jayybird69 Posted March 5, 2012 Share Posted March 5, 2012 Hello everyone, Looking into upgrading my exhaust, have purchased header (ebay), magnaflow cats, looking for cat back pipe (larger than stock) What have you used or where can i find? trying to bolt on. 98L 2.2 thanks Link to comment Share on other sites More sharing options...
ricky santana Posted March 7, 2012 Share Posted March 7, 2012 www.letmesearchthatforyou.com Link to comment Share on other sites More sharing options...
JJay03 Posted March 7, 2012 Share Posted March 7, 2012 I ordered the magaflow cats and thinking about a ebay header also. Im just going to go with a stock replacement midpipe going larger would have no benefit. Link to comment Share on other sites More sharing options...
Kennyfvholla Posted March 7, 2012 Share Posted March 7, 2012 You won't find a gains in performance by using a larger mid-pipe. You'd be better off installing a race style/straight through design performance muffler.. Link to comment Share on other sites More sharing options...
Diagtech Posted March 7, 2012 Share Posted March 7, 2012 98 2.2L has single exhaust ports, sure you have the right header? Link to comment Share on other sites More sharing options...
jayybird69 Posted March 7, 2012 Author Share Posted March 7, 2012 1 new to forum not new to life. Seems to be a trend on here 2. Blow through a straw 5 inches long, then blow through a Straw 10 inches long and tell me there is no difference in resistance. Link to comment Share on other sites More sharing options...
Kennyfvholla Posted March 8, 2012 Share Posted March 8, 2012 lol, well. I suggest you go take a physics class. I also suggest you take your sass and sarcasm somewhere else. You didn't get 6 or 7 people ripping you a new one and putting you down. You got a handful of people giving you decent responses in order to try and help you out. And now, I refer you to something I posted on here a while back. We're talking about a sub 200 horsepower 2.2 liter 4 cylinder engine. So any changes in the exhaust system, besides running a header, straight pipes, and muffler, will yield absolute minimal performance gains or losses. Oh and we were referring to the DIAMETER of the mid-pipe and not the length, smart one.. The goal of the headers is to use differences in atmospheric pressure to create a vacuum, which helps draw the exhaust gases out of the cylinder quickly and smoothly. The goal of the rest of the exhaust system is to continue this vacuum all the way to the tail pipe. Gases move from one place to another because of the differences in pressure and the tendency to reach equilibrium. Bends have almost nothing to do with efficiency, it's the length and diameter of a header tube as well as the locations of where exhaust tubes and exhaust gases meet, which should be sized and located according to the size of the cylinders and rev capability. Primary header tubes meeting immediately (such as stock exhaust manifolds) = immediate back pressure into the cylinders and no efficiency or exhaust scavenging. The engine itself has to create the pressure during a power stroke to "push" the exhaust gases out of the cylinder. This takes power on the engines part and reduces overall horsepower at the crank. Primary header tubes meeting 2 to even 3 feet in length from the exhaust ports (such as long tube headers) = no immediate back pressure and more volume with less pressure than the cylinders. This creates more "room" for the exhaust to to immediately come to an equilibrium within the cylinder and header tubes. Now as this happens, the piston in cylinder is moving up, and while doing so is increasing pressure in the cylinder. But the long length of the header has left enough volume for that pressure to fill up the tube without creating much back pressure. Larger diameter = slower moving exhaust gases; and smaller diameter = faster moving exhaust gases. For optimum efficiency, you want the pipes to be long enough to handle all of the exhaust gases from the cylinder, but you don't want the diameter to be too large or too small. The optimum diameter is contingent to the length of the headers. Now, the proper length of tubing coming from each cylinder should be a little different. This is because you don't want exhaust gases from each cylinder colliding, and negative pressure occurs in the exhaust manifolds between the positive pressure pulses, especially at lower engine speeds. This is where the math really comes into play. You need to tune the lengths so the exhaust pulses enter the collector between the exhaust pulses from other cylinders, preventing interference between the exhaust pulses. A Subaru N/A UEL header in design, has separate tubing of equal lengths coming from each cylinder and ending in a primary collector for each side of the engine. On the drivers side a very short secondary header pipe then connects to a secondary collector at the end of the headers, while the secondary header tubing coming from the drivers side is much longer before it reaches the secondary collector. The length of the secondary tubing is purposely different so that exhaust gases run into each other at certain points to bring out a rumble inherent to the design of a boxer engine. An N/A equal length header, such as the one one from OBX, has much longer primary tubing than the UEL header (all having specifically tuned lengths to reduce exhaust pulse collisions) that meet at a primary collector, which finally enters into a single short, secondary tube with no collector. Remember, every bit of an exhaust system is going to have less of a power impact behind a UEL header than an EL header. To design the rest of the exhaust system, you now have to realize that you want there to be negative pressure compared to the positive pressure within the headers. So now you want to create yet more exhaust scavenging. This is where keeping enough back-pressure, in stages, is important because you want to keep the exhaust flowing as smoothly and as quickly as possible. By creating stages of back pressure you are creating different area's of pressure within the exhaust system, and remember differences in pressure are how gases move from one area to the next. A 2.2 or 2.5 liter engine is too small to create enough exhaust pressure for a full length true dual exhaust system, so a single pipe exhaust system in necessary. But that's a give in... More importantly, this is when you need to figure out where to place any exhaust component that will increase positive (back) pressure. Starting, you need with the 1st or only catalytic converter. After that you need to find out where to locate the resonator, and how long it should be. And last, you need to decide which muffler you want to use. Remember, converters, resonators, and muffler all create a large space for exhaust gases to slow down, which increases back pressure. You need to consider how much extra volume a particular exhaust component creates. Besides figuring out where an exhaust component should be placed, you need figure out if you should use none, one, or two converters, whether or not you should use a resonator, and what type of muffler you want/need. Considering emissions regulations, if you don't care about sound, I would use one converter (somewhere around the stock location of the secondary converter), no resonator, and a short high flow racing muffler, all with 2.25 inch tubing to make up for the lack of pressure from pressure points. Also considering emissions regulations, but wanting to keep sound decibels and resonation to a minimum, I would use two high flow converters (located as far away from each other as possible), an long length resonator (located at little bit further back from the stock location), and a full size, high flow, performance muffler, all with 2.5" tubing to make up the differences in pressure caused by the extra exhaust components. It's a lot to think of. And now you see why I really don't care to do the math. It's NOT worth the trouble on a stock N/A non-performance orientated 4 cylinder, as it all makes such a small percentage in power difference. If you're running UEL headers, it's only a little bit more important to figure out how to set up the rest of the exhaust system in order to increase exhaust scavenging from the headers in order to gain as much power as possible compared to using an EL header. You might see a 4 to 6 horsepower difference on a 2.5 in max horsepower, but you certainly won't lose any. Link to comment Share on other sites More sharing options...
monkeyposeur Posted March 8, 2012 Share Posted March 8, 2012 Blow through a straw 5 inches long, then blow through a Straw 10 inches long and tell me there is no difference in resistance. Diameter is more important than length in this case. Read up on your physics. Link to comment Share on other sites More sharing options...
jayybird69 Posted March 8, 2012 Author Share Posted March 8, 2012 alright genius, i didn't think i had to spell it out but if you have a straw 5 inches long and 1 cm diameter coupled to another 5 inch straw 3 cm in diameter, you will have less resistance than a single 10 inch straw 1cm diameter. not physics common sense. there does not have to be expected hp gain. Link to comment Share on other sites More sharing options...
monkeyposeur Posted March 8, 2012 Share Posted March 8, 2012 Well in your earlier post you only mentioned length not diameter. Kind of a big deal. Link to comment Share on other sites More sharing options...
jayybird69 Posted March 8, 2012 Author Share Posted March 8, 2012 my post was not meant for all posters and i apologize, but the diameter past the 5 inch straw would have been irrelevent, it was obvious i was talking about a larger diameter hence my starting post. Exactly what i was reffering to. "seems to be a trend here" Link to comment Share on other sites More sharing options...
monkeyposeur Posted March 8, 2012 Share Posted March 8, 2012 Oh, well in that case I apologize for missing the obvious. Link to comment Share on other sites More sharing options...
subikid90 Posted March 8, 2012 Share Posted March 8, 2012 There are dyno test somewhere (rs25.com i think) with data proving that anything over 2.25" is to large for an NA 2.5. Going bigger is not better on an NA motor, you will lose back pressure and lose power. -Subikid90 1997 Legacy GT 5spd & EJ251 w/EJ25D heads ~10.5CR 1998 Legacy GT Limited waiting for EJ22T hybrid swap Link to comment Share on other sites More sharing options...
JJay03 Posted March 8, 2012 Share Posted March 8, 2012 There are dyno test somewhere (rs25.com i think) with data proving that anything over 2.25" is to large for an NA 2.5. Going bigger is not better on an NA motor, you will lose back pressure and lose power. Exactly and the choking point is still going to be the stock cats and manifold. Link to comment Share on other sites More sharing options...
jayybird69 Posted March 8, 2012 Author Share Posted March 8, 2012 the only loss in power would be caused by the computers inability to compensate for leaner air/fuel due to decreased backpressure? so increasing midpipe size will have no pos or neg affect, if the "choking point" is the header and cats. but it will give a deeper throaty sound through a performance muffler? Link to comment Share on other sites More sharing options...
jayybird69 Posted March 8, 2012 Author Share Posted March 8, 2012 and more secifically power loss caused by decreased back pressure would relate to FI, vehicles, not carburated NA's? Link to comment Share on other sites More sharing options...
Kennyfvholla Posted March 8, 2012 Share Posted March 8, 2012 Look, if you are so smart and know so much about this and going to argue against everything and anything everyone says just go do what you want. You're obviously going to do it anyway.. Oh, and to answer your original question about where to buy a mid-pipe, you can't. You have to have one custom fabricated. Link to comment Share on other sites More sharing options...
subikid90 Posted March 8, 2012 Share Posted March 8, 2012 FI does not want back pressure, thats why turbo diesels and turbo cars like STi's run large pipe. Why waste the money on a midpipe if you are keeping the stock cats? -Subikid90 1997 Legacy GT 5spd & EJ251 w/EJ25D heads ~10.5CR 1998 Legacy GT Limited waiting for EJ22T hybrid swap Link to comment Share on other sites More sharing options...
Kennyfvholla Posted March 8, 2012 Share Posted March 8, 2012 It doesn't matter if you are running an electronic fuel injection system or a carburetor, being an NA car you want as much exhaust scavenging as possible. To do that, you need to increase velocity. And regardless of the reasons, a larger mid-pipe WILL decrease exhaust gas velocity and back-pressure will be increased. It is THAT simple. Link to comment Share on other sites More sharing options...
jayybird69 Posted March 9, 2012 Author Share Posted March 9, 2012 OK whoa, if you notice my question marks you will Find that I'm looking for confirmation? Now your talking circles around yourself, one minute a larger pipe increases BP next It decreases it. Your a ******* retard, go **** yourself. Link to comment Share on other sites More sharing options...
monkeyposeur Posted March 9, 2012 Share Posted March 9, 2012 Jayybird, you are a dick. Link to comment Share on other sites More sharing options...
subikid90 Posted March 9, 2012 Share Posted March 9, 2012 And reported... -Subikid90 1997 Legacy GT 5spd & EJ251 w/EJ25D heads ~10.5CR 1998 Legacy GT Limited waiting for EJ22T hybrid swap Link to comment Share on other sites More sharing options...
Kennyfvholla Posted March 9, 2012 Share Posted March 9, 2012 OK whoa, if you notice my question marks you will Find that I'm looking for confirmation? Now your talking circles around yourself, one minute a larger pipe increases BP next It decreases it. Your a ******* retard, go **** yourself. Your next to last post had question marks. I was not see that post, and was responding to to other posts you made before then with no question marks. I'm not the one talking circles around myself. You couldn't even get what you were saying straight, and then started to ask questions. I also never said a larger mid pipe increases back-pressure. I have tried to help you with every single one of my posts, and you have been rude with your responses so I was rude with irritation in return. I will gladly unsubscribe from this thread and be done with you. Thank you for all your kind words, and have fun with your Subaru.. Link to comment Share on other sites More sharing options...
jayybird69 Posted March 9, 2012 Author Share Posted March 9, 2012 It doesn't matter if you are running an electronic fuel injection system or a carburetor, being an NA car you want as much exhaust scavenging as possible. To do that, you need to increase velocity. And regardless of the reasons, a larger mid-pipe WILL decrease exhaust gas velocity and back-pressure will be increased. It is THAT simple. Link to comment Share on other sites More sharing options...
SBT Posted March 9, 2012 Share Posted March 9, 2012 FI does not want back pressure, thats why turbo diesels and turbo cars like STi's run large pipe. Why waste the money on a midpipe if you are keeping the stock cats? I believe you were referring to Forced-Induction (rather than fuel-injected) cars which run larger DP and CBEs, in order to move the massive amount of air that the engine is pushing as a result of the turbo compressor pushing more air into the intake side. Even the stock cats on these cars are designed to move as much air as possible (be less restrictive). It doesn't matter if you are running an electronic fuel injection system or a carburetor, being an NA car you want as much exhaust scavenging as possible. To do that, you need to increase velocity. And regardless of the reasons, a larger mid-pipe WILL decrease exhaust gas velocity and back-pressure will be increased. It is THAT simple. Exactly! - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
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