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Complicated exhaust issue (raspy mid-high rpm)

Discussion in 'VF Holden Commodore (2013 - 2017)' started by soag17redline, Oct 30, 2017.

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  1. Oct 30, 2017 #1
    soag17redline

    soag17redline New Member

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    Hey guys complicated question here but I'll just list the mod then the problem..

    I have hurricane mild steel 1 3/4 headers, 100 cell cats joined up to my existing stock bimodal system on my vf2 redline with otr and tune.. sounds good for the most part but quite raspy/echoey at mid to high rpm (4-7k).. im guessing its from the smaller diameter of the bimodal exhaust/the baily tip causing the raspiness.. i need to fix that im guessing i need to just replace the stock catback as well?

    Now seeing as my extractors are mild steel should i stick with it or go stainless and should i stick with brand or go with a different catback brand?

    Any advice would be massive as i want a deeper note across the rev range not just low-mid rpm.. cheers
     
    soag17redline, Oct 30, 2017
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  2. Oct 30, 2017 #2
    Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    What you use will depend on how the cats were fitted. Do you have a photo of the join where the cat pipes meet the cat back?

    Is it only raspy with the bimodals open?
     
    Not_An_Abba_Fan, Oct 30, 2017
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  3. Oct 30, 2017 #3
    soag17redline

    soag17redline New Member

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    Nah i dont have a picture..

    Yeah with it open, when open the exhaust is very loud which is great until it starts getting raspy.. with it closed the car is pretty quiet which is handy too..


     
    soag17redline, Oct 30, 2017
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  4. Oct 30, 2017 #4
    daves8

    daves8 Active Member

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    Are the hurricane headers ceramic coated?

    For depth of note I would look at either manta or difllipo/ Walkinshaw.

    I went a Manta mild steel cat back as it tends to carbon up a little bit more, giving a slightly deeper dirtier note (my preference)
     
    daves8, Oct 30, 2017
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  5. Oct 30, 2017 #5
    Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    If you want to keep the bimodals and stop the raspiness I would recommend a front section with a muffler. Will make it deeper and quiet with the bimodals closed, but with them open it should give a smoother more defined note.

    The problem with mixing components is that none of them are frequency matched. It will be a bit of a lottery to find parts that go well together. I would fit a whole cat back, but it will probably need modifying depending on how the cats were fitted.
     
    Not_An_Abba_Fan, Oct 30, 2017
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  6. Oct 30, 2017 #6
    soag17redline

    soag17redline New Member

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    Hmmm yeah its a toss up atm whether i get a dpe stainless 2.5 catback to match up and hopefully fix the note or gamble on the cheaper alternative and get a mild steep 2.5 inch hurricane catback and have it all the same and hopefully fix it..
     
    soag17redline, Oct 30, 2017
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  7. Oct 30, 2017 #7
    daves8

    daves8 Active Member

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    I have been told hurricane catbacks drone a little on the VF.

    I would go DPE
     
    daves8, Oct 30, 2017
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  8. Oct 30, 2017 #8
    blackve76

    blackve76 Well-Known Member

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    I had the same with GM motorsport headers and cats with standard system just raspy crap sound as you say up over 4000 revs, added a 3" KPM system and nice deep note.

    I'd just change system, note the 6.3 factory tune has extra fuel in it to get those crap sound crackles and pops, asked my tuner to get rid of them in tune and heaps nicer again
     
    blackve76, Oct 30, 2017
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  9. Oct 30, 2017 #9
    Witto

    Witto New Member

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    I've just fitted HSV Headers and 100 cell cats to my VF1 Calais Sportwagon. But with a R8 mid section and Bimodals, also have the same issue, particularly when going from 1st to 2nd gear under light throttle( valve is constantly open ). I'm thinking its possibly the tips are the issue as well. Sounded fine with standard headers and Cats.
     
    Witto, Oct 30, 2017
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  10. Oct 30, 2017 #10
    duaned

    duaned Active Member

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    What do you mean by raspy / echoey? Wouldnt it sound similar to the standard exhaust only a little louder?
     
    duaned, Oct 30, 2017
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  11. Oct 31, 2017 #11
    monstar

    monstar Naturally as-pirated

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    My exhaust was loud and raspy 4-7 k rpm, I put little hot dogs after the x-pipe, before rear mufflers
     
    monstar, Oct 31, 2017
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  12. Oct 31, 2017 #12
    Witto

    Witto New Member

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    I was surprised how much louder it is by adding headers and cats. As for the "Raspiness / Echo" I would describe it as abit of the old school 308 clappy sound just deeper, if that makes sense?
     
    Witto, Oct 31, 2017
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  13. Oct 31, 2017 #13
    blackve76

    blackve76 Well-Known Member

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    You'd think that and yes louder at idle and nice at low revs but a really unrefined noise high in revs, as if a tinny muffler etc. Changed mine in a week just not a great sound
     
    blackve76, Oct 31, 2017
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  14. Oct 31, 2017 #14
    PeteSS

    PeteSS Active Member

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    Yep, I replaced my 3 inch Pacemaker catback with 2.5 inch Hurricane to quieten it down a bit. Still has the Pacemaker 1 7/8th headers

    it's quieter, but now drones at low revs
     
    PeteSS, Oct 31, 2017
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  15. Oct 31, 2017 #15
    VT&VX

    VT&VX Active Member

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    So it is raspy like a cough just before spewing your dinner or raspy like a European sportscar?
     
    VT&VX, Oct 31, 2017
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  16. Oct 31, 2017 #16
    panhead

    panhead Well-Known Member

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    Doesn't make sense to me as the old school 308's sound absolutely fantastic compared to LS engines.



    .
     
    panhead, Oct 31, 2017
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  17. Oct 31, 2017 #17
    VS 5.0

    VS 5.0 Well-Known Member

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    That is the key aspect I miss about my VS.
     
    VS 5.0, Oct 31, 2017
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  18. Oct 31, 2017 #18
    Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    No cats, carby and intake all make a huge difference to exhaust note.
     
    Not_An_Abba_Fan, Oct 31, 2017
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  19. Oct 31, 2017 #19
    soag17redline

    soag17redline New Member

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    Rippa input guys thanks!

    Yeah i haven't heard back from the guys i went through to get a price on catback but c&a autofashion reckon about 2k for stainless steel 2.5 inch catback retaining bimodal and should fix the note.. leaning that way at the moment
     
    soag17redline, Oct 31, 2017
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  20. Oct 31, 2017 #20
    panhead

    panhead Well-Known Member

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    Even with cats an injected 304 sounds great.

    This is my 1995 VS.







    .
     
    panhead, Oct 31, 2017
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