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?
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.
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.
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.
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