straight pipe = louder sound and air polution we all know that.

today i had a discussion with a friend about his straight pipe on his si sedan...obviously its louder..so i called him rice...and called my si coupe a little bitch because because his was louder at 2000k rpm than my vtec...

WTF!? BECAUSE IT DOESNT HAVE A STRAIGHT PIPE!?!?! so its a little bitch..

anyways...first thing that poped in my mind was as loud as it is...its probably has less power...since back in highschool in autoshop learning japanesse cars need back pressure which in this case he lost a lot right?
i didnt say anything about it cause if i was wrong id seem like a dumbass...

anyways i did my research and found this http://www.ideamarketers.com/?Straig...ticleid=446067...

says you do loose hp!

but i want to know what you guys think...and hear from people with straight pipes if its really faster? or do they notice drop in performance..

so the rest of the story is.. i just laughed at the poor soul...and that was it...once i find out if it does really loose performance ill just taunt him calling his car rice and race...win some...get my self some new toys for the car..

i havnt seen him actually drive his car..so to elminate "better driver" **** ive been driving stick for 4 years now he got his 2 months ago and started driving stick for the first time...-.- hes just one of thoes guys that thinks they know **** and has money...so im ready to put his money where his mouth is...

...sorry longer post than i expected

 

the only time you should get straight pipe is if you have a built motor, or if your running boost. but even in those 2 situations straight pipe isnt necessary, but larger diameter exhausts are.

but other than that, i would call him rice too.
cuz straight pipes on our cars sound like **** to be honest.
i prefer my stock exhaust + dcrh all day.

 

excellent...quick question would a tbs do anything for me i just have a stock 06 i got the rev hang fixed at the dealer they just updated the PCM

 

dcrh with stock exhaust will not last long adn will start to sound like a raspy.

 

wow.

 

Backpressure: The myth and why it's wrong
I started to get heated when people keep thinking back pressure is helpful for our cars, so im posting this, hoping it will clear up confusion.


Backpressure: The myth and why it's wrong.

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.


Copyrighted from HCF (thanks Sacicons)

 

So did nobody else notice that the OP is our first '09er. Welcome!


Is that a fact!

So why does my exhaust still sound normal even though I've had my DCRH on for over a year and a half??

No raspyness....not even at partial or full throttle.


Silentkillz1.............so what exactly would be an appropriate diameter exhaust system to compliment our cars with a Race header or even in stock form??

Say for example I'm choosing between a 50mm exhaust (1.96 inches) and a 60mm exhaust (2.3 inches). Which one would benefit better in terms of your theory?? I don't know the exact measurement of the stock exhaust diameter.

 

quit killing the environment and tell him to put the cat back on his stock *** si! **** atleast run a high flow metal substrate cat, plus im sure he wouldn't like getting a ticket in socal for no cat vs his possible 5 or less hp gain. but what do i know i drive a clapped 91 rex si

 

^ Agreed. I have turbo and even then have a high flow cat.

 

i dunno lol, i just copied and pasted that info from another site lol

 

so..Silentkillz1 did you read the link i gave? but i read your post but the two sources kinda contradict each other...unless i didnt understand what you pasted..but we all should come to the conclusion that the skunk2 70mm w/o any other mods should do the trick then huh? haha

ps. thanks for the warm welcome rico suave...no homo..

 

1st let me correct your quote here.

2nd, my car doesnt sound raspy and mines been on for almost a year.

 

You suck donkey nuts!

j/k

 

hey how did you get no mercy under your name?

 

is a straight pipe the same as putting on a test pipe>

 

some dood with a civic si dyno'ed a sp2 and ws2 and the ws2 got better numbers/ sp2 is straigt while ws2 is chambered
ws2 sounds better and is quieter

 

My vote is that you're both tools. He for calling a car a "little bitch" and you for getting your panties in a bunch, and creating this thread over nothing. Straight pipes work, even on "non-built" motors. But the power/cost ratio is something to be studied, and decided by each potential customer. /thread.

 

A courtesy from one of the mods/administrators. Can't tell you who though cause I don't want to be the center of anything.

I've actually had a sub-title for a while now but lost it during the transition from zeroforum to vbulletin. When things were up and running again, all those who lost their sub-titles were allowed to have it back....I simply requested a change to mine and it was honored.

 

Straight pipe: No cats no resonaters.

 

Thats some BullShit!!!!!!

Its not Raspy Rico because you are the exception to every thread ever made

I always thought a 60mm would be way better on a built SI versus a 70mm. I say that since I always said that 70 was for a turbo app and kept that in my mind for years. The only thing with a 70 should be either a turbo SI or a Ricer who wants the world to know hes comming down the street

JK

 

.lol i agree.

 

The requirements for drive shafts are satisfactorily met with straight seam welded steel pipes, especially with regard to dynamic characteristics. However, it is disadvantageous that the steel pipe has a relatively heavy weight compared to pipes made of aluminum. One endeavors, therefore, to utilize aluminum pipes, which are considerably lighter. The weight savings for aluminum pipes is at least approximately 30% in contrast to steel pipes. In view of the tendency in the construction of motor vehicles toward saving weight in dynamically loaded parts, whereby additional component parts, such as bearings, can be more cost-effectively designed and dimensioned, the endeavor is to use aluminum. In addition, a lower vehicle weight makes a lower fuel consumption possible.The known drive shafts consisting of aluminum are made from extruded pipe rounds. Due to the high precision generally required for drive shafts, the known aluminum pipes must be subjected to drawing for forming drive shafts, which is associated with a considerable expenditure.

 

^^^
wtf?

 

Shut up.

Plagiarism FTW!

 

Lol