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340 headers VF2

Discussion in 'VF Holden Commodore (2013 - 2017)' started by Nico36, Mar 8, 2018.

  1. Nico36

    Nico36 Member

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    Yea just used the HSV cats that came with the headers. There may be but I couldn't imagine it would be much of an increase.
     
  2. Nico36

    Nico36 Member

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    Yes absolutely, considering I paid about 2000 all up for eveything! Considering WP quoted me 7000 for the 375 lol !
     
  3. arronm

    arronm Active Member

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    I have been advised that stock cats are good for under 400rwhp (300rwkw).
     
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  4. monstar

    monstar Naturally as-pirated

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    Yes 2.25" is standard for the HM exit ID.
    Whether you notice the difference depends on the tuning as most tunes are not really customised to the setup. What you notice is the trade-off 90% of the driving time when you want torque but seems less (doughy, laggy) when tuned for the larger diameter to make peak power up top. So to be clear you don't hardly feel 10-20 fwkw (15rwkw) screaming its tits off up top, but you certainly miss the wider torque spread that comes with higher velocity and scavenging low to mid.
    FWIW I've never been an advocate for larger diameter short throw headers on our car, I did some calcs then dyno trials took the choke off using varying diameter (hence tuning velocity) of the stock downpipe just after the header flange: 2.25" is ideal for HP and TQ balance with a (near) stock engine.
    The two tonne wagon (all variants really), gear ratios, V8 and chassis character all responds better to more torque than unproductive screaming HP.
    Unfortunately for most owners (at least on Facebook) there is one number to describe all the detailed facets of engineering and factors affecting state of tune, that being (estimated) peak engine power.
    BTW I posted results of investigation into LS3 pipe lengths and diameters using PipeMax and Engine Analyser Pro somewhere here will link if I can.
    In other words yes there is a trade-off to get more peak power.
     
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  5. 426Cuda

    426Cuda SUBLIME!

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    Thanks Monstar. A view of both curves would be great if you have them?
     
  6. VF_CalaisV

    VF_CalaisV New Member

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    The difference between them is only somewhere between 5 and 10kw. The other power increase to get up to the 340 mark was from using the supercharged airbox. From what I understand there is no tune difference betwen the 317kw and the 340kw its just part swapping. I am slightly porting my clubsport 2.25" headers. You can open it up a bit at the collector maybe about 3mm increase in diameter. Also at the top of the entry to the header runners there are half ground off welds from the flange welding. I am grinding the rest of the internal parts of the weld off to make it smooth at the top of the runners. Should help the flow a little. I will then use a 2.5" dia bend into a set of VFii cats and a 3" out to suit the catback that came with my car. I'll hopefully eventually get a dyno run and give the results.
    Its just hard to find some cheap VFii cats..
     
    Last edited: Jul 17, 2018 at 2:12 PM
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  7. kleanphil

    kleanphil Member

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    I've got a pair for sale , what do you call cheap ?
     
  8. .05

    .05 Member

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    thanks for the info , i wondered the difference in power output between 317,325,340kw headers and engines tune ect
    i will be fitting some pacemaker 5377 headers i think there hsv340kw clones and will be making up some 200cel cats with smooth pipe bends to cats and hsv 2.5 cat back with stock bimodal mufflers and rotafab air box
    its my misses car shes a traffic light bandit so its just for a bit more squirt for her
    when i,m making up the short cat pipes i dont want to fry the computer , damage anything when doing tack welds under the car
    anyone have any advice on what to do , i have always tack welded on older cars with battery connected before and never had a problem
    i don't want to stuff it up or i will be in big trouble
     
  9. VF_CalaisV

    VF_CalaisV New Member

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    Just an update on the size for the smaller collector (VE) version. There is really 3 dimensions to measure:
    1) Pipe inside diameter, this is only a mm or two over 2"
    2) Flange inner step diameter, this is 2,1/4 "
    3) Flange surface(mating to cat flange) inner diameter is 2,1/2"

    I measured the outer diameter of the pipe going into the flange as 60mm
    So when porting the inside of the pipe and step I will go up to about 2,1/8" inner diameter and flare out to the step at 2,1/4"

    It would be interesting to know those dimensions for the so called 2,1/2" 340kW collectors.
     
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  10. 426Cuda

    426Cuda SUBLIME!

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    Aftet having fitted the Roto-Fab CAI, and previously a Gen-f2 2.5" centre section I'm about to book my Motorsport in for a tune at Gentech in Canberra. At the same time, I will have the 340 headers fitted.
    So, my questions are about the cats. I understand the VF2 cats are 400cell? But, it appears they flow quite well up to beyond 300rwkw, which is my upper target. I like the look of the stock cats and would.like to retain them if I can. Has anyone used these with the HSV 340 headers and if so, what were your results? What mods were required to fit them to the HSV headers?
    Any advice appreciated.
    Thanks all.
     
  11. dimetime

    dimetime Active Member

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    i believe the flanges dont line up, i couldnt see you getting around 300rwkws with a otr and any exhaust be it a hsv one or a quality aftermarket system. 400cell cats will be the main restriction, id consider just getting some 200cell cats made up if you are going to muck around with the cats anyway!
     
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  12. lmoengnr

    lmoengnr Well-Known Member

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    Been trying to find out details about the Euro 5 cats on VF2's, read somewhere they are 600 cell cats, but cant confirm it...
    I have big Ballistic cats on the Maloo, same size as factory, in the same position. They flow well!
    Will the 340 headers fit around the oil heat exchanger on the Motorsport?
     
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  13. 3rspecB

    3rspecB Well-Known Member

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    Pic courtesy from Supercoach. He fit 340 R8 headers to his motorsport. From memory he trimmed the header flange to allow more clearance to the heat exchanger.

    downloadfile-6.jpg
     
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  14. lmoengnr

    lmoengnr Well-Known Member

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    Thanks for finding that pic, its very informative!
    I had the Magnum on ramps, so I got underneath, and held up a 325 header without cat.
    It looked like it would be 'really close'...
     
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  15. 426Cuda

    426Cuda SUBLIME!

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    Thanks gents!
    Ok, well if they're 600cpi, they've got to go.
    @dimetime - I'm basing that on the gains I got in my VF Redline (L77 auto), with similar mods. It went from about 205rwkw stock, to about 260 with these mods and tune (inc 200 cell cats). The auto LS3 stock in the MSE seems to be about 245rwkw, so adding 55 should get me near enough to 300, give or take. I'll post up the results.
    @Imoengnr are your cats 200cell? What rwtq & kw did you achieve? I'm assuming it's not cammed...are there any ground clearance issues with the Ballistics?
    @3rspecB yeah, the pic you shared is before any trimming. So they do fit, albeit tight. So, I was going to grind off a couple of MM to allow a bit more clearance.
    Thanks again blokes.
     
  16. 3rspecB

    3rspecB Well-Known Member

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    Yes before trimming. PM supercoach, I think he took pics of the trimmed flange, so you can see the clearance he achieved.
     
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  17. lmoengnr

    lmoengnr Well-Known Member

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    They are 100cpi cats, on Sureflo headers. Same size and position as factory cats, no clearance problems at all.
    Had to get a flange welded to the Maloo catback, to replace the factory swivel joint to mate to the cats.
    With an OTR and tune, it gained 42kw, from 243 to 285, and enough torque to ruin rear tyres and make me spend most of 2013 as a pedestrian...
     
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  18. 426Cuda

    426Cuda SUBLIME!

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    Haha. Naughty, naughty, very naughty.
     
  19. lmoengnr

    lmoengnr Well-Known Member

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    It must be LS3's, it was 4 months this year, driving a stock Magnum... But now my licence has zero points!:D
     

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