2014 Engine yin yang

[Holm86]

Today on the contrary you can add as much air as you want, by using little amount or a lot you can run rich or lean but the calorific potential, the energy introduced, is always the same.

This is what Marmorini said. Thats why i said it wouldt mean anything power wise. Though I've allways heard that you achieve most power running slightly rich.

And after seeing that chart I will still hold my opinion that they will run the engines rich. If it both gives you the most amount of power and runs cooler its a win-win situation.

[xpensive]

Don't you need a certain amount of oxygen to burn a given mass of fuel, isn't that the idea with turbos and intercoolers?

[Tommy Cookers]

@ Holm
at 27.7 gm/sec of fuel and a rich mixture there is not enough air to burn all 27.7 gm that arrives each second
at 27.7 gm/sec of fuel and a stoichiometric or lean mixture there is enough air to burn all 27.7 gm fuel each second

so at this 2014 fixed fuel rate a rich mixture will yield less heat energy than a stoichiometric or a lean mixture
ie in 2014 rich mixture = less power

rich mixture's contribution to power is possible faster and more consistent combustion
neither relevant at 10500 rpm in small cylinders, with fuel ideally conditioned for combustion by v high pressure DI
or higher CR or boost using high-aromatic fuels (these won't be used in 2014 as their specific energy is much inferior)

Mr IMO

[motobaleno]

@ Holm
at 27.7 gm/sec of fuel and a rich mixture there is not enough air to burn all 27.7 gm that arrives each second
at 27.7 gm/sec of fuel and a stoichiometric or lean mixture there is enough air to burn all 27.7 gm fuel each second

so at this 2014 fixed fuel rate a rich mixture will yield less heat energy than a stoichiometric or a lean mixture
ie in 2014 rich mixture = less power

rich mixture's contribution to power is possible faster and more consistent combustion
neither relevant at 10500 rpm in small cylinders, with fuel ideally conditioned for combustion by v high pressure DI
or higher CR or boost using high-aromatic fuels (these won't be used in 2014 as their specific energy is much inferior)

Mr IMO

this time I definitely agree with you. in a fuel limited formula you have to run stechiometric o lean to achieve the maximum possible power
the graph above is true but someone is not interpreting it right
the graph simply says that if you use 1 of fuel and 14.7 of air you get lets say 100 of power (the number is not important) then if you use 1.1 of fuel and 14.7 of air you get 103: that's running rich. BUT if you use again 1.1 of fuel and 16.17 of air (again stechiometric) you get 105!
so, IF you are air restricted (and if you don't have any fuel limit you are ALWAYS air restricted) is better to run rich but if you are fuel restricted is better to run stechiometric (or lean that means LOCALLY stechiometric inside the combustion chamber but that's rather complicated to explain)

[Holm86]

@ Holm
at 27.7 gm/sec of fuel and a rich mixture there is not enough air to burn all 27.7 gm that arrives each second
at 27.7 gm/sec of fuel and a stoichiometric or lean mixture there is enough air to burn all 27.7 gm fuel each second

so at this 2014 fixed fuel rate a rich mixture will yield less heat energy than a stoichiometric or a lean mixture
ie in 2014 rich mixture = less power

rich mixture's contribution to power is possible faster and more consistent combustion
neither relevant at 10500 rpm in small cylinders, with fuel ideally conditioned for combustion by v high pressure DI
or higher CR or boost using high-aromatic fuels (these won't be used in 2014 as their specific energy is much inferior)

Mr IMO

How can a rich mixture in any cases achive more power if it werent able to burn all the fuel?

[motobaleno]

How can a rich mixture in any cases achive more power if it werent able to burn all the fuel?

beacause theory and reality are different.
inside the combustion chamber is very difficult in such small time to achieve a perfect uniform mixture air fuel so if you run stechiometric maybe there are some regions where you actually are lean and you don't use all the air you could (remember: if you don't have fuel limits you are ALWAYS air limited) so, if you run a bit rich you are sure to be at least stechiometric everywhere inside the combustion chambers if the air fuel mixture is not perfect uniform

[Holm86]

How can a rich mixture in any cases achive more power if it werent able to burn all the fuel?

beacause theory and reality are different.
inside the combustion chamber is very difficult in such small time to achieve a perfect uniform mixture air fuel so if you run stechiometric maybe there are some regions where you actually are lean and you don't use all the air you could (remember: if you don't have fuel limits you are ALWAYS air limited) so, if you run a bit rich you are sure to be at least stechiometric everywhere inside the combustion chambers if the air fuel mixture is not perfect uniform

Well the lambda sensor sits in the exhaust pipe. It measures the amount of oxygen. And if that says lambda 1.0 then you have had a stoichiometric combustion. So your idea of a lean burn in some places of the combustion chamber doesnt hold up. If there would be excess air the lambda sensor would pick up on that.

I dont think the engines will run stoichiometric and not lean at all. The temperatures would be way to high in a boosted race engine. And probably introduce knock.

[Abarth]

[...]Well the lambda sensor sits in the exhaust pipe. It measures the amount of oxygen. And if that says lambda 1.0 then you have had a stoichiometric combustion. So your idea of a lean burn in some places of the combustion chamber doesnt hold up. If there would be excess air the lambda sensor would pick up on that.[...]

No, motobaleno is right.

A Lambda sensor can not identify a combustion in a combustion chamber in which the mixture was not homogenically distributed. Mind you, this is one cycle, in which one you have zones of lean and zones of rich mixture, even if the mean ratio is stochiometric. What should a lambda sond measure in such a case, according to you?

And, motobaleno is correct in assessing that in a fuel restricted case, running rather on the lean side yields max. power.
OTOH, you are correct in that running lean (lambda >1) you run higher temperatures, which might have a negative impact on turbine and possibly exhaust valves.
But with todays materials, who knows...

[Holm86]

[...]Well the lambda sensor sits in the exhaust pipe. It measures the amount of oxygen. And if that says lambda 1.0 then you have had a stoichiometric combustion. So your idea of a lean burn in some places of the combustion chamber doesnt hold up. If there would be excess air the lambda sensor would pick up on that.[...]

No, motobaleno is right.

A Lambda sensor can not identify a combustion in a combustion chamber in which the mixture was not homogenically distributed. Mind you, this is one cycle, in which one you have zones of lean and zones of rich mixture, even if the mean ratio is stochiometric. What should a lambda sond measure in such a case, according to you?

And, motobaleno is correct in assessing that in a fuel restricted case, running rather on the lean side yields max. power.
OTOH, you are correct in that running lean (lambda >1) you run higher temperatures, which might have a negative impact on turbine and possibly exhaust valves.
But with todays materials, who knows...

No a lambda sensor cant monitor a combustion in the chamber. But what motobaleno said was that you wouldnt use all the air that you could bechaust of this uneven combustion. But if there is excess air after the combustion then there will be excess air in the exhaust which the lamdba would pick up. And with DI you could have lambda sensors at all 6 exhaust outlets so you can regulate the lambda individually in each cylinder.

And again it doesnt matter if it is fuel or air restricted. Its a ratio between the two. So it would be the same.

[Phil]

This might not be the right thread to ask, but I hope I won't be flamed for putting it outthere, regardless:

From what I understand, the fuel for 2014 is limited - in other words, the fuel being limited also means there is some limit on power at a practical level, since you don't want to burn too much fuel in order to make it through the grandprix. Now, is the fuel amount the only limitation or is there some kind of cap on fuel-flow as well?

The reason for my asking is; the cars start with 100kg+ of fuel for the GP. At the start, the cars are heavier, thus require more fuel for power,than at the end of a GP when the cars are lighter. So, I guess I am wondering if there is some thought being put into engines that deliever more power towards the end of a GP when the cars become lighter and the cars use less fuel relative to the weight. Would this even make sense?

100kg of fuel distributed over a GP is tricky when the fuel loads change accoarding to the weight the cars carry around the track. It'd be also interesting to know if some thought into this problem has went into the 2010 season when they effectively switched to banned-refueling races with effectively frozen engine tech (sans the mapping). Now, I get what I am questioning can to a large part be solved with different engine maps - but my point is, if you know you can run afford to run more power at a certain stage of a grandprix because you have more fuel at your disposal (relative speaking), it makes sense to build an engine to that requirement and then limit the power during the other stages by mapping in order to get through the fuel/GP limit.

Any thoughts?

[Holm86]

This might not be the right thread to ask, but I hope I won't be flamed for putting it outthere, regardless:

From what I understand, the fuel for 2014 is limited - in other words, the fuel being limited also means there is some limit on power at a practical level, since you don't want to burn too much fuel in order to make it through the grandprix. Now, is the fuel amount the only limitation or is there some kind of cap on fuel-flow as well?

The reason for my asking is; the cars start with 100kg+ of fuel for the GP. At the start, the cars are heavier, thus require more fuel for power,than at the end of a GP when the cars are lighter. So, I guess I am wondering if there is some thought being put into engines that deliever more power towards the end of a GP when the cars become lighter and the cars use less fuel relative to the weight. Would this even make sense?

100kg of fuel distributed over a GP is tricky when the fuel loads change accoarding to the weight the cars carry around the track. It'd be also interesting to know if some thought into this problem has went into the 2010 season when they effectively switched to banned-refueling races with effectively frozen engine tech (sans the mapping). Now, I get what I am questioning can to a large part be solved with different engine maps - but my point is, if you know you can run afford to run more power at a certain stage of a grandprix because you have more fuel at your disposal (relative speaking), it makes sense to build an engine to that requirement and then limit the power during the other stages by mapping in order to get through the fuel/GP limit.

Any thoughts?

There is a fuel flow limit of 100 kg/h. And this a max flow limit. Not a fuel average.

In here we like to say 27.77 g/s instead of 100 kg/h.

[Abarth]

[...]And again it doesnt matter if it is fuel or air restricted. Its a ratio between the two. So it would be the same.

It is a ratio, but it does matter.

I'll try to explain with another example what motobaleno tried to explain.

Again, it is an example!

At Lambda = 0.85 = 255 g/kWh (=max. power)
At Lambda = 1.0 = 240 g/kWh
At Lambda = 1.15 = 230 g /kWh (=minimum spec. consumption)

Lambda is, in this case, not regulated with the amount of injected fuel, but with amout of air charged (which means that you have to rise boost pressure, and thus for leaner operation, consumption might not go down as much as in an air restricted engine, due to higher pumping losses).

OK, lets calculate the power the engine theoretically is able to produce if not air restricted:

Rich: 100 kg/h / 0.255 kg/kWh = 392 kW = 533 HP
Stochiometric: 100 kg/h / 0.240 kg/kWh = 417 kW = 567 HP
Lean: 100 kg/h / 0.230 kg/kWh = 435 kW = 591 HP.

Less specific consumption in a fuel restricted engine always leads to higher power output.
Whether these engines will be able running lean, I don't know.

[Tommy Cookers]

@ Holm
rich mixture's contribution to power is possible faster and more consistent combustion
neither relevant at 10500 rpm in small cylinders, with fuel ideally conditioned for combustion by v high pressure DI
or higher CR or boost using high-aromatic fuels (these won't be used in 2014 as their specific energy is much inferior)

How can a rich mixture in any cases achieve more power if it werent able to burn all the fuel?

in addition to the reasons already given as above
in 99.99999999% of cases the engine is air limited eg in current F1 by having 2400cc @ 18000 rpm
a rich mixture means more fuel than can all be burnt by that limited air
this surplus fuel means that notionally all the air will be used
because all the air ie more air is being used the heat liberated with a rich mixture will be more than with eg a stoichiometric one
with eg a stoichiometric mixture not quite all the air will be used (and not quite all the fuel)
so rich mixture will here give better power (but much worse bsfc, because some fuel is simply being thrown away unused)

current F1 certainly has more consistent combustion enabled by rich mixture use
so uses more/all of its fixed air supply when run rich, so has greater maximum power
the price is disproportionate fuel consumption
but they run some or much of every race in rich mixture

[Phil]

There is a fuel flow limit of 100 kg/h. And this a max flow limit. Not a fuel average.

In here we like to say 27.77 g/s instead of 100 kg/h.

Thanks. Is this the common way / metric to formulate the fuel flow limit (kg per hour) or can this be used to exceed the limit as long as the average stays within the limit [of the hour]? I.e. Could I use 40g/s at times as long as the average stays at no higher 27.77 g/s over the period of an hour?

[Holm86]

There is a fuel flow limit of 100 kg/h. And this a max flow limit. Not a fuel average.

In here we like to say 27.77 g/s instead of 100 kg/h.

Thanks. Is this the common way / metric to formulate the fuel flow limit (kg per hour) or can this be used to exceed the limit as long as the average stays within the limit [of the hour]? I.e. Could I use 40g/s at times as long as the average stays at no higher 27.77 g/s over the period of an hour?

As I said its the maximum fuel flow. The flow cannot exceed 27.77 g/s. Its not an average.