Performance Loss With Loudmouth?

[Noobz347]

Magnaflow Magnapacks or Borla Stingers. I personally like the Stingers just a bit better.

Magnaflow Magnapacks Catback with Mac O/R H pipe - YouTube

2003 Mustang Gt Borla Stinger Bassani O/R X - YouTube

Not too loud at part throttle, but it gets REALLY loud when you get on it. What midpipe and headers will you be running?


Also, about the loss in low end torque. It is of my personal opinion that that is complete BS. I've heard it SO much on so many different forums, and I've never once seen any proof to back it up. My personal experience is a .2 second and nearly 2 mph gain in the 1/4 mile with an offroad midpipe and catback. And just because I'm bored right now, I'll go into a more in-depth explanation.

Back pressure, which is simply the force against the air flow created by catalytic converters, restrictive mufflers, bad bends in the pipe, etc., is ALWAYS a bad thing. Yes, your car requires a certain amount to do some complicated stuff inside the heads, but that amount is easily provided by the friction losses and aerodynamic drag created from simply moving the air from the front of the car to the rear via the exhaust pipes. The cats create quite a bit of back pressure, and removing the cats (and/or restrictive muffler) will decrease that pressure and create more power.

The problem most people have is separating back pressure from exhaust velocity. Faster moving air helps pull the exhaust gases out of the combustion chamber better (read: scavenging), which is the reason why long tube headers work. Your factory exhaust has a 2.25 inch diameter, from the exhaust manifolds back. If you replace that with a 3 inch exhaust, the speed of the air moving through those pipes is going to decrease (as per some relatively simply fluid dynamics principles), although not by a whole lot because the 2.25 inch piping itself isn't really restricting much in the first place. So, slower moving exhaust = less torque.

When you go and put an offroad midpipe and/or catback on your Mustang, you are both removing back pressure (by removing the cats, better flowing pipe bends, etc.) and decreasing the exhaust velocity (by increasing the diameter of the pipe). However, the amount of power/torque you gain by removing the back pressure is MUCH greater than the amount of torque you lose from the decreased exhaust velocities.

Make sense?

This post should be a sticky. I get tired of explaining the difference between back pressure and poor exhaust scavenging. With any exhaust system, there is a BALANCE. That's why there exists such a thing as a Tuned Exhaust System and also why I chuckle when I see exhaust manufacturers talk about how their products will increase HP with no dyno data to back it up.

 

[hawkfish78]

so i got my slp lm1's on today. let me tell you they sound a whole lot better than flowmaster 40's. they have a louder idle and sound a lot cleaner and smoother. i didnt feel any loss in power. when i get on the highway all i hear is drone with the flows and it was horrible with the slp's they have no drone at all they are quiet when cruising but when you get on the pedal they scream they are awesome. they have deep tone to them also not just loud. they are a good muffler if you have emissions strict state or you wanna get the cats on. they are a pain to install but they are worth it to me they sound so much better than the flows

How was it a pain to install? Did you weld them or clamp them?

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[hawkfish78]

Whereabouts in Oregon? If you want and are in the pdx area, pm me and I'll have you come to one of our mustang meets. You can hear the combo of bassani x(w/cats) and Borla CB (stinger).

It's loud as hell, and the best combo I think I've ever heard.

I live in Portland, so I might take you up on that. Is anyone using loudmouths, I'd also like to hear those in person.

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[jzhgt19]

I just bought the mufflers and had them welded in. They are a center center muffler instead of offset offset. Many shops around me suck ( I hate it) they said there is no way they would get on finally found some shop by me that said they could do it in about an hour, about two and a half hours later they were on. Needed some custom work but well worth the 75 bucks for install. Just took time that's all but they sound great to me

 

[fiveohwblow]

I live in Portland, so I might take you up on that. Is anyone using loudmouths, I'd also like to hear those in person.

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Sounds good. Used to have a guy with a 4.6 and LM's but he sold. I'll see if anyone else is running them.

 

[Kornnut]

I live in Portland, so I might take you up on that. Is anyone using loudmouths, I'd also like to hear those in person.

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I have posted vids of mine before. Just search my name and you will find them. If not I will post some when I get off work tonight.

 

[Stan Weiss]

Magnaflow Magnapacks or Borla Stingers. I personally like the Stingers just a bit better.

Magnaflow Magnapacks Catback with Mac O/R H pipe - YouTube

2003 Mustang Gt Borla Stinger Bassani O/R X - YouTube

Not too loud at part throttle, but it gets REALLY loud when you get on it. What midpipe and headers will you be running?


Also, about the loss in low end torque. It is of my personal opinion that that is complete BS. I've heard it SO much on so many different forums, and I've never once seen any proof to back it up. My personal experience is a .2 second and nearly 2 mph gain in the 1/4 mile with an offroad midpipe and catback. And just because I'm bored right now, I'll go into a more in-depth explanation.

Back pressure, which is simply the force against the air flow created by catalytic converters, restrictive mufflers, bad bends in the pipe, etc., is ALWAYS a bad thing. Yes, your car requires a certain amount to do some complicated stuff inside the heads, but that amount is easily provided by the friction losses and aerodynamic drag created from simply moving the air from the front of the car to the rear via the exhaust pipes. The cats create quite a bit of back pressure, and removing the cats (and/or restrictive muffler) will decrease that pressure and create more power.

The problem most people have is separating back pressure from exhaust velocity. Faster moving air helps pull the exhaust gases out of the combustion chamber better (read: scavenging), which is the reason why long tube headers work. Your factory exhaust has a 2.25 inch diameter, from the exhaust manifolds back. If you replace that with a 3 inch exhaust, the speed of the air moving through those pipes is going to decrease (as per some relatively simply fluid dynamics principles), although not by a whole lot because the 2.25 inch piping itself isn't really restricting much in the first place. So, slower moving exhaust = less torque.

When you go and put an offroad midpipe and/or catback on your Mustang, you are both removing back pressure (by removing the cats, better flowing pipe bends, etc.) and decreasing the exhaust velocity (by increasing the diameter of the pipe). However, the amount of power/torque you gain by removing the back pressure is MUCH greater than the amount of torque you lose from the decreased exhaust velocities.

Make sense?

The pipe numbers are for the outside diameter, but since I do not know the wall thickness I will use 2.25" and 3"

► (2.25/2)^2*pi = 3.976078202199582 sq inches csa
► (3.00/2)^2*pi = 7.068583470577035 sq inches csa
► 7.068583470577035/3.976078202199582 = 1.777777777777778 increase in csa

FPS = ( CFM / CSA ) * 2.4

Stan

 

[fast97gt]

I had lm1s on my 97 with pi engine swap with a bassani o/r-x pipe and absolutely loved it. Sorry I don't have a clip, but I think you'd be happy with em

 

[Deleted member 38176]

I had lm1s on my 97 with pi engine swap with a bassani o/r-x pipe and absolutely loved it. Sorry I don't have a clip, but I think you'd be happy with em

LM1's with an O/R midpipe?

 

[BlackArtemis]

I had no performance loss.
Here is my 2002 GT with BBK Lts, and catted H and LM1. I love it, but I think any SLP product with an X pipe sounds horrid.

2002 Mustang GT BBK LTs, catted H, and SLP LM1's - YouTube

 

[Deleted member 38176]

I had no performance loss.
Here is my 2002 GT with BBK Lts, and catted H and LM1. I love it, but I think any SLP product with an X pipe sounds horrid.

2002 Mustang GT BBK LTs, catted H, and SLP LM1's - YouTube

Well well, look what the cat dragged in.....

 

[sneaky98gt]

The pipe numbers are for the outside diameter, but since I do not know the wall thickness I will use 2.25" and 3"

► (2.25/2)^2*pi = 3.976078202199582 sq inches csa
► (3.00/2)^2*pi = 7.068583470577035 sq inches csa
► 7.068583470577035/3.976078202199582 = 1.777777777777778 increase in csa

FPS = ( CFM / CSA ) * 2.4

Stan

You're right. I shouldn't have used 3 inches in my example, as almost no one uses a 3 inch pipe, and the people who do are either ignorant or are making enough power that the loss in velocity is insignificant.

99% of street 'Stangs out there use 2.5 inch mid pipes, which the area is 4.9087 square inches. A 1.23456789 increase in cross sectional area. (As a side note, that's crazy that (1.25^2)/(1.125^2) is 1.234567890....)

While I don't have any scientific evidence or anything, I still hold that that amount of decrease in exhaust velocity is vastly overshadowed by the reduced backpressure from the cats. And don't forget that the restriction caused by the cats also reduces the velocity.

 

[Stan Weiss]

You're right. I shouldn't have used 3 inches in my example, as almost no one uses a 3 inch pipe, and the people who do are either ignorant or are making enough power that the loss in velocity is insignificant.

99% of street 'Stangs out there use 2.5 inch mid pipes, which the area is 4.9087 square inches. A 1.23456789 increase in cross sectional area. (As a side note, that's crazy that (1.125^2)/(1.25^2) is 1.234567890....)

While I don't have any scientific evidence or anything, I still hold that that amount of decrease in exhaust velocity is vastly overshadowed by the reduced backpressure from the cats. And don't forget that the restriction caused by the cats also reduces the velocity.

The other point that I was trying to make and left out was you need to look at the difference in csa because looking pipe diameter will not give you the correct increase in area or change in velocity.

► 3 / 2.25 = 1.333333333333333

Also so no one is confused you have the sizes reversed.

► (1.25^2)/(1.125^2) = 1.23456790

Stan

 

[txredgt]

LM1's with an O/R midpipe?

That's what I'm rocking right now. Yes I want a catted mid but at 450 bucks for a long tube catted mid pipe I would rather spend that money elsewhere.

 

[Deleted member 38176]

That's what I'm rocking right now. Yes I want a catted mid but at 450 bucks for a long tube catted mid pipe I would rather spend that money elsewhere.

Any sound clips?

 

[Lugnuts]

Just extra information because I want to hear myself talk I guess.
Exhaust is far more complicated than what is laid out here but there is a large window of acceptable combinations that will provide decent return. The fact is that if you are not in a restricted, super competitive (limited) class then the returns are simply not worth the fraction of improvement. But if you have the time and are going to spend the money anyway, why not exercise some research and math skills and get the most for your money? Honestly there are tons of ways to improve your exhaust system but do you want to improve it or max it out for your combination?
Scavenging is a very mild supercharging effect that is influenced by multiple factors but the primary influence is the cam selection. In principle, the intake and exhaust valves are open at the same time briefly during the end of the exhaust stroke/beginning of the intake stroke. The exhaust velocity leaving the cylinder creates a small amount of vacuum which sucks in intake charge once the intake valve is opened until the closing of the exhaust valve - this increase in intake charge merits more power in a calculated rpm as you add more fuel and air than typically possible at atmospheric conditions. Down low the result is a decrease of power as you have a small amount of fresh intake charge blowing out through the exhaust without creating enough velocity to compensate during the span of the intake stroke and this nets you with a less dense intake charge - but at the rpm calculated (if you did your homework right) you will have good increase in performance. While the camshaft overlap of intake and exhaust is required to do this, the entire exhaust system will effect the total results. To determine where in the rpm the return occurs and how well it works you have to get the velocity correct - pipes with as little restriction as possible but with the correct velocity for the application (so not too big and not too small). If you really want to get deep into it you will have to incorporate the exhaust pulse into the equation. There is a resonance created by the exhaust pulse that bounces through the exhaust system. As the wave of the pulse propagates through the exhaust system there is a low pressure wave immediately behind the high pressure pulse. If you can time this resonance to occur at the valve when the exhaust valve opens, you will have a high pressure cylinder exhausting into a lower than normal pressure wave of the pulse which will increase the initial speed of emptying the cylinder. While many will immediately dismiss the benefits of this, it is why the better performance header manufacturers make "equal length" units. While they are not perfect for every application, they get you much closer to the point where you can take advantage of this pulse. Consider that they are going to the extra effort of making the tubes equal length in such a confined space - do you really think they would go through all that headache if it were not beneficial?
The moral of the story is that you can improve performance without factoring in all this information. If you have a 2" system and you go 2-1/2" you will improve breathing. But you can improve your exhaust or you can tune your exhaust. If you are gonna replace it anyway - why not max it out?

As far as liking it loud, put some cutouts on it and call it a day.... This way you can enjoy it loud and quiet it down where necessary for noise ordinances.

 

[Stumbaugh]

For those saying that mufflers do not offer any sort of performance gain over any other. Here is a thread to prove you wrong. A guy over on Corral with a supercharged car swapped over to 3" exhaust from 2.5" to do a comparison on power. He had some full body Magnaflow mufflers laying around, along with some Mac flowpath's. So he decided to do a comparison of the 2 mufflers in 3" form. The Mac flowpaths made 40+rwhp over the magnaflows at 5200rpm. Here is the thread:

MAC Flowpath vs Magnaflow Dyno results - Ford Mustang Forums : Corral.net Mustang Forum

 

[Gearbanger 101]

For those saying that mufflers do not offer any sort of performance gain over any other. Here is a thread to prove you wrong. A guy over on Corral with a supercharged car swapped over to 3" exhaust from 2.5" to do a comparison on power. He had some full body Magnaflow mufflers laying around, along with some Mac flowpath's. So he decided to do a comparison of the 2 mufflers in 3" form. The Mac flowpaths made 40+rwhp over the magnaflows at 5200rpm. Here is the thread:

MAC Flowpath vs Magnaflow Dyno results - Ford Mustang Forums : Corral.net Mustang Forum

He picked up/lost that 40rwhp+ because of tuning issues would be my guess. Not because one muffler was vastly superior to another. Also, the Magnaflows need to "break in" before seeing their full performance value. Not to mention....I’ve seen 800hp cars vary that much in horsepower from one dyno day, to the next. Exact figures are pretty tough to repeat at that horsepower level considering how much temperature, barometric pressure, humidity, under hood temps, etc can affect their output.

 

[Stumbaugh]

He picked up that 40rwhp+ because he went from a 2 1/2" exhaust, to a 3" exhaust....not because of the type of muffler he was running.

If you would have read the thread, you would know that's not true, here's a little break down for you.

He had a 2.5" prochamber, with a 2.5" Mac flowpath cat back and then swapped to a 3" prochamber with a 3" Mac flowmath catback and gained 45rwhp.

He then had a set of 3" Magnaflow mufflers laying around that he swapped in and lost 45rwhp.

He said when he swapped from the 2.5" to 3", he had to add in a lot more fuel because it was moving a lot more air. When he put the Magnaflow's on, the car was bad rich because it was not moving as much air, so they had to retune it for the Magnaflows. He has dyno graphs in the thread and you can clearly see that it loses power all through out the power band, as well as torque.

FYI: The car was tuned for the Mac flowpaths, then tuned for the Magnaflows. He said they spent a good while tuning it with the magnaflows on and that it was simply down in power.

 

[Gearbanger 101]

If you would have read the thread, you would know that's not true, here's a little break down for you.

He had a 2.5" prochamber, with a 2.5" Mac flowpath cat back and then swapped to a 3" prochamber with a 3" Mac flowmath catback and gained 45rwhp.

He then had a set of 3" Magnaflow mufflers laying around that he swapped in and lost 45rwhp.

He said when he swapped from the 2.5" to 3", he had to add in a lot more fuel because it was moving a lot more air. When he put the Magnaflow's on, the car was bad rich because it was not moving as much air, so they had to retune it for the Magnaflows. He has dyno graphs in the thread and you can clearly see that it loses power all through out the power band, as well as torque.

FYI: The car was tuned for the Mac flowpaths, then tuned for the Magnaflows. He said they spent a good while tuning it with the magnaflows on and that it was simply down in power.

Yeah, re-read it....read my edit above.