First let me start off by saying I may not be 100% correct, if not please correct me (have evidince to prove me wrong though please)
Second, maybe Im just getting awrney (sp) as Im getting older, or my life situations are causing me to be such a dick lately (more so that usual )

To the point. Ive been noticing a lot of threads with agrivating things people post/ask. (I dont necessarly get agrivated but threads where someone is getting agrivated by calling something it isnt.)
Some people get annoyed when we (as a general) refer to a torque converter with a higher than stock stall speed as a "stall" Some dont like refering to an engine as a "motor" etc things like this.

What gets me (today at least ) is the referencing to "back pressure" This is where I would like to be corrected if Im wrong. Just know that I know everything Im just not always right But what people are usually refering to is actually Scavenging. ANY back pressure is bad, the misconception is that when you increase your pipe diameter or lessen the restriction in your exhaust you loose low end power cause of the loss of back pressure. This is not true. When you lessen the restriction, sometimes you let the exhaust gases slow down there by decreasing the velocity that the gases exit, causing you to loose some scavenging effect and this is where the loss comes from.

I know a few things about flows and pipe sizes/restrictions (this is what I do for a living) And ANYTIME you change pipe size your (for a given flow) your pressure, or velocity will change. If you maintain the same pressure, the speed will increase/decrease inverse to the pipe change (go bigger pipe, the pressure will decrease, and vice versa) OR your velocity will change (if your pressure stays the same, and your pipe size increases the flow will slow down) This is where you loose your low end power. If you go (to an extent) to a smaller pipe, you are keeping the pressure and velocitys high, wich creates the scavenging effect giving you the power you want. When you go with a larger pipe/header primary etc, you are letting the gases expand wich let them cool down and the velocity decreases causing the loss of power.

Discuss (getting tired of typing)

 

what he said.

 

 

I concur.

 

i agree with the theory, here's my argument though.


if a smaller diameter pipe is more condusive to a scavanging effect, why would you ever want a bigger pipe, if it causes a horsepower/torque loss due to a drop in velocity?

i think this theory is correct...... but it is relative to rpm and displacement. So, losing "backpressure" in essence will cause a loss in horsepower/torque at lower rpms, but it will enable more capability at a higher rpm.

that being said, displacement will affect it in a similar way.

if there's a stall and a cam, big pipes are the way to go, because you bypass the low rpms.
if you're running a stock engine, with no stall, than smaller pipes will help you.


so after all this, it is a truly an application by application argument. no?

 

Your Wrong
























Maybe not in this instance but you know your wrong

 

I agree with the principle, but you have to think about the massive flow and velocity increase as rpms go up.

That being said, hot girl like fat guys with big pipes....................

 

Loudazzlow, and snake eater. Yall are both very correct especially with the displacement/upper rpm points, I got tired of typing earlier The higher you rev the engine, or more displacement you have, the more velocity you have. There is a happy medium, but most people tend to "over exhaust" their systems Correct? I for one dont see any gain using true dual 3" on a N/A 5.3 with only bolt ons.

Hell (I need to get some true dyno numbers) I believe Im between 350-375 to the tires, and I think my single 3" is better for my application than dual 2.5

 

i argee with ya 100%

 

*** da boat of ya