Cobra Exhaust Tuning Recommendation.

[Fire-medic]

A good-looking bike, the P-40 Flying Tiger theme is a popular one for bikes, one I've seen before on multiple bikes. The Cobras look good but no-way am I gonna reduce my HP for looks.

 

[lilredrooster]

Many Thanks FM, glad you like my version...
I hear what you are saying, I didn`t specifically go looking for an exhaust to reduce HP, I like the look, sound, design & the price enough to install the Cobras. Sucks that the manufacturer struggles to match the performance of the stock system. Still hoping to pick up that final couple of HP to pull even with stock, if I don`t find any more HP so be it, I have enjoyed playing around with it and will continue to be very happy to keep the Cobras anyways....
The best thing about the VMax is we all get to build and enjoy our own unique individual VMax versions, it would be a very sad/mundane life and forum if we all liked exactly the same thing....
Ride Safe.... Enjoy the Ride.....

 

[lilredrooster]

 

[lilredrooster]

 

[lilredrooster]

There are many Cobra 4/4 Haters/Bashers around, often quoting power losses of 15 BHP to 30 BHP.

There are many Vmaxxers that like the look/design/sound of the Cobras but are negatively influenced by such large power loss claims and the herd mentality.

Why not challenge the herd mentality and the perceived power losses being quoted, why not consider a more balanced/alternative viewpoint, why not try and establish more accurately what the power losses actually are?

In my actual experience and also with the experiences of a few others it would seem that the actual power losses are in fact much, much smaller than the 15 HP to 30 HP losses often being quoted by the herd........ The actual power losses would appear to be much closer to around 5 HP, perhaps slightly more, perhaps slightly less.....

Care needs to be given that apples are being compared to apples here, the Cobras are a low end, budget slip on exhaust using the original Yamaha front headers, it is not a full performance exhaust system and should not be compared to one, generally slip on rear mufflers do not show gains over the stock Yamaha rear mufflers which are very well designed and very efficient for a stock exhaust of this era.

 

[lilredrooster]

The VMax is an old school, old fashioned muscle/cruiser with unique hot-rod/retro styling, in 1984 it was also right up there as a competitive high performance bike, today not any more.....

The VMax is one of the most, enduring, endearing and customized motorcycles ever built. As VMax enthusiasts, we are very fortunate to be able to access an almost limitless supply of customized parts worldwide to be able to transform our bikes into something that more suits our own personal needs and goals.....

I have both owned and enjoyed riding and wrenching on my Vmax for many years, my VMax meets my own personal needs and goals and I am very happy with it, it meets my own personal approval and that is all that matters.

Like the vast majority of VMax and muscle/cruiser owners, my VMax is used primarily for street/road use, the vast majority of the time when riding I am not riding right on the edge, scraping my knees on the corners or constantly pegging the rev-counter to the redline, it was not built for that, it is a street-cruiser, not a circuit/road-racer, the power it makes is more than enough to meet my personal needs...... As is commonly the case, it is often not the bike that makes the difference it is the rider.....

If I wanted a sports-bike, super-sports-bike, race-bike, drag-bike, road-racer, canyon-carver, dirt-bike, super-bike, performance-bike, or any other kind of bike I would buy one or build one, I wanted an old school muscle/cruiser and I got one of the finest, I choose the VMax, I also choose the Cobras, very happy with my choices so far......

For those out there that do not like my choices..... Tuff..... Get over it.....

 

[one2dmax]

Where are you getting a 30 hp loss claim? I am stating 10% which is about 10-12

 

[jdeitz1979]

If you like the pipes that’s great! They look great too!! Maybe some of us should lay off the loss reiterating and let ya be, just saying. You get the idea though, if ya want a few ponies back, run a kerker or what have you....all been tested and documented on what works for our bikes.

It’s a great looking bike, hope you enjoy it this season, and ride safe.

 

[lilredrooster]

If you like the pipes that’s great! They look great too!! Maybe some of us should lay off the loss reiterating and let ya be, just saying. You get the idea though, if ya want a few ponies back, run a kerker or what have you....all been tested and documented on what works for our bikes.

It’s a great looking bike, hope you enjoy it this season, and ride safe.

G`day JD, Many Thanks for your thoughts and the compliments much appreciated, winter time here in Australia, we get the majority of rainfall here in the next 3 months so bike is in hibernation mode until spring, enjoy your current riding season, enjoy your ride......

 

[lilredrooster]

Where are you getting a 30 hp loss claim? I am stating 10% which is about 10-12

Forget about the false claims from the Haters/Bashers they are not accurate and totally irrelevant, what is important are the facts..... I think we can both agree that any Hater/Basher claims north of a 15 RWHP loss is fantasy-land.....


I think we can both agree that any HP loss from the Cobras on a given stock engine, stock exhaust VMax is somewhere between 2 RWHP and 12 RWHP...... Now we could call it 7 RWHP and call it quits..... Ha Ha....

I think we can also agree that there is always going to be some variation between the performance of groups/multiples of stock engined stock exhaust Vmax`s...... Maybe as much as 8 RWHP swing between the best and the worst of a large bunch of similar equipped VMax....

I have tried my best to keep an open mind on the Cobras performance, I have provided plenty of related data on this thread and also been testing and tuning my own Vmax/Cobras combination and adding that data too.

There is data added to suggest another forum member losing 4 RWHP by substituting a Kerker 4/1 for Cobras with dyno sheets as proof....

There is data added to suggest another member losing multiple rolling races with a modified VMax by 2 bike lengths which would suggest a negligible loss if any....

The results I have found to date on my own bike suggest a power loss of close to 5 RWHP with a slipping clutch as documented.


On the other hand you are suggesting a 10% 11 RWHP loss (I assume you are rating a stock engine, stock exhaust VMax at 110 RWHP).

I appreciate and respect that you have lots of VMax experience, but where is your data ???
What have you got to post to support your claims of an 10% 11 RWHP loss ???

 

[thunder]

Nice looking bike! I have a 2003 and used to have cobras as well. There was no performance increase, just louder. I ended up getting a full exhaust system 4 into 2 and that made the biggest change in power. Ironically for me, I had to put smaller main jets in,147.5. The bike ran way too rich before. Elevation 1900 feet.
It's hard to beat a well tuned stock bike with some minor tweaks of the carbs. Adjusting the air fuel mixture screws and shimming the needles will give good results. Using either the stage 1 or stage 7 needles made the air fuel mixture too rich. Unfortunately I learned the hard way by trial and error after getting the bike dynoed, I went back to the stock air box and my days of messing with it are over.

 

[Vinmax]

The Cobras are a good looking slip-on exhaust, and they sound pretty good to some people.
The main problem is that they are a 'SHIT' design. Anyone, that knows, anything, about exhaust design knows that on regular internal combustion engines, there's a very distinct benefit from helping to 'pull' the exhaust gases out of the cylinders when the exhaust valves open.

The pistons and of course the expanded gases (after being burned) on the exhaust stroke want to really get the hell out of those cylinders. They do as the piston comes up in the bore. They also want to travel very fast down the exhaust system and find relief out in the open air.

The theory behind the collector tube on an exhaust system is that you want to use the vacuum created by, and left behind, by the last cylinder that was pumping out exhaust gases.
This is a definite and proven exhaust system design principal. This vacuum helps draw and evacuate the exhaust system so the new gases from the current exhausting cylinder don't have to 'push' so hard to get the gases out.

The Cobra design;
The Cobras eliminated the collector pipe. They've eliminated the vacuum created in the rear of the exhaust. They've eliminated the 'help' needed to get the exhaust gases 'sucked' out of the exhaust.
They've basically eliminated a great and proven design and replaced it with semi-free flowing separate pipes.

So in eliminating the proven, standard, exhaust design............ they've also help to drop power in the bikes engine.
No getting around this.
No jetting will make up for this.
No airbox mods will make up for this.
No drilling the Cobras will make up for this.

They simply are a poor design (regardless of looks), and nothing will make up for them eliminating the suction pulse 'boost' that proper exhaust system designs strive for.

Whoever designed the Cobras went for looks only. Sound only. NOT for performance.
Very simple concept here.

I've seen this on aftermarket (I mean the poorly designed aftermarket) Harley exhausts. The ones where they eliminate the crossover tube that the stock bike has.
Yep, results in loss of power........ but the owner just LOVESSSSSSSSSSSS the loudness they gain and the performance they 'think' they've gained.

No debating dyno numbers here. Sound does not equal actual HP gains.

SuperTrapp = Good. Collector is in the design
Dam = Good. Collector is in the design
Dale Walker Holeshot = Good. Collector is in the design
Most other slip-ons with collector = Good. Collector is in the design
STOCK Vmax exhaust = Good. Collector is in the design
Cobra = Not Good (*not good; if... you're looking for stock horsepower levels or any sort of increase at all) HP loss. NO collector in the design. NO scavenging help for the engine. Again, HP loss as it typical of any exhaust on most bikes and cars for that matter, where you put on a system that takes away the benefit of exhaust scavenging (the vacuum pull in the exhaust system). Taking away the help of 'exhaust scavenging' is a great and simple way to reduce horsepower and torque.

Vinnie

 

[lilredrooster]

If you take the time to read the threads, you will see that there are examples including a well respected member on this site, of stock Gen1 Vmax running four separate slip-ons with original front headers (Not Cobras), that are running equivalent and better 1/4 mile times and speeds as a stock VMax = zero performance loss with no collector and no scavenging......

"This suggests that the problem is not related to the lack of scavenging or lack of collectors".

Everybody is entitled to their opinion, in my experience with the same VMax and the Cobra exhausts I found I lost 3-4 BHP, but when I did the testing it was not in ideal conditions for weather and track conditions and I had audible clutch slip or loss of traction at the top end. I would like to think that given more opportunity I could have improved the results.

You can talk all you want about collectors and scavenging, instead of talking about it, build it and test it, use the same bike, show the test results difference.... Cobras with scavenging, Same Cobras without scavenging, show the difference and prove it.......

If you like the look of the Cobras, like the price, like the sound, then enjoy them......

 

[Vinmax]

If you take the time to read the threads, you will see that there are examples including a well respected member on this site, of stock Gen1 Vmax running four separate slip-ons with original front headers (Not Cobras), that are running equivalent and better 1/4 mile times and speeds as a stock VMax = zero performance loss with no collector and no scavenging......

"This suggests that the problem is not related to the lack of scavenging or lack of collectors".

Everybody is entitled to their opinion, in my experience with the same VMax and the Cobra exhausts I found I lost 3-4 BHP, but when I did the testing it was not in ideal conditions for weather and track conditions and I had audible clutch slip or loss of traction at the top end. I would like to think that given more opportunity I could have improved the results.

You can talk all you want about collectors and scavenging, instead of talking about it, build it and test it, use the same bike, show the test results difference.... Cobras with scavenging, Same Cobras without scavenging, show the difference and prove it.......

If you like the look of the Cobras, like the price, like the sound, then enjoy them......

With all due respect, I don't have to 'build it and test it' to know that when you remove the scavenging, you wind up with less power. Yamaha already did that. And they do that all the time. That's why all their exhausts are not just pipes right out of the exhaust ports with no crossovers or scavenging systems built in.

Some people that are passionate about some kind of 'lacking' exhaust can try all kinds of things (including using the weight loss associated) with a poor exhaust design to try and equal or even better to some extent the 1/4 mile times. Does not prove that they did anything to add power to their bikes.

For example, If I jet my bike crappy, or remove the efficient design of a scavenging exhaust, of course I will lose power. If I add Cobra's, yes, of course I will most definitely lose power and midrange torque, and the general fun of riding the bike.
But then if I got (rest in peace....) Jay Gleason when he was riding/racing to ride my bike and get a better 1/4 mile than me or most anyone out there on my bike, it does not prove that I made any gains. It's just me figuring a better way to try and prove my point by comparing apples to oranges.
And I didn't make any real advantage to my bike,,,,,,, I simply lost a bit of weight on the bike and got a wayyyyyyyy better rider than myself to get that bike down the 1/4 mile faster.
*that's why nothing proves more than a dyno and back to back runs with different mods. It takes away the 'perception' of seat of the pants feel and weight loss of the bike (or rider).

I'm not really understanding where you said;
'If you take the time to read the threads, you will see that there are examples including a well respected member on this site, of stock Gen1 Vmax running four separate slip-ons with original front headers (Not Cobras), that are running equivalent and better 1/4 mile times and speeds as a stock VMax = zero performance loss with no collector and no scavenging......'

You are mentioning that someone tried different slip-ons. But you said 'Not Cobras.' Well yes, most slip-ons (if not all) do in fact have collector systems built in. Some of the ones I can think of off hand are; Dale Walker's Holeshots, Damn exhaust slipons, Supertrapps, Delkevic, Kerker, etc. In fact, I'm having a hard time finding any other one (other than the Cobras) that 'don't' have the built in collector. These all have built in scavenging collectors before the pipes let the exhaust gasses into the muffler section. That's why they all work very well compared to the Cobras.
So I'm not too sure what you mean. But if you check it out, you'll see that the slipons that are available for the first gen Vmax all come with the proper collector/scavenging built in. All, of course for except the Cobras.

Please read up on exhaust systems. Cobra's, when discussing exhaust designs, are not a good exhaust.
They cut efficiency, cut power, cut torque. Same with any Harley exhaust that gets rid of the crossover piping. And any other exhaust system out there that 'cheaps out' and gets rid of the engineering and scavenging effects just to look good or sound loud.

If you want the look, the noise, the weight loss, then go for it. But you can't and won't convince anyone knowledgeable about exhaust design that they are some sort of good exhaust as far as making power. They rob some efficiency from the exhaust and that will most definitely show up on the dyno and in 'seat of the pants' feel............. pure and simple.

Yamaha, and all the slip-on makers out there (except Cobra) don't just have extra pipe laying around that they decided to use to make exhaust collector systems with. It must be a real pain in the ass to design a proper exhaust and they don't just do it for the fun of it. They do it because it works. It works well. And it's engineered correctly. Cobra decided not to. They went for the looks/sound only and didn't sweat the power/efficiency stuff. Maybe they thought the Vmax had more than enough power and no one would care? Not too sure about that one. We'd have to call up the engineering team at Cobra and ask why didn't they put a darn collector on that nice looking exhaust system.

Again, I'm not knocking your choice of exhaust. I love the look myself. Before I got my Vmax back in '01, I was thinking about getting them also. But they I learned about the slight inefficiency and slight power/torque loss and decided against it. But that's just me.

Hell, I'm still on my stock system! I love the look and the smooth powerband. I mean, I rejetted the bike and optimized it for my altitude, and I know there's more power there if I go to a full header and exhaust design system, but I'm happy with what I have now. And someday I'll probably go for a slip-on when I find the one I'll really be happy with (I used to use SuperTrapp on my old '88 Vmax).
So again, I'm not knocking you at all (I mean not at all), for you choice on exhaust. I'm just discussing that the Cobras design will lose just some power and torque and there's no way to explain it otherwise. It's factual and proven. And we know why also. It's just through exhaust design knowledge that we know 'why' they lose some power/torque. Not just opinion.

 

[Fire-medic]

Oh no, not again!

Our smilies are limited. Where's the one I want?

Choose-one... .

https://www.google.com/url?sa=i&url=https://giphy.com/explore/beat-a-dead-horse&psig=AOvVaw2BkGTvGH9YMndpgd6BpCpk&ust=1593180641549000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCJD2y8ySneoCFQAAAAAdAAAAABAD

 

[desert_max]

Oh no, not again!

Our smilies are limited. Where's the one I want?

Choose-one... .

https://www.google.com/url?sa=i&url=https://giphy.com/explore/beat-a-dead-horse&psig=AOvVaw2BkGTvGH9YMndpgd6BpCpk&ust=1593180641549000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCJD2y8ySneoCFQAAAAAdAAAAABAD

OMG! Did I ever get some laughs from that page…

 

[Vinmax]

LOL! I forgot to add this link to my reply......... again............ about why the Cobra's are, ummmm, well,,,,, ok ok, here ya go;
https://www.quora.com/Why-cant-some-people-learn-simple-things

 

[Fire-medic]

I can see someone going for Cobra 4/4's on the basis of looks, but don't expect them to perform like a stock system, making an equivalent amount of HP and torque because they won't. Like the attractive woman who's just no-fun to be-around, "high-maintenance" some call them, after awhile, you realize that 'looks aren't everything.'

 

[Vinmax]

Great vid with a practical explanation of how it all works;


Collectors = GOOD! (power & torque = more fun and smiles))).
Cobras = no collectors = Bad (bad for max power that is. I will admit they do definitely look good and sound ok also).

 

[VMAXXIMUM]

That was a great video, thank you.