Bore x stroke - affects exhaust sound?

[JT]

bore and stoke affects the amout of gas passed
bore x storke = cc's per cycle
increase ehither one and the passed volume increases
so ye therotically thought the sae exhaust the sound can change
but it wouldnt be a lot
and most probably barly audible


simple physic's really...isn5t it ??


v

Simple physics but you forgot the pie!
(((1/2 bore) squared) x pi) x stroke = cc

my typing skills are not as good as your i have no problem agreeing with that
but whats the point of be able to type when you have no idea what your tring to convay......

a rebore wont affect sound in the real world and is not a sugnificant change in the dynamic where as a larger cam is a considerable differance to both effencency and dynamics
as i have said

maybe you need to go back to school and get a education to go with you typing skills so that you dont end up looking like a total dipshit

i did not do that you did it to yourself,......

v

The topic is about the same displacement engine, and what happens to the sound when a different bore x stroke combination is used.

He never said it wouldn't change the sound. Read the thread again.

With your knowledge you shouldn't need to resort to calling people names .

[vvega]

i was giving examples of what can cause the sound to be different
in general......
i wasent been specific and that is my choice not to be
thre is no rule that states i have to do that.....
dont see why hes got such a issue with it


v

[ChaosAD]

I know you are but what am I??

I know you are but what am I??

I know you are but what am I??



Quit the bitching kids.

I think the boxer sound has something to do with the exhaust manifold design (as I think has already been pointed out) because if you change the manifold to a properly designed one it aparently smoothes out the boxers rumble.

[RomanV]

Well in all fairness to VVEGA my question was kind of misleading.

What I really should have asked was 'does a big cylinder bore (relative to stroke) contribute to a pulse effect in the exhaust manifold.'

But it seems we have established that the unequal extractor length is the major contributor to the 'suby sound'.

CASE CLOSED!


Unless anyone else has some useful information to contribute.

[CozmoNz]

Unless anyone else has some useful information to contribute.

Yes

cams. Boy oh boy, they dont change the note of an engine at all do they!

Duration / lift obviously also makes a huge difference in the note. Maybe this is why porshe sounds so much nicer than subaru?

[jondee86]

Ha Interesting topic for a quiet night !!!

The engine noise is caused by pressure pulses released by the exhaust. When the expansion stroke of the engine comes to his end, the outlet valve opens and the remaining pressure in the cylinder discharges as a pulse into the exhaust system. These pulses are between 0.1 and 0.4 atmosphere in amplitude, with a pulse duration between 2 and 5 milliseconds. The frequency spectrum is directly correlated with the pulse duration. The cut-off frequency lies between 200 and 500 Hz.

Sooooooo...... it would seem that valve timing has an effect (the earlier
the exhaust valve opens, the higher the residual pressure in the cylinder)
and, cam profile. A cam that opens the valves quickly will give a stronger
pulse than a cam with a slower opening rate.

When the pulse frequency coincides with the resonant frequency of the
exhaust system (as it does with my car at about 4200 rpm) you get a
wicked crackle !!! The factory rear silencer is tuned to kill this frequency,
and does a great job, but at $500 plus a pop, they don't sell many

Cheers..... jondee86

[dohca]

i hope this hasent been said, i cant be bothered to read it all.

one of the main reasons the subarus "rumble, bark, drain pipe" etc is due to the manifold setups

esp on the single turbo

cant remember the entire 100% reason but thats defanatly one
edit:

seems a few people have said this