4 Cyl Cross Plane vs Flat Plane Crankshaft

[Professor Gas Can]

Please click on the link below, skip the intro, and wait for the bike to load. Click on the bottom most square and watch the video.

Link (http://www.yamaha-motor.com/sport/msite/micro_v1.aspx)

There you will see their "explanation"� of why the cross plane crankshaft is better than the flat plane. I'm not so sure I agree with them and would like your guy's opinions on whether these guys are full of crap or not.
Basically what they do is they take the standard 1-2-4-3 firing order, flat plane crankshaft and move both cylinders 2 and 3 by 90 degrees and 4 by 180. This yields a firing interval of 270-180-90-180 if I'm not mistaken. It's essentially one bank of a V8. Their claim is that by moving cylinders 2 and 3 out of the plane, the inertial torque is split evenly throughout the cycle, yielding a smoother variation in crankshaft speed. Whether this provides any benefit is debatable.
I ran their firing order and phasing through my crankshaft program and got the same mean torque throughout the cycle. This makes sense (same amount of fuel and air combusted over the same period of time). Okay, so same mean power is produced over the same cycle. What is different is the peaks and valleys are smaller (blue line) as opposed to the normal flat plane (pink line).

http://img.photobucket.com/albums/v253/ianamay/untitled.jpg?t=1223000654

If we hypothetically setup a situation where all the cylinders got the same amount of air fuel and spark, and put them in identical situations, only differing the firing order of the cranks, would there be any benefit in performance? A good analogy would be paddling a canoe two times really fast and coasting for a while or paddle once, wait, then paddle once again. Or for UB's sake, does a 90 degree V-twin make more power than a 45 Degree V-twin just because of the firing order and crankshaft? It shouldn't.

So yea, the cross plane crank's angular acceleration varies less over a cycle, but does that really equate to better performance? I would imagine it would be worse if anything due to the uneven nature of the intake and exhaust systems due to the uneven firing order.
One benefit would be that the cross plane crankshaft wouldn't need a balance shaft as its second order rotation is not a problem, unlike a flat plane. I can't imagine variation in torque would be that much where it would affect traction (like they said it would) because not only is there a flywheel, it is a low inertia high rev race engine. Would bearing friction or loading make any difference with the cross plane vs flat plane?

I thought this would be interesting to all you 4 cylinder junkies, so now you'll be better prepared for when Steve Fox asks you why you chose to use a flat plane crank instead of a cross plane crank.

-Ian
Ex-UB Engine Guy

[VFR750R]

it's a bunch of marketing b-s. They do it to M1's because of the vibration from a flat-plane crank at 18,000rpm. The uneven firing order does hurt power production, from exhaust tuning, but motogp bikes make excessive power and have more issue controlling it, and a 90deg crank will have a broader power curve from the exhaust not tuning up strong at specific rpm. Even most streetbikes don't pair the correct cylinders together on exhaust systems. Since R1's aren't taking advantage of their current even firing order, they don't stand to lose much with the new uneven one.

This type of crank is often confused with a big-bang style of engine used by honda(and maybe others) in the 2-stroke days. Those engines fired all 4 cylinders within 132deg of one crank rotation. It produced a distinct overlapping power pulse followed by a distinct void of cylinder pressure which allowed the tire to regain grip. Interestingly, they abandoned it when spark and fuel controls improved to the point they could provide the control instead.
I once heard the limit of crankshaft underbalance on F1 engines was limited by the eyesight of the driver and strength of the rear wing mounts.

The reason they do it to R1's is because they do it to m1's.

[murpia]

Originally posted by VFR750R:
Those engines fired all 4 cylinders within 132deg of one crank rotation. It produced a distinct overlapping power pulse followed by a distinct void of cylinder pressure which allowed the tire to regain grip.
I've heard this theory before and always wondered why it was supposed to work.

I can think of a few reasons why it might, and others why it wouldn't...

Anyone know if there's any valid data anywhere one way or the other?

Regards, Ian

[samphlett]

Pure marketing poop.

Did anyone here believe Honda when they promoted that oval pistoned bike as some kind of technology breakthrough?

[Chris_S]

Originally posted by murpia:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VFR750R:
Those engines fired all 4 cylinders within 132deg of one crank rotation. It produced a distinct overlapping power pulse followed by a distinct void of cylinder pressure which allowed the tire to regain grip.
I've heard this theory before and always wondered why it was supposed to work.

I can think of a few reasons why it might, and others why it wouldn't...

Anyone know if there's any valid data anywhere one way or the other?

Regards, Ian </div></BLOCKQUOTE>

A topic from earlier on in the year: http://fsae.com/eve/forums/a/tpc/f/125607348/m/94810786121/p/3

[stickboy]

It is not just marketing B.S. It is true that they only experiment with firing order for bikes in MotoGP because they are the only bikes that make enough power where it is necessary. It all has to do with the tires. In a regular firing order, most of the power pulses occur one after another pretty consistently. Because of the power of these machines, the tire cannot keep traction and wants to slide. Imagine pushing a person repeatedly over and over, never giving them a chance to regain their footing.
Due to the firing order of a "long/big bang" engine, the power pulses are clumped closer together and there is a period of crank rotation where absolutely nothing is going on. This offers the tire enough time to settle and gain traction before the next pulse. However, this is unnecessary for any bike unless your putting out 230 hp, and fsae cars don't deal with just one tire and a contact patch the size of your palm.

[stickboy]

sorry to repeat what VFR750R already said in my earlier post, but big bang engines have been used as recently as 2006, not just in the old two-strokes. Also, there is no real power gains or losses, its just a way to optimize vibration issues, driveability, and over all better equilibrium between various systems on the vehicle.

[murpia]

Originally posted by stickboy:
It is not just marketing B.S. It is true that they only experiment with firing order for bikes in MotoGP because they are the only bikes that make enough power where it is necessary. It all has to do with the tires. In a regular firing order, most of the power pulses occur one after another pretty consistently. Because of the power of these machines, the tire cannot keep traction and wants to slide. Imagine pushing a person repeatedly over and over, never giving them a chance to regain their footing.
Due to the firing order of a "long/big bang" engine, the power pulses are clumped closer together and there is a period of crank rotation where absolutely nothing is going on. This offers the tire enough time to settle and gain traction before the next pulse. However, this is unnecessary for any bike unless your putting out 230 hp, and fsae cars don't deal with just one tire and a contact patch the size of your palm.
At 10,000rpm the engine torque pulses are in the 300Hz range. I cannot conceive how a chain driven transmission plus all the other inertias in between can transmit torque at that frequency to a tyre. Can someone explain?

Regards, Ian

[Superfast Matt McCoy]

Originally posted by Professor Gas Can:
so now you'll be better prepared for when Steve Fox asks you why you chose to use a flat plane crank instead of a cross plane crank.

"It's marketing BS Steve, stop asking stupid questions."

?

[VFR750R]

Originally posted by murpia:

At 10,000rpm the engine torque pulses are in the 300Hz range. I cannot conceive how a chain driven transmission plus all the other inertias in between can transmit torque at that frequency to a tyre. Can someone explain?

Regards, Ian

for it to work like a big bang, it would actually have to be a big bang. ie all pulses very close together.

I also find it funny that although it is a inline 4 now it has the same firing order as a V4. Now my vfr sounds pretty sweet, but honda never marketed vfr's (or rC45's) as having special throttle control superiority due to its unconventional firing order.

[VFR750R]

These are some big bang engines

http://www.youtube.com/watch?v=_7lwXtVro6c

http://www.youtube.com/watch?v=jxzTtkv-mHI

the john deere actually has an uneven firing order. it's a parallel twin with 180 deg crank. That one is close to the 'factory' 416 cubic inch and factory 35hp, but i've seen G's at antique pulls without rules have 630 cubic inch from 2 cylinders and more like 135hp. That's a 10" stroke. at the end of the video you can just see the individual power pulses rotating the tires before he pulls the clutch. 'Built' G's throw dirt on each power stroke and it's way cool to watch. Too bad most old guys building these things don't put their stuff on youtubehttp://fsae.com/groupee_common/emoticons/icon_wink.gif

[Charlie]

Originally posted by samphlett:
Did anyone here believe Honda when they promoted that oval pistoned bike as some kind of technology breakthrough?

When did Honda do that?

As far as I know that was a way to get around the rules... it was never promoted as an optimum way to make power.

[VFR750R]

Honda sure did, but it was 12 years later when they tried to sell the technology as exotic in the NR750. They justified it to the public by charging 4 times more then a just as fast RC30.

[exFSAE]

Originally posted by stickboy:
Due to the firing order of a "long/big bang" engine, the power pulses are clumped closer together and there is a period of crank rotation where absolutely nothing is going on. This offers the tire enough time to settle and gain traction before the next pulse.

I highly doubt this.

[PSUAlum06]

Originally posted by exFSAE:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stickboy:
Due to the firing order of a "long/big bang" engine, the power pulses are clumped closer together and there is a period of crank rotation where absolutely nothing is going on. This offers the tire enough time to settle and gain traction before the next pulse.

I highly doubt this. </div></BLOCKQUOTE>

If anything, I think sustained torque would be better for the tire

[VFR750R]

http://www.superbikeplanet.com/NSR500.htm

I lied, all 4 cylinders fired within 70 deg window.

but again, the r1 is no more big bang then a honda vfr, and to my knowledge no true big bang engines have been produced since the 2-stroke days. I'm sure it depends on your definition of big bang, but my pre-requisites would include more then half the potential time for cylinder pressure being free from it. Basically all cylinders firing within 360deg in a 4 stroke or 180 deg in a 2-stroke. This means all single cylinder engines are big bang, and parallel twins with 180deg cranks would also qualify.

[Superfast Matt McCoy]

Originally posted by exFSAE:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stickboy:
Due to the firing order of a "long/big bang" engine, the power pulses are clumped closer together and there is a period of crank rotation where absolutely nothing is going on. This offers the tire enough time to settle and gain traction before the next pulse.

I highly doubt this. </div></BLOCKQUOTE>

Without looking at any data, I am inclined to believe this theory. It's the same principal as ABS, sure it happens at a much higher Hz but you're talking about racing riders who are at the edge of the traction of the tire as opposed to ABS which is designed for soccer moms standing on the brakes and screaming.

Why do you doubt with so much boldness and italicness?

[exFSAE]

Originally posted by Superfast Matt McCoy:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by exFSAE:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stickboy:
Due to the firing order of a "long/big bang" engine, the power pulses are clumped closer together and there is a period of crank rotation where absolutely nothing is going on. This offers the tire enough time to settle and gain traction before the next pulse.

I highly doubt this. </div></BLOCKQUOTE>

Without looking at any data, I am inclined to believe this theory. It's the same principal as ABS, sure it happens at a much higher Hz but you're talking about racing riders who are at the edge of the traction of the tire as opposed to ABS which is designed for soccer moms standing on the brakes and screaming.

Why do you doubt with so much boldness and italicness? </div></BLOCKQUOTE>

Not sure I'd say it's the same idea as ABS. ABS doesn't gain grip by alternating between stick and slip. That's just a fallout of the controller (I think). Holding a constant brake torque near or just below the "peak" would shorten braking distances even more. But since that peak changes based on load, road surface, speed, temperature.. you can't put that into a controller in advance. Best it can do is pulse the brake pressure when it sees wheelspeed on a corner drop below some treshhold.

http://www.ae.gatech.edu/people/ptsiotra/Papers/vsd02.pdf

Tire's don't generate grip instantly. There's a minimum time (or distance) constant involved. High engine RPMs and low rolling speed (where you'd be most concerned for drive traction) means I doubt you're anywhere near that required time for the tire to "settle."

Besides, you're talking about a bunch of torque on each pulse. Conceivably twice as much as normal? So as if it wasn't hard enough controlling a more regular "stream" of torque to the wheels, now you're going BREAK TRACTION - do nothing - BREAK TRACTION - do nothing - BREAK TRACTION.

Doesn't make any sense. Don't think that's how contact friction works.

[VFR750R]

i think the idea is based on static friction being higher then kinetic friction. there are a lot of inertia and springs in the system. You are right that maintaining the edge of grip is better then occilating the load, but motorcycles have such small contact patches even professional riders struggle to ride that limit.
I have never ridden a big bang but i could imagine at that limit, the rider with a big bang feels it like abs, it gives more feedback to where that limit is. A even firing engine will break loose and spin up like a automatic transmission in the snow. In that article it talks about how M. Doohan could ride the even firing engine but his teammates couldn't.

[Wesley]

Would not a torque pulse on a constant-speed tire have to generate deflection within the tire before it can generate thrust (and slip?) Indicating that it takes more power to go from the non-slip constant-speed to slip than it does to go from already deformed tire to slip?

Thats what I understood the big-bang useful for.

You generate a torque pulse, you deform the rubber initially, then generate slip on top of that. Then theres a slack period where the rubber springs back (adding that bit of torque back with a little loss) and it settles out for the next one.

If you even out the torque pulses, you have a more constant deformation in the tire, and the torque has less to overcome (less possible thrust.) and enters slip much more quickly.

I don't know that much about tire kinematics.

Try to shove a box across the floor by a series of impulses, and then by constant force. Under constant force, after that initial resistant force peak, you have a constant F, with the first method, your net generated force must be higher to overcome the friction.

Now just reverse that, and have the friction generate the movement, and the force of acceleration oppose the motion. You are maintaining it on the edge of grip, but the static edge of grip, giving you an oscillating but higher and yet more controllable peak.

[murpia]

I'm still very interested to understand the torque-related force actually at the contact patch not the crankshaft...

In a 'normal' bike you have pistons -> crank -> maybe a flywheel -> reduction gear -> clutch -> gearbox input shaft -> dogs & gears -> gearbox output shaft -> chain -> hub -> spokes -> rim -> tyre sidewall -> tyre contact patch (did I miss anything?).

All have finite stiffnesses, significant inertias and often backlash present. Some bikes (though I suspect not MotoGP) have compliant drives from the chain to the hub. Also the chain is free to 'slap' up and down and there are a large number of joints transmitting torque in the form of tension.

Can we really accept this system will reliably and repeatably transmit torque oscillations at hundred of Hz?

Regards, Ian

[VFR750R]

Lets consider the following
Single cylinder big bang 150mph corner exit
12,000rpm
Tire ~23" tall for 6.02ft rollout

150mph = 220ft/s = 36.5 rev/s of tire
12,000rpm = 200rev/s = 100 firings/s
or 5.5rev engine/tire rev and 2.75firings/tire rev
360deg / 2.75 firings = 130deg of wheel rotation per engine firing
A single delievers all its force to the tire in about 90 deg of crank rotation/720deg cycle. So
90/720 = 1/8th
1/8*130 = 16.25deg or tire rotation followed by a lull 130-16.25deg long = 113.75deg.
So the effect of a big bang is 2.75 pulses per wheel rotation. And those 'pulses' only happen ~45deg of wheel rotation. This assumes stiff drivetrain components, but I could definitely see the tire responding to this.

[Superfast Matt McCoy]

Originally posted by exFSAE:
ABS doesn't gain grip by alternating between stick and slip. That's just a fallout of the controller (I think).

I'm pretty sure that's exactly what ABS does and is intended to do; allow the driver to maintain steering control with the brake applied. The shortened stopping distance is the byproduct (except on slick surfaces).

Similarly, I see the benefit of the big bang in allowing the rider to dance close to the edge of traction in cornering without being so close to dumping the bike.

I can't comment on the big bang's effectiveness, but it seems plausible enough for further investigation. I think VFR's math shows that as well. In any case, I think its time has come and gone.

[exFSAE]

Would you be traction limited at 150mph? I would think this would be a bigger deal at low speeds...

[Wesley]

I agree Matt, it gives the tire a chance to recover enough to get back inside the traction circle and generate lateral thrust, but also most importantly give the driver some feedback.

ABS basically does two things - prevents idiots from locking up the brakes and losing steering control (aka the blind stomp) and also modulates braking force to allow the wheel to turn in inclement weather when drivers are likely to overcompensate and lock the brakes causing hydroplaning.

ABS, with a good driver, lengthens dry stopping distances.

In a racing application, stopping distances aren't important. Panic stops aren't really designed for. But locking the inside wheel braking on turn in kills all cornering force that wheel would develop, and simply produces a force opposite to vehicle motion. ABS allows that wheel to be modulated, reducing braking force and dropping the tire back into the traction circle where lateral grip can be generated.

Right?

[Superfast Matt McCoy]

Originally posted by exFSAE:
Would you be traction limited at 150mph? I would think this would be a bigger deal at low speeds...

During Cornering? Absolutely. And even in low speed corners, maintaining maximum corner speed is paramount.

[stickboy]

Thats the right idea Wesley. Its just the same principles working in reverse. The goal is to keep the tire in control so that you can continue to generate longitudinal an/or lateral force and also to keep in control of the vehicle.


Would you be traction limited at 150mph? I would think this would be a bigger deal at low speeds...

The benefits of this setup would defnetely be more apparent at low speeds, but it won't hinder you at high speeds. Even at high speeds it would still hold advantages over a conventional firing order. At high speeds and higher revs, these power "pulses" are coming with a higher frequency, but still are more manageable than if they were affecting the tire twice as often. Besides, the benefits of this only pertain to corner entry and exit. Also, a big bang or similar type motorcycle engine is only going to be found in MotoGP. WSBK banned it and any other track oriented motorcycle just isn't powerful enough for it to be practical. The different crank examined at the beginning of this post is a different story, as it is designed solely to reduce mechanical inefficiency and offer better response to the rider. Neither technology offers any power gains; they are designed to refine the package and help the parts of the vehicle work in harmony.

[VFR750R]

which brings up the point...is yamaha selling it to us, or are they homoglating it for ama, british, and world superbike where they'll get another 70hp by turning the snot out of it.

[TMichaels]

ABS, with a good driver, lengthens dry stopping distances.

I'm sorry Wesley, but this is not true. ABS allows the driver to apply a very high gradient of pressure to the system thus shortening the dead time. It also uses every individual tyre in its optimum slip. No driver is able to do this, because he does not have 4 feet to modulate the brake pressure at each wheel separately.

[Wesley]

Are you talking about a race ABS system or an OEM system?

I was talking about average guy-OEM. Not race inspired.

[VFR750R]

the fastest car 0-100-0 is the Ultima GTR. look it up on youtube. It has zero brake electonics.
But...the dodge viper acr has the shortest stopping distances of any 'real' production car, with the oem abs system turned on.

[TMichaels]

As long as not every kind of car ist tested under the same conditions you cannot tell which one is best in a special discipline.

@Wesley: What is the difference between a Race-ABS and an OEM-ABS. If the supplier knows what he does, then there is no difference in the performance of the systems.

[Wesley]

The difference is whether or not all 4 wheels are independently controlled by ABS.

[VFR750R]

How else would they do it? i thought all systems regulated all 4 tires independently short of a 92 S10 or something. Otherwise, what's the point?

[TMichaels]

The control of all 4 wheels independently is standard since more than 10 years.

[L B0MB]

The answer to the 90° crankshaft and irregular interval firing from Masao Furusawa, Executive Officer of Yamaha Motor Co himself

Note: He doesnt subscribe to the big bang theory

http://www.sae.org/mags/AEI/5586

[Professor Gas Can]

Cool article. Pretty much wraps up the question...unless...
Who has a lot of time to see if this works for a Formula SAE car as well? It would probably wouldn't have much of an effect on the car's cornering, but how much....and you'd probably lose a little bit of power due to the complicated tuning/imbalance of the int/exh manifolds.
Where's a grad student when you need one?

-Ian

[VFR750R]

After reading that article I think I finally understand the inertia torque argument. It is just another way of looking at the secondary vibration of inline 4 cylinders. The difference in speed between the pistons approaching BDC versus the pair approaching TDC creates a vertical vibration, but that force is transmitted through the crankshaft (which is not aligned vertically at max force) which causes a torque on the crankshaft.

I also would like to add friction. Lets see what everyone thinks about this.
At TDC/BDC for each cylinder pair the velocity/friction of the piston assemblies goes to zero. At 90 deg from that its at a maximum, which may have a measurable effect on torque at the wheel.

[L B0MB]

i think the two designs provide the same output averaged over time but the 90 degree crank allows a more progressing feel

so the only benefit is in driver feedback

[Wesley]

Even in sand and gravel, ABS generally increases stopping distances, because a locked wheel causes a buildup in front of the tire that slows the vehicle. Additionally, since ABS is a comparative system, on ice, if the driver locks multiple wheels, the system loses effectiveness.

I still hold that stopping distances are not always shortened using ABS with a skilled driver. Overall performance increased? Sure. But not stopping distances.

[VFR750R]

Wes, your arguement seems to be around conditions which require tire lockup or there is no way around lockup as grounds for not having abs. This seems quite silly, as your examples as questionable and represent very small percentages of vehicle use.
As far as off-road (sand and gravel), I've never heard of build up helping breaking except in deep mud/sand. Hardly the place abs was designed for. Even so, keeping the tire rotating for tread cleaning seems to be worth something. I can't imagine abs hurts in this environment to the extent you claim.

As far as on-road...which everyone else here is talking about, no buildup anyhow.

A driver cannot possibly process information as fast as today's abs systems. And today's abs systems are integrated to the point where you can do at-limit braking while turning. A driver cannot do this because a driver cannot apply maximum braking effort to 4 wheels independently to match the drastically different normal forces on them. At best, a driver can match an abs system under perfect conditions in a straight line. So under that condition abs doesn't shorten braking distance, but under all other conditions it does. It also means it will get the most out of the brakes whether the tires are new/old/cold/hot, tank full/empty, regardless of passengers (or location of passengers), or any other weight changes. A driver has to re-learn the limits whenever a change is made. Even different kinds of pavement pose a challenge to the race-car driver, but not to abs.

And the standard deviation in braking over multiple attempts will be better with abs then without, even in a straight line.

Ice doesn't even deserve mention here. If traction is to the point abs can't work (and it still works quite well in most snow and ice i've driven in), you're f'd anyway.

My corvette's abs, traction, and stability control is way more talented then I am, and it's saved my ass at least a couple times. I'm no race-car driver, but the shit works.

[Fred G]

ABS and sand don't go together...

If you ever fly off a track into a sandtrap, you want to lock up and dig into the sand. Otherwise you skip along the top of the sand, then into a barrier.

Fred

[TMichaels]

In most of the cases I have seen, the cars fly over sandtraps after leaving the track because of the usually hard suspension. Just remember Michael Schumacher's accident in silverstone.

ABS increases the safety of race cars, because it lowers the risk of loosing control over the car.

[Wesley]

You're exactly right - my statement was only in regards to straight line. I'm not arguing that ABS/Traction systems aren't worth it. I never said that. In fact:

" I still hold that stopping distances are not always shortened using ABS with a skilled driver. Overall performance increased? Sure. But not stopping distances."

I never argued anything but straight line stopping. I'm not going to try to tell you computer controlled braking systems don't result in faster cars.

[Pete Marsh]

If ABS is so fantastic on racing cars why did Porsche remove it from their GT3 racers? I because the competitors wanted it gone!

ABS has trouble dealing with the 'abnormal' situations that are more common on the track and the result of a confused ABS system is a big crash. A couple of years ago a Porsche cup driver was badly injured in a crash caused by ABS failure here in Aus and there was a lot of talk about it. Not a system failure as in a broken wire, but a combination of inputs that resulted in no brakes and then WALL!!

The sort of stuff it doesn't like -
flat tyres, braking over kerbs, one side in the dirt, marbles on tyres, etc
The biggest problem is ABS prevents the driver from intentionally locking the wheels solid, which is required to stop a spinning car crossing the racing line and getting T boned.

Pete

Ps whats this got to do with crank shafts? The Kwacka article is interesting, but it seems the big advantage is in constant cornering, which Moto GP do a lot of and we do very little of.

[Professor Gas Can]

"If you ask me, Muhammad Ali in his prime was much better than anti-lock brakes."
That should adequately kill the ABS debate and this thread, probably.

[Jones]

Regarding twins allowing a tire to recover whereas inline fours' continuous power delivery don't, weird as it seems, it is true. Case in point, when Yves Briquet rode in World Supersport in the mid 1990s on a Ducati twin, in the days before Pirelli had developed a tire that could compete at the top, he had very good success. (Some might remember Yves nearly winning an AMA Supersport race in the rain at Daytona in the early 1990s on a borrowed bike supported by Team Rayce, that wasn't a Ducati.) But in Europe, using the same tire on the same tracks with the same rider but on an inline bike, corner-exit traction was greatly reduced. This was at the time attributed to the different power pulses between a twin and inline four. Traction control can help but not cure this issue, which is why big-bang engines are still tried. Basically, better traction needs less control, or rather the point where control is needed is at a higher level. Sometimes reality is not intuitive, like with counter steering. And by the way, there is much more to the new R1's engine than this and fun marketing. Let's all see what we think once the bikes get out.

[DFT]

In the end it's the results that matter and based on what I've read and seen it seems that the R1 went from being the "peakiest" inline four to the one with the most grunt in the same year that they introduced their new crankshaft. Although I'm not sure how much of that is due to the cross plane crankshaft, I would not write it off as a coincidence. This video is a pretty good comparison of the new R1 to the CBR1000: http://www.youtube.com/watch?v=ST4rDqrnVZ4

[Grant Mahler]

Originally posted by Jones:
Regarding twins allowing a tire to recover whereas inline fours' continuous power delivery don't, weird as it seems, it is true. Case in point, when Yves Briquet rode in World Supersport in the mid 1990s on a Ducati twin, in the days before Pirelli had developed a tire that could compete at the top, he had very good success. (Some might remember Yves nearly winning an AMA Supersport race in the rain at Daytona in the early 1990s on a borrowed bike supported by Team Rayce, that wasn't a Ducati.) But in Europe, using the same tire on the same tracks with the same rider but on an inline bike, corner-exit traction was greatly reduced. This was at the time attributed to the different power pulses between a twin and inline four. Traction control can help but not cure this issue, which is why big-bang engines are still tried. Basically, better traction needs less control, or rather the point where control is needed is at a higher level. Sometimes reality is not intuitive, like with counter steering. And by the way, there is much more to the new R1's engine than this and fun marketing. Let's all see what we think once the bikes get out.

Holy thread from the dead Batman.

The articles and comments above were all in regards to cross plane vs flat plane crankshafts, not 2 vs 4 cylinders. Some similar ideas to be sure, but you're pointing out something different than the argument being made.

[VFR750R]

Originally posted by DFT:
In the end it's the results that matter and based on what I've read and seen it seems that the R1 went from being the "peakiest" inline four to the one with the most grunt in the same year that they introduced their new crankshaft. Although I'm not sure how much of that is due to the cross plane crankshaft, I would not write it off as a coincidence. This video is a pretty good comparison of the new R1 to the CBR1000: http://www.youtube.com/watch?v=ST4rDqrnVZ4

I noticed they kept talking about how much lowend power the R1 had and how much harder it would pull in rollons. I looked up some dyno curves for the 2009 R1 vs CBR1000RR and the CBR stomps a mudhole in the R1 all the way to the 11,000rpm. In fact, the larger valves looks to be the most significant improvement to the powerband.


I wonder if Yamaha was able to significantly reduce crankshaft inertia, which would allow it to 'spin-up' much faster but on a 5th or 6th gear dyno pull wouldn't show up because the rate of accel is much lower then say 2nd or 3rd.

If the R1 really works out, I suspect honda will just build a V4 CBR as it gets rid of the 'inertia torque', same as a cross plane inline 4, but its much shorter crank and shared pins allow for a much lighter lower inertia crankshaft.

http://www.tamparacing.com/for...4887-09-r1-dyno.html (http://www.tamparacing.com/forums/bike-tech/544887-09-r1-dyno.html)

[Homemade WRX]

quite an interesting concept...its almost like having two seperate 2-cylinder motors sharing one crank and well, everything else in the motor...I do however wonder how this would translate to a 'V' or even more so a flat/boxer configuration...? In these cases it would also seem much easier to deal with a dual plenum and seperate exhaust systems. More so how it would help reduce inherent crank issues/firing order of a flat-4.

Crap, I think I just made a new experiment for myself.

I won't comment on ABS lol

[Kevin Ash]

I'm a bike journalist and technical writer too and have looked into Yamaha's crossplane crank in detail, and the real reason they use it hasn't been touched on in this thread yet. There's a full feature on my own website at www.ashonbikes.com/cross-plane_crank (http://www.ashonbikes.com/cross-plane_crank) . The key to it is that in a flat plane crank all four pistons are stationary together, then accelerate, then stop again, all at the same time. If you take the crank and piston system in isolation and spin it (we'll have zero friction for the moment...), this means the pistons' kinetic energy is all transferred to the crank when they're at BDC and TDC, so at that stage the crank is spinning fastest. 90 degrees later all the pistons are at maximum speed, and that energy has come from the crank which in turn slows down. 90 degrees further on again and the pistons have stopped and crank's spinning faster. This is a sort of background cyclic wobble in the crank's rotation (but nothing to do with balance) which adds a fuzzy edge to the power delivery, and it IS noticeable by ordinary mortals on the R1, at least on the track. It's independent of the torque output from the engine's combustion and merely overlays it in a near-sinusoidal pattern with a net torque of zero.
In the cross plane configuration the pistons' accelerations cancel out - as one is speeding up another is slowing down, and the inertial torque (which depends on the mass of the pistons and conrods, not the crank) is almost zero (almost because the conrods have finite length and pistons spend longer in the lower 180 degrees than the upper).
The uneven firing intervals are simply a side effect, not Yamaha's aim, and do nothing to increase grip - Pirelli did some research on this a few years ago and could find no evidence of the Big Bang idea increasing grip.
The cross plane idea is not marketing guff, Ducati has been quietly enjoying the benefits with its 90 degree twins for years (almost zero inertial torque) which is why they've configured the MotoGP bike effectively as two V-twins side by side, and its a factor in several car engine designs.
Hope this is of interest!

[VFR750R]

Well stated.
Your article explained the phenomenon better then any I have read. You assume a lot using 2ftlbs as a example. I'd be interested to know what the real order of magnitude of those forces end up being. Obviously the lighter the reciprocating parts the less the torque, but the lower the system inertia the higher the left over torque variation at the tire contact point. Might be Yamahas true goal as crank inertia might be able to be lowered a tremendous amount without effecting felt vibration or riders control. That helps power obviously but also lessens gyroscopic effect of the crank which definitely can be felt (imagine 1000cc bike with engine inertia of 600cc bike, or 600cc bike with inertia of 400cc) Lets hope the R6 comes next!

It also points at much reduced driving frequency and amplitude into valvetrain (always a welcome thing).

Many have assumed it has a 'big-bang' effect as no previous engines to use a 'big-bang' engine have been inline 4's and have, like you've stated, negligible inertia torque.

[dende890]

Originally posted by Wesley:
You're exactly right - my statement was only in regards to straight line. I'm not arguing that ABS/Traction systems aren't worth it. I never said that. In fact:

" I still hold that stopping distances are not always shortened using ABS with a skilled driver. Overall performance increased? Sure. But not stopping distances."

I never argued anything but straight line stopping. I'm not going to try to tell you computer controlled braking systems don't result in faster cars.

I drove cars in Soviet Union till 1988 until I emigrated to the US.
I lived in Ural Mountains where at least 7 month snow and very slick roads.
We never had any ABS or other stability control systems on cars. I drove at least 40,000 miles every year for 15 years under such conditions.
Now I do tracks in advanced group and every instructor and drivers who sitting with me flattered me with my outstanding driving skills.
All thanks to the Ural Mountains bad weather.
I so accustomed to brake by engine switching the gears down with blimp that it was very difficult on tracks in the beginning start braking by brakes only. Sometimes in order to move from the complete stop I pressed very slightly brake pedal and then apply on the gas pedal so icy the road was. I was braking in a Rally manner by pumping the brakes as fast as possible even in Summer time just to keep my mind ready for the icy winter to prevent the locking of the wheels. It happened in America that for at least 15 year I drove sedans and vans all over USA in different weather and always was laughing on how easy it was with such a good roads and ABS systems compare to Russia.
It was very difficult for years to my mind to stop pumping the brakes and keep the pedal under big constant reassure in situations where the short stop distance needed.
So, I'm for kissing the ABS, my "parachute" on the roads.

Lev.
From my very kin feeling I can say that ABS is no comparison to non ABS similar car especially under slippery conditions.
I escape a few times 100% collisions under slippery roads only because of ABS tremendous help, it definitely shorten the distance, believe to my eyesight and feelings trained forever by the bad Russian roads.
Yes, ABS isn't probably good for some Rally driving where you need to lock the wheels for a split second to put the car in sliding and rotate it easily then, but for regular day driving disregarding of experience the ABS is a big safety net.

[Kevin Ash]

Originally posted by VFR750R:
You assume a lot using 2ftlbs as a example. I'd be interested to know what the real order of magnitude of those forces end up being.

I assumed far too little as it turned out! I did a simplified calculation and was shocked at the level of inertial torque so I ran it by a designer friend at Prodrive and he came up with similar numbers using an SHM method. Each piston at 12,000rpm, if it weighs 0.2kg, generates around a 120lb.ft peak, which reverses every half a revolution. With all four doing it together that's almost 500lb.ft, and I didn't even include the conrods! You can see what I did here:
/www.ashonbikes.com/inertial_torque (http://www.ashonbikes.com/inertial_torque)
Yamaha keeps claiming the advantage is an improvement in feel and directness, and I think this could come from not having to damp out these huge torque pulses with torsional springs in the clutch or some other method. Without these you'd imagine these big pulses could do some damage to a transmission of a flat plane four, but in a cross plane one the transmission would be okay, and the crank would be more directly connected to the rear wheel, which ought to give better feedback and control to the rider. I can't imagine road riders benefit at all but to the top guys on the track it might well make a useful difference. Yamaha's doing well enough in MotoGP to suggest it does.

[Scrappy]

This is a very interesting topic, and I figured I would throw in some related info about the tire slip that was mentioned earlier in this post.

http://www.motorcyclenews.com/...-two-wheel-drive-r1/ (http://www.motorcyclenews.com/MCN/News/newsresults/Customs--modified-bikes/2009/May/may1809-secrets-of-ohlins-two-wheel-drive-r1/)

This is a really cool article about a hydraulic 2wd system that Ohlins developed for both on and off road bikes, including an R1. In this article, the Ohlins R&D manager who was interviewed about their 2wd system for an R1 mentions specific tire slip numbers at speed. At 80km/h (50 mph) steady state, the rubber deformation accounts for .5% slip, and at 200km/h (125 mph) under full throttle, it accounts for up to 5% slip.

This blew my mind, and it seems apparent that any increased dampening or cancelling of the inertial torque at the crankshaft would benefit the throttle feel and control under both steady state and heavy accel riding. With the cross plane crank, I would imagine you are relying much less on the springs in the clutch basket to smooth out those high frequency inertial torque "pulses". Since the rubber already deforms as much as it does regardless of what crank the bike has, it seems that removing that extra variable of how much those pulses are being transmitted through the drivetrain to the contact patch would make the bike more planted and predictable. I think it would be extremely hard for an average rider on the street to feel the difference though.

[Akshay Jain]

So much arguments for ABS here.
So i would like to ask if anyone has used ABS system on their FSAE cars and any difference it made?

[L B0MB]

Good points there Scrappy... Only freaks like Valentino would ever notice it... Not your average chimp with 18 grand and a death wish

[Tilman]

Originally posted by Akshay Jain:
So much arguments for ABS here.
So i would like to ask if anyone has used ABS system on their FSAE cars and any difference it made?

Stuttgart has got a Bosch motorsport ABS in their current car. Drop them a mail ...

[Adambomb]

Hah, funny I never noticed this post before. Thinking it came about one of those times I was too busy for the whole "internet" thing. Anyway, on the cross-plane crank discussion...

First off, for Yamaha to claim that a cross-plane crank 4 cyl. has never been put in a sport bike is 100% false. My '88 Ninja 600 has a cross-plane crank. Firing order is 1-2-3-4, and phasing is something like 1 @ 0 deg., 2 @ 90 deg., 3 @ 360 deg., 4 @ 450 deg. In other words, 1+2, and 3+4 are paired to fire 90 deg. off each other, with a 270 "lull" in between. The result sounds almost like a cross between a Ducati and a small block Chevy at 11,000 rpm (SWEET). The cams also look funny due to the 1-2-3-4 firing order, the lobes all follow each other in a spiral pattern. On top of this, in true '80s style, the Ninja has dual exhaust, with 1+2 and 3+4 paired. At idle, you can hear the close-ness of the pulses in stereo.

Listening to a lot of older 4-cyl Japanese bikes, I think this was actually the norm. If I had to guess, back in the days when 10,000 rpm was extreme on a bike, it was probably done for vibration more than anything else. I don't buy into the whole "breaking traction then regaining traction" thing, if that were the case with tire behavior then it would be in our best interest to do such ridiculous things like remove our shocks completely and have 200% anti-squat, etc. to get really high instantaneous loading. Also, the transmission of pulses subject has been covered, and while it is debatable whether or not that pulse could even be seen after losses through the gears, chain, etc, don't forget that most of these bikes also have some sort of torsional damper mounted between the sprocket and the wheel, which would essentially serve as a low-pass filter.

When I was a TA for our uni's measurements and instrumentation class, I put together a little video. Recorded the intake noise of my 'ol Ninja at WOT from 5-80 mph, then analyzed it with Matlab's specgram function. Basically took an FFT at each time step. Pretty interesting. In the video below the x-axis is time, and the y-axis is frequency, while the spectral intensity from the FFT is the color scale. Pretty cool.

'88 Ninja 600, WOT 5-80 mph (http://www.public.iastate.edu/%7Eadambomb/intake_WOT_specgram.wmv)