Sonnick

IHC: I've heard taht the piping near the head should be smaller to keep exhaust velocity up. If it's too large, there will be less velocity, causing a loss of torque. Exhaust science is all based off keeping the velocity as high as possible for a given pipe diameter. You will have more velocity in a 2.25in setup I'm assuming, but it won't be moving near the volume of air of a 3in setup. You have to try to meet somewhere in the middle with both velocity and pipe diameters to net the best gains.

With that said, everything after the collector is just a restriction.

I hate cars

That's true. But the cams play a very important role in exhaust selection and with their small nature when not in vtec, you really can't hurt the low end. With all the dynos out there, there's not one that shows a loss in low end or torque, only gains. One thing to point out is the same size pipe at the heads will be more of a restriction than it will be near the rear of the car as the exhaust cools.

When you throw large cams in the mix, you have to pay more attention to exhaust sizing. That's why member ethenol with his large aftermarket cams preferred the stock j-pipe over an aftermarket one if my memory is correct.

Scavenging is a little different since we don't use a traditional header. It's still there but not as prevalent. I do like your theory, tune it from the PCD to the J-pipe and then go as big as you want.

With everything I said about the cams vs exhaust, one thing to keep in mind is most people using larger cams still use the stock rev limit. If the rev limit were raised as it should be with larger cams and say we're spinning 8,500rpm, it would be the same story, use the largest exhaust you can from the heads back and don't worry about the low end, you're just shifting the power band upwards and not losing anything. I wish these cars were figured out like traditional American V8s. You knew exactly which header, exhaust, and cam to run based on the intended rpm range. There's just no R&D of different exhausts based on different engine combos.

DisgustipatedAP1

Hi, just a little update for anyone who has been interested in this.

I didn't get a chance last week to get the exhaust made because I went on vacation, and I haven't been able to put on any bolt-ons because the exhaust flange bolts are so rusted on that I'll need the exhaust shop to torch off the j-pipe and catback bolts.

Other than that, I'm ready to have the exhaust made, hopefully tomorrow! Here's what I've got so far to put on the car:

E-Shift High Flow Cats ($150 for all 3)
ATLP J-Pipe v1 + race pipe ($220)
3" custom exhaust from J-Pipe-back ($400)
Stainless steel 3.5" quad-tips for base bumper fitment ($67)

I plan to just sell the E-shift 3rd cat and race pipe to make some money back ($50 each should get them sold quickly), because I think having the exhaust go from J-pipe back only makes sense and will allow me to use a 2.5"-3" merger (thanks Sonnick for the suggestion).

I wanted to do all of this on a budget and found some really good deals on parts. Yeah, they're not the fancy new RV6 or ATLP stuff, but they should work pretty well, especially for the cost.

Will update once I get all of this on, hopefully in the next 2 days.

Sonnick

Sounds good dude. The difference is gonna be night and day from these mods. You are basically going from a stock ~225whp car to a ~260whp car all at once. That's gonna be exciting!

I'm glad you decided to try the merge collector Did you get it from SPDexhaust as well? What reso/mufflers did you end up going with? Let us know.

DisgustipatedAP1

Well, not exactly. After reading this thread: https://acurazine.com/forums/showpos...6&postcount=16

I think I'm going to follow that approach. Custom J-pipe going to a true dual with an H pipe.

However, I'm thinking I should do a 3" J-Pipe going to a 3" true dual with a nice resonator (18" or 22") and see how that works. Most people seem to do 2.5" J-pipes as well, but I'm thinking a 3" J-Pipe going to 3" true dual would work even better?

The setup in that link is basically what I had in mind but one step further. The guy I'm going to can do it just as well as that one.

Funny thing is, the guy that did that fab work (Labree) is located about 10 mins from my gf's house. I'd go to him, but it's about 80 miles from my house. The guy I'm going to does great work as well, and I'm sure if he uses the pictures as a reference he can get it spot on.

Anyone think that the 3" custom J-pipe + 3" true dual would be the optimal setup?

TLdream

iTrader: (4)

I think the 3" true dual is going to be a bit of overkill. I am working on a 2.5 td setup right now. Here is what i have, should be installing it next weekend.

Im currently running stock j pipe to single 3 in.

Sonnick

3in true dual is way overkill. The biggest I'd recommend is 2.5OD, not ID (meaning outer diameter so the inner would probably be around 2.35-2.4).

http://www.boyleworks.com/ta400/psp/exhaust3.html

On this particular setup, an X pipe outperformend an H. I believe the X pipe does a better job at sound deadening as well. If you really want to go the true dual route, read up on the differences between them so you can get an optimal setup! Good luck.

swoosh

iTrader: (5)

awesome....you did find my exhaust thread....

honestly i think your trying toooo hard....3" is an overkill anyway but why do you want a Jpipe when your doing a true dual ??? you will be loosing some power there....you want the exhaust to have minimal amount of merges/splits (restrictions)....as they said I would go with a 2.25ID or 2.5OD topsss.....

see 3" is perfect for single and when your doing duals I would go with a tops of 2.5....am glad others are venturing into true duals so we can compare the results of 2.25 v/s 2.5 etc....

true....

X is better than H is better than J....mentioned J as the OP is wanting to go Jpipe as opposed to X or H....

Sonnick

Good point Swoosh. I didn't even catch that. OP: You can't do a Jpipe if you are going true duals. True duals you have 3 options: X/H/no pipe. No crossover pipe would sound 'disgustipated' so I would venture far away from that. Sounds like an interesting project though. In for results.

swoosh

iTrader: (5)

^^^ you could do a J pipe....but it would be like richie's...not really a true dual....

Sonnick

Exactly my point

swoosh

iTrader: (5)

i guess i will have to wait another week for my exhaust....Aug 8th it is....

swoosh

iTrader: (5)

bringing this thread back from the dead....

DisgustedAP1 and TLDream....any progress on your custom exhaust ?

bouncer07

When making these kinds of threads, it makes us readers thinking that it went wrong when they are not coming back to finish up where they started. Was people right on going 3inch? Was people wrong? It's complicated when the testers backed off and disappeared. All in all, I think that with 3inch true dual on N/A will lose power but with a single outlet exhaust it may gain some. Just look at the Nissan Skyline GTR, 600whp, true dual 3 inch, total monster. Same with 350Z---> turbo = Dual, All motor = single or 2.25 - 2.5 dual

swoosh

iTrader: (5)

^^^ i agree with you hence bumped the thread....my 2.25" true dual is running perfectly fine....yes its a tad bit loud and has some rasp @3K-3.5K rpm but other than that sounds great....

i wudnt recommend going more than 2.5" on the TL....thats what I told the OP....