• There has been a recent cluster of spammers accessing BARFer accounts and posting spam. To safeguard your account, please consider changing your password. It would be even better to take the additional step of enabling 2 Factor Authentication (2FA) on your BARF account. Read more here.

Open pipe=Must ReJet?

Reminds me of this guy that lives in my complex.

I hear his muffler-shy bike every day. Sounds kind of reminiscent of a MotoGP bike, loud, raspy. I actually saw the bike as we were pulling in to the neighborhood the other day. Ninja 250. If you can't go big, go loud I suppose. :rolleyes
 
racedout said:
....and people who are against motorcycles will be against them no matter what you do so safe that crap for someone else
Click to expand...


Not true. Images can be changed. And bad impressions that influence non riders don't have to be created.
 
racedout said:
yep i stunt in the parking lot not around asshole cars that will run me over and where i have the possiblity of wrecking and causing traffic backups and maybe even hurting other people
Click to expand...

Thumbs up for at least stunting in the right locations. :thumbup
 
racedout said:
thank you ;P alot of people look down on stunting period....shouldnt it be acceptable in the right locations? parking lot with noone else around???
Click to expand...

+1

I have no issue with stunting when and where it's safe. It's the riders who are tempted to display their mad skillz in freeway traffic or in front of *$'s that I :| at.
 
thats just stupid on their part...here in dallas its already nerve wrecking just to ride on the highways let alone have to balance a wheelie at the same time
 
Dopesick said:
:cry

You sir have no right giving facts based upon YOUR OPINION.
Click to expand...
I wrote a long post about how you are basically, well, wrong. But then I decided how about we just let the record setters speak thier piece?

http://www.nrhsperformance.com/racing.shtml

I think there are 2 bikes on the entire page with anything but a straight pipe. One of those is a Buell Blast which I assume is stock, the other I can't see the full system but has a similar design to other bikes that would have a muffler.

Every other bike on this page has a tuned length, tuned diameter system, routed for a straightest shot out the back. There is nothing there to add backpressure.

You sir have no right giving facts based upon YOUR OPINION.
 
Last edited:
Sidewalk said:
I wrote a long post about how you are basically, well, wrong. But then I decided, how about we just let the record setters speak thier piece?

Every other bike on this page has a tuned length, tuned diameter system, routed for a straightest shot out the back. There is nothing there to add backpressure.

You sir have no right giving facts based upon YOUR OPINION.
Click to expand...

You proved my point exactly, and also reinforced exactly how wrong your own words prove you are. You said it perfectly.
"Every other bike on this page has a tuned length, tuned diameter system, routed for a straightest shot out the back."

If you were to place a pressure gauge into the system you would indeed find PRESSURE. :thumbup

I NEVER said a muffler was required to engineer the correct flow and backpressure in a system. All the muffler is for is "sound emissions", HOWEVER when a muffler is in the system it needs to be balanced out in the overall system flow and back pressure amount, for proper performance.
 
Last edited:
hate to break it to you, sidewalk, but dopesick is completely right and you're....well......completely wrong. and besides that theres not 1 inline four on that site. comparing the backpressure needs of a big v-twin, with rocker arms and technology from the 80's with a little inline four with technology from the 90's isn't a great comparison.
 
Thanks for backing me skippy. :thumbup

I guess I let it go to my head that people PAY me to make things go fast, and fast things even faster. :cool

If he really wants to get technical. I COULD start listing the draw backs of having a "bell" or Velocity stack, 90* to the airflow at high speed, creating a vortex and actually HURTING airflow performance into the carb. Where as they COULD turn the velocity stack 90* into the airflow. Thus creating a "ram air" effect, and improving airflow through the system. But hey what do I know.

Btw: had he read the ENTIRE SITE.. Even he could understand and see where I was coming from. The supertrap is technically a muffler. An adjustable one... And one can see by checking the link below, which I quoted the good stuff from.
http://www.nrhsperformance.com/tech_supertrapp.shtml

and I quote:

"All of these pulls were done on the same day, on the same bike, as close in time to each other as possible. As you can see, adding discs helped midrange and top end power in all cases, and never lost any bottom end power!

In general, we like this exhaust, it diffuses well with lots of discs in it and gives a good wide powerband.

We also did a few pulls with the end cap and discs removed, just to see what it did. Here we compare the best one with the 26 disc pull.

As you can see, you need the discs!

Supertrapp systems are readily available from NRHS,"
 
Last edited:
Long winded response that was probably pointless so I deleted it, and I appear to be replacing it with another.

I could sit here and spew out details on about pt pressures and tt temperatures on turbines and maybe the concerns of free turbine speed, or deisel firing pressures, or reading exhaust temps on a boiler system analyze heat transfer effeciency. But those are not exactly related to what we are talking about kind of like velocity stacks. To get technical.

Funny how they will talk and support an exhaust system they sell, but you don't see it on a single one of the high performing LSR bikes. I posted that link for the pictures, not to advertise thier goods.
 
Last edited:
*Sigh* No your not picking up 100% on what they are after in THOSE bikes with straight pipes. What they are attempting to acomplish is moving air. After all with all the other technical defeciencies the V engines suffer from, they HAVE to move air. And do it in the least restrictive way. In THAT case they are doing so to REDUCE engine load, and spin a higher RPM in a less restrictive fashion. The limit they have on speed, in land record attempts are gearing and rpm. The faster you spin things the faster you go.. YES there is a fine balance between power to weight, wind resistance etc.... I could go on and on... However...

I already said I could continue on and on. Every point you drag into this conversation shows your not understanding what they are doing in that exact setup. Honestly it's not helping the poor OP, in the simple question he had.

Which, the correct answer is YES. With any change of system flow, fuel amount and atomization will change, and needs to be corrected.
 
Last edited:
There's a reason expansion chambers exist on two-stroke motors, and many of those principles can be applied to four-stroke motors, such as using the resonance of the exhaust system to increase the volumetric efficiency of an internal combustion engine. They've been doing it since the seventies.
 
Last edited:
The lack of a pipe and thus, zero back pressure in the exhaust system can work well if you tune the engine for that situation. But, you'll only get maximum output at the very narrow RPM range that you do that tuning at. For all other rpms, higher and lower, it will run like shit. Exhaust systems inherently need back pressure, not because the backpressure is required so much as that it is a necessary evil for other reasons. Like wanting the engine to perform at its best throughout a wide range of RPM's. And the need to route the exhaust somewhere safe. If internal combustion engines only ran at one RPM and didn't need any routing of the exhaust for other reasons like out the back so you don't asphixiate yourself, or to a muffler for noise suppresion, you could design the motor to run with zero backpressure and be very efficient. But, as we all know, internal combustion engines need to run efficiently at a wide range of RPM's and need to be safe and quiet. So, backpressure is a necessity.
 
'Just looked at the second Supertrap dyno run in the link that was posted. That illustrates my point. Notice that with the disks removed and backpressure reduced, power actually increases across a narrow range of RPM. Everywhere else it's reduced. If you were to futher reduce backpressure by cutting the pipe down or even removing it, you'd find that the power in the narrow range would actually increase, but that narrow range would get even narrower and the power everywhere else would continue to fall even more.

As I mentioned before, backpressure is not necessary if you're designing an engine to run at only one RPM. It is necessary if you want a nice, broad power curve.
 
Oh, and ever notice that vehicles designed for long extended runs at top RPM often have short large diameter exhausts? That's because the engines are used at or near max RPM and stay there throughout the run. They're tuned to make peak HP there and much less emphasis is put on making power elsewhere. There's no need to make the motor pull strongly throughout the range. All they want is max power at max RPM. So, they can get away with extremely low back pressure.
 
I will run an open pipe for however long I please no matter what anyone says.

Explain the theory of an open pipe being peaky or only making power at a certain rpm and losing power elsewhere. Last time I checked, my tri-oval was an open pipe. Granted, it absorbed sound, but still a big open tube straight down to the collector.

The bike runs fine, BTW.
 
You must log in or register to reply here.
Back
Top