Honda Power Unit Hardware & Software

[henry]

Here’s a presentation by Mahle on a project they did for the US government.https://www.energy.gov/sites/prod/files ... 2015_o.pdf

It discusses low speed, 2500 rpm operation. It, I think, gives some insight, but not definitive answers, into some of the discussion points on TJI.

On injection it says the injection event into the pre-chamber is >60° BTDC.

On ignition it says the prechamber ignites and then there is a delay before the jets are formed and the main chamber ignites. So essentially we have 2 ignition events to discuss. The first graph shows these at 25° and 9° BTDC respectively. I’ll leave those more knowledgeable to comment on whether this is early or late in comparison with normal spark ignition.

It shows max cylinder pressure at around 13-14° ATDC. I’m guessing this has informed @Saviour stivala’s assertions.

The importance of free radicals in the ignition jet is mentioned, supporting some of @godlamerosa’s points.

There is brief discussion at the end of the issue of fouling of the jet orifices. It’s claimed not to be observed as an issue. I wonder that if the chamber is formed as part of the spark plug insert whether it can be removed and replaced? This might allow more and smaller jets than the 4 or 6 mentioned in this project.

[Polite]

Here’s a presentation by Mahle on a project they did for the US government.https://www.energy.gov/sites/prod/files ... 2015_o.pdf

It discusses low speed, 2500 rpm operation. It, I think, gives some insight, but not definitive answers, into some of the discussion points on TJI.

On injection it says the injection event into the pre-chamber is >60° BTDC.

On ignition it says the prechamber ignites and then there is a delay before the jets are formed and the main chamber ignites. So essentially we have 2 ignition events to discuss. The first graph shows these at 25° and 9° BTDC respectively. I’ll leave those more knowledgeable to comment on whether this is early or late in comparison with normal spark ignition.

Very nice link, tnk u!

[saviour stivala]

The Mahle project presentation done for US Government was actually the one that convinced me that their TJI combustion system was not compatible with the needs of an engine that spends most of its working life rotating at a maximum power speed of 10500 RPM. That is apart from my opinion that it is also not compatible with FIA direct injection rules. But on the other hand it had nothing to do with my believed technical opinion that:- fuel in this here DISI ICE is injected at least 60 degrees BTDC. That maximum combustion pressure (PPP-peak pressure position) is at optimum when reached at 14 degrees ATDC (and an note here, this PPP most benefic position point goes for most engines I know off and have been around.
A post explaining all about ‘PPP’ has been posted a while back but still have to pop-up.

[saviour stivala]

As I submitted my reply post to henry the mentioned PPP post just popped-up.

[dren]

Different fuels formulation use between races I believe are not permitted by the rules nowadays.

Fuel suppliers bring fuel upgrades throughout the season.

TC had some good insight as to how they went about fuel formulation in the older non-hybrid formula a page or so back.

Thanks to henry for the article. I think some of us are confusing igniting the pre-chamber vs igniting the main lean charge when talking about ignition timing.

[Tommy Cookers]

.... In the NA 2.4L V8 era both fast burn and slow burn fuel was being formulated and used according to circuit specifics needs, .....mentioning a particular test comparison and it’s results between F1 formulated fuel and that formulated for normal road car use of which both are as per FIA fuel formulation... FERRARI F1 F60 with its tipo 056 2.4L NA V8 Driven by Alonso at Fiorano. 4 laps ran using FI fuel resulted in a best lap time of 1:03.950. 4 laps ran using Shell normal road pump fuel resulted in a best lap time 9/10ths slower but the road pump fuel produced a faster top speed.......

road fuel being 1.5% worse on laptime might suggest that (presumably the 'worst' version) NA F1 fuel wasn't slow burning
and the road fuel was an expensive version intended for sporty cars so might have been faster burning than the usual road fuel
despite the usual assumption that the higher the ON the slower the combustion

current F1 fuel has presumably the highest possible mass-specific heat content and ON regardless of other properties

[saviour stivala]

.... In the NA 2.4L V8 era both fast burn and slow burn fuel was being formulated and used according to circuit specifics needs, .....mentioning a particular test comparison and it’s results between F1 formulated fuel and that formulated for normal road car use of which both are as per FIA fuel formulation... FERRARI F1 F60 with its tipo 056 2.4L NA V8 Driven by Alonso at Fiorano. 4 laps ran using FI fuel resulted in a best lap time of 1:03.950. 4 laps ran using Shell normal road pump fuel resulted in a best lap time 9/10ths slower but the road pump fuel produced a faster top speed.......

road fuel being 1.5% worse on laptime might suggest that (presumably the 'worst' version) NA F1 fuel wasn't slow burning
and the road fuel was an expensive version intended for sporty cars so might have been faster burning than the usual road fuel
despite the usual assumption that the higher the ON the slower the combustion

current F1 fuel has presumably the highest possible mass-specific heat content and ON regardless of other properties

if interested in that fuel comparison test try trace and viste "how close is F1 fuel to road car fuel//F1 news//james allen on F1" also "shell v-power race fuel vs shell v-power road fuel" at that time the test was also futured no "BBC-Jake Hmphery shell v-power fuel test".

[saviour stivala]

Mixture burn time versus engine speed. The time for an overall burn.
Standard road car at near max power (4000 RPM) 2.1 ms burn time.
Formula 1 car (NA V8 at max power (19000 RPM) 0.4 ms burn time.
How does the flame burn all mixture in the cylinder at high engine speed?, the turbulent intensity increase with piston speed, the turbulent burning velocity is proportional to the turbulent intensity. At higher engine speeds the turbulent velocity is also higher, less time is needed to burn the entire mixture.

[PlatinumZealot]

The resultant fast flame speed when TJI combustion system is used that reduces the need for much ignition advance is the result of the main combustion chamber contents being ignited by a fast flame that is the result of an already combusted small content by a spark plug inside a pre-chamber. But talking about such technical matters regarding high speed operation of a F1 engine the following should be born in mind. A faster combustion (time wise) is not necessary a stronger and more complete combustion than a slower combustion, again (time wise). The present 1.6L T V6 ICE spending most of its racing life at a max power speed of 10500RPM fires all 6 cylinders 5250 times in one minute. The previous 2.4L NA V8 spending most of its racing life at a max power speed of 17500RPM used to fire all 8 cylinders 8750 time in one minute, at that time teams were using both fast burn formulated fuel as well as slow burn, depending on circuit specifics. In both cases (both types of ICE) the ignition advance used is solely aimed to move the maximum combustion pressure point to 14 degrees ATDC power stroke.

Slower combustion is not really an option. How the TJI makes up for "completeness" by utilizing multiple jets travelling radially outwards like a star shape to emmulate a near homogenous combustion. It's a pretty neat trick.

[saviour stivala]

The resultant fast flame speed when TJI combustion system is used that reduces the need for much ignition advance is the result of the main combustion chamber contents being ignited by a fast flame that is the result of an already combusted small content by a spark plug inside a pre-chamber. But talking about such technical matters regarding high speed operation of a F1 engine the following should be born in mind. A faster combustion (time wise) is not necessary a stronger and more complete combustion than a slower combustion, again (time wise). The present 1.6L T V6 ICE spending most of its racing life at a max power speed of 10500RPM fires all 6 cylinders 5250 times in one minute. The previous 2.4L NA V8 spending most of its racing life at a max power speed of 17500RPM used to fire all 8 cylinders 8750 time in one minute, at that time teams were using both fast burn formulated fuel as well as slow burn, depending on circuit specifics. In both cases (both types of ICE) the ignition advance used is solely aimed to move the maximum combustion pressure point to 14 degrees ATDC power stroke.

Slower combustion is not really an option. How the TJI makes up for "completeness" by utilizing multiple jets travelling radially outwards like a star shape to emmulate a near homogenous combustion. It's a pretty neat trick.

Agree that the Mahle TJI produces a near homogenous main (2nd) combustion by utilizing multiple flame jets produced by the 1st combustion which is started in a pre-chamber by means of a spark plug.

[ringo]

The Mahle project presentation done for US Government was actually the one that convinced me that their TJI combustion system was not compatible with the needs of an engine that spends most of its working life rotating at a maximum power speed of 10500 RPM. That is apart from my opinion that it is also not compatible with FIA direct injection rules. But on the other hand it had nothing to do with my believed technical opinion that:- fuel in this here DISI ICE is injected at least 60 degrees BTDC. That maximum combustion pressure (PPP-peak pressure position) is at optimum when reached at 14 degrees ATDC (and an note here, this PPP most benefic position point goes for most engines I know off and have been around.
A post explaining all about ‘PPP’ has been posted a while back but still have to pop-up.

This is injection. When is the ignition?

[saviour stivala]

The Mahle project presentation done for US Government was actually the one that convinced me that their TJI combustion system was not compatible with the needs of an engine that spends most of its working life rotating at a maximum power speed of 10500 RPM. That is apart from my opinion that it is also not compatible with FIA direct injection rules. But on the other hand it had nothing to do with my believed technical opinion that:- fuel in this here DISI ICE is injected at least 60 degrees BTDC. That maximum combustion pressure (PPP-peak pressure position) is at optimum when reached at 14 degrees ATDC (and an note here, this PPP most benefic position point goes for most engines I know off and have been around.
A post explaining all about ‘PPP’ has been posted a while back but still have to pop-up.

This is injection. When is the ignition?

The Mahle TJI two ignitions are shown to be at 25 degrees and 9 degrees BTDC, but as is the case with any ignition these numbers are floating in accordance with among others, engine speed and engine load so move the PPP point to as near as could be to 14 degrees ATDC. as to

[saviour stivala]

Formula 1 turbo hybrid fuel injection:- Fuel injection regulations 5.10.2 up to end of 2013 mandated an MPFI system, those rules has shown that all engine manufacturers converged on the same injector position and type of injector as well as injection mode, a shower type of injector on top of each cylinder intake port injecting for virtually the full four engine cycles (720 crankshaft degrees). Fuel injection regulations 5.10.2 from 2014 mandated a DI-GDI system so position of injector is fixed to inject inside cylinder, I have no doubt that like they did before all formula 1 engine manufacturers have this time also converged on the same injector position and injector type and style of injection.(injector position being exhaust side mounted). This DI-GDI injection system lost the freedom of when to inject fuel that the MPFI shower type had as well as the ability to pre-mix air and fuel. The previous MPFI injection period was something of the order of 12ms at 10000RPM. The present DI-GDI injection period at likewise 10000 RPM falls to something of the order of 1.6ms. Increasing engine speed reduces this time for evaporation and mixing still further.

[Bandit1216]

This DI-GDI injection system lost the freedom of when to inject fuel

Hi, Why is that?

[godlameroso]

Because with port injection, you can spray fuel independent of valvetrain or piston motion because the injectors are not inside the CC. With DI you are forced to inject inside the CC, and are limited by piston and valvetrain motion.