HomeForumsTechnical – GeneralExhaustMaking some kick ass pipes for 2nd gen commodore

This topic contains 147 replies, has 11 voices, and was last updated by Profile photo of VRSenator065 VRSenator065 4 years, 11 months ago.

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  • #6250
    Profile photo of IJ.
    IJ.
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    Member since: April 2, 2015
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    Use some stiff cardboard, roll it into a cone tape it, cut off one end at the biggest that will fit between the ports, cut the other end so it’s 2″ untape it lay it flat on some sheet and trace then roll the steel up and weld it, done :XD:

    #6252
    Profile photo of vs manta 218
    vs manta 218
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    Yeah that’s much better idea then running a smaller pipe into a bigger pipe that will cause trublance

     

    I have watched a mate build a methanol burning  cr500 exhaust like that, he actually done loaded it then cut it out and made it, but did make custom expansion chamber with different cones pitches and sizes using your method

     

    thanks very much

    #6253
    Profile photo of cava454
    cava454
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    Cones??

    #6254
    Profile photo of vs manta 218
    vs manta 218
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    Yeah big cones

    about 150mm in diameter and connected to a awesome pipe

    #6255
    Profile photo of cava454
    cava454
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    Ok I need photos for what I mean cause I’m confused lol

    #6256
    Profile photo of vs manta 218
    vs manta 218
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    I’m thinking this here has a pretty good angle I’ll try and get my 8 cones about the same as this as the angle seams pretty good

     

    I have no idea what the stuff in it is as I’m not a teenager any more and been over a decade since iv been anywhere near that

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    #6262
    Profile photo of VRSenator065
    VRSenator065
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    • VR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project)

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    You bloody neanderthals, how about you model the cone in 3D CAD then press flat pattern and trace around that  :wacko:

    #6265
    Profile photo of IJ.
    IJ.
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    In the time it takes me to fire up the CAD software I’d have it finished in cardboard…

    #6268
    Profile photo of delcowizzid
    delcowizzid
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    every 1/8th inch larger will move max torque rpm around 500rpm higher .the only reason your torque is allways climbing higher is boost never getting to max boost so it naturally makes more torque all the way over there to the right at redline if it hit full boost at 3000rpm like turbo youde have massive torque around full boost petering off slowly and be able to use headers to shift it left or right to where you want it.go too big and recovering rpm on gear shifts gets real hard.if its just gonna live up on a 7000+rpm limiter doing skids and never bog down you could use 2″ if it was street ide go small to get all the torque i could before boost takes over to make HP.you only need to look at the turbo cars to see exhaust tube diameter isnt too important with boost even when theres 40+psi of exhaust pressure at the exhaust valve youll be at way lower  exhaust pressure at the valve and strugglig to not blow all your charge clean out the exhaust.theres probably more gain in changing mufflers than headers even the 3.5 inch cats will be same cell count and same outside diameter so wont gain anything measurable over the 3″ in 3″ out

    #6269
    Profile photo of vs manta 218
    vs manta 218
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    The cats are 4 inch OD where 3 inch cats are 3.5 od so the count will be different

     

    Also on turbo cars there is a very valad reason why they keep there primary runners and cross over pipes small

     

    Its to keep air speed up to spool faster, even there cross over pipes can be down at less then 2 inch on 700 hp turbo set ups witch you wouldnt dare do on a SC car but after the turbo is a different story sometimes goin as large as 5 inch and if they really want power they will dump it just a few hundred mm after the turbo

    I dont really agree there is more power or better results to be had changing mufflers over headers, i know people with 2 inch pipes on 355 engines and they clearly got gains

    • This reply was modified 5 years, 3 months ago by Profile photo of vs manta 218 vs manta 218.
    #6272
    Profile photo of pir4te
    pir4te
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    Hi mate, I use a header design program and the Bat Computer spat this out for you:

    Lots of practical knowledge from Vizard and Meaux behind the calcs, made a huge difference to my build  ;-)

    • This reply was modified 5 years, 3 months ago by Profile photo of pir4te pir4te.

    Naturally as-pirated, all-motor.

    #6274
    Profile photo of vs manta 218
    vs manta 218
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    That awesome

     

    So by that my 2 inch pipes some between 20-23 inches long and 3.5 collector is actually right on the money and for top end hp could actually be a smigion bigger

     

    Ill have a good look at that when i finish work and read the collectir design and cone size it has there

     

    Thanks very much pir4te

    #6301
    Profile photo of vs manta 218
    vs manta 218
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    Pir4te

     

    Iv just had a good read of that and i must say that is the best info iv read or recieved on this site I think

     

    Carnt thank you enough

     

    What is the harmonics down the bottom ??

     

    I take it the primary harmonics is extractor length 20 inchs

     

    But the collector tail pipe? Is that saying my best results would be with a 14 inch exhaust system ??

    #6305
    Profile photo of VRSenator065
    VRSenator065
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    Lots of practical knowledge from Vizard and Meaux behind the calcs, made a huge difference to my build

     

    Is that David Vizard of mini tuner fame?  If it is that guy really knows his stuff…

    #6306
    Profile photo of pir4te
    pir4te
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    Pir4te Iv just had a good read of that and i must say that is the best info iv read or recieved on this site I think Carnt thank you enough

    Cheers mate, good to be on a site where new info is appreciated.

    <span style=”line-height: 1.5;”>

    </span>What is the harmonics down the bottom ??

    Harmonic frequency (length) at which the exhaust pulse from your motor develops a resonance, first harmonic is full wavelength. Useful to determine the best place to put devices such as pressure wave termination box, expansion point, muffler or like x-pipe – best place for x-pipe torque is second harmonic, for power up front at the third.

    <span style=”line-height: 1.5;”>

    </span>I take it the primary harmonics is extractor length 20 inchs But the collector tail pipe? Is that saying my best results would be with a 14 inch exhaust system ??

    No you have a choice of four ideal lengths although only two or three are practical when including collector, cats, muffler – 14, 29, 58 and 116″ measured from the end of secondaries at merge (start of collector).

    Naturally as-pirated, all-motor.

    #6307
    Profile photo of pir4te
    pir4te
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    Lots of practical knowledge from Vizard and Meaux behind the calcs, made a huge difference to my build

    Is that David Vizard of mini tuner fame? If it is that guy really knows his stuff…

    Yeah, good stuff really, more than pure theory has written world records, wrote several books and regular editorial contributor to professional magazines.

    Naturally as-pirated, all-motor.

    #6308
    Profile photo of VRSenator065
    VRSenator065
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    Sure was, have a couple of his books in my library at home from years back.  He was one of the guys back in the day actually putting theory behind what he was suggesting.  Very cool guy.

    #6309
    Profile photo of cava454
    cava454
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    Is this theory not based on all out power?

    Im with delco wizard. On the street. Better average is best. ESP in a car with a manual Gearbox.

    #6310
    Profile photo of vs manta 218
    vs manta 218
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    If you had my combo cava and where building extractors for it what size would you go ?

     

    Iv iv never heard of this David guy, I’ll have to look him up

    #6312
    Profile photo of cava454
    cava454
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    well my mate ran 9’s with 1 3/4 off the shelf pacies.

     

    Its not like these are costing a fortune so not sure what I’d do. If they were 2-3k I’d be staying what I had.

     

    if you had an auto with 4500 converter I’d say don’t worry about te downlow power your going to sacrifice.

    • This reply was modified 5 years, 3 months ago by Profile photo of cava454 cava454.
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