So I thought it may help to make this thread. Are there any benefits of a TD design over ours? We have so many Jpipes and I was wondering if there are any gains over the 1 piece design? Does TD flow better in our case? Where are the engineers?

 

Search man...'true dual' comes up big.

 

I've searched before and nothing substantial came up. There was only 1 big thread by SRT-11 but had some good stuff in it, thanks.

 

I thought about doing it when I was working at a shop. Too much of a pain in the ass

 

The exhaust note.. lol.. If I do the turbo setup it'll be a dual exhaust.. 3" x (2) 2.5" back.

Subinf, what difficulties did you discover?

 

Not too much room to work with under the motor. And I was feeling pretty lazy

 

pointless

Majofo..the turbo gives ya one single downpipe to work with, after both heads feeding the turbo...splitting from there would be pointless since it wouldb't be a true dual...so a single 3" would be good enough

if ya had a twin snail setup then u'd do a dual.. 2.5 inch each one, x-ed in the middle.

on our car, single is fine...with the turbo, still single 3" is fine

 

I'm not a big performance exhaust guy.. I just love the sound of the Infiniti G exhaust at idle to low rpm.. Do you see any issues splitting the 3" downpipe though? I may save my money.. the splitter alone is like $65.. money that will probably serve better towards a meth kit or rodney's new knock box.

 

When you say splitter do you mean something like a y-pipe?

 

yeah..

 

Any good exhaust shop can make one for about 10 dollars. I did so many of those when I was working I should have started selling them as my own design.

 

true dual should come right off of the manifold to the back of the car with an X pipe in the middle to equalize pressure.

 

i understand...g35 doesnt sound the way it does because of the dual setup, its the motor, just like a vr6, sounds the way it does because of the motor design...aside from all that...their stock exhaust is designed by nismo.

thats not to say that exhaust setup doesnt matter...it does, and u can easily mess it up, but there's some specific things based on the motor, head design and flow, stroke can change sound big time...just like the reason why bikes sound the way they do, because of their short stroke, or F1 cars.

a dual on our car isn't going to give u anything like a g35 sound...and on the turbo setup, it isn't really necessary to split after the turbo...it still wouldn't be a true dual...remember, both heads merge into the turbo manifold, and out into the downpipe, which already creates a merge of the 2 heads into 1...i would just shoot out a 3 inch all the way to the axle and split it into 2-2.5 inch tails.

aside from everything else...the turbo muffles and changes the sound..it will get deeper and cleaner...so again splitting isn't going to help as far as sound goes, or even flow.

 

Thanks for the claro Opel..damn it's late.. I shouldn't be on Azine while catching up on work. See you guys manana.. well, in a few hours.

 

I remember there was a True Dual thread a long long time ago. I do not beleive any Acura TL-ers attempted it, but I may be wrong. The only true dual J-series I've seen done was from an Accord V6 guy, not sure of his sn but i think his real name is Drew? Seen him a while ago when he ran a RSX-S.

I beleive he had a custom J-pipe, catless 3rd cat, 2.5" all the way resonator-less to 2 Tanabe Hyper Mufflers. From what I can remember, he said it was really raspy and sounded very bad. A X-pipe was then installed and the rasp died out a bit but was still there. Those who heard it said it didn't sound to good either.

Powerwise like Opel said, no big difference or gain from our current design
That's all I remember...

 

again, a true dual would mean...one seperate pipe from each head out the back. I dont understand the need of a J-pipe with such setup as you mentioned or how it can even be used, so now im assuming he still had the stock merge, but used a diff Jpipe, and then split into a dual after that. That is not a true dual. In fact, its only unnecessary noise.

Like you mentioned, with a complete dual setup, sound will be a problem, and can be addressed with a X pipe and resonators.

Dual doesnt provide more power... your highest peak power can be accomplished with the most free flowing you can have, and doesnt really depend on single or dual setup.

At one point a few years back, i almost attempted this, and was very close to getting it done, but i had the urge at the wrong time, at which i didnt have the money, but then it died out by the time i got my hands on money lol.
My reason wasn't bcs i was looking for power,
I wanted to accomplish a different completely unique sound, But instead, i found other simpler ways.

Either way, its really not necessary. As i mentioned in the previous post, if you were doing a twin-turbo setup, then a dual can be done, instead of merging the 2 turbo downpipes into one, you can just have them run out the back separately, Xed somewhere in the middle, and some nice simple straight-through mufflers, or for some people's taste in sound, resonators can be added along the cat-back.

Either way, on a turbo application, low end sound would be pretty muffled, due to the turbo acting like a muffler itself, and not too bad to keep quiet at the addition of mufflers, and once you stomp on it, then who cares how loud it gets.

 

There was also a possibility that the loss of back pressure would be at the cost of low end torque but slight increased hp at the top end. I don't know if it was ever confirmed on a dyno though.

 

loss of backpressure does affect low end torque..till about 3k then its a whole diff story.... i dont really need a dyno to tell me that.
However, on a turbo application, it isn't a problem, since the turbo itself acts as an exhaust restriction, which creates plenty of backpressure... aside from all this, with a turbo, you dont want any backpressure at all after the turbo.

 

Yeah, just wanted to point that out for NA people. If 3K is the cutover, then it's not as bad as I read. I've never tried it so I don't know from personal experience.

 

Thanks for all the clarification. I thought it may help with scavenging being 2 separate pipes from the manifold, but I may have been wrong. I'm sure the sound would change with dual as opposed to single as well. His specific exhaust probly sounded like poop cuz it was catless with no resonators! I bet if he put a nice reso in there it would've sounded sex.

 

I am in the process of building a custom true dual setup, i will post dyno numbers to find out if it is really worht it or not.

 

One more thing to think of is our motors sit transverse. Its harder to make true dual. The front manifold run is longer than the rear so how do you plan on making it equal length?
I would do something like the RL (or what i did) and make a Y then run 2 pipes back



Mine during the mock up stage

 

^^ very nice. except I will be going out each pre cat with a 2.5 in pipe, never mergeing them, crossing with an x pipe somewhere (i belive location of this will give maximum torque). Im going to start at the rear with it, dyno it, and if im not happy with the numbers move it closer to the front.

 

I've seen first hand the huge gain in power on the 3.7L MDX who did a dual set up off the cats. Placement of the crossover is key. Before looking at this dyno, remember this is on an AWD vehicle on a dyno that reads very low. The whole point is the before/after.

Blue: Stock
Red: K&N Drop in, Stock Primary Cats, dual 2.25" exhaust with x-pipe, magnaflow resonators & mufflers

 

very nice. I can see gaining very much hp, by doing this. I will be experimenting a bit to see where the best gains are going to be.

 

Agreed. And you're going to save a little weight with a single 3" vs a dual 2.5".

FWIW, a single 3" will support around 700hp. A dual 2.5" will support a little more. And by support I mean provide very, very little backpressure in a turbo application. You could stretch it further if need be.

 

That would be the only true dual exhaust I've seen. No J-pipe and no 3rd car or a 3rd cat for each side. The X pipe should also make it sound better.

Be prepared for a totally different sound than any other TL. True duals will really change the sound.

If you're still running the stock pre-cats, placement of the X pipe is not as critical.

 

Also, if you're running the stock pre-cats, you can be a little more careless with the size of the piping. They should provide all the backpressure you need. Keep in mind you don't actually lose torque, it just shifts it up a few hundred rpm. From most of the dynos I've seen around here it looks like low end actually improves slightly with a higher flowing exhaust.

 

^ uhh.... J37 MDX pushing only 159 hp.. is this awhp? still seems a bit low.

 

Where does the drone actually come from in an exhaust system?

If I were to go a single or maybe a pair of can's down the middle of the car with just pipes out the back. Will that drone and sound like shit, just drone, just sound like shit, sound ok?

This is a question for a TL with all 3 cats or no cat's and a turbo.

 

The turbo itself will quiet the exhaust somewhat.

Drone comes from the interaction of the exhaust and body, not just exhaust alone.

I just posted it in another thread but take a look at what Ford did with the 5.0 Mustang. The factory dual exhaust used different sized mufflers on each side in order to cancel each other out and reduce/eliminate drone.

Generally speaking the further upstream the muffler is, the less drone you will have. Mild steel mufflers usually have more drone than stainless mufflers. Larger tubing usually has less drone than smaller tubing. However, all of this can be false depending on the specific car.

 

Im not looking for a different sound, but most optimal power gians. Different sound would be cool, if it sounded nice. I will be running right off the off the precat deletes, xpipe about mid stream 1 resonator on each side right after the x pipe, then 1 muffler on each side before the exit. I will put up a drawing later about the design before we mock it up and weld it.

on a side note, man i wish i could get a lightweight flywheel and a clutch with a 3000lb pressure plate.

 

anyone else questioning dual exhaust runners adding 30 whp on that MDX? I know the dyno's are funny with awd cars but, adding 30 to a low number like 160 is pretty freakin good.

Graph says before whp = 160 and I'm guessing the 3.7L actually puts about 250 to the wheels (250/160 ~ 1.5625). If you use that multiple for the before after gain, that comes to roughly 47 whp gain. Either my math sucks or this is impossible.

I mean, I've seen a full exhaust add numbers like that to a 400 +hp american V8...ahh, I'm tired and probably stopped making sense a while back.

 

The MDX may just have a very bad factory exhaust. I remember some of the old muscle cars picking up 50hp from just an exhaust but when you have 454 cubes going through a 1.75" pipe you're going to get good gains.

 

You even bother to read? Its AWD and the dyno reads very low. Don't obsess over the 160... focus more on the before and after difference.

 

Just to elaborate on what I hate cars pointed out... the MDX being a family orientated SUV... I would bet money the monster factory resonators and mufflers are probably very restrictive. Also keep in mind, this replaced EVERYTHING... the restrictive j-pipe, the 3rd cat, 2 factory resonators, and 2 factory mufflers, and all the crush bends to free flowing mandrel bent system.

The point being, I believe good even gains across horsepower and torque throughout all RPMs can be had with a properly designed system. But you would be adding weight. And I'm not saying you will gain 30-40whp. This is just showing that it can be done without losing low end power or anything like that.

Also the fact that this particular motor is orientated transversely has little bearing on the need for equal length exhaust piping. Because remember, technically on the newer J series, the exhaust extractors are built into the head which is where a good majority of the back pressure is built up already. The 2 most important things in doing a dual piping system from heads back is piping size and placement of x-pipe for balance of gases so you don't have one pipe trying to 'suck in' air from the back of your car.

 

It's definitely got some back end restriction. On my 1G MDX there's a huge mid muffler. On the 2G MDX it looks like there's a y split from the 3rd cat to two large mufflers / res as well.

 

Missed the comment.. so how much hp can we safely say is from the catback. Is this your X cleanCL?

 

Not my MDX... but I was there for the dyno and talked to the owner heavily about what was done.

As for the numbers, you guys need to take a second look at the dyno, the stock run they only brought it up to 5800 rpm and the after run was brought up to 6100, so the comparison of the 2 peak numbers can be a bit misleading. Just look at the overall gains throughout the RPM.