Cobra Exhaust HP Loss Explained, Please?

[lilredrooster]

 

[one2dmax]

The reason I am offering this to you is so you have a real world experience yourself and not repost up other peoples experience trying to justify that these aren't the worst performing system out there. I think if you actually had a chance to ride the bike with the full header you'd truly understand why they suck.

 

[VMAXXIMUM]

Sean Lilredrooster's vmax drive is a little different than most of the rest of us. He likes the look and doesn't mind being a few bike lengths or so behind a stock vmax. I have a question for you Lilredrooster. If you were buying a full system new, would you still put your money on the cobra's?

 

[lilredrooster]

The reason I am offering this to you is so you have a real world experience yourself and not repost up other peoples experience trying to justify that these aren't the worst performing system out there. I think if you actually had a chance to ride the bike with the full header you'd truly understand why they suck.

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.....

Below is a link to another thread which goes into more detail....

https://www.vmaxforum.net/threads/cobra-exhaust-tuning-recommendation.46778/

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]

Sean Lilredrooster's vmax drive is a little different than most of the rest of us. He likes the look and doesn't mind being a few bike lengths or so behind a stock vmax. I have a question for you Lilredrooster. If you were buying a full system new, would you still put your money on the cobra's?

G`day VMaxximum,

Very good post, enjoyed reading it and agree with your comments....

First up, care needs to be given here that apples are being compared to apples, 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.

Back to your question: If I was buying new slip on mufflers to connect to the original yamaha front headers for my Vmax, of all the slip on alternatives I have seen to date I would buy the Cobras again in a heartbeat. Originally I believed that I was also buying a power loss of maybe 15 HP +++, now I believe I have a power loss of under 5 HP (Still hoping to reduce this further).

Back to your question: If I was buying a new full performance exhaust system (I am not in the market for one, plus, there might be several I have never seen) I would be looking to buy the UFO Quadzilla system or the Voodoo equivalent depending on the price/quality of the manufacturers.

Comparing apples with apples on costs of the above:
Quadzilla full performance system = $1200 USD with $200 USD Shipping to Australia. (Star rider perf, ebay) plus you might need the additional sound baffles for the street at $200 USD extra inc Shipping.
Cobra 4/4 slip on mufflers = $ 460 USD with $ 65 USD Shipping to Australia.
(Add Australian Import Duties to all of the above, then add 35% extra to convert to Australian Dollars)

It is also worth mentioning here that is just the start of it with the UFO System!!!!
With the Cobras you can bolt them on and drive off.
With the Quadzillas you will need a stage 7 jet kit or equivalent & air-filters maybe $400 USD, then maybe tuning/dyno time.... No idea what if any gains you might see with the Quadzilla with and/or without the street sound baffles?

 

[lilredrooster]

Sean Lilredrooster's vmax drive is a little different than most of the rest of us. He likes the look and doesn't mind being a few bike lengths or so behind a stock vmax. I have a question for you Lilredrooster. If you were buying a full system new, would you still put your money on the cobra's?

G`day again VMaxximum,

Very good post, enjoyed reading it and agree with your comments....

I have replied to your question on buying an exhaust on a previous post, just wanted to reply to the broader comments that you make in your post.



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 the 30 HP loss claims? I state about 10% or about 10-12 rwhp

 

[lilredrooster]

Where are the 30 HP loss claims? I state about 10% or about 10-12 rwhp

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 and the other thread titled Cobra Exhaust Tuning Recommendation. See Link as follows:
https://www.vmaxforum.net/threads/cobra-exhaust-tuning-recommendation.46778 I have 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 ???

 

[Fire-medic]

Oh, oh, stand-back! Sean's probably got more real-world personal experience than anyone else on here, posting regularly. That includes strip time and development time on a dyno. To challenge that database (which is a living, breathing computer-savvy guy able to document his achievements) is not necessarily going to do anything but try his patience. I already sense he's reached the limits of his patience w/the O.P. It will be a happier time on here if you drop the 30 HP-down statement, and just say, "I like the looks, I like my bike," and let it go at-that.

My bike, which I've owned for 26 years, did just-under 110 RWHP on a Dynojet dyno and from the library of roadtests I have the range of RWHP results is 106-118. That's quite a range. Put a Cobra on that lower-end bike, and you're down-to ~95 RWHP. Put one on the higher-end bike, and you're at the probably median RWHP reading of 107-108.

Japanese manufacturers are well-known for putting a set of hot cam(s) into their first-year bikes to generate some impressive numbers and then back-pedaling them for subsequent model years. My stone-stock first-year FZR1000 5-valve Genesis (non-EXUP) is proof of this. The 1987 model-year FZR1000 bike (a no-show year for the USA version of the VMax, because the warehouses had a backlog of 1986 VMaxes during 1987 after a defied all odds production run of 8800 1985 introductory year VMaxes, and a much-lower 1986 model year sales number sold in the USA) in the road tests of the day achieved a whopping 122 RWHP, and into the 10's at the dragstrip. The 1988 model year bike got a different set of cams, made a much-more modest 106 RWHP, but because they gave a cam grind which actually helped where most riders spend the majority of their time, the bike made 20 more HP in the middle of the rpm range. This proved to be much-more useful to the average rider, and very apparent on the street, as the roll-on was much better than the high-HP prior year 1987 model.