tumbaumba

I would like to make an unequal length header for my K24A1
Which runners do I need to make longer? I am guessing I can do cyl 1 & 3??
How do I calculate how much longer the cyl 1&3 runners need to be ?
I want the maximum rumble sound I can get


I got a couple of stock k20 headers that I am going to hack up and try to make this happen
I'd like to keep it 4-1 configuration and keep the stock collector and the stock catalytic converter - to keep everything legal and pass emissions
And add loops to cyl 1 and cyl 3 runners to make them 40-50% longer

Is there a way to calculate if this would give a good rumble ? Or would 4-2-1 make a better rumbler ?

tumbaumba

Hope this makes sense
1.

2.

Pro-SeriesFab

Primary length, size, and shape of bends are a function of RPM/displacement/valve size/port size and to a smaller degree packaging.

If all you care about is sound/looks then asking here won't matter . . . just build whatever you think looks good.

tumbaumba

The goal is to have maximum rumble with minimal performance loss (if at all possible)

I was looking for some rough guidelines from someone who understands the math behind it.
Such as :
It is better to loop cylinders 1&3 or 2&3 or other combinations ?
How much length (in % terms) should I add to the looped runners ?
Should I maintain the same diameter as stock runners if doing this to the OEM header ?

Or it doesn't matter at all?

k20z1ej1

maybe just buy something that increases performance while making it rumble? ie big cams

tumbaumba

it would be a waste of $2K+ (for vtec killer done right + k pro and tuning)
Will not rumble above 900rpm
Will not rumble at all while driving
Will not increase performance at all for the rpm range I drive in

Pro-SeriesFab

The problem is "rumble" is subjective . . . we don't have a quantifiable means of measuring this.

To me, you either build a header because it looks cool and you like the bends or you planned it out according to pipemax or actually doing some math.

tumbaumba

I see

My thought process was that the rumble sound is measurable

As in
Equal length = equal distance between all exhaust pulses - no rumble

If I increase the length of cyl#1 primary by X% - it alters the cyl#1 exhaust pulse by X amount in relation to exhaust pulses of cyl#2,3&4

So (in theory) there should be a way to calculate which combination of 2 primaries need to be lengthened and by what %... in order to have the exhaust pulses arranged as far from being equal as possible

Maybe I am overthinking this

Ryanthegreat1

It is a Honda not a Subaru, head back over to nasioc.com.

tumbaumba

It is Plastic not Metal, head back to myspace.com
Everything alright with you bro?

Ryanthegreat1

Do whatever you want man. Seems counter productive to loose power trying to make your car sound like it has a dead cylinder. Hey why not just unplug a fuel injector, same sound, less work.

If you want the Subaru bro sound go buy a Subaru. I don't see the appeal.

tumbaumba

Thank you for giving me permission to build my exhaust header.
From now on, before I modify any of my cars, I'll make sure to ask you whether the modification is in accord with your beliefs.
I will lose power? What makes you so sure about this? Are you clairvoyant? At what rpm will I "lose power"?
Does a 3 cylinder engine sound the same as a 4 cylinder to you? Do you randomly unplug fuel injectors before driving you car? This makes no sense at all.
What does this have to do with Subaru at all? I should drive a car I don't want to drive because why?
That's like saying to everyone on honda-tech to just go buy a Vette if they want to go fast. Or to just go and buy a Saab if they want a turbocharger. And so forth and so on.

turbociv910

cylinders 1 and 4 then 2-3 should merge. having either of them swapped will just cause turburlence in the exhaust..

Ryanthegreat1

I think turbulence is what his is going for to get that sick subi rumble.

tumbaumba

doesn't this depend on the length difference of the unequal primaries?

can all cylinders merge into a 4-1 collector (with unequal length primaries) ? why or why not?
thanks.

tumbaumba

Is turbulence related to the exhaust note and how? Care to explain? Are you just repeating random things you've read on the internet? Go get a moped if you want that sick fuel efficiency.

the_unknown

Turbulence in a way is related to the sound, but not directly. What you are trying to do to get that "rumble" is pair the cylinders together so the pulses of 2 of the 4 cylinders exit at the same time, then the other 2 at their time so you get separate exhaust "pulses" thus creating a more rhythmic "loping" exhaust sound. The problem with this is that the pulses of the cylinders that fire together being paired together will ram into each other and cause turbulence in the exhaust which can decrease flow, thus killing power.

This has been discussed many times before and most people frown on this because it serves no purpose other than the noise (which most people dont like anyway) yet it actually does kill horsepower, which is why you get the hate for it. These types of mods will never be a popular choice with the general public, and especially not with people that like to improve their cars.

I say improve because there are two types of car-people, those that modify their cars to make them better in one way or another, and those that modify their cars because they can and want to be different. These two philosophies will never see eye to eye and will frequently bump heads over mod choices. If you want to do this you already know how, you have received your answer from this board on what others think about it, now if you still want to do it, DO IT. You dont need to defend your stance, you dont need to convince any of us that what you are doing is OK, so not sure what else you are looking for.

And yes this will make your honda sound like a Subaru, which (in my opinion) sound like **** anyway...

k20z1ej1

i loled pretty good reading that

tumbaumba

The claim of UEL header killing power is based on your imagination. We would need at least mathematical explanation of how the UEL primaries alter the powerband. Ideally we would need a dyno graph of a naturally aspirated K2.4l with and without UEL. Before we have that, it's just an imaginary argument based on your beliefs.

I am pretty sure I will not be able to convince any of you. I am just pointing out how illogical your arguments are.

Let's look at the most obvious first. The vast majority of "acceptable" modifications (that everybody drools over) do NOT make cars better in any way.
Lowered/stiffened suspension car = slower and more dangerous on uneven public roads. Rear bumper lips = turbulence, makes the car slower.
All aftermarket wheels that are not lighter than stock wheels = makes the car slower.
All air intakes with the filter located inside the engine bay.
Pretty much all exhaust systems on stock/nearly stock motors = noise only
Shifting your powerband to upper rpm = noise and slow
RHD conversions, front end conversions.
Painting your car a color that is not a Honda color
Installing a spoiler or any aero part that hasn't been tuned in wind tunnel on your car

And so forth and so on, I could keep going with this list but I'll stop here, you get the point.

All of these mods do not make a car better in any way shape or form. It's only done to be different.
These mods serve no purpose and/or make cars slower and noisier.
Yet they are widely acceptable.
But god forbid somebody decides to make a UEL header because why? Because according to your imagination, it will "kill horsepower" and turn the car into a bicycle and make the planet explode?


It will not sound like a Subaru because it is not a Subaru. Not to mention that there are many Subaru engines, some turbocharged and some naturally aspirated and they all sound different.
That's like saying that putting a Magnaflow exhaust on your Honda will make it sound like a Dodge Neon SRT4. It makes absolutely no sense.

Why only bring Subaru into the discussion? Do you run around telling Porsche guys they sound like Subarus? What about all the rally teams with UEL headers on various 4cyl cars (including Hondas), do you run around telling all of them they are making their cars sound like a Subaru and "kill horsepower"?

Bottom line, these arguments have zero logic.

Caoboy

you know how bad you feel after eating a lot of taco bell after a night of drinking/partying?

and you're all backed up and you have to take a massive poop?


That's literally how you're going to make your engine feel by creating an unequal length header.


Just think about that. You're literally doing nothing good. You might as well just take all four primary runners and just weld them right into each other and tie that in with your exhaust.


And yes, it literally robs HP.

Primary example? Look at all the companies that make equal length manifolds for Subarus. Why? because it provides a smoother flow of exhaust gasses, which increases scavenging, allows for gas to flow faster, which in turn increases HP.


Don't take my word for it though, I only do mods for typical things like increasing performance.