aftermarket exhaust

[BBQdDude]

2013 370z nismo NA

 

Just a fun driving car, no huge mods.

 

Looking at exhausts. Current is 2.5 inch diameter. I am looking at a 3.0 one. I like a deeper tone. Hence why I like this one.

 

My issue (?), everyone is saying only go 3 inch if TT or SC. Is there a downside going to a 3.0 inch from a 2.5. I figure it will have a more 'raspy" tone. Other than that downsides???

[Geeto67]

here is my 2 cents from working with motorcycle exhausts...

 

Generally the diameter of the pipe controls exhaust gas velocity. When you hear about people putting big exhaust on something like their harley or SBC and then complaining they lost power because they removed the backpressure they are sort of right, they caused the engine to work less efficiently because they slow the exhaust gas velocity down. Some cars and bikes have a smaller diameter pipe than necessary to help emissions and speed up exhaust gas velocity so going to a larger pipe in conjunction with enriching the mixture has a positive effect, but if the people who know these cars are saying only use 3" when the car is supercharged/turbo then they are saying 3" is too big and only works in a situation where exhaust gas velocity is less critical (like under pressure).

 

If you want to change the noise, just experiment with different mufflers. That is where all the science of engineering sound is spent. Sure the pipes do add something to the sound, but it's the muffler, the piece that is designed specifically to limit sound, that has the greatest effect.

 

Sorry that I can't help more by saying "use 'x' muffler" but this line of thinking should get you on the right track.

[Tim Davis]

With all of the members of the Ohio G/Z club that are local, I would think that you could likely hear any combination of what is available via the aftermarket. This way you could base your decision on sound and actual feedback from the owner's.

 

That being said, you could also inquire with ZSpeedPerformance.com in Vandalia (Dayton), they stock many of the aftermarket systems that you could see first hand and likely save on shipping cost.

[pontiacfreak142]

Pretty much what geeto said. If you go too big, you lose back pressure. Depending on how big you go and how far forward (towards the engine) you go, it can make a noticeable difference. Like my firebird for instance, when i put a cut out on that car, i was told i wanted it as close to the engine as possible. Bad idea. I put it where the cat used to be, and when you would unbolt it, you could tell there was a loss in torque.

[POS VETT]

I wouldn't go with 3" exhaust, there is a range of annoying noise produced by the engine right at the range of highway-cruising speed.

 

If you're interested, I have a NISMO S-Tune catback exhaust sitting in my garage attic.

[BBQdDude]

Thank you all for that explanation. It makes perfect sense. 2.5 I guess it will be and I will pay attention to the muffler more so.

[BBQdDude]

With all of the members of the Ohio G/Z club that are local, I would think that you could likely hear any combination of what is available via the aftermarket. This way you could base your decision on sound and actual feedback from the owner's.

 

That being said, you could also inquire with ZSpeedPerformance.com in Vandalia (Dayton), they stock many of the aftermarket systems that you could see first hand and likely save on shipping cost.

 

I never get out lol. Too much work. I keep trying to go to a meet.

 

I bought my clutch and external slave from him. Hell of a guy.

[Draco-REX]

Gas velocity only matters to a N/A car for exhaust scavenging. Like a wind instrument, the exhaust is "tuned" a particular way so that the resonnance causes more exhaust to be pulled from the cylinders. (A similar thing is done with the intake, but we're talking exhaust here.) A higher "pitch" works best at the top end, lower pitch for the lower end of the power band. Obviously we're not dealing with actual musical notes, but the principle is the same. So changing to a larger diameter pipe will lower the "pitch" of the exhaust. If you're not musicaly inclined, take two bottles of different size and blow across the top, then think about how your engine sounds near red line vs cruising around town. Now the bigger and lower exhaust will still have a scavenging effect, but now that resonnance will be at an RPM that is outside the engine's power band; hence the power loss.

 

Exhausts, as I mentioned earlier, are not musical instruments. They aren't designed to hold a note; they're designed to guide exhaust away from the passenger compartment and things that burn. So the exhaust pulses that make the scavenging effect happen will become distorted and lose their power the further they get from the engine. Throw a catalytic converter in the way and they won't have much more power after that. Which is why once you eliminate restrictions in the exhaust (cats, mufflers, excess bends) the best place to find power is in the headers.

 

Now, here's the the big question: How much of your exhaust are you looking to change? If you're just doing a cat-back, go as big as you like. You'll only gain power as you reduce restrictions. If you're doing a cat back and eliminating cats in the exhaust pipes, then I would consider staying close to stock diameter for the test/track pipes, then going full bore with your cat back. If you're going from the heads back, I'd do some SERIOUS research into your headers with real-world examples to back up any claimed torque gains.

 

tl;dr: If you're just replacing a cat back to get more sound, don't worry about exhaust sizing, get what sounds best.

[BBQdDude]

Now, here's the the big question: How much of your exhaust are you looking to change? If you're just doing a cat-back, go as big as you like. You'll only gain power as you reduce restrictions. If you're doing a cat back and eliminating cats in the exhaust pipes, then I would consider staying close to stock diameter for the test/track pipes, then going full bore with your cat back. If you're going from the heads back, I'd do some SERIOUS research into your headers with real-world examples to back up any claimed torque gains.

 

tl;dr: If you're just replacing a cat back to get more sound, don't worry about exhaust sizing, get what sounds best.

 

I was thinking some arte test pipes, then HFC, then CBE to top it off.

[99StockGT]

If you aren't in the Ohio G/Z/GTR Club that would be the first place to join up, there are literally hundreds of central Ohio members with all sorts of exhaust setups. As Draco mentioned, if you are just doing cat back it's mostly just noise you are changing not any actual exhaust flow so do whatever you like.

 

Now when we are talking cat deleted/test pipes/headers that sort of thing keep in mind not only are you changing exhaust flows but your stock ECU will NOT be happy about what's been done. A tune will be necessary to a) get rid of the Check Engine Light and b) Actually show you some gains from the now much more free flowing exhaust.

 

Specific to the VQ motors the G/Zs have under the hood, do you like their signature "warble" or no? Keep that in mind when hunting for exhausts some actually get rid of that sound while others accentuate it.

[nismopc]

Just my thoughts. It's been proven time and time again that 3" exhaust performs very well on the VQ35's. There are several Maxima/Altima dyno's performed on the forums I belong to that back this statement.

 

I would assume the same goes for the VQ37. Not familiar with the changes between the two, but I have a '08 Altima 3.5 6MT with Racingline y-pipe and "knock-off" 3" stainless cat-back exhaust (with resonator). Originally output to 2.5" inlet dual ricer watermelon shooters with 4" tips . Looked less than desirable and the cans had NO packing or perforated core. Too loud even with silencers in tips, so I am running stock 2" inlet axle back mufflers. Slight gurgle sound from exhaust and no in cabin drone.

 

It eliminated the 3rd cat. Performance gains were quite noticeable.

[nismopc]

More to chew on:

 

Are the aftermarket 370Z true dual? If so, then 3" would be too large as N/A. The Altima goes from the downpipes to a y-pipe and run's a single pipe back to rear where it then splits back out to two mufflers. Maybe reason why 3" is so successful on these FWD cars.