...woooaaarrrrwoooaaarrrwoooaaarrr? I took my father for a drive, and asked him why cars don't have an even hum at high steady rpms. We were driving on the highway 70mph with 3.80 gears, so somewhere around 4000 rpms, and I was listening to the "wavering drone" of the engine, and told him "that is why I don't need a stereo...I love the "beat" of this "music"." He said that his old big-block '69 RoadRunner sounded just like it. But, he said that he went to some races many years ago, and noted that all the cars but one had that waver, the other one just a solid single-toned drone. I suggested that maybe uneven cylinder pressures cause a resonance in the engine sound. He didn't know. Maybe a "perfectly balanced" engine would not resonate? Is it uneven weight distribution? Uneven pressures? Any ideas?
My 6 cylinder just has an even drone to it. Especially when it used to be in the '74 which had dual glass packs. My '72 has stock exaust, so I can't really hardly hear it over the wind and road noise at 70-75 mph. Now my dad's '95 Mustang GT kind of has that in and out drone to it on the interstate. Almost sounds like it has something to do with harmonics to me.
it has something to do with # of cylinders as well as block shape and design. if you listen past the exhaust, youll notice that a v-8 is different in sound from a v-10. you will also notice that the subaru, volkswagen and porsche all sound similar and are different from an i-4. my favorite way to experience this is at air races. some v-12s competing against 32 piston radials and smaller radials in the t-6 class. even the radials sound different, (some have more pistons some less). i was told it has to do with the overall balance and how the reciprication strokes work out
i think its has something to do with the balance of the engine and how many cylinders its firing and even if it has cylinders, for example maverick at 70 (scary thought right now) my protege, or lets say for example an rx-8 sound very different, rx-8 being the smoothest, i think its cause it dosent have any cylinders?
here is my exlpanation.. not sure if its correct but it has to do with an unbalance in the engine... the pistons are all rotating and not everything is perfect.. ever.. then the exhaust goes through the bottom of the car and reverberates off the ground... and all this is while driving, so you get the air noise rushing over the car and causing the sound waves to bounce around under the car... then at a certain speed it all kinda just goes with the flow and evens out...
Just my opinion Guys i believe it has something to do with carburetion/ mixture in cruise mode. My (port) fuel injected vehicles dont seem to do it. I myself prefer the sound of W.O.T. or idle.
Interesting about the FI engine not doing it... I am not complaining, though, I really do like the sound.
The V8 has it's own distinct sound because the firing pulses are not evenly spaced apart. Cylinders 1 and 5 alternate back & forth between banks evenly. then 4 and 2 fire on the same bank, then 6 & 3 alternate, then 7 & 8 fire on the opposite bank. That odd pattern is what gives a V8 the distinct sound....if you put a 180 deg header on it, it would turn that roar into a loud, rythmic even humming sound, more or less. That is, IF its a TRUE 180 deg header. Add to that that your ears can't hear the odd firing pulses every time they occur, but they only pick up those pulses at certain times, which is why you hear it at different speeds. Kind of like an optical illusion, but with your hearing. A while back I found a site that explained every imagineable cylinder angle, crankshaft offset, and about everything else you'd ever want to know about most of the commonly-produced engines....if I can find it again, I'll post it. It was a good read....as long as you have a few hours on your hands.
mavman...a good scientific explanation. It kinda goes with my original hypothesis, but much more expanded. I would like to see that site, if you find it.
The angle of the opposing cylinder bank, exhaust, cam, number of valves, firing order, number of pistons, Hpipe, Xpipe, single pipes, dual pipes, cylinder head composition, engine block composition, compression ratio, etc... All play into how an engine sounds! Good luck figuring it out! Dave Edit: A side note, slightly related... Larger exhaust pipe diameter slows exhaust pulses and deepens the sound of the exhaust. Smaller pipe keeps a fast exhaust pulse and raises the volume. Exhaust gasses expand with heat, and shrink as they cool. So, you can use progressively smaller pipe as you get away from the engine and still maintain a level of flow equal to the larger pipe close to the engine. If you retain large pipe all the way out, you lose velocity and gain 'drone'. If you use small pipe all the way out, you lose flow potential in the front of the exhaust.
