S14DB

The construction of the mufflers make a major difference over any size difference.

Big oval cans are going to be a lot quieter and better tone then an N1 or glass pack.

Cat's help a lot. If you can't run one at least have a resonated test pipe. Then a resonator and muffler.

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Comments should be taken as Opinions not as Statements of Fact

hsitko

Apexi Noir
there is a video clip of it in a 240 on youtube. Sounds great.
As for the 2.5 to 3 in debate. Wow. So horsepower is made by how much cfm will flow through and engine. Basically. So if you decrease back pressure you increase how much cfm the head can flow. The reason for back pressure is to artificially increase compression since not all the exhaust will escape. By going to 3 in on an na setup you typically see a small loss in low to mid range torque and a small gain in top end power due to increased flow potential. I love how the people who had so much trash to talk about 3in on an na ka are no where to be found no that proof was posted. Lol or should i say roflkoptor.

Weedm

you bumped a 2 month old threadddd.

anywho ka's can sound nice.. i love my 3inch kakimoto.

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bmoses

WTF? Did you just make this up?

hsitko

No. If all the exhaust cant get out of the combustion chamber there is more "air" or exhaust in the chamber before the next intake stroke. Keep in mind, when an intake stroke happens it does not completely fill the combustion chamber to maximum capacity. The more that is in the combustion chamber the more compression you get. Like i said it increases your compression. It does not increase your mechanical compression. That isnt possible. But it does increase the combustion pressures and hence compression. You might want to make sure that you completely understand how an internal combustion engine works before you call me out on this kind of thing.

lalo167

Nurspec sounds sick on ka's!! and Noir is supper quiet!

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bmoses

I understand how an internal combustion engine works and dynamics behind them. I think you are wrong. Latent exhaust gas that hasn't been discharged from the engine will result in a lower VE (volumetric efficiency, or the amount of combustible air/fuel available in the cylinder relative to the displacement of the cylinder). Leftover exhaust gas that has not escaped will do nothing to increase your power anywhere in the RPM range at any time. All leftover exhaust gas will do is dissallow or displace more fresh air and fuel from getting in. Obviously it will not increase your mechanical, or static, compression. It will also not increase your dynamic compression. What your talking about is more like EGR. Exhaust gas in the cylinder is inert and not combustible and lowers exhaust gas temps, which lowers NOX emmissions. This is why there is an EGR system on our cars.

The issue at hand was backpressure. Backpressure is not necessarily something that is desired. Backpressure is never a good thing. However backpressure is a result of having smaller diameter exhaust tubing which is necessary to create strong exhaust pulses and exhaust velocities at midrange RPMs. The downside is that the smaller diameter tubing becomes a bottleneck at higher RPMs. It's the strong exhaust pulses and velocities which create effective scavenging at lower to mid RPMs, not the backpressure. Backpressure is just a result of having smaller sized tubing and is a necessary evil that can't be avoided.

klits562

I think hes right.....

hsitko

Firstly, having exhaust in the combustion chamber does not mean it will displace oxygen and fuel. Like i said a compression ratio is only a best case scenario. VERY BEST CASE. It is truthfully dependent on a lot of things. So keep in mind that when your engine is running its not running to its full potential almost ever. So having some exhaust in the chamber because of high back pressure means one thing basically. A leaner mixture in certain rpm ranges. You do know what a leaner mixture will do right? It will increase torque. This might be a different story if this car had a wideband stock that the ecu could add fuel with if it saw a leaner than normal mixture. But it cant. It only reads grams per second of oxygen which will not change if you dont expel all your exhaust and run lean. Keep in mind i'm not talking massively lean here. Only a little. And like i said. Its a small amount of torque and a small amount of horsepower i'm talking about here. Seriously less than 5 on average. An engine does not fill the combustion chamber to its maximum potential while the engine is running and thats a fact. Truthfully exhaust velocity is probably the biggest factor here. There are some fancy systems that have variable exhaust runner systems. One for high velocity at low rpm's and then one that opens up at higher rpm's to keep the velocity up with the increase of flow. Ceramic coating also helps. This is an interesting conversation i think. Good exhaust velocity will cause a good scavenging effect for sure. I really wonder how much time header producers spend on making a well engineered header. If you look at companies that make header parts like collectors there is some really fancy exhaust parts that you almost never see on name brand headers. Makes me kind of want to experiment on making my own.

chiboy002

try 2 2.5" pipes running back from the headers, nothing else. i cant hear shit anymore

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street dancer.

T-FAST

2.5 piping, highflow cat, vibrant resonator, vibrant streetpower muffler

If you don't like the vibrant muffler look at the apexi ws2

bmoses

Absolutely it means that air and fuel are displaced.

I'm not sure how you are relating compression ratio and un-evacuated exhaust from the chamber. Neither static, nor dynamnic compression, or compression measured in any other way will be changed or affected by exhaust being left in or fully expelled from the chamber.

I agree with this. Aside from WOT your engine is constantly being starved of air/fuel mixture by the throttle plate. And even at WOT there's likely only a small sliver of RPM rev range in which you're engine will attempt to reach 100% VE. In reality it will probably be something less than 100%.

This is where you lose me. I believe that your theory on this is flawed. Your mixture could not possibly be leaner with additional exhaust in the chamber. Exhaust has had it's oxygen used up already and is inert, cannot be burnt anymore. Therefore, if there was additional exhaust in the chamber that was not scavenged because, lets say, your RPMs were too low or too high this would be metered either by your MAF system or it would have been programmed into the ROM to your speed density system's VE map lookup table by a calibration engineer at the OEM in question. Either way, exhaust left in the chamber is simply one of they many ways in which VE does not equal 100%

Actually from my tuning experiences with a wideband, I find that an AFR of just under 13.0:1 (12.8:1 - 12.9:1) on gas creates the best torque from peak torque to peak HP, and then further richen after that for safety.

@6.5psi, I'm finding a lambda of about .85 from peak torque to peak HP feels good. In this case I'm on E85

These are my experiences with my KA, both N/A and turboed. When you say lean mixture, I'm not sure what you mean since you didn't add any points of reference to your story.

We are talking about WOT conditions here where VE is at peak for a given engine. Under these conditions a conventionl narrowband O2 sensor is disregarded and the ECU is running in open loop with an additional long term trim modifier added to the equation. In this case the ECU is running off of a target AFR table where values have been stored (again by a calibration engineer at a given OEM) as to how much fuel to add/modify by at a given load and rpm.

From my experience our Nissan ECU's don't convert or scale to grams per second of air (not oxygen), fuel or any other . It's a more simple 8 bit or 16bit load value. However, for the record, I will comment on this. If you don't expel all of your exhaust, your VE will be lower than if you did. In this case, this would be metered by your MAF since less air is able to enter your engine.


Well we do agree that an engine rarely if ever hit 100% VE. I'll add that this is assuming WOT. From what I have read, forced induction will cause an engine to get closer to and possibly hit 100% or greater VE (greater than 100% would be completely unburnt, unused air/fuel mixture out the tailpipe).

OP, sorry for threadjacking. This will be my last post of this nature.

hardtime21

If you're still looking, just throw a HKS High Power Exhaust on it and keep it moving! Sounds Deep and Throaty without the raspy crap and fits like a glove for a NA or Forced KA! I'm running a ISIS GT Single for the S14 that I bought from Billy on this forum's marketplace. It's a nice setup as well but my friend has the High Power and it sounds "Intimidating!"

bmoses

+1 for the HKS. I have an HKS Dragger 2 and I believe the pipe size is 65mm ~ 2.5" and the exhaust note was great N/A and it's damn near stock quiet with the turbo. Yet the system is totally free flowing as I noticed by looking straight through the muffler. All the bends seem to be as shallow as possible and the quality is great. I've had this exhaust for going on 6 or 7 years and it's still resisting rust and has all of it's coating still on. Also its fitment in bolting on with dead on. I couldn't have been happier with this exhaust system.

DEEPfrom1

My exhaust is 3" stainless from the turbo back to a 3" stainless catback (no cat) the apexi axle back was removed in favor of a 3" stainless straight pipe with a tig welded pie cut turn down. Only "sound dampening" comes from the middle resonator in the apexi exhaust, thats it no cat and no muff. NY cops don't ever pull me over, its loud, and rumbles and shoots flames, but they stopped harassing me as soon as the apexi cannon was circumcised, man the cops are dumb.