Honda Power Unit Hardware & Software

[subcritical71]

because the technical rules stipulates a 'direct injection' as the system to be used.

This is the part I don't get. I've searched all instances of 'direct' and none apply to the fuel injector. What I do find is the following, none of which says it must be directly injected into the combustion chamber;

1.31 Fuel injector :
Any device or component that delivers fuel into an oxidiser.

5.10 Fuel systems :
5.10.1 The pressure of the fuel supplied to the fuel injectors may not exceed 500bar. Only approved parts may be used and the list of parts approved by the FIA, and the approval procedure, may be found in the Appendix to the Technical Regulations.
5.10.2 There may only be one fuel injector per cylinder and no fuel injectors are permitted upstream of the intake valves or downstream of the exhaust valves. Only approved parts may be used and the list of parts approved by the FIA, and the approval procedure, may be found in the Appendix to the Technical Regulations.

I can't seem to find the relevant 'direct injection' rule, can you tell me what paragraph of the rules specify it?

[dren]

A Honda engineer was quoted (not a journalist forming an opinion) about the use of a pre-chamber in the 2017 PU. He said it was difficult to balance the A/F ratio in the pre-chamber and the main chamber with the injector spray and air flow. He said you cannot get away from using pre-chamber ignition in the current PU formula when you want to raise combustion efficiency.

Perhaps the pre-chamber is part of the piston crown and open to air/fuel up until TDC when it encapsulates the top protruding spark plug?

My fancy paint skills:

[1158]

A Honda engineer was quoted (not a journalist forming an opinion) about the use of a pre-chamber in the 2017 PU. He said it was difficult to balance the A/F ratio in the pre-chamber and the main chamber with the injector spray and air flow. He said you cannot get away from using pre-chamber ignition in the current PU formula when you want to raise combustion efficiency.

Perhaps the pre-chamber is part of the piston crown and open to air/fuel up until TDC when it encapsulates the top protruding spark plug?

I suggested that a while back in the generic PU thread (at least I think it was in that thread)

[henry]

because the technical rules stipulates a 'direct injection' as the system to be used.

This is the part I don't get. I've searched all instances of 'direct' and none apply to the fuel injector. What I do find is the following, none of which says it must be directly injected into the combustion chamber;

1.31 Fuel injector :
Any device or component that delivers fuel into an oxidiser.

5.10 Fuel systems :
5.10.1 The pressure of the fuel supplied to the fuel injectors may not exceed 500bar. Only approved parts may be used and the list of parts approved by the FIA, and the approval procedure, may be found in the Appendix to the Technical Regulations.
5.10.2 There may only be one fuel injector per cylinder and no fuel injectors are permitted upstream of the intake valves or downstream of the exhaust valves. Only approved parts may be used and the list of parts approved by the FIA, and the approval procedure, may be found in the Appendix to the Technical Regulations.

I can't seem to find the relevant 'direct injection' rule, can you tell me what paragraph of the rules specify it?

That’s a change for 2019. The 2018 regs say this:

5.10.2 There may only be one direct injector per cylinder and no injectors are permitted upstream of the intake valves or downstream of the exhaust valves. Only approved parts may be used and the list of parts approved by the FIA, and the approval procedure, may be found in the Appendix to the Technical Regulations.

So it looks like the FIA realised that the term direct didn’t add anything of value.

[dren]

A Honda engineer was quoted (not a journalist forming an opinion) about the use of a pre-chamber in the 2017 PU. He said it was difficult to balance the A/F ratio in the pre-chamber and the main chamber with the injector spray and air flow. He said you cannot get away from using pre-chamber ignition in the current PU formula when you want to raise combustion efficiency.

Perhaps the pre-chamber is part of the piston crown and open to air/fuel up until TDC when it encapsulates the top protruding spark plug?

I suggested that a while back in the generic PU thread (at least I think it was in that thread)

I think it's a possibility for sure.

Another wild idea would have the side injectors spraying into a side port in the piston that leads to a pre-chamber on the crown.

[subcritical71]

That’s a change for 2019. The 2018 regs say this:

5.10.2 There may only be one direct injector per cylinder and no injectors are permitted upstream of the intake valves or downstream of the exhaust valves. Only approved parts may be used and the list of parts approved by the FIA, and the approval procedure, may be found in the Appendix to the Technical Regulations.

So it looks like the FIA realised that the term direct didn’t add anything of value.

Are you sure , I double checked the 2018 rules, and just re-downloaded from the FIA site. The change is in the 2018 regs also.... (dated 2017-12-19)

[etusch]

Well, i would say the main reason HCCI was never really considered and every conversation about it was and would be a waste of time is because it's banned by the rules. The rules clearly say, that the ignition has to be initiated by a spark plug but HCCI uses compression ignition.



As i see it, TJI in this respect differs atleast in so far as there is no rule in place which wouldn't allow it.

I see a video about mazda's skyactive x engine and the Man in the video says they uses compression ignition but uses spark plug to start process in the right time. So it can be used I think. It is obvious that if it is hcci used at F1 engine again it is not completely same with road versions.

That's a bit inaccurate. As far as i know what Mazda does is running the engine with spark ignition until the right conditions are reached. For instance on a cold day you would have massive problems to start the engine up with HCCI only because the cold engine block and head takes away to much heat to reach the necessary temperature for ignition. That's also the reason why Diesel engines are sometimes very hard to start in cold weather and why they use glow plugs.

viewtopic.php?f=11&t=26621&start=15

[henry]

That’s a change for 2019. The 2018 regs say this:

5.10.2 There may only be one direct injector per cylinder and no injectors are permitted upstream of the intake valves or downstream of the exhaust valves. Only approved parts may be used and the list of parts approved by the FIA, and the approval procedure, may be found in the Appendix to the Technical Regulations.

So it looks like the FIA realised that the term direct didn’t add anything of value.

Are you sure , I double checked the 2018 rules, and just re-downloaded from the FIA site. The change is in the 2018 regs also.... (dated 2017-12-19)

Ok my copy of the 2018 regs is dated 21 September 2017 , I didn’t spot the later version. The paragraph I quote is unchanged since the 3 July 2013 version of the regs.

So this year they have, for the first season, been able to use an injector that isn’t direct ...

[1158]

I think it's a possibility for sure.

Another wild idea would have the side injectors spraying into a side port in the piston that leads to a pre-chamber on the crown.

Interesting idea and could be a neat trick.

[1158]

So this year they have, for the first season, been able to use an injector that isn’t direct ...

Have there been any clarifications/tech directives that could have lead to the change?

In my mind if a "pre-chamber" is in anyway connected to the combustion chamber (and it would have to be) it is still part of the combustion chamber and therefore an injector into the mythical pre-chamber would still be a direct injector.

Mr. Whiting's opinion may differ though.

[etusch]

A Honda engineer was quoted (not a journalist forming an opinion) about the use of a pre-chamber in the 2017 PU. He said it was difficult to balance the A/F ratio in the pre-chamber and the main chamber with the injector spray and air flow. He said you cannot get away from using pre-chamber ignition in the current PU formula when you want to raise combustion efficiency.

Perhaps the pre-chamber is part of the piston crown and open to air/fuel up until TDC when it encapsulates the top protruding spark plug?

My fancy paint skills:
https://image.ibb.co/e7MDFA/pre.png

Isn't that too late for ignition?

[henry]

So this year they have, for the first season, been able to use an injector that isn’t direct ...

Have there been any clarifications/tech directives that could have lead to the change?

In my mind if a "pre-chamber" is in anyway connected to the combustion chamber (and it would have to be) it is still part of the combustion chamber and therefore an injector into the mythical pre-chamber would still be a direct injector.

Mr. Whiting's opinion may differ though.

I’m not aware of anything that led up to this change. It’s interesting that they have chosen to emphasise the word fuel. I suppose to dissuade the injection of anything else?

[hurril]

godlameroso. Thank you, appreciated.

What is it that informs your opinion about the dis-usage of "TJI?" (Genuinely curious.)

How would you initiate combustion inside the pre chamber if the injector has to be outside of said chamber? There is a technical appendix to the regulations that specifies which types of injectors are allowed. What if in this appendix it is stated that the kind of multi stage injector needed to have a pre-chamber is not allowed?

We know the injectors are side mounted on the exhaust valve side on the Honda engine, and that the coil pack for the spark plug indicates it's mounted in a conventional way.

The most plausible method of having any kind of flame jet ignition with the current regulations is with the shrouded spark plug type.

When this has been discussed, it's been suggested that the mixture "compresses into" the pre-chamber. I, myself, struggle a bit with this and also with how it's cleared well enough post ignition. But I certainly want to believe/ understand it.

[godlameroso]

What is it that informs your opinion about the dis-usage of "TJI?" (Genuinely curious.)

How would you initiate combustion inside the pre chamber if the injector has to be outside of said chamber? There is a technical appendix to the regulations that specifies which types of injectors are allowed. What if in this appendix it is stated that the kind of multi stage injector needed to have a pre-chamber is not allowed?

We know the injectors are side mounted on the exhaust valve side on the Honda engine, and that the coil pack for the spark plug indicates it's mounted in a conventional way.

The most plausible method of having any kind of flame jet ignition with the current regulations is with the shrouded spark plug type.

When this has been discussed, it's been suggested that the mixture "compresses into" the pre-chamber. I, myself, struggle a bit with this and also with how it's cleared well enough post ignition. But I certainly want to believe/ understand it.

Shrouded Plug.


Standard Plug.


It's a mixture of the flames, and unburned free radicals coming out of the plug shroud that ignites the mixture in the main chamber. The gases are driven out of the shroud by the same effect that pushes the pistons down, ie increase in gas temperature.

It works in principle like a spark plug non-fouler.

[henry]

...

It's a mixture of the flames, and unburned free radicals coming out of the plug shroud that ignites the mixture in the main chamber. The gases are driven out of the shroud by the same effect that pushes the pistons down, ie increase in gas temperature.

...

I don’t see the difference between your description and this one.

The ignition chamber is connected to the main chamber by a number of orifices which allow jets of partially combusted products to ignite the main charge.

That’s from the Mahle description of their Turbulent Jet Ignition. https://www.mahle-powertrain.com/en/exp ... -ignition/

What’s the distinctive difference I’m missing?