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Discussion Starter · #1 ·
Here is a wonderful article I would like to share. It was sent to me and written by the SAE.
http://www.sae.org/mags/AEI/5586
I hope this can be another one of those high level discussions that seem to be occurring here recently.

Uneven firing plays winning tune for Yamaha
31-Dec-2008 15:29 GMT

Valentino Rossi astride the Yamaha YZR-M1 MotoGP racing machine. The YZR-MI won three ­MotoGPs in a row in April, May, and June.
“I might have gone absent without leave today had we lost Le Mans,” said Masao Furusawa, Executive Officer of Yamaha Motor Co. and Senior General Manager of Engineering Operations, Motorcycle Headquarters, when telling the secret of Yamaha’s winning formula in the MotoGP racing series. In April and May, Yamaha won three races in a row, the Grand Prix of China, Portugal, and France. The French Grand Prix at Le Mans saw Yamaha YZR-M1s finish in first, second, and third positions, justifying Furusawa’s technical discussion.
Furusawa’s success with Yamaha is in part due to his long service to the company. Furusawa was born in February 1951 on the western island of Kyushu, Japan. He graduated from the mechanical engineering department of the Kyushu Institute of Technology in 1973 and joined Yamaha the same year.
Furusawa climbed up in Yamaha’s engineering echelon; he was appointed General Manager of the off-highway vehicle Engineering Department Division, working with all-terrain vehicle snowmobiles, in 1998; General Manager of the Engineering Department, Global Engineering and Manufacturing, Motorcycle Operations in 2001; and Senior General Manager of Engineering Operations, Motorcycle Headquarters in 2005, before coming to his current management position.
MotoGP is the pinnacle of the world motorcycle road racing series, a Formula One on two wheels, fiercely contested by the leading OEM marques including Honda, Yamaha, Suzuki, and Kawasaki of Japan and the 2007 World Champion, Ducati, of Italy.
MotoGP’s governing regulations stipulate that engines must be four-stroke, have reciprocating pistons (no rotary or oval pistons), and be naturally aspirated of less than 800-cm3 displacement, reduced from the previous 990 cm3 in 2007 to curtail race speeds, as with the case of Formula One. Maximum fuel tank capacity has also been decreased from 22 to 21 L (5.8 to 5.6 gal). Minimum weight of the MotoGP motorcycle with four cylinders is 148 kg (326 lb), whereupon 7.5 kg (16.5 lb) must be added for each additional cylinder. Furusawa cited that a typical MotoGP machine should be capable of exceeding 320 km/h (199 mph) in a straight line, with its engine producing over 200 hp (149 kW).
As an engineer, theoretician, and avid racing enthusiast, Furusawa analyzed Yamaha’s race-winning YZR-M1 transverse inline four-cylinder engine and employed a 90° crankshaft and adopted irregular—or odd—interval firing.
“Uneven- or irregular-interval firing has been employed in racing engines—the so-called ‘Big Bang,’ with more than one cylinder firing simultaneously,” Furusawa explained. “Then there is the ‘Long Bang,’ with crank phases out of sync. Uneven-interval firing race engines have been known to improve lap times versus even-interval firing ones. How and why they work has not been clearly defined,” he said.
“Some maintain that closely spaced, multicylinder combustion pulses press the driving tire’s contact patch against the road surface harder, to a degree that the tire slips or spins, then enables the tire’s ‘recovery’ during the following non-combustion interval, so that pent up energy generates a stronger grip on the next power pulse—a rather dubious supposition that I do not subscribe to at all,” he continued.
Furusawa observed that, by simultaneous two-cylinder combustions, peak torque would double, producing a momentary burst of power, but conversely the total number of combustions decreases, thus obtaining the same total.
His ideal would have been a multicylinder, even-interval-firing engine with minimum fluctuations in revolutions, thereby getting the maximum amount of propulsion without inducing tire slippage. Ultimately, he added, something like an electric motor.
He said that uneven-interval firing itself was not the primary purpose of his design and development team, but that the 90° crankshaft was a fruit of strenuous work in minimizing fluctuations in engine revolutions. The natural result was that combustion intervals had become uneven because of the crankshaft design.
Furusawa’s team then pushed the uneven-interval-firing envelope to an extreme in one variation of the M1 engine that had all combustion occurring in a single revolution, the “Ultimate Long Bang,” Furusawa described. The exercise produced a change in the bike’s total traction, but no improvement in lap times.
Yamaha put the 90° crank YZR-M1 through its paces at the Mugello circuit, the MotoGP Italian Grand Prix track. The post-2007 machine shed 20% of its displacement in the regulation change, lost about 10 km/h (6 m­ph) in top speed—now about 330 km/h (205 mph)—­yet its cornering speeds improved by 2 to 8 km/h (1 to 5 mph), thus producing better lap times.
The throttle-opening ratio spread of the MotoGP machine is opposite to that of a Formula One car, noted Furusawa. A Honda F1 engineer confirmed that at the fast Monza circuit, the F1 Italian GP track, full throttle would account for massive 74% of all running, whereas a MotoGP rider at Mugello, another fast track, would crack the throttle wide open for only 25% of the race. More notable, Furusawa elaborated, is that less than 10% open throttle accounts for roughly 30% of the race.
“Whichever the engine configuration may be, inline or V-formation, targeted weight distribution should be no different, about 50/50. It could be a fraction of that at either end, but I am not going into that,” Furusawa said. “I believe the inline engine is more advantageous when fitted within a shorter wheelbase, which is more agile. In the V-configured engine, the rear bank tends to shift the mass rearward, which must be offset by lengthening the wheelbase.”
Engine power is obviously important; more so is its good traction and driveability on partial throttle. Ubiquitous inline four-cylinder engines in road cars and motorcycles employ 180° crankshafts and even-interval firing. Such engines are relatively simple in design and construction (by racing standards) with reciprocating first-order inertia forces balanced internally, while even-interval firing reduces vibration in the low- and mid-speed zones. However, the design is entirely unsuitable for MotoGP, where inertia forces and inertia torque would become huge in the usable revolution range of 15,000 rpm.
“What the rider wants is combustion torque proportionate to the throttle work, not inertia torque,” said Furusawa, who drew an analogy to signal-to-noise ratio (SNR), an electrical engineering term. “Combustion torque is a signal, and inertia torque is noise. Unfortunately, noise increases proportionately to the square of revolutions, greatly deteriorating the SNR.”
A typical road vehicle inline four may go up to about 7000 rpm on the high end, which is well within the engine’s effective combustion torque zone. In the MotoGP application, winding to 15,000 rpm, inertial torque would be significant. The rider must make best use of the signal buried deep within a large noise, and that would do no good to the essential connectivity between the throttle and rear tire.
Furusawa used the basics to illustrate his point; a single-cylinder engine does not turn as smoothly as might be imagined. It runs faster at top dead center (TDC) and bottom dead center (BDC), because the piston and crank pin are perfectly aligned, thus the crank exerts no effect. With the crank at 90 and 270°, the crank pulls, fluctuating revolution.
His theoretical SNR graph shows a 180° engine model at wide-open 15,000 rpm, assuming no fluctuations in rpm, in which noise/inertia torque is greater than signal/combustion torque. The compounded torque value that drives the motorcycle is, therefore, reduced. In the 90° crank engine, noise/inertia torque is almost negligible; what little is there is generated by the leaning connecting rods. Net driving torque nearly matches the value of combustion torque and is efficiently transmitted to the rear tire at the rider’s command.
Verification of the Yamaha SNR theory was performed by directly measuring fluctuations in rear tire revolutions during cornering using frequency analysis. In the 180° crank YZR-M1, speed fluctuations by second order in revolutions occurred regardless of throttle opening. The 90° crank version, on the other hand, displayed speed fluctuations of the second order in only 1.5 revolutions when the throttle was opened. Furusawa concluded that the 90° crank engine transmitted the signal/combustion torque singularly and effectively to the driving wheel.
Furusawa recounted racer Valentino Rossi’s first reaction to the YZR-M1 in January 2004. Rossi was the World MotoGP champion in 2002 and 2003, riding for Honda. The young Italian had just switched camps to Yamaha, widely rumored to prove that it was not the song but the singer.
Furusawa put Rossi on both the 180° and 90° crank YZR-M1. On the 180° machine, he commented that it was as power-oriented as his previous Honda mounts. On the 90° crank version, he responded, “Very sweet!” The bike responded precisely to his throttle command, producing optimal rear-wheel traction during cornering, and demanded less physical strain on a long run.
He observed that it somehow felt a little short of acceleration but, in fact, had better lap times. His riding style on the successive Hondas had been very aggressive, often wildly sliding the rear tires. His instinct told him that the old technique would not make the Yamaha go faster, but that he should adjust to a smoother style.
Rossi won the MotoGP World Championship astride the Yamaha YZR-M1 in 2004 and 2005. The 2008 season was still young, with only eight races run out of 18, when Furusawa revealed his unique SNR theory and the smallest hint of the YZR-M1 technology.
Furusawa imparted his wisdom, “Yes, the rider may adapt himself to a specific machine. On the other hand, we will respond to his demand if he wants more power. It works two ways. Winning is not by a single force, but the total efforts of the rider, machine, organization, motivation, and human and material resources. I want them all.”
Jack Yamaguchi
 

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Re: (Shomegrown)

Quote, originally posted by Shomegrown »
How is the sound different between the even and odd firing engines? I'd be curious to hear it!

Do a search for sound clips of the new 2009 R1, uses an uneven firing pattern like the M1.
http://www.yamaha-motor.com/sp....aspx
 

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Re: (Shomegrown)

Quote, originally posted by Shomegrown »
How is the sound different between the even and odd firing engines? I'd be curious to hear it!

Sounds like a V-engine. If you have ever heard a Honda VFR series bike, they sound much like this. Ducati has experimented with big bang on their V-4 desmosedicic as well.
One of the initial ideas behind this was a sort of natural traction control. The gentleman in the article above seems to discount this though. The longer duration between power cycles allowed a spinning tire to recover more easily. With the current state of electronics and traction control systems in MotoGP, this has largely become a moot point.
I guess the new Yamaha R1 sounds really awesome according to initial tests. I am excited to hear one myself.
 

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Re: (tgodbout)

It, the 2009 R1, does sound really cool. Almost the the M1, but it obvioulsy doesn't spin as fast. Curiously enough, the Ducati prototype sounds more like what you would expect a I4 to sound like. And the Yamaha sounds what you would expect a V4 to sound like.


Modified by TurboWraith at 12:43 PM 1-7-2009
 

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Re: (tgodbout)

Quote, originally posted by tgodbout »

Sounds like a V-engine. If you have ever heard a Honda VFR series bike, they sound much like this. Ducati has experimented with big bang on their V-4 desmosedicic as well.
One of the initial ideas behind this was a sort of natural traction control. The gentleman in the article above seems to discount this though. The longer duration between power cycles allowed a spinning tire to recover more easily. With the current state of electronics and traction control systems in MotoGP, this has largely become a moot point.
I guess the new Yamaha R1 sounds really awesome according to initial tests. I am excited to hear one myself.

Yep, the Ducati figured out their TC late in the 990 series bike and they have been screamer engines ever since.
Wonder what the old Aprilia Cube would have done with modern TC?
 

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Re: (BTM)

Quote, originally posted by BTM »
cliffnotes?

This might not be correct, but I'll try:
In a "normal" engine, rotation is fastest at top dead center and bottom dead center because the piston and crank pin are perfectly aligned. In an uneven firing engine, at the top and bottom of the piston's travel, the crank pin is at either 90 or 270 degrees.
My assumption is that the inertia of the piston being at the bottom of its travel corresponding with the perfect alignment of the crank pin and con rod creates an uneven rate of rotation whereby rotation slows in the middle of the pulse (the middle of the piston's travel). This would mean that the most inertia occurs at TDC and BDC. So what I was able to gather is that at BDC and TDC on an odd firing engine, this inertia is offset by the con rod and crank pin not correspondingly being at the top or bottom of their rotation. Likewise, when the con rod and crank pin are at the top and bottom of their travel, the piston is in the middle of its travel, offsetting the more extreme rise and fall of forces acting against the movement of the piston in an even firing engine.
So for the sake of BTM's request for cliff's notes and my own desire to understand, is this correct?
 

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Close ...
Considering inertial rotation only (not friction and power strokes etc), the total amount of kinetic energy in the crankshaft and pistons and connecting rods is constant at a given rotation speed.
With a normal crankshaft layout on an inline-four, at TDC/BDC, all of this energy is in the rotation of the crankshaft and, to a lesser extent, the connecting rods (which are rotating around the wrist-pin at that instant). At halfway between TDC and BDC, the kinetic energy is spread between the rotation energy in the crankshaft and the translation energy of the pistons and rods. Therefore, the rotation speed is highest at TDC/BDC and at a minimum 90 degrees before or after TDC/BDC.
With the irregular-firing crankpin, the kinetic energy transfers are split up because at the moment when one pair of pistons is at TDC/BDC the other pair is halfway between, and vice versa, so the rotation speed of the crankshaft through the whole rotation is much more steady.
The traditional 90-degree V4 layout with a 180 degree crankshaft also has this advantage and it has exactly the same firing pattern (90 - 180 - 270 - 180) as the new Yamaha in-line engine.
 

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Discussion Starter · #15 ·
Re: (HerrGolf)

That is not really what the article is about. There is no mathematical power advantage to ANY firing order. It is still 4 pistons firing in two crankshaft revolutions.
There is a Balance advantage of some firing orders. You can use the throws of one piston to counteract the other piston. This creates couples, but less translitory forces.
What this article is about is getting on the throttle earlier. The way this is accomplished is by FEEL. The multiple cylinder firings in a short amount of time create a large amount of Jerk, the derivative of acceleration. The highly skilled rider can now detect the onset of throttle better because there is more tactile feedback. Because the power pulse is 2-4x larger and occurs at 1/2-1/4 the frequency of a normal bike. This allows the RIDER to apply that power sooner and more precisely than with a conventional firing order.
The rider can now use that power because he can feel it. Previously the amount of torque available from crankshaft inertia alone was significant when compared to the individual power pulses. In other words you couldn't feel the 4 tiny pulses before at high RPM, but now, even thought he inertia of the crank is still there, because the 4 combustion events are so closely spaced, you can feel them and modulate the throttle better.
This is hy he consciously makes the analogy of signal to noise ratio. There is no power advantage at all, just more feedback from the bike, which the rider can use to push the limit even more.
 

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If anything, the odd firing order makes for a slight power *dis*advantage. The 90-degree crank on an in-line engine requires a counter-rotating balance shaft - the R1 engine has a pair of them, one on each end, and this adds a little friction. It also complicates intake and exhaust tuning because it's not symmetrical any more. The 2009 R1 engine supposedly has an ECU with individual mapping of all four cylinders ...
 

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Discussion Starter · #18 ·
Re: (GoFaster)

Quote, originally posted by GoFaster »
If anything, the odd firing order makes for a slight power *dis*advantage. The 90-degree crank on an in-line engine requires a counter-rotating balance shaft - the R1 engine has a pair of them, one on each end, and this adds a little friction. It also complicates intake and exhaust tuning because it's not symmetrical any more. The 2009 R1 engine supposedly has an ECU with individual mapping of all four cylinders ...

Well you could say just about anything. It's a pretty obtuse but interesting article.
Id bet you dollars to donuts though that mathematically the change in crankshaft polar moment of inertia (j) caused by counterbalancing the long bang, or other odd firing sequences is a significantly greater power loss than the balance shaft.
And frankly balance shafts don't balance ANYTHING. They cancel vibrations from entering the car or bike and are there for the purposes of NVH and NVH only. I doubt ANY race bike has balance shafts, unless its a rule.
 

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Quite true about the moment of inertia, that's yet another factor.
The Yamaha M1 does indeed use a balance shaft. Uneven primary balance at 16,000 rpm does a good job of shaking things apart. I have the MotoGP Technology book that 'splains a lot of this (but at that time, the theory about the "signal to noise" ratio was not around yet - or at least, not made public). The 990cc version of the Yamaha M1 has the crankshaft rotating backwards and the layshaft necessary to get the engine rotating the other way is also the balance shaft. In that case, using the same shaft for both purposes negated the extra drag (but not the extra inertia). The production engine doesn't do it that way.
If you really want to get freaked out ... try to figure out how Honda got their V5 (3 cyl in front bank, 2 cyl in rear bank) to be balanced without a balance shaft. That one, I still cannot figure out. That engine inherently had an irregular firing order. Interestingly, when Honda knocked off the odd cylinder to bring in the 800cc era, the bike that followed didn't have nearly the same race results that the 5-cylinder had.
 

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Re: (GoFaster)

I have one simple question....
Does the crank-shaft of this style look like a traditional V8's? Or is it two pistons at 0deg and two at 90deg?
Don't know why, but the description somehow made me think that it would look something like the latter

Never mind... Found it by searching somewhere else. It's a crank with each rod connection separated by 90deg, like a V8's. Just in case anyone else for some odd reason didn't understand what the article was talking about.
I guess since it was supposed to be some new-age design it was going to be radically different than anything ever before.
Now to find a machinist who will build me a forged crank in this style for my Corrado



Modified by thetwodubheads at 9:11 PM 1-9-2009
 
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