Guest Blog: Mat Oxley - Could a V4 M1 be Valentino Rossi’s silver bullet?

MotoMatters.com is delighted to feature the work of iconic MotoGP writer Mat Oxley. Oxley is a former racer, TT winner and highly respected author of biographies of world champions Mick Doohan and Valentino Rossi, and currently writes for Motor Sport Magazine, where he is MotoGP correspondent. We are featuring sections from Oxley's blogs, which are posted in full on the Motor Sport Magazine website.


Could a V4 M1 be Valentino Rossi’s silver bullet?

Ducati and Honda V4s have won the last 22 MotoGP races, so is it time for Yamaha to ditch its faithful inline-four engine?

Valentino Rossi finally said it. After finishing a miserable seventh on Sunday in front of his adoring fans, the seven-time MotoGP champion wondered aloud: “Ducati and Honda have V4 engines; we have an inline four – maybe this is the problem…”

But would a V4 M1 really get Rossi and Yamaha back to their winning ways? In other words, is a V4 engine better than an inline-four engine?

It all depends on how you look at it. V4 engines have won the last 22 races, but does that prove beyond any reasonable doubt that a V4 is best, or is it simply a case of Ducati and Honda working more efficiently on their engine internals and electronics than Yamaha?

Most MotoGP engineers believe that V4s and inline fours are like swings and roundabouts: they’re both better in some ways and worse in others. Everything in racing is a compromise. It’s all about maximising your advantages and minimising your disadvantages.

An inline-four engine is more compact, so chassis engineers can move it fore and aft and up and down to find the ideal centre of mass and so on. This is why Yamaha’s M1 has been the best-handling MotoGP bike for the past decade and a half.

Only a few years ago, many wondered if the 90-degree V4, so beloved of Ducati, had had its day. The engine was too long, they said, which explained the Desmosedici’s woeful steering and handling problems, because engineers were unable to put the engine in the right place. Then Honda revealed that its RC213V also uses a 90-degree vee. The answer for both factories was to rotate the engine slightly backwards in the frame to create more space for the chassis designers to do their job, but still, there’s no doubt that the M1 can use more corner speed than its main rivals.

Read the rest of Mat Oxley's blog on the Motor Sport Magazine website.

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Total votes: 8
Total votes: 7

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Comments

Mat refers to the Yamaha needing more corner speed. I was under the impression that, at least with Lorenzo, no bike was faster through the corner. So has this changed because the engine has changed or because the riding styles are different?

Total votes: 10

I think Mat means it can actually use more corner speed than its rivals, not it needs more corner speed.

Total votes: 26

Mass centralization has been the holy grail of chassis design for more decades than I can recall, long before people started calling it that. But it really grew legs when the top class returned to four-strokes almost two decades ago. It mattered before then, but not as much as it does now. In the two stroke 500cc era, when you had engines roughly the size and shape of a four-slice toaster, mass was more naturally centralized* (except for the huge fuel loads) than it became when the powers that be decided life was sweeter with a frosting of cams and valves on top of everyone's racing engines. From a simple analysis standpoint, Engineers always want a spherical mass to play with, as it will have the same inertia in pitch, roll, and yaw, just like a Beach Ball. But the reality is that engines are not spherical, and pitch, roll, and yaw do not have equal precedence when it comes to lap times. The inline fours would appear (perhaps falsely, see below) to have a packaging advantage in the fore and aft direction (pitch), but those furthest outboard bits of crankshaft, connecting rod, piston, valves, and camshaft inhibit roll (side to side) motion (even if, as Mr. Oxley explained to the rest of us tag-alongs, the four center flywheel bits of the M1 engine are much more massive than the emaciated outboard four). Of course, the word is inhibit, not destroy, and there are other ways of improving roll response. Nobody is saying the Yamaha wont snap over to 60 degrees.

So which direction is more important? Easy answer: whichever one the Michelin tires respond to. If the current generation of Michelins are less than the mutt's nuts when it comes to edge grip, and are hyper sensitive to fore and aft loading, then one direction may well have precedence over the other (because you don't want to stay on the edge; you want to pick the bike back up quickly onto the fatter part of the tire). If the Michelins suddenly start cleaving to the racing surface at maximum lean like stink on a monkey, then the relative precedence with regard to pitch and roll may change (the bike now being perfectly happy to stay at maximum lean angle longer). Yaw, as always, is sitting at the kiddie table. Not that yaw is inconsequential, but rather because pitch and roll wear the long pants, and yaw gets whatever is left.

What I suspect is happening is that there is a critical zone of lean angle that is impacting the current ECU package's ability to make the Michelin tires happy (and that is the ECU's main task). In this critical zone we have more than a few things happening. The bike is leaned over, but at the same time the contact patches have also migrated inboard as well, and to make things even more fun, the rear has migrated significantly further inboard than the front. So both the inertia of the system's mass, the mass location both vertically and horizontally, and how those masses are connected to the chassis are impacting both the flex and damping of that mass when leaned over. And not just in roll, as pitch response is impacted as well.

And that may lead to some issues not immediately apparent. Due to contact patch migration, the outboard bits move more than the inboard ones in roll. So what may be hindering the inline fours is not their ability to bank, but that they may wind up with a greater inertia variation in pitch due to their roll characteristics (compared to what the V-4's are seeing). When banked over, the longer crankshaft is now impacting pitch...and the Spec ECU/Michelin porridge may be going sour on these inline four ingredients.

But I really don't know. What I do know is that a lot of very smart people are struggling with this, and if it were just a primary effect that was the issue they would have sorted it by now. Which leads me to conclude they are wrestling with a secondary or tertiary effect that will be deuce difficult to get right. I also suspect they will not be able to solve this with the crankshaft mass wrong, as that may be masking a more coherent analysis of the system. So before the lads from Iwata saw their engine in half and put it back together as a V4, they need to get the spinning bits sized correctly, let the ECU talent they have (finally!) brought onboard get a handle on the sparky bits inside the Magneti Marelli ECU, and then have Herr Folger flog the hell out of it. Then they can decide if the bandsaw is required.

Or if the real changes required are in the structure of Yamaha itself.

Because, in the end, I believe the real answer is this: Ducati does not have the best bike on the grid because of the structure of their engine, but because of the structure of their team. What Dall'igna has built that is even more impressive than his current race bike is a finely honed organization where all the parts are connected to each other (e.g., riders, crew chiefs, on track technical support, factory engineering and development, and so forth), mutually supportive, and integrated into a high-performance whole. Just one example; in Kevin Cameron's latest piece he drops another mind bomb on us all. Ducati has hired in a predictive software group to help with analyzing how the Michelin tires can be expected to behave...and degrade...under race conditions, possibly including a capability to analyze the effect of the Dunlop Moto2 rubber they actually race on (but don't really practice on most of the weekend). Such a concept presented to Iwata would probably result in a multi year round of management discussions, followed by an effort to see if they could make their own version in-house. Gigi's response to the opportunity appears to be "Let's get some and try it". And as long as that is the difference between Ducati and some other Teams, I really don't think which way your cylinders are pointing is going to be the deciding factor. There would appear to be more to gain from looking at Dall'igna's racing organization structure than the structure of his engines. Cheers.

*Unless you were mighty Honda, and decided that slinging the fuel underneath the bike was a good idea, which it decidedly was not. This is not to slander Honda, but to show that much of life's progress still consists of taking the wrong fork in the road, and then having the wisdom to double back and take the better one. Honda's crankshaft inertia was too light previously, but appears currently to be pretty much on the mark. Suzuki, with less technical and monetary resources than Honda, took the Goldilocks and the Three Bears approach. Too light, then too heavy...now pretty close. Yamaha has spent a long time strolling happily in the sunshine. Perhaps they forgot that there are also many lessons to be learned by stumbling in the dark and occasionally falling down.

Total votes: 39

I found it interesting to note that the V4 guys all use external crankshaft weights. I've been wondering for a long time why Dorna don't allow this very thing and, lo and behold, it turns out the have been all along. Knowing that Honda and Ducati can change their crankshaft inertia on a track-to-track basis puts Yamaha's current struggles in a different light. 

It's said Yamaha can't use the same external weights because their engine is too wide. This may be true of external weights on the ends of the crankshaft, but there's nothing preventing them from adding an external weight geared to the crankshaft on the engine centerline behind the cylinders and above the gearbox, perhaps? Nothing is impossible, it's just a matter of the trade offs needed to implement the idea.

Total votes: 7

This reminds me of Rossi's first season on the Ducati, fixating on a massive and fundamental change that will 'fix' the bike. Going from stressed airbox to twin spar didn't solve the Ducati's problems, going from I-4 to V-4 probably won't solve Yamaha's. If anything it will raise a raft of entirely new problems that will take Yamaha at least a year but probably two to sort out.

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The M1 isn't a bad bike, it has 10 podiums, 2 pole positions and a fastest lap this year. It's problems are fractions of a percent, if it's throttle response were more refined so it didn't spin up and burn out it's rear tyre those fractions might even be in it's favour, but they're not.

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Regards the crankshaft weight issues. I think allowing the teams to have different weight flywheels would be a good compromise. It's a relatively cheap part, has the same effect as altering crankshaft weight and can be swapped without 'breaking the seal' on an engine. Limit it to three different flywheels that are set with the engine homologation and it won't increase costs much. It might not work but it might let a team in a situation like Yamaha's make the little refinement that brings the bike to the front, even if it means they run 'the heavy wheel' exclusively all season.

Total votes: 13

"Regards the crankshaft weight issues. I think allowing the teams to have different weight flywheels would be a good compromise."

That's a great idea!  You should suggest that to Mat.   BTW, don't read the article before you send the note, then tell us what he says.

Total votes: 4

Pretty sure I was agreeing with Oxley's idea, but don't let that stop you from being supercilious.

Total votes: 3

...it didn't at the time, as Rossi exasperatedly discovered. Going to twin spar left Rossi with a twin spar bike that still refused to turn. It took five years, Michelin tyres and control electronics to make the twin spar Desmosidici a front runner, Yamaha doing a complete redesign around a V4 could be a similar uphill struggle.

Total votes: 2

I'm wondering why a change to V4 would hurt the marketing for road bikes. Honda's Fireblade isn't a V4 and Ducati's Panagale is only a twin and it doesn't seem to have harmed either much. I suspect the old adage 'win on Sunday, sell on Monday' is more relevant.

Total votes: 4

A 3+1 configuration would be an interesting bunny trail for the lads from Iwata to hop down. Essentially, an inline triple with a single (fourth) cylinder V'd rearward off of the center. It may give them the best of both worlds, as the mass distribution would be closer to what they have now, which is important, since what they have now is what they know and understand from a chassis standpoint. They would lose a main bearing (from 5 to 4), significantly reduce the width (and the inertia) in the direction that may be currently haunting them, and the flywheel mass could be even more heavily concentrated (about the center pair shared with the additional V'd cylinder) near the center of the engine, with the outer pairs as light as they can make them while preserving structural integrity. You can also think of this as similar to a Honda RC211V V5...with one less cylinder in the back*. You would also have to account for the additional cam drive required, but their competition does not seem to be unduly penalized in this regard, and there is something to be said about the reduced distance across the forward bank yielding a more stable valve action for the outer pair of cylinders. And it would be a great fit for the rider's anatomy (very narrow at the back...and narrower up front than what they have now). Engine balance? Depends on what firing order they choose, and whether the rear cylinder is at 90 degrees (or a lessor angle), but that is why Yamaha has keen engineers. So keen are they that I am going to relieve myself from the task of incurring a massive headache thinking about it any further.

How the plumbing would work out would also be anyone's guess. Try to integrate all four cylinders intake and exhaust tuning as a whole? Be my guest. Build a screaming 750cc triple with essentially a Moto3 engine hanging off the back? Why not? They could certainly market it as an extension of their current (and excellent) three cylinder line-up as a "3+1". Well, at least until some WAG christens it "Quasimoto". But that would seem a slight price to pay to obtain the sanctuary offered by the top step of the podium. Cheers.

*We have all wondered whether the Honda V5 had the same cylinder capacity for the forward 3 and the aft 2. Someone else may have the definitive answer to this. With today's rules restricting bore size, a 3+1 would have to be the same (in order to be competitive).

Total votes: 7

I love the inline triple part.   I would be concerned about driving cam chain/gear separately for one piston though.   

I'd like to ride a bike with an engine like that.   I'd like the Honda V5 better.

Total votes: 5

A while back the story was that Yamaha's sensor processing was too slow - was this just an alternative way of saying the crankshaft inertia is too low so it responds faster than what can be reacted on?

I was unaware that the V4 allowed external flywheels of different inertias to be added - that can explain a lot if one knows if the V4 guys actually use this facility and by what percentage do they change the inertia?

I assume for Yamaha to add a flywheel to the jackshaft will offset the beneficial effect of the reverse rotating crankshaft?

Total votes: 4