I am looking to pickup a 2004 350z 6mt enthu. in the near future.

Having looked at many of the exhaust choices on the board I think I will be opting for the custom route which is what I did in my last car.

My question is what is the largest size (diameter) pipe you can run from the cat-back? Looking to staying rear dual in the 4inch exit range.

I see a lot of 2.5 inch cat back pipes. I was thinking of getting a custom 4 inch cat back made using magnaflow mufflers with rear duals.....will this work?

What potential hp/tq gains will I see?

FYI I ran a full 3 inch turbo back custom on my previous car....Audi A4 which put 300hp to the wheels.....so I am not a n00b to turbos/FI/high hp applications so please save the n00b comments for someone else.

Also I have searched the forum and just found a bunch of over priced packaged kits......

I am not looking for Ti. I would be using SS from the cat back and right now I do not foresee going FI...saving money to buy an engagement ring.

Anyway all help is appreciated....

 

man... i dont have any help tips or anything.. but please post pictures of what this will look like... and keep me posted

 

If there was a idea combination for every Z, we would all be running the same exhaust. Since you mentioned that you build custom exhaust, you know that every intake and exhaust mod will alter horsepower and torque curves. Few have the resources to build, test, modify, test, modify. The generic exhaust, say Injen, has been tested and proven.

Building from scratch is a guessing game. For all-motor, 4 inch inner diameter pipes if overkill. For one, where are you going to find a header with a 4 inch collector?

 

Considering 3" dual is good enough for most people on these boards running F/I, I don't see why 3" dual would be insufficient for N/A. It might already be overkill, remember stock exhaust is 2.5" at the midpipe. 3" dual will have a cross sectional area of 2.8 times the stock exhaust. If you're not even doubling the airflow, why make the exhaust almost 3x as big?

 

You are not going to gain anything out of an exhaust except sound on this car.

I would just buy a single in dual out muffler and call it a day. I had a flowmaster on my Z for the longest time. It sounded better than any other exhaust system I have ever heard in person. It also only cost about 120 bucks for the whole thing.

 

I was also going to build custom headers which is what I had to do with my Audi.

I know I did say all motor but in the future if the car holds up well I may put a big turbo on the motor. When I mean big I mean very large.....at that stage the motor will be fully built.

I am just trying to not make this car a money pit which is what happened with my previous car. I went pretty crazy as everything needed to be custom to suit my quality standards.

I had to wait 6 months last time for my last exhaust then ended up getting a refund and went custom. In the end the custom cost me a lot less.

 

If that is the case then why do we see hp & tq gains with other cat back systems? I do remember seeing people with hp & tq gains with an exhaust system....did I mis-read?

 

do you have any sound clips of the magna flow exhaust and why did you get rid of it

 

What I would recommend (and a lot of people would agree with me) is either a single 3" or a dual 2.5". If your turbo is going to be HUGE I guess a dual 3" would be acceptable, but it would have to be pretty freakin huge. Look into the HKS Hi Power mufflers, I have two of them on my custom dual 2.5" setup, and they sound amazing, look gorgeous, and are built to last. I don't know anything about building custom headers, I've been looking everywhere for headers w/ a 2.5" or even a 3" collector, but I've found none. I would really like to hear more about custom headers, can you give me details? thanks and good luck, custom is the way to go for sure.

 

Just FYI, the biggest downpipes I've ever seen are 3.5" and this is what APS puts on their extreme turbo kit. No one, or VERY few people have this setup actually on their Z yet. In any case it offers some of the biggest turbos around. (If you're looking for "really huge" turbos)

Even then, they still only use 3.5" pipes. 4" is uber-overkill and most likely you will lose power, as some effect of turbulence or reduced exhaust velocity.

Yes, you can gain some hp with exhaust systems. It's been dyno proven. However if you're N/A then exhaust is the most expensive $/hp mod period.

 

Thanks for the reply/advice. From what I am gathering is that other mods should be put in place first. I am assuming you would recommend cold air intake, plenum spacer, what is next in this line?

Do you think header would be the next step or do you think this would be the best first step.

I plan on getting a 2004 Enthu. 6MT and keeping the 18s stock rims and lowering just a little bit. I went full race coilovers on my last car and it first the ride was great but you have to check your teeth fillings after a ride.....jarring as hell!

So I would be looking to just use springs to lower a little....no body work as that was nightmare as well for me going with full body kit on my last car with CF hood.....


Pls keep the advice coming.....

 

PM Sent

 

okay so forgot 4 inch exhaust......custom 2.5 inch rear duals?

 

If you can feel the difference between stock and after market exhausts, you have a magic butt dyno hahahah. You did not mis-read, but in real world application even with my Nismo cat back which is supposed to have some of the largest gains, the difference from stock is hardly noticable. Even after all the bolt on mods are done on the 350 the ecu still doesn't know what to do with them until it is reflashed or a piggy back is added. So the gains made by these systems is really just made in the amount of crap you can put in your signature on this site... I am ranting.

Anyway, if you do a custom exhaust, take pictures and show the rest of us.

Flowmaster. No I do not. It was about like stock but deeper and much much louder. I could hear many blocks away when I had one of my friends drive it. I had no drone at any speed. I got rid of it because the price was right for the Nismo cat back I got.

 

If anything I would just save your money and go with the turbo. Something like making custom headers is going to be a large task since it is a fairly cramped space in the Z although not impossible.

Otherwise a custom 2.5inch exhaust would be more than sufficient for an NA build up or even a 3" single exhaust would do.

 

I would prefer to work from the headers back. Get the difficult part out of the way. The cats - test pipes and cat back exhaust will be be easy. If you have the money and a lift, do the entire exhaust at once: that way you only have to get under the car once.

 

My gf (future wife) said her car has to have rims & be lowered before I get to touch my future 350z.....so all of this will be on hold.

Plus I still have to buy a 350z!!!!!

 

So, there's not going to be a 4 inch exhaust?

I have Topspeed Pro-1 Exhaust and it has 3" piping. For some reason, it feels like I've lost power, especially in the lower RPMs. When I added the silencers, my car, strangely, felt faster but still felt a slight loss of power in the lower RPMs. The higher RPMs, I'm not sure, as it doesn't feel too different.

Can anybody explain to me what exactly happens with those 3" piping and what kind of difference there should be with the silencers in?

 

For naturally aspirated applications, a 2.5" pipe that comes together into a 3" to the tip is the best. Any larger than that and you will LOSE power unless you have a turbo and need a larger tube. Size of exhaust is all about the cooling properties of the air, or the EGT. Some people will talk about backpressure, only listen when they are speaking of EGT (exhaust gas temperature)

 

jus do dual 2.5. i felt such a difference- even bigger when i took them off. Most 2.5 duals will give u 10-15 rwhp.