LI_Max_WOT

iTrader: (9)

Ok.. sort of a tricky question here which will probably be disputed. The goal of this mod is to keep torque 3000< rpm the same or improved, increase mid-range power at 3k - 4.5k, and especially to open up the top end over 4.5k. I'm currently on the stock exhaust, and intake mods include a SRI and NWP spacers with a port-matched uim/elbow. I've never been dyno'ed or tuned, but each piece of the puzzle has been added separately to allow the computer to self-calibrate itself. The current status of the car, IMO, is that it hits peak torque at 4k rpm and then just rides an upward hp curve with a plateau at around 6k rpm. To achieve a meaner hp spike over 5.5k is the goal here, without sacrificing low or mid-range power and keeping the sound levels low.

Option 1: Dual Pipe Catback

This entails a short 2.5" pipe after the cat to a single inlet 2.5" Magnaflow with dual outlet 2.25" with dual pipes to a dual 2.25" inlet/outlet Flowmaster 50 series. The only problem I see occurring is getting two 2.25" pipes bent over the rear beam (there's not too much room there). To solve this, I'm thinking that two mandrel bent 2.25" pipes could fit through this gap if they were close enough and maybe were welded together in place with some sort of plate. The exhaust would be in two sections, meeting in front of the rear axle with dual flanges. My estimate is that this will cost about $500 to be fabricated which is not too shabby for the complexity of the project.

Option 2: Stock Y-Pipe Modification

My idea for modifying the stock y-pipe is to basically lengthen the two runners about 8-14" depending on how much room is down there (I will take measurements soon). The two pipes would be joined with a y collector, with either two flex pipes before the collector or one after. I've searched everywhere and could not find the diameter of the y-pipe runners, does anybody know the size? I'm guessing that they are 2" a piece, and the y collector I'm looking at is a dual 2" inlet and single 2.5" outlet. The goal of this would be to slightly mimic the effect of longer tube headers. Total cost would be about $100-150.


I'm not too good at theories of pipe diameters, velocity, back-pressure etc. and I was basically using this as an opportunity to share some different ideas with the .org (I don't know if anyone has done either of these things). I'm wondering how both of these options would affect the ENTIRE power band. I'm not in the habit of what I call "trading power" (losing low end torque for high end hp), the goal here is a gain in the entire power band. Any feedback would be appreciated.

T_Behr904

Why not just get a 3" catback from Cattman or BRM?

aackshun

iTrader: (3)

Your question as I understand it:

You want more power everywhere?

But I do not understand why you want a dual exhaust? For cool points? I can't fault you there, besides cool points I don't see why go dual.....

Get a 3" Exhaust all the way, don't be a... wimp (not the word I was using in my mind)... And get a 2.5" and say "Oh I don't want to loose my low end blah blah blah"

Remember, your motor's exhaust ports outflow some of the world's top performing motors, don't choke it, k? thx.

I wish I wasn't in a rush when I did my headers and got the pipe made to 3" instead of it being 2.5 (stock for the OBX's)

Rods03Max619

iTrader: (5)

Yeah Go Full Cattman and more power all over the board...or get headers and keep the stock exhaust...it will definitely pull harder, will be putting my 3in. back on some time this week coming up...got Vids of Headers on youtube hit link in sig, Stock Vids also and its a Auto so if your 6mt should be even better.

GreekMaxima

dual exhaust??? dont do it... not cool, no more power. Just get a cattman 3'' full catback or even 2.5'' pipe.

schmellyfart

iTrader: (46)

LI_Max_WOT

iTrader: (9)

I figured to get responses like that. Will a 3" catback inch out a 2.5" catback or stock, yes... and I mean inch out. This to me means nothing. This is my daily driver and I don't redline every gear all the time. Dyno-proven means diddly when its only measured over 3k rpm. I'm under 2.5k about 90% of the time.

This is what will be done: either a dual pipe catback or an extended y-pipe which would possibly eventually receive gutted precats once mine go out, I'm at about 90k miles right now. So instead of just jumping into this thread and touting a 3" cattman, how about we get some opinions on each setup???

LI_Max_WOT

iTrader: (9)

If someone could inform me of the pipe diameter of the runners in the y-pipe that would be grrrreat! Also, if anyone could explain to me the differences in these two y-pipes that would be fantastic.



I'm thinking that the stock y-pipe on the top would be better at creating backpressure and achieving maximum low end torque and a balanced mid-high range power curve while the aftermarket y-pipe would lose low end power (because of its straight pipe design and mandrel bends), keep mid range power about constant, and cause a spike in higher rpm hp by increasing the velocity of air through this section of the exhaust. Anyone have any thoughts on this?

skweaky

iTrader: (3)

You get mad at people saying "just get a 3inch" but you use the word "backpressure"?

Anyway, I see no problem extending the y. Might make 2 or 5 more HP. Can't hurt. As for dual 2.25 catbacks, no. Just no. You're adding more pipe area for friction to take place. Genesis coupe guys are picking 3inch single over 2.5dual and making more power and a better sound.

If u drive conservatively 90% of the time, just gut your cats and get an electric cutout. Best of both worlds.

sparks03max

iTrader: (7)

lol backpressure

aackshun

iTrader: (3)

I quit

J2FRESH

iTrader: (8)

Rods03Max619

iTrader: (5)

Yeah like someone said just gut the cats and do a Warspeed y pipe or Cattman and keep your stock exhaust will gain some torque and HP...and that y pipe shown above is from what a 6th gen or what car....I got Headers and stock exhaust don't redline everytime either but if a girl can notice the difference im sure you can to....GL...

LI_Max_WOT

iTrader: (9)

Good point about the friction being caused by the two separate pipes. I still think a two pipe system would still flow better than a single 3" pipe. Two combined 2.25" OD 16g pipes would have a greater cross-sectional area than a 3".

Here are the numbers for 16g tubing:
OD (in.)....ID (in.)...Area....
2.25........2.120.......3.53.....
2.50........2.370.......4.41.....
2.75........2.620.......5.39.....
3.00........2.870.......6.47.....

Wow. That's some good stuff right there. Backpressure determines flow rate, sound levels, and determines where peak tq and hp are in the rpm range. (Those are not all important things?) So, while you say "lol backpressure" I first say "what a d***" then I says to myself, "self, how can I use this to my advantage from a stock exhaust platform."

My guess is you'd be doing the world a favor

Who invited you anyway?

The y-pipes are stock and aftermarket for a 6th gen.


Thanks to everyone who contributed

LI_Max_WOT

iTrader: (9)

M3's use a true dual, why shouldn't I?

HMAX08

OP good luck on your plans. Also, if you are gonna post in the 5th Gen section, your gonna need some thick skin. These guys are no JOKE, LMAOO Again good luck in your pursuit

T_Behr904

That's a great question. You should ask the engineers at BMW why they chose that exhaust setup for that car. The way I see it, if you want to try to route 2 pipes where one pipe goes, and you can route it around the fuel tank and you can get it up and over the beam axle, and you're willing to pay an exhaust shop to figure it out, then go for it. It's your car, and your decision. Make sure you post before and after dyno run flies for us so we know how it works out for you.

aackshun

iTrader: (3)

You ask vague questions.

We ask questions to clarify.

Even though we don't quite understand why you want a true dual we still tried to answer your question.

Then complain about the answers like you already know your answer? Then why ask the question to begin with?



This is 6th/7th gen section non sense

Rods03Max619

iTrader: (5)

If he does that we are talking some on big money spent way more than a full Cattman for sure.....GL....on that plan....

T_Behr904

It's his car and his money. If he wants to reinvent the wheel, then let him do it. I'm not going to talk him out of it or persuade him any further to do otherwise.

Chris Gregg

iTrader: (59)

You've got great feedback. If you want to learn (and you obviously need to) then ask questions. But don't try to force your ideas or concepts down our throat without the ability to justify your perspective intellectually and clearly. You keep arguing you think your ideas are great somehow, better than what's already been proven. Okay, either back it up with intelligence or back it up with spending thousands in R&D. I look forward to the before/after dynos!

phatboislim

iTrader: (27)

cutout /thread

Scottwax

iTrader: (8)

Here is the solution for V6 Accords, wonder if the same could be done for a 5.5 gen?

http://rv6-performance.com/index.php...art&Itemid=104

Instead of how our aftermarket y-pipes go into a single pipe into the main cat, it stays two pipes, completely eliminating the main cat (which on a 5.5 gen isn't monitored anyway) and then goes to a single pipe at the cat back exhaust.

LI_Max_WOT

iTrader: (9)

This is some good stuff Scottwax! Here is what he is referring to:

"By completely removing the 3rd cat runner length was increased in order to take advantage of exhaust gas scavenging.

Dyno tests were performed on an unmodified 05 automatic base TL with 55k miles using a AWD Mustang dyno. We choose this vehicle because it is most common among the community. Higher gains are to be expected with the manual base and TL-s.

13 WHP peak gained
7 WTQ peak gained

15 WHP average gained
12 WTQ average gained"

These are some impressive power gains from a y-pipe extension to a main cat delete!!!

skweaky

iTrader: (3)

The word "backpressure" is missused and makes anyone who uses it seem ignorant. Backpressure is always bad. end of story.

The Acura thread pretty much confirms what i said about maybe gaining hp with extended y pipe.

Full dual exhaust with mufflers is 75-90% heavier than a single 3inch.
Its also more expensive to build.
And harder to remove/service.

extend an aftermarket y pipe and build a 3 inch catback from there.

or put a cutout where your main cat is and mount the switch somewhere easy to flip

LI_Max_WOT

iTrader: (9)

I am stubborn but not incorrigible. It appears that two 2.25" pipes will be extremely annoying to try to bend around everything after the place of the stock resonator. After further inspection, I can see why mostly everyone on the org goes for the single pipe exhaust, there's very little room to work over the axle. Here is what I have come up with as a "best of both worlds" type deal:



Given the information in the previous post, how do people feel about this setup?

LI_Max_WOT

iTrader: (9)

Sorry, I was getting the effects of backpressure mixed up with exhaust scavenging. I am an amateur tuner and do by no means claim to be an expert. When I started this thread I just didn't understand why so many people were just saying to go with a 3" catback without really giving me any reasoning really. For all the reasons you just stated is why I will eventually go with a 3" exhaust, but for now I think that I will have to split this project in half, and will work on the extended dual pipes system after the headers and see where that gets me.

It seems like we have arrived at a good looking compromise. The cost of the y-pipe extension will be about $400 total, and the 3" catback will run me about $400 too, with a Flowmaster 50-series and mandrel bend pipes. Not to shabby for a well resonated, smooth transitioned, mandrel bend pipe project!

Does anyone have opinions on which system would be more beneficial to put on first? I'm pretty much set on the y-pipe project, just to see the effects on it with a perverbial "cap" on the end of it with the stock system still in place and also keep sound levels moderate. Will the stock muffler be able to handle the increase in exhaust velocity?

BobPezz

iTrader: (5)

I suggest eliminating the X pipe, it will negate the extra length concept since at that point both banks will interconnect. The dual inlet/outlet resonator will also have a similar effect. A dual inlet single outlet resonator could also act as the Y pipe. Locating it right before the S pipe would yield the longest dual runner length possible.

LI_Max_WOT

iTrader: (9)

Some good points you have there BobPezz. It's kind of hard to visualize with my grade school artwork, but maybe I can clear a few things up.

In my plan: the y-pipe runners would be separately extended to the position of the stock main cat, which would be replaced with the x-pipe. The x-pipe has dual 2.25" inlet/outlets and a 2.5" core. This is about a lengthening of 2.5-3' for the runners, after which the pipes would crossover to balance the exhaust flow between the headers. The purpose of the x-pipe is two fold: to quiet the exhaust down, even out exhaust flow. Being possibly the only Maxima with an x-pipe is just a plus!! I feel that placing the crossover point way back where the resonator is going to be is just too far away from the engine to do its job properly.

I like your idea about the dual inlet/single outlet resonator, I really like it!! Putting the resonator right before that S-bend would really maximize the length of the dual piping, while saving me the extra cost of buying a y-collector!!

LI_Max_WOT

iTrader: (9)

Parts list thus far in order of appearance:

Flex Pipes x2: 2.25" I.D., 8" length
"Jones Exhaust" flex tube, piece of junk??

X-Pipe: 2.25" dual inlet/outlet, 2.5" crossover

"Resonator" (second muffler basically): 2.25" dual inlet/single 2.5" outlet


Total parts cost without a few flanges and some mandrel bent stainless steel pipe for the extended y-pipe: $230!! Summit racing free shipping for the win!! Before I order these parts I should probably confer with my exhaust shop guy to make sure he's willing to piece all this together for me...

Cant_Get_Ryte

iTrader: (52)

GET THA FLOCK OWTA HEEEEEERE !!!!!!!!!!!!!!!!

skweaky

iTrader: (3)

Jones is great stuff.

LI_Max_WOT

iTrader: (9)

funny stuff! NO JOKING! haha he was laughing his *** off off

Wicked cool. Jones is $20 compared to megan racing $50

"These Jones Exhaust Systems flex tubes are designed to minimize cracked manifolds or headers. They feature a T304 stainless steel 2-ply bellow flexible joint with corrugated inner tubing that is encased in a T304 braided cover. The flex joint pipes are available in different inlet diameters for any exhaust combination that you need."

doublea

iTrader: (7)

There is 2-3 way to make a dual exhaust, one can be dual 2" pipe coming from the Y-Pipe or from each headers to dual muffler (a la M3) or to run a single 3" pipe from the Y-pipe and then divide to 2 x 2" with dual muffler. But in order to do that, you have to either cut the spare wheel well partly or entirely or make a pipe that is bend around the spare wheel well. My 2k1 max is extremely modified, I have cut the spare wheel well entirely, cover the whole with metal sheet and brace the rear end with 1" square tubing welded to the chassis, I have cape the brace with diamond plate aluminum sheet so it doesn't look like crap, this also act as a heat barrier between the 2 Cattman muffler and the trunk. The only thing that left to be done is to weld the muffler hanger on the left side and weld the piping together, I'm probably going to add a flex section in the rear so the piping is not to stiff, that should prevent the welds to crack open. My engine has been totally rebuild with lower c/r and forge piston and so much done it would take a full page to describe, but it's blue print and the rotating assembly fully balance, so you get the picture. I could have done it with a single 3" but a dual Cattman exhaust is really sharp and unique, Cattman have fabricated me a left muffler specifically for my car. It's going to be awesome, either the look and the sound. As for the weight it is not really a factor, the added weight is not that much, maybe 15-20 lb. I like to have a something different that not many people have achieve, it might just be an excuse to work on the car but at the end it's all fun.

Rods03Max619

iTrader: (5)

So when do you think you are starting this project?

CMax03

iTrader: (3)

I've considered this same thing B4 as well and you won't be fitting the oval shaped muffler anywhere other you Maxima cause it won't fit inside the existing exhaust tunnel! Unless you shop around and can find a smaller round muffler with dual inlet/dual outlet or this single inlet/dual outlet style I've provided:
Anyway it'll be tight but using this round type it can be done! Good luck!

doublea

iTrader: (7)

The car is 90% done, I need to send my blown ECU to some place in Fl. My friend is a tech at a Nissan dealer and was suppose to come by with the Consult II computer but the computer is screwed, his boss doesn't want to repair it. Now they have the consult III but my friend has a hard time with his boss, no letting him take the consult III out for an evening to reprogram the replacement ECU I have bought locally. His boss want me to bring the car up-there and leave it there for few days, but this is out of the equation. I can't trust people I don't know, there is simply too much money invested in that car, risk if seeing part get stolen or anything else. My other option is to send the blown ECU for a rebuild, they won't have to be reprogram for the key. It's been a month that I said I will ship the ECU, but I've been pretty busy with the return to school and now with me starting a new business. I'm sending the ECU today and hopefully, I could start the engine again in about 7-10 days. In the meantime, I have to fix 2 small leak, one from the oil pan, I need to redo the sealant gasket, and the other one is the coolant pipe on the side of the engine but I will take care of both hopefully next week. After the holiday the car is going to the paint shop and will be back in february, then I'll weld the exhaust ( need to buy the tig welder first) so as you see i'm over load of stuff to do. I want the car to be ready for spring 2012, no more delays, that is going to be 5 years that the car has been sitting in the garage so time to move on.

skweaky

iTrader: (3)

Dublea... zero f*cks given at all about staying on topic.

ChrisMan287

iTrader: (34)

Good luck.

LI_Max_WOT

iTrader: (9)

@ dublea: I've thought about cutting out the spare wheel well and mounting a cross-flow muffler, but besides having a pretty cool and unique setup the cost-to-benefit ratio just isn't there for all that work. If I had all the equipment to do that and this wasn't my daily driver that might be a different story. Besides cutting into the spare wheel well, it would be very difficult to squeeze more than one pipe in the axle area I think.

First half should be done by the end of the year. The secondary will be determined after I see the effects of the first install. A before and after dyno is highly unlikely. But there will be many road tests, controlled experiments, and video footage to compare the setups.

Hmm... you have an interesting point. The magnaflow I was looking at is pretty small (5x8x18) which is only an inch wider than the round muffler you suggested. This will need further investigation and I will be able to take measurements tomorrow. I saw that 7" round when I was doing my research but those inlet pipes just looked too close together, but it could definitely work. Is it possible that a more straight through round muffler, like the one you proposed, would produce a faster exhaust flow because it's a more direct flow?

@ skweaky


Thanks. I'm definitely going to have my fingers crossed on this one... that's part of the reason I'm only doing half at a time, but most of the reason is I plucked all of the c-notes off of my $$$$ tree.

Update: I'm thinking to go with a single mandrel bent 2.5" after the dual pipes. IMO, I think that'll be large enough and will maximize mid-range power while providing enough flow to really open up the top end, especially with the dual piping before it.