3.3TT 'Prototype exhaust' - Buy or avoid?

[Justin B]

I have the opportunity to pick these up tomorrow.

Interesting idea with the cutback straight pipes though not a fan that they sit above the mufflers rather than next to or below.

Not sure how they would sound exactly & are not currently installed on a car so cannot hear before purchase. 110% will drone, possibly unbearably.

The real question. For $120 AUD, would you try these???

I'm not sure if I can restrain myself since I didn't get the bimodal (factory is sooooo quiet). I guess I should make it clear - I'm not looking for performance, just sound.

 

[Matt77]

I have the opportunity to pick these up tomorrow.

Interesting idea with the cutback straight pipes though not a fan that they sit above the mufflers rather than next to or below.

Not sure how they would sound exactly & are not currently installed on a car so cannot hear before purchase. 110% will drone, possibly unbearably.

The real question. For $120 AUD, would you try these???

I'm not sure if I can restrain myself since I didn't get the bimodal (factory is sooooo quiet). I guess I should make it clear - I'm not looking for performance, just sound.
View attachment 39846

That axleback exhaust has J pipes (simular to Helmholz resonators) which aim to kill the drone. No way of knowing if they are tuned correctly to reduce the right frequencies until you fit them. For $120 I'd give it a go.

 

[Justin B]

That axleback exhaust has J pipes (simular to Helmholz resonators) which aim to kill the drone. No way of knowing if they are tuned correctly to reduce the right frequencies until you fit them. For $120 I'd give it a go.

Never heard of Helmholtz. I appreciate that, something new to learn.

Checked wiki & it gave this gem:

"Helmholtz resonance sometimes occurs when a slightly open single car window makes a very loud sound, also called side window buffeting or wind throb."

Definitely familiar with that one. It will be interesting to see what the current owner says as I assume he was the one who fabricated the pipes.

 

[Aarvix]

Those are 1/4 wave resonators. Like Matt said, they're similar to helmholz, but the tuning is different.

They work by reflecting the sound back into the exhaust stream 180 degrees out of phase, effectively cancelling out a targeted frequency (usually a very narrow band). The length has to be exactly 1/4 of the wavelength of the nuisance frequency (1/4 in + 1/4 back = 1/2 wave AKA out of phase).

I'm considering building some for my MBRB to tune out the annoying 106Hz drone at 2000-2200 RPM, just have too many projects ahead of it ATM.
I calculated somewhere around 30-36" for my drone, but there's no way to know what that exhaust needs.
I'd probably still buy it, seems like a fair price and the "J-pipe" can always be lengthened or shortened if it's not quite right.

Helmholz resonators work on the "springiness" of air. Blowing over the top of a bottle is an example of helmholz resonance. The math is more complicated, but the effect is the same (cancelling out sounds).

 

[Justin B]

I purchased them but they don't fit my midpipe flange. Guy I bought them off said he had them fitted but I don't know how...

 

[YOWStinger]

For 120 I’d do it, no question