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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