pappasmurf

....what principles in constructing back boxes do the manufacturers use to get so many different tones and noise levels?
Is it all to do with the size of the barrel and what they put in them?
How is it some are loud and bassy?

smurfy.

davedipster

It's an interesting science you know, have a look in howstuffworks.com under autos and mufflers.

Dipster

sKunk

It depends on engine type as well.

A straight 4cyl sounds crap compared to a 4cyl boxer which sounds crap next to a v6 (TVR *drool*)............ -> v8 etc....

wez_sti

in a nut shell, the bigger the box/exit, the deeper the noise, same concept for drums, trumpets etc...

sound travels further = longer amplitude = lower frequency

ex-webby

exhausts are bloody complex if you're **** enough to look into it deeply. I certainly don't understand it all, but there are a number of complexities surrounding harmonics...

Any object has a resonent frequency.. meaning the frequency at which it as a whole resonates (don't ask me anything more complex than that!! )...

The size, shape, imperfections, etc, etc of each section of the exhaust has different resonent frequencies.. this means that the harmonics of the exhaust system as a whole has an effect on the sound, but also the performance creating different types of back pressures, etc at different revs.

Aparently, it's possible to make a new system, and it be fabulous, except at a certain rev range, where you'll end up with a massive drop in power (i guess that's called a flat spot??).. and you can work out what's causing that, and eradicate it only to create a different one, etc, etc, etc.

This happens to a lesser or greater extent in all exaust systems, better performance in some areas which creates worse performance in others.

Tuning this and a number of other areas such as flow rate, etc are what seperates a good exhausts system with an average one.

Cheers

Simon

sulli

On a similar note (Pardon the pun) can the design of the exhaust dramatically affect power output?
Mine is a handmade Sti backbox and matching 2 1/2" centre pipe (backbox is £1000 only available from Sti Japan), and I reckon it has dramatically increased the cars power from standard - if I was to guess i'd say 250bhp from a formerly standard car (apart from proper plugs, filter, fuel, proper oil every 3k etc) going on my performances against other imprezas, including WRXs.

Is this a tad hopeful from just exhaust mods, and could it be better than other makes of exhaust performance wise?

ex-webby

sulli

yes, a well designed and constructed exhaust system can have a substantial effect on the performance of the car.

All the best

Simon

wez_sti

I remeber seeing a thing on top gear about Z3's (i hate them personally) but any way, the car was approx 20-30bhp less than what it could of been because there wasnt enough room to make the exhaust long enough and exactly the right shape, so as the wise administrator says, can make a big diff!