Exhaust J pipe or Helmholtz Resonator

[AliK]

I’ve been thinking about experimenting with this for some time now and for some reason it’s really piqued my interest again!

I have a torque hole at around 2.1-2.5k rpm range - which I’ve mostly dialled out with tuning the carbs / needle experiments - but it correlates with exhaust drone / resonance. It’s not the sort of unbearable drone but it’s definitely a resonance that I know is there.

So I’m tempted to experiment with a J pipe or a resonator cavity. At present it’s just a thought experiment and learning, so nothing I plan to do right away,

Given a 120hz centreline of the target frequencies, it’s looking like a c. 86cm pipe which I can fit in one of 3 locations on the car, but a Helmholtz cavity would be much more compact if one can calculate it accurately with the myriad of variables in the equations.

There are tonnes of internet resources on the topic but out of curiosity, has anyone done this on a Z / L6 engine that we know of?

 

[SeanDezart]

Or you could go for one of my titanium exhaust lines later this year......

 

[AliK]

Well that sounds interesting!! I imagine a heck of a weight saving. My titanium bikes ring like a bell if you strike them - would be interesting to see how that translates into an exhaust sound. .

Although my understanding is that the frequency / resonance in echiasts is more a function of the number of cyls and RPMs than the material itself!

 

[Rob Gaskin]

I remember whan I replaced a Cortina mild steel exhaust with ss. It was tinny, but these days they seem to have overcome that.

 

[SeanDezart]

I remember whan I replaced a Cortina mild steel exhaust with ss. It was tinny, but these days they seem to have overcome that.

True, a stainless over a mild steel can sound tinny whilst a titanium line doesn't. Light is right and I'll be doing a limited prod run so as to have 1x and a spare for my race Z.
If a demand develops, I may make more but they-'re not the same price as stainless !!!