Yamaha to Get Pneumatic Valves

<div class='quotetop'>QUOTE (roger-m @ Jul 8 2007, 09:59 PM) <{POST_SNAPBACK}><div class='quotemain'>i think you will find most street bikes use the big bang config 180 crank as opposed to the 120 screamer, most screamer configs have a fireing order remap switch so the rider can adjust during the race.

As a matter of fact they don't. The cranc is 180 but as a 4-stroke piston only fire every second revolution the two pistons going paralell (usually 1-4 and 2-3) fire on oposite top. If piston one is on stroke 1, then piston 4 is on stroke 3. That makes the perfect screamer configuration with 180 deg between each fireing pulse.

<div class='quotetop'>QUOTE (Babelfish @ Jul 8 2007, 10:16 PM) <{POST_SNAPBACK}><div class='quotemain'>As a matter of fact they don't. The cranc is 180 but as a 4-stroke piston only fire every second revolution the two pistons going paralell (usually 1-4 and 2-3) fire on oposite top. If piston one is on stroke 1, then piston 4 is on stroke 3. That makes the perfect screamer configuration with 180 deg between each fireing pulse.
180 is big bang. A standard inline-four fires its cylinders at regular intervals - one cylinder every 180 degrees of crank rotation. This creates a constant delivery of power to the rear wheel,

United States Patent 7063059 for screamer cofig.
A multi-cylinder four-stroke internal combustion engine enabling a method for on-the-fly switching between two or more firing orders. Switching to the new firing order is done without requiring any tear-down of the engine such as to swap camshafts. Switching can be triggered by the rider, or it can be triggered automatically per conditions such as selected gear, RPM range, track location, velocity, and the like.
link

Honda unveiled a revolutionary idea with a 1992 V4 that was timed to fire all four cylinders within 65-70 degrees of crankshaft rotation - the so-called "Big-Bang" engine. Along with a balance shaft that neutralized the single crankshaft engine's gyroscopic effects, the 1992 NSR500 was a breakthrough. Emphasizing acceleration over sheer speed

i dunno fish. confuses the .... out of me

<div class='quotetop'>QUOTE (roger-m @ Jul 8 2007, 11:22 PM) <{POST_SNAPBACK}><div class='quotemain'>180 is big bang. A standard inline-four fires its cylinders at regular intervals - one cylinder every 180 degrees of crank rotation. This creates a constant delivery of power to the rear wheel,
It's only big bang if they fire two and two sylinders at the same time or allmost simultaniously.

With the fiering order you (and I) suggest it's a screamer.

<div class='quotetop'>QUOTE <div class='quotemain'>United States Patent 7063059 for screamer cofig.
A multi-cylinder four-stroke internal combustion engine enabling a method for on-the-fly switching between two or more firing orders. Switching to the new firing order is done without requiring any tear-down of the engine such as to swap camshafts. Switching can be triggered by the rider, or it can be triggered automatically per conditions such as selected gear, RPM range, track location, velocity, and the like.
link

What does that have to do with the this. You are confusing me.
<div class='quotetop'>QUOTE <div class='quotemain'>Honda unveiled a revolutionary idea with a 1992 V4 that was timed to fire all four cylinders within 65-70 degrees of crankshaft rotation - the so-called "Big-Bang" engine. Along with a balance shaft that neutralized the single crankshaft engine's gyroscopic effects, the 1992 NSR500 was a breakthrough. Emphasizing acceleration over sheer speed
No doubt that's a big bang but I'm 99% sure that a two and two fireing order is also called big bang as it differs a lot from the normal four fiering order (180).
<div class='quotetop'>QUOTE <div class='quotemain'>i dunno fish. confuses the .... out of me

Me too.

I am pretty sure Stoner and probably Loris has a switch to change maps so that they can fire down the straights when they need to and then chill out a bit when they dont need to so that they can conserve fuel. I think if the Duc ran at full capacity for the entire race, they would not make it.

Inline 4 cylinder road bikes are all using 180 "screamer" engines, where the firing order is completely symmetrical, this is the easiest on engine wear and doesn't require a balance shaft which saps power.

A big bang engine (as used by Kawasaki for example) has pairs of pistons firing either together or very close together, so each power pulse to the wheel is bigger but there is a rest time for the wheel to recover traction. Big bang engines can be set up symmetrically to effectively mimic a v-twin, or set up irregularly so that the two power pulses are closer together with a longer rest period between them.

Yamaha motogp engines are actually not big bang, but something called "long bang" where two cylinders fire close together, the remaining two cylinders are spaced out slightly more, then there is a long gap before the first pulse arrives again. The thinking behind this is that it makes the bike more ridable by reducing the fluctuations in crank speed that a big bang engine has, which means that the power going through the rear wheel is smoother than a big bang engine because essentially it eases the crank round more gently.

I hope that clears things up for everyone, i understand it but sometimes i am bad at explaining! Its also worth remembering that the angles you will have read about for the old 500 engines will be different because they were 2-strokes, that confused me for a bit.

<div class='quotetop'>QUOTE (Tom @ Jul 9 2007, 08:30 AM) <{POST_SNAPBACK}><div class='quotemain'>Inline 4 cylinder road bikes are all using 180 "screamer" engines, where the firing order is completely symmetrical, this is the easiest on engine wear and doesn't require a balance shaft which saps power.

A big bang engine (as used by Kawasaki for example) has pairs of pistons firing either together or very close together, so each power pulse to the wheel is bigger but there is a rest time for the wheel to recover traction. Big bang engines can be set up symmetrically to effectively mimic a v-twin, or set up irregularly so that the two power pulses are closer together with a longer rest period between them.

Yamaha motogp engines are actually not big bang, but something called "long bang" where two cylinders fire close together, the remaining two cylinders are spaced out slightly more, then there is a long gap before the first pulse arrives again. The thinking behind this is that it makes the bike more ridable by reducing the fluctuations in crank speed that a big bang engine has, which means that the power going through the rear wheel is smoother than a big bang engine because essentially it eases the crank round more gently.

I hope that clears things up for everyone, i understand it but sometimes i am bad at explaining! Its also worth remembering that the angles you will have read about for the old 500 engines will be different because they were 2-strokes, that confused me for a bit.
you wouldnt have 2 cylinders firing together, that would be like a twin,
i could be wrong but i was told many moons ago that big bang was 180 crank divides inrto 4 for the 720 otto cycle and screamer was 120 which divides int 6 for the 720 otto cycle. thus the 120 crank has more fires that are closer together than the 180 .

<div class='quotetop'>QUOTE (roger-m @ Jul 9 2007, 08:37 AM) <{POST_SNAPBACK}><div class='quotemain'>you wouldnt have 2 cylinders firing together, that would be like a twin,

Only if it fires symmetrically like a V-twin would usually, which i have never heard of anyone doing. If for example you had two pairs firing 180 appart followed by a 540 gap the engine would not behave like a V-twin.

<div class='quotetop'>QUOTE (roger-m @ Jul 9 2007, 08:37 AM) <{POST_SNAPBACK}><div class='quotemain'>i could be wrong but i was told many moons ago that big bang was 180 crank divides inrto 4 for the 720 otto cycle and screamer was 120 which divides int 6 for the 720 otto cycle. thus the 120 crank has more fires that are closer together than the 180 .

You have me a little confused here as to what you ar trying to say.

I think you might be quoting numbers that are associated with honda NSR 500 engines. Honda quickly ditched the true screamer (90 engine) in the 80's because it was unridable and had their cylinders firing in pairs, the screamer engine being a pair every 180. The big bang NSR had 2 pairs 120 appart leaving 540 of breathing space for the crank and rear tire. IS that what you meant?

<div class='quotetop'>QUOTE (Tom @ Jul 9 2007, 08:53 AM) <{POST_SNAPBACK}><div class='quotemain'>Only if it fires symmetrically like a V-twin would usually, which i have never heard of anyone doing. If for example you had two pairs firing 180 appart followed by a 540 gap the engine would not behave like a V-twin.
but that adds up to 900, it would have to come out to 720 to be a four stroke. and what would be the difference in say 2 250cc cylinders firing at the same time or 1 500cc cylinder, it would be like a twin without the torque. and there would be no point in having a 540 gap, thats a waste of power potential.

<div class='quotetop'>QUOTE (roger-m @ Jul 9 2007, 09:08 AM) <{POST_SNAPBACK}><div class='quotemain'>1. but that adds up to 900, it would have to come out to 720 to be a four stroke.

2. and what would be the difference in say 2 250cc cylinders firing at the same time or 1 500cc cylinder, it would be like a twin without the torque. and there would be no point in having a 540 gap, thats a waste of power potential.

1. How does it add up to 900??

2. The "pairs of cylinders" may not fire at exactly the same time, they can be slightly offset. Also smaller cylinders can get better combustion efficiency and have a smaller surface area so even when firing together are better than bigger cylinders. Think back to NSR 500 v-twins losing to the V4's even though they fired in pairs.

<div class='quotetop'>QUOTE (Tom @ Jul 9 2007, 09:19 AM) <{POST_SNAPBACK}><div class='quotemain'>1. How does it add up to 900??

2. The "pairs of cylinders" may not fire at exactly the same time, they can be slightly offset. Also smaller cylinders can get better combustion efficiency and have a smaller surface area so even when firing together are better than bigger cylinders. Think back to NSR 500 v-twins losing to the V4's even though they fired in pairs.
they dont fire in pairs, one is on the compression stroke and one is on the exhaust stroke

<div class='quotetop'>QUOTE (roger-m @ Jul 9 2007, 09:22 AM) <{POST_SNAPBACK}><div class='quotemain'>they dont fire in pairs, one is on the compression stroke and one is on the exhaust stroke

big bang engines fire cylinders in pairs or extremely close together. That is how the "big bang" is achieved.

<div class='quotetop'>QUOTE (Tom @ Jul 9 2007, 09:24 AM) <{POST_SNAPBACK}><div class='quotemain'>big bang engines fire cylinders in pairs or extremely close together. That is how the "big bang" is achieved.
they cant offset it tom or they would not be 180
you ask why i said your system woprked out at 900

<div class='quotetop'>QUOTE <div class='quotemain'>If for example you had two pairs firing 180 appart followed by a 540 gap the engine would not behave like a V-twin.

2x 180 = 360 + your 540 gap = 900

normal engine has 2 pairs of cylinders at 180
cylinder 1 induction stroke
cylinder 2 compression stroke
cylinder 3 power stroke
cylinder 4 exhaust stroke (cylinder 2 & 3 probably the other way around because of the firing order)
all 4 strokes happen over 720 like every 4 stroke engine, it's called the otto cycle. now im not sure if they call this bigbang or screamer but what i do no is it must be done over 720 and you would never have a 4 cylinder engine with 2 cylinders on a power stroke at the same time because it would be uneven cycle, v8s have 2 cylinders on a power stroke at the same time.
you said there would be a 540 gap, thats like 2 thirds of the cycle thats not producing anything but sapping power, i dont understand what your saying tom.

<div class='quotetop'>QUOTE (roger-m @ Jul 9 2007, 09:42 AM) <{POST_SNAPBACK}><div class='quotemain'>they cant offset it tom or they would not be 180

They can offset it, the complication of that is having to create a new crank shaft with irregular spacing.

<div class='quotetop'>QUOTE (Tom @ Jul 9 2007, 09:52 AM) <{POST_SNAPBACK}><div class='quotemain'>They can offset it, the complication of that is having to create a new crank shaft with irregular spacing.
then it wouldn't be 180 would it ?
for a cylinder to be at top dead center TDC not only does the piston have to be at the top but the connecting rod has to be exactly in the center of the bore, there is usually a few degrees either side when the piston is at the top, so there is no way of "off setting".
you still haven't explained this 540 gap you were going on about., im a little confused about this.

<div class='quotetop'>QUOTE (roger-m @ Jul 9 2007, 09:42 AM) <{POST_SNAPBACK}><div class='quotemain'>you ask why i said your system woprked out at 900
2x 180 = 360 + your 540 gap = 900

normal engine has 2 pairs of cylinders at 180
cylinder 1 induction stroke
cylinder 2 compression stroke
cylinder 3 power stroke
cylinder 4 exhaust stroke (cylinder 2 & 3 probably the other way around because of the firing order)
all 4 strokes happen over 720 like every 4 stroke engine, it's called the otto cycle. now im not sure if they call this bigbang or screamer but what i do no is it must be done over 720 and you would never have a 4 cylinder engine with 2 cylinders on a power stroke at the same time because it would be uneven cycle, v8s have 2 cylinders on a power stroke at the same time.
you said there would be a 540 gap, thats like 2 thirds of the cycle thats not producing anything but sapping power, i dont understand what your saying tom.

why 2 x 180?? remeber that when the second pair (yes they do it) of cylinders fire the first pair has completed 180 follow that with a 540 gap and you have 540 + 180 = 720 and back to the start. The gap sounds massive, but at the revs that a bike engine goes and the relationship between crank rotation and wheel rotation, it really does work out.

And yes your example is a standard 180 spaced engine (screamer)

<div class='quotetop'>QUOTE (roger-m @ Jul 9 2007, 09:55 AM) <{POST_SNAPBACK}><div class='quotemain'>then it wouldn't be 180 would it ?

exactly, your with it now?

<div class='quotetop'>QUOTE (Tom @ Jul 9 2007, 09:58 AM) <{POST_SNAPBACK}><div class='quotemain'>why 2 x 180??

QUOTE(Tom @ Jul 9 2007, 08:53 AM)

<div class='quotetop'>QUOTE <div class='quotemain'>Only if it fires symmetrically like a V-twin would usually, which i have never heard of anyone doing. If for example you had two pairs firing 180 appart followed by a 540 gap the engine would not behave like a V-twin.
you said 2 pairs firing at 180 apart = 360 + this 540 gap =900

<div class='quotetop'>QUOTE (roger-m @ Jul 9 2007, 10:04 AM) <{POST_SNAPBACK}><div class='quotemain'>QUOTE(Tom @ Jul 9 2007, 08:53 AM)
you said 2 pairs firing at 180 apart = 360 + this 540 gap =900

You misunderstand.

The first pair of cylinder start their power stroke and 180 later the second pair begin their power stroke. Now between the second pair of cylinders firing, and the first pair reaching the start of the cycle is the 540 gap.


Pair 1 fire (0 completed)
pair 1 begin exhaust stroke (pair 2 fire) (180 completed)
Pair 1 begin intake stroke (360 completed)
Pair 1 begin compression stroke (540 completed)
Pair 1 ready to fire (720 completed)

Do you see here that if pair 2 fire on 180 relevant to pair 1, that pair 1 have to make a further 540 before they are ready to fire?

<div class='quotetop'>QUOTE (Tom @ Jul 9 2007, 10:13 AM) <{POST_SNAPBACK}><div class='quotemain'>You misunderstand.

The first pair of cylinder start their power stroke and 180 later the second pair begin their power stroke. Now between the second pair of cylinders firing, and the first pair reaching the start of the cycle is the 540 gap.


Pair 1 fire (0 completed)
pair 1 begin exhaust stroke (pair 2 fire) (180 completed)
Pair 1 begin intake stroke (360 completed)
Pair 1 begin compression stroke (540 completed)
Pair 1 ready to fire (720 completed)

Do you see here that if pair 2 fire on 180 relevant to pair 1, that pair 1 have to make a further 540 before they are ready to fire?
ah i see what you mean. still sound daft to me to have 2 cylinders fire at the same time then a massive part of the cycle being non productive,

the only advantage i can think of over a big twin this big bang would have is valve surface area.
surly the engines woulds not last long with 2 explosions happening at the same time and there would also be a lot of strain on the cams and cam chain because of the amount of valve being opened at the same time.

<div class='quotetop'>QUOTE (roger-m @ Jul 9 2007, 10:22 AM) <{POST_SNAPBACK}><div class='quotemain'>ah i see what you mean. still sound daft to me to have 2 cylinders fire at the same time then a massive part of the cycle being non productive,

Having more power wouldn't be productive if it would make the wheel spin and the bike un-ridable.