Hey Mark,
Sorry, I'm a dork... Still don't get it... Are the jet sizes you mentioned above your recommendations for a stock set up or the Cobras at my evelvation???? :ummm:
Cobra Exhaust HP Loss Explained, Please?
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Hey Mark,
Sorry, I'm a dork... Still don't get it... Are the jet sizes you mentioned above your recommendations for a stock set up or the Cobras at my evelvation???? :ummm:
No worries. The 142.5's will be good at your elevation.
For either exhaust set up? (Stock or Cobras)?
Cobras. For stock I would try 145's.
Excellent! Thanks Mark!
kozy
Well-Known Member
Bastards.....I bid 3 times in the last 5 minutes of the auction and I kept having someone else outbid me immediately afterwards. Someone wanted it a lot more than me I guess.
Need to use eSnipe and set the max you want to bid. It will bid for you in the last 8 seconds. No one has time to over bid you if yours is the highest. If another person uses a snipe service and has a higher max they will win. At least you don't have to even be at the computer to get in your highest bid. This is better than eBay's proxy bid as your max bid can be determined by other bidders long before the end of bidding.
Praxxl
Member
Here's my theory. Look at the stock exhaust and each cylinder can exhaust thru both mufflers. Look at how the front cylinder exhaust is paired with the opposite side rear cylinder exhaust.
Because each of the 4 pistons exhaust at different times, one cylinder can exhaust through both mufflers while other pistons are at other points in the engine cycle.
With the Cobra's, when a cylinder exhausts, it pushes all the exhaust thru one muffler and then the remaining 3 of the 4 strokes, the muffler does nothing.
The V-max arrangement is well thought out.
Because each of the 4 pistons exhaust at different times, one cylinder can exhaust through both mufflers while other pistons are at other points in the engine cycle.
With the Cobra's, when a cylinder exhausts, it pushes all the exhaust thru one muffler and then the remaining 3 of the 4 strokes, the muffler does nothing.
The V-max arrangement is well thought out.
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Jasonc994
Well-Known Member
I have a set I may be parting with soon. Message me if your still looking. ThanksI'm starting to realize that I may have purchased my VMax more for its unique appearance and reputation than its brute force. :rofl_200:
I may change my mind over time, but my infatuation with the look of the Cobras just won't go away. As for the Morley rebuild, my goal in doing so is reliability and rideability, not blowing every bike I come across off the road. I may, again, change my mind in the future, but right now I just want to know that every time I get out on my Max that, 1: It will get me there in style and "on time", and, 2: That I will not see another bike like it on the way.
Having said that, there seem to be a number of the Cobra systems out there "gathering dust"... If folks are willing to part with them, let me know. I will be "demo-ing" a loaner set soon and may want to aquire one or more sets (if the price is right) to experiment with...
...or, I may just put them on, re-jet appropriately, and enjoy my Max in what ever way I choose to do so.
Speaking of re-jetting, should I be doing so if I ride @ 4000ft. with a stock set up anyway???
\m/ DS
Jasonc994
Well-Known Member
I have a set of cobras on my bike right now and just got my plugs perfect colors and running awesome. Cant wait to put on a kerker though
I rode a Cobra-equipped bike for someone looking to by a good used bike, he was looking at one from a friend's shop. What a difference from my UFO 4/1 setup in performance!
The Cobra-equipped bike ran OK, no stumble, no miss, but it was...flat. Having been riding my bike for a quarter century, I knew how a properly-jetted aftermarket exhaust should run. I had a stock exhaust on my bike when I bought it from the Yamaha dealer, of course. I have no issues with the stock exhaust, it's quiet, the chrome is good, the material is not easy to dent, and the bike runs well with it.
The Cobra 4/4 didn't seem to rev as-quickly, it definitely was slower than what I was used-to. As-to power, there was a noticeable lack of it, compared to a stock bike, or to mine with its 4/1.
I returned to the shop and told the prospective buyer, "the bike runs OK, but if you choose to buy it, the first thing I'd do would be to rip-off that Cobra 4/4 and install another exhaust. It's affecting the performance in a bad-way. The bike doesn't run like even a stock VMax should. Yes, it's 'pretty,' but you aren't getting all of the horsepower that the factory put in-there!" He bought it, and kept it with the Cobra exhaust. I later learned he bought a Shadow and sold the VMax. I reckon it wasn't his cuppa' tea, even in its emasculated form.
If you like the way your Cobra 4/4 bike runs wait until you switch-out the exhaust, even for a stock one. It will seem like a completely-different bike in its performance.
The Cobra-equipped bike ran OK, no stumble, no miss, but it was...flat. Having been riding my bike for a quarter century, I knew how a properly-jetted aftermarket exhaust should run. I had a stock exhaust on my bike when I bought it from the Yamaha dealer, of course. I have no issues with the stock exhaust, it's quiet, the chrome is good, the material is not easy to dent, and the bike runs well with it.
The Cobra 4/4 didn't seem to rev as-quickly, it definitely was slower than what I was used-to. As-to power, there was a noticeable lack of it, compared to a stock bike, or to mine with its 4/1.
I returned to the shop and told the prospective buyer, "the bike runs OK, but if you choose to buy it, the first thing I'd do would be to rip-off that Cobra 4/4 and install another exhaust. It's affecting the performance in a bad-way. The bike doesn't run like even a stock VMax should. Yes, it's 'pretty,' but you aren't getting all of the horsepower that the factory put in-there!" He bought it, and kept it with the Cobra exhaust. I later learned he bought a Shadow and sold the VMax. I reckon it wasn't his cuppa' tea, even in its emasculated form.
If you like the way your Cobra 4/4 bike runs wait until you switch-out the exhaust, even for a stock one. It will seem like a completely-different bike in its performance.
ga_max
Well-Known Member
++ Fire-medic's response. I put Cobras on my max and loved the look and sound but it lost a good bit of power and the VBoost seemed to lose its kick. I replaced them with Delkivics on it and the joy is back.
Traumahawk
Well-Known Member
Its my understanding that the loss in performance with a cobra exhaust is due to exhaust scavenging. Look at it this way. With 2 cylinders tied together (exhaust wise), and they fire after one another, 1 cylinder will fire, and the exhaust gases will leave the cylinder, and will travel down the exhaust pipe. it will create a small vacuum behind it. That vacuum, when paired with the cylinder that fires next, will help pull the exhaust out of that cylinder, and so on and so forth. As the cylinder empties better....it will pull in more air fuel mixture. More air fuel mixture......more power.
The cobras dont have the cylinders paired together, so you dont get the benefits of exhaust scavenging.
This is my understanding.
The cobras dont have the cylinders paired together, so you dont get the benefits of exhaust scavenging.
This is my understanding.
That is exactly correct Eric. I have been trying to let consumers know for years the expectations of these and don't buy them if you want to add power.
I like the looks of the Cobras over the "Can" look. Not sure I would want to lose power though. Would rejeting the carbs not fix that?
GP
GP
"GPrider:"
Not-only no,
but, Hell NO!
This question gets asked-about the Cobras frequently.
"I like the look of the Cobras, 4 exhausts! Cool! But, why isn't my bike performing as-well as stock? The difference in the loss of power is very-noticeable. Won't re-jetting fix that?" (See reply, above)
Save yourself the money and expense of buying and installing the Cobras. Simply remove one of your spark plug boots and leave it dangling-off, disconnected. The effect on your bike's performance will be similar, and one of life's great tragedies in motorcycling will befall you: VBoost won't, like stock.
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There is a very long discussion thread about this very subject and one guys stubborn attempts to try and regain his power. I think he managed to get some back but I don't think he got it back to stock levels after a LOT of testing and tuning.
Talk about an exercise in futility! I don't think he had much success in any of it, but you're correct, he was too-set in his ways to take an easier path, like re-install a stock system, and immediately (with stock jetting) pick-up close-to 15 RWHP. I get that the Cobras are "pretty," but I can live-with the OEM system just-fine, and especially-so if I get to keep my stock amounts of HP. Sacrificing 10-15 RWHP kinda defeats the whole reason for owning a VMax. If it was a Shadow, no one rides those for performance, it's the V-twin look/style. The owner gets to choose his mods, so if that's what he wants, his choice.
He was a good sport about asking questions, and hearing again and again, "no, there is nothing you can do but choose another exhaust, if you want to regain the HP."
Here is the l-o-n-g thread of-which Sean mentioned. Be sure to start at the beginning, and to read it until the end. Don't skip anything. It's an 'exhaustive' thread, one defining 'stubborn' and 'futile.' It reminds me of that speech by the Strother Martin character, "Captain," in "Cool Hand Luke."
https://www.vmaxforum.net/threads/cobra-exhaust-tuning-recommendation.46778/
I've ridden two Cobra-equipped bikes, and both had the same operational issues: lack of stock amounts of horsepower, and "flat" VBoost function. They just didn't "kick" like a stock exhaust, or a properly-jetted full aftermarket exhaust does, in VBoost.
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Ok. I'll take your word for it. Ha! I have mostly kept my 95 almost completely stock anyway. I like it that way.
GP
I have a set of what appears to be slip-on SuperTrapp mufflers. Do they actually slip-on or do you need the complete set of headers as well to make it work? If so, has anyone done this, did you need to rejet and what were your perceived results? I have a new set of Marving mufflers on it now and they seem the same as stock to me as far as sound goes and they are a touch shorter so you can see more of the back tire. The price was reasonable from Exactrep and delivery was quick.
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