Why do old bikes sound different from new bikes?

[KawiKid860]

I've been wondering this for a while, and can't seem to find anything on the internet about it (maybe I'm not wording my search correctly?). But for example, listen to the exhaust note of a CBR600 hurricane, a CBR600F3, an F4i, then an RR, they all sound different. Or compare an FZR600 to an R6, etc. The older ones tend to be more gruff and honestly to me sound closer to twins at idle, though they all have the same screaming I4 sound at higher rpms.

I understand technology has advanced quite a bit, but they're all still liquid cooled inline-4s. Is it the firing order? carbs vs efi? Enlighten me knowledgeable ninjetters!

[7oxSin]

Originally Posted by KawiKid860

I've been wondering this for a while, and can't seem to find anything on the internet about it (maybe I'm not wording my search correctly?). But for example, listen to the exhaust note of a CBR600 hurricane, a CBR600F3, an F4i, then an RR, they all sound different. Or compare an FZR600 to an R6, etc. The older ones tend to be more gruff and honestly to me sound closer to twins at idle, though they all have the same screaming I4 sound at higher rpms.

I understand technology has advanced quite a bit, but they're all still liquid cooled inline-4s. Is it the firing order? carbs vs efi? Enlighten me knowledgeable ninjetters!

if i had to throw a stick in the mud i would say muffler technology along with materials that they are made of now. you have to realize that the sounds any bike makes nowadays is 100% intentional. the companies have the tech and choose to let the bike sound like this, that and the other.

i know with harleys the rumble comes from the guy who invented em, he dindnt know what he was doing and ****ed up the timing but they still ran. thats how they get the deep put put bubble sounds, and also why they have to be serviced religiously.

[ninjamunky85]

I always wished the ninja 250 sounded more like this.

Link to original page on YouTube.
Of course that bike was a two stroke, so no modern street bike is gonna sound quite like that.

I think a lot of the difference in sound is due to things like fuel injection, and more strict noise restrictions. I remember when I first fired up the 300 at the dealership. It sounded weird, not really like any internal combustion engine that I had heard before. Luckily there are aftermarket exhausts to fix that. Not that I didn't like the sound of the 300, it's just that it sounded a lot different than my stock 250.

[Used Ninja]

That sound reminds me of a dirt bike, not a cruiser o.O

[ninjamunky85]

The kh wasn't a cruiser. The Kawasaki triples were the Ninjas of their day, predecessors to the modern sportbikes we know.

http://en.wikipedia.org/wiki/Kawasaki_triple

[Motofool]

Originally Posted by KawiKid860

............Or compare an FZR600 to an R6, etc. The older ones tend to be more gruff and honestly to me sound closer to twins at idle, though they all have the same screaming I4 sound at higher rpms.

I understand technology has advanced quite a bit, but they're all still liquid cooled inline-4s. Is it the firing order? carbs vs efi?.......

FZR600:
66.8 kW (89.6 hp) @ 10,500 RPM

YZF-R6:
88.2 kW (118.3 hp) @ 13,000 rpm

How do you obtain so much different performance from two engines physically almost identical?

Not by firing order or EFI certainly.

Remember that in engineering, everything is a compromise: you lose something to win something.

http://en.wikipedia.org/wiki/Inline-four_engine

http://www.epi-eng.com/piston_engine...and_torque.htm

Engineers can not play with much more than the timing of the valves and sparks.
By doing that, they modify the shape of the torque curves (or torque delivered for each rpm), achieving a more flat or peaky characteristic.
In other words, they strive for some torque for the full range of rpms' (flat engine) or higher torque for only a narrow range of rpms' and lower torque for the rest of the range (peaky engine).

The resulting sound is a sub-product of all the above plus some minor modifications to the intake and exhaust ducting and noise attenuation among different models.

[KawiKid860]

I never thought of the muffler tech, but putting if you put the same pipe on an 88 CBR and an 08 CBR they would still produce an entirely different sound.

So basically the the fact that older sport bikes tend to have a more user friendly midrange is part of what causes them to sound different?

Would compression ratio come into play as well? The FZR was 10.5:1 vs the R6s being 12-13:1 depending on the year, I'm sure the story is the same with other older bikes.

[Motofool]

Originally Posted by KawiKid860

.......So basically the the fact that older sport bikes tend to have a more user friendly midrange is part of what causes them to sound different?

Would compression ratio come into play as well? The FZR was 10.5:1 vs the R6s being 12-13:1 depending on the year, I'm sure the story is the same with other older bikes.

Yes, they "breath" at a different rhythm.
The sound is mainly the pulsing of these columns of air in and out.
The rest of the sound is from mechanisms, vibration and resonance of parts.

High compression ratio is always desirable for power and efficiency reasons, although is not always achievable without sacrificing something else.
It means nothing more than the force of the kick of the exploding gases over the piston; the pressure at the end of the downward stroke and at the point of exhaust valve's opening remains the same (no much (if any) effect on sound).

http://en.wikipedia.org/wiki/Compression_ratio

http://en.wikipedia.org/wiki/Otto_cycle

http://en.wikipedia.org/wiki/Thermal_efficiency

"A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency. This occurs because internal combustion engines are heat engines, and higher efficiency is created because higher compression ratios permit the same combustion temperature to be reached with less fuel, while giving a longer expansion cycle, creating more mechanical power output and lowering the exhaust temperature.

Thermal efficiency is the quotient of the net work to the heat addition into system. From analyzing the equation it is evident that the Otto cycle efficiency depends directly upon the compression ratio.

Ignition Process: The piston is momentarily at rest at TDC and heat is added to the working fluid at constant volume from an external heat source which is brought into contact with the cylinder head. The pressure rises and the ratio is called the "explosion ratio". At this instant the air/fuel mixture is compressed at the top of the compression stroke with the volume essentially held constant, also known as ignition phase.

Expansion Process: The increased high pressure exerts a greater amount of force on the piston and pushes it towards the BDC. Expansion of working fluid takes place isentropically and work is done by the system. The volume ratio is called "isentropic expansion ratio". Mechanically this is the adiabatic expansion of the hot gaseous mixture in the cylinder head, also known as expansion (power) stroke.

When expressed as a percentage, the thermal efficiency must be between 0% and 100%. Due to inefficiencies such as friction, heat loss, and other factors, thermal engines' efficiencies are typically much less than 100%. For example, a typical gasoline automobile engine operates at around 25% efficiency, and a large coal-fueled electrical generating plant peaks at about 46%. The largest diesel engine in the world peaks at 51.7%. In a combined cycle plant, thermal efficiencies are approaching 60%. Such a real-world value may be used as a figure of merit for the device."

[KawiKid860]

Ahhh "breathing at a different rhythm" makes sense to me.

Man you are smart!

Okay so my next question is a bike such as an FZ6R, or GSX650F, they have much more friendly mid ranges but still have that smooth modern 600 sound. I'm guessing those power curves combined with a similar sound would be achieved with compression ratio, the degree of the cams (or however you refer to that) and other little changes in the tuning, since they're a good 30-40 horsepower down from a supersport but produce the same type of exhaust note.

[Motofool]

Nah, ....just read a lot

Yes, probably so.

[CC Cowboy]

Hernan of Florida, splain crossplane please. I know Cadillac started it and Yami uses now. I thought it was crank and firing order.