2022 Sepang MotoGP Test

Since the amount of fuel is limited the only door open is efficiency. While with a street vehicle you can make the mixture richer and see black smoke (unburned fuel) coming from exhaust you cannot afford it in MotoGP. Rising compression ratio will better efficiency, this is why diesel engines get better fuel economy. Gasoline starts detonating when the ratio is too high for given fuel and it will destroy the engine. Making the cylinder smaller does allow for higher compression ratio, this is why adding more cylinders actually allows for more efficient engine. Making sure the vaporizing process ends exactly when compression cycle starts is important. Injectors must create fuel spray of particles of optimal size to ensure this. Vaporizing is endothermic process, cooling down the contents of cylinder is paramount for efficiency. This spray must fill the air inside of combustion chamber homogeneously, and this is the hard part. Developers use cleverly shaped combustion chambers to get closer to this goal. To add confusion when RPM gets higher all this must happen faster ... and when RPM goes down then it must slow down, too ...
All this is grasping at straws. But there is nothing else you can do.
If you ask me further developing of internal combustion engine is a waste of time and money. The effort is huge and the results are close to none.

Edit: Forgot about factors which affect fill ratio. This is where exhaust backpressure and other resonances come into play, plus valve timings. This area of development is about filling cylinders with greatest amount of air and avoiding any waste of unburned fuel.

So is inline 4 obsolete in GP?

Twins and V4s to rule?

Well, actually there is a lot of ways you can still improve a combustion engine. For example, designing a better valve opening/closing type instead of using the current way of opening like a drawer, which acts as a barrier for the flow, make they open/closing sliding. Also there is room for electronic camshafts together with electromagnetic slinding valves. And much more...

This talking about internal combustion engines having already reached maximum volumetric effiency is .........

MichaelBolton said:

Quartararo is not happy at all with the 2022 Yamaha apparently... would be so like them to have a horrid year by refusing to improve after winning the championship.

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I'm not surprised, it appears thy brought little to the Sepang test except for changed winglets.

Segfault said:

Refusing to improve? I wouldn't put it this way. There are theoretical limits, adding horsepower while getting closer to the limit is more expensive and the improvements get smaller. An ideal engine would use all energy contained in the fuel to power output. Such an engine would have no need for cooling, as no energy is wasted ... In the real world the max efficiency of an internal combustion engine is almost reached, there is not much left what can be done.

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When Honda have brought a new bike, Ducati new engines, exhausts and a front squat device when Yamaha brought...new fairings. I'd say that's a resistance or ignorance to improve.

The max efficiency an IC engine is not almost reached. The issue is the rules that stipulate a max bore of 81mm along with fuel restrictions

Mrpurple said:

How exactly can you add power to an inline four? I would assume its been at that limit for a while now and more weight would disturb the cornering ability.

An inline 5?? Ala Honda...

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You can easily add power to an inline 4. increase revs, remove the reverse rotating crank that requires multiple gears internally. Changes to bore/stroke that are limited by the current rules (current 81mm bore predicates your stroke to conform to the 1000cc, and with this current bore/stroke, you are limited to about 27m/sec piston speed).

These rules really split engineering into 2. Those who want max power, and those who want the correct engine character for handling, which is the route Yamaha have gone.

Mrpurple said:

So is inline 4 obsolete in GP?

Twins and V4s to rule?

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It depends. Suzuki use an inline 4 and have done since their return to MGP, when previously they used a V4.

You are confusing efficiency with horsepower per given displacement.

Larger bore main advantage is larger intake valves, which means more air at high RPM, which means you can add more fuel without wasting it. In the end you will get more HP, true. But this is conventional thinking, not necessarily valid for a MotoGP engine. Because MotoGP does not have this additional fuel ...

gui22a said:

Well, actually there is a lot of ways you can still improve a combustion engine. For example, designing a better valve opening/closing type instead of using the current way of opening like a drawer, which acts as a barrier for the flow, make they open/closing sliding. Also there is room for electronic camshafts together with electromagnetic slinding valves. And much more...

This talking about internal combustion engines having already reached maximum volumetric effiency is .........

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I'm suprised more companies aren't looking into 'free valve' technology. Not only from a racing standpoint but just as far as efficiency goes. I think Koen(insertwheelbarrowofletterhere) were claiming 40+% gain in horsepower and efficiency in an sr20. That's without getting into how you would no longer have to make a compromise with cam profiles etc.

Segfault said:

You are confusing efficiency with horsepower per given displacement.

Larger bore main advantage is larger intake valves, which means more air at high RPM, which means you can add more fuel without wasting it. In the end you will get more HP, true. But this is conventional thinking, not necessarily valid for a MotoGP engine. Because MotoGP does not have this additional fuel ...

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If I wasn't clear, I was talking about bore vs stroke and the relation to piston speed.

You are absolutely right, however that argument is invalid because of the 81mm bore rule. That in effect sets your stroke to 48.5mm to use the full 1000cc allowed by the rules. A larger bore allowing bigger intake valves will indeed allow more air at higher RPM but that is useless if you cannot rev higher due to piston speed limitations.

It's like the old 500's. More aggressive transfer port design allowed more and more power, but it also made the engines extremely peaky and with a very tight powerband, to the point you;d have to have something like a 15 speed gearbox to make it work. You get more power yes, but not useable.

My understanding of the 81mm/1000cc rule was to save costs and allow manufacturers to use the cylinder heads from the 800cc bikes. So 81mm is actually fairly narrow for a 1000cc engine.