Honda Power Unit Hardware & Software

[Bandit1216]

.......But you are right, a forced induction/turbo engine does not need as extreme a valve lift as an NA engine and also much less need of valve overlap to avoid turbo boost going right through the exhaust. It is valve overlap that mostly necessitates valve pockets in pistons. In turn valve pockets in pistons is driven by the need to keep combustion chamber space above the pistons as small as possible to obtain high compression ratios.

Gilles Simon wrote that there would be a conflict between adequate valve size/lift and adequate compression ratio
and boost isn't free in a turbocompound engine - pressure lost at the valves is work recovery denied to the turbine

we might also think that overlap would be needed to cool the exhaust valves
the exhaust mass-specific heat is unusually low but it's volume-specific heat is unusually high
and in these engines overlap loses no fuel and most of its flow work is recovered

could there even be some weird valve timing to use exhaust backpressure variations ?
sometimes overlap overscavenge and at other times underscavenge for internal exhaust retention and super-lean mixture

That's a good question, I often wonder if teams are using valve timing as a way to get away with high geometric compression ratios? A sort of Miller Atkinson combination, I wonder how much experimentation they've done with with valve timing. If it's gotten to the point that they're squeezing water out of stones, or if it's still a soggy sponge dripping with potential.

How do you mean "get away" with a high geometric compression ration? What would be the benefit?

[henry]

.....

How do you mean "get away" with a high geometric compression ration? What would be the benefit?

If you have Late Inlet Valve Closing , after BDC, the effective compression ratio is lowered with some of the cylinder contents returning to the inlet tract.

A possible scenario would be that the injector, sited between the exhaust valves, is aimed across the spark plug/prechamber at the back of the hot inlet valves and fires just after BDC on the compression stroke. A rich mixture is forced out of of the main chamber into the inlet tract where it has time to mix into a more homogeneous mixture during the next 500° or so. Meanwhile the rich mixture around the prechamber is forced into it by the compression and the main chamber mixture is compressed and then ignited in the normal way. This would emulate, to some extent, port injection for the main

There would be a need for low or no overlap to stop the premix going straight down the exhaust, albeit there is a turbine there to make use of the fuel that does so.

Too fanciful?

[Bandit1216]

.....

How do you mean "get away" with a high geometric compression ration? What would be the benefit?

If you have Late Inlet Valve Closing , after BDC, the effective compression ratio is lowered with some of the cylinder contents returning to the inlet tract.

A possible scenario would be that the injector, sited between the exhaust valves, is aimed across the spark plug/prechamber at the back of the hot inlet valves and fires just after BDC on the compression stroke. A rich mixture is forced out of of the main chamber into the inlet tract where it has time to mix into a more homogeneous mixture during the next 500° or so. Meanwhile the rich mixture around the prechamber is forced into it by the compression and the main chamber mixture is compressed and then ignited in the normal way. This would emulate, to some extent, port injection for the main

There would be a need for low or no overlap to stop the premix going straight down the exhaust, albeit there is a turbine there to make use of the fuel that does so.

Too fanciful?

But that would require 2 injectors, which is not allowed.

[henry]

.....

How do you mean "get away" with a high geometric compression ration? What would be the benefit?

If you have Late Inlet Valve Closing , after BDC, the effective compression ratio is lowered with some of the cylinder contents returning to the inlet tract.

A possible scenario would be that the injector, sited between the exhaust valves, is aimed across the spark plug/prechamber at the back of the hot inlet valves and fires just after BDC on the compression stroke. A rich mixture is forced out of of the main chamber into the inlet tract where it has time to mix into a more homogeneous mixture during the next 500° or so. Meanwhile the rich mixture around the prechamber is forced into it by the compression and the main chamber mixture is compressed and then ignited in the normal way. This would emulate, to some extent, port injection for the main

There would be a need for low or no overlap to stop the premix going straight down the exhaust, albeit there is a turbine there to make use of the fuel that does so.

Too fanciful?

But that would require 2 injectors, which is not allowed.

If that’s how it reads I apologise for not being clearer.

I mean ONE injector that injects simultaneously into the main chamber, prechamber, and the inlet ports, just after BDC on the compression stroke.

[Tommy Cookers]

If there is a man that knows that turbocompounding is not allowed in formula 1 that will be Giles Simon.

the F1 PU is compounded whenever power is being recovered from the turbine and the MGU-K is motoring

[Bandit1216]

If you have Late Inlet Valve Closing , after BDC, the effective compression ratio is lowered with some of the cylinder contents returning to the inlet tract.

A possible scenario would be that the injector, sited between the exhaust valves, is aimed across the spark plug/prechamber at the back of the hot inlet valves and fires just after BDC on the compression stroke. A rich mixture is forced out of of the main chamber into the inlet tract where it has time to mix into a more homogeneous mixture during the next 500° or so. Meanwhile the rich mixture around the prechamber is forced into it by the compression and the main chamber mixture is compressed and then ignited in the normal way. This would emulate, to some extent, port injection for the main

There would be a need for low or no overlap to stop the premix going straight down the exhaust, albeit there is a turbine there to make use of the fuel that does so.

Too fanciful?

But that would require 2 injectors, which is not allowed.

If that’s how it reads I apologise for not being clearer.

I mean ONE injector that injects simultaneously into the main chamber, prechamber, and the inlet ports, just after BDC on the compression stroke.

Far fetched IMO, but possible.

[saviour stivala]

If there is a man that knows that turbocompounding is not allowed in formula 1 that will be Giles Simon.

the F1 PU is compounded whenever power is being recovered from the turbine and the MGU-K is motoring

Tommy. You are correct. my mind was racing on some different line.

[Brake Horse Power]

The late inlet valve closing is the principle as used in the Mazda skyactive engines?

[Bandit1216]

Hi all. Last pages are more general pu talk than Honda. but oké.

I think valve timing and overlap will be quite conservative for a 12000 rpm engine, because it's a efficiency race, and not a power race anymore.

And I want to ask again: Is knock really an issue? I think they will be running lambda as lean as 2, and I understand that at a certain level it's too lean for detonation. I don't knock how that works though, see this picture.

[godlameroso]

Knocking in these engines is the limiting issue. These engines operate smack dab in the knock and high NOx zone on that graph.

[saviour stivala]

Knocking in these engines is the limiting issue. These engines operate smack dab in the knock and high NOx zone on that graph.

Very well said and expressed. Further back I described the design, running and control of the present PU (ENGINE) as a game of how not to burn your fingers. (one knock in one of the cylinders and a 2800 Euro build-in pressure sensor is broken, and then there is no sensor and after that there is no engine).

[Bandit1216]

Knocking in these engines is the limiting issue. These engines operate smack dab in the knock and high NOx zone on that graph.

Oké. But why do they do that when efficiency is best at lambda 2. Think the graph is not completely representative for gasoline as this is LNG, but it won't be much different, or would it?

One might think that big maritime engines are a lot different and even "simple", but lean burn and 3 bar turbo pressure is quite common in the business. Newest engine has 5 bar and sequential turbocharging and is 51% efficient. For maritime engines, efficiency has always been important, and easier to achieve because they mostly run close to full power, unlike car engines, but like nowadays F1.

I think there are quite some parallels to find.

[godlameroso]

Knocking in these engines is the limiting issue. These engines operate smack dab in the knock and high NOx zone on that graph.

Oké. But why do they do that when efficiency is best at lambda 2. Think the graph is not completely representative for gasoline as this is LNG, but it won't be much different, or would it?

One might think that big maritime engines are a lot different and even "simple", but lean burn and 3 bar turbo pressure is quite common in the business. Newest engine has 5 bar and sequential turbocharging and is 51% efficient. For maritime engines, efficiency has always been important, and easier to achieve because they mostly run close to full power, unlike car engines, but like nowadays F1.

I think there are quite some parallels to find.

Efficiency is best ~lambda 1.2-1.4, and max power is near stoich for these engines. Power comes from heating the compressed air crammed in the CC, the most expansion of that compressed air comes from a high temperature delta. High combustion temps are what causes these engines to produce NOx.

[63l8qrrfy6]

Knocking in these engines is the limiting issue. These engines operate smack dab in the knock and high NOx zone on that graph.

Oké. But why do they do that when efficiency is best at lambda 2. Think the graph is not completely representative for gasoline as this is LNG, but it won't be much different, or would it?

One might think that big maritime engines are a lot different and even "simple", but lean burn and 3 bar turbo pressure is quite common in the business. Newest engine has 5 bar and sequential turbocharging and is 51% efficient. For maritime engines, efficiency has always been important, and easier to achieve because they mostly run close to full power, unlike car engines, but like nowadays F1.

I think there are quite some parallels to find.

Efficiency is best ~lambda 1.2-1.4, and max power is near stoich for these engines. Power comes from heating the compressed air crammed in the CC, the most expansion of that compressed air comes from a high temperature delta. High combustion temps are what causes these engines to produce NOx.

Peak power is at peak TE. So 'best efficiency' and max power can't be at different AFR.

[saviour stivala]

Knocking in these engines is the limiting issue. These engines operate smack dab in the knock and high NOx zone on that graph.

Oké. But why do they do that when efficiency is best at lambda 2. Think the graph is not completely representative for gasoline as this is LNG, but it won't be much different, or would it?

One might think that big maritime engines are a lot different and even "simple", but lean burn and 3 bar turbo pressure is quite common in the business. Newest engine has 5 bar and sequential turbocharging and is 51% efficient. For maritime engines, efficiency has always been important, and easier to achieve because they mostly run close to full power, unlike car engines, but like nowadays F1.

I think there are quite some parallels to find.

How can a graph representing an engine designed to run at a maximum of 750RPM be representative of an engine designed to run at a max power speed of 10500RPM?.