The most basic exhause question known to man

[Riley2.4L]

I know this has been asked so no need for hella posts on this questions. Exhaust sizes... whats just right for a NA KA? also what size is the stock exhaust on a 95 SE

Riley

[Dookie]

This question has perplexed even the most brilliant of scientists. But they have come up with something around 2.5in or 3in. The choice is yours.

[Riley2.4L]

I see... I usually hear that 3 inches is too big for a non turbo engine

[F3600]

well some say its actually beneficial for top end... anyway it will be real noisy

ps:Dookie i like your sig

[Riley2.4L]

Well in that case I'll probably want to go 2.5 then. I want an exhaust that stays relatively quite while cruising the streets but gets noisy when I step on it

[Scooby24]

The Ideal size would actually be a straight through 2.25" to keep noise levels down and not sacrifice substantial power.

But 2.5" will work. 3" is too big.

I had 3" on my 337 whp STi and that's the biggest exhaust made for it....so for NA that's WAY too big.

[Riley2.4L]

ok thanks for the info Scooby 2.5 it is.

[XingYu]

theres been a lot of talk about this before.If I remember correctly 3" isn't too big for the KA. People don't lose power with it. If I can find it I'll post a link to the thread showing some dynos on it.

[raging panda]

yes, this is the most perplexed question ever, but the result of one's dyno charts resulted in the fact that the KA likes a 3" exhaust. I don't know if the dyno is real, or fabricated, but the dyno sheet showed that the KA does not lose any power with a 3" exhaust, only gains it throughout the rev range. It will be loud though.

Anyways, 3" best for KA N/A if you want the most power. dyno proven

[Riley2.4L]

[QUOTE=Anyways, 3" best for KA N/A if you want the most power. dyno proven[/QUOTE]

Well then that gives me something to think about. Cause I really hate those car that have the loud *** exhaust. I don't want to sound like I'm doing 100 when I'm cruising a 15 ya know. But then at the same time I don't want to spend money on something if its won't bring the most out of my car.

[F3600]

Well, i was running a 2.25 straigth pipe on my KA24E and it was sooo noisy ... inside the cabin the explosion and backfiring was givin me headache after 10 minutes. Just use some sort of resonator.. good luck a good aftermarket unit should do the job

[Riley2.4L]

yeah thanks to you all for the info

[InsanityInc]

3in is not too big for NA, exhaust flow is related to power levels, not aspiration or engine size (directly, anyway). There are plenty of graphs of a dyno for a NA KA with a 3" pipe gaining above 13whp from just the exhaust and losing nothing over stock.

[sunnys14]

just get a 3" exhaust and get it over with. 3" piping are too big for 1.8 liter hondas, but is GREAT for a big 2.4 liter nissan. 10+ whp gain!

[Bigvinnie]

Well DC sports has proved that 2-1/8" is the best for there pipe diameter,the collector is that size. Just header with no other mods it makes 8.8 additional HP at the wheels, and 7.7 ft/lb.s of torque.Hot Shots has proved that a 2.5" is the best for there pipe diameter.The collector is that size. Havent seen the results for myself, but the claim is that header with no other mods makes 9~10 additional hp, and 6 ft/lb.s of torque.So to me that would mean that you would want to tune your exhaust between those collector sizes. 2.15"~2.5".The exhaust is to be tuned to the size of all 4 exhaust ports plus 15% for proper tuning. That means on a KA it already surpases it's tuning at 2.5".Using a 3" pipe would lose power until the higher RPMS, it slows down the pulses and makes additional scavaging that decreases HP.Here is an interesting article to read that explains exhaust tuning.http://www.vmaxoutlaw.com/tech/exhaust.htmHere is a thread that I schooled people on as far as header selection.http://www.club240.com/forums/...25482

[raging panda]

yes, good job not reading other posts, or disreguarding them, what you say may be true, except for the part about it losing power in lower rpms, it doesn't it gains. i dont know if you make the same or close to the same power with 2.5 and 3 in exhaust, but i know that the dyno says that you dont lose power with 3 inches.

[Bigvinnie]

The one thing I have noticed on 3" exhaust on a stock trim KA engine is that the Torque band is scattered and isn't very smooth. It's not that relative in showing gains, but was an example that the KA does need a larger exhaust than stock OEM.Typically the KA exhaust ports arent ported to that of your average Nasport engine that has significant porting as well as higher lift and duration cams as well as larger fuel dumping to compliment the porting, and higher redlines.I find it extremely unecesarry to compliment a 3" exhaust especially when the KA is only using the sucking potential of a 60mm TB as well. The purpose of tuning the exhaust is to compliment the engine. From the cams, to the TB and even any possible headwork that is done. I think the exhaust should be used in such a manner to fine tune a equal Balance of HP/Torque ratio.An exhaust is typically used in a method of scavaging "NOT BACK PRESSURE" to regulate the power band or power output of the engine. Smaller diameters to compliment torque while larger diameters are to compliment HP.This would be as if it was the same debate over what header is better 4-2-1 or the 4-1. This will always be a never ending debate. All tuners chose to use there own savy to make there own engine design. All characteristics of each tuner are different as well as the scope of there engine....I leave with this note, bigger is not always best suited for all engine applications.

I actually did read everyones post and I agree with Scooby...The KA should deserve a 3" exhaust, but in my opinion, not in stock trim.

Modified by Bigvinnie at 11:01 PM 8/20/2005

Modified by Bigvinnie at 11:08 PM 8/20/2005

[InsanityInc]

The one thing I have noticed on 3" exhaust on a stock trim KA engine is that the Torque band is scattered and isn't very smooth, for example jump to this fresh alloy link http://forums.freshalloy.com/u...&vc=1. It looks like gains on the Dyno, but Alex even claims that he ran the engine cold, he states that HP and torque dropped when the engine was warm. It's not that relative in showing gains, but was an example that the KA does need a larger exhaust than stock OEM.

Uh, his car was probably slightly overheating, and the CTS was thus richening his fuel mixture, that's why the "hot" runs have an erratic curve. If I had to guess, I'd say he's probably running advanced timing, and imagine it would do the same regardless of the exhaust. You'll notice the first run on both stock and 3" exhaust have the exact same shaped curve.

[raging panda]

The one thing I have noticed on 3" exhaust on a stock trim KA engine is that the Torque band is scattered and isn't very smooth It's not that relative in showing gains, but was an example that the KA does need a larger exhaust than stock OEM.Typically the KA exhaust ports arent ported to that of your average Nasport engine that has significant porting as well as higher lift and duration cams as well as larger fuel dumping to compliment the porting, and higher redlines.I find it extremely unecesarry to compliment a 3" exhaust especially when the KA is only using the sucking potential of a 60mm TB as well. The purpose of tuning the exhaust is to compliment the engine. From the cams, to the TB and even any possible headwork that is done. I think the exhaust should be used in such a manner to fine tune a equal Balance of HP/Torque ratio.An exhaust is typically used in a method of scavaging "NOT BACK PRESSURE" to regulate the power band or power output of the engine. Smaller diameters to compliment torque while larger diameters are to compliment HP.This would be as if it was the same debate over what header is better 4-2-1 or the 4-1. This will always be a never ending debate. All tuners chose to use there own savy to make there own engine design. All characteristics of each tuner are different as well as the scope of there engine....I leave with this note, bigger is not always best suited for all engine applications.

I actually did read everyones post and I agree with Scooby...The KA should deserve a 3" exhaust, but in my opinion, not in stock trim.

Modified by Bigvinnie at 11:01 PM 8/20/2005

Modified by Bigvinnie at 11:08 PM 8/20/2005

awesome answer, im sorry if i seemed rude in my previous post, had you not posted this i would have felt justified in my doing so, but your reply was very well thought out and deserves to be recognized as such. its just you see so many guys not reading other peoples posts and talking like they know everything and whatever anyone else says is totally wrong since their friend who works at a shop told them so. anyways, good reply, good points, much respect to you

[Bigvinnie]

Uh, his car was probably slightly overheating, and the CTS was thus richening his fuel mixture, that's why the "hot" runs have an erratic curve. If I had to guess, I'd say he's probably running advanced timing, and imagine it would do the same regardless of the exhaust. You'll notice the first run on both stock and 3" exhaust have the exact same shaped curve.

There was nothing wrong with the car.... He mentions nothing of the ECU throwing codes....It's very simple, as the egr valve opens and tempratures rise in NOX, HP is decreased, as it goes through the intake mani.That is why you are told, "NOT" to run the engine cold on the dyno, it gives false results.....

[InsanityInc]

There was nothing wrong with the car.... He mentions nothing of the ECU throwing codes....It's very simple, as the egr valve opens and tempratures rise in NOX, HP is decreased, as it goes through the intake mani.That is why you are told, "NOT" to run the engine cold on the dyno, it gives false results.....

You do realize you have no ****ing clue what an EGR system does, right? It lowers NOx by reducing combustion chamber temperatures, as NO and NO2 are formed by reacting the oxygen and nitrogen inherent in the atmosphere, but the reaction requires a very, very high activation energy (high heat in the combustion chamber). By recirculating exhaust gas you reduce the amount of power the engine is making by diluting the intake charge, hence LESS temperature, not more, and therefore less NOx emissions. Not to mention it opens at 2000rpm regardless of engine temperature, so you're wholly and completely wrong. Good job.

If there were an A/F chart with the dyno (as there usually is, not sure why that one didn't have one), I 100% guarantee that his mixture was rich for those runs with the erratic graph, which is easily seen by looking at the graph with the silencer which becomes even more erratic and he specifically states the car was overheating in those cases. In case you were not aware, the coolant temperature sensor detects when your car is overheating, and if it detects that it is, the ECU richens your fuel mixture in an attempt to cool your engine down, which obviously makes your power production suffer, and will make it erratic as you will not have consistent combustion.

Do some research before telling me I'm wrong, it'll save me a lot of ****ing time.
Modified by InsanityInc at 5:06 PM 8/21/2005

[Bigvinnie]

Do some research before telling me I'm wrong, it'll save me a lot of ****ing time.

I never said you were wrong.........Like I said before you can select your own diameter based on the way you tune your engine. If 3" is what you like that is fine with me or anybody else.I do know how the EGR sysem works, that is also why I use EGR block off to gain HP..........

[InsanityInc]

I never said you were wrong.........Like I said before you can select your own diameter based on the way you tune your engine. If 3" is what you like that is fine with me or anybody else.I do know how the EGR sysem works, that is also why I use EGR block off to gain HP..........

Quote »It's very simple, as the egr valve opens and tempratures rise in NOX, HP is decreased[/quote]Based on that completely nonsensical statement, I have to disagree with the assertion that you know how an EGR system works.

[Bigvinnie]

This can be a never ending debate, then I should of also expressed the difference between open and closed loops, and the difference in A/F ratio as well. But the fact is I don't have all day to tell you what exhaust is better.........I was just using an example with those dyno graphs........I think with smaller diamter pipe the graph would of been SMOOTHER.

[ddgsxr504]

Well aside from all the bantering about who knows what about damn EGR valves , a 3" exhaust will work on your KA. I have a 3" Apexi N1 on my S14 and it runs great. I also have a hotshot header and 3" test pipe where the cat used to be. A 3" does not affect your power negatively, actually it gives you more power higher in the RPM band. I ran my car on a dyno with the stock exhaust and then with the 3" Apexi unit. The low-midrange power loss was almost visibly non-existent. You will lose a pony or two on the low end but you will also make anywhere from 10-15+ hp on the high end depending on other mods you may have. As for it being too loud my car sounds great at idle and is not that loud at WOT. The only downside is you get a slight hum inside the cabin while driving but that is only when you have the windows up. The best way to beat this is by buying a good unit such as HKS, Apexi, Greddy, Espiler or the like. The only reason that most "ricey" imports sound like they are about to blow up doing 35mph is because they have some cheap a$$ exhaust. Like you have heard before you get what you pay for.

[InsanityInc]

This can be a never ending debate, then I should of also expressed the difference between open and closed loops, and the difference in A/F ratio as well. But the fact is I don't have all day to tell you what exhaust is better.........I was just using an example with those dyno graphs........I think with smaller diamter pipe the graph would of been SMOOTHER.

No, it wouldn't. That's my damn point. The curve was not smooth on the subsequent runs because his car was overheating, causing the ECU to richen his fuel mixture. It had nothing to do with the 3" exhaust.

[Riley2.4L]

Well aside from all the bantering about who knows what about damn EGR valves , a 3" exhaust will work on your KA. I have a 3" Apexi N1 on my S14 and it runs great. I also have a hotshot header and 3" test pipe where the cat used to be. A 3" does not affect your power negatively, actually it gives you more power higher in the RPM band. I ran my car on a dyno with the stock exhaust and then with the 3" Apexi unit. The low-midrange power loss was almost visibly non-existent. You will lose a pony or two on the low end but you will also make anywhere from 10-15+ hp on the high end depending on other mods you may have. As for it being too loud my car sounds great at idle and is not that loud at WOT. The only downside is you get a slight hum inside the cabin while driving but that is only when you have the windows up. The best way to beat this is by buying a good unit such as HKS, Apexi, Greddy, Espiler or the like. The only reason that most "ricey" imports sound like they are about to blow up doing 35mph is because they have some cheap a$$ exhaust. Like you have heard before you get what you pay for.

Well in that case I was gonna go with the 3 inch and if I found it too loud would just go get a resonater. All you guys are giving me lots of info and things to consider. I saw on that post about aftermarket exhausts the other day some of you folks rides and I really like the look of the Apexi N1. As for the hum I might hear with 3 inches I'm used to that. I used to drive my dads '92 fairlady Z32 TT with even bigger exhaust. Any way the stereo in my S14 will drown out the hum.

[titanium240]

Hotshot header and BRM 3" SS w/ 14" resonator. Built custom for the KA. 'Nuff said.

Go ahead and flame each other to death while I laugh at the uselessness of this thread, I'm out!

[ddgsxr504]

Instead of getting a resonator on your 3" exhaust you can just get a baffle that bolts inside the tip. Like my Apexi unit there is a whole drilled into the tip on the bottom and they sell a baffle that bolts into the tip that deadens the sound.
Modified by ddgsxr504 at 7:48 AM 6/28/2006

[Riley2.4L]

Oh reallyy? So is that cheaper than buying a resonator