Cam-less engine - PeachParts Mercedes-Benz Forum

cmac2012 · #1 08-14-2017, 06:47 PM

This is better progress than I was aware of. I last searched on this years ago, 8 to 10 years probably, and they were talking about electro magnets then. These guys are using air pressure to do the work:

http://jalopnik.com/what-its-like-to-ride-in-a-car-with-the-camless-engine-1529865968

Being developed by Koenigsegg and crew, at least this one is. I can only imagine the engines are non-interference.

cmac2012 · #2 08-14-2017, 10:29 PM

https://www.youtube.com/watch?v=Bch5B23_pu0

Dubyagee · #3 08-15-2017, 06:19 AM

Thats brilliant from an individual cylinder management pov.

cmac2012 · #4 08-15-2017, 03:52 PM

I fantasized years ago about using a camless engine for jake-brake like recycling of energy, my thought was to store compressed air in a series of tanks, say 3, with each tank given time to cool off in series, so that said air could be released for use as turbo-like boost, only it would be major deluxe turbo boost - the air would be cold from decompression and no parasitic energy draw was made on the system to gain that boost.

Imagine a tank compressed to 1000 psi. I'm sure there's a lot I don't know about turbo boost but I found this for use as a basis:

Quote:

Turbochargers allow an engine to burn more fuel and air by packing more into the existing cylinders. The typical boost provided by a turbocharger is 6 to 8 pounds per square inch (psi). Since normal atmospheric pressure is 14.7 psi at sea level, you can see that you are getting about 50 percent more air into the engine. Therefore, you would expect to get 50 percent more power. It's not perfectly efficient, so you might get a 30- to 40-percent improvement instead.

Turbochargers and Engines - Turbochargers and Engines | HowStuffWorks

I'd have to do some serious research to really get my head around this (I've tried, not sure my knowledge of thermodynamics is up to the task) but I know that decompressed air can get pretty cold. If it was decmpressed immediately after compressing, would probably be somewhat normal temp, as the compressed air would be pretty hot. Let the tank cool however and the decompressed air can easily be sub-freezing.

FTSOA, let's say that one could do controlled releases of air at 30 psi and 32 degrees F. My guess is that it would provide good power. I can only imagine that compressed air is not legal in drag racing, putting ice in an intercooler sort of a different category, the compression was obtained by the engine.

I found this article of an experiment on that score.

Compressed-Air Supercharging - Hot Rod Network

Don't know if it's legal or not - but that's beside the point. Camless engine produced compressed air is derived from on board fuel, it's not a stored sort of energy that will run out soon enough. And the fact of it being gained from braking, saving wear and tear on discs and pads is very attractive.

It might be possible to use a 2.0 liter, beefed up to handle high boost, to do the work of larger engines. One could use the frost boost for accelerating and normal aspiration for cruising. Add to that other efficiencies from ideal valve timing and potential mpg figures could be very good.

Dubyagee · #5 08-15-2017, 04:08 PM

Thats a great idea. I was messing around with the idea of a variable compression ratio with rotary valving but the pneumatic design beats it by miles

cmac2012 · #6 08-15-2017, 04:30 PM

Quote:

Originally Posted by Dubyagee

Thats a great idea with rotary valving but the pneumatic design beats it by miles

Koenigsegg is way ahead of me. He mentioned that as well as using some of the compressed air for acceleration. Impossible to know at this point if the air would be more valuable for combustion boost or direct propulsion. Somehow I think the former. If such system ever did get going, I could imagine the ability to partially charge the system before departure, depending on how much compressed air was onboard.

One thing is certain, such an engine would have a serious ECU. Balancing all of that for optimal use would be rocket science.

It also occurs to me that they're talking about using compressed air to drive the valves downward, so in that case, having a regular supply of compressed air on board would be necessary. That was always a point that struck me as difficult in the cam-less concept. Reliably pushing on those valves 25 to 35 times a second could be tough. I had thought about a rotary valve setup for that. Perhaps easier to rotate than compress the spring every time. But I could imagine other problems with that.

75Sv1 · #7 08-15-2017, 05:02 PM

I think Renault used compressed air in their camless engine in the late 80's early 90's, in F1. It was a V-10. Sort of started the trend of V-10s.

Dubyagee · #8 08-15-2017, 06:03 PM

I think I remember the Renault design somewhere.

My rotary valving idea was just a shaft with notches cut into it that corresponded with ports in the head for exhaust and intake. RPM limited by the bottom end only and way less power to spin. Would shrink the heads to almost flat head specs.

Not as controlled as the video showed but rugged

Angel · #9 08-15-2017, 08:16 PM

Quote:

Originally Posted by cmac2012

...

It also occurs to me that they're talking about using compressed air to drive the valves downward, so in that case, having a regular supply of compressed air on board would be necessary. ....

we can do compressed air at 100-300 psi, that's easy.
If they always need compressed air, now they need to either get an electric air compressor, or attach one to the motor...and if you run out of compressed air, your engine stops. maybe the parasitic drag of an air compressor wont be enough to worry about, or will be eclipsed by thermodynamic efficiency gains of variable valve timing (and higher rpms?) but it feels like the free lunch is getting costly.

and what to do with extra compressed air ? remember that if they put it in the engine, the ECU needs to be able to react fast enough to keep emissions in spec. They are probably capable of this now with existing twin turbo setups etc....but I see a pressurized air tank (with ???psi in it) needing a serious regulator, decent diameter pipe and good engineering to work in 2017.

I think the equation is PV=RT - that allows you to see how many of air you get from a given of air at XX pressure.

hereafter- "?" means I'm not sure

basic google: Looks like a basic 2.0L 4 cyl needs 150cfm to run if not supercharged. 300cfm would then give you 15psi of boost (? - Plenty?). Actually less boost because a NA engine intake is always at less-than-atmospheric pressure when running. but anything above 6 or 8 psi is a notable bonus. I'm way open to better facts/curves here.

https://www.chemicool.com/cgi-bin/gaslaws.pl

assume: temperature is held constant at 80F (it wont be, but my thermodynamics arent that good here either)

if you have a 10cu-ft air tank at 1000psi (70atm?), how long will you get 15psi of boost ?
If I'm doing this right, it has 805 moles of air in it, and when vented at 15psi/2atm- nets you 349 Cubic feet of air.
So if you had a 10cu-ft air tank at 1000psi, you could get a full minute at 10-15psi of boost. that's not insignificant.

Sorry for the mixing of 'Merican units

Maybe this isn't such a bad idea. surely I'm missing some physics somewhere (turbulent flow out of tank, friction losses, expensive 2" solenoid valves, fittings and piping in a civilian car that must be rated to 1000psi...

-John

cmac2012 · #10 08-20-2017, 01:53 AM

That's some good figuring there. I haven't tried to do it all myself yet, I mean verify your work. Not that I doubt you, but unless I understand the route you took to get there I won't really have learned much.

I've often considered that I'm talking through my hat on this somewhat as I don't really know if the amount of air that could be gathered and compressed through the jake-braking compression would be of sufficient quantity - moles of oxygen molecules per unit of space (at a given compression) - to last long enough to be a large plus.

Stop and go driving would yield a fair amount, but that's when you'd need accelerating power. Highway driving wouldn't involve a lot of braking but neither is there much acceleration needed.

I can only guess that Koenigsegg's engine would need to have a small auxilliary compressor, one capable of compressing enough to power the valves even w/o any braking, or else, as mentioned, be dead in the water. Hard to know if the parasitic drain by a compressor would be greater of less than driving a cam shaft and pushing springs.

On the other end of possibilities, what if collecting jake braked compressed air for cooling as a way of shedding heat from braking, and this w/o doing the noisy fart of compressed air on current truck jake brakes, ended up collecting more air than could be used? You hinted at that somewhat. I could imagine that it could either be bled off or perhaps used to drive one or two cylinders until it reached a manageable level. Koenigsegg mentions using compressed air for propulsion in the vid, one guesses there wouldn't be enough to use for long.

Another question that's interesting to ponder, what would be an optimal pressure for use in acceleration? With too much, seems you'd either destroy the engine or reach a point of diminishing returns. I'm guessing the degree of beefing up of the engine would determine the max that should be used.