Hmmmm. I have true dual MagnaFlows, and their are okay. I never thought they were loud enough. But then again, seeing as I'm into my stereo system / music big-time, and my exhaust has no drone at all, when traveling down the free way, I guess this is not such a bad thing.

If I could "turn it on, and off" at random, I really do like the loud, straight pipe sounding racing exhaust systems..... but I wouldn't want that "all the time".

Oh, but then yesterday I heard a stock F150 getting on it, and I thought.... Yuuuk ! I guess my exhaust does sound pretty good

Peace,
Fish

 

Oooh I wouldn't say that. Then your not agreeing with The Superchips distributer and MGD who say otherwise. MGD is comparing flow rates, a lower flow rate will have a higher amount of back pressure.
According to them, going from a relatively restrictive stock muffler to a magnaflow muffler gets you power because it reduces back pressure. Also according to Superchips_Distributer, going from straight pipes to magnaflow also gets you better power. As he stated in the following quote.
What is the only possible alternative besides adding more flow since that is not possible in a straight pipe system? I'm assuming it is reducing it. The idea is you want some back pressure but not too much and not too little.

But it seems that apparently the only way to get in the optimum amount of back pressure is with a magnaflow and only a magnaflow.

Switched out of personal preference due to sound.

I'm not saying his only aim was to sell a muffler system because I have found many of his posts helpful but everyone has some kind of preference and any result will also have at least a bit of bias. I do not doubt a difference on a dyno because if you make a change, you should, in many cases, expect a change, especially when you are dealing with the maximum flow of the exhaust as seen in the conditions on a dyno. That is expressed in the following post.

Switched because of personal preference for the sound.

I was just throwing my personal preference that I like my flowmaster even though it isn't the one that everyone here likes. I've got friends with just about every kind of exhaust and I think if they are done right and on the right application they sound good. I didn't just go to a store and buy my flowmaster, throw it on and think I'm hot chit. I listened to it on other similar trucks and liked the way it sounded before buying. The two mufflers may have a difference on a dyno but when I have no difference from a real world standpoint, I went with what I think sounds good. I haven't run both mufflers on my truck but I helped a friend with a similar spec'd chevy try just about every single muffler that someone told him was best. He eventually settled for a cherry bomb saying that was the best one because that is the one he liked most. Looking back, he feels they had more of a placebo effect rather than real significan gains or losses. I can run a 16 second 1/4 mile and still easily get 19-22 mpg with the flowmaster. Considering I still run a 16 second 1/4 mile with or without the stock muffler. I dont find the "poorer" flow rates of the flowmaster to be significant. The only changes I saw in a real world application was in mileage between having a muffler to not having one and all I saw was a slight loss in mileage without, as in about 1 mpg on paper.

Besides what ARE the numbers for switching JUST the magnaflow and flowmaster mufflers on the same exact truck under the same conditions? With exhaustive testing there must be some comparable numbers somewhere. I may be losing a few hp but I'm not worried because I've got about 200 more and I rarely need to have them pull all at once. I use my light weight truck as a light weight truck that hauls bikes and boats. I dont go down drag strips or tow 10K so an insignificant loss in power does not matter to me. I've seen up to 8 horse difference between them but how does that compare to stock. That is how you determine if you are, in fact, losing or gaining.

I run it for the sound.

 

Actually, you are the only one throwing around this backpressure mumbo jumbo. Exhaust flow and velocity are not the same thing as this backpressure you speak of. Get with the times man! Backpressure (associated as being necessary with an exhaust system) IS A MYTH!

No one (who knows what they are talking about) has said anything about needing more "backpressure" on this thread except for you. Keep your Flowdisaster for its "backpressure" qualities and everyone else will continue on with reality.

Thats fine if you like your flowmaster for its sound. To each their own. But to argue about backpressure and say that flow through mufflers aren't superior to baffled mufflers, in the realm of potential performance, is just rediculous. These are things that have been PROVEN.


Take a few minutes to read up on this a little, before you continue on your current path of losing all credibility.

"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 "engines 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)."

 

Ok, your right, I always thought that if you had a specific amount of a fluid (liquid or gas) being put into a system at a constant rate and put an obstacle or restriction in its way that it would build an amount of pressure, like when you put your thumb over the end of a water hose. Air velocity, density and pressure must not be related like in Bernoulli's principle.

Your addition to your post is talking about pipe diameter and velocity, not comparing the walls of a baffled muffler. I completely agree that a 2.25" would have a resulting faster flow than a 2.5" or 3" pipe because that is by definition the Bernoulli principle.

So "pressure" was the wrong word but the concept is the velocity of the gas leaving a baffled muffler will not be as fast as the gas leaving a flow through muffler. When the amount of gas entering the pipes remains the same but the final speed is different what do you call the difference ahead of the deciding factor?

I based the best flow off of a post where having the magnaflow would increase power compared to straight dual exhaust. What is the deciding factor between a flow through muffler with pores into a sealed chamber and a flow through pipe that gains power? The "leaks" into the chamber aren't going to speed the gas up further.

I also didn't say baffled muffler are superior to flow through mufflers. Your right, that is rediculous. I'm saying that the gains are not a massive difference on a 4000-6000 pound truck. I say the biggest difference between brands should be sound. A dyno will find a difference much better than a buttometer. But do we take our trucks around on a dyno or on a road?

 

When i look at certain flowmasters, i can defiantly see why it doesnt flow as good, that would be the 50, 70, 80etc. But the 40, 44, and the 10 really dont seem to make me think the restrict flow all that much. a piece of metal in the middle bent in the middle, shouldn't really slow everything down too much. I do like the sound of magnaflow to a certain extent, but again even though they are just vids, i hear a crappy sounding popping at WOT=****. BTW, i don't care about drone, so that can be taken out of the equation here. I have a 44 on my 96 f150 with a 300 and it sounds great, drone and all. The muffler so far has survived a year in the terrible weather in northeast ohio, which includes driving on salty roads in the winter.welds are still good, just doesnt have much black paint left on it.

I've actually looked at the pypes violator and the hooker max flow mufflers. Anybody have some imput on those??

 

Ok, I was just on the phone with Troyer performance. I was correct in that pressure in front of a muffler is, indeed, called backpressure. Meaning that it is not a myth. I'm not sure what else it would be called because it is pressure that is pushing back towards the engine.
Back pressure from a smaller exhaust pipe IS a load of BS because of the previously mentioned natural principle. You will have faster flow in a smaller pipe otherwise you will have pressure, duh.

I got a 2 way answer when I asked if adding a magnaflow in a straight dual pipe setup would add backpressure. The first answer was that yes it does add a small amount of pressure changing from a straight dual to the muffler because of it's design. Then I got the answer that if your running something that is larger like 3 inch exhaust that it would cause a bit of restriction and cause the exiting velocity to be faster.

Again, I will reinforce. I do not keep the flowmaster for it's "backpressure" qualities. I keep it because I like the sound.

And nw150, the extra turns will slow down the flow to an extent. Just not so much in the 40s and such compared to the 80s and such.

 

Hi Longshot - did you talk to Mike himself? Because I can pull up one of his old posts where he says that BP is a myth (actually, the wording is more like 'largely a myth' and irrelevant). You can then present that, and then he'll be talkin' to whomever told you that on the phone




MGD

 

I talked to a guy named mike or michael (not sure because my crappy phone was breaking up while he introduced himself) and he seemed to know what he was talking about. This was also the second guy I talked to. The guy who answered the phone handed it off to someone else because they couldn't answer the first question. The guy I talked to also talked about the benefits of X pipes drawing the gas and heat from the engine among other things while talking about the effects of the magnaflow on true duals.

I guess it depends on the context of the term "back pressure". I use it as meaning a general resistance to flow causing the front ahead of the resistance to be higher than that behind. The post by 700hauler is a myth in that a smaller pipe diameter will cause back pressure. You get a known amount of volume coming in and the rate at which it exits is inversely proportional to the diameter.

And MGD, there is a difference between something being completely false and irrelivent.

 

the X pipe has the same debate


screw both Magnaslow and Slowmasters go with the proven winner Borla

 

We all know backpressure exists. Thats not the issue here. The issue is the misconception that backpressure is a necessity for a well working exhaust. To many people associate having an effective exhaust with having sufficient backpressure. This is where the backpressure as a myth comes into play. Yes backpressure exists, NO backpressure does not have to be present to have a good exhaust system. My argument toward you was soley based on your association of backpressure with a good exhaust which is false, and STILL A MYTH.

 

You said it yourself, the velocity going through a flowthrough muffler will be greater than that of a baffled muffler. Using this reasoning why would you want to use a baffled muffler considering that engines are nothing more than big air pumps? Air in, Air out, and the faster you can accomplish this the more efficient and powerful your engine can be. Why not get the most out of your truck if you are going to spend the money either way?
I get what you are getting at, but you are just aiding in the argument that flow through mufflers like Magnaflow are better. Using your deductions, the ONLY thing that makes the Flowdisaster "better" is its sound (and even that is debatable for most people who dont like obnoxious trucks). Ever heard of the saying, "It sounds fast but it isn't."? Thats the description the Flowmaster falls under for me.

 

http://www.youtube.com/watch?v=B7idXezTq-k

Tell me that doesnt sound good...

 

even darrin likes the flowmaster sound

 

Bingo, I picked the flowmaster because I liked the sound more. Apparently it is different for you but over here most of the magnaflows I see make popping noises if you get on it. But to compare value, mine was $40 (but could get it new for $80) compared to the more expensive magnaflow. The small difference in power didn't matter too much because before I bought mine I tried taking the muffler off for a free(er) flowing exhaust and didn't have much power difference. All my times are within .2 seconds of each other with, quite suprisingly, the stock exhaust holding the fastest time and the free flowing having the worst. Dont ask me why but that is how it was. Then to compare engine efficiency, my worst mileage was on the free flowing exhaust (try paying for 16 mpg on the highway when your used to 19). I also used my experience on other trucks and went with the sound I liked most.


Actually I'm not too thrilled about the clatter on that one. I like my deeper lope style lub.

 

OK I'll try. Here we go. That doesn't sound good....

I DID IT!