Or SPCCI. Probably neither of those would work in a flathead. Anyway HCCI is difficult enough with DOHC, and for SPCCI you would need swirl in the combustion chamber. How is that done with a flathead?
Anyway, if one really tried any of these in a flathead, the compression ratio should be increased tremendously. The space left for valves would be very low.
"Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere."
– Colin Chapman, design engineer, inventor, and founder of Lotus Cars
I am still talking about the alternate combustion processes which resemble very much Diesel, and no throttle control is used.
One possibility would be SVPC (single valve per cylinder) in which there is only one poppet valve per each cylinder, opening to a nice round combustion chamber. There swirl would be possible. However there should be another low pressure valve to change gas flow between intake and exhaust. The other valve could be rotating, flapping or what ever.
Kind of extreme solution would be leaving the other valve completely out or using only a reed valve to prevent exhaust gases flowing to the intake side, then pumping excess amount of air, and using a turbocharger for that.
"Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere."
– Colin Chapman, design engineer, inventor, and founder of Lotus Cars
I think that the single poppet valve scheme would be easiest in a Diesel engine. Some kind of check valve or reed valve would be needed for each intake port to prevent exhaust pulses reaching intake manifold. But I think those would be all valves needed: one poppet valve and one reed valve per each cylinder. The combustion chamber would become compact and round, allowing high compression ratio.
Perhaps a unit injector could be placed in the empty space of a removed valve. On the other hand, the injector should not be placed in the exhaust port. So, I don't know would that work.
"Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere."
– Colin Chapman, design engineer, inventor, and founder of Lotus Cars
The Gnome Monosoupape worked with a single valve and needed no auxiliary valves. But of course it used a very short stub pipe with no manifolding, muffling or filtering. Might be tolerable with a dragster but probably not much else. Plus it doesn't allow any pressure wave/inertia tuning.
Perfectionism is the enemy of actually getting shit done.
pdq67 wrote: ↑Sat Mar 30, 2019 8:05 pm
Is it possible to make a cam such that one valve can be used for both, the intake event as well as the exhaust event?
Suppose there is one high pressure poppet valve that takes care of both intake and exhaust. There should be some kind of low pressure valves below the poppet valve, completely outside of the combustion chamber. The low pressure intake valve could be a reed valve. The low pressure exhaust valve could be (for example) a slide valve or a poppet valve. Also a slide valve could work as a changer between intake and exhaust. If the low pressure exhaust valve is also a poppet valve, it could be driven by the same cam lobe as the high pressure valve, although phase must be advanced.
"Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere."
– Colin Chapman, design engineer, inventor, and founder of Lotus Cars
Nikolas Ojala wrote: ↑Sun Mar 31, 2019 5:49 am
Suppose there is one high pressure poppet valve that takes care of both intake and exhaust. There should be some kind of low pressure valves below the poppet valve, completely outside of the combustion chamber. The low pressure intake valve could be a reed valve. The low pressure exhaust valve could be (for example) a slide valve or a poppet valve. Also a slide valve could work as a changer between intake and exhaust. If the low pressure exhaust valve is also a poppet valve, it could be driven by the same cam lobe as the high pressure valve, although phase must be advanced.
And evolution to that scheme would be two poppet valves per cylinder so intake and exhaust gases could be totally isolated until cylinder - better cylinder flush, less temperature from exhaust to intake charge, better flowing ports and so on.
naukkis79 wrote: ↑Sun Mar 31, 2019 7:37 am
And evolution to that scheme would be two poppet valves per cylinder so intake and exhaust gases could be totally isolated until cylinder - better cylinder flush, less temperature from exhaust to intake charge, better flowing ports and so on.
Except, in case of flathead, worse shaped combustion chamber. That would be acceptable as long as it is a gasoline engine with low compression ratio 8:1. But if one desires much higher compression ratio, the ordinary L-head becomes a problem.
"Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere."
– Colin Chapman, design engineer, inventor, and founder of Lotus Cars
Nikolas Ojala wrote: ↑Sun Mar 31, 2019 5:49 am
Suppose there is one high pressure poppet valve that takes care of both intake and exhaust. There should be some kind of low pressure valves below the poppet valve, completely outside of the combustion chamber. The low pressure intake valve could be a reed valve. The low pressure exhaust valve could be (for example) a slide valve or a poppet valve. Also a slide valve could work as a changer between intake and exhaust. If the low pressure exhaust valve is also a poppet valve, it could be driven by the same cam lobe as the high pressure valve, although phase must be advanced.
And evolution to that scheme would be two poppet valves per cylinder so intake and exhaust gases could be totally isolated until cylinder - better cylinder flush, less temperature from exhaust to intake charge, better flowing ports and so on.
Nikolas Ojala wrote: ↑Sun Mar 31, 2019 8:16 am
Except, in case of flathead, worse shaped combustion chamber. That would be acceptable as long as it is a gasoline engine with low compression ratio 8:1. But if one desires much higher compression ratio, the ordinary L-head becomes a problem.
Pete1 wrote: ↑Tue Apr 16, 2019 8:34 pm
"But if one desires much higher compression ratio, the ordinary L-head becomes a problem".
What problem? We have been running 14 to 1 on flathead Fords since the early 50's.
Do you have some pictures or diagrams of 14:1 combustion chambers and pistons for a flathead Ford?
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