my experience with exhaust is like many other things: you get what you pay for. If you go out and spend a lot of $$ on a high quality exhaust like greddy, HKS, and the like, then your going to have a good system. The REASON most of these for N/A cars are sold in 2.5" piping is because its the "industry standard" if you will for exhaust manufacturers and N/A cars. To answer your question, they do this because its the ideal setup for N/A applications.
Now i dont want you to poop your diaper again over the SECOND post so ill answer that question as well. I would highly advise against custom piping on your N/A car for a few reasons. One reason is that if you choose custom piping and a generic muffler (or even a half way decent muffler for that matter) its probably going to sound loud and obnoxious. My advice is to pick a brand you like, find people with that brand and ask them how their car sounds! if you like it get it end of story! Secondly, custom applications are really only beneficial on very high performance cars ie: 300+HP n/a and almost all turbo cars. If your plans are to get a "custom" exhaust because its the "Jdm tYte yo" thing to do to improve performance on your basically stock KA engine then NO custom exhaust won't do $hit and you will waste your $$ Bottom line is you would be either
A) full of crap B) uncertain or C) very touch sensitive if you said you could "feel" a difference between 2.25" 2.50" some people can't even tell a difference between 3" piping either
N/A piping for all round power?!
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deftdrummer
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M3thod_Man
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deftdrummer
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I'll toss in my 2c here for the hell of it:
I had a '67 mustang that at one point had a 302 in it. Engine was about half the displacement of a KA24 and with my mods had a bit more than twice the power of a stock KA (316rwhp). I had a set of headers but from the headers back I had two different exhaust setups (three if you count the stock one). My first one was 2 1/4" dual exhaust all the way back, no cats and 2 1/4" dynomax superturbo mufflers. Great setup. After a while (but without doing any other power mods in the meantime) I got upgraded to 2 1/2" all the way back, again no cats and 2 1/2" dynomax superturbo's. Pretty much the only variable here was piping size. I never got the 2 1/4" setup dynoed, but my trap speeds were consistently around 1-2mph faster with that setup than after I went to 2 1/2". More than that, the car just felt a lot faster with the 2 1/4".
Considering that 2 1/4" dual exhaust (one 2 1/4" exhaust for each bank of 4 cyl.) worked perfectly on that car, and the KA is almost exactly half the displacement and output, I would definately get a 2 1/4" exhaust over a 2 1/2" for an NA KA24.
Just my opinion, doesn't really matter for me as I'm gonna go KAT:D
I had a '67 mustang that at one point had a 302 in it. Engine was about half the displacement of a KA24 and with my mods had a bit more than twice the power of a stock KA (316rwhp). I had a set of headers but from the headers back I had two different exhaust setups (three if you count the stock one). My first one was 2 1/4" dual exhaust all the way back, no cats and 2 1/4" dynomax superturbo mufflers. Great setup. After a while (but without doing any other power mods in the meantime) I got upgraded to 2 1/2" all the way back, again no cats and 2 1/2" dynomax superturbo's. Pretty much the only variable here was piping size. I never got the 2 1/4" setup dynoed, but my trap speeds were consistently around 1-2mph faster with that setup than after I went to 2 1/2". More than that, the car just felt a lot faster with the 2 1/4".
Considering that 2 1/4" dual exhaust (one 2 1/4" exhaust for each bank of 4 cyl.) worked perfectly on that car, and the KA is almost exactly half the displacement and output, I would definately get a 2 1/4" exhaust over a 2 1/2" for an NA KA24.
Just my opinion, doesn't really matter for me as I'm gonna go KAT:D
I have 2.5 inch custom from the cat back and no headers (yet) with a glass pack and it is a little loud, but the power gains were great. Horsepower is great because it puts gearing to full use. I lost very little down low and gained alot at top end. There is no wheezy ricer sound but a throaty growl. It is opverall a pretty nice system. KA's have bass and i like em.
Im still somewhat of a noob when it comes to the 240, but I believe I can help answer your question. I used to own one of the quicker NA eclipses over on 2GNT, actually the 2nd fastest out of thousands with just bolt on's. I chose a 2.5" mandrel bent exhaust over a 2.25" exhaust for several reasons. #1 2.25" systems are great for hondas and all, but my car came with 2.25" mandrel bent piping stock, so spending 100's on a name seemed like a waste to me. Plus the car had 2.0ls of displacement rather than the 1.6 or 1.8l's that come in most hondas. Realistically the power loss you experience down low will be minimal at best. At one point I had a spun rod bearing and had to throw the stock exhaust back on so everything was covered by the warranty, and while I did gain some low end back, the top end was more than worth the loss. With a 2.4l I would definitely not upgrade to anything smaller than a 2.5" exhaust system. If you plan on going to NA route this will probably be big enough for all your future plans as well.
The right pipe size?
I have a 95 240SX and I recently replaced the original 2" to 2.5" piping from the front top catalyst all the way to the muffler. I removed the 2nd catalyst from underneath and the resounator, and put a dual tip muffler.Let me tell you that it sound like if the car didn't have any muffler at all ! LOUD !!! not the loud kind that you want to her.
I went back and installed a new catalyst, it still makes noise, but tolerable, I guess that the muffler doesn't keep much sound cause it was a cheap one, BUT I can say that the car gained a little more power.
I'm happy with the whole new piping, but I may end up swapping the muffler that I paid $60 for a better one.
I went back and installed a new catalyst, it still makes noise, but tolerable, I guess that the muffler doesn't keep much sound cause it was a cheap one, BUT I can say that the car gained a little more power.
I'm happy with the whole new piping, but I may end up swapping the muffler that I paid $60 for a better one.
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quiksilvia
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From what i know, the bigger the diameter, the less torque,but as was mentionned, there's more PEAK horsepower.How big an rpm range you can use that newfound power depends on many things.
The basic concept here is to find the optimal COMPROMISE between flow and backpressure. Smaller diameter increases the backpressure which helps out the torque. Bigger diameterincreases flow needed by more powerfull/bigger engines butcosts torque, which more powerfull/bigger engines usually have more of anyways.
I JUST bought a 1990 240SX SE and compared to my old scirocco 8v, i find it lacks a bit of torque, but revs pretty nice. Compared toa 1999 Miata though, it's pretty good overall. I'm a torque guy and when you say you want good all-around power, i thinktorque is often the answer. It helps you get of the line faster andgenerally just keeps you from downshifting for passing, just stepon it and it goes. It depends a lot on preferences and , of course, cars you've driven before.
Typically on a VW 1.8L, 2-2.25" is pretty much the standard.Reading the posts here, i think 2.25-2.5" would be the best 'all-around' for a 240SX.
One thing i'd like to add. I often hear people say "i changed myold exhaust, the new 'insert exhaust name here' makes more power..." I myself did change my old clogged cat and muffler toa no-cat , sport muffler system. Had better power all-around after,i especially noticed how the engine revved better. Thing is, my old exhaust was BAD. You can't compare a regular worned out exhaust to a brand new sport one. Compare new to new and thedifferences are often much less noticeable.
The basic concept here is to find the optimal COMPROMISE between flow and backpressure. Smaller diameter increases the backpressure which helps out the torque. Bigger diameterincreases flow needed by more powerfull/bigger engines butcosts torque, which more powerfull/bigger engines usually have more of anyways.
I JUST bought a 1990 240SX SE and compared to my old scirocco 8v, i find it lacks a bit of torque, but revs pretty nice. Compared toa 1999 Miata though, it's pretty good overall. I'm a torque guy and when you say you want good all-around power, i thinktorque is often the answer. It helps you get of the line faster andgenerally just keeps you from downshifting for passing, just stepon it and it goes. It depends a lot on preferences and , of course, cars you've driven before.
Typically on a VW 1.8L, 2-2.25" is pretty much the standard.Reading the posts here, i think 2.25-2.5" would be the best 'all-around' for a 240SX.
One thing i'd like to add. I often hear people say "i changed myold exhaust, the new 'insert exhaust name here' makes more power..." I myself did change my old clogged cat and muffler toa no-cat , sport muffler system. Had better power all-around after,i especially noticed how the engine revved better. Thing is, my old exhaust was BAD. You can't compare a regular worned out exhaust to a brand new sport one. Compare new to new and thedifferences are often much less noticeable.
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Julio Bro!
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Hello M3thod_Man:
I see myself in your question so I'm gonna offer my experience. I did a lot of testing looking for power without the deafening sound.
Because in most places it's the law you can't eliminate the cat converter, so replace it with a performance brand, like a Random Tech.
Have a 2.5" tubing made from the cat to the muffler, eliminating the resonator, but keep the side hanger (prevents noises).
The muffler choice is the key on sound:
1) No muffler will bring the most gains without being loud inside your car, but outside is gonna be a riot. You can fit "inserts" in the tubing to lower sound a bit, but it's not much really.
2) A straight flow muffler or "open types" will bring gains similar to no muffler without being a riot outside, but inside your car it's gonna be too much. Many people tolerate this and the looks are better, particularly the mirror finish types.
3) A better designed OEM type replacement like the one from IMCO or Walker. This works because most manufacturers go with bigger inner tubes and smaller lighter casing, which brings better flow with sound control and less weight. Obviously gains are less, but sound is close to OEM with a better tone.
My choice of muffler was OEM type with chrome 3" tips installed at the shop. No muffler was great, but the people at my condo complaint, and I understood; also the police here is ticketing excesive noise lately.
The cat is $100, OEM type muffler is $35 ($0 for no muffler, $80 plus for stainless straight flow), tips are $25, and installation with tubing is $60 = $220. So, you save like $200 or more and produce gains in horsepower/torque.
For more power add a header.
I see myself in your question so I'm gonna offer my experience. I did a lot of testing looking for power without the deafening sound.
Because in most places it's the law you can't eliminate the cat converter, so replace it with a performance brand, like a Random Tech.
Have a 2.5" tubing made from the cat to the muffler, eliminating the resonator, but keep the side hanger (prevents noises).
The muffler choice is the key on sound:
1) No muffler will bring the most gains without being loud inside your car, but outside is gonna be a riot. You can fit "inserts" in the tubing to lower sound a bit, but it's not much really.
2) A straight flow muffler or "open types" will bring gains similar to no muffler without being a riot outside, but inside your car it's gonna be too much. Many people tolerate this and the looks are better, particularly the mirror finish types.
3) A better designed OEM type replacement like the one from IMCO or Walker. This works because most manufacturers go with bigger inner tubes and smaller lighter casing, which brings better flow with sound control and less weight. Obviously gains are less, but sound is close to OEM with a better tone.
My choice of muffler was OEM type with chrome 3" tips installed at the shop. No muffler was great, but the people at my condo complaint, and I understood; also the police here is ticketing excesive noise lately.
The cat is $100, OEM type muffler is $35 ($0 for no muffler, $80 plus for stainless straight flow), tips are $25, and installation with tubing is $60 = $220. So, you save like $200 or more and produce gains in horsepower/torque.
For more power add a header.