your opinion of hedman headers will change. they did not use quality anything for the header they make for the civic... before installing, sand off all of their 'high temp paint' and respray with real stuff.

with an header(s) its more important that there is quality, rather than specific dimensions.

o.g.l. is right about exhaust theory and all that. it is more complex and you dont pay us enough to explain it in depth :p

I actually like the torque-step header I bought for the civic. I know the factory paint sucks but this one was ceramic coated. It has alot more low end torque so drving it like a granny is easier. My fuel economy did go down, however. I think it is mainly due to the 5-wire O2 sensor not getting hot enough quickly enough. I am going to weld in a O2 sensor bung where two of the tubes come together (4-2-1 header w/ equalizer tube in the 2 part)and then wrap those tubes with the high temperature header wrap lindermen sent me (awesome guy). I know backpressure effects and fluid mechanics are complex but I'm just experimenting..... Would you weld in the O2 sensor where I intend to weld it or the equalizer tube (h-pipe)? Thanks

ceramic is a much better choice than their 'high temp paint' but is it a good idea to weld onto a ceramic coated header??

and the 'equalizer tube' does not have a constant flow of exhaust so i dont think it would be a good idea there either.

you put this header on a vx?? hmm anyway its losing fuel economy because of the decreased exhaust velocity in the runners, not because of the o2 sensor, or backpressure. it is a heated wideband o2 sensor.

what is the exhaust like that this header is dumping into?

heres a link that may be helpful, i haven't read though it recently so i don't recall how useful it would be.
backpressure

Interesting...
 

Good link Nathan, but 2 concerns:
1. The link discusses small aircraft engines that run at a constant RPM for long periods of time.

2. The VW tuners wanted a full-range of engine operation from idle to redline

Otherwise, very informative and detailed.

I found an old thread relating to the topic. I've been procrastinating on this exhaust for over a year :o ...I'm just paranoid to make it less efficient with a replacement.

Since we drive primarily at low RPM for FE, I'm willing to give up higher-end power/torque to have more readily-available torque at lower RPMs.

So when taken the practical theories gathered, and if the conclusion of the thread is true:

More Backpressure = Torque;
Less Backpressure = HP.

I'm still entertaining the idea of a header...but i dunno.

Regarding piping, we're pretty much limited to how long the vehicle is, and the intended route by the manufacturer. Mandrel bends are definitely a plus, but diameter is still in question. Using equations from another site (recall a link from here somewhere), one can find the optimal length of pipe from the engine's exhaust valve position, RPM, etc. Does this mean, cutting it short into a side-pipe?

Still corn-fused. :confused:

RH77

Ick, there is really nothing to gain from having backpressure.

Since you are most concerned with low rpm torque, your ideal headers will have narrow primaries (I think thats' the name of them) with lengths designed for your ideal rpm range.

The headers designed for high rpm torque (horsepower) use a larger runners as well as larger ports, valves, intakes etc, because of the larger amount of air flowing through them. At lower rpms these induction/exhaust systems are too large to keep the air moving quickly and smoothly. The opposite happens when you use low rpm tuning, the engine can't breath at higher power levels.

Your best bet is trying a commercialy available header, they almost all flow better than the strock restrictive system. Some stock manifolds flow fine, but most are pure crap. Up until the 80's they were all designed to just get air from one place to another, it isn't until recently that OEM's considered how they could make them flow well. My favorite example is right herehttps://img.nextag.com/image/1998_98_.../501881327.jpg They run the first exhaust port to the second ports, creating a bit of back pressure for it to fight against, with out enlargening the pipe to compensate for twice the exhaust flow, then if this isn't enough, they add the 3rd exhuast in with it, and expect it to merge smoothly with the much slower, and less pressurized gas from the 4th exhaust port :thumbdown:

Ahh, here is a GREAT LINK to exhaust header design.https://www.team-integra.net/sections...sp?ArticleID=2

Sweet
 

Holy crap :eek: sweet link! That answers a LOT of questions I've had for a long time. I'd like to get rid of that rusty chunk of a header with a lighter, better breathing unit. Regarding an exhaust, I've had my eye on the RS-R ExMag for a long time. Free-flow without a lot of noise. Unfotunately it's $$$. :rolleyes: The torque curves show the right design to look for. Excellent.

RH77