Motorcycle engines make a harsher, higher pitched sound than a same displacement, same cylinder number car engine. Why is that? Is it because of the bigger body of the car, or is there some difference in the design of motorcycle engines?
Car = exhaust usually passes through exhaust manifold verus header pipe, has a longer run of exhaust tubing and passes through a catlytic converter, substantial muffler (sometimes two mufflers) and a tail pipe which might be designed to further reduced resonance.
Note the small cars that sound like whiney cycles…usually have header pipes…might have bored out cat convertor…wider pipes and open muffler/tail pipe design.
Damn, forgot to include that many cycles are V-twins, getting displacement from just TWO cylinders…and that creates a sound that is distinctly different than a four cylinder (and six, eight, etc), as explosions and evacuation of exhaust gases happen with a different rhthym/tone.
Also, all car engines have water jackets, and the engine issurrounded by the car’s body, both of which muffle the sounds of internal combustion.
I’m not very familiar with cars, but I do belive that they typically rev a lot lower than a typical bike, which will result in a more high pitched sound from the bike.
I know my old 4 cylinder 400cc bike has a redline around 10.000 rpm (and that isn’t even that much compared to modern bikes), I belive that would be quite a lot for a car.
This comes down to the major differances between bike and car engines.
Bike engines are very much lighter in construction so any sound produced is not dampened down as much.
Bike engines are often water cooled and have water jackets, but the air cooled ones will certainly make more noise.
Bike engines are virtually always much higher revving than cars, this means much more noise from the top end, such as the cams, valves, camchains, indeed plenty of cars still use push rods rather than overhead cams.
The result is that on bikes, all these components wear very much more rapidly than on a car, bikes are very rarely good for more than 150k miles without very heavy duty work on the top end gear.
Bike engines tend to have much higher compression ratios, the more you squash the mixture before igniting it, the bigger the bang and the more power, bike engines tend to have higher power to weight ratios than car engines.This also has the effect of making the bike engine run hot, so cooling systems have to be designed to cope with this, and the pumps add to the noise.
One major source of noise on bike engines is the way drive from the crankshaft is delivered to the gearbox. Space on bikes is at a premium around the engine as a bulky engine will either be wide and have poor ground clearance when leaning over, or it will be long and this makes the wheelbase greater and make the bike handle more slowly, reducing agility.
The way the total engine length is reduced is by incorporating the gearbox into the engine casings, using the same oil. The oil in a car gearbox is usually far heavier than egine oil, bikes use engine oil in the gerabox which does not damp sound as well so you get plenty of gear whine.
Power on a bike is delivered from the crankshaft via a primary chain to the clutch basket, this is also much more noisy than a car which generally uses a shaft drive from crank to gearbox.
Car engines are mostly designed to produce lots of torque and at much lower engine speed than bikes and so exhaust design is very differant.
In fact some bikes have a way of effectively increasing the length of the exhaust tract to increase torque at lower engine speeds.
Bikes usually have shorter exhaust tracts and these are tuend to allow the spent gases to escape more easily which helps the engine rev up more quickly and rev higher, producing more power, the way a bike exhaust works is quite a feat, as pressure waves oscillate backwards and forwards within the system and these are used to literally such the engine gases out and draw the next fuel air mixture in.
The result is that a bike exhaust has more noise than a car- usually.