New Project- custom header

[Ajax]

So in my quest for pump-gas-fed 200whp, I've finally moved on to customizing the exhaust.
This weekend I removed my old 5Zigen exhaust in favor of a BRM 2.5" stainless. This is mainly due to looks, and hopefully a better sound. The old exhaust was also a 2.5", so I shouldn't see any difference there. This is a street vehicle, so I included a high-flow catalytic converter. I've never been a supporter of going without a cat, as most evidence shows that there is little if any performance difference between high-flows and test pipes. Yes, they add expense, but its really not a bank breaker.


Yes, when the car was repainted, they did not completely mask the exhaust...

The BRM does not have this large canister resonator, so there is no hanger on the new exhaust either. This would not normally be a problem, except the last person to work on my exhaust did this:

That's the "exhaust bracket tube" that has been welded to the old catalytic converter. When the old exhaust was originally installed, it was jerry-rigged to go from the stock tubing to the larger cat and exhaust- they actually cut off the flanges and just welded things together; which was fine until I upgraded to the OBX header. Then, because I wanted the ability to bolt on and off, I had a mechanic weld a flange back on. Well this was the result. So I just ordered a new bracket for $40 shipped from Courtesy NIssan. Hopefully, this will take care of that problem.

I had fitment problems with this OBX crap, and even after I had worked to correct the problem it was still a b*tch to get out. But out it came- so long mediocrity!

Next I bolted up part of the BRM just to get it on and see how it will look- much better:

On to the header. After paying some money to Burns Stainless for their proprietary header design program recommendations, I contacted a company that does custom headers through a mock up kit:
Stainless Headers Mfg: http://www.stainlessheaders.com/index.aspx
They have some neat ideas, and looked like they could handle my project. Expensive? Yes, in comparison to OBX, but with the money I've spent on my engine, it made sense with my goals to spend the cash on a custom design. Plus, I get to look all cool in creating a thread like this, right?
So bolt up the flange (I supplied a gasket ordered through AMS for them to develop- anyone else deciding to build a custom header for the KA through Stainless can thank me for that)...

... and promptly forget to take more pictures with the aluminum elbows attached.
I need to purchase some 1.5" PVC tubing and wait on the "exhaust bracket tube" to finish mocking, but I figured this was a good start to document.

[TheBlaiant]

You should make some zoomies lol

[Ajax]

Then I'd have to paint the whole car flat black or rustoleum red. Another project... actually, that might be pretty BA- silvia front, chopped roof, on a coupe, lowered with hacked fenders to fit giant euro TAs.
But not this car. I'm super busy with non-car projects, so it might be weekend to weekend with this project. Hopefully, all will be mocked next weekend, then sent back to Stainless to weld up the finished piece and back to me before the end of May.

[xX RB Xx]

Im also doing the same thing as you, 200whp KA. Good luck to you SIR!

[Ajax]

Pump gas or no? I'm curious to find out more about your project- what kind of mods are you using?

[breadbox]

So what are you hoping this setup will do to your torque band?

I never got the whole concept of header design for different applications explained to me. Everyone one just says better flow and that's about as technical as most people get. This thread could be useful if we can lump some good theories in here.

Has anyone found any awesome articles on the subject?

[1KleenS13]

If your looking for 200 whp, you should make all those primaries collect at a turbo $.02

[95zenki man]

Wait so what was wrong with the OBX? Dont get me wrong i love what your doing here but i just dont see why?

[Ajax]

Nothing necessarily "wrong" with the OBX, er Hotshot design. Its better flow than the stock log, most likely; and is a decently available-less costly upgrade. However, the tubing is anything but equal length, so there is a good amount of pulse interference. My knowledge of flow dynamics is limited, but basically, we're looking to get a vaccuum effect to help scavenge. When you're primaries are all different lengths, its difficult to essentially balance things out. Also, the fitment needs work a lot of the time. As to why- the OBX would be fine with a largely stock engine, but I've got quite a lot done to mine- the OBX is a limiting factor at this time, I believe.
With whatever design I arrange, I'm hoping to keep all the tubes roughly the same length, with a proper merge collector just before the cat. It should be a bit of a challenge, but it should be fun, too.
With the OBX, I had just over 175 peak hp with 165lb-ft (pretty flat plateau there, eh?)

With the new header and tuning (going to be upgrading to AEM Ems), I'm hoping to keep a pretty flat torque band, whle bumping up the top end. If I sacrifice a bit of lowend to reach 200, I won't be too disappointed.

[95zenki man]

Wow. Good answer, thanks for taking the time and actually typing all that out. I don't know a lot of people that would drop such a large amount of money on a tuning setup and custom make everything like that to reach 200hp. But more power to ya if you can.

Any real reason you want to stay NA rather thin go boost?

[Ajax]

I originally had reservations about turbos mainly because of perceived tuning and reliability issues- when I started getting into cars, I read so much about how much tuning seemed necessary, and all the parts that seemed to need upkeep- intercoolers, wastegates, blowoff valves, extra gauges- it all seemed staggering at the time (which is funny, because I've spent more money at this point than what I would have needed to build a daily-driveable 300hp beast). And I realize that knowledge of tuning and turbos has come a long way (and may in fact been over-complicated in my own perception), but I've really grown to love how this engine makes power, and I love the sound it makes on its own.
I also won't deny the idea of reaching the 200whp goal on pump gas that so many others have talked of but failed to achieve (if successful, I may be the first, as far as I know).
Plus, I don't really see the point of more hp than that for this small car on the street- I've got more than enough to get in trouble as is. If I had a turbo, I'd probably be scheming to keep increasing power; NA, I've got a goal, and when I reach that, I can just enjoy.

[95zenki man]

Sounds like your with the Honda boys on the quest of maximum NA power. Im always up for showing everyone we don't need a turbo to make power.

Keep up the good work!

[Ajax]

Sounds like your with the Honda boys on the quest of maximum NA power.

Except that I have torque to go with that power

[corn322]

Looking good so far. Are you going to stick with the tri-y or will you build a 4-1 header? I think I have a Hotshot header, I bought it used and there are no markings on it. I remember measuring the tube lengths one day, I think they were within an inch of eachother.
Mine also ties together differently. It looks like your OBX does 1-4 together and 2-3. My Hotshot has 1-3 and 2-4.

Also, your torque curve is awesome. I'd like to drive your car.

[95zenki man]

Any plans to run ITB's? or are you just sticking with the stock setup?

[Ajax]

I'm currently running an Xcessive Motorsports intake manifold. ITBs might happen in 5 years or so if I'm bored and want to switch things up.
OBX is 4-1, 2-3. I don't know of any headers that are 1-3, 2-4; that would be where an unequal length header would seem to make sense, though. A year ago, I measured out the piping on the OBX; can't find the measurements right now, it was pretty ridiculous~ something around 14" #4 primary to go to the 9" #1, 10"&11" for 2&3; 23" #1-4 secondary, 18" #2-3 secondary: pretty much the antithesis of equal length. From what I've seen, the OBX is a copy of the Hotshot. The DC sports looked like a better design when I last saw it.
I will be trying to fit a 4into1 design. Its going to be pretty tight, so we'll see.

[krash]

Pretty cool project. Have you looked into pacesetter? Thats a 4-1 design as well

[Speedy7_7]

I would like to see what we could do to your car on e85, would that fall into your pump gas category? There is a ton of it in here in MN. Can't wait to see the car again this summer.

[Ajax]

Pretty cool project. Have you looked into pacesetter? Thats a 4-1 design as well

Yes, but Pacesetter is pretty notorious for quality issues and crappy coatings. The runners are most likely too small for my engine specs- 1-1/2" runners might be okay for stock guts.
E85 would qualify as pump gas, but I'd like to hit 200 on dino premium first.

[Ajax]

Found those measurements for the OBX header-
Primaries- from head to 1st connection with other tubes- 1.75" OD
#1- 9"
#2- 14"
#3- 11"
#4- 15.5"

Secondaries- from 1st to 2nd connections- 2" OD
#1-4- 29"
#2-3- 19"

These are actually bigger diameters than I will be using. Here's to hoping that the in-between header diameter along with a proper merge collector will improve flow.

[Ajax]

Still have not recieved the exhaust tube bracket, which makes it difficult to finallize this project, but at least I started.

Here's the elbows- I recieved 6 total, but I wish I had more. Actually, there's a few things I wished for during this process.


Here's the 1st attempt, and the resulting lengths:



However, things were getting really tight underneath:

Fitting all 4 pipes through that tiny area was proving difficult- especially since I only had 2 extra adjustable elbows (one of the adjustable elbows was so tightly threaded, I actually had to saw and tear off its sleeve- that wasted a good 30 minutes) and a bunch of PVC elbows (which are much thicker than the actual tubing will be) to mock the rest. I may call Stainless Headers MFG to see if they can send me some extra adjustables. They prefer the PVCs for the rigidity and their stock size.
So with all that trouble, I started thinking of other options:


But I always seem to run into the same problem.

I haven't completely given up on a 4-1 header, but a 4-2-1 design would definitely be simpler- I understand why pacesetter uses such small runners and nobody else makes a 4-1. While I'd prefer a true 4-1, I know I can do a better job than the OBX on a 4-2-1 if I need to.
Also, cutting all this pvc with a hacksaw is getting monotonous. I may crack and buy the larger diameter pipe cutter.

[costa_rican13]

i have a 4-1 on my ka

[Ajax]

i have a 4-1 on my ka

Why you gotta tease like that- Details please!

[95zenki man]

i have a 4-1 on my ka

So do i, but its got a lil turbo on top

[DanThaMan]

maaan I hate to break it to ya but that pvc pipe wont work well as a header...I think it will probably melt

[Ajax]

maaan I hate to break it to ya but that pvc pipe wont work well as a header...I think it will probably melt

Its okay, I only live a 1/4 mile at a time, so I can let them cool down between runs...


I started dreaming up new runner routes. If the #1 is routed over the top, I'm wondering if I can get the rest underneath using enough tubing to route the collector by the firewall rather than underneath. We'll have to see- I picked up some more PVC joints to try some different things.

[TheRealNap0le0n]

do a RHD conversion and then you will have plenty of room for the header

[terry_240sx]

do a RHD conversion and then you will have plenty of room for the header

word. lol

[Ajax]

RHD NA KA. That would confuse fanboys to no end. lol

[krash]

Just tell them its teh speshul edishun wif a ka swap