2 mufflers on i4 = loss of back pressure??
 

does anyone know whether i will lose back pressure or not if i put 2 mufflers on a i4? for instance two Evo

From what I understand, you will lose back pressure at low RPM's. My GReddy SP exhaust is a single exhaust and I can feel a small loss of pressure. It takes a little more to get moving from a stop. From what I've heard, it is not wise to go dual with a four banger. I know there are some members of this forum with duals and their fours. Maybe they can share their opinions.

i have seen ppl with dual zigen fireballs and they told me, they don't feel any loss at all. yeah i know it sounds unbelievible but that's what they said. im asking this question cuz dual look better than single and if i wanna go with dual Evo, it's only 50 bucks more plus the cost of custom Y pipe. but on the other hand, im concerned about lose of back pressure and the extra weigh of the second can. well i will probably just go with single then

i think you're confused. you need to buy the Evo for $500, then add the dual option of $450 on there. so you'll actually spending $950 total. (i'm guessing on these prices.)

you sure? on its site, it says evo for v6, $649; 4 cyl, $599. the extra is just for the can, no pipes

this is from the greddy homepage ...
____________

10156633 Accord V6 2/4dr 1998-on 60 115 $649.00
10156634 Accord V6 Dual Opt 1998-on 60 115 $439.00
____________

from my knowledge, you have to get the single pipe, then add on the dual option. i could be wrong though, but i'm pretty sure about this.

fawk...sorry i didnt see it clearly .i will say no thanx to dual setup then

no, your right Eklypse39. If you were going to buy the exhaust, I dont think you would buy retail. You can usually find it cheaper.(i've seen it for like 30% cheaper on GBC) I have the Greddy MX w/V6 Dual Option on my ride. Email me for a pic steveng

Dual exhaust on 4 bangers that weren't designed from factory that way is something to laugh about.

Haha, yeah. But anywayz, you CAN go dual, but I think the Y piping will need to be like 1.25-to-1.5? I dunno, I don't think it's worth it go to dual unless you got something else to back it up.

Is it worth it being laughed at by car enthusiasts?

dual exhaust systems on i4's arent worth while at all to get some real gains you'd have piping close to that of stock size. even on V6's its not that great (its done to lower the sound of the exhaust)

Just to clarify, even though the 6's may have 2 mufflers, it is not a true dual exhaust system.

Stang GT?

from the article i read on honda life "you don't need backpressure, they need as high a flow velocity as possible with as little backpressure as possible."

that sounds crazy. did it say which car?

hM.. I wanna read this article.. :confused:

*i did not write this i got it from HONDA LIFE. i copied and saved it on my computer because i thought it was a good info.

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.

torque is increased by backpressure. hondas need all of the back pressure they can get.

holy dead thread resurrection batman

and... you didn't read the article did you? the need for backpressure is a myth.

If that was true, jamming a banana up your tailpipe a la Beverly Hills Cop would be a great way to add torque.

Next time you quote and try and refute something with your own opinion, read whatever it is that you are quoting first. :yes:

Hahaha, he got :owned:

hahahaha finally, the truth comes out. i had an argument with a moron on here about that the other day. i'll have to direct his dumbass to this thread

Shit that answers my question. I was thinking about going with the Comptech dual exhaust on my 4cyl.... **** that. I'll stick to my stock one.

the highest diameter of pipe i would go with on an accord is 2.25" and definately no split in the pipe. the stock piping is very restrictive.

so you would laugh at my car?

First of all that has to be the single most innacurate article I have ever read on any message board.

and to answer your question Adhzero....Yes I would point my finger and laugh at your car for the dual exhaust on an I4.

Do you have a link to that site?

nightshade, how is that innacurate? you want velocity with little backpressure and turbulance to have the exhaust gases flow out quickly and smoothly. any fluid flow mechanics course will back that up. i know, i took 3 lol

I dunno bout this, but back in the day, my sister's 1988 Olds Cutlass Calais 4dr with the Quad 4 had its entire muffler and exhaust fall off due to rust (even though it was a TX car) when going thru a 'bottom-out' intersection. It was fast to start out with, but it became wicked fast (and wicked loud) without its exhaust. It'd whip up on Camaros all day. One of my friends had a Camaro IROC, an 86 I believe, and that Calais would dust it all day long.

You remember the body style, right? Shared the platform with the Grand Am, Buick Somerset and Skylark?

If everyone is doing the wishy-washy dance about backpressure, then why does even NASCAR use an almost straight pipe setup? Almost no backpressure there.

Because those cars spend all their time at the high end of the RPM range thats why. An accord will make a little more power up high with no exhaust, but down low, you will definitely feel a loss in torque, and hp.

Ask any Accord owner who has had their exhaust rust out, or crack, requiring a new cat-back. On my car, when my exhaust went out all of a sudden on the highway, I felt like my tranny downshifted, and the car was slowing. For an all out race/drag car spending all its time close to redline, it may be worth it, but for every other case, in an Accord, the gains dont outweigh the negatives.

Decreasing the back pressure to an extent will give some useable gains, but take it to far, and you'll end up worse off than when you started.

by simple fluid mechanics.. when you take it too far you actually create more back pressure by losing exhaust gas velocity due to wider diameter piping, etc...

ive got duals on the wagon.......doesnt feel any different to me

http://www.imagestation.com/picture/...b/f9e46a7f.jpg

y'all need to read the article again....it's not hte loss of backpressure that's causing the power loss...it's other shit that just so happens to come into play at the same time as the backpressure loss so people mistake it for backpressure...backpressure is resistance to flow OUT of the engine...how can that be GOOD????? it cant lol

the article is right, back pressure isn't a good thing... accept it and move on

so would a Honda factory exhaust such as the TL-S dual muffler customed piped on an accord decrease overall torque/power since the overall piping is larger?

Dual for a 4 cyl. street car is a waste of money.

yes, it is a waste of $ for performance, but i want it for looks and quietness over my current Greddy Evo.

i think that people loose sight of what a motor does. basically in my opinion, you do one thing to the intake side, you have to do it to the exhaust side to keep things flowing smoothly.
our engines come pretty much perfectly tuned from the factory. everything is engineered in conjunction with all the other parts and its completely balanced. sure they dont put out any horses at this stage, but still they're tuned. i think that if dual exhaust was useable on an i4, they'd already be producing i4's with dual exhaust.

s2000