Heres my idea, well not really mine but ya. I keep my stock ehusat and cat but i but this Y-type pipe inbetween the cat and the header. The Y would have a valve in it that could change the exhuast flow from one on the Y’s “branches” to the other. You would be able to move the valve back and forth from inside the car while driving. On one “branch” you could have your stock exhaust setup then on the other you can just have a striaght pipe…no it won’t be legal but it would be alot of fun. and sorry about my lack of lingo, i think someone posted something like this a long time ago…they had a picture of what i am talking about. So can someone tell me why everyone isn’t doing this on thier cars? Thanx
1.) because its illegal
2.) it would be EXTREMELY loud.
3.) i think its too “domestic” like. seems sorta ricey and just lame. IMO though 
they’re always sellin these on Ebay for like $30 bucks.
woody
why not just get a test pipe?:roll: thas what i did… i know you lose low end… but the top end is way better… and when you think about it… when your racing… yoru ALWAYS in teh top end
Re: Exhaust Mod
Originally posted by Integra Style
Heres my idea, well not really mine but ya. I keep my stock ehusat and cat but i but this Y-type pipe inbetween the cat and the header. The Y would have a valve in it that could change the exhuast flow from one on the Y’s “branches” to the other. You would be able to move the valve back and forth from inside the car while driving. On one “branch” you could have your stock exhaust setup then on the other you can just have a striaght pipe…no it won’t be legal but it would be alot of fun. and sorry about my lack of lingo, i think someone posted something like this a long time ago…they had a picture of what i am talking about. So can someone tell me why everyone isn’t doing this on thier cars? Thanx
you’re gonna loose all your backpressure if you do that. and with all motor low displacement engines that is gonna be a problem. You’ll probably end up being slower rather than faster —plus its gonna sound like ish!
Re: Re: Exhaust Mod
Originally posted by 91IntegGS
you’re gonna loose all your backpressure if you do that. and with all motor low displacement engines that is gonna be a problem. You’ll probably end up being slower rather than faster —plus its gonna sound like ish!
:think:
During the exhaust stroke, a good way for an engine to lose power is through back pressure. The exhaust valve opens at the beginning of the exhaust stroke, and then the piston pushes the exhaust gases out of the cylinder. If there is any amount of resistance that the piston has to push against to force the exhaust gases out, power is wasted. Using two exhaust valves rather than one improves the flow by making the hole that the exhaust gases travel through larger.
its good to loose back pressure
Re: Re: Re: Exhaust Mod
Originally posted by VTEC_Teggy
[B]:think:
its good to loose back pressure [/B]
I think he means velocity. The only way this could be beneficial is if you were running a turbo setup.
Where are the test pipes illegal? And wouldn’t my setup still give more horespower and torque on low and high end? I just want an answer to why alot of people aren’t doing this, besides being illegal-cus most people here don’t care much about that (and i’m not really gunna do this, i’m just tryin to learn.
Re: Re: Re: Exhaust Mod
Originally posted by VTEC_Teggy
[B]:think:
its good to loose back pressure [/B]
its good to lose SOME backpressure. The stock piping has too much backpressure for a really high hp motor. However with an all motor setup you NEED some backpressure to help keep the exhaust flowing at the correct velocity.
ever wonder why people only run 2", 2.25" or 2.5" on their all motor setups? IF loosing backpressure was good wouldn’t they be running 2.5" 3" or bigger??? get my point? Like most things you need to compromise. Too much backpressure is a bad thing, and too little backpressure is also a bad thing.
now, with turbo this isn’t the case. typically if you’re running a heavy boost turbo you’ll want to run 3" exhaust, you want minimal backpressure in order for the turbo to work and spool properly.
this is typically refered to as an exhaust “cut out” and it used mainly on high hp v8’s or turbo/superchaged cars. It gives you an ASS LOAD of power on a properly set up car. And by properly set up car I dont mean a 140hp NA integra.
Originally posted by Formz TSi
And by properly set up car I dont mean a 140hp NA integra.
:naughty: 
[HR]
Posted by 91IntegGS:[BR] [B]its good to lose SOME backpressure. The stock piping has too much backpressure for a really high hp motor. However with an all motor setup you NEED some backpressure to help keep the exhaust flowing at the correct velocity.
ever wonder why people only run 2", 2.25" or 2.5" on their all motor setups? IF loosing backpressure was good wouldn’t they be running 2.5" 3" or bigger??? get my point? Like most things you need to compromise. Too much backpressure is a bad thing, and too little backpressure is also a bad thing.
now, with turbo this isn’t the case. typically if you’re running a heavy boost turbo you’ll want to run 3" exhaust, you want minimal backpressure in order for the turbo to work and spool properly.[/B]
[HR]
Here is my understanding of backpressure and velocity:
They don’t run such big pipes on all motor tegs because they will lose the velocity of the exhaust even though they have little backpresure. So if you had a 1" exhaust setup the velocity would be really high but the effect of the added backpressure would effect the hp more than the high velocity. But if you had a 3" exhaust setup then you would have very little backpressure but very low velocity and then the low velocity would have more of an effect on the hp’s than the low backpressure. So what you would have to do is make the perfect combination that way you can have minimal backpressure with high velocity. The relationship between the two is indirectly proportional: if you had a graph of backpressure vs X.x inch piping (at Xk RPM) and one of velocity vs X.x inch piping (at Xk RPM) and you overlapped the two graphs, the place that the two lines meet would be your optimal exhaust setup. BUT , an optimal exhaust setup is not practically possible because a car has different amounts of exhaust being expelled at different RPM’s so the velocity and backpressure would always be changing. So really the best exhaust system would be having the piping change size as you accelerate. And I do believe that having the exhaust come straight from the exhaust manifold would be the best setup except you would have 5 foot flames coming out all the time. Then reason turbos have to have bigger piping is 1) so they will spool up faster (if there was pressure pushing back on the spool than there would be some unneccessary resistance), and 2)There is just more exhaust being expelled do to the higher HP and RPM’s that turbo’s produce.
Please people feel more than free to argue/discuss with my thoughts. My screenname on AIM is MusicIsAir. If any of this is wrong, please correct me. THanx
I think we should have a section in teg tips labeled how stuff works so that way people can go there when they don’t undertsnad something (like me)
i tihnk i’ll archivethis
that image is pure BS. It’s showing velocity increasing as pipe size increases. When everyone knows that the larger the piping the slower the velocity. It’s like a hose, put your finger over a flowing hose and the hole gets smaller, water goes faster.
so some one take this out of the archive because that image is fake.
Originally posted by Formz TSi
[B]that image is pure BS. It’s showing velocity increasing as pipe size increases. When everyone knows that the larger the piping the slower the velocity. It’s like a hose, put your finger over a flowing hose and the hole gets smaller, water goes faster.
so some one take this out of the archive because that image is fake. [/B]
dito.
OH, sorry there guys. I"m at school right now and i’ll fix the pic when i get home. But yah, i REALLY did screw that pic up. I believe my logic is right but the graph is COMPLETELY wrong. Haha, sorry…i’ll give my self the :bs: The Velocty should be going down as the pipe size increases and going up infinitely towards a horizontal asemtope as the width of the pipe aproaches 0. I still want someone to tell me if my explanation of backpressure and velocity is right or not.
I just searchd the forum and found this, from Sir Rev Alot, thanx.
I. Introduction
One of the most misunderstood concepts in exhaust theory is backpressure. People love to talk about backpressure on message boards with no real understanding of what it is and what it’s consequences are. I’m sure many of you have heard or read the phrase “Hondas need backpressure” when discussing exhaust upgrades. That phrase is in fact completely inaccurate and a wholly misguided notion.
II. Some basic exhaust theory
Your exhaust system is designed to evacuate gases from the combustion chamber quickly and efficently. Exhaust gases are not produced in a smooth stream; exhaust gases originate in pulses. A 4 cylinder motor will have 4 distinct pulses per complete engine cycle, a 6 cylinder has 6 pules and so on. The more pulses that are produced, the more continuous the exhaust flow. Backpressure can be loosely defined as the resistance to positive flow - in this case, the resistance to positive flow of the exhaust stream.
III. Backpressure and velocity
Some people operate under the misguided notion that wider pipes are more effective at clearing the combustion chamber than narrower pipes. It’s not hard to see how this misconception is appealing - wider pipes have the capability to flow more than narrower pipes. So if they have the ability to flow more, why isn’t “wider is better” a good rule of thumb for exhaust upgrading? In a word - VELOCITY. I’m sure that all of you have at one time used a garden hose w/o a spray nozzle on it. If you let the water just run unrestricted out of the house it flows at a rather slow rate. However, if you take your finger and cover part of the opening, the water will flow out at a much much faster rate.
The astute exhaust designer knows that you must balance flow capacity with velocity. You want the exhaust gases to exit the chamber and speed along at the highest velocity possible - you want a FAST exhaust stream. If you have two exhaust pulses of equal volume, one in a 2" pipe and one in a 3" pipe, the pulse in the 2" pipe will be traveling considerably FASTER than the pulse in the 3" pipe. While it is true that the narrower the pipe, the higher the velocity of the exiting gases, you want make sure the pipe is wide enough so that there is as little backpressure as possible while maintaining suitable exhaust gas velocity. Backpressure in it’s most extreme form can lead to reversion of the exhaust stream - that is to say the exhaust flows backwards, which is not good. The trick is to have a pipe that that is as narrow as possible while having as close to zero backpressure as possible at the RPM range you want your power band to be located at. Exhaust pipe diameters are best suited to a particular RPM range. A smaller pipe diameter will produce higher exhaust velocities at a lower RPM but create unacceptably high amounts of backpressure at high rpm. Thus if your powerband is located 2-3000 RPM you’d want a narrower pipe than if your powerband is located at 8-9000RPM.
Many engineers try to work around the RPM specific nature of pipe diameters by using setups that are capable of creating a similar effect as a change in pipe diameter on the fly. The most advanced is Ferrari’s which consists of two exhaust paths after the header - at low RPM only one path is open to maintain exhaust velocity, but as RPM climbs and exhaust volume increases, the second path is opened to curb backpressure - since there is greater exhaust volume there is no loss in flow velocity. BMW and Nissan use a simpler and less effective method - there is a single exhaust path to the muffler; the muffler has two paths; one path is closed at low RPM but both are open at high RPM.
IV. So how did this myth come to be?
I often wonder how the myth “Hondas need backpressure” came to be. Mostly I believe it is a misunderstanding of what is going on with the exhaust stream as pipe diameters change. For instance, someone with a civic decides he’s going to uprade his exhaust with a 3" diameter piping. Once it’s installed the owner notices that he seems to have lost a good bit of power throughout the powerband. He makes the connections in the following manner: “My wider exhaust eliminated all backpressure but I lost power, therefore the motor must need some backpressure in order to make power.” What he did not realize is that he killed off all his flow velocity by using such a ridiculously wide pipe. It would have been possible for him to achieve close to zero backpressure with a much narrower pipe - in that way he would not have lost all his flow velocity.
V. So why is exhaust velocity so important?
The faster an exhaust pulse moves, the better it can scavenge out all of the spent gasses during valve overlap. The guiding principles of exhaust pulse scavenging are a bit beyond the scope of this doc but the general idea is a fast moving pulse creates a low pressure area behind it. This low pressure area acts as a vacuum and draws along the air behind it. A similar example would be a vehicle traveling at a high rate of speed on a dusty road. There is a low pressure area immediately behind the moving vehicle - dust particles get sucked into this low pressure area causing it to collect on the back of the vehicle. This effect is most noticeable on vans and hatchbacks which tend to create large trailing low pressure areas - giving rise to the numerous “wash me please” messages written in the thickly collected dust on the rear door(s).
VI. Conclusion.
SO it turns out that Hondas don’t need backpressure, they need as high a flow velocity as possible with as little backpressure as possible.
That is pretty much what i was trying to say, he just says it alot better.
Originally posted by Integra Style
SO it turns out that Hondas don’t need backpressure, they need as high a flow velocity as possible with as little backpressure as possible.
um… thats what EVERY car needs. Not just hondas. But its impossible to have peak velocity with zero backpressure. It’s a tade off:
Best velocity with huge backpressure
Huge backpressure but zero velocity
You have to find that point. And an exhaust cut out is NOT the answer. Most people feel its 2.25" piping.