Honda Power Unit Hardware & Software

[J.A.W.]

At 12,500 rpm mean piston speed is ~80km/h and it's only moving about 56mm so to be able to make multiple injections to set up your combustion event takes a very fast and precise injector. . . Just look at how fast pistons move, now imagine having to make two injections, one on the down and one on the up stroke, there's not much time to do it.

Simplifying - @ 12,500 rpm, the entire intake and compression strokes take a total of about 5 ms - you have to fit all your injection events in there somewhere.

Bear in mind, the affordable/available BRP ETEC DI 'voice coil' system - is rated for use up to 10,000 rpm...
...& that - on a 2-stroke, which is equivalent to a 4-stroke turning 20,000 rpm...

[Andres125sx]

Post by Andres125sx » 06 Apr 2017, 17:54
May I ask what was your hope at the respect?

In two weeks they can´t introduce any mayor modification. Actually not even in 1-2 months so, as they said theirselves, before Bahrein or Spain there will be no modifications... apart from software/mapping, wich in their case could bring very good results given their perfomance and gearing problems in Melbourne.

Second GP is way way too early, be patient.

I hope they surprise me, see how they boil their blood, see how they take pride, see that they punch the table and say "here we are !!" 4 or 5 races waiting is not acceptable, it is embarrassing.

Sorry but even if you find it embarrassing modifying the basic design of a PU to solve a problem like this, including design, manufacture and tests, takes months, not weeks.

Hopefully once they solve this problem, the rest of the development process this season will be minor teaks wich can be solved much faster, but an unexpected problem with the combustion process requires mayor modifications wich will affect the whole PU so they´ll have to think carefully and test extensively before taking the new PU to the track

[Tommy Cookers]

[quote=J.A.W.]Bear in mind, the affordable/available BRP ETEC DI 'voice coil' system - is rated for use up to 10,000 rpm...
...& that - on a 2-stroke, which is equivalent to a 4-stroke turning 20,000 rpm...[/quote]

no it's not equivalent
because injection 'speed' ie time window available falls at higher rpm independent of number of injection events per cycle or per rev

unless we are happy to inject fuel rather early relative to combustion ?

electromagnetics has inherently greater time ('speed') limitations than eg piezoelectrics

[mclaren111]

Post by Andres125sx » 06 Apr 2017, 17:54
May I ask what was your hope at the respect?

In two weeks they can´t introduce any mayor modification. Actually not even in 1-2 months so, as they said theirselves, before Bahrein or Spain there will be no modifications... apart from software/mapping, wich in their case could bring very good results given their perfomance and gearing problems in Melbourne.

Second GP is way way too early, be patient.

I hope they surprise me, see how they boil their blood, see how they take pride, see that they punch the table and say "here we are !!" 4 or 5 races waiting is not acceptable, it is embarrassing.

Sorry but even if you find it embarrassing modifying the basic design of a PU to solve a problem like this, including design, manufacture and tests, takes months, not weeks.

Hopefully once they solve this problem, the rest of the development process this season will be minor teaks wich can be solved much faster, but an unexpected problem with the combustion process requires mayor modifications wich will affect the whole PU so they´ll have to think carefully and test extensively before taking the new PU to the track

Hasegawa said they knew about this around Christmas 2016. This is 3 months later already, so there should be some progress.

Let's hope the gearbox / integration problem can be solved by / at the same time [-o< [-o<

[FW17]

Are mass dampers allowed t prevent drivetrain resonance?

[dren]

Are mass dampers allowed t prevent drivetrain resonance?

I don't see why not. The originals were banned because they were deemed to provide an aero effect.

[dren]

I hate to even bring this up given the arguments around the Mahle diagrams, number of injectors and what the regulations allow. But I am curious as to how creative you can be with respect to Reg 5.10.2 (one direct injector per cylinder). Specifically how do you define what exactly an "injector" is. As mentioned in the quote above, can you have multiple nozzles per injector? Can a single injector be designed to have different modes of operation? Either actively (some type of secondary solenoid) or passively (mechanical design such as I mention below)? I see no definition in the technical regulations as to the design of a fuel injector such as number of solenoids, needle valves, input signals. I believe these components have to be approved by the FIA in advance and that means someone has to make a judgement call on the design. If I was the FIA, I can see limiting the design of a single injector to having a single input signal and maybe a single solenoid and single needle valve. What if the needle valve had a complex design so that fuel flows out more than a single high pressure nozzle and may even have different timing and flow profiles for each nozzle. In short could a single (complex) injector still work somewhat like the Mahle system. With one path flowing into an enclosed pre-combustion chamber and a second path into the main combustion chamber. That with correct design you would allow for correct conditions in both (rich in pre and lean in main). With the difficulty in getting a mechanical design to operate under all conditions.

Thanks for considering my comment and be kind to me!

Richard

That's what some of us have guessed; the single DI has multiple nozzles as you suggest. There are probably several solutions to get the desired main and pre-chamber mix right.

[Craigy]

That's what some of us have guessed; the single DI has multiple nozzles as you suggest. There are probably several solutions to get the desired main and pre-chamber mix right.

I asked this before, but didn't get a reply:
How do you get air into the prechamber?

[dren]

During the intake stroke?

[Craigy]

During the intake stroke?

Basically it boils down to this: if there's a separate prechamber, which is fed by a fuel injector nozzle, how does air get into that prechamber space? I know the fuel gets in there because it's injected in there by the fuel pump under pressure and the injector. How does the air get into there?
Are you talking about air rushing into the prechamber through the tiny little nozzles that will later eject the turbulent jets of flame to ignite the main cylinder charge?

If you are, *why* would air rush in there? As I understand it, it's a sealed void.

Explain.

[dren]

It's a very small chamber that is still open to the main chamber. If gasses can escape, gases can enter during the intake and compression stroke.

[Craigy]

It's a very small chamber that is still open to the main chamber. If gasses can escape, gases can enter during the intake and compression stroke.

But the gases are "escaping" under their own pressure because they are expanding (due to being on fire).
The same can't be said for the charge air during the intake stroke.

[Tommy Cookers]

the chamber has the whole compression stroke period to fill - and, loosely, about 15:1 CR worth of pressure difference
and far less time for its combusted gas to emerge after ignition - but a much greater pressure difference

presumably a bit of development would get it working well enough
heavy throttling might be more difficult, but this is alleviated with cylinder cutting and/or driving the K hybrid style
the heat dilution SI engines already in service eg for power generation are not intended for low % powers

[Frank_]

the chamber will be flushed during the (tdc) valve overlap period wont it ? with some help from a shaped piston crown

[godlameroso]

Even more if the piston itself forms part of the pre-chamber. Then the flame jets can be incorporated into the piston crown.