Thread: 3" vs 2.5" header & exhaust

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  1. #1
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    Default 3" vs 2.5" header & exhaust

    Does anyone have any input on 1 7/8 headers w/3" cats and exhaust vs 1 3/4 headers w/2.5 cats and exhaust. I'm sure with full throttle 3" would be better but what about all around driving. Would 3" lose low end torque. I am looking at my next upgrade.

  2. #2
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    Default Re: 3" vs 2.5" header & exhaust

    With as much tq these cars have you wont notice a low end loss with 3". Take the cats off for cooler sills. Best bet would be to do 3" headers and a catless cat back exhaust. If you feel cats are best for you and your set up, get some high flow cats.


  3. #3
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    Default Re: 3" vs 2.5" header & exhaust

    What advantage would there be with no cats?

  4. #4
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    Default Re: 3" vs 2.5" header & exhaust

    A slight hp gain, cooler side sills, and a viper sounding exhaust. The stock exhaust with headers and cats sounds like a sewing machine. Does not fit the viper persona at all.


  5. #5
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    Default Re: 3" vs 2.5" header & exhaust

    knowing your final goals will also help in the decision

  6. #6
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    Default Re: 3" vs 2.5" header & exhaust

    What Plum said. What's the objective?

    More sound? Bigger is better.

    More performance? That's a little trickier. Bigger is better but only if the engine is designed for bigger. Specifically the camshaft.

  7. #7
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    Default Re: 3" vs 2.5" header & exhaust

    Who makes 1 7/8" headers? Either way, go with a full 3" EXHAUST and no cats for better sound and cooler side sills.

  8. #8
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    Default Re: 3" vs 2.5" header & exhaust

    Quote Originally Posted by alpha85 View Post
    What advantage would there be with no cats?
    I also read that no cats creates an exhaust smell inside the car??? Does this apply to Gen I and Gen II? The Gen II exhaust runs out the back. I was thinking of running no cats with Corsa and stock manifolds on a Gen II (advise from Viper Days in Savannah GA) but I would not want to smell like a tailpipe when I got out! Any input??

  9. #9
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    Default Re: 3" vs 2.5" header & exhaust

    Should be only minimal smell inside if any. I only have minimal but I believe I have an exhaust leak at one of my band clamps.

  10. #10
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    Default Re: 3" vs 2.5" header & exhaust

    Quote Originally Posted by alpha85 View Post
    Does anyone have any input on 1 7/8 headers w/3" cats and exhaust vs 1 3/4 headers w/2.5 cats and exhaust. I'm sure with full throttle 3" would be better but what about all around driving. Would 3" lose low end torque. I am looking at my next upgrade.
    Your sig says 'enthusiast'........... is it a Ram SRT? I am truly amazed by all the good answers.........but I feel unable to answer accurately because you did not mention the Year-Model-Mods-Planned Mods ! Only HHI asked and qualified his reply. And Plum mentioned goals as well......

    THE YEAR MATTERS ! It all matters, and matters a LOT.
    Last edited by JonB; 11-07-2009 at 08:25 PM.

  11. #11
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    Default Re: 3" vs 2.5" header & exhaust

    Quote Originally Posted by JonB - PartsRack View Post
    Your sig says 'enthusiast'........... is it a Ram SRT?
    I agree, they are also missing out the advangage that this club has to offer if he actually has a Viper.

  12. #12
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    Default Re: 3" vs 2.5" header & exhaust

    Quote Originally Posted by HHI VIPER View Post
    I also read that no cats creates an exhaust smell inside the car??? Does this apply to Gen I and Gen II? The Gen II exhaust runs out the back. I was thinking of running no cats with Corsa and stock manifolds on a Gen II (advise from Viper Days in Savannah GA) but I would not want to smell like a tailpipe when I got out! Any input??
    hhi v

    even with rear exhaust, you will get exhaust smell inside the car, i think more in an rt than in a gts, though this is only conjecture based on my rt. ride around with the top on and rear glass out, or just top on and windows down and sniff

    the aerodynamics of the car causes this "reverse flow". ever notice how dusty your bumper gets just below the licences plate i think i remember jonb talking about squished bugs on the rear bumper after high speed runs

    if you are bothered by smell, hi flows, and even they smell noticeably more than stock cats

  13. #13
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    Default Re: 3" vs 2.5" header & exhaust

    Mainly street some track. I would like to stay naturally aspirated.

  14. #14
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    Default Re: 3" vs 2.5" header & exhaust

    Hennessey, B&B

  15. #15
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    Default Re: 3" vs 2.5" header & exhaust

    Gen 3, Alum fly wheel, 355 gears

  16. #16
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    Default Re: 3" vs 2.5" header & exhaust

    I have a exhaust smell with cats

  17. #17
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    Default Re: 3" vs 2.5" header & exhaust

    I have a 05 Gen 3, Alum fly wheel,355 gears

  18. #18
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    Default Re: 3" vs 2.5" header & exhaust

    Any suggestions?

  19. #19
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    Default Re: 3" vs 2.5" header & exhaust

    ............

  20. #20
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    Default Re: 3" vs 2.5" header & exhaust

    Quote Originally Posted by alpha85 View Post
    Hennessey, B&B
    what are you referring to?

  21. #21
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    Default Re: 3" vs 2.5" header & exhaust

    What do you mean?

  22. #22
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    Default Re: 3" vs 2.5" header & exhaust

    So how do you like the 3.55 gears? Too short?

  23. #23
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    Default Re: 3" vs 2.5" header & exhaust

    I know this thread is old but the info was never supplied so ...

    All 4 stroke engines work better (at all speeds and rpms) with headers and no exhaust, even a lawnmower. Mileage, torque and hp are all increased with headers and no exhaust.

    Viper headers are generally made in 1 5/8" and 1 3/4" tube sizes. There are burns collector headers, stepped headers (notmally the best choice for stock levels of perfomance) and "pickled" Belanger headers which are also excellent for stock power levels.

    For supercharged and Nitrous Oxide powerlevels the largest headers are the best. The pickled Belangers are an excellent header, but restrictive for power adders and the pickles can be torched out for better perfromance.

    Corsa exhaust uses sound cacnellation technology to "tune" and quiet the 'bad' sounds from the exhaust with no baffles or dimples or any other restriction to the exhaust flows in the 3" tubing.

    Your car smells of gas? Sounds like you Cats are plugged? Perhops your rear oxy sensors have triggered an extra rich condition to "protect" you Cats? What is your fuel mileage? My highly modified, lowered compression GTS gets 20mpg US.

    Ted

  24. #24
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    Default Re: 3" vs 2.5" header & exhaust

    Back "in the day" a 340 engine came from the factory with No Cats and 2.5" exhaust. That was the largest size made. GM used 2.25" on most of their cars because it was much cheaper.

    488ci and Viper engines are basically a 360HP engine with racing heads built out of aluminium and much more refined. Obviously a 2.5" exhaust system is too restrictive. 2.5" exhaust was used for 275hp so 3" is a must for a HIGH PERFORMANCE engine.

  25. #25
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    Default Re: 3" vs 2.5" header & exhaust

    Good post Ted. I've read posts about slower times with the larger exhausts on these cars, but can't for the life of me, imagine that dual 3" is too much exhaust for a big 488...even a stock one.

  26. #26
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    Default Re: 3" vs 2.5" header & exhaust

    Thanks,

    On a 2 stroke an exhaust is needed for performance. Remove any of the exhaust excepting muffler and the engine slows considerably. BUT ...

    On a 4 stroke engine pipe is needed to take the exhaust away from the head and valves. Headers use a collector to help scavenge/suck exhuast gases from other cylinders resulting an increase if power. Racing old style cars (70 440 Dusters etc.) as much as 10 car lengths (100hp) could be gained by removing stock type exhaust systems. Although I read that torque was decreased I certainly didn't notice any loss of power. An equalizer tube (x tube) between cylinder banks also increases performance on a V8 but that doesn't seem to help on the V10 engine and when used (Gen2) is for exhaust sound quality.

    Ted

  27. #27
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    Default Re: 3" vs 2.5" header & exhaust

    06 Coupe with no cats, and no smell, except when I fill up with race fuel, then it smells gooooooood!

  28. #28
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    Default Re: 3" vs 2.5" header & exhaust

    Quote Originally Posted by alpha85 View Post
    Mainly street some track. I would like to stay naturally aspirated.
    Had a conversation with Lou Belanger yesterday (If you have not experienced this it is something you should do at least once before you die) and he swears up and down - and has for years - that Vipers are faster with a 2.5" exhaust after his headers rather than a 3". He also admits that the 2.5" over a 3" is much quieter (thus their GenIV cat-back systems being 2.5").

  29. #29
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    Default Re: 3" vs 2.5" header & exhaust

    Just finished installing Belangers on my 2001. I already had R/T's and Corsas, all 3". The only 2.5" section that was replaced was the factory turnout which I replaced with the supplied Belanger 3" turnout. With the full 3" system, the only thing I've noticed so far (no dyno #'s) is a deeper tone at idle, louder at medium and WOT, and the "seat of the pants" feel that the motor winds up faster.

  30. #30
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    Default Re: 3" vs 2.5" header & exhaust

    I bought the B&B 1 7/8 headers, took forever to get, and then cut out the cats and most of the corsa exhaust. The corsa exhaust tubes actually cracked around the welds. I went 3" pipe all the way out. The car opened up so much more power then with the cats, its like having a new car! The noise level isnt too bad when your in the car. When its just running it sounds awesome, but when Im going down the road people seem to freak out because its so loud when I pass them or just step on the gas. Im thinking I need to get rid of the back corsa and put in an X pipe.













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