collector mod?

[wed3k]

the longer you make it, the more flow you'll get however i dont have any scientific theories supporting it.

[PR CB7]

i love old threads, seeing jose, rafa and bagoon makes me

[marcusv8thunder]

So far my research says,

Short primarys= good for high end
long primarys=mid range
short secondaries=?
long secondaries=?
short collector= high end
long collector=mid range

Firstly can someone confirm this?

My theory based on the above is short=high end, so this would mean shortening the secondaries would/could also = high end?

[reklipz]

I think that if you really wanted to analyze this you should start with the simplest scenario and work your way up. I could be way wrong on this, but it makes sense to me.

An individual header / exhaust for each exhaust port on the head would be your baseline. So, what does the difference in length of the "header" on an individual cylinder mean? I say "header" meaning the part from the exhaust port on the manifold all the way to the first restriction: the catalytic converter I would assume.

From there, I assume the next best thing you can do would be to combine the most disparate exhaust ports, i.e. two cylinders whose exhaust strokes are the farthest apart (180 degrees in our case). The first restriction would be the collector point on there. I think the goal is to make that restriction as minimal as possible, and my naive approach would be to say: take the exhaust header diameter and double it; that should give the least amount of restriction up until the cat.

And so on... Sorry if this is vague or unnecessary, but I hope it helps paint a picture. Again, I have no real experience here. Someone tell me to keep my trap shut if I'm out of line, .

[Joey GT-R]

Big bump?

Seriously? You couldn't just start another thread?

While I appreciate you taking the time to search; if you have to go back 3+ years to find something of relevance I don't think anyone would have minded.


Now I gotta go move this thing....

[PR CB7]

if one doesnt search then its bad, and if one bumps an old thread its also bad

no need to change this joey, the only thing wrong with this, its that is old nothing else

bump for the thread, im also interested on header lenght differences

[marcusv8thunder]

Been reading some books, seems like shortening those secondaries will move the specific peak rpm up the rev range a bit, but the effect is minimal, however the diameter of them is still important.

Like 80% of the differences are inside the head even before it enters the exhaust, then the manifold/header, is the next most important. On the diameter of the collector, if your primarys are less that 2" like mine are, then a collector of 2.5" will hurt low rpm torque, with some, but little gain up high. A compromise of 2.25" is what im shooting for currently. (This is for a stock/small amount of bolt ons, F20a and F22a)