Muffler Selection

[Badgaz]

wanting some advice on mufflers here...

currently i have 3 inch from the downpipe all the way back to a cobi resonator and then out an RPS muffler at the back. I've been thinking about changing the cobi to another muffler instead of a resonator so i've been looking at those.

a couple of questions

has anyone used a borla, vortex or a flowmaster muffler on an RB before?

is there any reason why you wouldn't use these? n/a vs turbo muffler etc?

[butterfly effect]

If you want a quieter, deeper sound with high flow try an AES muffler.

[Badgaz]

my wife has the HKS super Dragger i quite like that sound.

[C4a0s]

to the best of my knowledge...a muffler for NA would be smaller in diameter and more restrictive compared to one for a turbo application. besides why would u use a NA muffler on a turbo car?

[Badgaz]

i guess you're hitting the nail on the head...what makes a turbo muffler a turbo muffler? is it a straight through design? if thats the case many mufflers can be used.

[GTSBoy]

There is no such thing as a turbo muffler.

There are mufflers of various sizes with various levels of flow and sound attenuation. The bigger and less restrictive the flow path through the muffler the less the attenuation. You can get away with a bit less attenuation in a turbo car because the turbo itself does some silencing.

All it really means is that a muffler that is low restriction is better suited to a turbo than an NA if noise is a concern. Both engines benefit from having as little restriction as possible, turbos possibly benefiting more than NA.

[C4a0s]

Both engines benefit from having as little restriction as possible, turbos possibly benefiting more than NA.

yes... technically they dont call it a turbo muffler just a muffler suited for turbo applications...

also less restriction the better in general BUT I believe for NA cars, the exhaust system is more critical as in, they plan for the bends, lengths etc to encourage a better scavenging effect since the pressure of the gases leaving the cylinders is not as pressurized as a turbocharged car. this is probably why when u put ur hand at the exhaust opening (when its not so hot), u can feel the gases coming out in pulses..

at least thats wat i have read so far...

[C4a0s]

i guess you're hitting the nail on the head...what makes a turbo muffler a turbo muffler? is it a straight through design? if thats the case many mufflers can be used.

for turbocharged exhaust systems, scavenging effect is less critical i believe... thus designers usually just want straight pipes with minimal bends... thus they usually point sideways near the rear of the car...

as for the internals of the muffler... most aftermarket ones are straight thru with steel wool etc... totally unlike ur OEM designs... which are misaligned /disjointed pipes with tons of sound deadening stuff in the middle...

[GTSBoy]

also less restriction the better in general BUT I believe for NA cars, the exhaust system is more critical as in, they plan for the bends, lengths etc to encourage a better scavenging effect since the pressure of the gases leaving the cylinders is not as pressurized as a turbocharged car. this is probably why when u put ur hand at the exhaust opening (when its not so hot), u can feel the gases coming out in pulses..

Correct design for NA exhaust is that you have to get the primary lengths and the secondary lengths right (and the diameters right to get the velocities into the right range) in order to get your pulse tuning. After the collector at the end of the secondaries, you don't want to go too big a diameter pipe (in the aim of minimising restriction) because you still want to retain a decent gas flow velocity in the downstream pipe.

Turbo exhausts just want to get as big as practical as soon after the turbine as practical in order to get the back pressure as low as possible. A really excessively big diameter exhaust on a turbo that didn't need it to be that big might hurt power......maybe...... from the gas speed being too low and causing some problems that some people talk about but I have a hard time imagining. But in general that size is probably bigger than what you can actually fit into most cars anyway.

[scotty nm35]

Back pressure is a bit of a crock, it hurts power production on any setup.

On a turbo the rear housing is already a restriction causing back pressure, go too small and you lose top end flow and engine torque.

On an NA a restriction should be built into the merge collector imo, not in a reduced exhaust size for the entire exhaust length. The worst idea I have seen is those X pipes some of the V8 guys use, which apparently help with creating vacuum before the X for a reduced flow. Siamese merge pipes are much better design imo as they don't harm exhaust flow.

[gtr jet]

Hey Scotty, how much benifit do you think there is in have a merge in a V8 exhaust system?

My old mans designing his set up atm and is deciding on whether to put a merge in or not.

Engine a 500ci+ producing around 700-800HP. Primaries are 2.25 into a 3.5" collector down to twin 3" pipes.

Any tips or recommendations on mufflers?

[scotty nm35]

Yep, look up what a Siamese merge is, it's just a small slit between the two pipes, barely affects flow, but causes each pulse to create vac in the other pipe. Take some inspiration from the merge collectors on Burns Stainless site, they are some of the best I have seen.

Don't use Hooker mufflers, they have restrictors in them to quieten the exhaust volume. I gained 30kw changing to a Varex, both running 3.5 inch. Any straight through absorption muffler should be fine, the quality decides how long it lasts.

[GTSBoy]

I think the general concensus (amongst people who have actually dyno tested) is that a proper merge X at the appropriate point in a V8 twin system not only makes it sound 1000% better but is very helpful for making better power and a nicer shaped torque curve.

[gtr jet]

Cheers guys. He was gonna skip the merge to save the extra mucking around under the car but I might let him know to re consider.

[Badgaz]

so could I run a flow master then.....I want to try that just for shits and giggles

[nicksamaniac]

Is anybody still running a standard system?

my s1 Stagea still has the Nissan exhuast on it, with whatever cat they fit during compliance.

it's all 2.5" stainless and very well made, nice bends, well mounted etc.

As you'd expect from Nissan!

Only mod I've done is remove the "p&o cruise ship" rear muffler and fitted a 2.5"id- 4.5"od stainless eBay cannon and everyone asks if it's full after market as its reasonably loud.

[scotty nm35]

You have a stock stainless system? Must be rare, I have never seen one on a Stagea before. If it is a Jap system it won't be 2.5 inch, they only use metric tube.

V8 Soarers have stock stainless, as did the Golf I worked on the other week. Not many manufacturers use it due to their bean counters.

[nicksamaniac]

Sorry, 63mm then?

it has the Nissan emblem on the mid muffler box and on various bits I can see the Hitachi/unisia symbol.

And it definitely is stainless.

I also had (previously owned) a Holden hsv VS manta, and it had a pretty nicely made twin 2 1/4" stainless system.

But probably only due to being a HSV model. As it had HSV embossed in big letters on the muffler boxes.

Edited March 4, 2014 by nicksamaniac

[skyline1000]

Magnaflo will give you good tone and performance.