removing mufflers
Thread Starter
Joined: Oct 2006
Posts: 14
removing mufflers
Is removing the mufflers and putting in strait pipes on a stock system that bad of an idea? I figured it would make you lose backpressure causing you to lose some low end torque, and it may be too loud, but with the stock cats and such i donno how bad it would be. whats your thought?[/align]
Senior Member
Joined: Jul 2005
Posts: 2,105
From: Central North Carolina
RE: removing mufflers
Yeah, its a pretty bad idea: it results in a great increase in noise, and no gain in power -- maybe even a loss.
Sound: It increases the level of sound you hear, all the time, a lot.that is fun only briefly and then itgets old in a hurry. Also, the "sound quality" is poor: most folks like a very low bass sound, and the V8 "intermingled exhaust pulsation rumble," but straight pipes let through all the rest, the high-pitch parts of the sound, etc.Aftermarket cat-backs give you the preferred low-end rumble but still filter out the annoyinghigh pitched elements andparts of the sound.
Power: There is little of no power gain on a stock engine over what you get by installing a good cat back system, and actually a loss compred to the best ones. The LS engines, at least in stock form, seem to need a little backpressure to function well in the mid and high RPM ranges. Frankly, most of what they need they get from the catalytic converters, and any backpressure fruther downstream isonly of secondary importance. I suspect, but have never looked into it, that this need for backpressure is designed in at the factory, is due to emissions reasons: designers want the exhaust to slow down a bit before hitting the cats so it spends a bit more time passing through them and getting cleaned).
(By the way, removing the cats, on a stock engine, usually results in no power gain).
On heavily modified engines(anything with a stroker crank or modified heads and cam) removing cats and or mufflers almost always will produce a power gain: as an example on my vette the cats are worth 30 HP and the mufflers about 10 (but I still run both, it's a street car, but at the track I can get 745 RWHP by oipening the exhaust at the collector tubes).This is because: a)modded cars have so much more exhaust to get rid of (exhaust volume is roughly proportional toHP--double the power, double what you have to push through the mufflers), and b) because aftermarket cams often set the engine up so it does not need or want any exhaust backpressure - here you just don't know 'til you try it. This is also complicated by the fact that high-duration cams work much better with long tube headers so usually you have those in the equation: now you car really does want a straight exhaust on it.
Sound: It increases the level of sound you hear, all the time, a lot.that is fun only briefly and then itgets old in a hurry. Also, the "sound quality" is poor: most folks like a very low bass sound, and the V8 "intermingled exhaust pulsation rumble," but straight pipes let through all the rest, the high-pitch parts of the sound, etc.Aftermarket cat-backs give you the preferred low-end rumble but still filter out the annoyinghigh pitched elements andparts of the sound.
Power: There is little of no power gain on a stock engine over what you get by installing a good cat back system, and actually a loss compred to the best ones. The LS engines, at least in stock form, seem to need a little backpressure to function well in the mid and high RPM ranges. Frankly, most of what they need they get from the catalytic converters, and any backpressure fruther downstream isonly of secondary importance. I suspect, but have never looked into it, that this need for backpressure is designed in at the factory, is due to emissions reasons: designers want the exhaust to slow down a bit before hitting the cats so it spends a bit more time passing through them and getting cleaned).
(By the way, removing the cats, on a stock engine, usually results in no power gain).
On heavily modified engines(anything with a stroker crank or modified heads and cam) removing cats and or mufflers almost always will produce a power gain: as an example on my vette the cats are worth 30 HP and the mufflers about 10 (but I still run both, it's a street car, but at the track I can get 745 RWHP by oipening the exhaust at the collector tubes).This is because: a)modded cars have so much more exhaust to get rid of (exhaust volume is roughly proportional toHP--double the power, double what you have to push through the mufflers), and b) because aftermarket cams often set the engine up so it does not need or want any exhaust backpressure - here you just don't know 'til you try it. This is also complicated by the fact that high-duration cams work much better with long tube headers so usually you have those in the equation: now you car really does want a straight exhaust on it.
Joined: Oct 2006
Posts: 216
From: South Carolina
RE: removing mufflers
Alright Lee, then can you answer this one for me......I have an '02 Z06 w/o cats and I'm about to put stock Ti exhaust back on it, but I have an idea. Buy some Titanium tubing, smaller than the other exhaust piping, and weld it into place between the inlet and outlet of the exhaust, therefore PARTIALLY bypassing the muffler. Now, would this big time ruin my backpressure or what? Sometime in the future I am going to first of all put a cam in, then later once I get some more money put some heads on it. What is your opinion on this? (Please don't hate on the lack of cats too much. I live in SC and we don't have emmision tests yet so I'm taking advantage of it as much as I can for now)
Senior Member
Joined: Jul 2005
Posts: 2,105
From: Central North Carolina
RE: removing mufflers
First, what you mention has been done a few other times and results in a nice sound sometimes (and sometimes not) Borla makes one system that has this already installed and comes with a set of variable size by-pass plates to vary how much goes through the alternate route from none to all.
But titanium is difficult to work and nearly impossible to weld without equipment only the military and big manufacturers can afford. You can use regular muffler clamps, though, but your plan will be still difficult since the whole exhaust is titanium and you will have to cut and fit into the titanium. I would not try it myself.
Instead, consider installing QTP electric cutouts. http://www.quicktimeperformance.com/QTEC/index.php
Then you can run quiet in full-muffler mode when you need to (cop car alongside) and go to full-loud when you want (ricer alongside) or anywhere in between, all at the touch of a button! This will cost less than doing what you want given you have a titanium exhaust (but more than that would cost if you had a regular steel exhaust).
Second, removing the cats reduces backpressure/changes exhaust charactreristics more than anything you can do further back, so whatever change, good or bad, occurred to the exhaust backpressure and its effect on the engine is already done.
T
But titanium is difficult to work and nearly impossible to weld without equipment only the military and big manufacturers can afford. You can use regular muffler clamps, though, but your plan will be still difficult since the whole exhaust is titanium and you will have to cut and fit into the titanium. I would not try it myself.
Instead, consider installing QTP electric cutouts. http://www.quicktimeperformance.com/QTEC/index.php
Then you can run quiet in full-muffler mode when you need to (cop car alongside) and go to full-loud when you want (ricer alongside) or anywhere in between, all at the touch of a button! This will cost less than doing what you want given you have a titanium exhaust (but more than that would cost if you had a regular steel exhaust).
Second, removing the cats reduces backpressure/changes exhaust charactreristics more than anything you can do further back, so whatever change, good or bad, occurred to the exhaust backpressure and its effect on the engine is already done.
T
Senior Member
Joined: Jul 2005
Posts: 2,105
From: Central North Carolina
RE: removing mufflers
If you can put the cats back on, I will "undo" any loss of power or emissions that removing them caused. If it was my car, I would put long tube headers and larger aftermarket cats on it (the combination work very well). Then have it tuned to maximize the added power.
Joined: Jul 2006
Posts: 6
RE: removing mufflers
love my Borlas, but looking for quiet at 70-80mph...is there a quick/temporary/removable system for this? Bassetts will accept a baffle system for some reduction...thanks
ORIGINAL: Lee WillisYeah, its a pretty bad idea: it results in a great increase in noise, and no gain in power -- maybe even a loss. Sound: It increases the level of sound you hear, all the time, a lot. that is fun only briefly and then it gets old in a hurry. Also, the "sound quality" is poor: most folks like a very low bass sound, and the V8 "intermingled exhaust pulsation rumble," but straight pipes let through all the rest, the high-pitch parts of the sound, etc. Aftermarket cat-backs give you the preferred low-end rumble but still filter out the annoying high pitched elements and parts of the sound. Power: There is little of no power gain on a stock engine over what you get by installing a good cat back system, and actually a loss compred to the best ones. The LS engines, at least in stock form, seem to need a little backpressure to function well in the mid and high RPM ranges. Frankly, most of what they need they get from the catalytic converters, and any backpressure fruther downstream is only of secondary importance. I suspect, but have never looked into it, that this need for backpressure is designed in at the factory, is due to emissions reasons: designers want the exhaust to slow down a bit before hitting the cats so it spends a bit more time passing through them and getting cleaned).(By the way, removing the cats, on a stock engine, usually results in no power gain).On heavily modified engines (anything with a stroker crank or modified heads and cam) removing cats and or mufflers almost always will produce a power gain: as an example on my vette the cats are worth 30 HP and the mufflers about 10 (but I still run both, it's a street car, but at the track I can get 745 RWHP by oipening the exhaust at the collector tubes). This is because: a) modded cars have so much more exhaust to get rid of (exhaust volume is roughly proportional to HP--double the power, double what you have to push through the mufflers), and b) because aftermarket cams often set the engine up so it does not need or want any exhaust backpressure - here you just don't know 'til you try it. This is also complicated by the fact that high-duration cams work much better with long tube headers so usually you have those in the equation: now you car really does want a straight exhaust on it.
Joined: Feb 2008
Posts: 2
RE: removing mufflers
Hi, thought i might step in and correct something. Quoted directly from super chevy march 08 " An engine does not need backpressure, what it does need is scavenging which is directly related to exhaust velocity. A common misconception is that you'll lose some low end torque by stepping up to a larger after-cat system. What's really happening is that the larger diameter piping is moving the rpm range where the scavenging takes place higher up the powerband. Since exhaust velocity increases with rpm, you're not losing power but moving it higher up in the rpm band" and by the way i hope im not coming off the wrong way on my first post, but just thought i should correct you no offense. Im looking to buy a C5 in the very near future just trying to find the perfect one. thanks and i love the site have already learned a lot about the C5.
Joined: Jan 2007
Posts: 236
From:
RE: removing mufflers
ORIGINAL: enos44
Hi, thought i might step in and correct something. Quoted directly from super chevy march 08 " An engine does not need backpressure, what it does need is scavenging which is directly related to exhaust velocity. A common misconception is that you'll lose some low end torque by stepping up to a larger after-cat system. What's really happening is that the larger diameter piping is moving the rpm range where the scavenging takes place higher up the powerband. Since exhaust velocity increases with rpm, you're not losing power but moving it higher up in the rpm band" and by the way i hope im not coming off the wrong way on my first post, but just thought i should correct you no offense. Im looking to buy a C5 in the very near future just trying to find the perfect one. thanks and i love the site have already learned a lot about the C5.
Hi, thought i might step in and correct something. Quoted directly from super chevy march 08 " An engine does not need backpressure, what it does need is scavenging which is directly related to exhaust velocity. A common misconception is that you'll lose some low end torque by stepping up to a larger after-cat system. What's really happening is that the larger diameter piping is moving the rpm range where the scavenging takes place higher up the powerband. Since exhaust velocity increases with rpm, you're not losing power but moving it higher up in the rpm band" and by the way i hope im not coming off the wrong way on my first post, but just thought i should correct you no offense. Im looking to buy a C5 in the very near future just trying to find the perfect one. thanks and i love the site have already learned a lot about the C5.
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