Question on exhuast systems, Trying to learn

[ZMEDIC13]

I'm considering going turbo or supercharger in the future but currently I'm running NA and I am looking into getting an exhaust. I've been to youtube and listened to sound clips, that's not my question. I was wondering if I shoul wait to upgrade my exhaust after I get my FI whichever it may be or should I just get one now? Also do you need an exhaust made for turbo'd or supercharged engines or could you use any aftermarket exhaust? My concern is I don't want to by an exhaust now and then have to buy another exhaust later when I go FI. Any help would be great. Thanks to all who give help. Sorry if this is a dumb question, I'm still learning.

[evildky]

if you go turbo you'll get the best performance from a true straight through muffler, otherwise a baffeled muffler will be fine, sport Z (now nissan sport)magazine has done comparo's I don't recall who got what but se sure to read through various posts in this section to see what others are running and what their results have been

[rmezz13]

the main thing i would worry about as far as exhaust is - headers, testpipes/HFC (high flow cats). I feel a cat back would be fine, i mean you could go turbo on stock exhaust if you wanted, the kits come with the exhaust manifolds you need (turbo). As far as SC, you could do basically what ever you want and it won't affect your SC install (headers and all). The turbo runs off of your exhaust gases and requires a special exhaust manifold that the turbo mounts to, so any header up grade will have to be replaced. I would think you would be fine with any cat back.

Any questions on turbo/sc ask.... I will try my best with both, but evil is the turbo guru.....

[ZMEDIC13]

When you have a turbo and you take your foot off the gas the turbo is still spinning and creating boost and and you have to have a bypass to get rid of the extra exhaust so you don't put too much strain on the throttle body(?) or the turbo or something like that, but my question is where do you direct the extra exhaust? I heard somewhere about redirecting it through the MAF maybe to maintain proper air fuel ratio. Can you explain, I think I may have gotten some things mixed up. Sorry I'm still learning and trying to keep things straight.

[rmezz13]

the boost pressure is released through a BOV (blow off valve) on the intake piping, and also through the wastegate on the turbo. When you let off the gas the extra boost pressure will release through a BOV thru the intake (same with SC)..... i can't really get more into depth hopefully evil or someone else will chime in if that doesn't explain enough....

anymore questions i'll do my best!

-Ryan

[KakkoiiRacing]

When you have a turbo and you take your foot off the gas the turbo is still spinning and creating boost and and you have to have a bypass to get rid of the extra exhaust so you don't put too much strain on the throttle body(?) or the turbo or something like that, but my question is where do you direct the extra exhaust? I heard somewhere about redirecting it through the MAF maybe to maintain proper air fuel ratio. Can you explain, I think I may have gotten some things mixed up. Sorry I'm still learning and trying to keep things straight.

woa, okay. you have a few things mixed up here. if i were you, i'd go to howstuffworks.com to learn a little more about how FI really works. essentially, your PA (power adder [turbo or super]) will add extra, charged air into your intake manifold/plenum. with a turbo, for example, when you let off the accelerator the compressor will keep spinning and forcing in air. the engine does not use this air so it tries to find another way out. air tries to escape to the easiest way and this is the same place it came in, the turbo. this will cause a stuttering of the compressor wheel called compressor surge (BAD). to combat this, you use a blow off valve or bypass valve. this relieves the pressure from your intake system and gives your turbo a longer life. in recirc cases, the air flows back into the intake bc the maf reads it as metered air. if you atmosphere vent, the metered air goes out of the system and causes the maf to tell your engine that bad things are occuring so it stalls. okay, so here is your exhaust answer. you can most certainly use your stock exhaust system with a turbo kit. most companies use downpipes in their kits that exit where your stock system starts (all aftermarket use this location too). the wastegate(s) will usually have dump tubes which kinda sound like crap. the best thing you can do in this case is to modify whatever exhaust you have to be able to accept the exhaust dumps from your wastegate(s). the exhaust does NOT get sent back to your maf. i'm trying to speak here in laymen's terms so if there is anything you're unsure about, SEARCH SEARCH SEARCH. just look at other sites for more in depth explanations on how FI works. hope this helped

[evildky]

kakkoii pretty much covered it

and to clarify on the SC setups they use a BOV in the same way, when the throttle shuts and there is vacume in the iintake manifold the bov opens and all the pressurised air in the inlet piping blows out or is recirculated, a SC boost is regulated by the pulley used and has no wastegate

and I believe most off the shelf turbo kits use internally gated turbo's with the excess gasses being routed back into the exhaust, and older systems running less boost didn't use BOV's, at low levels the compressor seurge wasn't real noticable but it does take stress off the turbo and keeps the turbo spooled between shifts

[C-Kwik]

I'd be less concerned about choosing an exhaust now if you were planning to S/C the motor. S/C motors will flow more air than N/A but will simply have higher pressure air of the same volume leaving through the exhaust pipe and have little effect on the power. A slightly bigger exhaust than would be used in N/A form is usually the sweet spot for S/C, but a good aftermarket N/A exhaust will work fine.

A turbo motor on the other hand operates primarily on a pressure differential before and after the turbine of the exhaust. The wastegate diverts flow as needed to maintain boost, which effectively regulates the pressure differential across the turbine. But since it is the change in pressure that makes such a big difference, that means that lowering the pressure after the turbo by providinf a better flowing exhaust will mean that the pressure before the turbine can be lowered as well. This results in lower backpressure to the motor which frees up power and reduces any effects of reversion that is caused by excess backpressure. This is why turbo motors can have some profound gains by simply changing the exhaust.

The simple rule with turbo motors is get the most free flowing exhaust you can (perhaps biggest diameter piping) that will fit and your ears can bear for the most power. Of course, the actuality is quite a bit more complicated, but as a general rule, this works.

I'd say if FI is a definite plan, but you are unsure of which (S/C or turbo), then wait on getting an exhaust until you are sure. A turbo exhaust generally uses some rather large piping and can reduce exhaust gas velocity at low to mid RPMs which can cause a drop in low to mid range torque.

[JDMZ32]

threads like this are why i love nico

The simple rule with turbo motors is get the most free flowing exhaust you can (perhaps biggest diameter piping) that will fit and your ears can bear for the most power.

this confused me. i thought bigger diameter exhausts were generally a lot quieter. my friend has a 3" apexi N1 exhaust on his KA-T S14 and it's very quiet. very deep, but quiet.

[KakkoiiRacing]

it all kinda depends on the setup of the exhaust.the apexi n1 has both a resonator and a fairly good muffler so it should be quiet.things like catalytic converters, resonators, muffler designs and pipe bends all factor in on how the sound resonates throughout the exhaust piping. the wall thickness and metal type also factors in, which is why titanium exhausts sound a lot different than a stainless steel variant of the same model.GENERALLY speaking, a larger piping size will lead to a louder, deeper, and raspier note. but when a turbo is thrown into the equation, exhaust theory changes a little as the turbo will act like a small muffler itself after the turbo manifold.the only way to determine if the pipes are gonna be obnoxious is to look at1) N/A or FI2) Cats or none3) Pipe Diameter4) Resonator or no (they give the exhaust a deeper and smoother/quieter sound)and5) Muffler design

It all kinda depends but it's better to look to youtube or to customer opinions (ie search NICO for opinions from people who have the exhaust).

^^^This also got kinda irrelevent but it's a little FYI