Big Bang vs Screamer?

[05 Busa LE]

Can anyone explain (in layman's terms) the difference between a "big-bang" firing order and a "screamer" firing order? I'm reading that Rossi and Hayden have tested both at Valencia, and I'm wondering what exactly is the difference, and how it would affect putting power to the ground.

 

[ogre]

the big bang is the firing order the kawi's are using, isn't it? where all 4 pistons fire within 180 degrees of crank rotation? someone in the know please chime in, i don't want to be giving wrong info.

 

[aussiekeeper]

the big bang is the firing order the kawi's are using, isn't it? where all 4 pistons fire within 180 degrees of crank rotation? someone in the know please chime in, i don't want to be giving wrong info.

Yes, but all plugs fire every 180...........

 

[Commuta_Busa]

The difference is in the crank. The rod throws are spaced differently. What this means is that the power strokes are uneven during a complete crank rotation. So you get a big shove of power and then a longer break in time/rotation before the next power stroke. This is being doing to try and control traction a little more. It gives the tire a little more time to recover between power strokes.

 

[jellyrug]

This explains the big bang motor.

- 2009 Yamaha YZF-R1 engine technology explanation[/url]

Not sure I support the technology, IMHO the back wheel will see more vibration due to uneven ignition pulses, putting more strain on wearing out the rear tire. At 11,000 RPM inertial torque is neglegible.

 

[djsin]

we are 2 up 2 down inside as well

 

[Dehning]

we are 2 up 2 down inside as well

That's the point if you watch the video explanation, you'll see that in big bang it's not 2 up 2 down, the center piston's crank is offset 90 degrees.

 

[mysql]

In the simplest terms, I'd describe a big bang as something similar to a v-twin in the power delivery, while a screamer is what you'd expect from a typical I4.

 

[05 Busa LE]

Thanks for all the input. It's interesting that they're testing both, but I guess they need to find what best suits both riders. Was Rossi's Yamaha a screamer or big bang?

I watched the video, and I'm assuming that the big bang configuration is the original configuration, where the crank configuration creates an inertial push, and Yamaha's cross-plane is the screamer configuration, where the crank configuration offsets the inertial push and creates more of a smooth delivery of power?

 

[jellyrug]

Thanks for all the input. It's interesting that they're testing both, but I guess they need to find what best suits both riders. Was Rossi's Yamaha a screamer or big bang?

I watched the video, and I'm assuming that the big bang configuration is the original configuration, where the crank configuration creates an inertial push, and Yamaha's cross-plane is the screamer configuration, where the crank configuration offsets the inertial push and creates more of a smooth delivery of power?

It's the other way around.

 

[05 Busa LE]

Got it--thanks. Saw this on Wikipedia, which helped to clarify it for me:

A big bang engine is an unconventional motorcycle engine designed so that most of the power strokes occur simultaneously or in close succession. This is achieved by changing the ignition timing; sometimes in combination with a change in crankpin angle. The goal is to change the power delivery characteristics of the engine or exhaust sound. A regular firing multi-cylinder engine fires at approximately even intervals, giving a smooth-running engine. Because of a big bang engine's power delivery imbalance, there exists more vibration and stress in the engine. This imbalance can overwhelm the rear tire, and generally makes a slide harder to catch. Until recently, this has limited their use to racing.