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Noob with exhaust questions.

Old 08-25-2011, 08:49 PM
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Noob with exhaust questions.

So one of my buddies that first got me interested in riding came by to show me his new bike/what all he's done to it. It's a ZX-14, so needless to say its pretty badass already, but he showed me where he completely removed the muffler and had it straight piped to the point of where it would throw flames.

Now my question: has anyone ever done this with their VTR? I feel like mine is already so friggin' loud that straight piping it wouldn't make it ridiculous or anything. I live in Oklahoma, so I don't have to pass any sort of db test.

I can see where this might cause a problem with the fuel/air ratios in the engine. My friend has a Power Commander, so his ratios took all of 10 min to adjust.

Comments, questions, and thought always more than welcome!
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Old 08-25-2011, 09:28 PM
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Zero backpressure is no bueno. It does sound cool, but it's louder than loud. Like, you're relieved when it turns off. Kinda like when you walk out of a club and the world comes back together.

Personally I wouldn't want to try to touch the tuning the carbs on these things with strait pipes... you can get it to run, but it won't run near it's potential.
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Old 08-26-2011, 12:04 AM
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I can't say I've ever walked out of a club relieved lol, I'm in college after all.

But on a serious note, my goal is to dump the exhaust before the rear wheel, kinda like the Buell Firebolt. Personally, I like the look of having a short exhaust and I'm sure it lightens the bike up significantly.

As to the sound level, I've been wearing headphones and I just ordered helmet speakers. I like my music loud enough that I can barely hear my exhaust. I used to work in car audio and my truck has hit over 130db, so I'm gonna go deaf anyway.

On that note, invest in hearing aids, my generations is gonna need them.

But like I said, I'm more concerned with the engine performance than the sound. is there perhaps a way to get the look I'm shooting for while still maintaining performance?
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Old 08-26-2011, 06:47 AM
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ive never had mine dyno'd so im not sure, but i cant tell a difference in power and yes it is pretty freaking loud... Name:  2011-07-28_10-55-26_777.jpg
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Old 08-26-2011, 08:53 AM
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you need some amount of backpressure in order to get the best performance out of your motor. If not, all you're doing is making noise and losing power. it may sound bad-***, but it won't perform. Why do you think racers run exhausts. If they could get more power without them, you can be sure they would be running them that way. I would challenge your buddy to dyno his bike before and after and see the results. I'd bet that he's losing power even though he adjusts with the power commander.
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Old 08-26-2011, 09:36 AM
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A/F will go out the door, and you will lose hp even if you re-jet, it's not optional, it's a fact... And while a big IL4 is loud with no exhaust, a V-twin is LOUD on an entirely different scale... But go ahead and try it... Just make sure you can reverse the change...
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Old 08-26-2011, 09:58 AM
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See I'm from the car world where backpressure is a dirty word and anything that flows faster is better, to the point where people straight pipe and dump on the strip to get their pipes to actually flow faster than a straight pipe. (I know that sounds impossible, but I've literally seen the test results.)

I guess I'm confused as to why this doesn't apply to the 'Hawks. Is it because they're carbureted? Also, most of the cars I've seen on the strip are either blown or running NOS, could that be the difference?

My goal is to have a good performance exhaust that doesn't really show. I'm planning on a SharkSkinz lowe, and the exhaust just barely coming out of it.

I like the look of the Firebolt exhaust, and those bikes have a sort of custom built muffler that sits underneath the trans and engine and dumps to the sides before the rear wheel. The muffler is circles in red in this picture.



Would it be possible to fit some sort of custom built muffler under the bottom of the bike and still make room for the SharkSkinz lower?

I'm trying to figure this all out before I purchase a lower because I have a nagging suspicion this type of exhaust wont fit inside it.

Should I look into a custom type muffle as well as a custom lower that are both built to fit the bike and each other while still looking awesome?

I can do fiberglass fabrication due to my history in the car audio field making sub boxes, and I have a friend who's dad owns an exhaust shop, so anything that is possible in this situation we can probably do. I just wanna know what you guys think before I start ripping the exhaust out and buying new pipe muffler components.
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Old 08-26-2011, 10:56 AM
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in short, no. there's not enough room. I hate to tell you, but from my street car hot rod days, even they need some amount of backpressure to operate at optimum. Sometimes though, that's caused by twists and bends in the exhaust, and the length of it too. Go dyno your car, then yank the exhaust off and dyno again, then put a quality tuned exhaust and do again. that will give you the real story. It's true that straight pipes may be better than a heavily restricted setup, but a good flowing one with proper restriction will always outperform. Tuning any engine is always a balancing act of many variables, much of which are beyond my feeble mind.

if you like the looks of the buell, you should probably just dump the hawk and buy one. it would be cheaper in the long run. They are cool bikes in their own right, and I have one in my garage.

Last edited by Old Yeller; 08-26-2011 at 10:59 AM.
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Old 08-26-2011, 11:00 AM
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Others will probably chime in with better explanation, but you touched on it with the carbs of these bikes. With cars, especially modern ones, they have computers that adjust for lean conditions caused by free flowing exhaust... and even then you sometimes have to get a bigger fuel pump and injectors that can deliver more to the cylinders. With carbs, you have to try to do this on your own, across the entire RPM 10.5K rpm range without flats spots or running too ruch or lean.

Like yeller said... companies invest ridiculous amounts of money and effort into R&D on their race bikes. If they could save weight or gain performance by ditching the exhaust they would have done so long ago. The Moriwaki bikes use 2 full length cans on theirs.

You may lose a little performance if you run a setup like kj4kym has, but it could be worth it for the uniqueness/style factor... that thing looks pretty cool.

Buell designed their whole bike around a centrally located, low center of gravity, so it would be hard to replicate one that nicely with a bike not designed for it.

Take all of my opinions with a grain of salt... personally I like the huge jugs hanging off of these bikes... but with your fiberglass/exhaust connections go make something freggin' awesome!
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Old 08-26-2011, 12:49 PM
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ok....so how many of you guys went immediately into the gutter with that last comment??? LOL
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Old 08-26-2011, 01:12 PM
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I might get a buell eventually, but I like the hawk as a starter bike.

I found a website that sells individual muffler and exhaust parts, so I'm probably gonna order a few of their products and see what I can rig up for a system. My goal is to have some sort of working prototype by thanksgiving and a final product by Christmas.

In any case, thanks for everyones input. At least now I have an idea of what needs to be done and how realistic my goal is.
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Old 08-26-2011, 01:32 PM
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Originally Posted by Big Shepp View Post
See I'm from the car world where backpressure is a dirty word and anything that flows faster is better, to the point where people straight pipe and dump on the strip to get their pipes to actually flow faster than a straight pipe. (I know that sounds impossible, but I've literally seen the test results.)
Even in the car world there is such a thing as not enough back pressure. It happens if the car "over scavenges" and pulls unburned gas into the exhaust during the valve overlap stage.

Not common, and far less common with EFI than carbs (even with motorcycles, EFI allows you to not worry about back pressure)
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Old 08-26-2011, 06:50 PM
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Originally Posted by Old Yeller View Post
ok....so how many of you guys went immediately into the gutter with that last comment??? LOL
I'm always in the gutter when I see a pair of well placed cans ready to be ridden hard.
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Old 08-27-2012, 06:07 PM
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I have no idea if you can get it, but you should look up the 2001 honda NAS concept bike. It was essentially a screwed over superhawk, but it did come with an under engine exhaust can! I think it would look badass on the hawk, let me know if you find anything!
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