Custom Headers DC5 K20Z

[PolitoHood]

I have a choice of sizes.
I want the 4-2-1 configuration.
My question is,

What would be the best sizes for it. I do intend to modify the engine internal in the future so bear that in mind.
these are the sizes im working with.

2” = 51.2mm

2.25” = 57.1mm

2.5” = 63.5mm

3” = 76.1mm

Would the best set up be 57.1mm - 63.5mm - 76.1mm or will the 51.2mm - 63.5mm - 76.1mm be better??

please explain your opinion

[ChargeR]

If the person building your header does not know enough to decide these diameters and primary and secondary lengths for his/herself I think you are wasting your time. Find a Toda or SSR header and copy it.

[PolitoHood]

If the person building your header does not know enough to decide these diameters and primary and secondary lengths for his/herself I think you are wasting your time. Find a Toda or SSR header and copy it.

It for my knowledge. their the sizes they said they can do. I want a larger collector than the toda manifold i want it at least 70mm. work with me here!

[tinkerbell]

i have a stainless steel k-series header plate for sale.

the K's port holes are big, so go with the 57mm for the 4 sections? (i.e. no proper reason)

[PolitoHood]

Thanks Dave.

One of the places Im getting to quote said this, but im mindful that they mostly do Holden V8 work.
"All the equipment and tube sizes in Australia are based on the USA which is imperial.

We could do 2” primaries, 2.25” secondaries and 3” outlet.
This will make power further up the rev range and would be suited to highly modified engines, ¼ mile times and dyno numbers.

If it is a stocker and you mainly use it for a street car, we could do:

1-3/4” primaries, 2” secondaries and still finish with a 3” outlet.

This will give you more low down power and better mid range power which is ideal for the street."

[tinkerbell]

so it is simple,

use the information you have been provided with (from the various places) and corelate this to your intended purpose of your car/engine...

you say you will be doing internals?

is it for racing on the circuit or straight line?

[tinkerbell]

and if you search on K20A.org, you may find dyno graphs comparing small primaries to large primaries?

link to search page

[tofu]

here's something i found
http://www.custom-car.us/exhaust/header.aspx

just as reference, the j's racing 4-2 header has 45mm primary with 50mm secondaries.

[tinkerbell]

what is the Toda?

[PolitoHood]

TODA has new design for the K20Z engine

Primary Runners 45mm
Secondary Runners 50mm
Middle Section 55mm~60mm
Collector 60mm
Source http://todaracingusa.com/product?cid=14&id=718

The Version for the K20A is the one we see here

Primary Runners 45mm
Secondary Runners 50mm
Collector 60mm

[fatboyz39]

My advice, buy a set already available. You'll spend months and months trying to get the combo right.

[m0nty]

My advice, buy a set already available. You'll spend months and months trying to get the combo right.

QFT.

Why gamble on making someting that companies such as TODA have spent hundreds of thousands of dollars developing? Chances are you're never gonna get close to the gains you get from their systems anyway. And custom ain't cool if it's giving you less powaaaa!

[PolitoHood]

I have read a lot on people using 3" systems great improvements but i dont know who makes them.

[03DC5R]

get toda headers with 3'' catback...

[ChargeR]

I have read a lot on people using 3" systems great improvements but i dont know who makes them.

Get one of these and add a muffler (or don't): LINK

Your JDM options for a 70mm are J's 70RR, Mugen N1, and Tracy Sports. I am sure there are others but I their names escape me at the moment.