Hey guys, i want to build my exhaust on a budget because i want to spread the money that i have over a variety of mods like springs, sway bars, and wheels as well. And since i can weld and stuff i can build my exhaust. I know a true dual 2.5" would give the most gains, but that requires twice the piping, twice the resonators, twice the mufflers. I want to do single exhaust but still have the dual tip look from the back. So what if i did this..

1) test pipes
2) y pipe into 3"
3) 3" piping to resonator
4) and then y pipe again into 2 2.5" pipes that will go into 2 resonators welded together acting as a muffler.

basically it follows the same design as the factory except with wider diameter piping, better resonators, and no cats. would this be a good setup for NA, and possibly FI in the future if i plan on running 400whp? sorry for all the questions, i'm just trying to be efficent with my money.

 

https://my350z.com/forum/intake-exhaust/324620-custom-muffler-delete-56k-bleh.html

 

I was having a chat at tony at motordyne, and he basically clued me in that single, dual, etc is not necessarily better than the other.

What matters in exhaust is where the 2 sides of the exhaust merge. and you can't figure that out without research.

I would get an exhaust with proven gains for that reason, or stick with stock.

 

I too fabricate and weld and tried the following with my fuel control:

Exhaust manifold, Cats, 3.5" ID Single Pipe with large single canister(Ti Magnaflow): Drone at 2k through 3.5k rpms.....sounded good too. Had this one for about 6 mo. This exhaust was bought

Headers, Resonated testpipes, 3.5" ID Single Pipe with large single canister(Ti Magnaflow): RASPY between 2k and 5k. Had this 4 mo and I wanted to kill myself. This is the same bought exhaust.

Headers, Resonated testpipes, 3.5" ID Single Pipe with Two Small Canisters and baffles: RASPY between 2.5k and 4.5k. This quieted things down but not enough. Had this 1 month and I fabricated it.

Headers, Resonated testpipes, 2.75" ID True Dual, Two Small Canisters and baffles: lots of drone up to 4.5k rpms.....some may like this. Had this about 2 days and loved it. I thought I could get just a little bit better and went with the last exhaust. This Exhaust I also fabricated, and sold to my friend, since I got a really good deal on the next exhaust

Headers, Resonated testpipes, 2.75" ID True Dual with their own resonators, Two Large Canisters and baffles: no rasp or drone, even quiet silent at idle. I've had this one for about 2 and half weeks. Its actually perfect. I don't think it flows as mush as my fabricated dual but it still works. This exhaust was bought

Using the final exhaust my AFR rose to 13.5 at 5k rpms from 13.3, basically I started moving a bit more air with this one. Which means potentially it can make more power. With the Single I was actually choking my car. Here is my thought process. I figured the rasp works like somebody whistling (or turbo spooling). The whistling happens from a large volume of air going through a small opening. The trick is to open it just enough to keep velocity without allowing the whistling to occur. I forced the entire engine's exhaust to go though a single 3.5" which cause the exhaust whistling (better know as rasp). The exhaust gas ends up running into itself at the header's collector and again at the y pipe before being divided near the mufflers and squeezing out into the atmosphere. The bottle neck was shooting a lot of air inefficiently, so if you divide 3.5 in half which is 1.75, that is what you're allowing each side of the engine to exale though. So in the single pipe the air must collide at least twice on its way out. With the true dual where the 2 halves of the engine never cross, the exhaust pulses collide only once at the header's collector, then maintain its own airstream of 2.75" ID piping through the rest of the exhaust until it reachs the outside. Thinking about it seems pretty logical and the reason for the air/fuel ratio.

 

so would you say 2.75" true dual would be the best. what about 2.5" true dual?

 

na td 2.5 is plenty

 

Reputable exhaust makers do design and performance testing. Many of our members have verified performance. What you are attempting sounds like a good design, but performance is just a guess.

 

yea a good affordable exhaust was the skunk2 TD (695 shippied) . both exhaust streams are separate the whole time and though TDs tend to lose down low. They provide excellent gains up. Borla stillen etc..all are good choices.


To be honest with the 350z im not sure if a 2.5 piping yielded any more gains then a 2.36 piping . Its really the design and sound at that point.

And single exhausts to me loose the most downlow for top end gains. I seen a JIC single loose more tq down low then any TD exhaust or catback exhaust. But thats just my views.


One other exhaust that shown good gains beleive it or not was the MRC deal with turbo XS . That 499(shipped) has proven gains na.

 

Another good affordable exhaust is the TX exhaust ($499 shipped). I got mine two days ago and really really like it. With that exhaust and a power labs spacer I dyno'd at 266 whp (240 something tq) which I was real happy with. It sounds really nice to me as well and i already liked the sound of the factory exhaust so I was a bit skeptical. The only thing about this exhaust is that if you just look at the tips, you'd think its stock. Its not flashy at all, but it does perform well. I'm not a flashy guy anyway but still, maybe a little bling would of been nice .

 

Do you have HFCs?

 

Not sure who you were asking about the HFC's but if it was me then the answer is no. The only two modes i have is the catback and a spacer.

 

HFC = high flow cats (catalytic converters)

 

I personal decided on the X02. Its very cheap compared to its unnamed look-alike/original model (cough...HKS...cough) but has held up pretty well over the past year. Have heard some rumors about rust but have yet to see any except some tarnishing on the Ti tips.

Its a 2.5 TD and its fairly loud with stock cats so wouldn't recommend TPs. New off eBay was $600 shipped.

Just throwing out another option.

 

third image is what i'm running..

-custom muffler delete
-aftermarket y-pipe (ebay)
-non-res test pipes (ebay)
only thing stock is the mid pipe.
total cost.. just under 300 bucks