Engine developments

[Scrub Puller]

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.

 

[icestationzebra]

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

 

[JDOFMEMI]

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.

 

[lantraxco]

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!

 

[old-iron-habit]

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.

 

[Dualie]

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.

 

[DPete]

Renault has been tinkering with the camless concept for their formula 1 engines. http://scarbsf1.com/valves.html

 

[willie59]

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.

 

[Scrub Puller]

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,

 

[Birken Vogt]

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.

 

[LT-x7]

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.

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.

 

[Birken Vogt]

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

 

[chevota84]

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.

 

[Birken Vogt]

One up, one down, it all balances out, minus friction like you said.

However, a purely hydraulic system would be 100% loss, much worse.

 

[chevota84]

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.

 

[old-iron-habit]

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.

 

[Scrub Puller]

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.

 

[Jim D]

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.

 

[Dualie]

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.

 

[chevota84]

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.