as it moves the power-band up the RPM range, but you won't lose power...you'll gain it.

  4. #4
    Madeche Vision...soon The Scientist's Avatar
    Join Date
    Feb 2006
    Location
    Galveston, TX
    Age
    38
    Posts
    328

    NBM
    '98 Ram Air Formula

    Excatly what danziger said. You need backpressure at low rpms to produce torque but not at higher rpms.

  5. #5
    UberTapping Friction Pimp Anthracis's Avatar
    Join Date
    Mar 2007
    Location
    Omar's Tittie Taverna & Grill, Deh Rawod
    Posts
    1,447

    18D Cock Diesel
    1999 Z28; 98 SS #2043 RIP

    ditto

  6. #6
    member since may 2000 nhraformula's Avatar
    Join Date
    Dec 2002
    Location
    n/w chicago
    Age
    47
    Posts
    6,933

    black
    2000 nhra edition formula

    backpressure=myth
    look at race cars, they have dumps off the headers.
    2000 nhra edition formula
    a few bolt ons, 379 rwhp
    11.96 @113.25

  7. #7
    Senior Member mrr23's Avatar
    Join Date
    Jul 2005
    Location
    orlando, fl
    Posts
    7,134

    dark bowling green
    2000 corvette

    Quote Originally Posted by nhraformula View Post
    backpressure=myth
    look at race cars, they have dumps off the headers.

    backpressure = myth is correct. the correct terminology that should be used is velocity.

    race cars - can't compare that to a street car. there's a balance needed. pipe sizing to exhaust output/rpm.

    you want to achieve zero backpressure. problem is you can't do that for all rpms. the larger the pipe, the less backpressure. but too large costs you in the lower rpms due to slow velocity.

    i'll use the ole' garen hose example:

    barely turn the faucet on to where the water slowly comes out (low rpms). this means not enough water to fill the entire area of the hose. now, pinch the hose. the water starts coming out faster and shoot further out. (this is where the whole backpressure myth confuses people). now, we have set the hose diameter to meet the requirements of the output of water.

    now, turn the water on full blast (high rpms). water is coming out quickly and lots of it. try and pinch it off. the hose swells up. even though the water is shooting further away, there is less volume coming out now. that is what's called backpressure. the point where the area of the hose cannot support the volume of water coming out.

    so, where is the happy medium, when it comes to street cars? here's little guide:

    single = dual
    2.50" ---- 2.00"
    3.00" ---- 2.25"
    3.50" ---- 2.50"

    not only is rpms a factor, but also horsepower output. for most 400-500hp and up to 6500 rpms, a single 3.5", or dual 2.5" will be a good medium with the dual having a better overall curve.

  8. #8
    member since may 2000 nhraformula's Avatar
    Join Date
    Dec 2002
    Location
    n/w chicago
    Age
    47
    Posts
    6,933

    black
    2000 nhra edition formula

    if your stalled as i, you dont worry about low end rpm.

  9. #9
    Senior Member mrr23's Avatar
    Join Date
    Jul 2005
    Location
    orlando, fl
    Posts
    7,134

    dark bowling green
    2000 corvette

    Quote Originally Posted by nhraformula View Post
    if your stalled as i, you dont worry about low end rpm.
    i do, because when i'm driving around, i'm under the stall speed of 3400. you are focused on racing. there's more to a streetcar than just racing.

  10. #10
    2004 HEAD/CAM CTS-V 9t8z28's Avatar
    Join Date
    Oct 2006
    Location
    doylestown, Pa
    Posts
    6,818

    SILVER
    2004 CTS-V

    Quote Originally Posted by mrr23 View Post
    i do, because when i'm driving around, i'm under the stall speed of 3400. you are focused on racing. there's more to a streetcar than just racing.
    =+1

  11. #11
    member since may 2000 nhraformula's Avatar
    Join Date
    Dec 2002
    Location
    n/w chicago
    Age
    47
    Posts
    6,933

    black
    2000 nhra edition formula

    Quote Originally Posted by mrr23 View Post
    i do, because when i'm driving around, i'm under the stall speed of 3400. you are focused on racing. there's more to a streetcar than just racing.
    even when not racing, the shift extension of the stall keeps your rpm higher than stock. any low end loss of a some tq shouldnt even be felt.

  12. #12
    Senior Member mrr23's Avatar
    Join Date
    Jul 2005
    Location
    orlando, fl
    Posts
    7,134

    dark bowling green
    2000 corvette

    depends on throttle input and STR of converter. normal driving for me is 3500 rpm shift point that drops to 2000 rpms due to converter.

  13. #13
    Junior Member
    Join Date
    Apr 2007
    Location
    Slidell, la
    Posts
    4
    Here is my expirence with back pressure. I have a 1970 baracuda with a 440 in it. We just got done with the car but the exhaust was on back order so we ran it without the back half of the exhaust for a good while. We were running headers coming down and a 1.5ft long 3.5" wide pipe off of each header. I ran 10.86 with that set-up.

    This car is also a weekend rider too, anyway we started to notice that when we would change the plugs about once a month that oil was coming out of the spark plug holes. Well the exhasut came in and we put it on well when we ran it again my time actually fropped from a 10.86 to a 10.62 and the oil problem stopped.

    Also im an apprentance at a shop doing SVT training and i see the same oil problem in cobra's that try and run off road pipes in place of the cats and havetaken off the mufflers,

    I mean im not to sure if back pressure has anything to do with it but from what im guessing back pressure has something to do with it

  14. #14
    Senior Member mrr23's Avatar
    Join Date
    Jul 2005
    Location
    orlando, fl
    Posts
    7,134

    dark bowling green
    2000 corvette

    the mufflers provided a scavenging affect. they helped to pull the exhaust out, causing a vacuum behind the leading pulse. this helps pull the next one out.

  15. #15
    TWISSTED
    Join Date
    Mar 2006
    Location
    SARATOGA,N.Y.
    Age
    42
    Posts
    78

    RED
    00' Camaro SS/6spd

    Guys...I appreciate all the helpfull input!!!

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Looking at 98 T/A need opinions
    By nochey in forum Firebird / WS6
    Replies: 41
    Last Post: 06-23-2010, 09:30 PM
  2. exhaust vs backpressure
    By Madcity T/A in forum External Engine
    Replies: 11
    Last Post: 08-04-2007, 10:33 AM
  3. Opinions about SLP
    By secondgearscratch in forum Camaro / SS
    Replies: 88
    Last Post: 03-02-2007, 06:10 AM
  4. looking for opinions on a car
    By Oldladykiller in forum Firebird / WS6
    Replies: 8
    Last Post: 02-23-2007, 01:15 PM
  5. backpressure
    By 99-SS-Conv in forum General Help
    Replies: 43
    Last Post: 01-21-2007, 08:40 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •