Open Exhaust...?

[acee125]

It looks like it's gonna be a while before my Mac's show up and with fresh rubber and great weather I'm itching to go riding. However, I'm sick of my bike being so quiet.

Would it hurt my bike at all if I ran it without mufflers and had no exhaust from the manifold back?

I would assume that the bike would need to be jetted a bit richer although it seems that the concensus on ROV is that you don't HAVE to rejet after you install Mac's.

Is it safe to assume that Mac's and the stock exhaust with no mufflers would have appoximately the same amount of flow?

Would I be taking an unnecessary chance of burning a valve with so little exhuast or would my bike just be extremely loud?

[Brian Moffet]

I believe the stock mufflers (complete, everything) and the Macs have the same flow.  If I remember correctly, there should be no jetting changes from the standard entire exhaust and the macs.

I would worry about not have exhaust, you'll be dumping an incredible amount of heat right at battery level from the rear Y pipe.  I think pulling the exhaust would be a really unsafe and bad idea.

I'm not so sure why you're sick of your bike being so quiet, that baffles me.

edit: I just did the math, and the exhaust temperatures at the Y-joint would be around 1300 degrees Fahrenheit.  That's enough to move some steels from elastic deformation into plastic deformation.  I.e it will bend and not return to the original shape...

Brian

[kiawrench]

been there, did that - if you are going to run open collector, get ready to buy wiring harness,battery ,r/r rear tire ,bushings/maybe bearings --- you can, (not will ) destroy the bike by just jumping out there and running open headers

[acee125]

Brian and kiawrench,

I see the error of my original post and should have taken a closer look at my exhuast before I posted. I thought that you could remove just the "cans" from the manifold but upon closer inspection I found that they are welded to it. (at least mine are)

As far as wanting to make it louder? I'll blame it on my youth. Why did people put glasspacks on muscle cars in the 60's and 70's and why to people straight pipe harleys? Because when done right, I think it sounds cool. I know that opinion is not shared by all and that's ok.

Respectfully,

Acee125

[h2olawyer]

I agree with Brian.  Loud bikes mostly serve just to annoy the non-riding public, further damaging our reputation.  About the only 'safety' argument to be made is to give an audible signal to unwary pedestrians.  The sound basically flows in a cone shape to the rear of the bike.  Well over 90% of the auto - bike accidents come from the front or side.  Your horn makes a much better signal to them than an exhaust ever would.

If bikes keep getting louder, look for tighter enforcement of existing noise statutes, tougher laws & even arguments to ban bikes.  What would you rather do - self police in this issue or become an accomplice to further restrictions in our right to ride?

As you can tell, loud bikes are kind of an 'issue' with me.  Unlike Rick_G, I actually like the sound from our OEM exhaust.  I don't think it "sounds like a Hoover with a head cold".   ;)

As for damage to the bike, I wouldn't do it.  No sense in taking the risks.

H₂O

[acee125]

I see the error of my original post and should have taken a closer look at my exhuast before I posted. I thought that you could remove just the "cans" from the manifold but upon closer inspection I found that they are welded to it. (at least mine are)

Yes, upon further examination I think it would be ridiculous to run the bike with open exhaust because of many already mentioned problems it would pose.

As far as noise is concerned: Ridiculously loud bikes are only good for one thing: showing off to whoever it is you want to please. Other than that they'll just make you deaf if you have to listen to it at speed and annoy cage drivers while you're at it.

However...I'm still a fan of moderate to loud bikes. IMHO, they sound cooler and in most cases free up horsepower. When I rev my V either while stationary or on the go I hear mainly engine noise, I also want to hear my exhaust. Thus, get a new set of pipes.

For me, the ideal exhaust is one that is loud when you rev it, and mellows out into a nice tone when cruising. I would guesstimate that 60 to 80 percent of bikes with aftermarket exhaust fall into that catagory.

[Brian Moffet]

in most cases free up horsepower.

Actually, there have been some tests done with aircraft (which tend to run straight pipes).  Turns out that a quieter tuned exhaust will provide more power than the straight pipes.  There is a company that is making tuned exhaust for general aviation aircraft and seeing 15 percent HP increases.  (http://www.powerflowsystems.com/exhaust_process.php is what they have).  While I could not argue that the Vision exhaust has been tuned to nearly the level that power flow systems has done for aircraft, it is an interesting idea.

Brian

[acee125]

Turns out that a quieter tuned exhaust will provide more power than the straight pipes.  There is a company that is making tuned exhaust for general aviation aircraft and seeing 15 percent HP increases.  Brian

It all depends on what you're trying to accomplish. Like you said, exhausts can be tuned. Generally for power delivery and the desired RPM range you want the power in. And yes, they can be made to run quiet and still produce if not increase power. The quiet factor of the airplace exhaust you gave example of is not the source of the power increase but a byproduct of its design.

It's the same reason that long tube headers result in more horsepower than "shorty" headers and why Flowmaster's "Delta" series mufflers can stay reasonably quiet while gaining horsepower over OEM mufflers.

[h2olawyer]

Most current noise ordinances permit aftermarket exhaust only if they are no louder than the stock exhaust.  They are also graduated, allowing more noise for older vehicles.  That said, the laws aren't heavily enforced in too many places.  I know Colorado Springs has equipped their police force with db meters and began aggressive enforcement a couple years ago.  Even guys with aftermarket cans on sportbikes (which are not normally that annoying) have been forced to reinstall their stock exhaust.

H₂O

[QBS]

Regarding aftermkt. cans on sprtbikes:  Several years ago Motorcycle Consumer News did before and after dynometer testing on several 1000 c.c. sport bikes of the day equiped with various aftermkt. systems.  They found that more loud=sometimes, a little more power and sometimes not.  Power change variances ranged from -.7hp to +3hp.  In most cases the effect was to simply move the existing power up the power curve, closer to red line.  For all practical purposes, in the real world, such changes are in drivability, not quarter mile times.  Straight line seat of the pants improvements would for all practicle puposes be undetectable, except in mind of the rider where the change in decible levels and power curves might be erroniously interpreted as noticably more power.  Additionally, differences in rider expertise, would no doubt offset any actual power differences.

The primary benefit was in weight loss, where there was always a loss in system weight.  I don't have the weight differencial figures.  But, I'm thinking it maxed out around 10 lbs.

So, in the best case scenario, for somewhere between $600.00 and $1200.00, you gain 3 hp and loose 10 lbs.  Is it worth it?  Not for me.  But for some young people, with all the wisdom that implies, bragging rights and "look at me" are worth every penny. 

[kwells]

For my Sprint, the pipe was 375.00 and I lost about 14lbs of weight.  It is louder than stock but I likes it that way.  It adds a very modest 3-4HP max to my chart. Some mapping changes gives the torque curve back its straight profile.
A pipe on a modern day bike without mapping changes does nothing except save weight.  Some of these systems by the way will weigh in at over 30lbs stock.  There is significant savings to be had on them especially with the stock dual catalytic converter systems.

BTW the Vision system weighs 29lbs.  That is massive for such a small bike.

[Rick G]

If you want to get a little more sound from the stock exhaust, drill 6 1/4 inch holes around the exhaust outlet
in a circular configuration . It will warm it up a little bit and get away from the whoosh sound of the stock pipes.

[Walt_M.]

Loud exhausts also have the benefit of attracting the attention of those fine folks with the flashy red and blue lights on their cars.

[kwells]

Personally If I wanted to sink into the shadows I'd probably stay home.  Red and Blue tends to find me regardless of my pipes.

[Walt_M.]

What I meant was, on the occasion when I want to let her rip I don't want the law to hear me a half mile away and come looking. If I am careless and they see me, ok, my bad. My bike has Spec IIs and I do keep the packing fresh, it is pretty loud if I don't.

[Coil Coyle]

Loud exhausts also have the benefit of attracting the attention of those fine folks with the flashy red and blue lights on their cars.

My "pull over quick; be non-threatening and polite" method of dealing with officers doesn't work as well when you have loud pipes.

$0.02
;)
Coil

[inanecathode]

Loud exhausts also have the benefit of attracting the attention of those fine folks with the flashy red and blue lights on their cars.

My "pull over quick; be non-threatening and polite" method of dealing with officers doesn't work as well when you have loud pipes.

$0.02
;)
Coil

Or ape hangers for that matter.

[macroars]

If you want to get a little more sound from the stock exhaust, drill 6 1/4 inch holes around the exhaust outlet
in a circular configuration . It will warm it up a little bit and get away from the whoosh sound of the stock pipes.

I did that:
http://web.mac.com/roarstokken/RoarS/Media/Original%20pipes.wav
http://web.mac.com/roarstokken/RoarS/Media/Drilled%20pipes.wav

I really liked the "new" sound!

In addition I had a more rational reason - I patched a hole, and wanted to reduce the pressure inside the mufflers to make it last longer....

[reardeac]

acee,
what do you plan on doing with your old exhaust is it in decent condition. i also am of the school of thought that quiet pipes keep your butt from getting a ticket, especially here in the burg that i live in. i would gladly by it if it isnt rusted through anywhere. i love the balanced look of an exhaust on each side of the bike but no way am i buying predators.
thanks

[vadasz1]

Drilled - definately sounds better to me.

Somewhat loud pipes are alright as motorists will definately know you are near them on the highway.