Honda Power Unit Hardware & Software

[godlameroso]

Do these engines produce a fair amount of NOx?

Higher injection pressures would allow better atomization, otherwise you have to rely on air dilution and natural EGR to aid fuel vaporization. The spray pattern of the injector could feed the pre-chamber and main chamber independently, but it requires a very precise injector because the timing is critical.

The pre chamber nozzles are also very important, you need to size them accordingly. Too many nozzles and the jets won't have enough penetration across the cylinder volume, to few and you won't have enough sources to consume the lean mixture. The opening into the pre-chamber is also important.

The pistons probably have to deal with several compromises as well.

[bigblue]

The words "completely new combustion process" obviously brings concerns. Is it even possible to explain the progression from 2015 to this mid-2018 engine, in terms of combustion process ? Does one process evolve into another, or is it a sort of "start again from scratch" scenario ? It's quite worrying if it's the latter as often things don't work out as intended, then again I guess you have the previous versions as a benchmark, and all the lessons learned from those engines, if only in terms of reliability, layout, and energy recovery philosophy. I suppose the glass half-full view is that there is still the potential for big gains if rather different combustion is on the cards going forwards ? Anyway, I'm sure you can understand the caution after the last few years.

[roon]

A few pages back we were having a discussion on the possibility of complex runner shapes and unusual valve arrangements.

I've developed a couple of concepts which might explain what that means, and why it could be beneficial. Both concepts re-order the traditional intake runner layout in order to introduce intake air tangentially into the cylinder and promote vertically-oriented helical vorticity within the cylinder, something not readily attainable with traditional parallel runners and plain poppet valves. Something I'm calling Helical Induction Intake Ports (HIIP).

The following illustration depicts HIIPs with one warped intake runner that wraps around the spark plug.



Next, a version of HIIPs which stacks the intake valves (as well as the exhaust valves) on top of each other and pairs the valves left-to-right, instead of the traditional fore-to-aft, relative to crankshaft centerline.



The aim would be to create a strong vortex that can provide stratified fuel-air-ratios within the cylinder, ideally locating the richest part of the charge in the center of the cylinder, where the spark plug is. Coarsely structured, predictable flow structures within the cylinder may also help deal with detonation by limiting the areas in which they occur.

[godlameroso]

The words "completely new combustion process" obviously brings concerns. Is it even possible to explain the progression from 2015 to this mid-2018 engine, in terms of combustion process ? Does one process evolve into another, or is it a sort of "start again from scratch" scenario ? It's quite worrying if it's the latter as often things don't work out as intended, then again I guess you have the previous versions as a benchmark, and all the lessons learned from those engines, if only in terms of reliability, layout, and energy recovery philosophy. I suppose the glass half-full view is that there is still the potential for big gains if rather different combustion is on the cards going forwards ? Anyway, I'm sure you can understand the caution after the last few years.

I would say that they started 2015 with a fuel hungry engine with a weak ERS, and 2016 improved on this in every respect. The 2017 was a brand new architecture, and a brand new combustion concept based on the pre-chamber, they took a step backwards and it led them to a net step forward at the end of 2017. 2018 first spec engines are a new combustion concept that was developed with lessons learned in 2017, and this has led them to the development of the next evolution that's planned for mid season. New means same concept but new hardware to exploit the things you learn along the way.

Those are very nice drawings and it's cool to see exactly what I was thinking visualized. Taking it a step further, let's say there's vorticity during the intake phase, then the kicker is where is the perfect timing in the piston stroke to induce turbulence? That has a lot to do with the intake valve close event, combustion chamber and piston crown shape. And where is the best timing to inject fuel. How much heat does the spark plug retain? If you're having trouble igniting the prechamber reliably I'm sure you've tried really long plugs, and everywhere in between.

[Bence]

The Lancia Triflux was also a highly unorthodox and elegant way of thinking outside of the box.

[1158]

Do the regs specify valve diameter? I tried looking but I have a feeling I'm not seeing all the regs.

[godlameroso]

5.3.3 Valve stem diameter must not be less than 4.95mm. Otherwise they're normal round poppet valves, but angle, and diameter of the valves/seats is free.

[1158]

5.3.3 Valve stem diameter must not be less than 4.95mm. Otherwise they're normal round poppet valves, but angle, and diameter of the valves/seats is free.

What if 1 gigantic intake valve was used with a smaller valve for the prechamber. 5.1.8 states the engine must have 2 intake and 2 exhaust valves per cylinder so I don't think you could get away with a 3rd smaller intake valve for the prechamber.

Would one larger valve versus 2 smaller ones in a forced induction engine be that big of a handicap?

[godlameroso]

Not really, engine speeds are relatively low, two smaller valves however have lower inertia, and less mass than one big valve. Flow, seal, and valve inertia are more engineering challenges when using one valve, and not power or efficiency dead ends. However time is of the essence.

But how would you use a valve for the pre-chamber? The challenge is getting a mixture of air and fuel in the pre-chamber at the correct level to ignite a much leaner mixture. Maybe a vortex where a lean air fuel mixture swirls around and in the middle a slightly richer mixture to ignite the pre-chamber like Mazda does?

[1158]

Not really, engine speeds are relatively low, two smaller valves however have lower inertia, and less mass than one big valve. Flow, seal, and valve inertia are more engineering challenges when using one valve, and not power or efficiency dead ends. However time is of the essence,

Good point. I didn't think about the increased weight. Was just wondering how effective a "normal" CC/cylinder design would be at ensuring fresh air for the prechamber. Than again maybe it's not even an issue.

[Brake Horse Power]

Next, a version of HIIPs which stacks the intake valves (as well as the exhaust valves) on top of each other and pairs the valves left-to-right, instead of the traditional fore-to-aft, relative to crankshaft centerline.

https://i.imgur.com/B2BCElq.jpg

Don't the intake valves clash once both opened?

[63l8qrrfy6]

Next, a version of HIIPs which stacks the intake valves (as well as the exhaust valves) on top of each other and pairs the valves left-to-right, instead of the traditional fore-to-aft, relative to crankshaft centerline.

https://i.imgur.com/B2BCElq.jpg

Don't the intake valves clash once both opened?

The angle between the intake valves is very small - they do come close as they open but won't touch.

[godlameroso]

Not really, engine speeds are relatively low, two smaller valves however have lower inertia, and less mass than one big valve. Flow, seal, and valve inertia are more engineering challenges when using one valve, and not power or efficiency dead ends. However time is of the essence,

Good point. I didn't think about the increased weight. Was just wondering how effective a "normal" CC/cylinder design would be at ensuring fresh air for the prechamber. Than again maybe it's not even an issue.

It is a challenge, maybe a side injector with a pocket in the piston for the injector, the combustion chamber is almost diesel like, very little curvature, not at all like the conventional pent roof chambers. The pre-chamber could sit just above the injector, and the injector uses a "pre-chamber spray pattern". Prior to this during the intake phase the main charge of fuel is sprayed with the "main chamber spray pattern", the swirl during intake segregates the main chamber mass, and allows a tiny and precise spray into the prechamber during the compression stroke. During this period the swirl will be transitioning to tumble/squish to aid mixing(if the engineers designed the system properly), the pre-chamber begins to ignite ~34 degrees BTDC, at ~16 degrees BTDC the flame jets begin penetrating across the chamber volume, at ~7 degrees BTDC the mixture begins igniting from outside in, and the pressure begins to rise dramatically until a few degrees ATDC where maximum heat release happens. With luck you timed everything well enough that maximum heat release happens just as the piston begins moving down, so that the combustion aids the crank's inertia.

Random thought, with the electric turbo one doesn't need fully closed intake or exhaust valves due to being able to control boost and back pressure. Design engine with 18:1 compression that operates like a 15:1 with late intake or early exhaust valve opening?

[PlatinumZealot]

You could make an oblong-rectangular shaped valve. A big ole valve that is as wide as two valves but the same height as one valve. Technically it could be lighter than two circular valves if designed right. The challenge would be manufacturing the thing, not to mention a really funky valve seat. So that out of the way, how do you make the second valve work with TJI while being legally an intake valve now?

[Wazari]

Do these engines produce a fair amount of NOx?

Higher injection pressures would allow better atomization, otherwise you have to rely on air dilution and natural EGR to aid fuel vaporization. The spray pattern of the injector could feed the pre-chamber and main chamber independently, but it requires a very precise injector because the timing is critical.

The pre chamber nozzles are also very important, you need to size them accordingly. Too many nozzles and the jets won't have enough penetration across the cylinder volume, to few and you won't have enough sources to consume the lean mixture. The opening into the pre-chamber is also important.

The pistons probably have to deal with several compromises as well.

Yes, more than a fair amount of NOx.