CUSTOM , HEADER ( 4-1 & 4-2-1 / Selection / Design / Fabrication )

[mykwikcoupe]

cool man let me know when you finish the orders you have now on the a20a pipes and well start on the b20a. Dont want to throw a wrench in the works by changing stuff to early. Anytime is good for me just send me a PM when your ready. Mike

[Justin86]

cant wait till the 5th!! too bad we wont be able to start with a baseline. . . . .no base line is better then no dyno run at all.

I think some one around here did get a base line dyno awhile back, if I can just find that thread.

[Justin86]

Yea I tried to look at all those different profiles, and then I looked at the race headers and half of them didn't seem to follow those basic principles. So I tried to stick with the basic principles as best i could but I didn't go with the 50/50 ratio of 1st to 2nd piping.

[Accordtheory]

yeah, I guess I was confusing myself about the cylinder pairing order..the cylinders that fire 360deg apart should be paired, and that would be 1&4 and 2&3 in this case. But it doesn't matter for me anyway...

[3_GENCYCO]

When can i buy one? im ready for one now. i was just shopping for a header...

[Justin86]

Well I will be getting it dynoed on March 5 and after that I will figure what to do about production and the price. I wish were able to get a base dyno run first, but another guy did it a year ago and got 83hp/94tq on his 87 Lx-i and that goes with the typical 15% drivetrain loss. So NXRacer and his 86 Lx-i should be close to the same.

[Vanilla Sky]

with me getting ready to start planning a custom header, i'd like to see how this one does...

as for your flange, that's just a local job, right?

[Justin86]

yea I had the flanges done locally with a CNC plasma.

[A20A1]

What are your thoughts... for those of you that wander around honda-tech

http://www.honda-tech.com/zerothread?id=1161501

...

I got my welder back from my friend... I'm gonna mess around, I haven't gotten my hands dirty in a while.

I don't know what your header looks like so I can only give you a general answer about what it is and how it works.

It's usually a larger sized chamber close to the exhaust port in the primary tube of the header and functions like a step. It's designed to keep the exhaust gasses from flowing backwards into the cylinder before the exhaust valve closes. This will help ensure that the cylinder gets filled with the freshest intake charge that isn't contaminated with leftover exhaust gasses, which will make more power. Like fluid, it's harder for the exhaust gases to travel backwards and upwards over a step than it would be if it was a simple round tube with no steps.

That's what it is and how it works in a nutshell, I'm sure the header manufacturers like Dave from SMSP etc could give you more detailed explanation.

A stepped header delivers a short duration (short duration = narrow affected rpm range / long duration = broad affected rpm range) expansion wave when the positive pressure wave reaches the step.
In headers the Positive waves exit through the exhaust valve and exhaust gases move in the same direction of the wave towards the open end of the pipe... once the positive wave exits the pipe is returns a negative suction wave that travels back up the pipe towards the cylinder... but the exhaust gases move opposite the direction of the negative wave. This is supposed to help lower the pressure in the cylinder and help it fill better. True that the smaller diameter also acts as a restriction to the exhaust gasses...

REVERSION is the secondary pressure wave that travels back up the primary pipes and enters into the cylinder on valve overlap. As this pressure wave travels back up the pipe, it brings with it all the residual gases still left in the pipe. This is what contaminates the fresh intake charge. Enter in stepped headers and ANTI-REVERSION chambers, placed at strategic locations in the primary pipes. These methods are employed to tune the arrival of the exhaust wave and to diminish the effects of the high pressure in the pipes. The results are higher volumetric efficiency and more power.

...it sounds like someone is suggesting they block negative expansion waves... the negative wave is what gives you the scavenging effect. Scavenging = so blocking the scavenging wave isn't a good thing... timing when it reaches the overlap period is.

Reversion is usually when the exhaust gases enter the cylinder or intake manifold and act against the incoming air... usually it's because of high overlap cams operating at a low engine rpm. Or a poorly designed header.

I'd say a stepped header may add some low speed gains but I would rather tune the tube lengths and diameters to get the most power for my application.

I see Hytechs Anti-reversion chamber as an Expansion chamber that flows freely in one direction but not in the other... this is okay for limiting the exhaust from reentering the cylinders but when you expand gasses they slow down :thumbdown: .
Good exhaust systems usually try to keep exhaust velocity high ...without adding too much restriction which is what increases pumping work. :thumbdown:

Small pipes = More velocity
Small pipes = More restriction :thumbdown:

Large pipes = Less Velocity :thumbdown:
Large Pipes = Less restriction

I wont try to knock Hytech's idea... but I don't see why you would want it if you have a properly tuned header. IMHO

Negative (returning) expansion waves are undesirable in headers and manufacturers often design in things like steps and anti reversion chambers to help reduce this pulse. Scavenging is very desirable but it is a "suction" created behind the departing pressure wave pulse, when the exhaust valve opens. That suction helps create a vacuum in the cylinder so it will fill more completely with a fresh intake charge and therefore make more power. A Negative returning pressure wave HURTS the scavenging effect because it actually pushes exhaust gasses back into the cylinder reducing cylinder filling efficiency.

Normally, every time the exhaust pulse reaches a point in the exhaust where it opens up into a larger area like the collector, a reverse pulse wave is reflected back up the pipe towards the exhaust valve. Negative pulse waves are going to happen in every header design so the best header designs incorporate features that help to reduce this effect as much as possible.

Certain design features like making the primary tube opening slightly larger than the exhaust port and smoothing the transition or "step" into larger diameter piping help reduce the negative pressure pulse wave. The first anti reversion feature I mentioned creates a physical step for the returning pulse wave to overcome, in order to re-enter the cylinder. The smoothing of the transition area when moving into larger piping which can be in the primary tubing and collectors helps to maintain velocity and significantly reduce the strength of the negative pulse wave.

There are other things that can be done like using cone shaped collector extensions and designing steps into a headers primary tubes at specific distances to help cancel out negative pressure waves. Building headers isn't an exact science, but it is a science and simply building them using different lengths and diameters of tubing that work isn't always the most effective way to make power on every application.

These pressure waves can be used to our advantage because they have the effect of moving gas particles along with them. A positive, or high pressure wave will propel gasses in the same direction that it is travelling. A negative, or low pressure wave will propel gasses in the opposite direction that it is travelling. Take a moment to let this sink in, because this simple fact is at the heart of exhaust system tuning. Although the pressure wave is moving at the speed of sound, it will propel the gasses at a much slower speed. An example of this is a boat that catches a wave from another boat that is motoring by. As the wave passes it will propel the boat in the same direction the wave is traveling, but at a much slower speed, and the wave will eventually pass the boat completely. This is the same thing that happens to the gas molecules in the exhaust system as a pressure wave passes through them.

These pressure waves respond in an interesting manner when they reach a sudden area change in the pipe. An example of a sudden area change is the collector, where the two pipes empty into a larger diameter pipe, a megaphone, or the end of the exhaust where the pipe empties into the atmosphere. When a pressure wave reaches a larger cross sectional area, it will reverse its sign (positive becomes negative, and negative becomes positive) and its direction. For instance, when the exhaust port first opens, a strong positive wave will travel to the end of the pipe, change to a negative wave, and travel back to the exhaust port. This is called a reflection. Both the positive wave traveling towards the end of the pipe, and the negative wave traveling towards the exhaust port will propel exhaust gasses towards the end of the exhaust system which is exactly where we want them to go. The amount of time that this cycle takes is defendant on the total distance that the wave has to travel.

I dunno... both my engine building book and the site quoted above say that the negative waves assist gas outflow.
Maybe I am mis-labeling or mis-interpreted what hytech labels as a negative wave in relation to what I'm describing and thats where the confusion exists...
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[Justin86]

Well I designed the header for someone with more mods then basic and at least a 272 cam.

well no dyno yet, but here is what it sounds like with my new exhaust set up........
http://www.sirrommotorsports.com/pho...ebsexhaust.mov

[NXRacer]

new header pics
https://www.3geez.com/showthread.php?p=500527#post500527

[Justin86]

yea but the only problem with that for me is having to get a spool gun($400) and a new tank for the CO2. If your current tank has the 75% CO2 mix you have to get a different tank for some reason to run the 100% mix. I'd rather save up to get a TIG

[A20A1]

I could make one for the B20 it would help a lot if I had an engine to weld it on so I know it fill fit for sure.

Maybe find a old head with simmilar ports to the B20... then lay it on the A20 block and secure it down... it should give you some idea.

[Justin86]

Yea that what I'm thinking along as the deck height and oil pan clearences are similar to the A20
ok and we we say B20 you talking about the JDM accord B20 or the prelude B20. Other wise I could use a pic of the engine/oil pan, where I can get a head to weld on, and dimiensions of the engine. Hopefully the A20 block is similar other wise I would need the actual engine to make it fit for sure.

[epic1400cs]

yea but the only problem with that for me is having to get a spool gun($400) and a new tank for the CO2. If your current tank has the 75% CO2 mix you have to get a different tank for some reason to run the 100% mix. I'd rather save up to get a TIG

Its my 2 cents but I also recommend to go for TIG with Argon gas if possible. With TIG you can control the heat area much much accurate = constant welding bead = good strong finish. Especially with stainless steel, if you use gas-after-flow well, you don't need to do much after welding. I guess, the pipe wall thickness would be a couple of millimeters and the falnge will be like 9 mm so if the TIG welder can handle 120 Amp that would be fine. There are lot of option available these days - pulse, step etc - but unless you use thin sheet under 1mm or welding gas tank, the basic one - just on/off plus gas after flow control - will do the job. Good luck.

[Justin86]

yea you read my mind and I have been in the market for picking up a TIG and plasma cuter, maybe some other goodies. I want to start working with aluminum and SS more and the TIG is the best bet. I like the MIG a lot for welding thicker steel but when I starting welding thinner stuff it took me awhile to get a good weld. It was either too hot or not enough penetration at first.

[epic1400cs]

I want to start working with aluminium and SS more and the TIG is the best bet. I like the MIG a lot for welding thicker steel but when I starting welding thinner stuff it took me awhile to get a good weld. It was either too hot or not enough penetration at first.

Sir Justin 86, yes TIG is the king. If you want to work with aluminuium, you might want AC/DC out put switch - alu wants to be welded in AC than DC. Also for thin material, step will be handy to control the heat build up they say, but the price will be very expensive. I have worked with TIG first as a job and recently I have bought MIG for my DIY project. Portable MIG is good for its price but DIY range doesn't come with variable amparege control - like low, mid, high and I need to control heat build up by welding speed and wire speed. So you cant always weld with your best condition. Also you grip the TIG torch like pencil, not like stick, which give you more accuracy.

[Micah 89LXi]

the level of dedication in your work is amazing man...i am really impressed...alas i have have an Lx-i EFI engine....and further down the road id be really interested in purchasing one...maybe ill just have to get the DC Sports one...good work tho man

[NXRacer]

i've been rolling with this header and you dont really need a dyno to show the crazy gains in response and power.

Dyno numbers would deffinately be nice though.

[Strugglebucket]

what ever happened to Justin86's header?

[onliLX-i]

So this means us guys without headers are still screwed. I might buy a used header just because there is nothing else. Where can you get a used one? I am also wondering what the down pipe diameter is? Anyone know what the DC sport header down pipe size is?

I see. I wish I knew about this forum before I had my exhaust redone. 2" cat back. I would have to replace all that piping to take any advantage of a header. The guy at the shop told me anything bigger than 2" would be anti-beneficial. Started rattling off about back pressure. What about scavenging you !#%*&.

It is all we can still get that is commersial.

Why restriction? A choke?

[spnrx]

I'm still lost as to what to do Exhaust wise, A guy told me $280 for a 2.5" Cat back with magnaflow muffler. What headers would be best? like I heard Pacesetters weren't that good but a good number of people use them on here.

[loko84hb]

looks like those guys could make sum sick ass headers...at a pretty penny...

[onliLX-i]

Does this cteate a vaccume effect to suck the gasses out? What if you just ran the four header pipes all the way back to the bumper and had four exhaust pipes? I know this is rediculous but what would that do?

[A20A1]

It would sound like a motorcycle... (Harley)
You would hear the individual cylinders firing.

You wouldn't get any assistance from one cylinder creating vacuum for the other cylinder since the pipes don't merge thru/into one.