 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Ford / Ford Mustang / October 2004Exhaust 3" or 2 1/2"?
I have an 87 gt with a strong 331 supercharged motor running 15 lbs. boost . I am in the process of stepping my headers up from 1 5/8 x 2 1/2" to 1 3/4 x 3". Should I run the exhaust 3" all the way with a 3" X-pipe and 3" in and out mufflers or should I reduce to 2 1/2" for some back pressure? Any input would be appreciated , also any input on muffler reccomendations. Thanks LarryV >I have an 87 gt with a strong 331 supercharged motor running 15 lbs. boost >. I [quoted text clipped - 6 lines] > be appreciated , also any input on muffler reccomendations. Thanks > LarryV IMHO, I'd run 2.5". Here's why. The resistance and flow characteristics in the pipe itself changes dramatically for each size you move up. Using basic math you can see the difference. 3" pipe= 85.2 square inches volume in 1' of pipe 2.5" pipe= 58.8 square inches volume in 1' of pipe. Difference of 26.4 square inches. 2.25" pipe= 46.8 square inches volume in 1' of pipe. Difference of 12" and 38.4" from 3" pipe You can see how this adds quite rapidly even though it's only a fraction of an inch change in diameter. Over the full length of an exhaust system which is...oh say...16', the 3" system ends up with a capacity almost twice that of the 2.25" system and 50% more than the 2.5" system. This may sound good, but it's a huge difference for what the engine sees in resistance. If the motor weren't blown I'd say 2.25" would be all you'd need, especially if you want to keep some reserve torque. If you had a more cubes, or a BB, then I'd say the 3" would work. I'm running 2.5" on my 400ci Windsor and it's plenty. The other thing you might think about is the sound you'll get from the different size pipes. Acoustically there is a difference. As a brass musician and someone who has studied acoustics, I will use some simple comparisons. The French Horn and the Baritone are roughly the same length, however the Baritone has roughly twice the bore (inside diameter) of the French horn. The difference in resistance is immediately noticeable. All things being the same, the French horn plays much higher than the Baritone and the Baritone plays much lower than the French Horn. For the same amount of exerted force (flow). Hence a smaller exhaust pipe will raise the pitch of your exhaust note, and I'm not even getting into mufflers. Another thing, big exhaust tips or trumpets don't make the pitch deeper, just louder. Listen to any riceboy for proof of that and I won't have to use a musical instrument comparo. IMHO, I'd rather have a pipe that's slightly too small than drastically too big. Even though it's only 1/2" difference, it ends up being a HUGE difference all done. So was that WAY too much description?! ;)  SignatureScott W. '66 Mustang HCS 289 '68 Ranchero 500 302 '69 Mustang Sportsroof 351W '97 Cougar 30th Anniv SE 4.6L ThunderSnake #57 http://home.comcast.net/~scott.williams.613/ Scott, It probably looks good to most folks, but "square inches volume"? It's square inches of cross sectional area or flow area, and cubic inches of volume. A 3" pipe has 7.07 square inches of flow area (A = pi x radius x radius) and a 16 feet length of 3" pipe has 1357 cubic inches of volume (V = Area x length). SignatureJohn ThunderSnake #59 If you Reply, be sure and remove the " (DELETE_THIS) " from the email address. > >I have an 87 gt with a strong 331 supercharged motor running 15 lbs. boost > >. I [quoted text clipped - 45 lines] > > So was that WAY too much description?! ;) > Scott, > [quoted text clipped - 4 lines] > = > Area x length). Yeah, I didn't realize I had it off by one dimension until *after* I hit send. oops, but the theory is still sound. SignatureScott W. '66 Mustang HCS 289 '68 Ranchero 500 302 '69 Mustang Sportsroof 351W '97 Cougar 30th Anniv SE 4.6L ThunderSnake #57 http://home.comcast.net/~scott.williams.613/ > > Scott, > > [quoted text clipped - 7 lines] > Yeah, I didn't realize I had it off by one dimension until *after* I hit > send. oops, but the theory is still sound. Both of you are ignoring the fact that at 15 lbs of boost, a 331 needs to move as much air as a 662-incher. The theories of tube sizing for static displacement go out the door. From the Holley site: > For maximum boost and horsepower applications (12 pounds or more), we > recommend the following engine specifications: [quoted text clipped - 18 lines] > 2-1/4", with 4" collectors > Maximum effective compression ratio on gas not to exceed 24:1 Read the whole page at: http://www.holley.com/HiOctn/TechServ/TechInfo/SCTech.html SignatureCobraJet Thunder Snake #1 >Both of you are ignoring the fact that at 15 lbs of boost, a 331 >needs to move as much air as a 662-incher. He's right. That's why many of the Turbo Regals run dual 3" exhaust and this is with 3.8L or 231ci. Forced induction needs all the exhaust it can get. ///Mike TS #63 1993 BMW 525i http://community.webshots.com/user/mpompe2 Pics of all the old cars - Newly updated Also gotta' remember that forced induction needs less back pressure than an N/A motor. The back pressure in an N/A motor keeps the pressure up a bit during the valve overlap of the exhaust closing and intake opening, this helps with the cylinder fill. Forced induction doesn't need much help to fill the cylinder, but the back pressure is needed to assure the fresh intake air doesn't make it out the exhaust valve during the overlap period. SignatureMike Silver 10th Anniversary Cobra Coupe --- >> Both of you are ignoring the fact that at 15 lbs of boost, a 331 >> needs to move as much air as a 662-incher. [quoted text clipped - 8 lines] > http://community.webshots.com/user/mpompe2 > Pics of all the old cars - Newly updated > > > Scott, > > > [quoted text clipped - 11 lines] > needs to move as much air as a 662-incher. The theories of tube sizing > for static displacement go out the door. From the Holley site: I was too focused on the math problems to see this, but you're damn right! Thanks! SignatureJohn ThunderSnake #59 If you Reply, be sure and remove the " (DELETE_THIS) " from the email address. > > For maximum boost and horsepower applications (12 pounds or more), we > > recommend the following engine specifications: [quoted text clipped - 21 lines] > Read the whole page at: > http://www.holley.com/HiOctn/TechServ/TechInfo/SCTech.html Excellent post. Too big an exhaust will slow exhaust velocity dramatically. Not a good thing if you want any power below top end. LJH 95GT (331 stroker) > >I have an 87 gt with a strong 331 supercharged motor running 15 lbs. boost > >. I [quoted text clipped - 45 lines] > > So was that WAY too much description?! ;) > I have an 87 gt with a strong 331 supercharged motor running 15 lbs. boost . I > am in the process of stepping my headers up from 1 5/8 x 2 1/2" to 1 3/4 x 3". > Should I run the exhaust 3" all the way with a 3" X-pipe and 3" in and out > mufflers or should I reduce to 2 1/2" for some back pressure? Any input would > be appreciated , also any input on muffler reccomendations. Thanks > LarryV Dr. Gas makes an X pipe that is 3" in and 2-1/2 out. Sounds about perfect for you. They sold me that setup for my 342 and it worked pretty good, but I wasn't running any boost. MadDAWG >Dr. Gas makes an X pipe that is 3" in and 2-1/2 out. Sounds about perfect >for you. They sold me that setup for my 342 and it worked pretty good, but >I wasn't running any boost. > >MadDAWG This is a good set-up as the exhaust gas will cool and volumn decrease as it travels through the system. Expense is down also. bradtx > This is a good set-up as the exhaust gas will cool and volumn decrease as it > travels through the system. Expense is down also. > > bradtx The sales guy gave me some big long talk on how the X will make the dual 2-1/2 inch section flow more than the a 3" pipe would, but to be honest it pretty much all went over my head. However it does sound wicked. The Dr. Gas setup is much smoother sounding than my BBK X pipe I have on my shorties now. I just need to get me some 1-3/4 long tubes w/ 3 bolt collector by this coming spring. MadDAWG > I have an 87 gt with a strong 331 supercharged motor running 15 lbs. boost . I > am in the process of stepping my headers up from 1 5/8 x 2 1/2" to 1 3/4 x 3". > Should I run the exhaust 3" all the way with a 3" X-pipe and 3" in and out > mufflers or should I reduce to 2 1/2" for some back pressure? Any input would > be appreciated , also any input on muffler reccomendations. Thanks > LarryV That engine is passing a lot of gas. Treat it like a big block, and go 3" all the way. There's a good article in either Hot Rod or Car Craft this month. They tested a decent big block on 2.5" and 3" pipes. The 3" pipes made more power in the mid and upper range, without any loss of power at the bottom end. Signature.boB '01 Dakota Quad Cab, 5.9/Auto/4x4 '97 H-D FXDWG - Turbocharged! '84 GMC Jimmy - Mountain Beater '65 427SC Cobra FFR Replica - Project '66 Mustang Coup - Daily Driver I have 2.5" exhaust the whole way for my 351C stroked to 377 CID. I get good power through the entire RPM range with max of 340 RWHP @ 5,500 RPM & 400 lb-ft torque @ 3,300 RPM. Yet another $.02 worth from a proud owner of a 1970 Mach 1 351C @ http://community.webshots.com/album/18644819fHAehGJAjt >I have an 87 gt with a strong 331 supercharged motor running 15 lbs. boost >. I [quoted text clipped - 6 lines] > be appreciated , also any input on muffler reccomendations. Thanks > LarryV I have walked into a great deal locally. I have decided to return the hooker 1 3/4 headers I bought. I was picking up a meziere electric water pump from a guy locally when I noticed the exhaust he had in a trash can. It turned out to be a set of kooks 1 7/8 step headers x 3 1/2 with the kooks 3 1/2 in dumps. I picked up the exhaust and water pump for 900$. My plan is to cut the dumps off the headers reduce to 3" run a 3" crossover and put the dumps where the stock mufflers go. What do you think? My neighbors are gonna hate me! > I have walked into a great deal locally. I have decided to return the hooker 1 > 3/4 headers I bought. I was picking up a meziere electric water pump from a guy [quoted text clipped - 3 lines] > the headers reduce to 3" run a 3" crossover and put the dumps where the stock > mufflers go. What do you think? My neighbors are gonna hate me! $900 for a water pump and a set of headers you found in a trash can! Hmmmm . . . . why don't you have a look thru my garbage cans. Honestly, this may have been a good deal if the headers were stainless steel and were for sale, but they were in the trash can for christ sakes! You could have waited til he set them out for pick-up, drove by, and had them for free! Will you be anybody's bitch, or are you his now that he broke it off in you? SignatureJohn If you Reply, be sure and remove the " (DELETE_THIS) " from the email address. > $900 for a water pump and a set of headers you found in a trash can! Hmmmm > . . . . why don't you have a look thru my garbage cans. Honestly, this may [quoted text clipped - 3 lines] > > Will you be anybody's bitch, or are you his now that he broke it off in you? Just because it was stored in a trash can doesn't mean that's where it was headed, dumb a.s... SignatureYOU are the real piece of work in this post. I think you are a couple of drumsticks short of a picnic there bud. - SVTKate > > $900 for a water pump and a set of headers you found in a trash can! Hmmmm > > . . . . why don't you have a look thru my garbage cans. Honestly, this may [quoted text clipped - 6 lines] > Just because it was stored in a trash can doesn't mean that's > where it was headed, dumb a.s... And if you wanted to negotiate for something out of the owners *trash can*, I bet you'd immediately agree with them when they fed you the same line you fed me, "I was just storing them there". Yeah, right! SignatureJohn If you Reply, be sure and remove the " (DELETE_THIS) " from the email address. These kooks headers were in brand new condition stored in a garage. These are stainless in perfect condition . I saw receipts for the exhaust for 1400$ from kooks. The meziere water pump lists for 400 $ and was also in perfect condition. I think I made a pretty good deal. And to the one jerk You come up my way And youll see who I make my bitch! > These kooks headers were in brand new condition stored in a garage. These are > stainless in perfect condition . I saw receipts for the exhaust for 1400$ from > kooks. The meziere water pump lists for 400 $ and was also in perfect > condition. I think I made a pretty good deal. And to the one jerk You come up > my way And youll see who I make my bitch! I'm guilty of pouncing on a post that was not too clear, IMHO. Sorry about that, but this is Usenet. Now that you've filled in some detail, it's obvious you got a pretty good deal. If you'd been more clear and left less to interpretation in the beginning, it would not have happened. SignatureJohn If you Reply, be sure and remove the " (DELETE_THIS) " from the email address. > I'm guilty of pouncing on a post that was not too clear, IMHO. Sorry about > that, but this is Usenet. Now that you've filled in some detail, it's > obvious you got a pretty good deal. If you'd been more clear and left less > to interpretation in the beginning, it would not have happened. Everyone else got it... SignatureYOU are the real piece of work in this post. I think you are a couple of drumsticks short of a picnic there bud. - SVTKate > > I'm guilty of pouncing on a post that was not too clear, IMHO. Sorry about > > that, but this is Usenet. Now that you've filled in some detail, it's > > obvious you got a pretty good deal. If you'd been more clear and left less > > to interpretation in the beginning, it would not have happened. > > Everyone else got it... Somehow I feel better knowing everyone falls victim to your omnipotent mind reading power, except me. SignatureJohn ThunderSnake #59 If you Reply, be sure and remove the " (DELETE_THIS) " from the email address. >>>I'm guilty of pouncing on a post that was not too clear, IMHO. Sorry > [quoted text clipped - 11 lines] > Somehow I feel better knowing everyone falls victim to your omnipotent mind > reading power, except me. My mind? You still don't get it. It wasn't my post but everyone but you knew what he meant. SignatureYOU are the real piece of work in this post. I think you are a couple of drumsticks short of a picnic there bud. - SVTKate > >>>I'm guilty of pouncing on a post that was not too clear, IMHO. Sorry > > [quoted text clipped - 14 lines] > My mind? You still don't get it. It wasn't my post but everyone > but you knew what he meant. There you go again, telling the whole wide world you know what *everyone* is thinking. Well sport, *everyone* in this case is LarryV and you, and I think Larry has called off the dogs. Why do you keep on? I won't even pretend to know why, but I've been around long enough to have formed an opinion about you though. You act like a cross between Eddie Haskell, a pain in the a.s yapping Chihuahua, and a parasite. You ride off other folks posts, absolutely *have* to have the last word, write a lot but don't say much, and suck the life out of the posts you get involved with. That's my opinion. What does *everyone* else think, WindsorFox? Now, let's see if I'm right or not. SignatureJohn ThunderSnake #59 If you Reply, be sure and remove the " (DELETE_THIS) " from the email address. I -was- posting for a few days for the express purpose of pissing several of you off. It worked. Great for me. I'm so proud I could burst. My sincere apologies. I went way too far, again. Been working on that. I am a newb to most of this group. I came in here to talk about Mustangs. And as for "newb", you're only partially correct. When I got my first 67, I posted regularly to this group, in early 96 through mid 98 or so. Then I stopped, wondered if this group still existed six years later, and lo and behold there it was. There wasn't quite the volume of traffic at that time that there is now, the topics weren't quite as disparate, and there was a stronger core user group. Alright. So I extend an olive branch to you. Stike my bullshit from the record. And no, this post is for real. I'll do my best to be a decent fellow hobbyist posting guy. Isn't it ridiculous how silly the things are we can get so WOUND UP about? Using this post as a gauge, I will see what level of willingess there is to accept it at face value, and judge what level of participation I will continue with. >Using this post as a gauge, I will see what level of willingess there is >to accept it at face value, and judge what level of participation I will >continue with. Hmmmm...I judge you to be a turd. No level of participation is what I expect from you. Clear? >>Using this post as a gauge, I will see what level of willingess there is >>to accept it at face value, and judge what level of participation I will >>continue with. > Hmmmm...I judge you to be a turd. No level of participation is what I > expect from you. Clear? Damn...Harsh! But exceptable. I think I love you!!! LOL I didn't expect a single response. Just remember that many people cannot admit fault for something for their entire lives. But being at fault for something? Try going a day. >>>Using this post as a gauge, I will see what level of willingess there is >>>to accept it at face value, and judge what level of participation I will [quoted text clipped - 4 lines] > > Damn...Harsh! But exceptable. I think I love you!!! LOL >I didn't expect a single response. That's makes you a *dumb* turd. > Just remember that many people >cannot admit fault for something for their entire lives. > >But being at fault for something? Try going a day. Blah, bla blah, blah blah. So are you leaving or not? >>>>Using this post as a gauge, I will see what level of willingess there is >>>>to accept it at face value, and judge what level of participation I will [quoted text clipped - 4 lines] >> >> Damn...Harsh! But exceptable. I think I love you!!! LOL > Blah, bla blah, blah blah. So are you leaving or not? Hmm... I don't know. I guess it will have to be a surprise, you glib little bitch. I promised myself I wouldn't run over children with their tongues stuck out at me, but I may again give in to temptation. >> Blah, bla blah, blah blah. So are you leaving or not? > >Hmm... I don't know. Not knowing seems to be your pattern. >I guess it will have to be a surprise, you glib little bitch. I promised myself >I wouldn't run over children with their tongues stuck out at > me, but I may again give in to temptation. Ok, so now you're a pissy stupid turd. >>>Blah, bla blah, blah blah. So are you leaving or not? >> >>Hmm... I don't know. > > Not knowing seems to be your pattern. Yep, so far, you're right. I've changed my mind again, and I've decided not to give a rat's a.s what you or what anyone else thinks. I might be nice, but I might not. I might contribute some friendly advice. I might run you over. I don't care if anyone replies, and I don't care if anyone cares. I will use this group for information and entertainment whenever I want to. >>I guess it will have to be a surprise, you glib little bitch. I promised myself >>I wouldn't run over children with their tongues stuck out at >>me, but I may again give in to temptation. > > Ok, so now you're a pissy stupid turd. You just made me blush. I'm not pissy, I'm Wound Up. And I'm very, very far from stupid. Psychologists have tested me ad nauseam to find out just what screws are loose upstairs. My intellectual aptitude is not the problem. I have a graduate degree, am well-read, trilingual, and have a voracious mental appetite, so I'm more than adequately educated. I may act the fool sometimes, but I am not a fool. I am what I am. Call me a turd if it makes you feel better. I don't give a sh.t. A better description would be "rightfully arrogant, unstable, and pissed off". Enjoy the rest of the weekend, Carmen. If you're a sports fan, I hope your team wins. >>>>Blah, bla blah, blah blah. So are you leaving or not? >>> [quoted text clipped - 8 lines] >anyone cares. I will use this group for information and entertainment >whenever I want to. I can assure you, if you leave *no one* will give a sh.t. :) >>>I guess it will have to be a surprise, you glib little bitch. I promised myself >>>I wouldn't run over children with their tongues stuck out at [quoted text clipped - 11 lines] > A better description would be "rightfully arrogant, unstable, and >pissed off". Spoken like the guy who got a lot of swirlies and wedgies in high school. >Enjoy the rest of the weekend, Carmen. If you're a sports fan, I hope >your team wins. Heh, trying to make nice-nice now? Pussy. >>>Using this post as a gauge, I will see what level of willingess there is >>>to accept it at face value, and judge what level of participation I will [quoted text clipped - 3 lines] > >Damn...Harsh! But exceptable. I think I love you!!! LOL Haha! < tips hat> The headers are stainless in perfect condition and they were for sale. They were in a plastic can that had never been used for garbsge. He also showed me receipts for the exhaust which was 1400$ from kooks. The meziere water pump retails for 400$ So I think I made out pretty well. Bring your mustang up my way (if you even have one), and will see who's the bitch! Technically, when the trash can is put out for the garbage pickup.... it is the property of the city/county government, or in some cases the garbage contractor if the contract is incl;usive. Therefore, awaiting the items to be placed out for pickup and removing them is... THEFT... >> I have walked into a great deal locally. I have decided to return the >hooker 1 [quoted text clipped - 16 lines] > >Will you be anybody's bitch, or are you his now that he broke it off in you? Entering into the unknown, V'ger seeks information used to maintain his Vintage Burgundy 1965 Ford Mustang 2+2 w/289 ci 4v oem A Code V8, C4 Trans, 16x8" Vintage 40 wheels, with BF Goodrich gForce T/A 225/50ZR16 tires, American Racing "Mustang" Centercaps, and a whole lot of other stuff; ) > Technically, when the trash can is put out for the garbage pickup.... > it is the property of the city/county government, or in some cases the > garbage contractor if the contract is incl;usive. Therefore, awaiting > the items to be placed out for pickup and removing them is... THEFT... True, but from a practical standpoint wrt the trash can owner, what does it matter? As long as it gets taken away. Now, wrt society, it's a win-win situation. Someone gets rid of their junk, someone gets something they want, and the neighborhood dump is one item less full! I've never heard of anyone in their right mind calling 911 on the guy cruising the neighborhood in a pick-up right before garbage pick-up looking for valuable junk. Please pardon this insult beforehand, but are you a lawyer? SignatureJohn If you Reply, be sure and remove the " (DELETE_THIS) " from the email address. No. I am a retired cop who has had to respond to those 911 calls which nobody makes. I am one of those people who must waste hours filling out forms and filing reports which go to the DA so the DA can decide to prosecute or not. In more than one case we found people who had "collected" trash and were running 7 day a week yard sales, without permits. They were making considerable amounts of money upon which they paid no taxes and thus contributed nothing to support the local economy to help pay fopr me to waste hours investigating, etc etc etc. In other cases we found that the owner's kid(s) had left things out which were subsequently hauled away. Everything from lawnmowers to bicycles valued at several hundred dollars and in one case a Harley left lying on it's side by the drunk who rode it home and dumped it in front of his house amid the trash barrels. Nope. Nobody ever calls 911 about people "stealing" trash. They just call 911 and report a theft. And quite often, when you interview the owner, you find that they would have given the stuff to anyone who asked for it. But, hey, it's your tax dollars being wasted. I always got my paycheck. >> Technically, when the trash can is put out for the garbage pickup.... >> it is the property of the city/county government, or in some cases the [quoted text clipped - 8 lines] >in a pick-up right before garbage pick-up looking for valuable junk. Please >pardon this insult beforehand, but are you a lawyer? Entering into the unknown, V'ger seeks information used to maintain his Vintage Burgundy 1965 Ford Mustang 2+2 w/289 ci 4v oem A Code V8, C4 Trans, 16x8" Vintage 40 wheels, with BF Goodrich gForce T/A 225/50ZR16 tires, American Racing "Mustang" Centercaps, and a whole lot of other stuff; ) Oh that's precious . . . a drunk ditches his Harley amongst the trash cans and the bin diver gets it! LMAO! SignatureJohn ThunderSnake #59 If you Reply, be sure and remove the " (DELETE_THIS) " from the email address. > No. I am a retired cop who has had to respond to those 911 calls which > nobody makes. I am one of those people who must waste hours filling [quoted text clipped - 40 lines] > T/A 225/50ZR16 tires, American Racing "Mustang" > Centercaps, and a whole lot of other stuff; ) The guy who took it did time for that little "trash" pick up. You know, if it ain't locked up or tied down, somebody will swear they thought it was free for the taking. >Oh that's precious . . . a drunk ditches his Harley amongst the trash cans >and the bin diver gets it! LMAO! Entering into the unknown, V'ger seeks information used to maintain his Vintage Burgundy 1965 Ford Mustang 2+2 w/289 ci 4v oem A Code V8, C4 Trans, 16x8" Vintage 40 wheels, with BF Goodrich gForce T/A 225/50ZR16 tires, American Racing "Mustang" Centercaps, and a whole lot of other stuff; ) |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.