BE CAREFUL SLP LOUDMOUTHS LOOSE HORSEPOWER.
06-18-2006, 02:20 PM
#23
5th Gear Member
Join Date: Mar 2006
Location:
Posts: 2,544
RE: BE CAREFUL SLP LOUDMOUTHS LOOSE HORSEPOWER.
Let me see if I can explain this:
There are two basic factors in an exhaust system that are often confused with each other:
1) "Backpressure", which is better called "static impediment to flow". This includes things such as baffled mufflers, narrowed-down sections in the exhaust tubing, crimped joints, very tight bends, or turbulence-enducing "defects" like rough castings/tubing, poor quality welds that stick out into the exhaust flow area, badly matched tubing joints, and so forth. Factors like this --backpressure-- always cost you horsepower, period.
2) The second factor, and the most mis-understood, is the tuning (resonance and other) of the exhaust system to suit the engine. This is based on complex physics, but it has to do with the diameter and the length of the exhaust pipes, especially those closest to the engine. (For example, header primaries). This can sometimes cost you power and sometimes make you power.
If your engine is properly tuned (as earlier posters discussed re-jetting carbs), then lowering backpressure (#1 above) will ALWAYS be beneficial to your engine. It might give you a lot of HP, it might give you a little, but it will never hurt you. I'll say that again so it's clear. If your engine is properly tuned, reducing backpressure will NEVER hurt performance.
The second factor, tuning/resonance, is complex. Let's do an example. Suppose that I have a relatively small displacement V8, such as our 4.6L. Suppose then that I buy a set of long-tube headers with HUGE primary tubes, like pro drag race headers that were meant for a 500+ cubic inch big-block making 2,000 HP or more. Pretend for a moment that these headers would bolt up to my 4.6. What happens?
Well, on the one hand, I've reduced the restiction in the exhaust because the smooth bends of the headers are much less restrictive than the OEM manifolds.
On the other hand, I've completely changed the tuning of the exhaust. Those giant-diameter headers are going to be ill suited for my 4.6 "street engine" becasue the resonant characteristics are a very poor match. This will probably cost me HP.
So what's the conclusion? More than likely, I will LOOSE a lot of power through most of the RPM range. Someone that didn't know any better might say You lost HP becasue those big headers had too little back-pressure. That is WRONG. The backpressure (restriction) isn't the problem. The problem is that the big block drag headers aren't a good tuning match for the engine.
Tuning is complicated, but it works a bit like this:
First off, the diameter of a tube affects the velocity of the gases that flow through it. An engine running at a certain RPM is going to be emitting a certain volume of exhaust gas. A "smaller" tube makes the gases flow faster (and if it's small enough, becomes a restriction). A "larger" tube slows down the gases. There is a delicate trade-off here. High speed flow is good for scavenging in a naturally-aspirated motor. BUT, too narrow of a tube, causes backpressure at high RPM (as above). That's why a set of headers needs to be matched to the engine. It needs to have tubes that are sized correctly to give good velocity and scavenging, but not too small, as to hurt high RPM power.
In our earlier example, the big-block headers don't work on a small V8 becasue the tubes are so big (for the exhaust flow of the small engine) that the velocity drops and scavenging suffers. It's not the "backpressure" that causes a problem here, it's the improper tuning!
A second kind of tuning has to do with matching the lengths of the piping (usually header primaries) with the characteristics of the engine. Any pipe will resonate at a given frequnecy. (That's how wind instruments, like a trumpet, work folks) The frequnecy has to do with the length of the tube and its diameter. People that design headers come up with specific lengths and diameter combinations that make them work with certain engines. On professional race cars, this goes even further, into the X/H-pipes, and even the full length of the tail-pipe, and shape of the muffler(s).
So, it's possible to have an exhaust mod that reduces backpressure (always good) but AT THE SAME TIME screws up "tuning" in one way or another. If the tuning screwup is worse than the backpressure reduction, then people might say "that mod has too little backpressure". Bull$hit. The backpressure is fine, it's the tuning that's messed up.
You can see this in many common aftermarket mods.
For example, Shorty Headers. Shorty headers drop backpressure becasue they are freer flowing compared to the cast stock manifolds. But, Shorty Headers aren't really "tuned" at all. Consequently, they give you a small HP gain: 3-5 HP tops.
Long Tube headers, on the other hand, drop backpressure AND they are properly tuned. In fact, I'll bet that on a flow bench you couldn't even tell the difference between shorty headers and long-tubes purely on a basis of static flow. BUT, properly sized longtubes are worth 20-30 HP, or more, on our cars. Most of that gain is becasue they are properly tuned.
Like our earlier example, if you were to bolt on a "bad" set of Longtube headers--ones with too small or loo large primaries, the backpressure would still be lessened compared to stock, but the tuning would be all kinds of wrong. This is one of those things that people are going to call "too little backpressure", but again, backpressure isn't the issue.
All this being said, I don't belive for a minute that the SLP mufflers will cost you HP, so long as the engine is properly tuned (correct A/R ratio).
There are two basic factors in an exhaust system that are often confused with each other:
1) "Backpressure", which is better called "static impediment to flow". This includes things such as baffled mufflers, narrowed-down sections in the exhaust tubing, crimped joints, very tight bends, or turbulence-enducing "defects" like rough castings/tubing, poor quality welds that stick out into the exhaust flow area, badly matched tubing joints, and so forth. Factors like this --backpressure-- always cost you horsepower, period.
2) The second factor, and the most mis-understood, is the tuning (resonance and other) of the exhaust system to suit the engine. This is based on complex physics, but it has to do with the diameter and the length of the exhaust pipes, especially those closest to the engine. (For example, header primaries). This can sometimes cost you power and sometimes make you power.
If your engine is properly tuned (as earlier posters discussed re-jetting carbs), then lowering backpressure (#1 above) will ALWAYS be beneficial to your engine. It might give you a lot of HP, it might give you a little, but it will never hurt you. I'll say that again so it's clear. If your engine is properly tuned, reducing backpressure will NEVER hurt performance.
The second factor, tuning/resonance, is complex. Let's do an example. Suppose that I have a relatively small displacement V8, such as our 4.6L. Suppose then that I buy a set of long-tube headers with HUGE primary tubes, like pro drag race headers that were meant for a 500+ cubic inch big-block making 2,000 HP or more. Pretend for a moment that these headers would bolt up to my 4.6. What happens?
Well, on the one hand, I've reduced the restiction in the exhaust because the smooth bends of the headers are much less restrictive than the OEM manifolds.
On the other hand, I've completely changed the tuning of the exhaust. Those giant-diameter headers are going to be ill suited for my 4.6 "street engine" becasue the resonant characteristics are a very poor match. This will probably cost me HP.
So what's the conclusion? More than likely, I will LOOSE a lot of power through most of the RPM range. Someone that didn't know any better might say You lost HP becasue those big headers had too little back-pressure. That is WRONG. The backpressure (restriction) isn't the problem. The problem is that the big block drag headers aren't a good tuning match for the engine.
Tuning is complicated, but it works a bit like this:
First off, the diameter of a tube affects the velocity of the gases that flow through it. An engine running at a certain RPM is going to be emitting a certain volume of exhaust gas. A "smaller" tube makes the gases flow faster (and if it's small enough, becomes a restriction). A "larger" tube slows down the gases. There is a delicate trade-off here. High speed flow is good for scavenging in a naturally-aspirated motor. BUT, too narrow of a tube, causes backpressure at high RPM (as above). That's why a set of headers needs to be matched to the engine. It needs to have tubes that are sized correctly to give good velocity and scavenging, but not too small, as to hurt high RPM power.
In our earlier example, the big-block headers don't work on a small V8 becasue the tubes are so big (for the exhaust flow of the small engine) that the velocity drops and scavenging suffers. It's not the "backpressure" that causes a problem here, it's the improper tuning!
A second kind of tuning has to do with matching the lengths of the piping (usually header primaries) with the characteristics of the engine. Any pipe will resonate at a given frequnecy. (That's how wind instruments, like a trumpet, work folks) The frequnecy has to do with the length of the tube and its diameter. People that design headers come up with specific lengths and diameter combinations that make them work with certain engines. On professional race cars, this goes even further, into the X/H-pipes, and even the full length of the tail-pipe, and shape of the muffler(s).
So, it's possible to have an exhaust mod that reduces backpressure (always good) but AT THE SAME TIME screws up "tuning" in one way or another. If the tuning screwup is worse than the backpressure reduction, then people might say "that mod has too little backpressure". Bull$hit. The backpressure is fine, it's the tuning that's messed up.
You can see this in many common aftermarket mods.
For example, Shorty Headers. Shorty headers drop backpressure becasue they are freer flowing compared to the cast stock manifolds. But, Shorty Headers aren't really "tuned" at all. Consequently, they give you a small HP gain: 3-5 HP tops.
Long Tube headers, on the other hand, drop backpressure AND they are properly tuned. In fact, I'll bet that on a flow bench you couldn't even tell the difference between shorty headers and long-tubes purely on a basis of static flow. BUT, properly sized longtubes are worth 20-30 HP, or more, on our cars. Most of that gain is becasue they are properly tuned.
Like our earlier example, if you were to bolt on a "bad" set of Longtube headers--ones with too small or loo large primaries, the backpressure would still be lessened compared to stock, but the tuning would be all kinds of wrong. This is one of those things that people are going to call "too little backpressure", but again, backpressure isn't the issue.
All this being said, I don't belive for a minute that the SLP mufflers will cost you HP, so long as the engine is properly tuned (correct A/R ratio).
06-18-2006, 03:36 PM
#25
2nd Gear Member
Join Date: Mar 2006
Location:
Posts: 170
RE: BE CAREFUL SLP LOUDMOUTHS LOOSE HORSEPOWER.
ok i get it now.. thx for your help crazy Al, one more question tho.. what if i keep my STOCK headers and go with a MAC O/R H PIPE?? with FLOWMASTER mufflers?! will that be ok or not? i dont have money for the longtubes yet, so i prolly wont get them for awhile.
06-18-2006, 03:54 PM
#27
1st Gear Member
Thread Starter
Join Date: Nov 2005
Location:
Posts: 76
RE: BE CAREFUL SLP LOUDMOUTHS LOOSE HORSEPOWER.
You are full of CRAP.
Had many cars with SLPs and loud mufflers, I'm happier with the ones I have.
[sm=icon_stickpoke.gif]
Had many cars with SLPs and loud mufflers, I'm happier with the ones I have.
[sm=icon_stickpoke.gif]
ORIGINAL: 2GKT5
I think someone with the Power Flos just heard the Loudmouths in person and is PO'd 
ORIGINAL: Pony Up
I see a bunch of stuff about the LM's here lately. Yes they are loud (do sound like a blugging boat at idle though) and they do sound good but when I called SLP directly and asked their teck about horse power issues hew did tell me the Loudmouths "DO make the 05-06 Mustangs loose horsepower". He said in order for the set to make sense one must use headers and off road mid pipes amunst other things. He said and I quote "Most dummies just like the sound and are sport car want to be's" as he chuckled. Said they did many different dyno"s to prove this.
Hmmm. Made me think of something else. I did ask if the Power flos had issuse and he said they "DID NOT rid the car of any horsepower". I did buy the Power Flos instead of the Loudmouths. They do have a deeper rumble but are not as "loud" as the LM's.
Just thought I"d chime in and let people who want horsepower "gains" know.
I see a bunch of stuff about the LM's here lately. Yes they are loud (do sound like a blugging boat at idle though) and they do sound good but when I called SLP directly and asked their teck about horse power issues hew did tell me the Loudmouths "DO make the 05-06 Mustangs loose horsepower". He said in order for the set to make sense one must use headers and off road mid pipes amunst other things. He said and I quote "Most dummies just like the sound and are sport car want to be's" as he chuckled. Said they did many different dyno"s to prove this.
Hmmm. Made me think of something else. I did ask if the Power flos had issuse and he said they "DID NOT rid the car of any horsepower". I did buy the Power Flos instead of the Loudmouths. They do have a deeper rumble but are not as "loud" as the LM's.
Just thought I"d chime in and let people who want horsepower "gains" know.
06-18-2006, 04:14 PM
#28
5th Gear Member
Join Date: Mar 2006
Location:
Posts: 2,544
RE: BE CAREFUL SLP LOUDMOUTHS LOOSE HORSEPOWER.
What is probably happening is that when you add the SLP loudmouths, they produce an acoustic wave that causes constructive sound wave interference at various rpms in the exhaust system and this is what causes the loss of HP. What this does is actually cause a sonic node of backpressure that drops your HP!!
ORIGINAL: Reaper
ok i get it now.. thx for your help crazy Al, one more question tho.. what if i keep my STOCK headers and go with a MAC O/R H PIPE?? with FLOWMASTER mufflers?! will that be ok or not? i dont have money for the longtubes yet, so i prolly wont get them for awhile.
ok i get it now.. thx for your help crazy Al, one more question tho.. what if i keep my STOCK headers and go with a MAC O/R H PIPE?? with FLOWMASTER mufflers?! will that be ok or not? i dont have money for the longtubes yet, so i prolly wont get them for awhile.
The O/R H-pipe (any brand) will give you HP becasue it eliminates the restriction of the factory cats. It is basically "tuning neutral". I would expect it to be just fine, and to give you a moderate HP gain. I would be expecting 5-10 HP tops. Note that this is a guess, I haven't seen any dyno stuff on this.
I would definatley save up for the longtubes. That is where the biggest HP gain is possible on the 'stang exhuast.
06-18-2006, 05:18 PM
#29
5th Gear Member
Join Date: May 2006
Location: Florida
Posts: 3,881
RE: BE CAREFUL SLP LOUDMOUTHS LOOSE HORSEPOWER.
ORIGINAL: CrazyAl
Let me see if I can explain this:
There are two basic factors in an exhaust system that are often confused with each other:
1) "Backpressure", which is better called "static impediment to flow". This includes things such as baffled mufflers, narrowed-down sections in the exhaust tubing, crimped joints, very tight bends, or turbulence-enducing "defects" like rough castings/tubing, poor quality welds that stick out into the exhaust flow area, badly matched tubing joints, and so forth. Factors like this --backpressure-- always cost you horsepower, period.
2) The second factor, and the most mis-understood, is the tuning (resonance and other) of the exhaust system to suit the engine. This is based on complex physics, but it has to do with the diameter and the length of the exhaust pipes, especially those closest to the engine. (For example, header primaries). This can sometimes cost you power and sometimes make you power.
If your engine is properly tuned (as earlier posters discussed re-jetting carbs), then lowering backpressure (#1 above) will ALWAYS be beneficial to your engine. It might give you a lot of HP, it might give you a little, but it will never hurt you. I'll say that again so it's clear. If your engine is properly tuned, reducing backpressure will NEVER hurt performance.
The second factor, tuning/resonance, is complex. Let's do an example. Suppose that I have a relatively small displacement V8, such as our 4.6L. Suppose then that I buy a set of long-tube headers with HUGE primary tubes, like pro drag race headers that were meant for a 500+ cubic inch big-block making 2,000 HP or more. Pretend for a moment that these headers would bolt up to my 4.6. What happens?
Well, on the one hand, I've reduced the restiction in the exhaust because the smooth bends of the headers are much less restrictive than the OEM manifolds.
On the other hand, I've completely changed the tuning of the exhaust. Those giant-diameter headers are going to be ill suited for my 4.6 "street engine" becasue the resonant characteristics are a very poor match. This will probably cost me HP.
So what's the conclusion? More than likely, I will LOOSE a lot of power through most of the RPM range. Someone that didn't know any better might say You lost HP becasue those big headers had too little back-pressure. That is WRONG. The backpressure (restriction) isn't the problem. The problem is that the big block drag headers aren't a good tuning match for the engine.
Tuning is complicated, but it works a bit like this:
First off, the diameter of a tube affects the velocity of the gases that flow through it. An engine running at a certain RPM is going to be emitting a certain volume of exhaust gas. A "smaller" tube makes the gases flow faster (and if it's small enough, becomes a restriction). A "larger" tube slows down the gases. There is a delicate trade-off here. High speed flow is good for scavenging in a naturally-aspirated motor. BUT, too narrow of a tube, causes backpressure at high RPM (as above). That's why a set of headers needs to be matched to the engine. It needs to have tubes that are sized correctly to give good velocity and scavenging, but not too small, as to hurt high RPM power.
In our earlier example, the big-block headers don't work on a small V8 becasue the tubes are so big (for the exhaust flow of the small engine) that the velocity drops and scavenging suffers. It's not the "backpressure" that causes a problem here, it's the improper tuning!
A second kind of tuning has to do with matching the lengths of the piping (usually header primaries) with the characteristics of the engine. Any pipe will resonate at a given frequnecy. (That's how wind instruments, like a trumpet, work folks) The frequnecy has to do with the length of the tube and its diameter. People that design headers come up with specific lengths and diameter combinations that make them work with certain engines. On professional race cars, this goes even further, into the X/H-pipes, and even the full length of the tail-pipe, and shape of the muffler(s).
So, it's possible to have an exhaust mod that reduces backpressure (always good) but AT THE SAME TIME screws up "tuning" in one way or another. If the tuning screwup is worse than the backpressure reduction, then people might say "that mod has too little backpressure". Bull$hit. The backpressure is fine, it's the tuning that's messed up.
You can see this in many common aftermarket mods.
For example, Shorty Headers. Shorty headers drop backpressure becasue they are freer flowing compared to the cast stock manifolds. But, Shorty Headers aren't really "tuned" at all. Consequently, they give you a small HP gain: 3-5 HP tops.
Long Tube headers, on the other hand, drop backpressure AND they are properly tuned. In fact, I'll bet that on a flow bench you couldn't even tell the difference between shorty headers and long-tubes purely on a basis of static flow. BUT, properly sized longtubes are worth 20-30 HP, or more, on our cars. Most of that gain is becasue they are properly tuned.
Like our earlier example, if you were to bolt on a "bad" set of Longtube headers--ones with too small or loo large primaries, the backpressure would still be lessened compared to stock, but the tuning would be all kinds of wrong. This is one of those things that people are going to call "too little backpressure", but again, backpressure isn't the issue.
All this being said, I don't belive for a minute that the SLP mufflers will cost you HP, so long as the engine is properly tuned (correct A/R ratio).
Let me see if I can explain this:
There are two basic factors in an exhaust system that are often confused with each other:
1) "Backpressure", which is better called "static impediment to flow". This includes things such as baffled mufflers, narrowed-down sections in the exhaust tubing, crimped joints, very tight bends, or turbulence-enducing "defects" like rough castings/tubing, poor quality welds that stick out into the exhaust flow area, badly matched tubing joints, and so forth. Factors like this --backpressure-- always cost you horsepower, period.
2) The second factor, and the most mis-understood, is the tuning (resonance and other) of the exhaust system to suit the engine. This is based on complex physics, but it has to do with the diameter and the length of the exhaust pipes, especially those closest to the engine. (For example, header primaries). This can sometimes cost you power and sometimes make you power.
If your engine is properly tuned (as earlier posters discussed re-jetting carbs), then lowering backpressure (#1 above) will ALWAYS be beneficial to your engine. It might give you a lot of HP, it might give you a little, but it will never hurt you. I'll say that again so it's clear. If your engine is properly tuned, reducing backpressure will NEVER hurt performance.
The second factor, tuning/resonance, is complex. Let's do an example. Suppose that I have a relatively small displacement V8, such as our 4.6L. Suppose then that I buy a set of long-tube headers with HUGE primary tubes, like pro drag race headers that were meant for a 500+ cubic inch big-block making 2,000 HP or more. Pretend for a moment that these headers would bolt up to my 4.6. What happens?
Well, on the one hand, I've reduced the restiction in the exhaust because the smooth bends of the headers are much less restrictive than the OEM manifolds.
On the other hand, I've completely changed the tuning of the exhaust. Those giant-diameter headers are going to be ill suited for my 4.6 "street engine" becasue the resonant characteristics are a very poor match. This will probably cost me HP.
So what's the conclusion? More than likely, I will LOOSE a lot of power through most of the RPM range. Someone that didn't know any better might say You lost HP becasue those big headers had too little back-pressure. That is WRONG. The backpressure (restriction) isn't the problem. The problem is that the big block drag headers aren't a good tuning match for the engine.
Tuning is complicated, but it works a bit like this:
First off, the diameter of a tube affects the velocity of the gases that flow through it. An engine running at a certain RPM is going to be emitting a certain volume of exhaust gas. A "smaller" tube makes the gases flow faster (and if it's small enough, becomes a restriction). A "larger" tube slows down the gases. There is a delicate trade-off here. High speed flow is good for scavenging in a naturally-aspirated motor. BUT, too narrow of a tube, causes backpressure at high RPM (as above). That's why a set of headers needs to be matched to the engine. It needs to have tubes that are sized correctly to give good velocity and scavenging, but not too small, as to hurt high RPM power.
In our earlier example, the big-block headers don't work on a small V8 becasue the tubes are so big (for the exhaust flow of the small engine) that the velocity drops and scavenging suffers. It's not the "backpressure" that causes a problem here, it's the improper tuning!
A second kind of tuning has to do with matching the lengths of the piping (usually header primaries) with the characteristics of the engine. Any pipe will resonate at a given frequnecy. (That's how wind instruments, like a trumpet, work folks) The frequnecy has to do with the length of the tube and its diameter. People that design headers come up with specific lengths and diameter combinations that make them work with certain engines. On professional race cars, this goes even further, into the X/H-pipes, and even the full length of the tail-pipe, and shape of the muffler(s).
So, it's possible to have an exhaust mod that reduces backpressure (always good) but AT THE SAME TIME screws up "tuning" in one way or another. If the tuning screwup is worse than the backpressure reduction, then people might say "that mod has too little backpressure". Bull$hit. The backpressure is fine, it's the tuning that's messed up.
You can see this in many common aftermarket mods.
For example, Shorty Headers. Shorty headers drop backpressure becasue they are freer flowing compared to the cast stock manifolds. But, Shorty Headers aren't really "tuned" at all. Consequently, they give you a small HP gain: 3-5 HP tops.
Long Tube headers, on the other hand, drop backpressure AND they are properly tuned. In fact, I'll bet that on a flow bench you couldn't even tell the difference between shorty headers and long-tubes purely on a basis of static flow. BUT, properly sized longtubes are worth 20-30 HP, or more, on our cars. Most of that gain is becasue they are properly tuned.
Like our earlier example, if you were to bolt on a "bad" set of Longtube headers--ones with too small or loo large primaries, the backpressure would still be lessened compared to stock, but the tuning would be all kinds of wrong. This is one of those things that people are going to call "too little backpressure", but again, backpressure isn't the issue.
All this being said, I don't belive for a minute that the SLP mufflers will cost you HP, so long as the engine is properly tuned (correct A/R ratio).