Had A Exhaust Question

[-Alero-]

what if, i went straight piping, from the downpipe back withonly a muffler. this muffler would be the camaro style muffler. any ideas on what exactly this would sound like?

i know straight pipes are illegal, but knox county doesnt do pollution tests. i know of plenty of trucks around here without a cat, and or muffler.

[flalero]

Do it! I did it on my car, and it's really easy and cheap if you know how to weld and use a sawzall. I just bought a section of pipe from Midas for about $10, went to the auto hobby shop on base, cut off the cat and silencer with a sawzall and welded up the straight pipe. Keep one thing in mind. It is easier to weld the top of the pipe (where it is closest to the body of the car) if you have the exhaust removed from the car.

[-Alero-]

yeah but what does it sound like, im perfectly capable of mig welding, but i dont know how i'll get a lift, or get the exhaust off.....i need to think more into this. if i wanna do this i wanna do all 2.5 from the downpipe back. or should i start where the cat used to be?

[Yomeo]

o , thats fast

[flalero]

It does make it a little bit louder. My exhaust sounds a little raspy, but not quite ricey. Yours will probably sound a lot better since you are getting a camaro style muffler. My muffler is kind of like something you would see on an import. I would replace all of the piping with the 2.5" piping. Any muffler shop should be able to easily bend this for you. However, it could get kind of expensive when you get to welding a flange on for the exhaust manifold connection. I would just cut it off between the cat and flange and re-weld the flange onto the piping. It was pretty easy for me because I just replaced a four foot section of piping between the exhaust manifold and the bend that goes over the suspension. Anyway, good luck. Heres a pic of my muffler, so you know what kind of style I'm talking about.
http://memimage.cardomain.net/member_images/1/web/541000-541999/541534_24_full.jpg

[-Alero-]

Originally posted by Yomeo@Apr 25 2005, 01:16 AM
o , thats fast
Quoted post


what made you say that?

[flalero]

^^^Yeah, I was wondering the same thing? What are talking about? I think he's talking about our sigs. Alero, I would have to agree with you on the Prelude thing. I have yet to beat any Prelude.

[-Alero-]

yeah its B/S.....i was so mad that night. cant wait till i can get a job and a beater and just dump nothing but money into the alero.....all just to beat a damn prelude...

[flalero]

The only one I've ever beaten was one of the newer ones with a auto/slapstick tranny. I don't get it, there's a guy running around with a civic that has B18 v-tec swap and I beat him all the time. Oh well!

[-Alero-]

maybe one day when my alero is older and all grown up i'll be able to beat one.

[-Alero-]

but anyways!, has anyone else doen this setup? and does anyone think this is a good idea or bad idea?

also, if the stock cat flows better anyways, i wont even notice any sort of gain with it there or not, am i right?

[flalero]

Actually, it seems like the removal of the cat and silencer was the single best mod I made to my car. I've taken my CAI and MAFT off of they car and I feel almost difference at all.

[-Alero-]

whats a MAFT?

anybody else have good reviews about this?

also, falero dod you have a 4 cyl or the v6?

[mike2002]

ive seen dyno's of "stock cat" "no cat" and "highflow cat" on the same car. they had a huge article in car craft years ago. with no cat, the car lost significant low end, gaining a little in the higher rpm over stock. highflow cat showed gains across the board.

i wouln't chop your cat off, your car will smell like poop if you do. and when a cops behind you and your car reaks, he may decide to pull you over. and the fine for no cat is over $20,000.

on a near stock car 2.5" is to big. you hear everyone saying you'll loose backpressure, loosing low end. there only half right. you dont need back pressure. what you need is exhaust velocity for low end. the bigger the pipe, the less the velocity. backpressure itself hurts you. all these guys on this board have a big ass pipe with a flowmaster muffler. this is about the worst setup you could have. the pipe is huge so they loose velocity (but also loose backpressure which is good) then the muffler has all these baffles in it giving them more backpressure. the best setup would be a smaller pipe and a muffler with no baffles. that way you drop backpressure, but you still keep exhaust velocity. if want even less back pressure than that, get a highflow cat

i put a strait through magnaflow on my car and it was loud as hell, so i got a 31" thrush glasspack and it quited it down alot, but my exhaust doesn't have 1 baffle in it, so even though i have a smaller pipe than most guys, i have less backpressure than most.

[-Alero-]

ok so if you say having a smaller diameter pipe is better than a bigger one, then why not just keeps the stock piping??? since its so much better? 2.5 isnt really that big, thats like saying the SLP exhaust makes you loose horsepower.

im pretty confident i'll keep my cat, but just upgrade the cat back piping, to 2.5 im pretty confident it will be fine with benefits, besides the v6's have a decent amount of low end torque but little to no hiogh end torque, so if anything, the more high end torque the better....

and as for my muffler choice, i wont go Slowmaster again, im gonna try to get that Magnaflow camaro style muffler, for the dual exhaust thing

[Spilner521]

small piping is not necessarily better than bigger piping. you have to get the right size for your engine to maintain decent exhaust gas velocity but still be big enough to have maximum flow at the top end of the rpm band. the stock piping is great for low end, but on the top end it doesnt flow well enough to reduce restriction. and like mike2002 said, you want the least backpressure and restriction, and the most free flowing muffler possible.

i have the 2.4 engine in my car but i have driven a few v6 aleros completely stock and i agree, that engine is full of low end torque. so if i were you, i'd go with full 2.5"piping from the manifold back, high flow cat or no cat at all, and a straight through muffler. and if its too loud for you throw in one or two straight through glasspacks or resonators to quiet it down a touch.

[-Alero-]

Originally posted by Spilner521@May 1 2005, 04:41 AM
small piping is not necessarily better than bigger piping. you have to get the right size for your engine to maintain decent exhaust gas velocity but still be big enough to have maximum flow at the top end of the rpm band. the stock piping is great for low end, but on the top end it doesnt flow well enough to reduce restriction. and like mike2002 said, you want the least backpressure and restriction, and the most free flowing muffler possible.

i have the 2.4 engine in my car but i have driven a few v6 aleros completely stock and i agree, that engine is full of low end torque. so if i were you, i'd go with full 2.5"piping from the manifold back, high flow cat or no cat at all, and a straight through muffler. and if its too loud for you throw in one or two straight through glasspacks or resonators to quiet it down a touch.
Quoted post



thank you, i plan on doing that, but i am not sure how well the magnaflow muffler flows :glare:

[mike2002]

you want dual exhaust or twin tip exhaust? not that it matters for flowing, all the magnaflow mufflers are strait through, no baffles.

2.5" slp will give you more power, your car will have higher peak hp, but it will have less hp in the lower rpms. so it does "add hp" but that doesn't necessarly mean your car is faster. also, the stock muffler is very very restrictive, and the slp one is a strait through design, so you have overall alot less back pressure, but unfortanatly less velocity. like spliner said, you have to find the best pipe size for your application, you can go to big, you can go to small. for a 170hp car, 2.5 is ridiculously big. borla had a better setup with 2.25" mandrel, stock is 2" pressure bent. its my opinion that 2" mandrel bent is the best setup for a near stock car (like ours). but the companies know to sell the kits, people want bigger, the average person putting exhaust on there car will order the kit with the biggest pipe. 2.5" mandrel isn't needed unless you are running forced induction.

i could have upgraded my piping from 2" to 2.25", but for the cost, and the fact that i would be switching out stainless steel that will last forever for aluminum that will rust out in 3 years of snowy weather ( i know because i found out the exhaust on my last car just fell apart, rusted through, 3rd winter with it's aluminum pipe) i decided to keep the stock piping and just elimintate the back pressure by using a strait through muffler (magnalfow) if i want to further reduce my backpressure, i could get a highflow cat.

[mike2002]

so the moral is, big exhaust pipe is only for bragging to other kids in study hall that you have it.

take a gtp for example. alot more time and money has been spent on research and development of performance parts for that car. stock they put out over 300lbs of torque (they are underrated). lightly moddified ( stuff like pully, rockers, intake, dhp other small bolt on's....basically a mid to high 13 second car) they recommend not to go over 2.5". so if they use 2.5" for 300+hp cars, do we need it for our 185hp (after mods) car?

[-Alero-]

:wacko: then why is everyone so much more staisfied, with the 2.5 piping rather than the 2.25?

i know i will go stainless steel. but if you read closely, the borlas exhuast is overpriced and isnt even stainless steel. im pretty confident i will go will custom piping.

but the thing i dont understand is that, if i were to get headers, the header piping is 2.5 so if i were to get 2.25 cat back piping wouldnt that create restriction, than rather having 2.5 overall

[Spilner521]

Originally posted by mike2002@May 1 2005, 04:12 PM
for a 170hp car, 2.5 is ridiculously big. borla had a better setup with 2.25" mandrel, stock is 2" pressure bent. its my opinion that 2" mandrel bent is the best setup for a near stock car (like ours). but the companies know to sell the kits, people want bigger, the average person putting exhaust on there car will order the kit with the biggest pipe. 2.5" mandrel isn't needed unless you are running forced induction.
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i agree......if it was a 170hp 4 cylinder. but you have to take into consideration this is a 3.4 liter v6, a decent size engine. you need room for all that exhaust to fit into. thats why the 2" stock piping is too restrictive. upgrade to 2.25" and you maintain velocity and it opens it up a little for the top end. upgrade to 2.5" and you push the peak power higher into the rpm band but also could gain a few hp with the bigger, more free flowing piping. swap to a high flow cat and gain a few more hp. ditch the cat for a completely unrestrictive exhaust and gain even a few more hp. its all the little gains that add up. plus if you plan on further modding the engine in the future, you've already got a good size exhaust to support those mods.

as for forced induction, you want the biggest piping possible. the pressurized intake charge pushes the exhaust out of the cylinder during valve overlap so you dont have to worry about the scavenging velocity to draw it out. you just have to worry about free flow and no restriction, especially with turbos. any restriction or backpressure what so ever could slow down the turbine wheel and cause excessive turbo lag. 3" piping is a must for boosted applications. anything bigger would be better, but you'd have a tough time fitting it under the car and going over speed bumps without scraping anything.

[Spilner521]

so the moral of this story: the bigger piping you go on a NA car, the higher in the rpm band the peak power output is. in my opinion, 2.5" header back without a cat is ideal for a lightly modded 3400 v6. so you sacrafice maybe a little low end grunt for that top end power, but the engine puts out enough torque to make up for it. 2.5" piping will give decent power gains and leave room for further mods in the future.

mike2002, nothing against you here at all. just stating what i think would work better and how it makes sense to me.

[mike2002]

borla is stainless steel, but it is expensive. very few shops bend stainless steel, most have aluminum. the stainless steel pipes are pretty expensive compared to aluminum.

headers dont give you more power because they're 2.5" they give you more power for a few reasons. 1 there are no ridges, it a completly smooth setup. on the stock exhaust manifolds the exhaust comes out and hits a basically 90* wall, and has a very rough path to make its way back to the cat. lots of sharp corners, which is bad for backpressure AND velocity, which is why headers designed correctly give you power through the whole power band.

also, they help from scavanging. if all the pipes come together in circular kind of twist motion, what happens is the exhaust comming out of one cylinder gets to this point right when the next cylinder is venting out, if made correctly (by varying pipe size and length) the exhaust passing through will actually help to suck the exhuast comming out of the next cylinder, THATS what makes a good header(s)

edit: the bigger pipe does help, but its not as significant as its made out to be. you have alot more velocity by the engine then you do at the tailpipe, which is why its more benifical to have bigger pipes at the engine than the end of the exhaust

people are so happy with there 2.5" because they see how big it is and now they can brag to there friends that they have "2.5" catback" for a stock car like mine, intake/exhaust/dhp/pully is the most i had ever planned to get for it, so for me it was more benifical to keep the stock pipe. if your planning on headers, 2.25" is your best bet. you may be able to pick up a used borla kit of here, or grandamgt.com. since its stainless steel it will last forever. the grandam borla kit is dual exhaust, the alero kit was twin tip

[-Alero-]

hmmm well, considering i didnt even ask for a definition of what headers do....im gonna still have to ask you.... why would you go from 2.5 in piping (headers) and then downgrade to 2.25 from the cat back?

and at first i could of sworn borla wasnt stainless, it was just normal steel or something, i forget. but anyways aluminum piping will work just as good as stainless. people say it rusts, when it actually just corrodes, but that takes years/abuse.

[mike2002]

Originally posted by -Alero-@May 2 2005, 02:46 PM
hmmm well, considering i didnt even ask for a definition of what headers do....im gonna still have to ask you.... why would you go from 2.5 in piping (headers) and then downgrade to 2.25 from the cat back?

and at first i could of sworn borla wasnt stainless, it was just normal steel or something, i forget. but anyways aluminum piping will work just as good as stainless. people say it rusts, when it actually just corrodes, but that takes years/abuse.
Quoted post


i give up, put 2.5" on your car. then you can brag to the kid at checkers you have 2.5" exhaust. you need the 2.25 to maintain decent velocity, the headers are 2.5" for different reasons, and your going to have more exhaust pressure at the headers because of all the exhaust combining/scavanging and whatnot, hence another reason why the headers piping should be a little bigger than the rest of the exhaust. your car is also lightly modded, the s&s is also made to accomadate more heavily modified cars, they arn't going to make 2 series of headers for a low demand car. if you were running cams, heads, intake mani's, tb blah blah, then you'd want 2.5" back

and the aluminum does rust, maybe its from the reaction of the weld, whatever it is, mine rusted through. and it does take years, as in 3, thats how long it took mine to rust through. my aurora was lowered, which helped to speed the process, since it was in more contact with snow/water than if it hadent been lowered i guess.

[Spilner521]

Originally posted by -Alero-@May 2 2005, 03:46 PM
hmmm well, considering i didnt even ask for a definition of what headers do....im gonna still have to ask you.... why would you go from 2.5 in piping (headers) and then downgrade to 2.25 from the cat back?
Quoted post


yeah i have no idea where headers came into this conversation. going big to small from the engine back? good question. doesnt make much sense to me. if you have 2.5" going into 2.25" towards the back its just going to cause restriction trying to squeeze the amount of exhaust in the bigger pipe down into the small one. restriction is bad.

depending on mods 2.25" is good for small 4 cylinders, 2.25-2.5" for larger 4's and small 6's, and 2.5" for larger 6's. 3400's are decent sized v6 engines. you need room to flow that much exhaust. you'll be happy with 2.5". and trust me, 2.5" piping will do you more good than just being able to brag to 12 year old girls that you have a big exhaust. and if you decide that you do want headers, you'll even gain a little more. like i said before, its all about the little gains here and there that add up.

[Redog]

Just buy a kit :rolleyes:

[-Alero-]

Originally posted by mike2002+May 2 2005, 10:59 PM--><div class='quotetop'>QUOTE(mike2002 @ May 2 2005, 10:59 PM)</div><div class='quotemain'>Originally posted by -Alero-@May 2 2005, 02:46 PM
hmmm well, considering i didnt even ask for a definition of what headers do....im gonna still have to ask you.... why would you go from 2.5 in piping (headers) and then downgrade to 2.25 from the cat back?

and at first i could of sworn borla wasnt stainless, it was just normal steel or something, i forget. but anyways aluminum piping will work just as good as stainless. people say it rusts, when it actually just corrodes, but that takes years/abuse.
Quoted post


i give up, put 2.5" on your car. then you can brag to the kid at checkers you have 2.5" exhaust. you need the 2.25 to maintain decent velocity, the headers are 2.5" for different reasons, and your going to have more exhaust pressure at the headers because of all the exhaust combining/scavanging and whatnot, hence another reason why the headers piping should be a little bigger than the rest of the exhaust. your car is also lightly modded, the s&s is also made to accomadate more heavily modified cars, they arn't going to make 2 series of headers for a low demand car. if you were running cams, heads, intake mani's, tb blah blah, then you'd want 2.5" back

and the aluminum does rust, maybe its from the reaction of the weld, whatever it is, mine rusted through. and it does take years, as in 3, thats how long it took mine to rust through. my aurora was lowered, which helped to speed the process, since it was in more contact with snow/water than if it hadent been lowered i guess.
Quoted post
[/b]

uh, trust me aluminum does not rust....i am a welder. it corrodes and the welds can rust yes. but anyways light mods or not, a cat back exhaust is a basic/light mod anyway, but i just dont see why you would go from 2.5 then to 2.25.....makes no sense. im not getting the biggest piping just to brag at checkers. im getting whats best for my car in the future, im pretty confident i will dump more money into the car further down the road, its just maybe taking care of exhaust once and only once is better than redoing it twice.

Originally posted by Spilner521@May 3 2005, 02:22 AM
<!--QuoteBegin--Alero-@May 2 2005, 03:46 PM
hmmm well, considering i didnt even ask for a definition of what headers do....im gonna still have to ask you.... why would you go from 2.5 in piping (headers) and then downgrade to 2.25 from the cat back?
Quoted post


yeah i have no idea where headers came into this conversation. going big to small from the engine back? good question. doesnt make much sense to me. if you have 2.5" going into 2.25" towards the back its just going to cause restriction trying to squeeze the amount of exhaust in the bigger pipe down into the small one. restriction is bad.

depending on mods 2.25" is good for small 4 cylinders, 2.25-2.5" for larger 4's and small 6's, and 2.5" for larger 6's. 3400's are decent sized v6 engines. you need room to flow that much exhaust. you'll be happy with 2.5". and trust me, 2.5" piping will do you more good than just being able to brag to 12 year old girls that you have a big exhaust. and if you decide that you do want headers, you'll even gain a little more. like i said before, its all about the little gains here and there that add up.
Quoted post
[/quote]

yeah going 2.5 isnt gonna hurt. the 2.5 from headers all the way back just seems to make more sense

[-Alero-]

Originally posted by Redog@May 3 2005, 08:53 AM
Just buy a kit :rolleyes:
Quoted post


you dont tell me how to live my life! lol :lol: ............................... :cry:

[mike2002]

[/quote]

yeah i have no idea where headers came into this conversation.
[/quote]

headers came into the conversation because someone said "why would i go from a 2.5" header to a 2.25" exhaust" well i explained how/why headers are the way they are because a explanation was obviously needed if you think you need 2.5" exhaust because the header has a 2.5" outlet.

[/quote]
going big to small from the engine back? good question. doesnt make much sense to me. if you have 2.5" going into 2.25" towards the back its just going to cause restriction trying to squeeze the amount of exhaust in the bigger pipe down into the small one. restriction is bad.

depending on mods 2.25" is good for small 4 cylinders, 2.25-2.5" for larger 4's and small 6's, and 2.5" for larger 6's. 3400's are decent sized v6 engines. you need room to flow that much exhaust. you'll be happy with 2.5". and trust me, 2.5" piping will do you more good than just being able to brag to 12 year old girls that you have a big exhaust. and if you decide that you do want headers, you'll even gain a little more. like i said before, its all about the little gains here and there that add up. [/quote]

i didn't think i had to explain the reason why you wouldn't want 2.5" AGAIN, but for kicks, i guess i do. with 2.5" you dont have enough veloicty to get good torque from the engine. the headers are 2.5" to accomadate such things as heavy mods, which you dont have. the larger size of the headers IS NOT NEEDED in your application, your car is NOT benifiting from 2.5" over 2.25" in the header. its benifiting from the other things i already explained in a previous post, which is why i explained them. please read this again, and again

a 170hp pushrod v6 does not benifit from 2.5", it hurts it. my friend just ordered a borla exhaust kit for his CORVETTE and its 2.5", its a 99ls1. so do you think if this 5.7L 345hp car needed only 2.5, you also need it? LMAO. you dont need 2.5" unless you were running at least 300hp. i dont really car if you put it on your car, but im just trying to prove a point

[/quote]
uh, trust me aluminum does not rust....i am a welder. it corrodes and the welds can rust yes.[/quote]

UH trust me, ive had aftermarket aluminum exhaust and the person i sold it to just told me it rusted through, and then i saw it (sold the car to a family member)corrodes or rusted, the whole thing is shot, and not just at the welds, the pipe is all brown with what looks like rust, but i guess its somthing else.

[mike2002]

im done ranting:)

[-Alero-]

mike! ask anyone here, aluminum does not rust! if yours rusted, then it wasnt aluminum. like i said it will corrode and only corrode.

also back the 2.5 thing. you know im not trying to get 2.5 just to brag to 12 year olds or be cool like a corvette or try to be something im not.

its just, with that 2.5 headers and 2.5 cat back exhaust it just seemed so much more reasonable to have. in fact i forget who it was exactly (he's on this board), but all he had was "light mods" including a CAI or WAI i forget, and SLP cat back exhaust, once he got headers he dynoed a 27 whp gain. so im pretty possitive it doesnt matter if you have heavy or light mods, headers will benefit no matter what. offcourse with the teamwork of a cat back exhaust.

but yeah i know for a fact you will loose some low end with the bigger the pipe, but what i was trying to say earlier was, the 3.4 has plenty of low end torque, and not enough high end. but yeah :wacko:

[Redog]

I'll do you the favor.....locked