Cobra Exhaust Tuning Recommendation.

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Better buy some magic pixie dust to sprinkle on that Cobra-equipped bike because in the face of all information to the contrary, you want to-believe you can make that dog of an exhaust regain what performance it loses after installation. I've owned or ridden your Cobra-equipped VMax, the Kerker 4/1; a full UFO 4/1 with the UFO shorty beveled exhaust tip, with the UFO megaphone and its two different exhaust tip sizes; and the full UFO system with two different custom canisters. I've also owned different slip-ons, including the F1 2/2, the Supertrapp 2/2, and of-course, the stock VMax exhaust.

I've dynoed my bike, though not in all configurations mentioned above. I've owned one or more Vmaxes continually for twenty-five years. By a considerable margin, the dog of the lot was the stock VMax with a Cobra 4/4. It wasn't in the same league with any of the other bikes in power output, throttle response, ability to rev, or riding satisfaction. Never having ridden a Jaapanese-market VMax, which came without the VBoost, but after reading multiple stories about them, I'd say the addition of a Cobra 4/4 comes closest to approaching the Japanese market bike, with its lesser power.

I said it before, I'll say it again: nothing you can do to that Cobra 4/4 system is going to restore the power you lose from having it on your bike. No 'Stage 1' system for your carbs, no hacking-up your Cobras, fuhgeddaboutit. If you want 4/4 megaphones that make power, buy the UFO Quadzilla and a pair of earplugs, as they are ear-damaging loud.

Dozens of members have tried drilling holes in their stock exhausts in various locations: the collector boxes, and the megaphone plates, or have tried removing the megaphone plates and then drilled holes into the ends. All that does is make them louder. No extra power, just louder.

There have been members on-here with the Cobra slip-ons who have descended into the rabbit-hole in-search of the Cobra lost performance before your appearance and none of them have had success. The #1 guy who freely-offers his advice and who has built many a modified VMax, Sean Morley, has informed you that it's a useless endeavor.

I get it, you want to keep the system that came on your bike, whether it's the looks or the sound (to me, they sound like sitting on a flat rock in a wet bathing suit, and farting) or that you're $-down and want to find the magic panacea to restore the lost horsepower your beloved Cobras cost you. It's out there, next-to the Holy Grail. Don't you think that in the time since the Cobras were released, someone would have already discovered this?

It's your time to waste. By installing a stock system you can boost your horsepower by a considerable margin, and to my ear, the stock full exhaust sounds better than the Cobra anyway. Appearance versus function/performance, for most VMax riders, the latter is a higher priority. If someone gave me a Cobra system, I wouldn't install it on my own bike, I'd look for someone like you who is so-enamored of the appearance that they can overlook the gaping performance loss they cause.

I'll send you a stock VMax exhaust megaphone set, just pay shipping, so you can install a stock system, and see for yourself what you're missing in performance. They aren't pretty, but maybe after 'discovering' that unicorn of performance, you will admit that on a performance bike anything that robs you of why the bike was designed, marketed, and sold is just a poor modification. Unless form over function is your overriding goal, and the eye-candy is worth more-to you than the performance.

:bang head::bang head::confused2::confused2::hmmm::hmmm::whistlin:
:blahblah::blahblah:
 
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[emoji23][emoji23][emoji23][emoji23][emoji24][emoji24] apparently it’s not dead


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I made him an offer, let's see if he chooses to add the "13%" or whatever amount of power he's lost keeping the Cobras, by installing a stock megaphone system he can own for the cost of shipping.
 
Dear Fire Medic (Glove Puppet),

I have never seen so many words, pictures, garbage before that mean absolutely Zero......

You have contributed zero to this thread, absolutely zero.....

Not Interested in your opinion at all.....

Go and Troll elsewhere..... Perhaps try a Kindergarden somewhere, they might appreciate the pretty pictures.....

:ignore:
 
Sorry for your limited view, if someone offered me free parts to restore full power to my steed, I would think kindly of that.

I acknowledged your fascination for the appearance of the 4/4 system, coupled with the desire to not spend the cost of a replacement system. I like the looks of a 4/4 system myself, but I am unwilling to spend the money for a Cobra when it costs me significant horsepower.

My time on here has been fruitful in being someone who is willing to help others with any insights I may offer, based upon my personal experiences and ownership of VMaxes for the past quarter-century. I'm not a machinist, nor a professional mechanic, but I do have over a half-century of experience of mechanical 'fiddling-about.' There are many members who have similar levels of experience. I've bought and sold parts on-here, I've given-away parts to needy members, and I've been the recipient of the generosity of others. When things haven't worked, I've admitted such. I've posted tech information to share my experiences, to help others through my trials and errors.

If there is something that you can do to fix your Cobra's performance deficit, then get-off the keyboard, and do it! As is said, actions speak louder than words. Take me up on my offer of a free stock megaphone/collector exhaust, install it on your bike, and see if you aren't more-satisfied with the performance increase than you are with the looks of the Cobras, and their pitiful decrease in horsepower.

The referral to me as a 'troll' is laughable. You arrived here and decided to extoll the Cobra system, stating essentially the same thing time and time again. Yes, it looks 'pretty.' No it doesn't perform as-well as a stocker, and the only thing that will make it perform better to be as-good as a stock megaphone/collector/header system is to replace it. Sad but true. Have you bought a handful of jets, and tried to re-jet it yourself? Have you bought a commercially-available kit, and tried to see what results you've attained? "Less jaw-work, more paw-work" and then post-up your results.

The offer of a free stock megaphone system stands despite your name-calling. :clapping:
 
I have significantly more data but this is from the specific event that the cobra's where measured at that are in question. Some items of note which have remained consistent from event to event.
1 - The higher the mileage the more the HP that they typically make.
2 - There is no specific brand of full header that consistently makes more HP then any other.
3 - The Stage seven and Muscle jet kits make similar power.
4 - Slip-ons and Stock make similar power (though note at this even there was a supertrapp equipped bike that performed exceptionally well).
5 - The Cobra bike was not that far off from it's tune and the power difference between it and the next closest bike was huge! I am sure we've dyno'd another one at one time or another but I don't have the time to go through every dyno file I have and get you proof. You either believe it or not. No amount of research is going to make your wish come true. That isn't to say that some modification can't help bring some power back but you'll likely never reach where the average stock bike can even achieve.


From the 2008 Event all bikes were stock 1200 Vmax engines unless otherwise noted*. All testing was done June 22 2008 on Dynojet 250i in climate controlled room.
132 Huligan (Roark) – 1999 (I think)?, Kerker 4-2-1, Stage Seven. *High mileage (55-60k)
130 Kopperhead (Heath) – 1999, Marks 4-2, Muscle Jet Kit. *High Mileage (60-70k)
127 Morley – 2005, Kerker 4-2-1 Header Carbon Muffler (an optional muffler we could get from Kerker), Muscle Jet Kit
124 Logan – ?year, Kerker 4-2-1, Muscle jet Kit
122 Campbell – 1985, Holeshot 4-2 w/Muscle Big Gun Mufflers on a 4-2 full system, Muscle Jet Kit
122 Smith – 2006, 4-2 Holeshot, Dynojet Stage 1
120 Kent – ?year, Marks 4-2, Dynojet Stage Seven.
119/164 Huber – 2000 (I think), Kerker (no baffle), Muscle Jet Kit. *The 164 was with 40 shot of nitrous.
118 Warden – ?year, Supertrapp Slip-ons, No mention of jet kit?
115 Rowl – 1992, Kerker 4-2-1 Header with Hi Flow Carbon Muffler (an optional muffler we could get from Kerker), Muscle Jet Kit
114 Foust – ?year, UFO header (not sure if 4-1 or 4-2), Dynojet Stage 1
113/109 Frazier – ? year, Kerker 4-2-1, Stage Seven. *Interesting to note. He baselined his bike with stock airbox and K&N drop in filter and did a number of tuning pulls to maximize that (which is the 109 power). Then he installed the stage 7 jet kit and retuned. He was able to gain an additional 4 HP. This doesn’t match the advertised gains he was supposedly going to get (which we knew it wouldn’t). Don’t believe everything you read from guys trying to use these numbers to sell you their products. Get some independent testing done like we did here.
112 Bob W – ?year, 100% Stock
111 Dink – ?year, Kerker Slip-ons, Stage one (I think).
109 Foster – ?year, Holeshot 4-1, Stage Seven. Lowest HP of any full headered bike
96 Bush – 1985, Cobra 4-4 Slip-on Mufflers *Engine High Mileage (50k plus), No Jet Kit

Non Stock Engine and Non Vmax Bikes:
165 Morley 1500 – 1991, Custom build 4-2 Header, Flatslides (no filters). Highest HP at the event but a 1500cc build that I did with big valves, 11:1 Compression Ratio. The custom made exhaust system was built using the outer shells of the stock front pipes which are very large. It had some restrictive turns on the rear pipes and I don't really think it would have measured much higher than a regular full header.
130 Hall – 1986, Marks 4-2 Exhaust – Muscle Jet Kit. *brand new 1300 conversion we built for him. 1300 Venture Base Block, Vmax Heads with porting, Ross 12:1 Pistons, Overdrive Trans (runs were done in 4th gear because of this). The 121 HP was fresh off the trailer and break in procedure with his baseline dyno 3000 set to one of the milder power curves (don't remember which one). The 130 HP was after he left and went and rode it for another hour or so giving it some additional break in time and one change on the dyna (which added 3hp of the change).
120 Ryan – 1986 Fazer, 4-1 Header, Dynojet Stage 3. This is a 1000cc conversion and why the number is so much higher then the Rowl stock engine Fazer. A very fun bike to ride.
90 Swift – 2005 Softail, LOTS of engine work
77 Rowl – 1986 Fazer, 700cc Stock Engine, Kerker 4-1 Header w/Hindle Muffler, Dynojet Stage 3. The 52/77 HP Before and after some tuning effort. No changes other than messing with the jetting to get it set better and resolved a misfire with new spark plugs (which was the bulk of the power increase).
 

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I personally like the looks of the Cobra's and had a set on my bike years ago. Not sure I can find a picture. They just flat out don't perform. Some of that is the lack of scavenging and some is the small primary pipes that the stock tubes provide.

I have a number of headers and muffler combinations here and i'll repeat my offer. I will cover the cost of shipping to you these systems so you can do extensive dyno testing at your expense. The only requirement will be they have to all be measured on the same bike and on the same dyno with the only changes being the exhaust and jet changes. You will need to try and get each one as close as possible to the ideal 12.7-13.3 AFR ratios.

If you can provide that fair comparison data I MIGHT even help subsidize some of the costs.
I THINK I can come up with:
Cobra's - unmodified
Voodoo - Full System (4-1 and maybe even a 4-2)
Kerker 4-2-1
Marks Standard System 4-2
Hingle 4-1
Muscle Marks 4-2
Supertrapp Slip-ons

I'm not sure what others i can find? We'd ship one or two systems at a time and send the next once you have tested the sets i already sent.
 
As always Sean, very handy data/information..... Very much appreciate your help and support....

Absolutely not interested in shipping over an exhaust USA to Australia and I most certainly do appreciate the offer that both your self and Fire Medic have made........

I like to see and enjoy the beauty in the vast majority of VMax that I see and have seen...... I am gradually getting my VMax how I like it and part of that process is retaining and persevering with the Cobras which I like and enjoy....

Ideally it would be good to have available a direct comparison of the exact same stock, unmodified VMax, on the exact same dyno, between the standard rear mufflers and the Cobra rear mufflers. However we do not have this information available, maybe one day this will happen so that an exact figure can be identified......
 
As previously discussed and also based on my past personal experience and the information available to date, I am fairly comfortable continuing with the following stock standard VMax performance ratings and the use of the performance calculator to gauge any potential, future changes/modifications/developments.

Stock-Standard VMax Gen 1 (Total Wet Weight with rider = 850 LBS).
(Average Quarter Mile ET = 11.5 Secs). (Average Quarter Mile Terminal Speed = 116 MPH). (Quarter Mile ET and Terminal Speed taken from Haynes Workshop Manual).

As per the Performance Calculator:
AVG Weight 850LBS + AVG Terminal Speed 116MPH = Average Horsepower of 102.25.

With the weight being constant and gradually increasing the terminal speed, you get the following BHP increases:
AVG weight 850LBS + AVG Terminal Speed 117 MPH = AVG BHP of 104.90.
AVG weight 850LBS + AVG Terminal Speed 118 MPH = AVG BHP of 107.80.
AVG weight 850LBS + AVG Terminal Speed 119 MPH = AVG BHP of 110.40.
AVG weight 850LBS + AVG Terminal Speed 120 MPH = AVG BHP of 113.20.
AVG weight 850LBS + AVG Terminal Speed 121 MPH = AVG BHP of 116.05.
AVG weight 850LBS + AVG Terminal Speed 122 MPH = AVG BHP of 118.95.
AVG weight 850LBS + AVG Terminal Speed 123 MPH = AVG BHP of 121.90.
AVG weight 850LBS + AVG Terminal Speed 124 MPH = AVG BHP of 124.90.
AVG weight 850LBS + AVG Terminal Speed 125 MPH = AVG BHP of 127.90.
 
From an earlier member's post:
A friend and I had our max's dynoed today.

His is all stock 2002
stock jets,
stock air filter, stock exhaust
amsoil engine oil


Mine is a 1997
stock jets,stock air filter ,
Cobra pipe
15w40 rotella

he posted 117 hp/ 82 ft torque

me ... 100hp and 71.75 ft torque


Another post, by a member here, who happens to be the VMOA webmaster:

With the cobra 4into4 slip-ons, my dyno showed me at 98rwhp. Thats just pathetic! I pulled them off quickly to use Supertraps and was pulling near 120rwhp then.

There's a back-to-back on the same bike documenting a loss of almost 19%.

Another member posting:

I've seen two bikes with Cobras, and both had around 95bhp. That's a HUGE loss in power...

I hope that helps to quantify the Cobra Conundrum.



 
From an earlier member's post:
A friend and I had our max's dynoed today.

His is all stock 2002
stock jets,
stock air filter, stock exhaust
amsoil engine oil


Mine is a 1997
stock jets,stock air filter ,
Cobra pipe
15w40 rotella

he posted 117 hp/ 82 ft torque

me ... 100hp and 71.75 ft torque


Another post, by a member here, who happens to be the VMOA webmaster:

With the cobra 4into4 slip-ons, my dyno showed me at 98rwhp. Thats just pathetic! I pulled them off quickly to use Supertraps and was pulling near 120rwhp then.

There's a back-to-back on the same bike documenting a loss of almost 19%.

Another member posting:

I've seen two bikes with Cobras, and both had around 95bhp. That's a HUGE loss in power...

I hope that helps to quantify the Cobra Conundrum.





G`day Fire Medic,

Many Thanks for posting this, very interesting, relevant and helpful.....

If its not too much trouble please could you identify these particular posts so that I might find them myself easily and research them further.......

Thanks again.....
 
I searched under 'cobra power.' It gave me about 4 pp. of 'hits.' Happy hunting.


G`day Fire Medic,

Many Thanks for posting this, very interesting, relevant and helpful.....

If its not too much trouble please could you identify these particular posts so that I might find them myself easily and research them further.......

Thanks again.....
 
No Worries, looking forward to scratching around again.....

Appreciate the info, helpful knowing the search words you used....

:thumbs up:
 
With that info there is enough data from these different people getting similar results as we did, to validate the power loss compared to stock. To me this seems to close the loop on that part of the research.

All that remains is what kind of modifications can be done to regain some of that power. What might be interesting to understand is if any of those Cobra measurements had a set that were drilled out (which is a popular modification to do). I don't feel that drilling them out will do anything but add sound volume as their restriction isn't enough to hurt power.
 
I am trying my best to try and keep an open mind about this whole issue.....

There is enough data/information, mostly personal opinions one way or another, that an individual could cherry pick comments/statements to build a case either way, both for and against the Cobras......

The only correct method would be to use the same stock unmodified VMax, standard exhaust, same independant dyno, compare the readings with the stock mufflers versus the readings with the 4 into 4 cobra mufflers. This would confirm/deny any performance difference and quantify the value.
Nobody seems to have done this and the data is simply not available....
 
I am trying my best to try and keep an open mind about this whole issue.....

There is enough data/information, mostly personal opinions one way or another, that an individual could cherry pick comments/statements to build a case either way, both for and against the Cobras......

The only correct method would be to use the same stock unmodified VMax, standard exhaust, same independant dyno, compare the readings with the stock mufflers versus the readings with the 4 into 4 cobra mufflers. This would confirm/deny any performance difference and quantify the value.
Nobody seems to have done this and the data is simply not available....
I don't think there is any data to cherry pick that confirms any performance gain. It all points toward performance loss.
True, does not seem to be completely quantified, however, if Sean is saying it takes a 10 percent loss that is enough quantitative research for me.

Sent from my SM-G360V using Tapatalk
 
G`day Eugene,

Thats a very good and fair post, I hear what you are saying and I tend to agree with you.......

I also think there is enough information, good, bad and ugly on this thread for people who are genuinely interested in the Cobra 4 into 4 slip ons, for whatever reason, to make up their own minds about them.....

Certainly we are all creating a good source of reference for the future for those with a genuine interest in the Cobras.....

Hopefully moving forwards, more meaningful information will be added, which will continue to help things along......

Enjoy the Ride, Ride Safe.......
 
Quote:

last year bought a 00 vmax with 10k with a 4-2-1 Kerker exhaust. i put on Delkevic front header, and rear stock header and put on cobra slip on. I just like the look of dual exhausts(4 pipes). Hear is the results of dyno before and after, i am guessing it's been rejetted with the Kerker exhaust. i did not rejet with cobra ex. Had problem with left rear slip on, only go on 1/8 in. Cobra said i doing something wrong.lol. After reading what i can do to increase hp on a stock motor does not look like i can do much, KN filters,carb syn?
uhm00000.gif




Quote Ref and Link Below:
http://www.vmaxforum.net/showthread.php?t=22440&highlight=cobras

See Attached Dyno Readings:

Same Dyno. Same VMax. Stock VMax Engine.

Kerker 4 into 1 Full Exhaust = 112.92 BHP. (Switched to Cobra 4/4 Slip Ons) Cobra 4 into 4 Slip Ons = 109.11 BHP.

Note: Dyno Sheets attached to original Vmaxforum thread listed in Red above.
 
From an earlier member's post:

A friend and I had our max's dynoed today.

His is all stock 2002
stock jets,
stock air filter, stock exhaust
amsoil engine oil

Mine is a 1997
stock jets,stock air filter ,
Cobra pipe
15w40 rotella

he posted 117 hp/ 82 ft torque

me ... 100hp and 71.75 ft torque


I hope that helps to quantify the Cobra Conundrum.




The above Quote from Fire-Medic Ref: Post # 90 of this thread.

The above Quote is generated from the original post highlighted below in "Red" Ref: Post # 1.

http://www.vmaxforum.net/showthread.php?t=38677&highlight=cobra+power

Please view post # 5 in particular, from the above "Red" post for a more balanced view..... ref: Damon.

I quote:

"Not really a fair comparison being that they are two different bikes. Run a dyno test on the bike with stock set-up then switch to the Cobra's?

I have seen Cobra's dyno around 112 RWHP"
 
The kerker-cobra dyno swap I am not sure how good an indicator that is. It looks like they only made one pull for each? It can typically take 5-8 back to back pulls to read a full potential output.

I would highly suggest you just swap over to a full header or other slip-on on your bike even without dyno and got try it out. All you're going by is conjecture right now.
 
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