Keith13b

iTrader: (3)

What is the best diameter exhaust to install to make a true dual exhaust from the headers back.

2.5" or 2.25"

I do plan on installing NOS in the near future, so I have been leaning to 2.5", but I'd rather be sure before I drop down the $$. That rotary in my blood is screaming - "Too big kills power" and I want to optimize the exhaust, but I know that bigger isn't always better. Remember I'm upgrading from the header back, this isn't just a cat back setup, so the answer ins't so obvious.

Thoughts?



Thanks,
Keith

Bean

iTrader: (1)

2.5" should be fine I'd think...

2.5" is the size to get on a normally aspirated 300zx... so I'd figure it'd be more evident on a motor thats 33% bigger.

With a nitrous kit, you're really going to need the bigger exhaust anyway if you want to run a decent shot.

I plan on a 3" single or a dual 2.5". Leaning towards the 3" single. Of course mine will start with a 3" testpipe/resonator and a 3" catback; and prolly a 2.5" downpipe until I get a turbokit
I also plan on packing a wet shot

SCV8

The 195hp Type R uses a 2" pipe,well it changes from 1-7/8" to
2-1/8",but basically 2".
To get the full benefit of the bottle,some large(1-3/4")primary headers would be cool,with a larger dia. collector.

Bean

iTrader: (1)

thats a 1.8L 4banger

this is a 4.0L V8... BIG difference

2" dual exhaust does NOT give you twice the flow of a 2" single

SCV8

That would be exactly twice the flow,given the same input to each,but now that you mention it,the requirements would be even less as the V8 fires alternately to each bank,so the pulses are farther apart,making the size less of a factor.I'll bet a 2-1/2" pipe flows twice as much as a single 2",and since that's a part of our car's exhaust...
Per cylinder, the cylinder pressures are going to be even higher on the better cammed,higher compression Hondacar.
I just don't think that there's much to be gained by messing with the exhaust pipes on these cars without some serious mods,in my humble opinion.

Bean

iTrader: (1)

a dual 2" system's area over the hole of the pipe is: 25.12
a 3" single system's area over the hole is: 28.26

a 3" single has more area and will flow more air; its not a simple thing of adding inches


2.5" single pipe: 19.625
2" single pipe: 12.56

thats not twice as much; in fact, not even close

I'm using this formula: 3.14 for pi... and pi*radius^2

SCV8

Ok,but flow isn't directly proportional to cross section,since there's drag from,and along the walls of the pipe.
I'm just mostly saying that I don't believe that the requirement is there in our motors for a larger exhaust,not that a larger pipe won't flow greater,but the only way to know for sure is to try it out both ways and look to see any real hp gains,that will tell what all the math/flow equations in the world won't.That's what I love about hotrodding;it can go against the "rules",and that's where the real gains are made.

Bean

iTrader: (1)

Last i checked; the bigger exhaust, the more power was made

but you lose more bottom end the bigger you get

I'll show you real hp gains

i was getting 2.1 60' launches and 15.1 1/4 mile times

i got my exhaust

i was getting 2.3 60' launches and equivalent 15.1 1/4 mile times with a higher mph

whats that tell you?

SCV8

I've got this other car,engine in the back,just not enough room for any good flowing,quiet exaust,so it got the very loud,good flowing,short exhaust,and I know it could be made to be alot quieter,and still have the same performance with a better system,since the engine's basically stock.
So I now have two cars;a quiet one,and a not-so-quiet one.
Maybe a turbo would quiet it down a bit?
There's an Australian company that makes a programmable valve to go in the exhaust to regulate back pressure at lower rpms,lesser throttle openings.It's supposed to help with torque,and emissions/efficiency.I thought it was pretty cool,since then you could go a little overboard on the exhaust,and just tune it with the controller device.

Bean

iTrader: (1)

Nissan has something similar to that in their variable capacity muffler

its pretty cool I think

a turbo will definitely quiet things down; you can put a straight pipe on a SupraTT and it won't be very loud at all