please help! what header to buy and modify

Hello - I've been reading through past posts on the subject but I'm looking for a clear answer on this. I'm about to take my aveo into the shop for a custom mandrel bent tube exhaust. The mechanic said doing a custom header would take some time and he started to whine about it, but he seemed more enthusiastic about me buying a header for another car since none are available for the aveo, and just modifying it to fit.

I've read on previous posts that the civic D16 performance header on ebay is a good starting point, and can be modified to fit. Is it difficult to modify? What needs to be done? Does this leave enough room for a magnaflow high flo cat?

get a header for a 1.8 motor. get a flange from gseturbo and give it to a welding shop. thats all u gotta do.

ok, 1.8 but from what make and manufacturer? does this look like it will fit the bill?, it's for an integra: http://tinyurl.com/5pwvjr

can someone post some links to something on ebay and just tell me what to buy?

does gseturbo have a site to order from? when I take it to the shop do I have to tell them to do anything special to get things fitted correctly?

Your help is much appreciated, i just want to make sure i get it right the first time to avoid headaches later.

hit up daewootech.com

here is the daftart engineering section on daewootech, message garret(gseturbo) and he will lead u to the right direction: DAEWOOTECH

give him couple days, sometimes he gets busy with his shop.

Thanks mike, I contacted gse so I can get the flanges.

However, one of my friends emailed me and said the following:

"but they will need to do a really
good job on welding the flange together because with engine torque and
solid, bolted exhaust mounts, the welding at the flange and the header
tubes can snap and then your right back where you started or worse. It's
rare but i've seen it on crappy parts that have been bought off ebay,
even if people don't run alot of horsepower the regular engine heat and
crappy welding just dont mix well and the welds just crack and snap
apart. Again though, I caution that there isn't enough information or
R&D put into this whole idea to have it run 100% smoothly and it's
likely that its going to be more trouble then its worth. Premade afterm
arket parts have all of this already worked out, and thus installation
is much easier."

My friend seems to dislike the idea as you can see...

perhaps just doing an exhaust past the manifold would suffice? the stock manifold can't be too restrictive, my guess is the stock cat, and the inefficient bends in the stock tubing, once removed, would improve things enough on their own.

i'm trying to find a balance between improved performance and still keep things practical enough to keep the car as my daily driver...

the difference is the crappy welding done on cheap parts from ebay is typical quality of an 11 yo boy in taiwan (sorry shy). And even then they are typically only press fit with a small tack or short seam, not fully welded around. Even a subaverage welder is going to get good enough penetration that if the header was going to brake it wouldn't be the weld, and i am sure that a purchased flange is going to be higher quality than one a cheap ebay manufacturer would use also.

the only problem i foresee is if you just weld the flange on and expect it to fit. i would think you would want modify the runners to match the flange, then bolt the flange into the car, and install the header to test fit everything, tack it, and the pull it from the car and fully weld. but that mean down time for the car, as it has to stay with the fabricator.

anyone have pics of the stock header without the heat shield on? part of me is just debating if it's even worth it touching the header....

IMO, getting a header made isn't worth it. Your car will have some downtime and you don't for sure how it will hold up. If it was readily available from the aftermarket, I would say go for it but this could turn into a huge headache. I'd say just go with a hi-flow cat and new piping.

thanks for slapping some sense into me :)

as far as engine performance, i dont know where you are as far as simple mods go. but :

for better engine breathing, people tend to go in this order:
1. K&N replacement filter
2. catback
3. cai (instead of K&N replacement filter, dont do both)
4. cat (larger, hollowed or test pipe)
5. header

so if you haven't dont the others yet i would wait on the header too.
most exhaust shops could fab up a decent catback for @ $300..
a cold air intake in front to match (actually out of the engine compartment is better)

if other stuff was available i would say chip the car first. but i dont think there is a thing like APR, revo, or giac for us.

i haven't pulled the heat shield or looked at the header. but most of the time you have to really need to have built the engine to need to breath before getting a header. things like cams, bigger injectors, advanced timing, etc are often more performance that a header will be, but we can't get chips to match.

Would it be worth Porting out the stock manifold?

Not unless you do it yourself, already have all the tools, and alot of free time. In other words, I wouldnt pay for it to get done.

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Originally Posted by aveodude

Not unless you do it yourself, already have all the tools, and alot of free time. In other words, I wouldnt pay for it to get done.

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thats all true. plus, if you haven't looks at it yet(i haven't) is it even cast that you could port it? the "other" economical car i bought had a stamped steel manifold. not porting sheet metal. plus if you do it yourself failure is more likely. cause when do you know if it is too thin for the heat?

i have an AEM CAI in my car so far, that's the only engine mod so far. I think i'm going to go with a magnaflow high flow cat, 2.25 inch piping to a flowmaster 40 or 60 muffler... i'm going to remove all the resonators and everything else, but keep the stock manifold....sound like a plan?

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Originally Posted by xdmitrix420

i have an AEM CAI in my car so far, that's the only engine mod so far. I think i'm going to go with a magnaflow high flow cat, 2.25 inch piping to a flowmaster 40 or 60 muffler... i'm going to remove all the resonators and everything else, but keep the stock manifold....sound like a plan?

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that might be too big. loss of back pressure will cause loss of power in lower rpm range.. and delay throttle response.

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Originally Posted by petrified.rabbit

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Originally Posted by xdmitrix420

i have an AEM CAI in my car so far, that's the only engine mod so far. I think i'm going to go with a magnaflow high flow cat, 2.25 inch piping to a flowmaster 40 or 60 muffler... i'm going to remove all the resonators and everything else, but keep the stock manifold....sound like a plan?

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that might be too big. loss of back pressure will cause loss of power in lower rpm range.. and delay throttle response.

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Might be a little loud, but you can always add a resonator or another muffler if you don't like the sound.

As for back pressure, that helps burn more fuel and thus cleaner emissions, however you do not need back pressure for power. What you want is exhaust velocity. Please research the difference and not post "loss of back pressure will cause loss of power in lower rpm range" as it is wrong will discredit the rest of what you say.

Exhaust velocity is the term of the speed of the exhaust flow and scavenging ability of the exhaust and typically goes up in higher rpm ranges. But with a lower velocity at idle, the back pressure is important to keep the engine running smoothly. if you are going to set your idle to 2500 rpm then yeah only worry about velocity. if you want to idle at 700 rpm(what ever is stock) then you also need to maintain back pressure if you want the car to produce power before the car hits 2500 rpm from a stop. its been proven on a dyno that once you go past a certain size where the back pressure is lost, not only does the engine not produce the same power until the rpms are past a point, but also that the car will start having trouble idling. and if you go past a reasonable exhaust velocity then it will produce less power across the entire power band.

2.25 is not too big of a choice for exhaust velocity so why mention that?, 2.5 with tuning could be done. but being that i doubt he has a turbo. a chip, a cam, itbs, standalone, or anything else that allows you to eliminate the need of back pressure that the oem fuel injection management accounts for at idle, he will need to maintain back pressure. A high flow cat, 2.25 pipe with only a 60 series muffler probably wont have enough restriction for a 1.6 liter engine to produce back pressure

is the performancec just going to completely suck below 3k rpm with the 2.25 piping? i thought 2inch or 2.25 were accepted 'norms' on this forum, at least from what i read from others about their exhaust setups.

the shop said the smallest they is go is 2.25, otherwise i would have done 2 inch i suppose.... would keeping one stock resonator in help out with backpressure? i figured by using the stock header that would also retain enough backpressure , the exhaust isn't being sent out as smoothly as it would be with a custom header. perhaps upping the idle by a few hundred could also help, is there an easy way to do that or does it involve hacking the cpu?

i might do some more serious engine mods after the exhaust work, like custom pistons, cams, etc, so 2.25 might come in handy. however, that might be some time down the road.

you can't say if it will suck or not, i dont know the numbers like the restriction or back pressure your stock exhaust has, and them how much each of your new components will produce. on a mildly modded car you can usually stand to loose almost 50% of the back pressure. with tuning sometimes more. but that varies with makes and models. if you were to go with a tunable muffler you could probably do straight pipe entire length and then tune the muffler to how you want or need the car to run. a resonator does add some back pressure but i wouldn't reuse stock you and you can get a decent resonator in the pipe diameter you are running for cheaper than labor to cut and fit the old one. but everything i have to say has been discredited because i addressed back pressure instead of velocity.

a very none technical way of seeing if you car will run without back pressure is to pull the exhaust apart and run the car. you will want to keep both 02 sensors in the system so to eliminate a lot of back pressure but not all would be disconnect the midpipe from the cat and run it. taking the cat off would eliminate almost all the back pressure. but to appease subachad, this will also change your exhaust velocity. in our shop we had a test exhausts that we could put on the car that had a tunable muffler and adjust to perform.

that's interesting just using only a tunable muffler, definately would simplify things, and simplicity is good :) just out of curiosity what do people when they have no cat and have to do their emissions inspection like we do every 2 years in maryland? bolt the stock exhaust system back on and then go do the emission test?

you will need someone local to answer that, i know pa law not maryland.

in pa
newer cars only get obd2 testing, so if you have programming that by passes the secondary 02 sensor, so the light won't come on. you will pass the actual test. if they don't offer a chip tune. then you can fabricate a mil eliminator. to keep the cel off. most people put in dummy cats (or hollow out their stock ones) to pass the visual part of our test. (as long as it was not done by our shop, to hollow out a cat for someone is illegal)

for sniffer tests you need to be tuned well, depending on hat the states perimeters are for your car it should be able to pass without a cat. If it doesn't then you can retest. and some shops around here who still have their old sniffer equipment (the ones not hook directly to the states computer) will do a pretest and tune to get you into the range. other people i have heard of running denatured alcohol at a 10:1 ratio the tank before your test will make you pass. but i don't recommend it.

most of the cars we did aren't driven in winter. so they all qualify for the >5000 mile exemption. plus i think it is up to pre 84 now only needs to pass a gas cap test.. (that part keeps changing) and we didn't typically see a lot of typical people come back for maintenance. only the high end cars would come back for that.

I would say 2" piping would be the right choice for the stock engine. Talking to a few local performance shops, they recommended 2" from the cat back with a flowmaster 60 and keeping one resonator in. There was another member on here that removed both resonators when they did their exhaust and had to put them back in because it was way too loud.

if it was legal, i would straight pipe 8)

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Originally Posted by acdc1287

if it was legal, i would straight pipe 8)

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Some people may disagree but a straight-piped four banger is almost the worst sound you can get from a car.

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Originally Posted by 07_aveo

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Originally Posted by acdc1287

if it was legal, i would straight pipe 8)

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Some people may disagree but a straight-piped four banger is almost the worst sound you can get from a car.

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oh yeh, its horrid!

i got 2' repipe with megan duals, no resonators, punched out cat, and slightly modded headers, my **** loud as hell. if i dont have my silencers in for the winter, there would be no way id be able to allow my car to warm up in the driveway, it shakes the house and pisses off the neighbors.

is my setup (2.25 inch piping, highflow cat, muffler) going to be obnoxiously loud? should i tell them to keep one resonator in for good measure?

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Originally Posted by xdmitrix420

is my setup (2.25 inch piping, highflow cat, muffler) going to be obnoxiously loud? should i tell them to keep one resonator in for good measure?

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if u like ur exhaust loud, then no resonators, if u live in a residential area, and ur neighbors like u and u wanna keep it that way, keep a resonator in. get a good one tho that will match ur new exhaust pipe size like a vibrant resonator or a loudmouth.