Muffler Question

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I am planning to get either a Magaflow or Gibson muffler to replace my OEM on my Mitsubishi Montero Sport 3.0 V6. I am keeping the stock piping of 2" from the cat back and probably will only change on the inlet and outlet of the muffler since the smallest diameter each muffler has available is 2.25". How does the muffler size i.e dimensions affect the torque curve of the engine?
 
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It depends on the length and brand of the muffler bearings that you are using. The ones that come with the grease fittings built in will last longer than the newer styles.
 
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Increasing diameter will tune the exhaust for higher RPMs. I don't think going up 1/4" on the muffler only would make a noticeable difference there though; maybe a couple lb-ft at a little higher RPM. A muffler of the same diameter that simply flows more freely will increase torque across the RPM range though; once again, maybe a couple lb-ft. Either way, probably not a noticeable difference in performance unless it's a straight-through muffler. You might barely notice the effect of a straight-through muffler, but nobody around you would appreciate that!
 
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Good one Bernard. #1 - wrong forum for a muffler question #2 - you will gain 0 horsepower and 0 torque changing the muffler. you will only gain sound. Sadly the sound will drive you crazy if you take long trips. #3 - why are you doing this? is your current muffler rusted out?
 

2000_SL_1.9

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Thanks, Bernard, I am not clear on your answer. Perhaps my first post was unclear. The mufflers I'm considering use 2.25" OD piping. So, the muffler shop will have to weld a transition fitment from 2" to 2.25" for the muffler fit. Since my V6 is not a high output engine in regards to hp and tq, I don't want to go with a higher diameter piping. The only modifications I have made is a K&N drop in and plugging the airbox/snorkel resonators, hoping that closing those up will increase intake air velocity or at least increase the intake pressure. I'm not an engineer and this may be junkyard science. So maybe you enlightened ones on the board can help me out. I basically want to increase my throttle response and add a little pick up. I know these mods aren't going to yield 50hp. I like tinkering with stuff. I would be happy with just 5-10 hp gains. I'm sorry if this is posted in the wrong forum. I saw Auto... and General Topics and clicked the link. [Duh!] Moderators please feel free to move this to the proper forum. [ September 02, 2006, 04:37 AM: Message edited by: 2000_SL_1.9 ]
 
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Bernard was joking. To increase horsepower you must reduce the resistance of the exhaust pipe, and the best way to do that is to increase pipe diameter. You will not gain any noticeable power changing just a muffler, but you will gain a lot of sound and often sound is confused with power. I don't advise changing the muffler for more "throttle response". [Smile]
 

2000_SL_1.9

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So are all these aftermarket bolt on stuff such as intake tubes and baffled, chambered, perforated straight pipes in the muffler housing just hype unless you actually do some ECU reprogramming and head porting etc.?
 
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A cat-back system designed for your car may work nicely if the stock piping is indeed too small or if the stock piping has poor bends (you'll see ripples along the curve crossways to the flow). If the stock muffler is the most restrictive part, then dropping in a freer flowing muffler will help. Maybe you won't feel the difference in the seat of the pants or in fuel mileage, but maybe it would relieve a little backpressure and make the enging run a tad cooler in the exhaust manifold area. Certainly won't hurt. I was told by one muffler "expert" that with my '95 F150 simply installing a freer flowing muffler in the stock piping would give me about 90% of the benefits of a cat-back system. He said the muffler on mine is very restrictive. So what'd I do? Bored holes in the back of the muffler, wrapped it with sheet metal for crisp sound, and have enjoyed the "truck" (not hot rod) sound for the past several years. It is ripening with age--a good effect for me. I was just too cheap to spend the time and money on a new muffler when the stock muffler was in good shape. As far as exhaust tuning, you probably have no effect after the catalytic converter. A larger diameter muffler won't make any difference in the torque curve as I understand it.
 
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A straight through type muffler will have less restriction than a chambered type. You will get better power and gas mileage. No miracles, but it WILL breathe freer. At the end of the pipe, you are not really tuning, but removing a cork. Yes, it will be louder, but usually only a problem when accelerating hard, if that.
 
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''plugging the airbox/snorkel resonators, hoping that closing those up will increase intake air velocity or at least increase the intake pressure. I'm not an engineer '' Did it ever occur to you that the people that convinced the bean counters they were worth the cost were engineers? You could well be better off unplugging them and leaving the exhaust alone.
 

2000_SL_1.9

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quote:
Originally posted by labman: ''plugging the airbox/snorkel resonators, hoping that closing those up will increase intake air velocity or at least increase the intake pressure. I'm not an engineer '' Did it ever occur to you that the people that convinced the bean counters they were worth the cost were engineers? You could well be better off unplugging them and leaving the exhaust alone.
I understand your point. What if the engineering that went into designing the airbox was primarily to reduce noise and secondary to make the engine breathe efficiently?
 
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the catalytic converter(s)which are located upstream of your muffler are a major source of exhaust restriction. A free flow muffler alone won't do diddly for power-certainly not the 10hp you are hoping for. Spend the money on a "Tornado" intake restricter instead. (that was a joke, son)
 
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Biomed_eng, you are wise. The placebo effect plays a huge role in the marketing of aftermarket performance parts. Or maybe I should say "alleged performance" parts. The increased sound from a less-restrictive muffler (or intake, air filter, synthetic blinker fluid or whatever)will absolutely convince most buyers that their engine is making more power. I've been there. It's because they've (we've) spent the money and want to believe it. I haven't used (or seen) a G-Pro, but have seen positive references to them, and the concept makes a lot of sense. My point is that increased performance can be well documented with stopwatches, G-techs and the like, but definitely not by the seat of anyone's pants. (top pro drivers excluded. maybe. somewhat. or not.) And don't even get me started on "strut bars" for street cars. Now THAT'd be a rant...
 
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Here is a simple test to find out what you might be missing without a free flowing exhaust - temporarily disconnect your exhaust just after the cat. Yes it will be loud but this is as good as it's going to get. At this point you have to ask yourself two questions. Am I really missing anything? How much noise can I really stand on a daily basis?
 
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If you want to know if you made any more power/tq, I recommend you buy a gtechpro RR, just google it. I have used them for tuning and they work great. The RR allows you to see the data on your PC for analysis. It graphs the TQ/HP vs RPM curves for you too.
 
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quote:
''plugging the airbox/snorkel resonators, hoping that closing those up will increase intake air velocity or at least increase the intake pressure. I'm not an engineer ''
I would not plug the snorkel resonator or whatever it is. I removed it from the 3.0 V6 in the Aerostar. No negative effect, slightly louder intake, larger air opening, runs fine. There are free flowing mufflers that are not excessively noisy, but you might as well get a free flowing cat too. If you go cat-back system you will be sure of the best reduction of bottlenecks, that is unless the exhaust manifolds are bottlenecked too. But who knows if it will make a significant difference.
 
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TurboJim said "At this point you have to ask yourself two questions. Am I really missing anything? How much noise can I really stand on a daily basis?" You really should ask yourself how much noise the REST OF THE WORLD should have to endure on a daily basis with your new exhaust system .. P.B.
 
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While I personally cannot tolerate automotive exhaust noise (excessive), I beg to differ RE: less restrictive exhaust flow = HP. Reasoning as follows: Have you ever look at Honda S2000's design, even with factory stock cat and muffler, this car is known to produce 100hp/1litre in N/A configuration (stock exhaust and intake). Have you tried installing aftermarket exhaust to see how see what sort of gain you got? I have (not on my car but someone in my pool of "autophools" did it and then dyno'ed it) and the hp dropped considerably (HKS manifold, cat bypass, low restriction HKS muffler, etc.). And you wonder why there are so many "loud" systems out there that would accelerate slower than your ordinary "cat-in", "restrictive" exhaust system? Note: think "exhaust scavenging" within a particular N/A gasoline engine.
 
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"And don't even get me started on "strut bars" for street cars. Now THAT'd be a rant..." I worked on my car. The car no longer flexs over some bridge expansion gaps on highway. And the creaking was also reduced when I go up my drive way. Belive it or not, beside the strut bar, the rood rack also helped to firm up my car.
 
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Opening up the air intake system to make it less restrictive and increase airflow to the engine, and decreasing restrictions in the exhaust system by using larger pipes, mandrel bends in the pipes, and less restrictive mufflers, when done together, will generally increase hp and torque. By how much depends on the engine. Increases can vary from a mere 1-2 hp and 1-2 ft. lbs. of torque to 10+ hp and 10+ ft. lbs. of torque. The dyno results I've seen generally show that the larger increases are on the larger V8's and larger diesels. Noise will result from both the intake and the exhaust modifications, and it may be a considerable noise increase. The intake and exhaust sysems are factory engineered to low noise levels, because low noise is what most consumers want, which results in restrictive systems that, when modified to increase air inflow to and outflow from the engine, will increase hp and torque. Do NOT believe any self-serving hp and torque increase claims made by the manufacturers of exhaust systems and their components, hi-flow air cleaners such as K&N, and cold air intake kits.
 
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