Racer Exhausts 2 into 1 VS 2 into 2

Discussion in 'Old's Cool' started by Voltaire, May 4, 2012.

  1. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    I have a 2 into one on my race bike bike mainly as it became available and seemed like a good idea.
    Its unequal length and the 'muffler' has been gutted and a plate with holes fitted....its very quiet...road legal quiet.:rofl
    Last weekend I had a ride on a r100 with 2 into 2 and owner/rider/builder said " look at any pictures of BMW racers and they have 2 into 2.
    The bike goes well but it would be good to compare.
    Any thoughts ?
    I have ditched the filters and am waiting on trumpets from Bevel Heaven.

    [​IMG]
    #1
  2. motu

    motu Loose Pre Unit

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    BMW knows more than you and any alteration from stock the bike will lose HP.

    I've had the standard system with standard mufflers (rotted, so not something to base my later experiments on) then short mega's, then unequal 2 into 1 with Supertrapp and now equal length with Supertrapp. I'm happy with it now - I get good top end and really good mid range. I don't race, and for my roads operate in the 4,000 to 6,000rpm range, with 7,500 being available if I need it and 8,000rpm for run away wheelspin on gravel.

    I think the Supertrapp is the secret - the rest of the system doesn't really matter, you can tune it all out with the muffler.
    #2
  3. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    Yes BMW does know more than me :cry 8000RPM:eek1
    I was hoping to get some Brit bike guys chip in as they are more flexible with specifications...:rofl
    #3
  4. Houseoffubar

    Houseoffubar HoFmetalworks.com

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    A 2 onto 1, or 2 into 2 exhaust have very little difference in HP. The 2 into 2 has the advantage of making good power, while being quieter than the 2 into 1 system.

    BTW Supertrapp exhausts make good spark arrestors, they however are the worst muffler made for horsepower. The disc system simply increases back pressure by choking off the exhaust until it is acceptably quiet (usually after losing several HP) It is literally the same as welding a washer to the back of your exhaust to restrict it into being quiet.
    #4
  5. motu

    motu Loose Pre Unit

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    A race core Supertrapp certainly doesn't reduce noise...maybe with one disc but not with anymore. I've put less on mine until it reduces power, but the noise stays the same. I do noise tests as part of my job - we test at 2,500rpm for a 2 valve twin and it takes an effort to keep mine at 97db. I have to fail over 97db, although 100db is the limit for road use.
    #5
  6. trustme

    trustme Long timer

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    As a brit bike rider , I would suggest you fit star washers. :evil:evil:evil
    #6
  7. Padmei

    Padmei enamoured

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    :rofl:rofl:rofl
    And get drip tray?:lol3
    #7
  8. Pigford

    Pigford British

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    Basically, soon as you start messing with any part of the engine it will have a knock-on effect and to get it running right will need more time & money spent matching the unit as a whole. But isn't that what makes bikes fun :wink:
    #8
  9. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    true, I've only had the bike running for what amounts to a few hours on the track, It runs fine considering so much was changed at once when we rebuilt the $275 engine..... heads skimmed 1mm, sports cam, inlets opened from 32 to 36 with some Dells fitted.
    It is fun looking at all the what ifs and maybes.
    Sorting out the programmable ignition I got for it recently this week :clap.
    #9
  10. motu

    motu Loose Pre Unit

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    Yeah, I do all those calculations too - my exhausts aren't something I slap together with some scrap pipe. I've just worked out what size 1/4 wave resonator I need to cut noise at our 2,500rpm test speed....and it needs to be over 2 metres long!
    #10
  11. PJay

    PJay Any bike, anywhere

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    Depends how much you want to spend, but getting a decent system designed according to the rest of what you've done with the engine's always the optimum. Wobbly designed not only the 2-stroke systems on my TZ Yamahas, but also the 4-2-1 on my CB1100, and for this last we have 6hp more on the dyno from the exhaust alone compared with a yay whizzo brand one from the USA.

    In general terms, on all my Norton twin race bikes, we always had the best power on the dyno from 2-2s, but the most even spread from 2-1s.
    #11
  12. trustme

    trustme Long timer

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    Volty has a cross tube on his headers as does a certain British bike, are these a help or hindrance. My understanding is they help midrange but do they detract from the top end ?.
    #12
  13. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    hmmm Wobbly does exhausts too....I just got an ignition off him.Must ask him.:wink:
    Hey Motu /WOF man...why is my almost empty muffler so quiet? :huh
    #13
  14. motu

    motu Loose Pre Unit

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    You get out what you put in - you are not putting much into the exhaust....so not much comes out.
    #14
  15. adventure950

    adventure950 Anglo-Saxon

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    I have run my modified BMW engine with both a 2 into 1 and now a 2 into 2. The 2 into 1 was a siebenrock sgs2 system super light well made and provide good power and torque it cost about £900. I now have sold that and fitted a 2 into 2 from Kiehen (about £600) its a sports system for my dakar replica. I have not run this far yet but the short test ride I done with it seemed to give excellent power and torque. I had advise from Klaus at HPN and he stated that in their experience the airhead generally worked better and gave better performance on a 2 into 2 system. I should be doing a 500 mile ride in two weeks time to run the project bike in so should be able to report back on the comparison between the two bikes. I may even get another Dyno test run then I would have a direct comparison between the two exhausts. As I have the results for the 2 into 1. Jake.
    #15
  16. pommie john

    pommie john Long timer

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    The dyno's the only way to find out.

    I started with a 2into 1 with 32" primaries and a megaphone. It was useless. It had a torque curve shaped like a big M. No power in the mid range.

    I've had good results with Supertrapps on my current 2 into 2 system
    #16
  17. PJay

    PJay Any bike, anywhere

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    The Wobbly Man's mainly a zorst guy. Among his claims to fame, he made the expansion chambers on the last privateer machine ever to win a world championship (Jan Ekerold, Bimota TZ350), so he goes waaaay back with this stuff.

    PVL ign?
    #17
  18. PJay

    PJay Any bike, anywhere

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    Mainly a noise compliance thing, promoted by Triumph back in the 70s as a torque/power spread thing - bollix.
    #18
  19. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    Ignitech, getting some mounting plates made up, hoping to fit in next week or so....bye bye Boyer...
    The two stroke guys at the Buckets rate him pretty highly.
    #19
  20. motu

    motu Loose Pre Unit

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    Now they've put you in Airheads you aren't going to get the wider response you were hoping for - you should've deleted that photo and shut up about what bike you were riding...people follow these threads y'know.

    With a single pipe per cyl you can use resonance tuning for peak power, in my experience this makes a screamer with plenty of top end but loses bottom end or may run ragged down low. 2 into 1 can't take advantage of the resonance. 2 into 1 engines seem to have more bottom end....but then most 2 into 1 bikes aren't really performance bikes....
    #20