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Discussion Starter · #1 ·
Ok, I'm not too keen on exhaust mods so bear with me.

the exhaust manifolds on out engine connect at what i can only describe to be some kinds of h pipe. it looks like it wouldnt create a good steady flow with the rear manifold flowing towards the front of the car for about a foot or more and create turbulance. a single direction flow straight to the back would be better by creating a vaccume and sucking more exhaust cases out of the cylinder on the exhaust stroke right? remember, i'm not too sure on exhaust science here.

If i was to cut the "h" pipe off and replace it with a Y pipe so the rear manifold pipe came straight down and towards the rear instead of the front would that be better, and what could i expect? would ill kill torque and increase high end? or does the "h" pipe already do a good job?

I understand you have to have some back pressure so the air can help pull the air beind it as it goes out like a cycle, kinda like a siphon.
 

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Discussion Starter · #3 · (Edited)
what do you mean exactly john? what parts of piping?

i got a question about piping also, i'd like to do this all by myself with clamps because i dont weld. clamps will work on any pipe, excluding the exhaust manifold its self right?

you know that flexable exhaust piping? i know its ridged and not great for maximum flow but thats gota atleast be better with flex pipe and y-pipe than the OEM setup.

Is it legal to use flex pipe or clamps before the cat or do you have to weld? i know you can use them in "cold air" applications as in post catalytic

how much anyone think installing a Y pipe would run at a shop?
 

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this has been talked about before, but I've never seen anyone do it...I think it's a good idea...not sure what you'd get out of it performance wise...just makes more sense flow-wise
 

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the pipes from the exhaust manifold to the resonator are double wall, meaning there is a second pipe inside the outer pipe. It's overkill like everything else, sometimes good overkill, sometimes bad overkill. Moral of the story, legend exhaust it built good but not for flow!!!
 

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Discussion Starter · #7 ·
i dont really mind the piping before the 2 meet cause its not like im getting headers or anything, i believe headers for a NSX will fit it by looking at the bolt pattern but they cost more than my whole car.

not too sure on this one, but shouldnt the diameter before they meet be exactly half of what they are after they meet? I've got my manifold off right now so illl measure inside width of both tomorrow when i have some light.

If i can find out for sure if i can use clamps before the cat and still pass inspection i'll do it soon as i get my engine back together
 

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Discussion Starter · #8 ·
i just looked at the headers and pipe and they both seem to have a 3cm internal diameter plus the piping from them isnt mandrell bent so its even worse.

theres one thing though.. the front manifold looks more restricted than the rear, it has a second chamber using up about 20% of the outlet.. i'm guessing its for the AIV/ERG valve to introduce/suck air through.

so with the front more restricted than the rear it makes sense now why honda made the rear manifold take a more restricted pipe route to equal out that difference!

I've got a good solution to this though.. you probably wont pass emissions though.

if a rear manifold can be put on the front which i think it can but not sure, you can just pull one off another legend and have them both the same :) you would have to block and disable the AIV and ERG valve i think since a rear manifold lacks the connections for them, anyway disabling these will make your air intake a little colder, not sure if its significant or not but who cares, its just a bonus.

Also the rear manifolds widens a bit directly after the outlet so im sure you could bore the outlet to 4 to 5cm's then be able to use 2 1/2 inch piping after the Y pipe connecting them. 5cm+5cm=2.5 inches

i believe this is about as close as we can get to custom headers and should yield some decent results theroretically.
 

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A true "H" pipe is proven to improve exhaust flow due to pressure pulse tuning. I haven't looked under my car yet to see what you're describing but I'll be it's the same concept. Sort of a 3-2-1 exhaust design instead of 3-1.
 

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slartibartfast said:
A true "H" pipe is proven to improve exhaust flow due to pressure pulse tuning. I haven't looked under my car yet to see what you're describing but I'll be it's the same concept. Sort of a 3-2-1 exhaust design instead of 3-1.
no the front manifold goes under the pan and straight out, the rear manifold goes under the pan as well but curls back for some restricted exhaust flow :****:
 

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Discussion Starter · #12 ·
yea, its not a true H pipe, its more like a upside down lower case h, i dont know what else to call it.. but anyway, i just got a piston and everything for my car and soon as it gets running ill go get the 2nd exhaust manifold, its only 11$ lol
 

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Well I'm completely new to honda motors, on my mustang I replaced the factory mid pipe for a bassani x pipe way better flow than a h pipe plus it added more hp and sounds sweet with my borla cat back and hooker full lengths
 
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