[N0OS3]

So, i'm closing in on the day i put in my headers (MMW) and decided i'm going to re-route my exhaust all together and come out as 3.5" quads in the back...

The exit tube of the headers is 2.5" diameter. I'm going to weld my OEM flanges to them. From there, route 2.5" piping into Flowmaster mufflers (mid way through the piping). The exhaust will still be individual to each header (no connecting; i.e. x-pipe, h-pipe, y-hipe, etc.). From the mufflers, will exit 3" piping and split ways at the rear differential, each going to the rear of the bumper on opposite sides. The pipes will be coming up at an angle to show off the actual black chrome display that will be the tips. The pipe will split before connecting to these tips as y-pipes and will piece the dual 3.5" tips to each end (making FAT quads). The tips are also angle-cut, therefore i will turn the outward most part of the tips inwards toward the center of the car about 30 degrees, giving the appearance of the exhaust facing outwards from the vehicle.

I submitted a ticket to Flowmaster to get their advice on a good mid-muffler; waiting to hear back from them. This design (minus the quad tips) using a mid-muffler is very popular among inline 6's used in 68 mustangs and that era of muscle cars and they sound great... i'm not 100% devoted to this design yet until i hear back some professsional advice about the sound i'm trying to acquire....

What do you guys think?
[sorry, no pics at the moment and nothing to reference to either because no one has this rear end quad exhaust that i see]

[N0OS3]

So i talked to a different muffler shop, and the guy there has 35 years experience and told me that pretty much no matter what you do to a BMW's inline6 is not going to make it sound deep and throaty like a muscle car... O_o i mean, right now <5000rpm i sound like a beast, but after that it's raspy and ricey (for those of you who seen my DIY video, a take off is demonstrated at the end) and he says there's nothing you can do about that... i'm thinking in his 35 years, he hasn't tried enough muffler/glass pack/resonator variations to know that for certain... his shop mostly does repairs on old catalytic converters, installing aftermarket (pre-fabricated) exhaust on consumer's cars that don't know how to do it themselves... i think if someone had access to a bmw and tried out different combinations you could come up with something really good... O_o that's what Active Autowerks does, right? and Supersprint?
I dunno though... i'm still going forward with this, but i mainly don't want to be THE annoying guy in my community with a loud ass exhaust screaming at 6:45am when i go to work... it's not necessary and i would be a hypocrite if i didn't fix my own issues with being loud... so, i think with catless headers and everything else except a mid-muffler would be just the ticket...

[Ricke90]

Just want to make sure I have this right.

To get a deeper sound you want to forgo any crossover in your exhaust set up?

[N0OS3]

Originally Posted by Ricke90

Just want to make sure I have this right.

To get a deeper sound you want to forgo any crossover in your exhaust set up?

so far it's worked out for me...

right now i have straight pipe from headers back with no crossover (true dual exhaust)... pipe goes from 2-1/4" from the headers into 2-1/2" into 3" tips. If you search on youtube for "E90 Straight pipe" i'm sure you will see my car there...

[Ricke90]

Okay, interesting. I know that on a v8, having an H pipe crossover gives deeper tone. Also, it helps with scavenging to have some sort of crossover. Better scavenging means more power, basically.

It would be interesting to see what adding a crossover pipe might do for you.

[N0OS3]

I've been reading up on exhaust configurations quite a bit... basically, i want to keep the "popping" from my exhaust (to me, it makes it sound more throatier), adding an X-pipe or H-pipe takes that away. My exhaust guy thinks that if i had a muffler, the loop will help with backflow and scavenging and help reduce the loudness slightly (depending on the size of the muffler).
On a side note, since separating my exhaust into two separate pipes, i've lost ~3mpg both hwy and in town... so, it's not for the weak pocketed.

[N0OS3]

It was explained to me, one of the major differences in Inline 6 vs V configuration six is the firing timing... this is how it's explained in a V8:

With a V8, a cylinder fires every 90 degrees of crankshaft rotation, so that part is even firing. But the crankshaft only has 4 throws, not 8 throws, so you don’t have complete freedom to choose firing order. What you find if you scratch your head and think about it for a while is that on each bank, the firing sequence will be two intervals of 180 degrees of crank rotation between firing, one of 90 degrees, and one of 270 degrees. So the cylinder firing on each bank is not evenly spaced. The crossover pipe allows the exhaust system to partially compensate for that. When you get to the point that the 90 degree interval is firing on one bank, that’s also about the point where the 270 degree interval is occurring on the other bank, so the crossover pipe lets a bit of exhaust from the side that is firing on 90 degree interval at that instant cross over to the side that is on 270 degree interval at that instant.
Layman's terms:
Considering the whole engine, the 8 cylinders fire evenly, meaning bang, bang, bang, 8 times, evenly spaced, in a row. But if you just consider the 4 cylinders on the left bank of the V, or the 4 cylinders on the right bank, neither bank fires evenly. Each bank of 4 goes bang, pause, bang, bang, pause, bang, extra long pause, and repeat. Furthermore, it works out such that the short interval “bang, bang” on one side corresponds in time to the extra long pause on the other, so the crossover pipe lets some of the momentarily higher flow of exhaust from the short interval “bang, bang” cross over to the other side where there is momentarily lower flow because of that bank’s long pause. The earlier post tried to explain a bit more about why that is, namely degrees of crankshaft rotation between firing pulses related to a 4 throw, V8 crankshaft, but it sounds like it failed to do that clearly enough.

So, a V6 would be firing at approximately 120 degrees on each side... an inline six fires at 60 degrees because they're in a straight row (so i'm told)... that being said, it's a lot easier to work with the exhaust for compensating scavenging loss... [he says you work with backpressure more than you do anything else]

Anyone can correct me (or my exhaust guy that explained this to me) if i'm wrong...

[N0OS3]

here's some more insight:

Exhaust X-Pipes

This simple mod nets more power and great sound

Leonard Emanuelson / autoMedia.com






It's a proven fact that joining the exhaust pipes of multi-cylinder engines improves power and torque over a broad rpm range. A "tuned" set of exhaust headers (with pipes of calculated diameter and length) actually assists sequential firing cylinders to scavenge spent exhaust gases, making room in the cylinder for an undiluted, fresh charge of fuel and air. The velocity of exhaust gases in one header tube causes a low-pressure area in an adjacent tube, literally sucking the exhaust out of that cylinder. The more cylinders, the greater the effect. The late and great Smokey Yunick built several eight-into-one header collector systems that showed increased power on the dyno. Unfortunately, such a system is virtually impossible to package on a typical sedan type of vehicle.

Early H-Pipes
That which works with headers also works downstream with dual-exhaust systems. Unconnected dual exhausts on V-8-powered vehicles act as two independent four-cylinder engines and exhaust systems—and we all know what four-cylinder engines sound like. Back in the '60s, performance engineers at the Big Three car companies discovered that running a balance tube between the two branches of the exhaust system (subsequently called an H-pipe) would broaden the torque curve as well as cut down the interior noise caused by resonance in the exhaust system.




Fast-forward 30 years to the '90s, where a revolutionary development in exhaust technology has taken the balance-tube H-pipe to the next level. Instead of connecting the branches of a dual-exhaust system with a restrictive 90-degree connection, the X-pipe union simply flows the two branches together without changing the direction of exhaust flow, and one side can easily draw from the other for a sizeable reduction in back pressure.


Many companies are now producing X-pipes for most popular performance cars. They are typically available in off-road versions (without catalytic converters) or as 50-state legal models with proper emissions equipment. Most are designed as simple bolt-ons that require less than an hour to install with basic hand tools.


For those who have vehicles where no X-pipe is available, a custom X-pipe can be made by any competent muffler shop by purchasing the X-pipe union and bending up some exhaust tubing to make it fit. If you are fabricating your own X-pipe, a tip is to place the X-pipe union as far to the rear of the car as physically possible—it will make more power that way.


More HP
What can you expect from this modification? A major performance-car magazine did a test on a 350 small-block Chevy engine and the results were fairly spectacular. Torque at 3,000 rpm jumped by 20 lb.-ft. and horsepower increased by 13. These are increases in the useable part of the rpm range and should not only result in quicker acceleration but better fuel economy as well.


What we haven't commented on is the sound. Connecting the branches of the dual exhaust in this manner makes for the sweetest-sounding V-8 you can imagine. Instead of hearing the firing impulses of two disconnected four-cylinder engines, you hear all eight cylinders out of each pipe. What a difference.

**So with this said, i might just stay muffler and cat free, and just stick an X-pipe behind the rear differential.**

[keeedle]

Do you mind if you post a pic of your current setup?
I want to do a quad setup but am confused about what to do..
Muffler delete with Y-pipe to make it a dual? Or with a magnaflow single-in/dual-out to make it a dual?

[N0OS3]

I will take a pic next time i go into the shop to discuss. I should have done that to begin with actually.


They synopsis is this: From the OEM headers(x2), it is a 2-1/4" pipe. This feeds into your secondary catalytic converters, back to 2-1/4" pipe (x2). These two pipes feed into your resonator. The resonator is a single-out 3-1/2" molded pipe. This feeds to your muffler. The muffler then outputs (x2) 2-1/4" pipes [stock]... and if they came with fancy tips, they basically just slide onto your piping and welded.

My suggestion is that if you want LOUDER, go with just sticking a y-pipe onto the molded 3-1/2" pipe and out to make your quads. If you want quieter, then go with the muffler of your choice that has 3-1/2" in, to (x2) 2-1/4" (or 2-1/2") out to make quads.

[N0OS3]

Some more input:

Do you really need an exhaust system on your car? That’s a good question. If you have neighbors, drive it on public streets anywhere there are cops, or race it on virtually any NHRA track in the country, the answer is probably yes. Will it cost you power compared to open headers? Although that answer is also frequently yes, it can be no with the right system.

We’ve been running open headers on our ’86 Mustang project car since day one because it was the easiest thing to do and it seemed cool. It was also brutally loud, but it did pass muster at our local track because Los Angeles County Raceway doesn’t enforce a 95-decibel rule or require mufflers like many “street-legal” drag programs do. However, we always wondered if the open headers were costing us a little low-end torque due to a lack of backpressure. To find the answer, we took the car to Magnaflow Performance Exhaust’s research and development center. After discussing our combination and the way the car is used (100 percent at the track), Magnaflow built a system based on its universal X-pipe crossover and a pair of its stainless steel street series mufflers.

For any performance exhaust system, some type of crossover connecting the two sides of a dual exhaust system is important because it acts to balance the two banks of the engine. The common H-style crossover is good at balancing sound pulses between the two halves, but does little to promote scavenging because the exhaust gases tend to follow the path of least resistance, which is straight through each pipe rather than taking the 90-degree turn through the H-pipe into the other half of the system. In an X-pipe system, however, where the two sides of the system intersect, the gasses have no choice but to intermingle as they pass through the junction. This promotes improved scavenging effects by smoothing out uneven exhaust pulses from the engine’s firing order. It also helps quiet down the exhaust, resulting in a mellower, less raspy tone. According to Magnaflow, the faster acceleration of the gasses through an X-pipe causes them to flow in a linear fashion parallel to the walls of the tubing rather than tumbling. This “laminar” flowing gas is much quieter than tumbling gas, resulting in an exhaust tone up to 8 decibels quieter than a traditional H-pipe.

We left the car at Magnaflow for about a week, and when we came back we found that after some preliminary testing, the guys had built a really trick system consisting of 2-½-inch tubing from the header collectors into the X-pipe, 3-inch out of the X flaring into 3½-inch tubing running for about 26 inches before necking back down into a pair of 3-inch mufflers with turn-downs. The theory behind this design is that it will keep the velocity of the exhaust gases moving quickly through the headers into the X-pipe to maximize the scavenging effect, while the larger-diameter tubing ahead of the mufflers prevents the gasses from stacking up as they pass through the mufflers to avoid excessive backpressure in the system.

Sounds good, but would it work? To find out, we tested three exhaust-system configurations on Magnaflow’s in-house Dynojet. For a baseline, we ran the car with open headers and saw 333 hp at 6,300 rpm and 304 lb-ft of torque at 5,200 at the rear wheels. Next, we ran a 2-½-inch bolt-together system consisting of a BBK short off-road H-pipe designed to fit the company’s full-length headers connected to a set of race-type 2-½-inch welded mufflers with turndowns. Our Mustang’s carbureted 302 didn’t like this combo, as power fell to 323 hp at 6,300 rpm and 295 lb-ft of torque at 5,200. The increased backpressure also richened up the air/fuel mixture by about two carburetor jet sizes.

Finally, we swapped on the stepped X-pipe setup and were impressed to see power levels equal to the open headers: 335 hp at 6,300 hp and 302 lb-ft at 5,200. That’s a gain of 12 rear-wheel horsepower, although it turns out we weren’t really giving anything up or gaining anything extra from the open headers. So the car’s happy, and our ears are even happier!

Read more: http://www.carcraft.com/techarticles...#ixzz1pDhpLVCE

[N0OS3]

So i think i'm gonna go with an H-pipe, block back unrestricted setup... ^__^ i might try and stick my H-pipe right behind the rear differential right before the quads come out the back...

[Johnny D]

The X pipe should go as close to the front section of the exhaust as possible. Let me reword that...The X pipe should go directly after the final collection point of the exhaust.

I personally will be running a magnaflow X pipe resonator in the section before the secondary cats.

For an H pipe the location is generally used more for a tuning aspect. It's install location will depend on what tone you're attempting to generate/eliminate.

Very high level information and there is a ton more to it than that, but its the generalization to your questions.

[N0OS3]

Originally Posted by Johnny D

The X pipe should go as close to the front section of the exhaust as possible. Let me reword that...The X pipe should go directly after the final collection point of the exhaust.

I personally will be running a magnaflow X pipe resonator in the section before the secondary cats.

why close to the front?

I'm running an H-pipe though... from the multiple threads and articles i've read into, you keep the deep tone from an H-pipe without a lot of raspy effect.

[Johnny D]

Originally Posted by N0OS3

why close to the front?

I'm running an H-pipe though... from the multiple threads and articles i've read into, you keep the deep tone from an H-pipe without a lot of raspy effect.

I edited my post and added to it.


Generally the X pipe is installed just after the final collection point. (This term doesn't mean the final area that bolts up, but actually means the final location the exhaust gasses collect in the system)

The X pipe/H pipe debate could go on forever. Both are somewhat tune-able by changing installation location. However, it is generally accepted that the X pipe does the same thing the H pipe does, but with better scavenging benefits.

[N0OS3]

I would have to dyno to be certain, but for sound quality i'm gonna go with H-pipe for now... either way it's going to be better than my extreme torque loss experienced from going true dual all the way back... :/

[Johnny D]

Im going to order my stuff next week and install the headers. I cant wait. Like I said earlier, I'll be running the Magnaflow Tru-x muffler up front and a regular dual in/out in the rear 2.25" front to back.

[N0OS3]

Originally Posted by Johnny D

Im going to order my stuff next week and install the headers. I cant wait. Like I said earlier, I'll be running the Magnaflow Tru-x muffler up front and a regular dual in/out in the rear 2.25" front to back.

you know the MMW headers exit at 2.5", right? you're going to downsize?

I think after the crossover (H-pipe) i'm going to hike up the pipe size to 3" all the way back still... i hope it works out for me. ^__^

[keeedle]

Originally Posted by N0OS3

I will take a pic next time i go into the shop to discuss. I should have done that to begin with actually.


They synopsis is this: From the OEM headers(x2), it is a 2-1/4" pipe. This feeds into your secondary catalytic converters, back to 2-1/4" pipe (x2). These two pipes feed into your resonator. The resonator is a single-out 3-1/2" molded pipe. This feeds to your muffler. The muffler then outputs (x2) 2-1/4" pipes [stock]... and if they came with fancy tips, they basically just slide onto your piping and welded.

My suggestion is that if you want LOUDER, go with just sticking a y-pipe onto the molded 3-1/2" pipe and out to make your quads. If you want quieter, then go with the muffler of your choice that has 3-1/2" in, to (x2) 2-1/4" (or 2-1/2") out to make quads.

Thanks for the info.
I don't want my car to be too loud. I want it to be louder than stock but doesn't want it to sounds like a civic..
Do you have any muffler in mind that sounds good? I saw a lot of members using magnaflow universal mufflers to make their duals/quads. Any comment on those?

[Johnny D]

Originally Posted by N0OS3

you know the MMW headers exit at 2.5", right? you're going to downsize?

I think after the crossover (H-pipe) i'm going to hike up the pipe size to 3" all the way back still... i hope it works out for me. ^__^

It's only a 3.0L NA motor. Big diameter exhaust isn't worth it. Plus, if you compare diameter, dual 2.25" has more area than a single 3". Dual 2.5" is just to much for this motor. I'm going with 2.25" to keep the exhaust velocity high thus keeping the torque and hopefully gaining some power.

[N0OS3]

Originally Posted by keeedle

Thanks for the info.
I don 't want my car to be too loud. I want it to be louder than stock but doesn't want it to sounds like a civic..
Do you have any muffler in mind that sounds good? I saw a lot of members using magnaflow universal mufflers to make their duals/quads. Any comment on those?

Personally, i'm a fan of straight-pipe sound. If you can find a shop that will let you 'clamp' down different mufflers to your system to experiment with, that's your best bet, but to my knowledge, shops like that are very rare as most only keep scrap mufflers in stock and the new ones are always on order... :/

Originally Posted by Johnny D

It's only a 3.0L NA motor. Big diameter exhaust isn't worth it. Plus, if you compare diameter, dual 2.25" has more area than a single 3". Dual 2.5" is just to much for this motor. I'm going with 2.25" to keep the exhaust velocity high thus keeping the torque and hopefully gaining some power.

Do you plan on doing a dyno run after your exhaust is set up? I'd be interested to see the results. ^__^ i'll give you $1. hehe