Titanium Exhaust Drone

[Deano 1]

I'm sure you'll find it a lot more than 5kg mate, more 15kg

[Ronin 09]

I'm sure you'll find it a lot more than 5kg mate, more 15kg

yeah ok so 15kg saving on a 1500kg road car = 1%. WIN.

you're probably right but the point is that chasing weight saving from a titanium exhaust on a full weight road car is a bit silly.

[kaneryan]

I think he was generalising, as an example

[Ronin 09]

ronin 09.

Cheers for the help,

Im not fussed about weight, TI sound would be good... But im just after getting rid of the drone it has and making it a tad quieter as its a bit louder than what I thought it would have been.

Cheers

You're going to have to get something with a centre muffler, or at least a reasonable size resonnator. Dicking around with wrapping the exhaust defeats the purpose of a nice system in my view - it's a bit band-aid solution.

So options come down to:

1. cut and insert a muffler in the mid section (don't know how easy or hard this may be with Ti)

2. sell yours and get another ti system with a centre muffler

3. sell yours and get a custom made one that is quieter with a centre muffler

I went option 3 because it means the car is only slightly louder than stock, so it can be booted around on WOT happily without getting the look of death from other road users.

My view is that the louder it is, the less you're inclined to enjoy it (at least in Vic where the popo are draconian).

[Serpandrew]

My view is that the louder it is, the less you're inclined to enjoy it (at least in Vic where the popo are draconian).

This man speaks the truth

[KiwiRS4T]

I went option 3 because it means the car is only slightly louder than stock, so it can be booted around on WOT happily without getting the look of death from other road users.

My view is that the louder it is, the less you're inclined to enjoy it (at least in Vic where the popo are draconian).

I want maximum flow so I have what is essentially a noisy system but drive round normally with a "silencer" which makes it a bit more acceptable noise wise but probably costs 10% of the power. I take it out for tuning and on the track.

[GTR-N1]

I'm sure you'll find it a lot more than 5kg mate, more 15kg

Yup...

And some people have a distinct justified intention of lessening the weight.

The downside of some brands of Ti, is that a bit of the RB sound gets lost.

But fortunately with my dumps & Y, it's still there.

[simpletool]

Single muffler - that is your problem. No single muffler Ti exhaust is gonna be quiet

Only way to fix it - add a decent middle muffler, or buy another exhaust.

OR fit a side-branch resonator. Will fix the drone for sure, but it'll be some interesting fabrication work.

[dkbcleaner]

Terry are those true equal length front pipes? They look longer than the midori ones

[kaneryan]

Would a side branch resonator make the exhaust a bit quieter? Also is the formula easy to work out? And where would I place it in my exhaust?

[dkbcleaner]

My view is that the louder it is, the less you're inclined to enjoy it (at least in Vic where the popo are draconian).

I think this is only half true. Most of us gtr owners are running over 300rwkw and you cant go wot everywhere anyways. So you need to pick your spots. The gtr motor produces such a beautiful sound that for me half the driving experience and enjoyment comes from the sound it makes.

[GTSBoy]

Would a side branch resonator make the exhaust a bit quieter? Also is the formula easy to work out? And where would I place it in my exhaust?

A resonator is intended to damp out the sound at a given narrow frequency range. So, yes, if you have a particularly bad "drone" that is louder than you'd like, then if you can measure that frequency you plug it into that linked formula and it spits out how long the branch needs to be to attenuate that frequency. You can only get a certain amount of attenuation though. You can't kill all of the noise at that frequency. And you may find that killing a drony frequency might make something else sound terrible. That's why acoustic engineering, whilst having a lot of hard science to base calculations etc on, usually comes down to experimentation and tuning to come up with something that sounds nice.

And yes, the formula is dead easy. Just plug in the gas temp (sadly in degrees Rankine, but at least they give the formula there and you can easily convert temperatures using Google anyway) and the frequency and it tells you how long to make the branch. You have to know what frequency you want to kill, and you have to have a good idea what the gas temp is at that point in the exhaust.

You place it where it will fit.

[kaneryan]

wow! I dont have a clue what ur talking about haha, gas temperature? and how do i find out what frequency the drone is at?

[GTR-N1]

Terry are those true equal length front pipes? They look longer than the midori ones

Now I need a piece of string - lol

The Mine's is more equal in length than the HKS which looks more equal in length than the Midori.

Before the join in the pipe, you'll notice how Mine's created more of a bend in the 'straight' section to accommodate the wrap-around.

[GTSBoy]

wow! I dont have a clue what ur talking about haha, gas temperature? and how do i find out what frequency the drone is at?

Well, that's the point isn't it? You need to measure the temperature of the pipe at the point where you propose to mount the branch. You need to do so when driving at the sort of load that causes the drone (so as to get the gas temperature that pertains to that condition, not the hottest gas you'd get when fanging it, for example). You need to try to measure it in such a way that it gives you a reasonable estimate of the gas temperature. I would do this by putting a thermocouple against the pipe then wrapping a lot insulation around it to keep the pipe from loosing much heat at that location. Job done.

To measure the frequency you'd need a spectrum analyser, or quite possibly there's an iPhone app for it nowadays! You could just record the sound then put it into a computer and look at the frequencies that are present and look for a big spike at about the sort of frequency you'd expect for the drone (probably a few hundred Hz). Job done.

[R31Nismoid]

OR fit a side-branch resonator. Will fix the drone for sure, but it'll be some interesting fabrication work.

Great idea on paper......

But tell me where you can fit that under the ass of a GTR and still have a reasonable ride height - because a lowered GTR you only JUST have enough room to fit a 4" exhaust with dual mufflers and even then you are usually around 80mm-100mm

There is no room for anything extra. Hence go dual mufflers and you don't have a problem anyway so it kinda cancels itself out.

[Ronin 09]

I want maximum flow so I have what is essentially a noisy system but drive round normally with a "silencer" which makes it a bit more acceptable noise wise but probably costs 10% of the power. I take it out for tuning and on the track.

I perhaps should have been more clear; the 90mm is straight through with no loss of power; I don't have to dick around with removing or refitting any baffles or silencers between road/track.

The system has two very large and well made (by hand) mufflers that simply work. It belts out ~340kw at the wheels every day.

Also, as noted by dkbcleaner, i do love the sound of an RB, and when it is high in the revs it still makes a great sound - albeit quieter than a Japanese 3" exhaust.

but I'm not here to justify my choice; your circumstance may be different and therefore you seek something different. Just trying to help kaneryan get to an acceptable solution for his problem.

GSTBoy: your solution is technically robust and elegant, but do you really think it is logistically feasible? where would you put it? Floorpans are limited so you could only really put it where the centre muffler should be. But is that where it's needed? Can you get one made of Ti? Otherwise you need to cut the existing ti, insert a ti flange, get a stainless resonator, bolt on? Sounds complicated and expensive. Plus all the dicking around to find the resonant frequency. Robust and elegant, potentially, practical, no.

[Ronin 09]

Great idea on paper......

But tell me where you can fit that under the ass of a GTR and still have a reasonable ride height - because a lowered GTR you only JUST have enough room to fit a 4" exhaust with dual mufflers and even then you are usually around 80mm-100mm

There is no room for anything extra. Hence go dual mufflers and you don't have a problem anyway so it kinda cancels itself out.

fark, ash. what he said.

[GTSBoy]

Not my solution. Just explaining how you do it based on my 5 second look at the attachment in #48.

FWIW, branch resonators and similar ideas are technically elegant. Just not always feasible, as outlined by R31 et al above.

[kaneryan]

Well I think this branch resonator looks like heaps of work and yes since getting under the car the other day, there isn't alot of room at all.

I think im going to insert a mid muffler and take out the resonator, as its the easiest way, and im not looking about weight issues, as this car is not a 600hp track car, im just after the exhaust to loose its drone and be that tiny bit quieter,

You miggt say sell it and buy another one, but I waited 3 months for this exhaust to get here... I love the look of it, and want it to work, as in ive waited this long dont wanna just turn around and sell it

I know people have thoughts about what I just said so shoot them at me

Also add what type of stainless muffler I should get based on previous knowledge and use along with your thoughts