Idk rather to do full 3in exhaust all the way back, I heard it would reduce power. I currently have 2.5 straight back from cat and resonater and it's pretty nice. Many concerns about this mod. Let me know what I should do and I have an 04 Acura Tl

 

unless you have a built motor, ported heads, cams, blower or turbo, etc. you're more likely to hurt performance putting 3" exhaust on your car. you won't have enough backpressure/velocity.

keep it at 2.5"

 

The best setup for bolt ons is 3" to 2.5" duals.

 

Ya I thought so 2.5 is what I have thanks for the input

 

Leave it at 2.5

 

Dual 2.25 FTW

 

Just getting peoples opinions on my options; As per GuLuMoNeY's recommendation, I took the TL to a local muffler shop, seemed to be a decent fella; his recommendation was to go with a custom exhaust made at his shop vs. buying a ready made one from XLR8 or Tsudo or gReddy (the last being the one I really would have loved to have!!). I showed him this youtube video as this is what I want - He recommends using a 3" pipe (I need to confirm material on the pipe) that would split into 2.5" Y crush bent in his shop with magnaflow mufflers that will look and sound similar to the gReddy - all installed for $575!! (He said he'd let me try out the system without resonator) and if it's too loud then he'll place the res no charge; Also he showed me some options for drone that he could do at an additional cost ($70); It would be great to have your guys's opinions as to my options

 

Of course he recommends to build a custom one over buying a premade one... hes getting paid labor to build it...

 

Going larger wont hurt performance but it might not help. If you have cats it's really a non issue. Generally speaking, larger will have less drone but will be louder through the tailpipe.

 

I am a little surprised all these aftermarket exhausts for the TL arent 3" until the Y in the back, K series guys run 3" in the all-motor stuff, we got 2 extra cyl's and over a liter more displacement.

 

i know these cars arent the same but if it serves as any comparison, the maxima guys are all running 3" catbacks with lots of power gain... i myself had a 3" catback on my 02 maxima (which is comparable in performance IMO) and guys are shown to gain 30+ whp gains under curve and about 8-12whp peak

 

I'm with Shark on this one. Want are going for? Sound/power/both?

 

now remember the bends will be 2.5" since we are crushing!! just not sure if that would provide enough back pressure if any; Also I didn't realize that a catback also had to have some back pressure??

 

crush bends

 

Why do you guys want backpressure? I thought this had been settled a long time ago. Backpressure is not needed especially in a cat back exhaust. Forget velocity and scavenging once you're past the j pipe and go for least restriction after that.

 

care to elaborate besides the obvious; 3" crush bended = 2.75 at the bends maybe...still pretty large flow diameter??

 

that's what my understanding is as well!! - Jpipe - back pr; catback - is all you & what you want (sound etc.)!!

 

The only thing keeping me from making a 3" exhaust is I can't find a set of mufflers I like, might just get a set of magnaflows and weld on quad tips.

 

yea, back pressure is a myth.. you will optimize the most performance from an exhaust where the exhaust gas flow isnt choked or isnt over powered by the size of the piping tube to have muffled exhaust gas... if back pressure was so important you would want to mod and get a smaller piping to build more back pressure :lol: im positive you will gain more power using a 3" catback.. best friend old auto legend ran a custom mandrel bend solutions catback, there is a stupid fast 3.5 altima locally who ran a 3.5" catback (seriously, and gained power), a 3" catback will be fine.. im sure you will see more power under curve though if its similar to the 3.5 maxima

 

In theory, the most efficient exhaust is one that gets slightly bigger throughout the entire system, but since that is not possible running a 3" exhaust past a 2.5" J pipe is a step in the right direction imo.

 

i think it all depends on how the exhaust per each cylinder bank communicate so u have to understand that our exhaust are only 3 cylinders per exhaust side then communicate, so ideally some back pressure is good, but 2.5" for wat majority of us have (just bolt on non built motors) would be perfect, if u are running bigger throttle body, intake, cams, higher comp pistons..etc) then i would deff say 3" is the way to go....but even with the new rv6 true dual exhaust setup the way they have it is set up perfect for bolt ons......however i would even still like to see difference between 2.5" and 3" on the same motor! because u just never know how different motors work because they all have different volumetric effeciencies...(i.e. how well the motor "pumps air" i guess as they call it?)

 

You say each bank communicates and that back pressure is necessary because of this but you don't explain why. Higher compression doesn't change exhaust requirements. The only thing that could make an engine more sensitive to exhaust and backpressure is cams and usually better exhaust flow is needed with cams.

The piston on the exhaust stroke forces exhaust out of the cylinder, into the exhaust and down the exhaust. By making it easier for the piston to push exhaust to the tailpipe you're reducing pumping losses but that's not all. During valve overlap as the exhaust valves are closing and intake valves are opening both sets of valves are partially open at the same time. Lots of exhaust backpressure means you don't get the cylinder completely empty of exhaust which also means you don't get as much of the air/fuel charge. You have a partial, diluted charge and power is reduced. The advantages are twofold, pumping loss reduction and a better charge.

The other key is scavenging. Scavenging is using the other cylinders' exhaust pulses and the low pressure area behind the pulses to help draw exhaust from another cylinder. With traditional headers they can be tuned to help each other out with the right diameter and length and placement. I'm not sure how much you can gain if anything through scavenging on a TL with it's single port per head and cats hanging off the head. The J pipe would play a large role if better scavenging is even possible. If I were going for maximum power with the TL I would probably just go for lowest restriction from the heads back. You're on the small lobe for just driving around town, you're not going to lose any low end and with scavenging playing little to no role you're best off just to go large. If you're running cats, it's even simpler, go as large as you want, absolutely no need to worry about scavenging and backpressure.

You can bet the TL's cams are tailored to higher backpressure with a 1200 cell cat hanging off of each head. I've never seen the specs but I would guess the exhaust valves close fairly early. OEMs usually have little overlap because of emissions and mpg requirements, that's where vtec comes in. They don't want lots of overlap causing part of the intake charge to go out through the exhaust. It's usually the best for power but it kills mpg and emissions.

3" should be plenty for any NA TL. I know of many people that have gone 10s with a 3" single exhaust. Keep in mind a 3" pipe has nearly twice the area of a 2.25" pipe. A single 3.5" exhaust has as much area as a dual 2.5" exhaust. That's a lot of potential exhaust volume for a small NA V6. My car makes about the same power with or without the exhaust hooked up and that's dual 2.5" with 602rwhp or over 700hp at the crank. I don't see anyone losing power with a 3.5" exhaust on a TL but I don't exactly think it's necessary. Even a single 3" is a stretch.

 

compression does make a difference as far as exhaust and is just as important as cams are for exhaust requirements and how u need to tune the exhaust area for the proper sizing...ive seen plenty of people lose power because they have gone to big of an exhaust. top end is gonna be over all better but bottom end is gonna suffer. the best is to get an exhaust the gives you and over all better power curve throughout the rpm range, and if your racing obviously top end would be the ideal and for around town bottom end is better, so its a matter of preferance on were u want the most power to be, but for most of us who have tl an overall gain throughout the entire power band is best suited. so basically u dont want to go to big or to small i.e. 2.5" is best

 

Wrong. Higher compression does not add air volume, it just makes better use of the air and fuel it has.

Think of exhaust this way. When you're driving slowly around town, the stock exhaust system will flow several times more volume that you're giving it. You in essence have a very high flow exhaust. Does the TL only make high end power at part throttle? Plus you're leaving out things like cats and stock cams and all of the things that make going as big as you want with possible no downsides.

Lets not forget vtec, you're running around on the small lobes most of the time; you're not losing anything anywhere.

 

What are the stock cats 2.25"? I have to assume J-Pipes are 2.5"... until I see a dyno sheet that says otherwise I see no reason why a 3" exhaust that splits down to dual 2.5" pipes then to dual mufflers will hurt power in any way.

I really do no see any way to increase scavenging with the way our exhaust ports are, you certainly cant pair runners or run them equal length in any way, and there is no way the pulses match when they meet wherever the collector ends up being, we have a pretty nasty crutch when it comes to that... and it really affects the output of these motors in NA form imo.

 

Exactly. Fully agreed.