Thread: looking for some exhaust advice (not another 2.5 vs 3 inch question lol)

Alright guys this is going to be my first all motor serious setup and I need some help on my header idea .. coming from hondas this header design has been known to make more power on the larger displacement b series motors than any other (sometimes quite a bit more) but being that VVL is a bit different than most b20vtec builds I was wondering what your opinions are on opening it up to a 3" outlet for basically a true full 3" exhaust im going to include a picture





right after the o2 bung is where I was thinking to flare it to 3 inch

As of right now the plans for the motor internally are basically stock besides n1 cams but if I really enjoy it im thinking of doing a built motor later (possibly stroker with 12ish compression bigger cams ect) or maybe just boost it im not sure but opinions and thoughts on the header opening up to 3inch would be greatly appreciated!


Or should I just stick with a hytech copy?

@cory
@Payu

Plus some other folks to chime in on this.

That header looks good as long as long as you keep the choke to 2.25 and the hard part will be to make a nice transition to 3 on that angle!!
But it should work I think someone on the forum already did one of those for a DE!!!

I agree w payu. Your going to be better off keeping the 2.25 in choke w a nice smooth transition back into 3. Of course a lot of people think bigger is always better but it couldn't be further from the truth. The idea is to keep velocity as high as possible and the smaller choke aids in this. Keeping the velocity up actually creates a low pressure and if done correctly will actually pull spent gasses from the cylinder. Once you get things really dialed in this can even help add momentum to the fresh charge coming into the intake side of the head.

My new header!!


Still full street jejejeje
Even with the megaphone and reverse cone!!!

So if I am to understand you guys right I should leave it smaller (I know end opening is 2.75 but not sure on the choke at that point) and maybe flare out to 3" like under the oil pan maybe? This is a B series header knocked off from bisimoto (owner of the fastest all motor single cam honda) .. does this idea sound better to you guys?

Its been proven that bisimoto headers are not the most power makers headers in the honda market!!!
But remember you are getting this header for materials basically since bends wont fit as is!!
So you have other choices!!

Just basically fallow like if you going to build a Tri-Y header longer primaries and 2.25 choke..bud search for the Tri-Y header...this is what almost every one from PR are running making good numbers either DE or VE.( @Payu, @mercado ser ) for my understanding are well informed on everything. They can keep you on track so you are in good hands bud.

Im not entirely following you on the materials part .. but I guess thanks

He said materials cause that's basically what you are doing. You are getting the header and brake it all apart to then weld it back again. But this time making a customization to fit it on the engine. So you are pretty much using it for materials. You still kind off keep the same original design but you are changing positions of the primaries. Just follow this link it would help you to build your header is kind of building a Tri-Y is just a different design header. Your header is more of a Ram Style Tri-Y the other one is just regular Tri-Y same concept. But they all are a little different cause is a custom header to fit our engines.
Here are 2 links first link is back to 2010 when @mercado ser started building one second link back to 2011. Take your time and inform more and search and you will have a good damn header they are proven to be probably the best or one of the best header out there for us.
http://www.sr20-forum.com/vvl/26855-tri-y-headers.html

http://www.sr20-forum.com/vvl/51672-custom-tri-y-headers.html