I have been smashing around my jdm 4-1 replica for 2years now, it's pretty much dead now and the car needs a new header. Here in Greece there are no decent shops to build me a custom header, So i decided to give it a shot myself i think it's worth it for the experience alone. I've settled on a 4-1 Setup that's a given. I've done my share of studying on the subject, There are two things that i havent cleared in my head out since i havent found out a documentation about it. First is Cylinder pairing in the collector, Firing in a rotational order is the only logical way i can see, but then i see headers like RMF drag and some ancient Mugen 4-1's that fire in an X-Pattern and i can't wrap my head around it what's the purpose of that ? Secondly i haven't found any Solid info about Stepping Primaries, i know some people really did their R&D around it and i dont want to disrespect their efforts trying to benefit from them through a forum. I do understand that the steps in the primaries help scavenging by accelerating gas since it moves from a high pressure area to a Lower one, But how does that affect Primary tube length ? My Logic assumes it should be longer than it should have been if it was a straight shot..Is my thinking right or am i really lost here ?

So enough with these theoritical stuff and down to my calculations.
I'm trying to focus my powerband between 6k-9k.
My math work according to fueling's formulas gave me a primary length of approximately 25.5 Inches and 1.57 ID.
According to Bells formula i got an approximate primary length of 23 Inches and 1.67 ID

I assume Bells formula is far more accurate since it takes more variables in consideration. But the Length seems too short on Paper. I Don't have access to any OTS header to measure their dimensions to see if i am even on the right track as far as length is concerned i Got a Blueprint from Burns for my specific application but i have my doubts after researching further on the matter.

Does 23-25 Inch length sound right for a B18C Focusing on 6-9k ? Stepped or not ? If anyone is willing to help in anyway i'd really appreciate it.
Thanks a lot

 

Dimitri, geia sou! Xeretismate kai kali tixi me to project xtapodi. Tha sou ta po sta agglika gia na min exoun aformi na poun malakies oi malakes xaxa

Traslation: Dimitri hello. Greetings and good luck with your header project. I am going to tell you in english in order not to give a reason for the haters to hate, lol

Yes, you are about right with your calculations. So in theory

We have :

engine displacement, exhaust valve diameter and exhaust valve lift.

We calculate curtain area = pi (3.14) x valve diameter x lift

And to calculate runner diameter

Area = pi x r^2

r= square root (area/pi)

Diameter= 2 x square root (1.901/3.14) =1.556167 inches

So yes, your calculations are correct and that could work, I mean it would make some kind of power.. but overall your length is too short, what I mean is that you need to make it longer based on Honda Bseries R an D that shows that the engine happier with longer length/


I am going to share with you some of my 1.8 Liter VTEC Bseries testing to get an idea why I think it is too short.

My base engine was a b18c1 with some aftermarket cams.

Test 1 with header AAA and CAMS AAA

Exhaust Runner Diameter: 1.595 inches
Exhaust Runner Length: 34 Inches

Exhaust Cam Lift : 0.428 inches
Exhaust Cam Duration at 0.050 : 236

Peak HP: 174 HP at 7500 RPM
Average Tq: 131
Peal TQ: 149 at 5500 RPM


Test 2: Header changed to header BBB and CAMS STAYED AAA

Exhaust Runner Diameter: 1.650 inches
Exhaust Runner Length: 34 Inches

Exhaust Cam Lift : 0.428 inches
Exhaust Cam Duration at 0.050 : 236

Peak HP: 181 HP at 7500 RPM
Average Tq: 136
Peak TQ: 144 at 5500 RPM


Test 3: NEW CAMS BBB and HEADER STAYS BBB

Exhaust Runner Diameter: 1.650 inches
Exhaust Runner Length: 34 Inches

Exhaust Cam Lift : 0.458 inches
Exhaust Cam Duration at 0.050 : 236

Best HP: 189 HP at 7500 RPM
Average Tq: 133
Peal TQ: 147 at 5500 RPM


Test 4: HEADER CCC spec, cams BBB spec

Exhaust Runner Diameter: 1.675 inches
Exhaust Runner Length: 31 Inches

Exhaust Cam Lift : 0.458 inches
Exhaust Cam Duration at 0.050 : 236

Best HP: 194 HP at 7500 RPM
Average Tq: 137
Peal TQ: 146 at 5500 RPM



So my advice is, if you are going to just give it one shot, I would go with 31 inches for runner length.


Your exhaust cam matters, you intake cam matters, your centerlines matter, etc etc

 

Niko efxaristo poli gia tis plirofories ! So here is the thing my engine gets MaxHp at 9100 with JDM 4-1 Replica and 9"inch Runner IM. My exhaust cam opens at 61* BBDC and duration is 263@1mm. Since i Shift at 9100 i calculated the primaries length for maxhp at 8500. Here are the measurements that i was provided with that did seem a bit off for a B18C running 12.7:1.

1step -> 203mm@1.625
2step -> 203mm@1.750
3step -> 203mm@1.875
2.5" Collector Choke Flaring to 2.75

How does this sound ? I ( without any experience just based on my research ) think it's gonna want to rev to the moon.

 

Randy (RMF) liked 26" long tubes (correct me if I am wrong, going off my memory of a convo I had with Randy years ago), this with a 3-4" collector gets you to 29-30".

Tip from Randy: an easy way to measure curved pipe length is to use a U.S. dollar which is about 6" long. So RMF headers were a little over 4-dollar lengths long.

 

Thanks a lot Rocket really appreciated. When i was crunching runners i found that the numbers that looked most appealing on paper was using Fueling's Formula to calculate the length and then using that Length in Bell's Formula for calculating diameter.

L=120V/N
L= Length
V= Gas Speed approx. 17000ft/sec
N= Target RPM

L=(120*17000)/8000= 25.5inches Length

ID=sqrt(cc/(L+3)x25) x2.1=sqrt(0.64)x2.1= 1.68" ID

I think that's my best bet so far.

 

years ago Randy did say
he liked 30-32inches give or take an inch
depending on motor/use etc and engine compartment

 

you could also try pipemax ... usually most of the calculators would give 2 diff number styles

one would be ... a slightly bigger dia. primary but shorter
the other.. slightly smaller but longer..

odd that theyre almost both exact opposite of one another..
thats based on most of the online softwares we can get
at the end of the day.. dyno and trials would still fine tune it

have fun on this project man! keep us posted

 

thanks for the info and the heads up man i dont got pipemax unfortunatly..I Got Engine analyzer Pro which actually Sucks big time for exhaust Simulation.

 

thats fine... build ur stuff.. i think the 30-32inches is a safe bet...

dont get too caught up in numbers...

example
we had a 85x89 motor.. running the conventional 30inch total header
switched to an experimental header with 45inches length
it made more power and took it to 9,400peak and 9.800rpm bfor it started to lose power

.... IMO those length suppose to be "wrong" but dyno showed different?

 

true..i think i've seen a header like that in the Race Header thread, were the primaries 2" where they met the collector ?

 

cool ... not sure it was ever posted there

but yeah.. somewhat close to that as u asked

the pipe used to make the collector was 2" to give "volume" maintaining the same overall length

 

thanks alot that clears up a lot in my head

 

1 5/8 stepped to 1 7/8 with 2 1/8 collector choke.

 

Thanks a lot rocket I've calculated 2.3 Inches for the collector choke, So seems i am on the right path. Anyone knows where i can get a 1 7/8 to 2 1/8 - 2 2/8 Collector ?

Thanks a lot everyone you really helped me clear my head, it was seriously eating me inside out !

 

http://www.spdexhaust.com/

 

Given all the information. You're best bet is to buy a good 4-2-1 header from Ebay for $300 -$350.

The manufacturers overseas don't have the ability to make a good 4-1 collector .

http://www.ebay.com/itm/PLM-Tri-Y-Standard-Tube-Exhaust-Header-Integra-Civic-Si-DOHC-B18C-B16A-B20B-GSR-/300745168500?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AHonda&hash=item4605cf1674&vxp=mtr
http://www.ebay.com/itm/Toda-Style-B-Series-Header-Honda-Acura-B16-B18-/111064096476?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AHonda&hash=item19dbef9edc&vxp=mtr

 

http://www.turbo-flanges.com/product...products_id=38

 

Rocket i know but its approx 350 without shipping 420-450 with shipping to Greece..and if i get customs check its another 100$$ for Import Taxes Can you believe it ?

 

There may be freight forwarders you can use.

 

is this a street car? why do you want the powerband so high, thats practically undriveable on the street, you want power much lower in the rpm band for dribeability

 

While it does see the streets daily i dont consider it my street car, My wife has a peugeot 207 for that matter. When hitting the track i wanna stay above 6k Permanently below 6k no matter what setup it wont be as fast imho.

 

My collector just arrived last week. Here are some cell pictures









what do you guys think ? the collector is 1.88 to 2.5" and the cones are 2.5 to 2" ( the cones are gonna get trimmed on the small side to about 2.20") i know it's not a true merge collector but i couldnt justify the cost at this point. Couple of questions if someone can help. Should i use the cones in the first Pictures to create a choke ? or run it straight 2.5 ? Has anyone use EAP 3.9 for engine simulation ? I got the new version now, got my full engine specs in there and the header dimensions i've decided on work wonderful.

 

Looks killer, I would use a choke and have long diffuser/megaphone cone after it.

 

I know this is almost a 1 year thread but car has been off duty for almost 10 months and i've been quite busy with life in general. At last i was able to move forward with this project with the help of my friends. Anyway i ended up with the primaries at 22" long 99% equal length and 1.88" OD. Calculated with a 7-9k rpm powerband in mind. The collector is 7" long, 2.5" Outlet with a 2.25" Choke approx. Here is a Progress pic fully welded minus the collector. More pics to follow. I'd like to hear your thoughts on length,diameter,Collector Choice,Rooting etc.

 

I love stuff like this, really looking forward to before and after dynos.