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.

Viewing 20 posts - 1 through 20 (of 149 total)
  • Author
    Posts
  • #6101
    Profile photo of vs manta 218
    vs manta 218
    Participant
    Member since: March 2, 2015
    Posts: 796
    Supporter

    Ok so I’m making some custom extractors for my blowen 355

     

    iv got a DIY kit from difilippo, iv got a holden engine flanges in 1 3/4 that I will port out

     

    if I can I’m goin to put some slits in 2 inch pipes and taper them down slightly so they clear the extractor bolts and run full 2 inch 4 Into 1 with a 3.5 inch collector

     

    so my questions are, I’m running LS ecu with 2 O2 sensors, how far down the pipes should these be and does it matter witch way they face ( upside down or right way up)

    Iv got a wide band and that goes at the collector

    I have EGT, how close to head ports should this be ?

     

    And also Iv got 2 3.5 inch moroso spiral mufflers that I’ll be fitting straight after the 3.5 inch cats along side the gear box, are there any pros and cons of having these mufflers before the x pipe ??

     

    After these it will tapper down to 3 inch where it will connect to my existing exhaust pictured below

     

    ??

    #6129
    Profile photo of VRSenator065
    VRSenator065
    Participant
    • Adelaide SA
    • VR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project)

    • View build HERE
    Member since: February 17, 2015
    Posts: 5 696
    Supporter

    Ok deleted the other thread mate, play on :good:

    #6130
    Profile photo of VRSenator065
    VRSenator065
    Participant
    • Adelaide SA
    • VR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project)

    • View build HERE
    Member since: February 17, 2015
    Posts: 5 696
    Supporter

    Btw looking forward to following this, take heaps of pics :-)

    #6168
    Profile photo of delcowizzid
    delcowizzid
    Participant
    Member since: March 2, 2015
    Posts: 13

    Isn’t this centrifugal charged the last thing you want to do is cripple your low rpm torque production with way to big primaries and collectors

    #6169
    Profile photo of vs manta 218
    vs manta 218
    Participant
    Member since: March 2, 2015
    Posts: 796
    Supporter

    What do you declare as low down torque ?

    I dont get boost till 3000rpm and has no power below that so not after torque below that rpm

    having 1 7/8 for first 8-10 inches then 2 inch after that is what quite a few have said would be about the perfect size for 800-1000 hp and leaves me room for down the track if I go a torque power block and throw all I can at it

     

    this is entire set up was not built for low torque, it’s all mid range to top end power

     

    I was also advised by Daren him self and others to go with 3.5 inch collectors over 3 inch running this power level

    #6170
    Profile photo of vs manta 218
    vs manta 218
    Participant
    Member since: March 2, 2015
    Posts: 796
    Supporter

    What size would you suggest delco wizard for this sort of power between 3000-7000 rpm ??

     

    And nd can anyone tell me how far down the pipes the LS O2 sensors like to be ??

    And how close a EGT sensor should be to head port ?

    #6191
    Profile photo of delcowizzid
    delcowizzid
    Participant
    Member since: March 2, 2015
    Posts: 13

    Length will play a big roll short and small diameter can sometimes give the best of both worlds for both torque and hp.to big you may loose 30+ft/lb of torque below 4500 rpm and only gain 5hp at peak making the car slower by a lot.2″ upwards with 3.5 collectors is 540 bigblock teratory. Egt within 1″ of head o2’s closer to stock ls1 distance from port will make your learning to tune easier

    #6192
    Profile photo of vs manta 218
    vs manta 218
    Participant
    Member since: March 2, 2015
    Posts: 796
    Supporter

    If I was building a street user engine I would agree but myn is not street user

    it’s a rip tearing off it’s head high reving engine

     

    have a look at my dyno graph, that is 6500rpm at the top dot and this was the 4th power run and still blowing black smoke so it should make power till 7000rpm

     

    all my torque is up in the rpm range so that’s where Im focusing on

     

    I’m not interested in the area lower 4000rpm, it just is what it is down there

     

    all my calulations point to 1.9 or 2 inch primary’s in about 34 inch length

     

    getting this length right is where I’m goin to spend all my effort, And from what I can gather using 1 7/8 inch for first 8 inches and 2 inch the rest of the way seams to suit this best

     

    I haven’t seen collectors yet but I hope the have a bit of a choke down then back to 3.5 inch and if they don’t I might modify them so they do

     

    I’m not in any way doubting you this is just what I have found in my reshearce

     

    im interested in knowing what you think would be the optimum size for this type of combo

     

    and thank you very much for 1 inch info and O2 position same as factory exhaust manifold on a ls1

     

    #6210
    Profile photo of VRSenator065
    VRSenator065
    Participant
    • Adelaide SA
    • VR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project)

    • View build HERE
    Member since: February 17, 2015
    Posts: 5 696
    Supporter

    Does seem larger def is not always better.  I currently have 1 3/4″ on my 454 (NA).  When I was speaking to Jake Bain about doing heads/custom cam/headers etc as a package he ran the numbers through his design software and he said he could maybe make the 1.75″ headers work.  I def would lose on ultimate, but not necessarily that much, of course 1 7/8″ would be better and he thought 2″ was maybe borderline too big.  I guess that backs up Delcowizzid is saying (as expected).  But does yours being forced induction change that?  I always thought (maybe wrongly) that with NA you wanted/needed to be very particular about runner length and diameter, but with FI its more about getting it out, so you can pump the next charge in, so going slightly larger in diameter is better.  But is that not right?

    • This reply was modified 5 years, 3 months ago by Profile photo of VRSenator065 VRSenator065.
    #6213
    Profile photo of cava454
    cava454
    Moderator
    Member since: February 20, 2015
    Posts: 2 362
    Supporter

    Being manual u will go faster by keeping that “down low power”

     

    stalled auto. Bigger is better

    #6215
    Profile photo of vs manta 218
    vs manta 218
    Participant
    Member since: March 2, 2015
    Posts: 796
    Supporter

    From what i can gather its calulation between peak torque at what rpm and CI of engine

    Peak torque been at

    4700rpm in 355comes is about 1 7/8

    3600 rpm or below 355 is more like 1 3/4 and can go even less if its peak torque is at 2500 rpm and

     

    A 304 engine would be less again

     

    My torque climbs all the way to 6000rpm and is still on the rise

    A 355 peak torque been 5000 + comes in at a fly hair less then 2 inch and over 5200 rpm is 2 inch and higher continues getting bigger

     

    The same 3600 rpm in 454 would be more like 1 7/8

     

    But yours gary hits torque at 2200 so 1 7/8 will be big and may benefit more from 1 3/4

     

    If you go bigger cam and raise the torque line then the bigger pipes will work more effictevly

     

    Correct me if im wrong as this is just what iv been able to gather

    #6216
    Profile photo of vs manta 218
    vs manta 218
    Participant
    Member since: March 2, 2015
    Posts: 796
    Supporter

    Thats the absolute bare baisics

     

    Its gets a hell of a lot more complercited then that

    #6219
    Profile photo of vs manta 218
    vs manta 218
    Participant
    Member since: March 2, 2015
    Posts: 796
    Supporter

    And as gary says i to believe it takes a step up for F/I set ups as what iv found out that I put above is for N/A set up

     

    But still after others oppions on what they would use and why running a set up like this

    #6230
    Profile photo of VRSenator065
    VRSenator065
    Participant
    • Adelaide SA
    • VR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project)

    • View build HERE
    Member since: February 17, 2015
    Posts: 5 696
    Supporter

    Yea as I understand it pretty much as you have described is the go.  Just remember it really isn’t a  single purpose race car, so for example you don’t have straight through pipes, so its going to be a bit of a compromise.  Maybe the engine builders could help with suggestions?  I mean realistically you are going to be talking the difference between mental and insane, so your on a win-win anyways :good:

    • This reply was modified 5 years, 3 months ago by Profile photo of VRSenator065 VRSenator065.
    #6236
    Profile photo of vs manta 218
    vs manta 218
    Participant
    Member since: March 2, 2015
    Posts: 796
    Supporter

    They recommend 1 7/8 for my engine in N/A form but can just cope on 1 3/4 and have a engine with 555hp over the gold pro my is based from with 525hp and that one needs 1 7/8 as a minium

     

    Add boost and i have no idea lol

     

    2 inch is just such a nice number though lol

    #6241
    Profile photo of VRSenator065
    VRSenator065
    Participant
    • Adelaide SA
    • VR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project)

    • View build HERE
    Member since: February 17, 2015
    Posts: 5 696
    Supporter

    I would go 2″. That’s what my guts tells me anyways. I remember talking to an old school guy many years ago about exhaust valve size. He said, “make it big, get that shit out of there”. Not exactly elegant but you get what he means :)

    • This reply was modified 5 years, 3 months ago by Profile photo of VRSenator065 VRSenator065.
    #6243
    Profile photo of IJ.
    IJ.
    Participant
    Member since: April 2, 2015
    Posts: 3 210
    Supporter

    Personally I’d start the bigger pipe a couple of inches off the ports so the 1st bend is 2″ but that’s just me…

    #6245
    Profile photo of vs manta 218
    vs manta 218
    Participant
    Member since: March 2, 2015
    Posts: 796
    Supporter

    Yeah it’s what my gut tells me to Gary

     

    Ij  are you saying run a 1 7/8 for just the first straight about 35mm/ 1.5 inch or so and get the 2 inch bend on it there  ??

     

    This is the main part I haven’t made up my mind on yet unless some one comes up with some hard evidence these are to big but I’m certainly not finding any

     

    I have thought about running some cuts maybe 4 down about 30 mm on a 2 inch pipe and flaring it down a little just so I can get my extractor bolts in and that in it’s self would act as a scavenge  type thing or like you say a smaller pipe just a inch or 2 or make the first bend 1 7/8 something less then 8 inches I would imagine

    #6246
    Profile photo of IJ.
    IJ.
    Participant
    Member since: April 2, 2015
    Posts: 3 210
    Supporter

    I’d probably roll up 8x cones to go from whatever you can fit on the ports to 2″ Pete, this has proven to work well on Turbo dump pipes as it allows the Gases to expand quickly and can help a bit with scavenging.

    ARP Studs with 12 point small nuts will help here as well.

    #6249
    Profile photo of vs manta 218
    vs manta 218
    Participant
    Member since: March 2, 2015
    Posts: 796
    Supporter

    Absolute legend  :yes:

     

    best idea ever

Viewing 20 posts - 1 through 20 (of 149 total)

You must be logged in to reply to this topic.