Nismo Cat Back

Jessobear · 03-10-2011, 07:24 AM

There is no compelling evidence that any of the aftermarket exhausts out there give you much more than a few HP over the Nismo. In other words, if you had a car with intake, exhaust and tuning, you most likely will only see a few hp from one of the louder aftermarket exhausts.

It really boils down to whether or not you like the sound of the 370Z uncorked. The only aftermarket exhaust I've heard is the GReddy Ti-C (without the silencers) on stock cats and I thought it sounded terrible and ricey. This was when I was buying my OEM Nismo, which I paid $450 for from the guy who put the Ti-C on his car.

The OEM Nismo is barely louder than stock, at least from inside the car. I later added Fast Intentions resonated HFC's and the sound level barely increased. Not too sure what the car sounds like from outside, although from inside my underground parking garage, it is definitely noticeably deeper and louder when I start the car up. Were I to do it again, I'd probably go for resonated test pipes (resonator gets rid of a bad exhaust rasp at ~2700 rpm, right where you cruise a lot).

Bang for the buck, you absolutely can't go wrong with a take-off OEM Nismo. Add the resonated test pipes and a Stillen Gen 3 intake and you'd probably have a really nice sound under throttle. The nice thing about getting your sound from an intake is that it only makes a bunch of noise at WOT, so the car is still very quiet for cruising.

bigZ · 03-10-2011, 08:40 AM

That is sound advice. ha!

thanks a bunch.

chops · 03-10-2011, 04:44 PM

there is definitely rasp if you add test pipes (resonated or not) or high flow cats to the nismo exhaust. i believe the H pipe is the culprit here. the new cats/tp's go from 2.5" pipe to the 2.25" flex pipe flanges, which end at 2" to the midpipe/resonators.

a member in the nismo forum said he added a custom 2.5" x-pipe which got rid of all his rasp. im determined to go this route as well...as soon as someone makes one!

Nikkolai · 03-10-2011, 05:34 PM

Quote:

Originally Posted by chops

there is definitely rasp if you had test pipes (resonated or not) or high flow cats to the nismo exhaust. i believe the H pipe is the culprit here. the new cats/tp's go from 2.5" pipe to the 2" flex pipe flanges, which open upto 2.25" to the midpipe/resonators.

a member in the nismo forum said he added a custom 2.5" x-pipe which got rid of all his rasp. im determined to go this route as well...as soon as someone makes one!

What about those cheap Y-Pipes from Ebay coupled with the rest of the Nismo exhaust? I do not mind the rasp if it goes away upon warm up.

chops · 03-10-2011, 06:34 PM

Quote:

Originally Posted by Nikkolai

What about those cheap Y-Pipes from Ebay coupled with the rest of the Nismo exhaust? I do not mind the rasp if it goes away upon warm up.

a Y-pipe will not work..only the stock Z has 2 catalytic converters joined to a single pipe. nismo owners will require an X-pipe

Nikkolai · 03-10-2011, 11:22 PM

Quote:

Originally Posted by chops

a Y-pipe will not work..only the stock Z has 2 catalytic converters joined to a single pipe. nismo owners will require an X-pipe

Yes, that is my fault. It was totally obvious. I guess the late shifts I had this week is taking a toll on my brain, lol.

Jessobear · 03-10-2011, 08:02 PM

Quote:

Originally Posted by chops

there is definitely rasp if you add test pipes (resonated or not) or high flow cats to the nismo exhaust. i believe the H pipe is the culprit here. the new cats/tp's go from 2.5" pipe to the 2.25" flex pipe flanges, which end at 2" to the midpipe/resonators.

a member in the nismo forum said he added a custom 2.5" x-pipe which got rid of all his rasp. im determined to go this route as well...as soon as someone makes one!

I have the Nismo OEM exhaust with FI resonated HFC's and I can definitely tell you that my car does not have any noticeable exhaust rasp.

I also find it funny that everyone really gets on the piping diameters of the H pipe. Having stepped piping sizes is actually totally normal and can actually aid in the scavenging effect of the exhaust system. Think about this in terms of total cross-sectional area: passing the exhaust through two 2" diameter pipes is a greater cross-sectional area than passing through a single X or Y pipe.

The advantage of an X pipe has nothing to do with cross sectional area. It has to do with easier flow between the two sides of the exhaust due to a smoother transition compared with an H pipe. An X pipe will also have the effect of making the exhaust quieter from noise cancellation due to the easier cross flow of the two legs. The H pipe configuration is not a bad design in essence, which is why people have only seen small gains from other exhaust systems.

Here's a decent link about putting an X pipe exhaust system on a car:

Exhaust System Installation H-Pipe, X-Pipe,- Car Craft Magazine

chops · 03-10-2011, 08:59 PM

Quote:

Originally Posted by Jessobear

I have the Nismo OEM exhaust with FI resonated HFC's and I can definitely tell you that my car does not have any noticeable exhaust rasp.

I also find it funny that everyone really gets on the piping diameters of the H pipe. Having stepped piping sizes is actually totally normal and can actually aid in the scavenging effect of the exhaust system. Think about this in terms of total cross-sectional area: passing the exhaust through two 2" diameter pipes is a greater cross-sectional area than passing through a single X or Y pipe.

The advantage of an X pipe has nothing to do with cross sectional area. It has to do with easier flow between the two sides of the exhaust due to a smoother transition compared with an H pipe. An X pipe will also have the effect of making the exhaust quieter from noise cancellation due to the easier cross flow of the two legs. The H pipe configuration is not a bad design in essence, which is why people have only seen small gains from other exhaust systems.

Here's a decent link about putting an X pipe exhaust system on a car:

Exhaust System Installation H-Pipe, X-Pipe,- Car Craft Magazine

Quote:

For any performance exhaust system, some type of crossover connecting the two sides of a dual exhaust system is important because it acts to balance the two banks of the engine. The common H-style crossover is good at balancing sound pulses between the two halves, but does little to promote scavenging because the exhaust gases tend to follow the path of least resistance, which is straight through each pipe rather than taking the 90-degree turn through the H-pipe into the other half of the system. In an X-pipe system, however, where the two sides of the system intersect, the gasses have no choice but to intermingle as they pass through the junction. This promotes improved scavenging effects by smoothing out uneven exhaust pulses from the engine’s firing order. It also helps quiet down the exhaust, resulting in a mellower, less raspy tone. According to Magnaflow, the faster acceleration of the gasses through an X-pipe causes them to flow in a linear fashion parallel to the walls of the tubing rather than tumbling. This “laminar” flowing gas is much quieter than tumbling gas, resulting in an exhaust tone up to 8 decibels quieter than a traditional H-pipe.

this is fine by me! more power, less rasp, cant go wrong with the X-pipe..

Jessobear · 03-11-2011, 08:38 AM

Quote:

Originally Posted by chops

this is fine by me! more power, less rasp, cant go wrong with the X-pipe..

Which is why if I were to recommend an aftermarket exhaust, it would be the Fast Intentions (even though I really hate the look of having the visible polished/angled mufflers under the car). All I'm saying is that even with the H-pipe in my OEM Nismo exhaust, I'm not getting any raspiness. This may be because of my resonated HFC's, which as far as I can tell I'm one of two people on this forum to own, the other guy being in Australia. Perhaps removing either the cat part or the resonator part (which would describe the setup that 99% of the people here have) induces some raspiness that I'm not getting.

chops · 03-11-2011, 01:45 PM

Quote:

Originally Posted by Jessobear

Which is why if I were to recommend an aftermarket exhaust, it would be the Fast Intentions (even though I really hate the look of having the visible polished/angled mufflers under the car). All I'm saying is that even with the H-pipe in my OEM Nismo exhaust, I'm not getting any raspiness. This may be because of my resonated HFC's, which as far as I can tell I'm one of two people on this forum to own, the other guy being in Australia. Perhaps removing either the cat part or the resonator part (which would describe the setup that 99% of the people here have) induces some raspiness that I'm not getting.

yea..ive already approached fast intentions in hopes that they will create an X-pipe for us nismo owners

Rooskey · 03-12-2011, 01:46 AM

Quote:

Originally Posted by chops

this is fine by me! more power, less rasp, cant go wrong with the X-pipe..

Actually an X pipe works as a vacuum on the exhaust side. The crossover helps pull the exhaust out. Kinda like using vacuum on the intake side to run power brakes or opening up throttle bodies. It helps helps pull the oxygen through the engine. (Add's power)

6spd · 03-11-2011, 03:57 PM

Ive gotta disagree on the piping size, the s-tune is much larger that stock, especially at the y-pipe choke points and flex pipes.

GZ3 · 03-11-2011, 04:10 PM

^^ true it is larger

03-10-2011, 07:24 AM	#1 (permalink)
Jessobear Base Member Join Date: Oct 2010 Location: Washington, DC Posts: 201 Drives: '10 370Z Tour/Sp M6 Rep Power: 16	There is no compelling evidence that any of the aftermarket exhausts out there give you much more than a few HP over the Nismo. In other words, if you had a car with intake, exhaust and tuning, you most likely will only see a few hp from one of the louder aftermarket exhausts. It really boils down to whether or not you like the sound of the 370Z uncorked. The only aftermarket exhaust I've heard is the GReddy Ti-C (without the silencers) on stock cats and I thought it sounded terrible and ricey. This was when I was buying my OEM Nismo, which I paid $450 for from the guy who put the Ti-C on his car. The OEM Nismo is barely louder than stock, at least from inside the car. I later added Fast Intentions resonated HFC's and the sound level barely increased. Not too sure what the car sounds like from outside, although from inside my underground parking garage, it is definitely noticeably deeper and louder when I start the car up. Were I to do it again, I'd probably go for resonated test pipes (resonator gets rid of a bad exhaust rasp at ~2700 rpm, right where you cruise a lot). Bang for the buck, you absolutely can't go wrong with a take-off OEM Nismo. Add the resonated test pipes and a Stillen Gen 3 intake and you'd probably have a really nice sound under throttle. The nice thing about getting your sound from an intake is that it only makes a bunch of noise at WOT, so the car is still very quiet for cruising. Last edited by Jessobear; 03-10-2011 at 07:26 AM.

03-10-2011, 04:44 PM	#3 (permalink)
chops A True Z Fanatic Join Date: Oct 2010 Location: NA Posts: 1,732 Drives: NA Rep Power: 23	there is definitely rasp if you add test pipes (resonated or not) or high flow cats to the nismo exhaust. i believe the H pipe is the culprit here. the new cats/tp's go from 2.5" pipe to the 2.25" flex pipe flanges, which end at 2" to the midpipe/resonators. a member in the nismo forum said he added a custom 2.5" x-pipe which got rid of all his rasp. im determined to go this route as well...as soon as someone makes one! Last edited by chops; 03-10-2011 at 06:35 PM.

03-11-2011, 03:57 PM	#12 (permalink)
6spd A True Z Fanatic Join Date: Aug 2009 Location: South Florida Posts: 3,001 Drives: Q50RS Rep Power: 26	Ive gotta disagree on the piping size, the s-tune is much larger that stock, especially at the y-pipe choke points and flex pipes. __________________ -Jay- jonathanjamesphotographer.com

03-11-2011, 04:10 PM	#13 (permalink)
GZ3 A True Z Fanatic Join Date: Dec 2009 Location: SATX Posts: 3,296 Drives: Z Rep Power: 23	^^ true it is larger __________________ 09 GT-R 12' 370Z 7AT HANDED DOWN 12'+13' 5.0 SOLD

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03-10-2011, 08:40 AM	#2 (permalink)
bigZ Base Member Join Date: Feb 2011 Location: Austin TX Posts: 76 Drives: 2010 370z Rep Power: 16	That is sound advice. ha! thanks a bunch.