Ok I've read a lot on here and other places and I still don't have a clear answer to my question.

I am doing a mild NA build on my SOHC and need some advice on what kind/size of exhause I should get.

I have an ebay special "OBX" header, resonated 2.5" diameter testpipe.

I completely rebuilt the engine with oe internals, bored 50 over. I plan on getting a tuned chip, upgraded cam, have intake, ignition system, lightweight flywheel/crank pulley, upgrade wires/plugs. I'm not sure how much power I'll get out of all this but I'm sure it will be under/around 200hp.

What diameter cat-back exhaust should I get? I have heard 2.25-2.5 is good for all motor 2.4L engine. I don't want it to sound like crap. I'm thinking a custom compression bent cat-back pipe with a resonator and magnaflow street mufler. I want it to be quiet at low RPM's.

Would a 3" catback work well if I added a resonator?Is it really going to make that much of a difference if I don't have mendrell bent pipes?What non-turbo systems are available for this car?What is everyone else's setup for NA KA? How do you like it?

Also, I don't want anything that i have to keep one of those ugly silencers in.

Thanks in advance for the information.
Modified by FSUDrifter at 2:28 PM 3/31/2006

s13/s14?

S13 (SOHC)

This guy says 2.25 is best:http://home.att.net/~MabuhayCarlos/Exhaust.html

FSUDrifter wrote:S13 (SOHC)

This guy says 2.25 is best:http://home.att.net/~MabuhayCarlos/Exhaust.html

That guy doesn't know what he is talking about.

2.5 for stock, of lightly modded daily driver, 3" for everything else. 3" with resonator is fine too. You will not lose any low end.

2.85" ftw.

lrb_2000 wrote:2.85" ftw.

I have always wondered this. Never seen any 2.75 inch systems or whatever. Seems like you could possibly end up with a better powerband gain than 3" on NA. Maybe not more peak horsepower, but probably a more useable gain. Hmmm

lrb_2000 wrote:2.85" ftw.

noob, we all know 2.73921 is the best

jk id go with 2.5 idk why, it just sounds like a nice number

Good god, has this topic been flogged to death. Do a search, and pray Insanity doesn't see this thread.

JimmyMethod wrote:Good god, has this topic been flogged to death. Do a search, and pray Insanity doesn't see this thread.

Werd, but you have to agree that an intermediate size like 2.7 has not been discussed.

I did search, but every car has a different setup. I was kind of just hoping that other people with NA KA's could tell me what they have and how they like it. And even though there are other threads about this I'm sure there are plenty of other people with this question since all 240sx's are NA KA's to start with. Besides the fact that i get flamed if I bump old posts so I might as well get flamed for this.

FSUDrifter wrote:I did search, but every car has a different setup. I was kind of just hoping that other people with NA KA's could tell me what they have and how they like it. And even though there are other threads about this I'm sure there are plenty of other people with this question since all 240sx's are NA KA's to start with. Besides the fact that i get flamed if I bump old posts so I might as well get flamed for this.

You should search. Since I am nice, I will say this:

3" gives the most gains, but is louder, and won't gain as much midrange as a 2.5. Generally sounds kinda crappy on na cars.

2.5" is quiter, gives good gains, and sounds nice.

On either system, you should get a resonator installed as well, because you are not turbo, and don't want it droning too bad on the highway.

well the car is my dd so 2.5 would be better lower range and 3 would be better high range power?

Also, for a car under 200hp, the type of bending won't really make that big of difference, right?

i think i'd go 2.5 see'n thats what your header is 2.5

FSUDrifter wrote:well the car is my dd so 2.5 would be better lower range and 3 would be better high range power?

Also, for a car under 200hp, the type of bending won't really make that big of difference, right?

Yeah go 2.5.

Bends are actually pretty important. You want the fewest number, the least amount of angle to them, and mandrel is the best.

My system is custom and has 2 bends. Both are under 20 degrees, and are unfortunately not mandrel bends, but being that they are so shallow, it's not a huge deal.

JimmyMethod wrote:pray Insanity doesn't see this thread.

w3rd

3 is a little much. if you are going to stay na then go 2.5. With a 3 inch you are going to loose alot of low end torque. Turbo cars operate alot better with a 3 inch b/c back pressure is a biotch.

eds13 wrote:i think i'd go 2.5 see'n thats what your header is 2.5

I dont think his came with a header...

Hello FSUDrifter, I think you might benefit from my experience. Like you, I wanted a practical performance exhaust without wasting too much, so I searched for parts and opinions. I tried a few setups so I'll tell you my findings. There's something you don't mention and it's how you feel about droning/resonation inside the cabin; I despise it and so my search focuses on that.

Most exhaust companies recommend 2.25" to 2.5" for a 2.4L NA engine and bigger for forced induction. This because to maintain the scavenging effect, necessary for good combustion, the gasses must go at a certain speed, if pipes are too big the NA engine can't push enough to get that speed at mid rpms; where you usually drive.

Dronning is a function of the size and speed of the sound waves exposed in the system. A smaller tube channels a smaller, faster wave, which drones less than the bigger, slower wave of the big diameters. OEM mufflers and "true" resonators use a wave cancelling method which usually involves chambers and small diameters for specific frequencies and that makes them restrictive. Performance mufflers don't have this, so all have dronning, the magnitude depends on the engine and the exhaust size.

I can say for a fact that a tube with no muffler will produce almost no resonation. This because the wave is only exposed at the end, but will be loud as hell outside and for most places this is illegal...and annoying for people. A performance muffler exposes the wave in a box which creates a harder drone, but quiets the sound outside.

Most so called "resonators" for performance exhausts are glasspacks or small straight mufflers which only absorb some more of the sound; it's like adding length to the muffler. The only true performance resonator I know exists is the one used by the BRM system, which is famous in the NICO forums. This is not a glasspack, but a straight system surrounded by a chamber that cancels some of the dronning frequencies. Apparently, results are very good. I think HKS uses a true resonator too.

So:

* 2.5" - gives more power at high rpms, there's a lot of droning.

* 2.25" - gives less power than 2.5", but better feel at mid rpms; there's less droning than 2.5".

* 3" and more should only be used for high compression or forced induction engines; NA power increase would be marginal and droning should be terrible.

* To cut on dronning use the longest straight muffler and glasspack/resonator you can fit. It won't dissappear, for that you'll need a specifically designed true resonator on the 2500-3500 rpm range; doesn't exist.

I have a 1993 240SX SE and right now I'm using a 2.25" system with a Magnaflow muffler and a 20" glasspack. Although acceleration is not explosive, it's much more pleasurable than any of the bigger systems I've used before. If you have the money, the BRM system is probably the best, followed by the HKS.

Modified by Julio Bro! at 10:26 PM 4/6/2006
Modified by Julio Bro! at 3:18 PM 4/7/2006

i went with the pace setter headers and pace setter monza exhaust, also added a high flow cat. the exhaust I have is 2.25 and all of it fromt he headers back is completely black except the cat. For everything in my exaust i payed 530 shipped. I think it was a decent deal. The car sounds muuuch nicer than before, also due to the custom short ram air intake i put in(I modified an aftermarket inake tube for a honda and moved my battery to the drivers side, and cut the rusty metal out where the battery used to be and got a new plate welded in its place with a 4 inch hole in which I got a grill welded for cold airflow). I didnt notice any decrease in my low end and did definately notice it in the mid range quite a bit. I like the whole black look with the headers and exaust so im stickin with the pacesetter till i've worked my *** off for money to boost it.

OK, thanks for all the help. Here is the very affordable setup I decided to go with:

Stainless Steel OBX 4-2-1 Ebay Header $200 shipped:

Ebay 2.5" Stainless Steel Resonated Test Pipe $50 shipped:

Megan Racing Drift-Spec 2.5" Cat-Back Stainless Steel - $333 Shipped w/ Insurance:

Thanks for all the input. I know it's all cheap stuff ($583 engine-back setup), but it's stainless so as long as it fits, I think it should last a while. There is a good chance I might swap the motor sometime in the future so if it doesn't last that long then oh well. Hopefully this setup won't be too loud. I have a feeling it might be. If so, I might just have to add a Magnaflow resonator. I'll post pics when I get it installed. I'll do some sound clips too. Again, thanks for the input.