A Small Rant

IMO it's due to the confined space in which a tether car engine operates. The sound it thus magnified.

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SuperDave wrote:IMO it's due to the confined space in which a tether car engine operates. The sound it thus magnified.

I think that prop engines are louder even though to all
Of us they seem less loud this is because a spinning wheel creates hardly any noise but a spinning prop makes a whirring sound and changes the way things sound kind of like singing into a fan. When you sing into a fan the sound waves are interrupted every time a blade passes through them so they sound different i believe the same thing goes for engine sound so the sound is lot louder just distorted so we get a different frequency.

So the prop-wash distorts the sound waves. Now I also know why pushers are louder than pullers. I don't have it in a car, just in a vise.

How did 1970's kids survive the noise?

One of my BWs is louder than the others. I can't imagine what could be different. It runs fine, fast and steady, but I don't have a tach so I can't swear it's identical.

RknRusty wrote:One of my BWs is louder than the others. I can't imagine what could be different. It runs fine, fast and steady, but I don't have a tach so I can't swear it's identical.

might sound silly but are you sure it going in the right direction.
maybe it has slightly larger exhaust ports.
here is an attempt to quieten down a g mark using a drinks bottle but it didnt seal too well so you can hear it is not as quite as it could be i now have made a smaller one that is quieter.

nitroairplane wrote:

RknRusty wrote:One of my BWs is louder than the others. I can't imagine what could be different. It runs fine, fast and steady, but I don't have a tach so I can't swear it's identical.

might sound silly but are you sure it going in the right direction.
maybe it has slightly larger exhaust ports.
here is an attempt to quieten down a g mark using a drinks bottle but it didnt seal too well so you can hear it is not as quite as it could be i now have made a smaller one that is quieter.

that exhaust port size definitly makes a dif. the super bee has much larger ports than a regular BW.
the gaps are much wider. but there is one other thing that could make a difference:
the speed of the injected mixture.
1.Pressure: as we all know, before it is injected, it is compressed in the crank case.
if you have ever turned the engine over without the head on, you will have noticed that the air that
bursts up from the OPs already seems to have quite some pressure, and a very distinguishable sound, even
when the engine is turned slowly. so imagine these gases at 17000 rpm...whew, the piston comes down pretty damn fast, so the gases shoot up into the piston, driving the exhaust gases out with even MORE speed and pressure.
2.temperature:
just a crude theory, but when the by comparison much cooler mixture is subjected to the very hot
environment of the cylinder, that has just fired, it will expand VERY rapidly (especially the very volatile nitrometh
=> 1st one of the nitroalcanes, in nerd speak), so that might cause an even more rapid exit of the gases out of the engine.(more pressure = louder audible sound).
if you take a look at the old thin-walled engines, you will see
that there's not much room for the gases to overflow (compared to the thick, generous ports of a BW).
which theeeeeeeeen means more pressure buildup in the overflow channels and a higher injection velocity=>
higher exit velocity and pressure of the exhaust.
ok, so there's my theory on fluid and gas dynamics in a cox engine, its your turn now, SuperDave

GermanBeez wrote:

nitroairplane wrote:

RknRusty wrote:One of my BWs is louder than the others. I can't imagine what could be different. It runs fine, fast and steady, but I don't have a tach so I can't swear it's identical.

might sound silly but are you sure it going in the right direction.
maybe it has slightly larger exhaust ports.
here is an attempt to quieten down a g mark using a drinks bottle but it didnt seal too well so you can hear it is not as quite as it could be i now have made a smaller one that is quieter.

that exhaust port size definitly makes a dif. the super bee has much larger ports than a regular BW.
the gaps are much wider. but there is one other thing that could make a difference:
the speed of the injected mixture.
1.Pressure: as we all know, before it is injected, it is compressed in the crank case.
if you have ever turned the engine over without the head on, you will have noticed that the air that
bursts up from the OPs already seems to have quite some pressure, and a very distinguishable sound, even
when the engine is turned slowly. so imagine these gases at 17000 rpm...whew, the piston comes down pretty damn fast, so the gases shoot up into the piston, driving the exhaust gases out with even MORE speed and pressure.
2.temperature:
just a crude theory, but when the by comparison much cooler mixture is subjected to the very hot
environment of the cylinder, that has just fired, it will expand VERY rapidly (especially the very volatile nitrometh
=> 1st one of the nitroalcanes, in nerd speak), so that might cause an even more rapid exit of the gases out of the engine.(more pressure = louder audible sound).
if you take a look at the old thin-walled engines, you will see
that there's not much room for the gases to overflow (compared to the thick, generous ports of a BW).
which theeeeeeeeen means more pressure buildup in the overflow channels and a higher injection velocity=>
higher exit velocity and pressure of the exhaust.
ok, so there's my theory on fluid and gas dynamics in a cox engine, its your turn now, SuperDave

very nice Dave and Dave.

heeeeey, that was all mine

That drink bottle thingy was no silencer in fact it wasn't even a muffler because the engine sounded loud to me.

Who is kidding whom? You Brits are confused here.

SuperDave wrote:That drink bottle thingy was no silencer in fact it wasn't even a muffler because the engine sounded loud to me.

Who is kidding whom? You Brits are confused here.

Ok lets say Baffler as the middle ground.
http://en.wikipedia.org/wiki/Silencer

SuperDave wrote:That drink bottle thingy was no silencer in fact it wasn't even a muffler because the engine sounded loud to me.

Who is kidding whom? You Brits are confused here.

Also i have now much improved that Baffler now it is much quieter.