Honda Power Unit Hardware & Software

[ncassi22]

The article mentions the Pneumatic valve system. It dindn't make clear whether the system was reduced in components/simplified to save weight or dumped for a springvalve system. Also it says something about injectors on the exhaust side??? Translation errors or something else?

I read it to mean Honda went from original pneumatic valve return to conventional coil springs to eliminate the pneumatic system weight. It says each coil spring is actually a triple-spring combo, which typically prevents any one spring resonance from dominating and provides light friction damping between springs. Current materials and dynamic modeling make conventional springs possible at revs where pneumatic used to be needed.

Would be interesting to know if other engines (Merc., Ferrari, Renault) use coil springs instead of pneumatic, and would be interesting to know if Honda sticks with coil-spring for the higher revs in 2021.

Going back to coil springs over Pneumatic is a very odd thing to do and I find it very very srprising. Even at "only" 13,000 rpm the valvetrain dynamics are very hard to control when using aggressive ramps. Jerk is not your friend.
Not to mention the difference in weight between the valve springs themselves and the entire Pneumatic system is not as great as one might think.

Yeah my thoughts too? Could this be part of the friction issue Brown and then Wazari alluded to. I hope he can share his thoughts on this.

[amho]

Also it says something about injectors on the exhaust side??? Translation errors or something else?

Injectors on the exhaust side is nothing strange. The injector merely sits on the cylinderbank together with the exhaust valves instead of with the intake valves.

I always thought that the injector is placed in the top of prechamber, but If injector is in exhaust side (as motor fan pic. indicates) how do they have rich mixture in the prechamber? there might be multiple injection first one when piston is near tdc to mainly fill prechamber?
https://drive.google.com/open?id=1tpCUl ... SY3ZJV5gNa

[roon]

Maybe stacked belleville springs instead of coil, to mimic the symmetrical loading offered by pneumatics.

[63l8qrrfy6]

Multiple valve springs with friction damping makes no sense whatsoever.
Renault have PVRS - Hulky I think retired due to loss of pneumtic pressure.
Mercedes have PVRS on the hypercar - surely they have it on the F1 engine too.

Other than the actual seal diaphragm and the pneumatic barrels they only need a pressure vessel with a regulator and a few hoses.

[bill shoe]

Google "triple valve springs", then go to images. It's the standard high performance valvespring config. I think the middle spring is often there to provide control and light damping to the inner and outer springs that do most of the heavy lifting.

[Wazari]

Today's valves springs can handle 13,000 PRM with no problem.

[godlameroso]

I mean Honda made single coil springs that could handle 9,100 rpm and 400,000km of service back in 1999. I would not be surprised if they had valve springs capable of handling 13k for 7,000km 19 years later.

[ncassi22]

I mean Honda made single coil springs that could handle 9,100 rpm and 400,000km of service back in 1999. I would not be surprised if they had valve springs capable of handling 13k for 7,000km 19 years later.

In terms of reliability yes, however I was thinking in terms reducing friction... wouldn't every hp they could squeeze out be helpful. The snowball effect of which has been discussed here. My (admittedly non-enigneer) brain would think the close to 5 bar boost would require some heavy duty springs?

*edit - did some reading. Seems boost doesn't have much of an effect.

[godlameroso]

Believe it or not engine speed puts much more stress on the rotating assembly than cylinder pressure.

The part that really amazes me is that the top piston ring is under far more stress than the valves/springs, and a cylinder ring is thin, and relatively brittle, you can break it with your hands by bending it aggressively.

[PlatinumZealot]

I mean Honda made single coil springs that could handle 9,100 rpm and 400,000km of service back in 1999. I would not be surprised if they had valve springs capable of handling 13k for 7,000km 19 years later.

In terms of reliability yes, however I was thinking in terms reducing friction... wouldn't every hp they could squeeze out be helpful. The snowball effect of which has been discussed here. My (admittedly non-enigneer) brain would think the close to 5 bar boost would require some heavy duty springs?

I dont see how friction to turn the cam would change much versus pneumatic if the springs are designed properly. Pneumatic is also addtional complexity and space taken up.

[ncassi22]

I dont see how friction to turn the cam would change much versus pneumatic if the springs are designed properly. Pneumatic is also addtional complexity and space taken up.

I didn't take into account that the air would need to apply the same pressure as a physical spring would to keep the valve closed or pressed against the rocker. Pretty dumb on my part

[PlatinumZealot]

No. not dumb actually!
above higher rpms there is a point where the spring has to be made stiffer to prevent hysteresis, resonance and all sorts of effects and not necessarily because increased spring presssure is needed for the valve. In those cases air will be an advantage you since can use less pressure there. But i think the rpms of the current regs being sub 13,000 rpms, is in the realm of springs and with F1 know how applied you can bet that those springs will be specially designed to be light and soft as possible.

[Tommy Cookers]

'prevent hysteresis' - nonsense !

hysteresis is an inherent characteristic of the material and not something that can be changed by design
metals have little hysteresis and higher strength versions of metals ie spring materials have less than little hysteresis
so the best qualified spring materials via high strength are also the best via low hysteresis

hysteresis can down in the region of ten parts per million and should be close to that in a race valve spring
ok such a valve spring will be generating hundreds of times per second that hysteresis (loss of strain energy) as self-heat
which will certainly need removing by properly designed coolant flow

force measurement in eg wind tunnel tests of race cars or when buying a piece of steak depends on the low hysteresis of metal
the load cells or balances work by measuring the dimensional change in metal with change in load
hysteresis would show as a residual error ie the output not returning to zero when the load is removed

true hysteresis is the residue after unloading and allowing the self-heat to disperse
most load cells are fortunately small enough for natural heat dispersion within the time taken by the calibration procedure
but with large load cells the calibration procedure should allow for this (but probably hasn't)
anyway various behaviours of the strain-sensing side tend to add to overall attribution as measurement 'hysteresis'


regarding eg triple valve springs (or similar doubles) ..... afaik
interference friction develops at incipient surge resonance of main spring(s) and by design this won't be at continuous rpm
in an engine committed to lasting several events untouched

[63l8qrrfy6]

Google "triple valve springs", then go to images. It's the standard high performance valvespring config. I think the middle spring is often there to provide control and light damping to the inner and outer springs that do most of the heavy lifting.
http://www.jegs.com/images/photos/200/278/278-1248.jpg

I have not denied their existence - my point is that as soon as you need more than 1 spring and friction damping you are already better off using a pneumatic system.

That being said, I still believe that it can be done with a well engineered single spring.

[hurril]

Also it says something about injectors on the exhaust side??? Translation errors or something else?

Injectors on the exhaust side is nothing strange. The injector merely sits on the cylinderbank together with the exhaust valves instead of with the intake valves.

I always thought that the injector is placed in the top of prechamber, but If injector is in exhaust side (as motor fan pic. indicates) how do they have rich mixture in the prechamber? there might be multiple injection first one when piston is near tdc to mainly fill prechamber?
https://drive.google.com/open?id=1tpCUl ... SY3ZJV5gNa

I know, right? I've wondered that from the start and the only thing that seems possible is for the injector to create a denser cloud close to the holes in the pre-chamber and then hope that enough of it gets sucked/ pushed in there by the compression. (The pressure gradient is evened out/ lowered so that it is equal on both sides of the "membrane" that the holes form, thereby pulling the fuel with it.)

There seem to be so many concurrently active factors that go in to this though and it's not that easy to form a working picture of all of them I think.