This write ups are nothing new and have been written for people to read that have nothing better to do. A dyno is the only way to measure real HP gains. Anybody can copy an article and pass it on. Don't **** anybody of Junior, thats why this is a forum, because anybody can discuss.

 

Your first post and this one scream that you do not know what you're talking about. I was considering doing a shorty myself on my rr and after much research came across this information. If you take the time to read this you would learn a lot lil Jon. Those post are the answer to the original question, all of the info you and your bf posted are just misinforming this new rider. And if the post are nothing new and common knowledge then why are you posting the wrong facts and even mentioning backpressure lil Jon?

 

I've been building bikes and racing them for years and can garrantee that I know enough not to **** people of. You can't go on a forum and just insult everyone that could be wrong. You could of simply posted the articles without insulting others, but you are just someone that obiously doesn't have friends.

 

so .

wait.
you want me to put my exhaust where?
maybe its too tight?

 

Well there's some good info here, douchery from both sides not withstanding.

Thanks for the info, it's a new read for me at least and much more definitive and informative than anything else I've seen. I don't know if it's all right, but it certainly makes sense.

Maybe you guys could take the pissing match and kids games to pms?

 

you said it johnny-
there was alot of good information in those extensive paste-jobs.
i definately learned something. it wouldve been even better if someone used their own words to explain the concepts in a way that the average rider like me can understand.
they wouldve really gained my admiration for sharing their knowledge in a way that makes us all feel like were cooperating to learn more about the machines we share a passion for.
nobody should feel stupid for trying to figure this stuff out. my bike is kinda like magic to me. i look around in its organs with a little flashlight trying to figure out what does what and as i learn more about it i keep uncovering even deeper science. im on here everyday because you guys know alot . but it really works, the magic kicks in, when a thread starts with a wild idea question and each of us contributes our understanding of it untill a whole picture emerges. we each have little bits of the answer. we gotta show eachother the pices of the puzzle that were holding and the shape of the pieces were each missing.

 

apologies, i was off base in the manner that i posted that, just gonna say it's a "pet peeve" of mine when i read when people ask questions that are answered by misinformation, leading them further in the wrong direction. if you read all of it then good for you leo, i was considering making a shorter pipe on my cbr out of thin gauge aluminum but didn't want to go ahead without fully understanding the pluses and minuses of doing such a thing. i've queried multiple boards about the idea to no avail and spent a lot of time researching trying to find the truth out of all the useless stuff posted everywhere. if you're serious about understanding the concept of an exhaust system then read the above three post, these where the simplest and most honest post i've gathered about i4 exhaust systems on the net.

(again, after a LOT LOT LOT of research online, in person, and via phone i've gathered the following information which i'll explain in my own words, fyi i'm not the most "articulate" person)
Ok for any 4-stroke, inline 4 motor the way to get the most power of an exhaust system is to use concept of scavenging (similar in manner to a 2-stroke but not nearly as necassary). on one of these motors to scavenge you need to use the escaping exhaust "pulse" (pressure wave) to suck more air out of you cylinders and create a negative or low pressure zone inside the cylinder and/or immediately behind the valve.

how you do this is by making an exhaust system that is the correct length and diameter. you want to allow the high pressure exhaust wave to get to the end of the pipe and just be breaking, escaping to the low pressure atmosphere and create a negative pressure in the system that pulls more of the waste inside the cylinders out on the next stroke, creating negative pressure inside the cylinder before the cylinder even begins to drop and build up neg. pressure on the intake stroke, so it's "super" negative on the stroke, sucking in more air (and of course more air + more gas = stronger bang = more power).

-too short and the exhaust pulse will escape too early and the inside of the exhaust will equalize pressure with the outside air, preventing the scavenging effect.
-too long and the systems pulses start piling up which can have multiple effects, the most common is "stepping" which significantly reduce the scavenging effect.
-too wide and the exhaust pulse disperses reducing pressure and negates scavenging and flow velocity.
-too thin (constricting i.d.) and backpressure builds doing exactly the opposite of scavenge, possibly creating a positive pressure outside the cylinder.

this is a very rudimentary explanation, hopefully someone understands it. i think i's pretty crappy but theres a summary...

p.s. backpressure is a negative, but you go too big and you lose flow velocity. you want that exhaust pulse to maintain the same pressure through the pipe and just be escaping as the exhaust valve is about to open, creating the scavenging effect. there are ways to tune an exhaust for different parts of the powerband, but that's not really a simple concept and everyone has different ways of doing it.

 

i'll post a website that has a formula for making an "ideal" exhaust when i find it again, but after reading all of this information and wanting the most power out of my motor i went ahead and spent the money to get a system from a company that i noticed was worn by top privateers who race cbr's instead o trying to design my own. don't believe that brands who are worn in racing are the best because they win, that means that the brand spent a little dough to get their name put on that bikes exhaust. top privateers who race in higher tier leagues are where to look to find the best brands. do you really think that termignoni makes valentino rossi's exhaust? nope, but they sure spent a lot to get the decal put on that pipe made by yamaha or to yama's specs by termi.

this is my list of exhaust for cbr's of all types to make the MOST POWER
1. Arrow, Arata, Akrapovic/HRC (maximum power gains)
2. Micron, Leo Vince, M4 (decent power gains)
3. Yoshi, Ti Force (minor power gain)
4. D&D, Jardine, Two Bros (you got lied to by the dyno op, but at least it's louder...)
5. Hotbodies (you just got robbed of money and power)

Don't mean to offend just my opinion! Flame on!

 

 

I agree, the write up is very imformative and it is very well explained. If you read it carefully enough you will see that a contol valve is used on alot of the newer bike like the yamaha to create a change in the flow. HP is built at high RPM and a good exhaust system builts more hp but torque is what gets us out of the hole and to big of an exhaust kills torque. A good tuned exhaust doesn't compromise either or. We use temperture tape to tune an exhaust and its worked for us. Johnny