2014-2020 Formula One 1.6l V6 turbo engine formula

[Tommy Cookers]

underscavenge (internal EGR) will occur any time the exhaust pressure is raised by suitably generation-loading the MGU-H
this I have often suggested will be made to happen at sustained rpms over 10500
(because it's better than the alternatives of further increasing AFR or lowering (how exactly?) the boost)
and could be made to happen at other times ....

but people really should decide whether there's ....
this systematic underscavenge/internal EGR or the conventional exhaust valve cooling by fresh air and valve overlap
they can't have both

the EVs don't need cooling like a high power aircooled engine's because the seats are closer on the thermal gradient to coolant
and anyway the exhaust gas is cooler because it's very heavily cut with unused air

though presumably there is some combustion in the exhaust gas whether internally recirculated or upstream of the turbine
at max AFRs of prechamber SI engines likely combustion efficiency is 'only' 95% - counting or discounting exhaust combustion ?

[roon]

Summary of some of the more interesting additions to the 2018 technical regulations. Revisions in pink.

[1158]

The change to 5.10.5 is very interesting. Is that implying it would have been technically legal to funnel off some of the fuel destined for the return line back into the main line upstream of the flow meter?

[roon]

Why "store and recycle" fuel at all? I like 1.30, personally. Previously there wasn't a definition for combustion chamber.

[63l8qrrfy6]

Why "store and recycle" fuel at all? I like 1.30, personally. Previously there wasn't a definition for combustion chamber.

Because you could flow 100 kg/h at part throttle, store it after the meter then burn in excess of 100 kg/h when needed ?

[Zynerji]

Why "store and recycle" fuel at all? I like 1.30, personally. Previously there wasn't a definition for combustion chamber.

Because you could flow 100 kg/h at part throttle, store it after the meter then burn in excess of 100 kg/h when needed ?

Sounds obvious?

[1158]

Why "store and recycle" fuel at all? I like 1.30, personally. Previously there wasn't a definition for combustion chamber.

Because you could flow 100 kg/h at part throttle, store it after the meter then burn in excess of 100 kg/h when needed ?

That's what I was thinking. I think the wording before outlawed storing fuel after the flow meter but didn't say anything about recycling. In theory a team could have run a return line back to the tank, but not into the tank, and then back to rail. If the fuel is flowing it isn't being stored, at least in my eyes, and that would allow them more fuel flow than the 100 kg/h rate for short periods of time.

You're robbing Peter to pay Paul given the total fuel limit, but if you can use it for an advantage in Q and then for a few laps early in the race, you can dial back your consumption later in the race to make up for the higher usage previously.

[roon]

That's a big loophole that was closed, if so. I wonder if the FIA saw high-yet-legal flow rates at odd times. During idle, braking, starting grid, etc.

You're robbing Peter to pay Paul given the total fuel limit, but if you can use it for an advantage in Q and then for a few laps early in the race, you can dial back your consumption later in the race to make up for the higher usage previously.

There wouldn't necessarily be a compromise. Under a fuel-restriction formula, a way to maximize power other than combustion & drivetrain efficiency, would be to flow the maximum amount of fuel permitted for as long as possible.

As mentioned, you maximize fuel flow during idle, pit stops, starting formation, formation lap, and caution laps; storing the unused fuel in a buffer tank, which could simply be large diameter fuel rails (green box below):



Never once would the flow limit be exceeded. The flow limit is not defined as what enters singular cylinders i.e. 100kg/hr/6. It's simply 100kg/hr. 100kg/hr/6 per-cylinder may already be exceeded during cylinder cutting. How the fuel was subdivided amongst the cylinders after the flow meter was never defined. This remains.

[PlatinumZealot]

These issues were discussed back in 2014 and 2015.
We had theories of Honda using a "big bang" injection pattern in which three cylinders alone fire, and with twice the fuel that they would get if 6 cylinders were firing - but it was just like any other combination of firing patterns in the end.. a bit of efficiency compromises here and there and average fuel flow is still 100kg/hr no matter how you slice it.

[gruntguru]

There is little doubt that the teams were storing and releasing metered fuel by varying the fuel pressure in a section of the fuel system that was "springy" ie its volume varied significantly with pressure. This could even be an obvious "accumulator" type device - something used frequently in fuel injection systems.

[roon]

1.29 implies that a portion of the charge air was not being used for combustion.

Guesses:

• Significant valve overlap in order to maximize heat dilution, a:f ratio, and mass flow to the turbine. A cooler but more voluminous exhaust flow for the turbine may have been advantageous. Claims of extremely high a:f ratios could be explained in this way. The combustion chamber sees a relatively rich a:f ratio; the cylinder at valve overlap and the exhaust manifold see a much leaner ratio as extra charge air is added. Ideally uncooled charge air would be used for the dilution mix, and you only pass combustion-chamber-charge, not dilution-charge, through the intercooler.
• Vortex tube to bleed off separated hot air, as Zynerji suggested.

1.30 may imply an unusual combustion chamber design. Why else define what is common knowledge?

Guesses:

• A combustion chamber was used which did not use poppet valves as the, or as the main form of, control.
• Combustion was occurring elsewhere.

[dren]

Doesn't this sound familiar: https://www.autoblog.com/2018/01/25/maz ... explained/

The combustion chamber and injection pulse is designed to create a swirling effect, like a little hurricane — complete with an "eye." Mazda discovered that it could make the eye a little richer than the rest of the mixture by injecting some fuel later, while keeping things overall too cool and underpressurized to actually self-combust.

Igniting that small enriched portion in the "eye" creates enough extra heat and pressure in the rest of the combustion chamber to ignite the leaner mixture around it. The result is a controlled and very quick burn of an extremely lean mixture overall. It's the puzzle piece that makes SPCCI work at around 80 percent of the operating range of the engine in normal circumstances.

[roon]

In that video I see: delayed intake valve opening, a central injector and a spark plug in between the intake valves. Using the fuel spray to help induce vorticity is interesting. I don't know why air is shown flowing inside the intake runner while the intake valve is closed.

[1158]

1.30 may imply an unusual combustion chamber design. Why else define what is common knowledge?

Guesses:

• A combustion chamber was used which did not use poppet valves as the, or as the main form of, control.
• Combustion was occurring elsewhere.
• What I would call 'stratified compression' controlled by piston movement and geometry. One portion of the cylinder undergoes relatively low compression. Another portion undergoes higher compression. This may also explain the compression ratio limit rule.

1.30 still wouldn't prohibit combustion outside the CC. It would need to say ALL combustion to prevent combustion from occurring somewhere else.

Your idea of different compression ratios within the cylinder is interesting. Perhaps an asymmetric piston crown with some sort of divider between the 2 areas? As the compression increases on the compression stroke the combustion event on the higher CR side of the piston begins, forcing jets through the divider and igniting the other side? Could this work? The divider might become a hotspot though. I know there was talk of Ferrari having intricate pistion crown designs but I never heard any ideas as to what it might look like. I don't remember having read anyone suggest this idea (though it certainly could have been suggested already).


The addition of fuel in front of injector is also interesting. Does that mean you could have an air injector or maybe a water injector? Note 5.14.2 would not necessarily outlaw injecting water directly into the CC, the regs state only fuel can be injected it the air destined for combustion. Although since fuel can't be injected upstream or downstream of the CC I guess that implies air in the CC is the air destined for combustion. Any benefit to injecting water after the combustion event during the exhaust stroke?

[roon]

Continuing upon using valve overlap to explain 1.29, we may also consider 5.3.6, the latter defined as:

No cylinder of the engine may have a geometric compression ratio higher than 18.0.

'Cylinder' in the regs, as I read them, seems to mean the swept volume of the piston inside a cylinder. This ignores combustion chamber volume.

Suppose the intake and exhaust valves are open through the intake stroke and the first half of the compression stroke. A geometric compression ratio of the 36 would be required to achieve an effective compression ratio of 18.

If air dilution is being achieved through valve overlap and Atkinson-type partial-stroke compression, these two rules would be a way to limit that.

The efficiency formula and high a:f ratios should imply that there will always be a portion of compressor charge inside the combustion chamber which is not being used for combustion. Oxygen sensors in the exhaust should reveal that such a rule is always being transgressed.

Although since fuel can't be injected upstream or downstream of the CC I guess that implies air in the CC is the air destined for combustion. Any benefit to injecting water after the combustion event during the exhaust stroke?

An interesting idea, adding mass and steam pressure to the exhaust flow. Another way to transfer more work to the turbine, a pseudo sixth-stroke. But likely precluded by:

5.8.1 With the exception of incidental leakage through joints (either into or out of the system) and power unit breather fluids, all and only the fluids entering the compressor inlet and fuel injectors must exit from the engine exhaust system.

This limits a water injector to only be placed pre-compressor. And 1.29 prevents passing compressor charge air, water-laden or not, from entering the exhaust because it is was not used for combustion.

A couple more 2018 additions I missed before:

5.1.11 An insert within a PU component is a minimal, non-dismountable part whose function is solely to locally support a function of this component. The total volume of inserts within the component cannot be more than 10% of the total volume of the component.
5.1.12 All power unit breather fluids may only vent to atmosphere and must pass through an orifice which is positioned rearward of the rear axle centre line and less than 400mm above the reference plane and less than 100mm from the car centre plane. No breather fluids may re-enter the power unit.

5.1.12 is yet another oil ingestion reference. I count four so far. It replaces a now-omitted rule which had stated that all sump-breather gases must pass through the engine in order to prevent oil-spillage on track. A reversal of intent.

It would be interesting to know the history of the sump-breather-gas-ingestion-for-safety rule. Was it suggested by those with ulterior motives, or was it subverted after-the-fact?