Back Pressure Myth

[Smoke Panther]

Re: Back Pressure Myth

^got something other than your flapping lips to substantiate that?

[Blip55]

Re: Back Pressure Myth

just my opinion..

backpressure is a myth with a proper setup.. if you have the power to support completely free flowing, then backpressure does not play a role. for example, the v8's can have true duals 3" with little bullet bufflers and their car can handle it w/o any major modifications..

if you did that on a close to stock v6, youd be in for some power loss.

I dont need anything to prove

[tcrocker162000]

Re: Back Pressure Myth

loss of power or not true duals on a V6 sound nice =]...what is the best exhaust set up for have a faster acceleration rate off the line?

[Blue02]

Re: Back Pressure Myth

Acceleration rate "Off The Line" isn't going to be noticably different no matter what exhaust system. (within reason) Exhaust mods are typically going to show up in the higher rpms.
You want OTL acceleration look at torque converters, lower rear gears, limited slip differential and sticky tires...

[FireEagle22]

Re: Back Pressure Myth

If you put your finger in the path of a hose's exit it won't travel faster or expel the water quicker however it will travel further. Proof that this doesn't work is the following. Okay for those of you that are kinda slow and might not understand what I"m about to say. Try this yourself. Ok so you grab your hose and your turn it on. You let the water run and you see how far it is traveling by holding it in a straight angle without your finger in the hole. Okay what you do next is now you put your finger over the hose. Yes it is traveling farther now so it would seem on first impression that it is traveling faster. But suddenly when you remove your finger and the hole is not restricted anymore. The water now travels a little further than it originally did the first time you let it run without the finger in the way. And this happens for a few seconds before returning to normal. Now why is the water traveling further than it originally did when you let it run unrestricted the first time. I'll tell you why. Because the very fact that putting your finger over the hose doesn't expel it faster it actually expels it slower. So what happens its that the water is getting built up behind your finger and not expelling quick enough. So that when you let it go it comes out in a different, faster and further way than the first time. Therefore smaller pipe doesn't mean faster flow or that it will expel quicker. But it will mean that its traveling further. And like I said earlier the reason for that is. Its because there will be so much back-pressure that it is coming out of it nonstop that it will push it further than lets say a pipe with less back-pressure. Thats why when you put your finger over a hose it travels further not faster.Okay here is one more in case you guys didn't understand that one. Just like lets say. you are exhaling. Much like a car has its exhaust flow. If you cover up one of side of your nose and check to see how far the air goes out of your nose when you exhale normally by putting part of your hand under your nose and moving it further and further away until you can no longer feel it. Sure you'll be feel the air further away with one nostril covered up and the other one exhaling. However it doesn't make it more efficient. Otherwise we would have already evolved to have one nostril. So yeah I hope this was helpful to some of you. And I hope it cleared up that back-pressure myth. And for those of you that still think that 3 inches is overkill or that it seems like you lost power in the lower power-band this is all in your head. Much like when you are in the shower and expecting a phone call you'll be more likely to think you heard the phone ring when you are already thinking someone is going to call you. As supposed when you are not. You'll only hear it when its actually ringing. So in conclusion if it feels like you lost power in the low end its just your head and your convictions going into work.

[ssms5411]

Re: Back Pressure Myth

^ nice read.

[usp55]

Re: Back Pressure Myth

loss of power or not true duals on a V6 sound nice =]...what is the best exhaust set up for have a faster acceleration rate off the line?

I second that!!!
http://www.youtube.com/watch?v=4YfZ2Msn2Ig


I hope to have my true dual H pip setup on my 3.4 w/pacesetters in the next few weeks. I thinking about throwing two cutouts on there also after the H pipe, just cause im curious if its the h pip or the mufflers that makes his setup have zero rasp. Ill post vids. but still u have to admit that vid sounds great. and even better after he cam'd that car (other vid)

oh and my car feels slower with my cutout open (well its stuck open, lol), if its not slower than ill admit i must be crazy but there is without a doubt no low end torq with it open

[LEOMAC23]

Re: Back Pressure Myth

Im not sure about this,but the example of creating velocity the same way as you create it with a garden hose doesnt make sense to me,if your trying to release the gases as fast as possible,then how would this work.When you put your fingr over a garden hose you actually slow the velocity down inside the hose,it doesnt pick up velocity until it exits the hose and thats only because there is less coming out.so you slowing it down inside the pie but it speeds up after the fact??

[FireEagle22]

Re: Back Pressure Myth

That is correct LEOMAC you do slow down the velocity when you put your finger over the hose just like I wrote on the top. Putting your finger over the hose or getting a smaller exhaust pipe won't increase the velocity or expel the exhaust fumes faster. However it will increase the distance the exhaust fumes travel. This happens because it gets so backed up that suddenly an enormous amount of fumes are trying to come out at an alarming rate that each molecule of air is pushing the other one further and further away in an attempt to relieve it. On the other hand when there is no restrictions in a hose or an exhaust pipe there is not enough back-pressure to push them that far. However this does not mean its not expelling them quick enough due to to little backpressure rather than its expelling them faster just not as far. In conclusion when you put your finger over a hose and all the sudden the water is shooting farther its not shooting faster or expelling the fumes faster. Its just shooting them farther just like explained there is so much back pressure that each molecule is pushing the other one further and further away in an effort to relieve that pressure that is keeping it from exiting. That is why when you put your finger over a hose it travels further, not faster nor more efficiently.

[Pewter2K1]

Re: Back Pressure Myth

First... take your finger off the hose..... they went about it the wrong way... if you are going to compare water flowing through a hose you need to put the two ideas in the same context....

Take your typical hose spigot on the side of the house.... you run a 1" hose off the house and 10 feet later the hose sprays the water out say 3 feet hoizontally... now, get yourself a 2" hose and attach it to the house... the same flow of water will only come out maybe 2 feet... the water has to fill the hose and create its own pressure before it makes any movement down the hose...

You can correlate this to the same as exhaust tubing... consider the different engines as different water pressures... if you have standard water pressue on the house, a 1" hose is perfect for that application because it creates a flow and pressure high enough to do work in the yard, run a sprinkler etc.... this is like a honda and its 1.5" exhaust... works fine for a stock car, but will become restrictive once you make more power... if say man my sprinkler isnt working right, must need to put more water to it... so you go out and buy a 2" hose to put on the spigot, turn it on... what do ya know! the sprinkler actually works worse!

So you can see that you must up the output of the source of water (exhaust) to benifit from larger pipes. So in some cases, 3" piping is overkill until you have enough power to push the exhaust through the system.

Putting your finger over the hose is like throwing a tennis ball in the exhaust tip... of course it will restrict the flow and not create any power... its extra velocity AT THE END, not from the source...

Ok, Im done.. just wanted to clear things up...

[ViperRider]

Re: Back Pressure Myth

So for a stock 3.8, the stock piping is best?

[FireEagle22]

Re: Back Pressure Myth

I still disagree that 3 inch on an F-body is overkill. I have heard a lot of people that believe this say this. "Well a 3 inch exhaust is overkill on a 3.8 F body because you need more power to push out the exhaust fumes. So a 3 inch exhaust actually creates back-pressure making it flow worse" And then they go and say "So yeah a 2 1/2 inch exhaust is better because the car needs back-pressure to perform" So I say this let me get this straight. You believe the the car needs back-pressure to perform well. But yet you say that a 3 inch exhaust is bad because it creates backpressure? I mean I don't know about you guys that doesn't make any sense at all.

[FireEagle22]

Re: Back Pressure Myth

Another thing I will add sprinklers and an exhaust have two complete different functions. Sprinklers need a big amount of backpressure because they have to shoot the water out a couple feet in order to get a wider range of water on the designated area. Sure if you put a big *** pipe and try to run the sprinklers on standard pressure its not going to have the sprinkler function because its not going to cover that wide a range of area with Water like a small pipe would. But there is no reason why an exhaust has to shoot exhaust fumes farther. As long as its getting into the exhaust system quicker than on a small pipe it will create more power and less restriction. It's just like going to get a large Soda and grabbing a red stirring coffee straw and saying this is more efficient because its a smaller diameter straw. And I don't know if you guys have ever tried this but you have to suck the crap out of that thing to get the same amount you would out of a bigger straw.

[Disruptore4]

Re: Back Pressure Myth

I think the discussion/explanation has been concentrated on exhaust velocity out of the pipe and getting the exhaust through the system quicker. If you blow into a paper towel roll, you're basically just breathing out, and the breath is going as fast as you are blowing. If you blow through a McDonalds straw (they seem to be a little wider than most other straws) you can still breathe somewhat easily, but something has happened. The speed of the air through the straw has increased, while your breathing still feels normal. The reason for this velocity is to get the exhaust out while it's still hot. (Hot gas moves quicker). If this can be acheived, then you have faster exhaust flow and more efficient exhaust flow. Ever wonder why putting exhaust on a car usually moves the power band of an engine up? Better exhaust system = higher velocity of exhaust gases... Hope some of that made sense, and I know I'm just repeating everything that has already been posted in this.

I have 2.5" Magnaflow w/ high flow cat on my Camaro and it sounds good and runs great, no complaints.

[Disruptore4]

Re: Back Pressure Myth

First... take your finger off the hose..... they went about it the wrong way... if you are going to compare water flowing through a hose you need to put the two ideas in the same context....

Take your typical hose spigot on the side of the house.... you run a 1" hose off the house and 10 feet later the hose sprays the water out say 3 feet hoizontally... now, get yourself a 2" hose and attach it to the house... the same flow of water will only come out maybe 2 feet... the water has to fill the hose and create its own pressure before it makes any movement down the hose...

You can correlate this to the same as exhaust tubing... consider the different engines as different water pressures... if you have standard water pressue on the house, a 1" hose is perfect for that application because it creates a flow and pressure high enough to do work in the yard, run a sprinkler etc.... this is like a honda and its 1.5" exhaust... works fine for a stock car, but will become restrictive once you make more power... if say man my sprinkler isnt working right, must need to put more water to it... so you go out and buy a 2" hose to put on the spigot, turn it on... what do ya know! the sprinkler actually works worse!

So you can see that you must up the output of the source of water (exhaust) to benifit from larger pipes. So in some cases, 3" piping is overkill until you have enough power to push the exhaust through the system.

Putting your finger over the hose is like throwing a tennis ball in the exhaust tip... of course it will restrict the flow and not create any power... its extra velocity AT THE END, not from the source...

Ok, Im done.. just wanted to clear things up...

Didn't read this before posting, this guy is right. It's about the size of the hose tubing, not if you put your finger over the end of the hose... :spank: