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

[A20A1]

PLEASE TAKE A LOOK AT THE HEADER FAQ THREAD
IF YOU WANT TO BUY INSTEAD OF MAKE YOUR OWN HEADER (CLICK HERE)

1) Choosing Type of Header; 4-1 or 4-2-1
Plan where you want to make power and what kind of driving you will be doing.
Long pipes move the power down in the RPM, Short pipes move the power up in the RPM
- 4-2-1 offers more usable/broader rpm range and often more torque through cylinder pairing.
- 4-1 have longer primaries in most cases moving torque up in the powerband
- Long Tubed 4-2-1 Does the same as a 4-1 but offers the advantage of cylinder pairing.

2) Designing The Header

The stock EFI 4-2-1 manifold and pipe is about 26" long.
The stock Carb manifold is about 10" - 13" long.

4-2-1 Sequential Pairing of cylinders when you have longer primaries like those found on 4-1 headers
4-2-1 Non-Sequential Pairing cylinders then primaries are not as long

Here I did all the equations for you, using multiple sources.

NON-Sequential 360-DEGREE COLLECTOR 4-2-1 Header For A20A Accord
1) Short Tubed 4-2-1 Design
2) Cylinders 1+4 , 2+3 Paired
3) Small exhaust Diameter for Primaries and Secondaries
4) Long Secondary length after header.


(4 pipe) 1.375" diameter Primaries  18.25" long
(2 pipe) 1.625" diameter Secondaries  12.25" long
Header Length 30.50" long
(1 pipe) 2.000" Secondary pipe 30.50" long

Total lenght 61"

Sequential 180-DEGREE COLLECTOR 4-2-1 Header For A20A Accord
1) Long Tubed 4-2-1 Design
2) Cylinders 1+3 , 2+4 Paired
3) Large exhaust Diameter for Primaries and Secondaries
4) Short Secondary length after header.


(4 pipe) 1.500" diameter Primaries  36.50" long
(2 pipe) 1.625" diameter Secondaries  12.25" long
Header Length 48.75" long
(1 pipe) 2.000" Secondary pipe 12.25" long

Total Length 61"

Now the muffler after the 61" will be the first LARGE change in cross-sectional area / volume.
This is where return pulse will be created. The muffler must be chambered to allow for the
cross-sectional change as well as flow the appopriate amount of CFM.

In this Case a Hooker Aero Chamber good for 200 HP or 441 CFM with 2.50" inlet and outlet diameters.
You can argue about reducing the 2.50" outlet of the header to 2.25" even 2.00",
but as long as the pipe flows the CFM I need I don't see it hurting much.

The Bit after the muffler in this image is a 2.50" SMSP catalytic convertor.

Bells Formula With Some Minor Tweaks.

Using EVO of 190    ( Exhaust Valve Opening )

1)   HPL = ( ( 850 x ( 360 - EVO ) ) / RPM ) - 3
2)   HPL = ( ( 850 x ( 360 - 190 ) ) / RPM ) - 3
3)   HPL = ( ( 850 x ( 170 ) ) / RPM ) - 3
3)   HPL = ( ( 850 x 170 ) / RPM ) - 3
4)   HPL = ( ( 144,500 ) / RPM ) - 3
5)   HPL = ( 144,500 / RPM ) - 3

Using RPM 6800
6)   HPL = ( 144,500 / 6800 ) - 3
7)   HPL = ( 21.25 ) - 3
8)   HPL = 21.25 - 3
9)   HPL = 18.25
HPL = 18.25"
EPL = 21.25"

Using RPM 6500
6)   HPL = ( 144,500 / 6500 ) - 3
7)   HPL = ( 22.23076923077 ) - 3
8)   HPL = 22.23076923077 - 3
9)   HPL = 19.23076923077
HPL = 19.25"
EPL = 22.25"

Using RPM 5500
6)   HPL = ( 144,500 / 5500 ) - 3
7)   HPL = ( 26.27272727273 ) - 3
8)   HPL = 26.27272727273 - 3
9)   HPL = 23.27272727273
HPL = 23.25"
EPL = 26.25"

Using RPM 3600
6)   HPL = ( 144,500 / 3600 ) - 3
7)   HPL = ( 40.13888888889 ) - 3
8)   HPL = 40.13888888889 - 3
9)   HPL = 37.13888888889
HPL = 37"
EPL = 40"

EPL = (HPL + 3)

USING EPL = 26.25 ( Exhaust Pipe Lenght )

CID Equation
1)   HPD = ( ( SCID x 16.38 ) / ( EPL x 25 ) ) x 2.1
2)   HPD = ( ( 29.75 x 16.38 ) / ( EPL x 25 ) ) x 2.1
2)   HPD = ( ( 487.305 ) / ( EPL x 25 ) ) x 2.1
3)   HPD = ( 487.305 / ( 26.25 x 25 ) ) x 2.1
4)   HPD = ( 487.305 / ( 656.25 ) ) x 2.1
5)   HPD = ( 487.305 / 656.25 ) x 2.1
6)   HPD = ( 0.74256 ) x 2.1
7)   HPD = 0.74256 x 2.1
8)   HPD = 0.74256 x 2.1
9)   HPD = 1.559376
HPD = 1.50"

1)   HPD = ( ( SCID ) / ( EPL x 25 ) ) ) x 2.1
2)   HPD = ( 487.305 / 765.625 ) x 2.1
3)   HPD = ( 0.63648 ) x 2.1
4)   HPD = 0.63648 x 2.1
5)   HPD = 1.336608
HPD = 1.375"

CC Equation
1)   HPD = ( ( SCC ) / ( EPL x 25 ) ) ) x 2.1
2)   HPD = ( 488.750 / 656.25 ) x 2.1
3)   HPD = ( 488.750 / 656.25 ) x 2.1
4)   HPD = 0.744761904762 x 2.1
5)   HPD = 1.564
HPD = 1.50"

1)   HPD = ( ( SCC ) / ( EPL x 25 ) ) ) x 2.1
2)   HPD = ( 488.750 / 765.625 ) x 2.1
3)   HPD = ( 0.638367346939 ) x 2.1
4)   HPD = 0.638367346939 x 2.1
5)   HPD = 1.340571428572
HPD = 1.375"

--------------------------
119 cid
SCID  =  29.75
1955 cc
SCC = 488.750

Other Formula

40.592” (7500 RPM 210 EXH DURATION)
42" - Out of Tune
- 43"
--- 44"
----- 46" (6500 RPM 210 EXH DURATION)
------- 48" (AVERAGE 210 EXH DURATION)
--------- 50"
----------- 51" (7500 RPM 253.5 EXH DURATION)
--------- 52"
------- 54"
----- 56"
--- 58" (5500 RPM 210 EXH DURATION)
- 59"
--- 60" (AVERAGE 253.5 EXH DURATION) (6500 RPM 253.5 EXH DURATION) (7500 RPM 288 EXH DURATION)
----- 62"
------- 64"
--------- 66"
----------- 67"
--------- 68"
------- 70" (AVERAGE 288 EXH DURATION) (6500 RPM 288 EXH DURATION)
----- 72" (5500 RPM 253.5 EXH DURATION)
--- 74"
- 75"
76" - Out of Tune
83.78” (5500 RPM 288 EXH DURATION)


Remember the engine moves in and out of tune
throughout the RPM range so I did averages
instead of going strickly based one setting.

The "OUT OF TUNE" I added to set limits based on averages.
Then I did calculations @ different rpms @ different exhaust durations.
If you look how the 288 @ 5500 rpm droped below the out of tune...
I'm figuring this is because such a high duration was not ment for
such a low rpm.
So I assume building a header with that length would do more harm
then good. Or not.

Comparison Between Chart and Bells Formula Figures.

EPL ( Exhaust Pipe Lenght )
EVO ( Exhaust Valve Opening )

Optimum EPL using EVO of 190 and RPM range of 3600-6800 is  30.625" with optimum diameter of 1.375"

When trying to find the collector outlet diameter, use about a 20% larger pipe than the primary header pipe diameter on 4cylinder motors. 

1-3/8" _or_ 1.375" + ( 1.375 x 0.20 ) = 1.65" which is close to 1.75" collector diameter
1-5/8" _or_ 1.625" + ( 1.625 x 0.20 ) = 1.95" which is close to 2.00" collector diameter
1-3/4" _or_ 1.750" + ( 1.750 x 0.20 ) = 2.10" which is close to 2.00" collector diameter
2.000" _or_ 2.000" + ( 2.000 x 0.20 ) = 2.40" which is close to 2.25" collector diameter

On V8's use collector equations as follows.

1.375" x 1.750" ~ 2.50 Collector
1.625" x 1.750" ~ 2.75 Collector

Header Plus Secondary Pipe Lenght      |                        Header Lengths
51.75" (5500 RPM 190.00 EXH DURATION) EPL = 25.875" (using Other Formula) vs. EPL = 26.25" (using Bell's Formula)
58.00" (5500 RPM 210.00 EXH DURATION) EPL = 29.000" (using Other Formula) vs. EPL = 26.25" (using Bell's Formula)
72.00" (5500 RPM 253.50 EXH DURATION)
83.75” (5500 RPM 288.00 EXH DURATION)

40.25" (6500 RPM 190.00 EXH DURATION) EPL = 20.125" (using Other Formula) vs. EPL = 22.25" (using Bell's Formula)
46.00" (6500 RPM 210.00 EXH DURATION) EPL = 23.000" (using Other Formula) vs. EPL = 22.25" (using Bell's Formula)
60.00" (6500 RPM 253.50 EXH DURATION)
70.00" (6500 RPM 288.00 EXH DURATION)

Header
Primary lenght,
      lenght of 4 and 2 pipes on 4-2-1
      or lenght of 4 primaries on 4-1.
Primaries,
      length of 4-2 pipes.
Secondaries,
      length of 2-1 pipes.
Collector length,
      length of pipe after 4-1 primaries merge.
Exhaust
Secondary length,
      length of pipe after primaries but sometimes including
      part or all of collector length. Secondary length is said
      to be important in making torque, even more so than
      primary length.
Total length,
      Lenght of Primary and Secondary together

Primary , Secondary
      Lenghts    |       RPM
________________________________
28.375 - 26.000  |  6500 - 7000
30.000 - 28.375  |  6000 - 6500
33.625 - 30.000  |  5500 - 6000
36.000 - 33.625  |  5000 - 5500

The basic ideas for building a header are:

1) Broaden power over a wide power band, not
just tune for high narrow peak power ( HP / Toruque )

2) Maintain exhaust velocity (scavenging vacuum)

3) Lower Backpressure as much as possible

TIPS:

Dont port your exhaust port to match the header flange,
a 1mm larger flange port all the way around will allow
the exhaust port on the head to act as an anti-reversion dam.

AR or anti-reversion is any area inside a pipe that allows
flow in one direction while inhibiting blow in the reverse direction.

AR is mostly used to address reversion at low engine speeds
where long duration cams cause the air/fuel mixture to get contaminated
by reversion.


Another Formula :
L = (850 X ED) / RPM 
L = length of primary pipes in inches
ED = 180 degrees + number of degrees exhaust valve opens BBDC
RPM = engine RPM at peak torque
Secondary Length approximately 2/3 Primary Length

Mine


Justins

[PhydeauX]

For some reason I thought I had already posted this here, but I guess I didn't. He has a chart for calculating the proper lengths based on cam timing and rpm.

http://www.billzilla.org/engexhaust.htm

Just to be sure you read that right. That chart doesn't tell you the length of the primaries, but of the whole exhaust system. A 4 - 1 should be half the calculated length. Its probalby not going to be practicle to have the exhaust that short on a 3g so just hook it up to a regualr cat back.

andy

[A20A1]

------------------------------
LINKS
Here are some sites to look at when shopping for materials... I know places like burns offers discounts if you order in bulk.
BURNS STAINLESS
PITSTOP USA
STAINLESS WORKS
RRE
TRC
CHASSIE WORKS
HEADERS BY ED
JC WHITNEY
S&S
BY REQUEST:
PITSTOP USA
Product ID: SCHSO63041
Description: SCHOENFELD SLIP-ON 4 TUBE COLLECTOR - SLIPS OVER 1-5/8" DIAMETER TUBING - 3" COLLECTOR DIAMETER - #SCHSO63041
Quantity: 1
>Handling Charge: $1.00
>Order Sub Total: $29.95
>UPS 2nd Day Air : $25.61
>Grand Total: $56.56

SUMMIT
Product ID: HOK-12540
Description: J-Bends 1-5/8" Mild Steel
Quantity: 6
Charges for your order include the following:
Parts: $77.70
Handling: $8.45
2nd day air shipping charges: $25.60
Current charges to your credit card are: $111.75
http://www.jcwhitney.com/webapp/wcs/...X&appId=391415
http://www.jegs.com/cgi-bin/ncommerc...61&cgrfnbr=841
http://www.ssheaders.com/JBends.htm

Basically this stuff is really complex and takes lots trial and error to get it right. I have been doing a lot of research on tube lengths, etc and still it's something that is pretty mush trial and error and dyno time, which I hope to be doing a lot of here soon.

It's good too see you were just as serious about getting a header made for your motor.
A few values I considered:
Cam profiles, Diameter, Length, RPM, CID... but even thene there are more variables to consider... it's all about timing/tuning the negative returning wave... the collector plays a role too chaniging the wave from short to long broadening the power range. When I made the chart in the header FAQ I did a lot of averaging to help get ball park figures... I never thought to question the primary and secondary 50%/50% length logic though.
In the end I didn't have much money to do what I wanted.
I noticed burns stainless has a build sheet... but some of the values they ask for I don't have. Right now I am interested in venturies cause since I've seen drag headers with 2" chokes/venturies and even if you didn't understand exhaust systems you know those cars wouldn't add restrictions if it wasn't going to help.
My understanding of any 4 cylinder pairing in a 4-2-1 was that the benifit came from the pairing of cylinders into two pipes before the collector... this way the scavenging wave returns back to the original cylinder that made the positive wave but while in the secondaries the negative wave also effects the cylinder its paired with. The term in one of the books I have was that pairing 4-1 and 3-2 evenly spaces the pulses and gives you "Full Resonace"... in a 4-2-1-3 firing order.
Same with a 2 cylinder motor.
I suppose the 4-2 and 3-1 design would be simmilar yet the pulses would be closer...
Anyways nice header, I'm looking forward to the dyno... in my PM I did't realize what you header looked like or if you had it hooked up to the exhaust... put a muffler or res on it quick. At least I'm not the only one that knows what i sounds like though.
Not the new one, no

What size pipes did you use for primaries and for secondaries? PM me if you don't want to post it.

i think we should do a little competition and see who can make the best header on 3geez...
no matter, the best on one car won't be the best on another, so it's not really something that can be scored

I dunno I tired to get a wide range when I tuned my header even though it might not seem like it... I would like to make a new one and have someone with a stock cam try it out.

I found some flux cored stainless wire... http://www.brazing.com/products/Weld...red_stainless/
I have no problem getting access to Co2...

[shepherd79]

nice work mike.

[wprocomp]

man that collecter is frakin huge mike!...I am looking at it wrong or does the downpipe angle to the left?
I wouild like to see an comparison between yours and a pacesetter....as big as it is I would assume yours would outflow it greatly...hmm..
BTW: what paint did you use? I used that engine paint from auto-zone and it burned right off until I found out that you are supposed to use a sealing primer to keep it on there...if you want it to stay you need to use that

[2old_honda]

Man I cant believe I havent seen this thread. Anyway, Mike good work! Very nice! We need more pics.

[Don87LX]

THats be-yu-ti-ful work mike. You should get great flow with the exterior welds (even if they are supposed to be interior), hope it all works out. YOu could get rid of the engine shaking the welds loose by solid mounting your engine ;-) If you like a numb ass...

[Mike's89AccordLX]

Get some sound clips of that baby Mike!!! Great job I have been waiting for a long time to see you do this and I'm amazed. Keep up the great work!

[markmdz89hatch]

Hey Mike, is there any way that you might be able to get hp numbers from that header? I know you have a ton of other perf. add-ons too, but just to see the gain from you header as opposed to stock.
Also, could you possibly snap a pic of the underside of the car. Just basically from the ground in the front of the car, just so I can see how low that header hangs, to see if I'll have any clearance issues with my ultra-low suspension.
....and as always, SWEET!

done!
I'd obviously pay for shipping too, and toss a few extra bux your way for the trouble.

actually, if you have a diagram, with dimensions, of the header/head flange that you need, e-mail it to me. I have a friend of the family that works at an old machine/tooling shop. He might be able to make this for you.
Just let me know if you want me to look into anything for you.

[120hpcanadian]

i don't know if this has been posted here already , but when welding cast iron remember to let the weld cool very gradually even putting it next to a woodstove wouldn't be a bad idea it will help stop cracks. and if your welding straight castiron to cast iron an arc welder will do the trick nicer then a mig. remember let the weld cool as slowly as possible.

[Robs89LXi]

Below is an email I sent to Tom Fowler of OPM AutoSports. Anyone interested? Be sure to check the web address listed in my note.
.................................................. ....
Date: Thu, 12 Feb 2004 12:19:09 -0500 (Eastern Standard Time)
From: "Tom Fowler" <[email protected]> Add to Address Book
To: [email protected]
Subject: Re: Headers for 86-89 Accord LXi
We have not made that header in a few years due to lack of interest. I could make another run, but it would take 7-10 orders. It's a custom race unit like our other Honda headers, hand-made 4-1 race header open pipe does not bolt to cat.
Tom Fowler
OPM AutoSports
248 Castleberry Industrial Dr
Cumming, GA 30040
[email protected]
-------Original Message-------
From: The Jadusinghs of Houston
Date: 02/02/04 14:14:43
To: [email protected]
Subject: Headers for 86-89 Accord LXi
Hello, Tom. Just spoke with one of your sales reps, and she directed me to you for this. I am interested in finding out more about a part you list on your webpage. It is the "Full-Race Exhaust Header" for an "86-88 Honda Accord LXi"
http://www.opmautosports.com/produc..._accordlxi.html
Would you please send me some more information on this product (what brand, availibility, quantity, associated flanges/gaskets, performance specs, etc.) as well as any pictures you may have of it? I am a member of an Accord club, and a group buy may be possible if it fits what we are looking for.
Thanks in advance.
Rob.

Oops. Try this.
OPM MOTORSPORTS
Everytime I try to post the link, it tries to shorten it, and omits parts of it, so here it is in two pieces. I guess you will have to type it in your address line manually.
http://www.opmautosports.com/product...accordlxi.html
Hope it works this time.
Okay, now I'm getting pissed! What kinda POS forum is this?
ACCORD LXI RACE HEADER
Okay, I see that now. Why did it not do it the first time? Anyway, he says it's a 4-1 in his reply, so I'm not sure. I've dropped him another note already, asking him for more info, so I'll pass that along as soon as I get it.

[Justanothermike]

still looking for someone to dyno your header? we're gonna dyno the car again and we could probably fit in a header comparo while we're doing it. The only concern i could think of is install difficulty with the one piece header cuz we'll be on the clock on the dyno and the car still has AC and PS so lemme know

[Justin86]

Well some people have been asking me about building one so I finally got it done. I'm gonna be working on exhaust and intakes also here soon. I'm gonna been hooking up NXRacer with these new parts to get dynoed march 5, but so far just driving around I have been impressed.

I went with that flange because it was cheapest on and less chance of warping. The specs I'm going to keep under raps. Not sure on a price yet but I'm looking at around maybe $200 uncoated, maybe more or less I'm still looking at some options.

[AccordEpicenter]

looks good but id use a better flange. Good work though

[Robs89LXi]

Looking real nice. I agree about the flange though; a single unit would give more support. Any specs (tubing diameter, exit size, etc.?). I'll be looking for one eventually.

[2drSE-i]

i agree with the flange, but shit man nice job! how much u thinkin about charging for those?

well its definately not the common after market header, he made it himself.

[Accordtheory]

Interesting. Does the 3g have a different firing order than the integra/civic? I always see cyl 1 paired with 3, and 2 paired with 4. I noticed you didn't do that. Also, how did you calculate what length to make the various sections of piping? (the sections look longer than a common aftermarket 4/2/1 header) I'm curious to hear the dyno results..

[AccordEpicenter]

Interesting. Does the 3g have a different firing order than the integra/civic? I always see cyl 1 paired with 3, and 2 paired with 4. I noticed you didn't do that[/U]

Thats a new one on me... ive never seen that. I think if you had a 3/8ths steel one piece weld flange youd be better off... betcha weirRacing might be able to make them...

[SteveDX89]

Interesting. Does the 3g have a different firing order than the integra/civic? I always see cyl 1 paired with 3, and 2 paired with 4. I noticed you didn't do that. Also, how did you calculate what length to make the various sections of piping? (the sections look longer than a common aftermarket 4/2/1 header) I'm curious to hear the dyno results..

Look closer. Cylinders 1 and 4 are together and 2 and 3 are together. It's like that on just about all Honda 4-2-1 headers.

[Strugglebucket]

yeah, A20 fires 1-3-4-2 just like other hondas.

justin that's a neat design. with those long primaries i would think performance wise it would be somewhere in-between a 4-1 and the normal 4-2-1 designs you usaually see.

[Justin86]

well I believe they are all the same 4-2-1-3 firing, but with most basic aftermarket headers they have 4&1, 2&3 together. Thats what I ran with but looking at some race header designs they have 3&1, 4&2 together. It makes sense to have the pulses seperate, but these new designs that are selling for $800+ and make the most overall power they use 3&1, 4&2 together. Also I did look at a bunch of header design programs and one that involve cam profiles. From what I was getting should be the best and what lenghts I see on products don't add up right.
With the average product like DC they follow those basic designs with the 4-2-1 like having the primary and the 2nd the same length. But the length are way to short and are best suited for highlift/duriation, high reving car. Then with the $800 race headers they use tube lengths longer then what the design programs say, but they still make better top end and midrange power then you would think. Basically this stuff is really complex and takes lots trial and error to get it right. I have been doing a lot of research on tube lengths, etc and still it's something that is pretty mush trial and error and dyno time, which I hope to be doing a lot of here soon.

Yea I have 3/8" flanges right now, but there is a local shop with a CNC plasma that I got them done at. As it being one peice flange or not, I'll do what ever I'm asked of. I did them seperate to save money and I heard it wil help prevent warpage and leaking....

justin that's a neat design. with those long primaries i would think performance wise it would be somewhere in-between a 4-1 and the normal 4-2-1 designs you usaually see.

Yea that is what I belive is behind them. If you guys have seen the new honda tuning on page 48 there is an example of these $800 headers. They don't follow the typical header designs you see on the streets, this is stuff used by racing teams that is now being applyed for the rest of us. They have the all the benefits of a 4-1 and 4-2-1 while now of the side effects.

yea I have flex pipe farther down on it

[mykwikcoupe]

hey man just a thought but make one for the jdm b20a for me so i dont have to modify one. id pay the same price maybe a little more since there is a little difference. ill send you a gasket to make the flange and just add those pipes to this flange. sounds easy enough huh. let me know. mike

[Justin86]

hey man just a thought but make one for the jdm b20a for me so i dont have to modify one. id pay the same price maybe a little more since there is a little difference. ill send you a gasket to make the flange and just add those pipes to this flange. sounds easy enough huh. let me know. mike

yea I could prob do that, would need a pic and some measurments to make sure it would fit.

[895spdforfree]

good job man i was thinking about buying a pacesetter withing a month or 2 but your header would be much better..

[b20a86lude]

holy damn thats nice i like that header it remindsme of a mugen header that they made back then for u accord guys hey how much are u sellin these headrs for u cam make a ass load of cash by sellin these here and sellin them on prleude power .com in the 2nd gen forum its real nice work i really like that header u should consider makin them for us b20a guys id def buy