V6 Cross over exhaust pipe

Discussion in 'Capri Chit Chat' started by 2.8jonny, 13 January 2020.

  1. 2.8jonny

    2.8jonny Registered Capri Power Member

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    Hi guys
    Has anyone ever fitted an x pipe or h pipe cross over to their v6 exhaust? I've been doing some reading around the subject and wonder if anyone has any experience?
    I'm interested in benefits to engine torque, power, exhaust note and volume?

    Thanks guys
    Jon
     
  2. robt100

    robt100 Registered Capri Power Member

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    I believe it helps with evening out pressures and scavenging effects....but sadly I can't help much, my 24v runs on a single exit system!
     
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  3. barnfind

    barnfind Registered Capri Power Member

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    I've only experience with modified BMW S14 4cyl and S54 6cyl M3 engines that both have superior exhaust header/manifold design and x-pipes under the front floor.
    BMW Motorsport designed them over the std production range, and these are the parts maintained in their Group N & A catalogue - i'd take reassurance from this alone.
    I can't see any negatives and if i wanted a more modified look to my car wouldn't have hesitated to fabricate the X to add to the tubular manifolds.
    May make gearbox removal a bit trickier on a Vee engine?
     
  4. 2.8jonny

    2.8jonny Registered Capri Power Member

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    All good points and I'm planning on some flanged or maybe v band clamps so the section can be removed for gear box or prop removal.
    I'm planning on adding a couple of cheap import silencers immediately after the down pipes to act as resonators, apparently the glass pack dissapears quickly making them less silencer and more resonator. Hopefully this will reduce the boom at cruising speeds I used to get without my decibel inserts but give me the power back that they cost.
    After the resonators I'm planning an x or h pipe cross over but haven't decided which.
    Longer term the whole exhaust will be stainless but I'll start with the front and then the rear silencer, I think I can get a straight through 4"x14" glass pack in there in place of the current 3"x10".

    I'm gonna stainless mig it, which will make some people sick but how often do you admire the tig welding in yer middle box?

    Longer term I want to be able to drive out of the garage before 10am on the weekend without worrying about annoying the neighbours.

    Thanks for your reply.
    Jon
     
  5. Stroker

    Stroker Registered Capri Power Member

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    In my experience you will be disappointed with the results if your planning on the straight though glass pack mufflers reducing the resonating boom at cruising speeds. I had a straight though glass pack as a center muffler and the resonate booming at cruising speeds was awful to say the least.
    I got rid of it by fitting a 3 chamber muffler. No resonating boom now and a joy to drive period!!!
    But I'm at the stage in life that I really don't like a noisey car at all. So I have been doing a bit of experimenting on my exhaust purely for noise control.
    I was really impressed with the 3 chamber muffler when I fitted it to the center section, that I fitted a 3 chamber muffler to the rear as well. But unfortunately that was a fail as the db went up.

    db scale on left, rpm at the bottom.
    [​IMG]
    The car is still pleasant to drive from the inside but far too loud on the outside for my liking.
    My car runs a 2.5" single system, so now I'm looking at maybe the Turbo type of muffler may be a better choice for making it quieter. Also looking at reducing the size of the pipe. I've been looking at some of the factory BMW and Nissan exhaust systems and they seem to run quite small diameter pipes, yet still make good power.
    So the thought now is to run smaller pipes(maybe 1.75") to 2 center Turbo type mufflers and then collect to a single 2"-2.25" pipe to rear Turbo type muffler. I have no doubt that it will cost some HP, especially at top end power, but I really don't care so much now a days.
     
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  6. 2.8jonny

    2.8jonny Registered Capri Power Member

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    Thanks for the as always thoroughly thought out and researched response stroker.
    My original system fell off 15 years ago and I've run a 2" twin capri club system ever since. When first fitted I couldn't drive the car as the two straight through silencers in each bank did virtually nothing, it was a deep booming sound at idle that made every one look and at cruising speeds you needed ear defenders. I fitted slip in decibel incerts from demon tweaks in the tail pipes and the in cabin boom was gone immediately and the idle volume dropped and rose in pitch. At the time I was delighted at the improvement but now would like a further reduction in noise and to release any horses held back by the inserts.
    When I last did any serious work on the car I added a couple of inches of pipe to the ns over axle section because it used to get banged on speed bumps when I carried passengers but also welded the decibel inserts in to the rear silencers in order to hold the perforated steel core in place as its falling apart. In fact I question how much absorbtion material is even left in my exhaust.
    So I short it's time for an exhaust refurb and I'm looking at my options.
    I'm also fascinated by how a 2.8 v6 will sound with a cross over twin system. The current idle is quite unique with its choppy note, essentially two engines competing to be heard, a cross over should result in an even exhaust note more akin to a modern v8....... Maybe.

    Jon.
     
  7. Stroker

    Stroker Registered Capri Power Member

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    It's just a personal thing but I don't like the sound of any 6 cylinder with completely separate twin pipe systems. I used to run my Capri Essex V6 with a single system(3") and also my Sierra(2.5"). I believe the cross over or H section will definitely help in evening out the exhaust tone. I doubt there will be any noticeable difference in performance with fitting a crossover. When it comes to the exhaust, the 2.8 motor does seem to respond quite well to header primary length, short for top end performance, long for bottom end performance, and difference in performance is quite noticeable.
     
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  8. barnfind

    barnfind Registered Capri Power Member

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    We've fabbed and replaced silencing with stainless wire in the Mig with neat results, with good bend and cuts you'll be fine. Huge fan of flap discs in grinder and the rotary these days, they help alleviate the chore of working with stainless.
    Yes, Tig's do give an inferiority complex, and it is the next level. But 'In period' i can't remember scrutinizing the welds on my Cherry Bombs, Ears, Peco's or Janspeeds for that matter . . . :D
     
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  9. Brookland32

    Brookland32 Registered Capri Power Member

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    hi I have fitted a balance pipe between the banks just under the tail of the gear box I have a 3.2 with a camm shaft I cant remember what it is but of a racy nature I used to get back fires pops and a very harsh sounding exhaust note but now get a very even note with no pops or bangs lol sounds like a quiet TVR
     
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  10. 2.8jonny

    2.8jonny Registered Capri Power Member

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    Thanks for that input mate, I've got some custom silencers made in 304 stainless now. They are massive and literally the biggest I can fit without compromising ground clearance. I've taken strokers advice and compromised on middle box flow by adding a ressinator chamber / baffle to bring noise down. I'm yet to bud the system, will likely be next winter.

    Did you do a before and after to see how much of a difference the cross over pipe made to performance? Or were you mostly interested in its note?

    Cheers
    Jon
     
  11. Brookland32

    Brookland32 Registered Capri Power Member

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    no I haven't done a comparison of power I honestly don't remember feeling any difference but for me was definitely a great improvement on exhaust note
     
  12. 2.8jonny

    2.8jonny Registered Capri Power Member

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    Funny, I always liked my exhaust note but when I analysed it, I realised its quite harsh and load with an annoying idle. I'm quite excited about how it will sound when the banks are balanced.
    Thanks for the input.
     
  13. SIDEWAYS 3.0 GHIA

    SIDEWAYS 3.0 GHIA Registered Capri Power Member

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    I know from experience, a 2.8i Granada, because of a single exit system sounds better than a 2.8i Capri, but l have a 3.0 Capri and a few Savages, all running twin systems and they sound brilliant. I do have one car on a stainless steel system and that sounds crap, it's quiet a tinny sound, shame it I'll never need replacing!!
    I will be very interested in your results.
    I always remember following my mates 3.0 Ghia and it always seemed to condensate out of the NS silencer more than the OS and there was absolutely nothing wrong with it, strange what you remember.
    My Mk1 3.0 GT XLR was ran without middle silencers to a rear box, that did sound good !!!
     
  14. 2.8jonny

    2.8jonny Registered Capri Power Member

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    I'm afraid you probably have to wait 18 months.......
     
  15. Clockwork Orange

    Clockwork Orange Glasgow Subway- Keeping it simple since 1896 Staff Member Moderator

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    a very good friend of mine did this ..
    it was a Capri with a 3.6 RV8 (wee bit worked) 05JAN28_17.JPG 05MAR04_07.JPG 05MAR04_08.JPG Mercedes compressor .. back then it sounded absolutely lovely
    and went rather well ..
     
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  16. BigJ

    BigJ Registered Capri Power Member

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    My Cosworth uses a 2.8i Janspeed system and sounds great. It also kicks out a fair amount of power ;)
     
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