Hey all,

I was wondering, with the Magna being a V6, is there any benefit from a dual 2" exhaust, with a balance tube and dual cat converters. I'm thinking of a side by side system, not a split system, to keep the pipes in a factory location.

What's peoples opinion of my idea?

K.............GO!!!!!!

Cheers, Greg.

only problem is space down the tunnel

only problem is space down the tunnel

Not really, there's plenty of space to run the twin pipes under the car however you would have to re-route the exhaust under the rear suspension in the center of the car.

hmm interesting! Imagine using an AWD shell with FWD tranny and running big exhausts down the driveshaft tunnel!

Well in mine I can very comfortably fit a 3inch system in the current tunnel with room to spare.

Not really, there's plenty of space to run the twin pipes under the car however you would have to re-route the exhaust under the rear suspension in the center of the car.

Over the rear suspension is the easy part. The problem will be room down the tunnel. I have 1x 3 inch pipe in there now and its rather full..:) You might get a second pipe in there but wont get anything past the muffler. Mine splits just before rear suspension and then one out each side.

I couldnt see why you would want twin pipes all the way. You would need a rather big engine or it will lack back pressure.

But only running dual 2" pipes in a full twin system, with a balance tube to join the banks, similar to factory V8 Commy and Falcon exhausts.

My concern was the different length of the systems (front bank is longer than rear bank). I can fit pipes anywhere!! *lol* Routing wouldn't be an issue. I only plan to lower my car with lows, not superlows, so going under the rear suspension cradle won't be a problem! Oh, I'll be making the exhaust myself, I just wanted to run my idea past people who have dealt with these car for much longer than I have. I don't know everything, just enough to be dangerous! *lol*

Cheers, Greg.

I get the system your tryin to set up but yea most people on here with duals just have a single pipe that splits at the rear into two mufflers. Best settle with whats proven.

Yeah, you could run a big single say 3in, splitting into two 2in pipes. Should work ok. The 3in single pipe will actually flow more air than the 2 x 2in pipes. (if my maths are correct)

A fair amount of R&D would have to go into it I imagine.Both heads would have to flow exhaust gases at the same rate. Considering FWD V6 is arranged north-south, the front bank essenitally means the exhaust gas would have to travel further. This would impact the engine in some way I would have thought. That is why the current setup (which is well designed as standard) all flows into a single collector before making its way down the remainder of the system.

V8's and east-west V6's get away with this because the headers can both be the same length.

Yeah, you could run a big single say 3in, splitting into two 2in pipes. Should work ok. The 3in single pipe will actually flow more air than the 2 x 2in pipes. (if my maths are correct)
what this guy said

single 3" is around 7" squared
dual 2" is about 3" squared each pipe (6" squared)

Dual exhausts look tacky on cars that don't really warrant them. You'll make it look like the new range of mazda's who bang 2 pipes on everything =/

You could fit HM headers or pacies which makes the secondaries similar lengths and instead of having the two secondaries joining up, each continue to the back. There is plenty of room under the car to run a pipe outside of the tunnel. Heck, the AWDs do it. The AWDs also run the exhaust under the rear axel for better flow. The only reason the non AWD 3rd gens still had the exhaust going over the rear axel eventhough they have IRS, is because the wagons don't have IRS so instead of manufacturing two tyres of exahuasts they opted for the cheaper nastier option. They were, however forced to make a different one for the AWDs. Plenty of cars with east/west engine run dual exhaust (Subaru Liberty with its H6).

If its for performance... forget it! Tried and failed. (Lack of back pressure.) unless you Supercharge/Turbo your car.
But for looks and sound... GO FOR IT!

You could fit HM headers or pacies which makes the secondaries similar lengths and instead of having the two secondaries joining up, each continue to the back. There is plenty of room under the car to run a pipe outside of the tunnel. Heck, the AWDs do it. The AWDs also run the exhaust under the rear axel for better flow. The only reason the non AWD 3rd gens still had the exhaust going over the rear axel eventhough they have IRS, is because the wagons don't have IRS so instead of manufacturing two tyres of exahuasts they opted for the cheaper nastier option. They were, however forced to make a different one for the AWDs. Plenty of cars with east/west engine run dual exhaust (Subaru Liberty with its H6).

hmm interesting, so the AWD version of the rear exhaust is better designed than the FWD counterpart?

Cyber, you made a mistake in your comment. The Magna's V6 is E-W, and a Commy's V6 is N-S.

And 2 x 2" pipes will have a bigger cross sectional area than 1 3" pipe, and it would sound different to a big single system. I don't know if it would sound better or worse, just different! And would also get rid of the collecting merge pipe....it looks shocking from factory!

Cheers, Greg.

Cross section of a 3" pipe is 4.713" squared.

Cross section of two 2" pipes is 6.284" squared.

Thus, in theory, two 2" pipes will flow more than a single 3" pipe.

If my math is wrong, please correct me!

Cheers, Greg.

wrong

cross section of one 3 inch is 7.068" squared

Cyber, you made a mistake in your comment. The Magna's V6 is E-W, and a Commy's V6 is N-S.

And 2 x 2" pipes will have a bigger cross sectional area than 1 3" pipe, and it would sound different to a big single system. I don't know if it would sound better or worse, just different! And would also get rid of the collecting merge pipe....it looks shocking from factory!

Cheers, Greg.

yeah sorry wrong way round.

Which formula is which?

2 x pie x rad = ?

pie x rad(sq) = ?

One is square area, one is circumfrence, which is which?? *lol*

pie x (radius squared)

radius is half the daimeter of the pipe

so 3inch divided by 2 is 1.5

1.5 X 1.5 = 2.25

3.14 X 2.25 = 7.065 inch squared pipe volume


Extra info

2 2inch pipes

2 / 2 = 1

1 X 3.14 = 3.14

3.14 X number of pipes = 6.28

So I'm wrong then, a single 3" pipe will flow more gas than a pair of 2" pipes?

Oh well...scrap that idea then!!

yeah but not by much

and just to mess with ya head, 2 X 2 1/4 pipes have exactly the same volume as a single 3 inch pipe but the flow characteristics will be different a flow rate depending of whether you run an interfearance type system or not.

2.25 is a wierd size to buy mandrel bends in, it's either 2" or 2.5" for me!

I wonder what it would sound like (dual 2") with a 1.5" balance pipe welded in?

1.5" balance pipe?

I think that a 2" pipe may be borderline excessive for a 1.75L 3 cyl engine that would rarely rev to 6,000rpm.
I have no idea what a balance pipe would do other than interrupt flow and cause a bit of an obstruction.

If you can do it without a lot of cost, then I reckon you should go for it - at worst you can convert it to a system with REALLY long secondaries

ARS55 - You know what a balance pipe is, don't you? It allows a small amount of gas from each bank to merge, letting the pulses from each bank help to cancel each other out to (try to) avoid resonance and droning.

V8's use either balance pipes, or cross over "X" pipes. AFAIK, you use a balance pipe roughly 0.5" smaller than the pipe you are joining.

What are peoples opinions on a single 3" system then? Drone much on the 3.5 SOHC? Especially the auto.

Cheers, Greg.

Yeah I understand what a balance pipe is but why would you bother when making an X-pipe is so simple and offer so much better flow capabilities.

Basically you just cut the back side off 2 mandrel bends and weld the holes together. You can use either 90's (my personal preference) or you can use 45's.

Here's a pic of an X-pipe I made you can easily see how they are to do.

http://img687.imageshack.us/img687/7361/stainless100ser6.jpg

ARS5 that is awesome work man, you showed him thats for sure lol

Not sure if has been covered but a single larger exhause is better than a twin system as there is a lot less surface area.

Most race cars run a larger single system and often when the car was produced with a twin system this is removed in favour for a single

There is also no benefit in a NA engine going over 21/2 inch, forced induction you can go 3 inch

I would have to disagree with you there madmagna. I believe it was Rpw that proved a 3 inch system made more power and torque over the 2 1/2 inch system on the magna's. Also i'm not sure what race car's you look at but the v8 supercar's certainly don't run a single system. In fact they run 3 pipes out each side before the rear wheels. I will agree with you that on a street car with a 6 cylinder engine a single system would be prefered.

Yes, I'm a boilermaker / welder by trade and I know where you are coming from with the X pipe. To me, they merge the exhaust banks together and divide them again, a properly set up balance tube won't impede on each bank's flow, whilst still canceling out the nasty pulses.

And I was considering using the stock headers for the mean time too.

At the end of the day, a decent 2.5" free flowing single is going to be a better system, isn't it? The dual system sounds like fun but setting it up right is going to be a pain, and it still might sound like arse! And cost more too. Doubling up on cats, mufflers, pipe, bends, welding etc.

Ahhh.....it was fun while it lasted!

Cheers, Greg.

I'm a little late to the discussion, but yes, a single 3" is bigger than 2x2".
If you go 2x2.25" or 2x2.5" then you've got bigger than a single 3".

Yes, a single will be easier and cheaper, but then you're forgetting the coolness factor..
Take the paras for example. Everyone knows they are rubbish as headlights compared to the execies, but we all desire them cause they are cool... ;P

I'm a practical person, I'm not going to spend all that money just for the 'cool' factor. If it is a proven gain, it's worth it in my books. This isn't a proven gain yet, and I'm not spending my money to find out either!!

I'm a little late to the discussion, but yes, a single 3" is bigger than 2x2".
If you go 2x2.25" or 2x2.5" then you've got bigger than a single 3".



Have to pull you up on that one mate. 2X2.25 has the same internal diameter as a single 3.

Yes has the same internal Dia but what about the side wall surface area, this is where the issues are

As for the current touring cars, these dont really even have an exhaust to speak of, I am talking about cars more in the line of the magna engine in capacity etc etc

With the older holdens many used to ditch the 2" twins on the old 253 engines in favour of an 2 1/2 inch single system. I know these are very different engines but even if you look at the 5.0 ford engine which has more volume, many have done the same thing in the past with the only people to keep the twin pipes having done so for sound and not power

As for RPW, I would take anything they have done with a grain of salt as many around here know how bad a lot of the products from that place have been.

I have played with many exhausts on Magnas and to date have had best results out of 2.25" inter dia pipe, high flow cat good clean flowing muffler and resinator

Mal, bit OT but in your experience are aftermarket extactors like pacemakers worth it over the stock item, especially if an SKR or similar tune is a definate down the track?

Look, the stock engine pipe in the magna FWD is actually a very good design for a stock set up.

If you are chasing power or want to move where the power is made and you are then going to add other things like cams, tunes etc then perhaps a reasonable investment.

I do not like Hurricanes, personally I like either Pace Maker or HM

You could fit HM headers or pacies which makes the secondaries similar lengths and instead of having the two secondaries joining up, each continue to the back. There is plenty of room under the car to run a pipe outside of the tunnel. Heck, the AWDs do it. The AWDs also run the exhaust under the rear axel for better flow. The only reason the non AWD 3rd gens still had the exhaust going over the rear axel eventhough they have IRS, is because the wagons don't have IRS so instead of manufacturing two tyres of exahuasts they opted for the cheaper nastier option. They were, however forced to make a different one for the AWDs. Plenty of cars with east/west engine run dual exhaust (Subaru Liberty with its H6).

Subaru liberty H6 is not an east/west, no boxer engined Subaru has an east west engine, and it doesn't run a full twin system, it splits after the rear suspension, sorry to pick but I just had to point that out, I'm a bit of a soob nut

Correct me if I'm wrong but my understanding is that flow is the most important thing in an exhaust on an N/A car, and putting huge dia pipe reduces flow, even if it increases volume, thats why when I do the exhaust on my wagon I'm going with 2.5 stepped down to 2.25 over the rear axle then back up to 2.5 tail pipe, this should create a venturi type effect thus drawing the gasses out and increasing flow.

You would need a rather big engine or it will lack back pressure.


2x 2" pipe is small than 1x 3" pipe,
but i do agree single 3" down the centre into twin at the back,

didnt EZ boy try this along time ago???

Subaru liberty H6 is not an east/west, no boxer engined Subaru has an east west engine, and it doesn't run a full twin system, it splits after the rear suspension, sorry to pick but I just had to point that out, I'm a bit of a soob nut

Correct me if I'm wrong but my understanding is that flow is the most important thing in an exhaust on an N/A car, and putting huge dia pipe reduces flow, even if it increases volume, thats why when I do the exhaust on my wagon I'm going with 2.5 stepped down to 2.25 over the rear axle then back up to 2.5 tail pipe, this should create a venturi type effect thus drawing the gasses out and increasing flow.

I understand where you are coming from, but surely a big V6 like a 3.5 doesn't need to worry so much about removing exhaust gases to such extremes? On a 2.0 4cyl yes I would agree...

I understand where you are coming from, but surely a big V6 like a 3.5 doesn't need to worry so much about removing exhaust gases to such extremes? On a 2.0 4cyl yes I would agree...

I have been led to believe that the XY GTHO's ran this type of system and is a big reason as to why they preformed so well at bahturst and the like, so I figure that theres no harm in trying and it's not like it's going to cost me a fortune, because I can get the pipe and do all the cutting, bending and welding at work, all I have to buy is the pacies, muffler, cat and the resinator...

XY GTHO's actually stepped down to dual 2" pipes to go over the diff, and stayed at 2". Apparently the step down made them sound better!

Actually the XY's ran a full 2inch dual system right from the manifolds.

Hey all,

I was wondering, with the Magna being a V6, is there any benefit from a dual 2" exhaust, with a balance tube and dual cat converters. I'm thinking of a side by side system, not a split system, to keep the pipes in a factory location.

What's peoples opinion of my idea?

K.............GO!!!!!!

Cheers, Greg.

I also considered this after noticing plenty of room for a muffler on the left hand side of the TF, but dismissed it because, apart from the cool factor, there really isn't much going for it to offset the increased cost and complexity, unless you are supercharging or substantially increasing the engine power some other way.

The smaller tailpipes would prevent the low frequency droning that plagues people using oversized exhaust tips (remember when they used to be called "resonator tips", back when "personalised plates" were called "vanity plates"?), but a sensible tailpipe can also do this - check out luxury performance cars fitted with large tailpipes as standard equipment and you'll see a splitter plate to prevent the low frequency droning.

A sensible single system should do a perfectly good job at a lower cost (and weight) that a twin system for just about any Magna. According to flow testing by Dynomax, one of their single 2.25" straight-through mufflers (Ultra Flo Welded model number 17561) will flow 273 BHP (203 kW) (see http://www.dynomax.com/assets/2008catalog_pdf/ultraflowelded.pdf). The way they define "Loss Free Horsepower" is based on flow bench testing where the flow figures were calibrated against dyno testing done by David Vizard and from memory of his article he used a 1% power loss as his criteria (so a 273 BHP engine would actually make 1% more power with no muffler). Their 2.5" muffler from the same range is good for more than 450 BHP, so a 3" system is a bit over the top for almost all cars. An oversized system results in reduced torque because the exhaust loses momentum instead of making way for more fuel and air.

If you did decide to go for a twin 2" system, you could use "turbo" style mufflers, instead of straight-through mufflers for a more subdued sound. It's still a performance sound, just quieter and less raspy. For a comparison, check out the Dynomax Super Turbo vs their Ultra Flo models on their "Sounds of Dynomax" (http://www.dynomax.com/soundsofdynomax.php), although I'm guessing your Magna doesn't sound too much like the big block V8 that they use. This is not meant to be an ad for Dynomax (whose range is available locally rebadged as Lukey), it is just that I have not been able to find any other manufacturer that provides flow performance data. Similarly designed mufflers from other manufacturers should have comparable flow performance and all other things being equal, the larger the muffler body (not the inlet and outlet pipe sizes), the quieter it will be.

Attention exhaust system manufacturers: flow (and acoustic) performance data for your products would be appreciated.

There is no need for a balance pipe on a V6 (or single-plane crankshaft V8) - the cylinder banks would be better off kept separated because they run like two synchronised 3 cylinder engines and there is no positive cylinder scavenging effect from combining the exhaust pulses from the other cylinder bank. Balance pipes are useful on dual-plane (or "cross-plane" according to Wikipedia - http://en.wikipedia.org/wiki/V8_engine#Crankshaft_design) crankshaft V8s due to the prohibitive complexity of an optimal manifold design that combines cylinders from opposite banks such as the one used on the Ford GT40 and known as a "bundle of snakes" (see http://forums.audiworld.com/showpost.php?p=15600075&postcount=13 or http://www.kitcarmag.com/featuredvehicles/0611kc_superformance_spf_gt40/photo_02.html for a modern version).

All that being said, if you have an abundance of 2" aluminized tube, catalytic converters, mufflers and inspiration, there is no technical reason you shouldn't go for it.