even though a 4-2-1 header doesn't exist for the xB, I've been meaning to ask this for while...
What exactly is the difference between the two... I mean other than the obvious physical differences. Why would one be preferred over the other? and how do they differ in function (like what is the theory behind the differences in the way they work)?

 

421 is for broad torque range. 41 is for top end horsepower. what the other has it gives up in the other respect. street car 421 is better. monster torque car 41 ok.

 

can't beat a balanced tuned exhaust for the street

 

oh thanks, but.. i'm also wondering why it works out that way...

 

I can't give you an answer specific to the scion, but in general the idea is to match exhaust pulses (so they "pull" the trailing pulse down) within a certain RPM range to make more power withing that RPM range.
I guess 4-2-1 matches pulses more in the midrange than a 4-1 header does.

Make sense?

 

Header theory is complicated. From: http://www.tprmag.com/issue/9/9_b16_headers.shtml

In general, with all other factors being the same, a four-into-one style header will generally show its best performance gains toward the top-end of the powerband, near engine redline. A 4-2-1 design header generally shows performance gains across the powerband from low-rpm to high-rpm. However, the ultimate gain at the higher rpms may be more with the 4-into-1 design.

Before you think that the configuration (4-1 or 4-2-1) is all that matters, understand that there are six other major factors that influence the performance characteristic of a header. The diameter of primary tubes, secondary tubes, and collectors, along with the lengths of the primary tubes, secondary tubes and collector(s) will all influence the performance characteristic of the header.

All in all, header design is an extremely complex affair. Someone could design a four-into-one header that works very well at low and middle engine speeds. Someone else could engineer a 4-2-1 header that performance best at high rpm only. The header that works best for your vehicle is going to depend a great deal on the other high-performance components that are part of your performance combination, as well as the type of driving that you will be encountering.

 

Actually, there are 4-2-1 headers out there for the xB (try SEARCH for threads or just Google it). Mostly, I think 4-2-1 are 2-piece (flange-boltable) designs, while the 4-1 are one piece from manifold to cat.

Peek behind your XB engine cover and you'll find that Scion/Toyota spent some engineering $$$ on providing some form of tubular headers for this engine. Probably not a true high-performance/HP/torquey design, but there ARE four separate tubes leading from the head (possibly stainless by the looks of them?), they're just covered over by a formed shroud or something.

Certainly better than a cast manifold (which would've been easier and cheaper), I expect the design is aimed at middle-of-the-road HP and torque over a broad range of RPMs. Just a thought there, Chimmy3 . . .

 

Thanks for the info everyone... I think i have an idea of why it works the way it does now.

also...

I have yet to see a 4-2-1 header for the xB.

I see a lot of pieces which are really 4-1 headers and mislabelled and sold as 4-2-1 headers.
This is just like how a lot of "cat-back" exhaust systems for the xB are really axle-backs... the online store just mislabels it.

DC sports
Megan
Alphawerks
Strup

all make 4-1 headers... but occasionally you'll see stores selling them as 4-2-1... with a generic pic of a 4-2-1...

One of the reasons i asked is b/c the DC sports 4-1 header was shown to lose some low-end power. So if, generally, 4-2-1 headers provide BETTER low/mid range power (which is what our cars need IMO) then why has one never been made and everyone is making 4-1 headers...

 

Not going ito whats best or not, because there is no real answer there, there are companies that make 4-2-1 for the 1NZ-FE. Yasio Factory makes one ( check out http://www.yashiofactory.jp/i_love/vitz/muff/index.htm

 

i have been waiting fot a 4-2-1 header, is there any way we can get the Yasio Factory header here in the US?

 

you may want to check out:

http://scionsport.com/store/product_...a69e30af1a904f

 

Companies haven't been able to put together a 4-2-1 header because of the lack of room. The tight is fit and its hard to come up with something so technical with the room that is given. Granted, it can be done, they exist for the Bb. However, people want a 4-2-1 with more whp gains than a 4-1, in return, that makes it complicated.

Cya

 

I bought my header from them, its a 4-1.

 

what power gains are they getting from the 4-2-1?

 

it depends. if you want to see better hp gains normally aspirated you would need to shorten the A pipe(pipe after exhaust manifold) and have an exhaust header longer in length.

look at a turbo manifold or even a header best suited for SC applications. You'll see a 4-1 quick scavaging header(short) you'll gain low end torque sacraficing hp and top end(boost spooling means more). Since we have tight gearing its not such a bad idea. Is anyone here looking for 125mph in the back straights of Watkins Glen? Probably not. A 4:1 quick scavaging is sufficient for such a small motor. We get going faster if you were to step on it more so then a top end header. Scion xA/xB top end...lol..i just made a funny.

here is my old hytech exhaust header. notice Dshaped primaries, anti reversion chambers and a megaphone at the end.

my NA 1.9 liter honda motor dynod 246whp with 165torque. What i would give to have that in my toaster. 4x50mm Throttle bodies urrrrhhh urrhhhhh




notice... 4-2-1 but at 14.7:1 compression making the hp i was.... i wanted something for the entire power band when drag racing.

btw..i own Partshippers and the reason i sell the Strup products is for quality and efficiency. And yes...Charlie Westrup owner of Strup Performance was the GM for DC for many many years.

scion lifers discounts on them here.

https://www.scionlife.com/forums/vie...794&highlight=

 

yeah i used to be into hondas had a 95 civic, not too bad but now i got a baby girl on the way so i needed something bigger. Most of my friends are goin turbo with them. one of them is gettin 330 to the wheels and he just had some major head work done and otherthings, probly goin to see 370-400 at the wheels, he wants 600whp

so u reccomend strup header?

 

yup...its the reason i sell them. i'm still a honda fan btw..no question.