Honda Power Unit Hardware & Software

[godlameroso]

The regulations state max compression ratio is 18:1 they're suggesting that they need to be able to run at that ratio to catch up?

[ncassi22]

The regulations state max compression ratio is 18:1 they're suggesting that they need to be able to run at that ratio to catch up?

Pistons should look rather interesting given an 18:1 CR with a very stroke. Very 'domey'? I doubt it and the head would be parallel like in diesels mainly because of the limited space for both prechamber/injector/plug and valve. Also based on whats been discussed here regarding the 'weird'(radial?) valve layout.

[HPD]

The same article also says:

Compression ratio 18.0 and high pressure injector

I remember about the cylinder compression ratio 18.0 that it was only added in 2016. It was supposed to be an additional rule under the Mercedes standard of those days. In gasoline turbo engines, it is usual to set the compression ratio to a lower value in order to prevent knocking (ignition without permission), but it seems to be different in the world of F1.

This high compression ratio is realized by blowing fuel mist like with 500 bar high pressure injector and lowering cylinder temperature by heat of vaporization.
http://f1-motorsports-gp.com/%E3%83%AC% ... egulation/

[Tommy Cookers]

lowering cylinder temperature by heat of vapourisation ?

the cooling effect of this is of course also diluted by the great excess of air so is less than usual
the NA engines were probably evaporating more fuel in the cylinders and had far less air to cool

all engines evaporate their fuel in their air somewhere and a lot of that will be in-cylinder
with a race NA engine evaporation pre-cylinder is counterproductive as it displaces air eg the 2.4 litre V8 would act as 2.3 or so

[gruntguru]

I agree. If 18:1 is being achieved it is mainly due to rapid combustion, stratification and ultra-lean mixture.
- Little time for heating of the end gas
- Very dilute (lean) end gas (possibly just air)
- low combustion temperatures

[roon]

18:1 may also be about trying to limit Atkinson-cycle development and/or valve overlap. It would also limit the range of movement for any variable geometry features within the combustion chamber.

How problematic is knock & detonation when the air-fuel charge is so lean and stratified? If the fuel does ignite prematurely it will be localized. I suspect detonation can be incorporated into regular operation and be rendered irrelevant. Maintaining separation of the fuel-air charge from non-combustion air (I'll call this NCA; maybe there's another established term) is the trick. NCA or delineated CC volumes will absorb/withstand detonation, ignition and pre-ignition of the fuel-air charge. Timing, inclusion or disclusion of those events is important but only for performance, not durability or catastrophic failure of the componentry (my guess).

An aside--oil injection may have been about using oil spray to cool CC surfaces directly and not about burning oil. Using fuel to cool is perhaps not the best use of it within this formula and would go against maintaining stratification.

[godlameroso]

At 18:1 spark ignition becomes almost exclusively about dealing with detonation. Unless you have some tricks up your sleeve, your main concern will be knock, which I believe all these engines deal with.

So the hardware and the software simply have to have more fidelity to operate closer to the edge. That's where the relative advantage comes in.

Perhaps the electrical systems are creeping up to the 1,000 volt limit as well.

Edit:
Are you suggesting a weird hybrid otto/atkinson 18:1 engine that under atkinson operates like a 15:1 or 14:1?

[PlatinumZealot]

18:1 is high, but not that far from the old 16 to 1 of the NA engines. With direct injection it shouldn't be too challenging I presume.

[63l8qrrfy6]

Dont think any of the NAs reached 15.
Also is it really worth chasing too high a CR considering TE starts to level out around 14-16 ?

I just don't see the ugly deep valve pocket pistons they had on NA handling current pressures and temperatures.

Edit: just checked - toyota v8 was 13.6, cossie v8 was 13.3. I have honda and bmw numbers somewhere but I'm too lazy.

[wuzak]

18:1 is high, but not that far from the old 16 to 1 of the NA engines. With direct injection it shouldn't be too challenging I presume.

18:1 with air that has already been compressed to between 3 and 4 bar.

[GhostF1]

18:1 is high, but not that far from the old 16 to 1 of the NA engines. With direct injection it shouldn't be too challenging I presume.

18:1 with air that has already been compressed to between 3 and 4 bar.

That's the main thing. Having a compression ratio that high is one thing, but combine that with intake pressure levels 4-5 times atmospheric, it makes you start to marvel at these creations.

[godlameroso]

What if using a pent roof combustion chamber isn't the best solution? But you arrive at this conclusion because you can't accurately model the type of combustion chamber geometry you want to use? Or that it's taking too long in order to learn and implement knowledge. But what if you design a cylinder head that uses a very flat valve angle, which is easier to model, true you sacrifice some efficiency, but it's easier to develop. You evolve your models, you try them with new combustion chamber designs. Eventually you learn enough that your meshes are fine enough and your simulations are so good that you can predict and develop with more complex combustion chamber shapes.

Would in part explain a tall cylinder head.

[gruntguru]

18:1 is high, but not that far from the old 16 to 1 of the NA engines. With direct injection it shouldn't be too challenging I presume.

18:1 with air that has already been compressed to between 3 and 4 bar.

Yes, for isentropic compression that would produce a compression pressure > 220 bar! (and temperature > 2000*C)

[dren]

18:1 is high, but not that far from the old 16 to 1 of the NA engines. With direct injection it shouldn't be too challenging I presume.

18:1 with air that has already been compressed to between 3 and 4 bar.

Yes, for isentropic compression that would produce a compression pressure > 220 bar! (and temperature > 2000*C)

And that's before ignition!

As for oil cooling that someone pointed out, wouldn't they spray the back side of the pistons already for lubrication and cooling?

[roon]

What if using a pent roof combustion chamber isn't the best solution? But you arrive at this conclusion because you can't accurately model the type of combustion chamber geometry you want to use? Or that it's taking too long in order to learn and implement knowledge. But what if you design a cylinder head that uses a very flat valve angle, which is easier to model, true you sacrifice some efficiency, but it's easier to develop. You evolve your models, you try them with new combustion chamber designs. Eventually you learn enough that your meshes are fine enough and your simulations are so good that you can predict and develop with more complex combustion chamber shapes.

Would in part explain a tall cylinder head.

All the photos I've seen suggest close camshaft spacing, which may imply what you're implying.