header/exhaust diameter

[blackk]

Alright, I don't know much about the exhaust system and planning to upgrade. Been researching on various forums and 2.25/2.5" have been mentioned alot for the b16a2 and now i'm hella confused. What's the best/good size for b16a2 and does all the header, bpipe and axleback have to be the same size in diameter? Or could i just get it somewhat modified.

much appreciated.

[Jarkz]

2.0 - 2.25... the more equal length though out the exhaust will give the best results

So if your get a header with a 2.25 collector keep it 2.25 from the header to the tip.

2.0 for low rev torque.

2.25 for mid to top end.

[blackk]

thanks buddy, is there a downside to having 2.5". I'm trying to get the Mugen tiwnloop catback to hook up with the 5zigen header but ain't sure whats the diameter size to it. Someone let me know? Also what kind of cat do i need?

[EK1.6LCIV]

downside in a 2.5" on a basic 1600cc inline four is the cabin and exterior drone that will occur

[blackk]

Got a 2" collector header.. whats the pros/cons on having that on a b16a2 with 2.25" bpipe then 2.5" axleback? Or would 2" > 2" > 2.5" be better? Give me some ideas guys for best results!

[SHU-ES1]

having a 1.6L engine, i'd say that 2-2.25" side header outlet size, piping all the way through would be your best bet. going to 2.5" might give you better top end power, but you would almost definately lose some low end torque as a result.

it depends what your intentions are. if its just you're daily driving, going for something in between 2 and 2.25" would be suitable if you want that extra bit of punch off at the lights etc. and having mandrel bends, and straight through mufflers would be good. depending on the quality of your mufflers, and their size will depend on how loud your exhaust will be.

as EK1.6 said, you'd probably get a annoying drone as you cruise with a 2.5" exhaust. if you planning on staying in the higher rev range all the time (track racing), then maybe a 2.5" will suit but that's up to you. either way, tbh, an exhaust doesn't do that much for a standard engine but that's just my opinion. so don't go blowing big bucks on a mediocre upgrade to your b16.

my bets on a 2.25", good luck with it!

[bboyccw]

I have faced this same problem before in the past. I've tried a few combinations and found this measurements suits me the best.

1.6L (stock or lightly modded) - 2.25/2.3"
1.6L & 1.8L (heavy mods) - 2.5"
1.8L stock - 2.25/2.3"

Its important to keep the diameter all the same from the catback all the way to the inlet of your muffler so as not to 'confuse'/restrict the flow.

The type of extractor you are using in important too. The 4-2-1 system is great for mid-range torque. The 4-1 system is great for high end torque (track or curcuit driving) but compensates the mid-range power. You may find that your car may act sluggish with the 4-1 system.
So for a stock B16A and u are using the 4-1 system i think the best diameter for u is 2.25"/2.3" so u dont loose pressure at the end of your system (backpressure).
If your B16A is heavily modded (high cams etc..) then 2.5" is fine to use with the 4-2-1 system. You will have both mid-range torque as well as high-end power from vtec all the way to the redline.

I guess it comes down to the specs of your engine and what sort of torque range u are going after. Hope this helps!

[dougie_504]

I'd go 2.25" or as close to. 2" is fine but 2.5" will give you cabin drone which will result in friggin' headaches and loss of torque (which is minimal on a B16A2 to begin with).

So go 2" or 2.25"

Keep it the same size, or start smaller like 2" and have a 2.25" cat-back/muffler but don't go from large to small (EG 2.25" header and 2" cat-back).

[blackk]

Thanks guys for the info, very helpful. Well I've got a 5zigen header that I thought to be 2.25" but i measured the collector size from the the inside and it came out to be 2". But I'm still considering on installing it or find another one with 2.25", was thinking of sourcing a 2.25" mandrel bend bpipe with a Mugen twinloop axleback which i was told it has a 2.5" collector. So its going from header 2" > 2.25" > 2.5" unless i get the bpipe 2" as well if thats any better.

Does the bpipe make a huge difference with performance?
and I'm hoping that I measured the header wrong, is there a proper way? from inside the hole it measured to be 40.7mm.

[dougie_504]

From one side to the other of the end of the header where it connects to the catalytic converter (the "1" in the "4-2-1" design) is the "size" of the header.

40.7mm isn't 2", that's about 1.75" which would be smaller/same size as your stock one. One inch is 2.54cm so 2" would be 5.08cm or 50.8mm.

I recommend not going over 2.5", even at the back-pipe, as you'll lose a little of your low-end power which is already quite minimal on the B16A2. 2.25" should be a good size for low and high end ranges combined.

[blackk]

From one side to the other of the end of the header where it connects to the catalytic converter (the "1" in the "4-2-1" design) is the "size" of the header.



You mean i measure the length of the pipe? or the diameter of the inner hole. I'm confused, i hope i measured it incorrectly

[blackk]

Well i remeasured it again from the inner diameter of the hole where it meets the cat converter and its 2".

[bennjamin]

imo


the cat , and cat-back system should be the same size of your header collector.

[JasonGilholme]

60 mm

[blackk]

whats 60mm?

[dougie_504]

2.36"

[JasonGilholme]

60mm is what most aftermarket JDM & other cat backs use. Its also the diameter of most popular header collectors.

[blackk]

alright, thanks guys.

very newb question but how do u measure the collector size? do u measure the hole of the pipe (inner diameter) or the outer diameter of the pipe.

[JasonGilholme]

ID. Inner Diameter.

[blackk]

someone on honda-tech mentioned outer diameter... i'm confused.


Outer diameter on tubing. Inner diameter on cats and mufflers.

--
Tom

[dougie_504]

He's a noob. The thickness of the header pipe has nothing to do with the size of the actual exhaust outlet, only the inner diameter where the exhaust flows.

You could have steel 2" thick but then the header size wouldn't be 16cm or whatever, yeah?

So it's from one side of the hollow part to the other side :)

[CB7_OWNER]

Say i wack on a JDM ITR 4-1 header.. which has a 2.5 collector.. ideally wouldnt be keeping the same size piping for the rest of the system.. but being a stock b16. i dont see 2.5" reasonable. What would you recommend after the header? > 2.25 high flow cat > 2.25 catback

or jdm header > 2.5 high flow > 60mm cat back

or jdm header > 2.5 high flow > 2.25 catback

[JasonGilholme]

no point having a 2.5" collector if you have 2.25 piping.

Imagine drinking through a massive diameter straw that goes down to a tiny diameter just before your mouth. You can only drink as fast as what will go through the smallest section.

2.5 is good for the b16. Don't think of it as a 1600cc engine, think of it as a 2000 and size your exhaust to that.

[CB7_OWNER]

Im not really chasing power, im just after more drivability down in the lower revs.. cause the 1.6 really does lack down below.

[JasonGilholme]

2.25 exhaust won't do you any good, and neither will the 4-1 header. 4-2-1 improves mid range but doesn't really effect really low down. Thats just a bad thing about honda's + low capacity.

Good improvement if you go to the b18, but if you don't want to do that all i can suggest is a 4-2-1 header with a 2.5 inch exhaust. Nothing stopping you from putting a good 2.5 inch muffler or two in the system to bring down the dB.