CROSSPLANE inline 4 EXPLAINED in detail - How the YAMAHA R1 i4 differs from all other INLINE FOURS

00:00 Inline four is everywhere
01:52 What's a crossplane crankshaft
03:47 Crossplane and flat plane engine balance
12:37 Crossplane firing interval
14:50 Flat plane vs crossplane sound
18:06 Big bang engines in MotoGP and their benefits
24:22 Why no other bike went crossplane

The inline four cylinder engine is likely the most plentiful engine configuration in the world. It outnumbers other engine configurations because it offers an optimal blend of physical size, efficiency and power potential for most applications. And you can find an inline four engine in thousands upon thousands of different cars, bikes, boats, trucks, you name it – it’s everywhere. Walk through a city street almost anywhere in the world and chances are very slim that there isn't an inline four somewhere very near you.

And if you would take any of those countless inline four engines and opened it up inside you would find a crankshaft that looks like this. In fact at the heart of every single inline four you can find on the roads of the world lies pretty much the same crankshaft. There may be slight variations, different materials and manufacturing processes, a different number of counterweights. But all of them have essentially the same crankshaft.

Well all of them except one…….. This is the crankshaft in the Yamaha R1 and as you can see it’s different from all the others. So why is the Yamaha R1 inline four engine different from all the other inline fours out there and to what end? Well today I’m going to try and answer that question as thoroughly as possible with this detailed video. We will explain what the crossplane crankshaft is, how it differs from the flat plane, how this influences engine balance and what advantages and drawbacks it brings to the table and then with this information in mind we will talk about the history of big bang engines in MotoGP to see why they came into existence and what benefits they offer in the real world. We will end the video by answering the question of why other brands never adopted the crossplane crankshaft in their production bikes and why it never made it into another Yamaha fan favorite, the R6. So let’s get started.

Now, as you can see all the crankshafts inside every production inline four out there have 1 key feature in common and that is that two of the crank pins point up and the other two crank pins point down. The result is of course that pistons move in pairs. When two go up two must come down.
This type of crankshaft is called a flat plane crankshaft because all the crank pins are located in a single plane.

But starting with the 2009 model year Yamaha’s flagship 1 liter sportbike the R1 made a radical step away from this convention. As you can see its crankshaft doesn’t have two crank pins pointed up and the other two 180 degrees away. Instead each crank pin is pointing in its own direction. If we set our crankshaft so that the first crank pin points up then the second crank pin will be rotated 90 degrees from it. The third crank pin will be 180 degrees from the second and the fourth 90 degrees from the third. In more simple terms one points up, one left, one right, one down.

So why are 99.99% of inline four crankshafts out there flat plane instead of crossplane. The answer to that is that if one takes a rational objective approach towards designing an inline four engine the flat plane design offers more benefits and less drawbacks then a cross plane one. To understand why 99.99% of inline fours are flat plane we must understand how the primary and secondary engine balance of flat plane and crossplane inline fours differ from each other.

In flat plane inline four the pistons move in pairs. When two go up the other two go down. In other words piston one balances out piston two and piston three balances out piston 4.

A crossplane inline four also has an even number of pistons so we should have no problems with primary balance right? The inner two pistons are separated by 180 degrees so they balance each other out. The outer two pistons are also separated by 180 degrees so they also balance each other out. It’s the same thing as a flat plane but only with different pistons. So this means that the crossplane should have perfect primary balance just like the flat plane right? Wrong.
Yes the number of pistons is even but the problem is their distance from and relationship with the engine’s center of mass which results in the crossplane engine having something called a rocking couple.

A special thank you to my patrons:
Daniel
Peter Della Flora
Daniel Morgan
William
Richard Caldwell
Pepe
Brian Durning
Brian Alvarez

#d4a #crossplane #enginebalance #yamahar1

[RobSchofield]

That has to be the best engineering chain-of-reasoning explanation I have *ever* heard, in 40+ years as an Engineer myself. You are to be congratulated on your clarity of understanding and ability to get the message across. Superb!

[paulspice]

I'm a 71 year old biker with an engineering degree and you are the best teacher I have EVER listened to. Brilliant👍

[MLeoM]

I was shocked watching 5 minutes into the video how excellent it is explained and demonstrated verbally + visually and I have NEVER experienced learning about engines like this before in my entire life!

[manstersr]

Great explanation of the big bang 2 stroke engine. One thing you may have missed is how the two-stroke "power band" which you described as a brutal power delivery came in suddenly and made them hard to handle because the power would suddenly double or triple (for explanation purposes) when it hit a certain RPM, primarily due to the exhaust expansion chambers getting "on the pipe".

[wirenutt]

It's so great to listen to a complex and accurate engineering video like this instead of yet another simplistic, poorly researched and poorly written attempt at explaining something simple to begin with done by others. You will always have my attention with every video you release. Thank you for exercising my brain instead of putting me to sleep like so many others! A++++ for you, sir!

[VisioRacer]

Incredible video! I already knew this and got extremely fascinated when I first found out, but this video explains the whole point of uneven firing very very well. Everybody must get it after watching.

[psajeffreyocaya]

Your explanation, presentation and delivery is out this world. I never thought I could finish this entire video coming in with just mere curiosity on the crossplane design. Your way of "teaching" is bounds and leaps ahead of what could be the greatest teaching styles most everywhere. Thank you very much!

[pannusgarageanautomotivewo]

I am 16 years old and i have been studying automobile since my childhood, I have learnt a lot from your videos gaining knowledge of complex concepts in simple yet detailed manner.. Thank you❤❤❤

[Gixerpilot]

The fact you did this in perfect English which isn’t your first language is just amazing !!!

[AVweb]

This is f^%$ing brilliant. Well done. Even I get it now.

[calinkln]

Incredible how this guy can explain complicated stuff and make it easy to understand for the average person. Time and time again. Nice work!

[nbowlingtrio]

People need to realize and recognize the amount of effort you put into your videos. Well done sir

[tylera.]

"Rev happiness" is the best way I've ever heard it put. Explains why I love my rotary engines & motorcycles so much

[ankitpandey]

Incredible! As an engineer and a rider, I loved how cleanly and clearly this explains the tyre use and firing order. Thanks for creating this

[tesmith]

This was absolutely excellent, you win this week's internet education award, KUDOS!!!

[jaredchampagne]

I have a cross plane r1, and its the best sounding and feeling engine I’ve ever experienced, I absolutely love the sound the bike makes, its such a head turner and it sounds like a v8.

[uNails]

I have absolutely zero questions! Incredibly comprehensive and beautifully illustrated. This is a master class in how to break down a complex engineering problem and explain it in common language. Brilliantly done.

[nicozimmermann]

this was a extremely well made explanation. i never though about how powerdelivery to the tire is actually in pulse form but it makes so much sense. fascinating.

[bostjanerjavec]

This was the most educational video, I've seen lately (allmost ever). Finaly explains why (at the time) Ducatis were faster than Yamahas, although Yamahas had more HP (L2 vs. inline 4).

[Dadnatron]

You do such a great job of explaining these engineering concepts. High enough level to impart real knowledge, but in a manner low enough for a non-engineer to understand. Thank you very much.