Exhaust Bypass

[xTomKx]

A while back I had the exhaust totally off my 04 vfr. It was late at night but I had a couple of beers in me and I couldn't stop myself from starting it up to hear how she sounds without the cans.

I only had the bike running for a short time and did not rev it up much, but she sounded awesome. Idle was kind of like a small block v8. Nice and deep tone. When I slightly reved it up the bike sounded mean.

So is anyone running without the exhaust?

My idea is to incorporate a bypass into the exhaust. I'm not sure if I'm going with a flip valve, permament bypass, or a total removal of the exhaust. If I could get rid of the exhaust totally it would probably shave close to 50lbs of the bike but I like the way the stock pipes hide my license plate.

Backpressure should not be much of an issue since the bike has a cat.

Any suggestions?

[timmythecop]

you will find that under load, it will sound like poop. And run like poop.

Listen to the japanese fellows who wear white lab coats.

[DaveM]

you will find that under load, it will sound like poop. And run like poop.

Listen to the japanese fellows who wear white lab coats.

I like the idea. A moto gp style shorty would be super easy to fabricate - something like the one Toro did for his bike. Don't know about the sound under load, but just sitting in the garage...... :unsure: - sounds awesome. The running like poop problem (if there is one) could be easily fixed with a PC. The real problem on a 6th gen - take off the cans and you have two huge empty cutouts under the seat.

[FotoMoto]

a total removal of the exhaust. If I could get rid of the exhaust totally it would probably shave close to 50lbs of the bike but I like the way the stock pipes hide my license plate.

No, you'd lose about 25lbs at most; significant but no where near 50.

Now ask yourself, "Self: this is so easy and simple, why isn't everyone doing this?".

[V4 Rosso]

I'm not sure if I'm going with a flip valve, permament bypass, or a total removal of the exhaust.

Any suggestions?

Get rid of the O₂ sensors and replace them with some tubing that goes straight to you ear canal. You have the nice loud pipe sound and it keeps your neighbours (and traffic) happy.

[xTomKx]

Most aftermarket exhaust muflers are straight through design with fiberglass which should hardly create any backpressure at all, much like an open pipe. The cat should provide enough backpressure where the powerband would not shift too drasticly. Therefore I don't see a reason why the bike would run like poop.

I'm not too excited about the way the bike looks without the cans. Maybe I could reduce the weight by getting rid of the exhaust piping and leave the cans in place or at least half of the cans.

Does anyone have a stock exahust hanging around they could weigh?

[Baileyrock]

So is anyone running without the exhaust?

Any suggestions?

I hope not, please Don't do it or at least sell your VFR before pissing off everyone with some insanely loud exhaust(can you say HD with straight pipes). :idea3:

Extremely loud exhaust on any brand of bike only hurts our entire sport, it will only lead to further strict Laws & regulations. Many race tracks are either being closed down because of noise or are having to meet Db limits. Many classes at the local oval track are now required to run mufflers and I don't see that as a problem if it will let the sport continue and everyone has to run one and meet a db level.

I had to be under a certain db level when I road raced cars with SCCA and I also have to at bike track days, that's all fine with me if it lets me keep doing what I enjoy.

People who choose to run anything w/o exhaust will only hurt my future chances to enjoy it and that pisses me off!!!! :laugh:

[xTomKx]

So is anyone running without the exhaust?

Any suggestions?

I hope not, please Don't do it or at least sell your VFR before pissing off everyone with some insanely loud exhaust(can you say HD with straight pipes). :idea3:

Extremely loud exhaust on any brand of bike only hurts our entire sport, it will only lead to further strict Laws & regulations. Many race tracks are either being closed down because of noise or are having to meet Db limits. Many classes at the local oval track are now required to run mufflers and I don't see that as a problem if it will let the sport continue and everyone has to run one and meet a db level.

I had to be under a certain db level when I road raced cars with SCCA and I also have to at bike track days, that's all fine with me if it lets me keep doing what I enjoy.

People who choose to run anything w/o exhaust will only hurt my future chances to enjoy it and that pisses me off!!!! :laugh:

It's going to lead to further laws and regulations no matter what you do. Goverment and cops will try to make more money. It's like property taxes ... they will never decrease.

My vfr is too quiet and it doesn't get noticed when I drive next to other motorists. That puts me at a higher risk of someone cutting me off, driving into me, etc. I look at it like a safety feature. Maybe others who live in the open country don't worry about that stuff but the trafic on the jersey turnpike sucks.

[Guest]

My vfr is too quiet and it doesn't get noticed when I drive next to other motorists. That puts me at a higher risk of someone cutting me off, driving into me, etc. I look at it like a safety feature. Maybe others who live in the open country don't worry about that stuff but the trafic on the jersey turnpike sucks.

Are you sure you didn't mean to by a Harley. Sorry, but loud pipes don't save lives. Being an alert and engaged rider does. Load pipes only tell people that some a$$hole just rode by. Sorry, had to get that off my chest. :laugh:

[FotoMoto]

Now ask yourself, "Self: this is so easy and simple, why isn't everyone doing this?".

Tom, that wasn't a rhetorical question. What's your answer?

[xTomKx]

Are you sure you didn't mean to by a Harley. Sorry, but loud pipes don't save lives. Being an alert and engaged rider does. Load pipes only tell people that some a$$hole just rode by. Sorry, had to get that off my chest. :fing02:

Nice way to offend everyone. I think about half the people on the forum have aftermarket pipes which are loud wot.

If it bothers you wear earplugs.

:laugh: :idea3: :offtopic:

Let's get back to the topic

[pbmax]

How about just doing one of the exhaust mods to the stock exhaust? Keep the look of stock but the sound of a straight-thru (ish) system. I did mine and WOW is it awesome!! Just sayin.

[VolatileVFR]

but I like the way the stock pipes hide my license plate.

OUCH!!

:laugh: :idea3: :offtopic:

I think thereis difference between loud pipes and quality exhaust.... I will leave it that simple.. I didnt read all the above posts, but, IIRC the exhaust on this engine will "contain" the HP while complete loss does not give the engine enough backpressure to enhance all powerbands...

[Darth Bling]

Are you sure you didn't mean to by a Harley. Sorry, but loud pipes don't save lives. Being an alert and engaged rider does. Load pipes only tell people that some a$$hole just rode by. Sorry, had to get that off my chest. :laugh:

Nice way to offend everyone. I think about half the people on the forum have aftermarket pipes which are loud wot.

If it bothers you wear earplugs.

Yeah, but most people don't ride around WOT all the time, so it's a moot reason. If you believe load pipes will help people notice you, that's your prerogative. And, like you said, it's off topic.

Let's get back to the topic

Yes, let's do so. Even though aftermarket pipes are "straight through", it doesn't mean they have less back pressure than san cans. The bends and curves contribute to the restriction of the exhaust, as well as the longer length of the exhaust. I think you'd still want to put some short of restriction in to keep back pressure from getting too low.

I think if you were fabricate a MotoGP style exhaust, it would be a much better idea. Not so much from a loudness point-of-view, but because that particular style of exhaust is so sweet looking. And, it would be quite trick since it would be a custom job and nobody else would have one like it. JM2¢, but any monkey can take the exhaust cans off their bike and ride around. Now, you could build some sort of exhaust bypass, but then you'd be adding complexity and weight to the bike.

Personally, I think you should look into some Leo Vince cans. I get so many compliments from people about mine. They aren't loud at all (except when you're hammering it), so they're quite nice in town. But, they've got a nice rumble to them, which you can really hear inside your helmet. Very nice! :idea3:

[TimC]

Why isn't everyone doing this? Because it's obnoxiously loud. Might also be illegal, same as trying to hide your license plate - tho most fender eliminator kits keep them visible.

My $0.02: Gut the stock exhaust first and see if you like the sound.

No offense, Tom K., and I know I don't have to deal with the traffic you do on the Jersey Turnpike, but your defensive riding skills should be used to ward off idiotic cagers rather than loud exhaust cans. Louder cans might help, but so would a very brightly colored jacket, vest or riding suit.

[DaveM]

Wow! All the threads and conversations that have been created here over the years on after market exhausts and gutting stock exhausts - all for more sound and more esthetically pleasing sound.... But we seem to have a problem with this? Is it the subtitle that has everyone's shorts in a knot?

An exhaust you could quickly and easily adjust to suit your preference would be ideal. Quiet for leaving the house on those early morning commutes, then loud and squidly for bike night. Isn't that sort of what we accomplish by pulling the spuds out of most after market pipes? On the cans I built I’ve gone through several internal designs and packing levels to get exactly the sound I wanted, but even now there are still times when I wish it was louder or quieter.

Keep after it Tom.

[tyrroneous]

Please, please, please, PULEEEZ do NOT ride around with open pipes! My goodness man, think of the children!

[toro1]

As I have been down this path, I'll share some of my own experiences with you...

First off, an unmuffled VFR (that is, taking the muffler off at the end of the exhaust header) without a catalytic converter does not sound good at WOT. It's very blatty, unrefined, and just not pleasant to listen to -- nothing at all like an uncorked V8. Cat-equipped bikes might differ here since the cat muffles & smoothes out some of the sound, but my '98 was not at all pleasing with the exhaust removed. Adding tubing after the header will alter the sound and might make it better as well, but as it stands, the 98-99 bikes sound awful, I repeat, awful (and insanely loud) at WOT with no pipe.

Also, the notion that NA engines need exhaust backpressure to make power is a myth. Anything that impedes air from entering or leaving an engine is a restriction, and any restriction (that is, loss of energy) robs power. This is why good exhausts have mandrel bends and smooth transitions in the merge collectors, all in the effort of reducing unwanted restriction (aka backpressure). The key design considerations for an exhaust are pipe length and pipe diameter, for the primary, secondary, and collector sections -- these factors are what really determine the powerband-altering aspects of an exhaust system, as exhaust gas velocity can be custom tuned to boost power in a certain part of the rev range.

I haven't even mentioned the scavenging effects offered by a well designed header, nor do I need to. The header on our bikes is designed to offer a broad range of power, and what goes on after the final exhaust clamp can only really squash power. For example, when I first designed my shorty exhaust, I had a 2-disk insert inside the core of the muffler, designed to reduce the decibels to an appropriate level. It worked on the noise reduction level, but put out weaker power than my old Staintune pipe (about 10hp less, actually). Once I pulled the insert out of the exhaust, not only did I gain back power, I gained almost 7hp compared to the Staintune! This is with a large diameter, short section of lightly muffled pipe right after the exhaust header -- no backpressure here, folks. Power was up everywhere, leading me to discover that the stock header will work quite well with just a short leader pipe attached to the header, and any muffler configuration can only lead to a reduction in power.

High exhaust gas velocity = complete evacuation of unburnt gasses from the cylinder = power, it's as simple as that. Unfortunately, there are always compromises to make, and while small diameter pipes keep the velocity high when the revs are low, they choke the flow when revs are high. Conversely, large diameter pipes kill flow when rpms are down (the gas expands, cools down, loses energy, and slows down), but when revs are high, they allow for unrestricted flow. I'd be willing to bet that if I equipped my supercharged bike with larger diameter pipes from the head on down, I'd pick up an easy 10-15hp without breaking a sweat.

Hope this clears up some things for you.

Or maybe it just made a bigger mess.

[Baileyrock]

I have and love the sound of aftermarket exhaust. I too like to hear the engine note, but I would like it to be as loud as possible w/o it being offensive.

There is a HUGE difference with the sweet sound of some nice aftermarket cans and open headers as suggested here by the thread starter. :idea3:

As an Old Fart rider, I guess I've matured enough to realize the negative consequences towards our sport by acts of stupid behavior. IMO Street Racing, Stunting and Loud Exhaust are the 3 Main reasons that our sports freedoms will eventually be legislated away. Attitudes like yours Tom are leading the way to our extinction. :offtopic:

I am willing to speak up and do whatever I can to help slow that inevitable future! Policing ourselves Should be a big part of each riders responsibility. That means that if your riding buddy is doing something stupid you should call them on it, of course that's only if you give a rats ass about the future of our sport or your buddy!

I have to add that I like to ride fast and I do it out away from everyone as possible, I try to consider every other person I come across whether there in a cage, on a bike, or in their yard. I will do everything in my power to make the smallest negative impact on their live and that directly effects our lives as riders.

Our sports future is in our hands! :laugh:

[xTomKx]

Wow! All the threads and conversations that have been created here over the years on after market exhausts and gutting stock exhausts - all for more sound and more esthetically pleasing sound.... But we seem to have a problem with this? Is it the subtitle that has everyone's shorts in a knot?

An exhaust you could quickly and easily adjust to suit your preference would be ideal. Quiet for leaving the house on those early morning commutes, then loud and squidly for bike night. Isn't that sort of what we accomplish by pulling the spuds out of most after market pipes? On the cans I built I’ve gone through several internal designs and packing levels to get exactly the sound I wanted, but even now there are still times when I wish it was louder or quieter.

Keep after it Tom.

That's exactly why I was thinking about welding in a dump valve before the stock mufflers. So that I could keep it very quiet when I wanted to. I already did some moding to the stock exhaust with a drill and an air-chisel but when I ride with my brother who has Yoshi pipes I can bearly hear my bike.

Making your own tunnable mufflers is a great idea. But I don't have the budget or the time. I'll probably run some tests to see how loud the bike is with open mufflers.

Why people havn't been doing it .... because most older bikes don't have catalytic converters. Some backpressure is needed to have low end power. Otherwise the powerband shifts up to the higher rpm and kills the low end. My philosophy is that the cat will provide some backpressure. Our bikes have long headers also.

[Guest]

On my 98 i have a straight pipe that i built so that it would be an underseat ehaust system. I love the way it sound and all the car guys here at the dealership i work at love it too. It will get alittle raspy at about 6500-7500 rpm at part throttle. But when i do a wide-open take off it will stand the hairs up on the back of your neck and sounds like a stroked racing engine. As far as neighbors are concened, i just putt around near the house. I use the Harley guys motto, loud pipes save lives and i know everyone around me on the tollway han hear mean if i need them to. But actually its not to bad when i shift to a higher gear and cruise around 4000-5000 range in town.

[Darth Bling]

I have to add that I like to ride fast and I do it out away from everyone as possible, I try to consider every other person I come across whether there in a cage, on a bike, or in their yard. I will do everything in my power to make the smallest negative impact on their live and that directly effects our lives as riders.

Our sports future is in our hands! :laugh:

Isn't this the sort of the same thing that Tom is trying to do with his exhaust? From the sound of things (no pun intended), Tom wants to install some sort of bypass valve so he can run his bike quiet around town, but when he's out in places where there's no people or people who just don't care he can open her up.

That's exactly why I was thinking about welding in a dump valve before the stock mufflers. So that I could keep it very quiet when I wanted to. I already did some moding to the stock exhaust with a drill and an air-chisel but when I ride with my brother who has Yoshi pipes I can bearly hear my bike.

Making your own tunnable mufflers is a great idea. But I don't have the budget or the time. I'll probably run some tests to see how loud the bike is with open mufflers.

What's the quote? "Do it right, or don't do it at all" Seriously, the whole bypass quiet/loud option sounds like a great idea. I would love to see you pull it off. :idea3: But, if you're not going to do it and instead are just going to run open mufflers, then I have to agree with Baileyrock. We have to ambassadors to our sport. If we don't, nobody will.

[FotoMoto]

Making your own tunnable mufflers is a great idea. But I don't have the budget or the time. I'll probably run some tests to see how loud the bike is with open mufflers.

Kerker/Supertrap has made a "tunable" muffler for eon's. The more discs you add the louder they get but you're talking about going from muffled to open with the turn of a valve. That would throw the fueling map way off me thinks.

[Guest]

I've thought about an exhaust system that could both be "throaty and obnoxious" and "stealthily quiet" (I.E. stock sounding) on demand for a while now. Having built a few custom exhaust systems, I've always thought it would be really cool to have an electronic servo actuated EXUP type "dump valve" going to a barely baffled can with a "stock type" heavily baffled can open all the time. I think it would be really cool to have a bike that had a civilized, low db. exhaust note that with the touch of a button could transform into a hellacious sounding beast. I built a "RC211v/GSV-r" type 2 into 2 exhaust for my VFR and my RC51 has dual M4s so I don't currently have a ride to try this system out on. Maybe on my next project.

[Darth Bling]

I've thought about an exhaust system that could both be "throaty and obnoxious" and "stealthily quiet" (I.E. stock sounding) on demand for a while now. Having built a few custom exhaust systems, I've always thought it would be really cool to have an electronic servo actuated EXUP type "dump valve" going to a barely baffled can with a "stock type" heavily baffled can open all the time. I think it would be really cool to have a bike that had a civilized, low db. exhaust note that with the touch of a button could transform into a hellacious sounding beast. I built a "RC211v/GSV-r" type 2 into 2 exhaust for my VFR and my RC51 has dual M4s so I don't currently have a ride to try this system out on. Maybe on my next project.

The current CBR600RR (07-08) and the recent CBR1000RR (06-07) have servo-acutated valves in the headers (about the same place our catalytic convertors are on the VFR). Honda stuck them on there for sound emission reasons. Serveral people of dyno'ed their bikes with the valve operating normally vs with the valve disabled and there were no differences in the dyno charts.

So, Honda already does something similar on their CBRs. I'm sure you can find tons of these Honda valve units since many people have gone to full aftermarket exhausts. Or, maybe a wastegate-type dump valve like what's found on turbo systems would work?