I've been doing a fair amount of research, on forums with quite a few top racers/builders that like the single cam Honda's, particularly the d-series. (Don/SOHCinWA, Rushi, Big Tuna, occasionally Bisi, Luke/Live for Physics, DocHudson, Acid Beave, etc). A few of the previously mentioned people have said that ~40" long runners with a GOOD 4-1 collector (with good choke, a good taper back up to ~2.5", etc) will make good power through the entire rshared_pm range.

Good thread: exhaust setup - onecamonly.com

I've seen more than one good source say that the programs/formulas for calculating manifold sizes aren't good. The exhuast is way too dynamic and nothing short of experimentation will get you the best results. I'm too poor to do that, so my header will be based on research and the design of a few other high-power builds.

From my build plans (PM me if you want to see all of it), I had the fallowing laid out for the header design. No idea on shape/design of the actual pipes, but this is just rough notes from my research. Not sure on a few numbers and I won't be until the engine is assembled.

D16 Stroked to 1.7L, 12:1+ comp, tuned on 93 oct, shooting for 170whp+
CAI, Edelbrock Performer X IM, Custom Header, 2.5" exhaust
D16Y8 VTEC Head (Good quench, Swirl Ports. Good low-mid range, porting will improve high end)
Bisimoto L3 Cam (2000-8000rshared_pm power range), Springs/Retainers/Cam Gear


Packaging has alot to do with header design/I'll be running the header/exhaust under the engine/car, through a high flow cat, a muffler or two, and dump out of the rear bumper. So the above idea wouldn't work. And I've read that good exhuast scavenging really helps pull the last bit of power out, and working with a small displacement engine, I really need that last bit of power.

But idk. I'm mostly talking out of my ass. I'm no expert at anything, just trying to plan out a good build/header. My design would be something like this one (first pic), but I'm thinking about doing doing something more radicical like in the second pic (although with longer primaries)... Third picture is a Bisi header for a D16, fourth is a Bisi header for a F22 (both Bisi headers are Honda engines).

Hondanickx's Custom D16 header from OneCamOnly:


Random Race Header Remoer on OneCamOnly Found:


Bisimoto Version 2 Header for D15/D16's:


Bisimoto F20 Header (on BigMike's Prelude):

 

you're thinking about this in terms of one constant flow. In an exhaust, it isn't constant, it is pulses, and you have to remember that it isn't just one pipe, it is part of a set, and there is something that will speed it back up, the vacuum created by the pulse of exhaust just before it. in one runner, no, it just slows down, but as soon as you hit the collector, the pulse in front, "pulls" the pulse behind it, which in tern, "pushes" the pulse in front of it. Pretty much the most important part of the entire exhaust system, as far as making power goes, is the collector.

are you trying to imply that the super heated exhaust is going to want to rise because hot shit rises?
It is hot enough that, that isn't going to apply. I mean, yeah it would in an open air environment, but that isn't going to make any difference at all in this situation. The gas is so hot and moving so fast, that it doesn't really care which direction it is going, as long as nothing is in its way.
I see where you are going with the whole ambient temp thing, and again, that doesn't really matter. A good header is a good header in 50* or 120* Yes, the flow will be different, however, not a variable that you have to consider when designing.

actually, that is a really crappy way to design a header. There is no collector, so you are loosing that scavenging effect. and you actually have more air pressure to push through because of the dramatic drop in temp.
You want at least some pipe beyond the collector to let the exhaust continue to move out of the way while it cools down. What about F1 cars you say? They have a collector to take advantage of that. and because they rev out so far, they have a lot more exhaust flowing out of that pipe, and they dump their exhaust into the vacuum of air just behind their car. The "rules" change a little bit when you're doing over 10,000 RPMs when you slow down.

 

That's the forum/link I was referring to previously.
That'll pretty much tell you what you want to know... or at least as much as you can without years of practical knowledge.

sounds like you're on the right path to "figuring it out"

 

heres one im working on now

 

I hadnt considered the venturi effect caused from the gas pulses of each pipe passing into the collector...yet one more thing to toss into the variables mix lol >.<

Needless to say, you are correct in assuming the only way to get a flawless header design is by trial and error. There are entirely too many things to consider for it to be cost effective.

The purpose behind my illustration was to show the intricacy and complexity of determining exactly and precisely the differences made by the bend itself. Ambient temperatures may not make a noticeable difference in power increase on the engine, however every 0.0001 bar or cfm of decrease should be accurately accounted for in determining exact differences if you're going to go so far as to concern yourself with the bend ID's impact on overall flow in a mandrel bent header. To be completely accurate it would need to be checked repeatedly in a controlled environment with precision equipment. Again, all in all...it's really just not worth it...this is the sorta stuff those guys who are busying themselves creating extreme output ceramic 4 cylinder engines worry themselves with.

And the rearward swept angle of the pipes on drag engines remain exposed to passing air as the car moves forward...creating the same venturi effect as the collector pipe...only much more dramatic. Anything that spoils airflow creates a small vacuum behind it...kinda like when you draft a semi on interstate to conserve on fuel.

 

Got any good pictures of the goilette spike inside the collector/pre-assembly pics of the collector?

 

ill take one in a bit

 

Header design and a few other things
Tampa Racing to The TOP!