Cobra Exhaust Tuning Recommendation.

Discussion in 'Exhaust' started by lilredrooster, Jul 8, 2018.

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  1. Aug 2, 2018 #41

    lilredrooster

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  2. Aug 3, 2018 #42

    Killjoy

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  3. Aug 3, 2018 #43

    one2dmax

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    I have a pretty decent set for sale if anyone is interested. BUT, i always caution to be prepared for the power loss. I don't know how to say it other then that there is no way you're ever going to make them perform with no amount of wishful thinking and modifications.
     
  4. Aug 4, 2018 #44

    lilredrooster

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    Has anyone out there actually tried to modify the Cobra Exhausts and have they got any before and after modification numbers?

    Dyno records/readings/figures before and after exhaust modifications?

    Quarter mile times? and/or Trap/Terminal speeds before and after exhaust modifications?
     
  5. Aug 4, 2018 #45

    VMAXXIMUM

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    I'm not sure whether we should admire your tenacity or feel bad for your stubbornness. However besides the turbo/supercharger/nitrous idea I suggested in an earlier post I did come up with an idea that I think will work. We know the two main hp killers are the stock head pipes and the lack of a crossover. So...put a proper header on and modify the cobra's to fit the larger diameter pipes then drill some holes and weld in a crossover, then jet your carbs properly and voila, more power. Then you can post your before and after numbers.
     
  6. Aug 4, 2018 #46

    Fire-medic

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    Given the fact that the Cobra 4-into-4 exhausts are limited by the laws of physics, you need to look to other methods of gaining HP. What kind of oil do you use? A premium motorcycle oil will net you several HP, and allow proper clutch function, while protecting your engine from heat and from oil failure. You do know that automotive oil isn't good for your engine?
     
  7. Aug 5, 2018 #47

    one2dmax

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    We have the before and it was so tremoudously terrible we decided not to bother with an after. As I said before the mufflers themselves are not the main issue (except for lack of scavenging since they aren't tied together). One of the main issues are the smaller primary pipes. This is also why there are no gains over stock with any brand of slip-on system.

    I decided it wasn't worth the time and costs to try and make the Cobra's at least get back to the stock power levels. My customers are looking for more and that requires all of it to be replaced.

    Feel free to invest the significant time and money to go disprove what our experience is. Please add those files to this thread so we can all see your results.
     
  8. Aug 6, 2018 #48

    lilredrooster

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    Soooooo Movin on Lets try again shall we......

    Has anyone out there actually tried to modify the Cobra Exhausts and have they got any before and after modification numbers?

    Dyno records/readings/figures before and after exhaust modifications?

    Quarter mile times? and/or Trap/Terminal speeds before and after exhaust modifications?
    [​IMG]
     
  9. Aug 6, 2018 #49

    VMAXXIMUM

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    I'm leaning towards stubbornness but now I'm thinking your one of those robot posters that will just keep repeating what you've been programed to type.....or your impersonating a former member that was just looking to create controversy. lilredrooster Sean just told you he'd once considered it but the cost and time were way out of line with the potential benefit of simply recovering what was lost and no net gain. Movin on would be to drop this by now silly thread and get to something more interesting for all of us.
     
  10. Aug 6, 2018 #50

    lilredrooster

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    Many Thanks to All that have contributed to date both the positive and the negative, very much appreciated.....

    Please Note: The title of the thread is: Cobra Exhaust Tuning Recommendation.

    The intention is to improve the performance (no matter how small an improvement) of the Cobra Exhausts (which as most would realise) are intended to slip on to the standard front headers.....

    This thread is not intended to keep waffling on about how the cobras lose power...... We know this already.....

    This thread is about trying to improve the Cobra exhausts in some way, shape or form....
     
  11. Aug 6, 2018 #51

    Killjoy

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    I suppose one could weld a balance pipe between the two rear pipes, and then somehow X them into the front pipes. Doesnt seem incredibly difficult.
     
  12. Aug 6, 2018 #52

    lilredrooster

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    Many Thanks again KillJoy for all your help and support I really appreciate your input. :thumbs up:

    Above all else Thank-you for keeping the thread on-track and focussed on the original theme and bringing some positivity along too. :eclipsee_gold_cup:

    The way I see it so far there are two practical ways to improve the Cobra Exhaust performance.

    (A) Tune the Carbs via Jet Kit, Jetting etc. (We have already discussed this option earlier in the post and Many Thanks to Vinmax for his input in this area).

    (B) Modifying the Cobra Exhausts.

    Out of all the people that have so far taken an interest you are the only one to date that has "actually" made an attempt to "actually" modify the Cobra exhausts.... I salute you for it and thanks again for sharing.... :eusa_dance:

    To be continued..... :git:
     
    Last edited: Aug 6, 2018
  13. Aug 6, 2018 #53

    Fire-medic

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    Just hacking the system up isn't any guarantee of success. The engineers who are proficient in the harmonics of flow dynamics designed a decent stock system, removed by some people because they like the appearance of 4 into 4 systems better. The loss of power is the price you pay for 'pretty.' Most VMax owners are into the 'go,' not as-much the 'show.' There are so-many variables about exhaust design, that haphazardly cutting up that pretty 4 into 4 will destroy the looks, make it more-susceptible to failure from rusting-out, since it's no-longer plated metal, and likely going to result in leaks, difficulty in removal/replacement, and possibly even-worse performance, since the owner knows nothing of engineering an effective system. If they did, they would have started with something that works to begin-with, like a full UFO 4-outlet system, and a proven track record of something that adds power, instead of killing power, like the Cobra 4 into 4.

    We all "get" the OP bought a bike with a pretty-appearing dysfunctional exhaust. We also "get" that he cheerfully and very-stubbornly wants to 'fix' something that cannot be easily-fixed. If he would just source a stock exhaust, he would regain the horsepower the Cobra exhaust cost-him. Bottom-line: you cannot make a silk purse out of a sow's ear. Nothing can easily be done to fix the Cobra 4 into 4, to even get-back to a stock bike's power output, no amount of jetting, no aftermarket air filter, no removing the air filter box top, no propellers in the intake tract, no "Fish" carbs (you have to be old to know about the Fish carbs), no Marvel Mystery Oil upper-cylinder injection system, no fiberglass cloth header wrap, nothing will 'fix' it, except to replace it.

    Used exhaust systems are easily available on here, either stock or full aftermarket, I've bought and sold them.

    Someone who wants more power, install this with a Morley jet kit:
    https://www.ebay.com/itm/85-07-Yama...ax+exhaust&_from=R40&rt=nc&_trksid=m570.l1313

     
  14. Aug 6, 2018 #54

    one2dmax

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    I have had a number of customers ask this over the years and most don't want to pay for the costs of research to make this happen. My estimates would be that maybe you could get back 5% of the lost 10% power. I personally don't include jetting since that should be done anyway (leaner) to get the bike running properly. The 10% loss INCLUDES having the bike jetting correctly. An incorrectly running or jetted bike will lose even more (and where many of the "baseline" bikes used to compare jet kits start out).

    So, if you want to experiment i'd suggest alteration of them in a manner to join them with a merged section after the stock pipes. Much like most standard slip-on systems do. Then you can open it back up to as many mufflers as you wish. You'll need to keep a small area of that merged section at around 2" diameter or so for some distance before you go back to the mufflers. Simply adding a cross tube between the mufflers isn't going to let the scavenging work properly.

    Doing something like this should get you back to around stock power output (still need to go smaller mains to get this right). At that point to see any gains you need to replace the stock primary pipe work. This needs to be enlarged to around 1.625" vs the stock 1.5"

    Again you need to have the correct mergers of the pipes so that the scavenging works properly. It really isn't even all that big a deal which pair you merge together (RF to LR and LF to RR, or RF to RR and LF to LR, or all 4 together). That doesn't have a significant impact to power in the systems we've tested.

    I MAY have some cheap primary pipes I can donate to your testing and I may even have some cosmetically damaged Cobra's that I can sell cheap for your testing as well. Just would need to provide the scientific data that you're asking someone else to provide you. I can even loan you a jet kit if you want to give it a try and see what happens when you add more air then you can flow properly (kind of like putting an 850 double pumper on the average 350 small block because that sounds like the cool thing to do).

    I don't want to seem like i'm completely against all of this but rarely do I have a customer that wants to spend 1000's of dollars to attempt to make something work (with no guarantee it will) when it's so much cheaper and easier to get tried and tested stuff that already works. UFO made their quadzilla system some years back to get guys that look that some so desired. I even had a special setup made for the Marks system that had a dual muffler setup on one side. Just really all depends on what your budget and goals are.
     
  15. Aug 6, 2018 #55

    Eugene Brad

    Eugene Brad

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    Quick question regarding exhaust. F.M. you call the cobra slip ons a 4into 4 system. Is any system with 4 tips considered 4into 4. Seems to me if the tips have an immediate Y, the exhaust system is still only 4 into 2. Does that make any sence? Mostly curious if mine is a 4into 4, pictured? I believe they are ufo quadzilla.
    Thanks, and sorry for the thread hijack.[​IMG]

    Sent from my SM-G360V using Tapatalk
     
  16. Aug 6, 2018 #56

    one2dmax

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    That is a 4-2 with dual tip mufflers.
    You have 4 Cylinders
    Going into two separate Collectors
    then into the two muffler tips (not much of a muffler and you don't count "tips")

    A kerker (full system) (4-2-1 *Very similar to what car guys might call a Tri Y system)
    has 4 Cylinders
    Into 2 collectors
    Into 1 Collector
    Into 1 shared muffler

    The older Hindles (4-1)
    Have 4 cylinders
    into 1 collector
    into one shared muffler

    The Cobras are (4-4)
    Have 4 cylinders
    NO collector
    4 Mufflers independent of any others
    *** Note, this isn't 100% accurate as the front pipes do actually have a cross over though it's not all that effective
     
  17. Aug 6, 2018 #57

    lilredrooster

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    G`day Eugene Brad,

    Thats a Grrrrreat looking Bike Mate, Exhaust has its similarities with the Cobra Exhausts, I would call that a 4 into 2 into 4, 4/2/4, still a 4/4, but, a much better design and better performance potential than the Cobra which is 4 into 4 (4 x individual pipes all the way through) 4/4 with a balance pipe between the front 2 cylinders only.

    Thats why it is called the "Quad"zilla..... 4 x points of Exhaust gas Entry into the pipes, 4 x points of Exhaust Gas Exit out of the pipes. The Duozilla does not seem to have quite the same ring to it...

    Certainly the Cobra Exhausts could be modified along these lines and could well yield better results than its original form. Many Thanks for posting and sharing...... :clapping:
     
    Last edited: Aug 7, 2018
  18. Aug 6, 2018 #58

    lilredrooster

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    Thats a Grrrrreat Post Sean, Many Thanks again for your thoughts and expert comments, very much appreciated.... :eclipsee_gold_cup:
     
  19. Aug 6, 2018 #59

    lilredrooster

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    Many Thanks as always for your thoughts FM, much appreciated, power and performance is not the be all or end all of the VMax for everybody?

    In fact, if an individual were purely focussed on power and performance, they most certainly would not be riding a Gen 1 VMax in the first place!

    Sounds to me that reclaiming at least some of the Cobras lost 10HP is perhaps achievable? Not expecting any guarantees.....
     
  20. Aug 30, 2018 #60

    lilredrooster

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    I fitted COPS, new plugs, fitted 147.5 main jets and changed the fuel from 98 octane unleaded over to 91 unleaded, has cleaned the rich running up significantly, the ends of all the exhaust tips have always been black/sooty, no more, no trace of rich running at the exhausts now.....

    Had a closer look at the cobra exhausts internals....

    The bores of the Cobra main pipes are 70mm Inside Dia.

    Inside each main pipe is a perforated circular/baffle tube (approx 25mm Inside diameter) which runs central to, and most of the length of each main Cobra pipe.

    The perforated baffle tube is attached at both ends and supported by two doughnut section/profile end plates.

    Approx in the middle/centre of the length of the perforated baffle tube the internal diameter of the tube is blocked off by a single circular solid disc, approx 32mm in diameter.

    The internal design means that the exhaust gas enters the Cobra exhausts from the front, the exhaust gas meets the first doughtnut shaped end plate and continues through the centre and along the central perforated baffle tube.

    The exhaust gas is then stopped dead by the single central solid disc head on, the gas is then forced through the perforations in the tube crossing from the inside dia of the tube to the outside diameter of the perforated baffle tube.

    The exhaust gas continues rearwards on the outside of the perforated baffle tube until it meets the rear doughnut shaped end plate head on, the gas is then forced back through the perforations in the tube crossing back from around the outside dia of the tube to the inside diameter of the tube, downstream of the single central solid disc.

    The exhaust gas having now returned to the inside diameter of the central perforated baffle/tube now exits to atmosphere through the centre of the doughnut/section rear end plate.

    Strikes me that the internal single central solid disc is a massive restriction to the exhaust gas flow.....
     
    Last edited: Aug 30, 2018

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