Yair . . . Given that no form of rotary/turbine is going to displace the reciprocating engine any time soon and given the wide acceptance and gradual improvement in electronic injectors I put it to a couple of old petrol heads the other day that doing away with camshafts and conventional valve gear would be a wonderful opportunity for the boffins to make life really interesting. Imagine an engine with a electronic computer controlled gizmo operating each valve and imagine the wonderful overlaps and dwell times that could be dialled in. One of them reckoned it was doubtful a small enough gizmo could be built that would generate the necessary force to open a valve and then some one suggested sleeve valves and about then my eyes glazed over and I had another rum. Any one out there with opinions? Cheers.
To my knowledge nobody has ever been able to make a sleeve style valve that is durable enough to be accepted. And I know that individual valve actuation has been tried, but I think variable cam shaft timing gives you most of the bennefits without all the failure prone parts individual actuators would have. ISZ
While it may not yet be possible, maybe one day it will, and think of the flexibility that designers will have then. The ability to deactivate one cylinder at a time for economy, instead of the current method in some of one bank on or off. Different torque curves depending on load, change from economy mode to power mode as needed. So many advantages, if the technology develops.
We have injectors that fire multiple times per piston stroke, so I'm sure we can actuate valves individually and with precise timing. The question is, can it be done for a reasonable price and is the benefit worth more than the cost? Take big ships engines for instance, they turn slow as hell so they're a natural, most of them have hydraulic exhaust valves these days I think. By the way, I heard they're building new cargo ships that will run on natural gas, gas being more plentiful, cheaper and light years cleaner than bunker fuel. While we're all paying high prices and taxes to supposedly clean up the air, one container ship belches out enough carbon and sulfur to equal a large city every year!
I may be corrected but I thought at least one of our high performance European car manufacturers were already using electric valves for 4 to 5 years now on certain engines.
sterman (Sp) technologies out of Colorado has been trying to get camless valves going for a while now since at least 2002. they were trying hydraulically actuated electronically comntrolled valves but they cant get it dialed quite right. To much stroke and pressure required to keep it precise for every single stroke of the piston. ITs day is coming but its much easier to control fuel with electrics because the amount of fuel is small compared to the force required to overcome a valve spring and move a valve. Plus of the injector hangs open it usually takes alot longer to destroy a cylinder kit than a valve would.
Renault has been tinkering with the camless concept for their formula 1 engines. http://scarbsf1.com/valves.html
I'm not a motor head, so take my thoughts with a grain of salt. And spark ignited petrol engines, I've never been a fan, I contend the only way to work on these things is pour diesel fuel on them and set them on fire. And I don't want to derail scrubs thread with an additional thought, but I think there's a degree of relevance. Most often, one of the goals in engine development is to make them more fuel efficient, well, that's a primary goal in recent decades. Since we're discussing the cam operated valve train, consider where that could be improved, i.e., where the cam valve train robs power from the engine. After all, when making an engine more fuel efficient, one of the ways to do that is eliminate things that rob power for the engine to operate, make it as free spinning as possible. So consider the cam valve train. Where does it rob power? It doesn't take much power to turn the cam, nor does the valves themselves have much friction in the valve guides, the power sucker is the valve springs and the power required to depress them. That's where I've always be intrigued by Ducati using the Desmodromic valve train in their motorcycle engines, the valve spring is done away with because they use an additional lobe on the overhead cam to lift the valve closed. This allows quicker throttle response, and a higher revving engine because it's impossible to "float" a valve with the desmo. These things give Ducati an "edge" with racing engines, but it seems to me it would make an engine more fuel efficient in civilian applications as the cam doesn't have to depress valve springs. But at the same time, I'm not naive, surely this isn't some hidden secret, surely someone has considered the desmo valve train for civilian petrol cars, there has to be a reason it's either not feasible, not practical, or simply wouldn't make a big enough difference. Just something I've thought about without doing research.
Yair . . . Gotcha willie59 Good points . . . and I will mention, I am never precious with threads, if it wanders off topic so be it. As with this one, I sometimes just put topics out there to create a bit of interesting traffic on the site. Thanks for all responses Cheers,
I recall International was trying to make it work 10-15 years ago as it was a natural fit because they were big into HEUI but it has been so long I completely forgot about it. You can bet that if it was practical somebody would be doing it because they are trying so hard to make emissions compliant engines these days and they and everybody knows that DPF/SCR is a big loser so they would love to get rid of that contraption if they could make the engines cleaner naturally.
That is a very interesting concept Willie, I've never heard of this design Ducati uses. Very simple design but it would seem like it would work incredibly well. Along those same lines have you seen the spherical rotary valves? http://www.coatesengine.com/csrv-advantages.html This also seems like an amazing design to me. But at the same time I remember reading about this same company and design over 10 years ago and still haven't seen one in a production engine.
Rotary valves might be a step in the wrong direction because their opening and closing rates are so gradual as that animation shows and cannot be changed. A cam can have the ramp rates mild or extreme as necessary, within limits. As above mentioned, one issue with hydraulic valve actuation I can see is that in a conventional camshaft, at least some of the energy is returned from the spring to the cam when the valve is closing. Just like when you turn a camshaft by hand. With hydraulic valves that energy would all be lost and it is significant. However, it has to still be better than dumping diesel down the tailpipe
I'd think any energy return on the back side of the lobe would be counter acted by the opening of the next valve. Also, the friction losses in a conventional cam system are significant.
One up, one down, it all balances out, minus friction like you said. However, a purely hydraulic system would be 100% loss, much worse.
Except that you'd be losing all the cam bearing and timing set friction. Also, the lifters will create friction in both directions so the valve closing event won't balance out with valve opening.
Hey Scrub, I enjoy your thinking out loud and sharing with us. I think being able to vary valve timing based on load and engine RPM would be a huge boost over our traditional cams as we know it today. The next step after that would be to shorten the stroke at faster RPM's when the high torque is not needed. Some creative engineering will be required to pull that off but remember all the worlds progress comes from non conforming "lunatics" as they are never satisfied to follow the standard. The world needs more lunatics. Guess this post shows that I don't sleep either. LOL, Big Grin.
Yair . . . old-iron-habit Good one mate. I probably spend far too much time thinking about stuff that is of little relevance but they reckon it's good to keep the brain active. It is also good to get so many responses to a thread that could have gone no where. There have been some interesting comments and thanks to all. Cheers.
That is an excellent question, Scrub Puller. What can be gained from electric-hydraulic valve actuation? Some small percentage increase in fuel efficiency? What is the down side? Total failure if a piston hits a valve. Cams and springs are *very* reliable.
infinitely variable valve timing and overlap. the ability's to change camshafts 1000x a min while driving. take your economy tuned motor and change it to a fire breathing MONSTER in .005 seconds.
Just look at the success honda has had with the very simple vtec system or gm's vvt. Both of those are fairly simple mechanical systems and are examples of how variable valve timing can work. I would imagine a spring return on the valve would still be used for simplicity. You'd only need a one way actuator and a quick bleed.
And to show that coming up with alternative methods to work valves in an internal combustion engine here's an example from years back: http://en.wikipedia.org/wiki/Knight_engine
kshansen, The successful sleeve valve design was the Burt-McCollum single sleeve. http://en.wikipedia.org/wiki/Sleeve_valve Developed by Bristol (Roy Fedden) first for the Hercules and Centarus aircraft engines, and used by Napier in the Saber, and Rolls Royce in the Eagle. The combined axial and rotational motion of the sleeve is very clever.
I think that the compression ratio needs to be increased *also* for a fire breathing MONSTER. 30 years of variable valve timing developments in IC engines have only shown small benefits. Advancing timing is routine, BMW did variable lift. It is precision motion at high speeds. One race engine cam designer says 'It's not eliminating valve train bounce; it's deciding how many bounces are acceptable... '
I used to potter about in a car 20 years ago that had the Vario Valve thing happening in the boot, all these things have been done years ago, even Atlas (think CAT 60 first Diesel here) had variable fuel and valve control done with wedge's? the future of the I.C. engine is not looking good, the Tesler thing will come top line soon I feel with the Sun filling the fuel tank. tctractors
good luck with the build bmw service
Very simple answer to all these valve problems: electrogravetics. As soon as this technology can be released by the corrupt govts., then it will change everything. Unfortunately, it will tear out the pockets of the huge oil producers, and the profits of the elite.....so, it will take a major world grass-roots rebellion to bring this technology out. In essence, you are tweeking the components of gravity to achieve power/lift. Gravity can be changed by modifying one if its three components. Ask Tesla, Leedskalnin, Paul LaViolette, Searle, Townsend Brown, and others. By applying an electrical charge to the leading edge of aircraft wings, you create an ionizing affect which eliminates all typical frictional forces and causes a pulling affect on the wing.....possibly applied on the B1 Bombers of today. Even us garage inventors can create an anti-gravity rig by using an old pc monitor's high voltage output line to send current down a very fine wire to a small light rig which will cause the rig to "lift" upwards, while creating an interesting "cold" spot under it. Also, at night you wee the ionizing affect glowing and making a hissing sound. Now, applying this to an old Case 580CK.............
"Tesler thing". Well said, tc!
jim D, the spelling thing is a bit crap for me as I border on being very thick, so its probably due for an A rather than an E in its name, a customer I was working for just the other day has bought 1 of these engine-less Cars, this man is a big iron lover who collects CAT's and anything oil soaked, he explained his reason for this not small £££ spend as investing something in the future helping towards the development of a long term answer to power the World, it would seem the I.C. power unit is facing the end game at a rapid pace. tctractors
Thats where turbo charging comes in. Staic compression ratios can be enhanced with turbo bost. valve timing is trivial Im talking about complete invinate adjustment of lift and duration...
TC, not to worry, diesel may be in short supply in the future, as I hear 100 octane avgas is getting to be for the big old warbirds, but we have several hundred years of known supply in natural gas, so we may have some spark ignited units running forever, or it seems I have heard tell of some mixed fuel engines, start on diesel and run on mostly natural gas with just the tiniest whiff of diesel through the injectors to provide the explosion? I remember when everything the world over was going to be run on turbines, cars, ships, home electric generators... turns out they're only really efficient when moving forward at several hundred knots to force air into them and even then they're horribly dirty throwing out tons of carbon from the incomplete combustion of kerosene. Point is I don't think battery operated will kill off the IC engine in our lifetime, maybe not our children's either.
Cummins was the one doing the compression ignition CNG engines. they werent all they were cracked up to be. Westport innovations was converting Cummins blocks to Spark Ignited CNG also not that great but better than the ones that relied upon compression alone.
100 Low Lead LL is being replaced with unleaded but we'll see some accidents very soon because engines will fail. 115/145 purple, Originally used as primary fuel for the largest, boost-supercharged engines needing this fuel's anti detonation properties. Limited batches are produced for special events such as unlimited air races. Reintroduced by Warter Aviation 2015. Link: Bunker fuel heating requirements Interesting article - skip ahead to page 17 to read about the engines fuel.
There is a company that has cam less valve engines and they use pneumatics off a belt driven compressor. Low production expensive cars, I can't remember the name something like koeningsburg. Vvt systems are just cheaper and work better and are already developed. I would still think it's the tech of the future for ice engines
Two strokes were replaced because of emissions, and fuels were replaced because of emissions. Now that we found cleaner fuel, lets go back to two cycles.
I think if you made a variable expansion pipe you could make two stroke great again. That or two stroke gas over electric as the two stroke only needs to run one rpm. My idea is to build a flathead straight 6 with port injection turning 1800 rpm gas over electric, thing will never die. Ice over electric kills any need for vvt