The electric version has been done by Renault and I'm sure others. However, like the compressed air supply, the electric power draw on the solenoid driven system is very high.
Both air and electric give insane amounts of driveability and valve timing options, but you have to know what you want because there are some many possible iterations.
I like the smaller packaging.
cwh wrote: I think a very interesting possibility with this system is the ability to change "Cam" timing. Granny style when wanted, aggressive when desired. Change the entire personality of the engine to match the needs.
That's not an interesting possibility, that's the whole idea.
VVT. Most modern engines have it.
My point was that engines are still getting along with a simple spring to close and a cam to open. When a pushrod engine can turn 9K+ rpm. so where is the need ?
iceracer wrote: VVT. Most modern engines have it. My point was that engines are still getting along with a simple spring to close and a cam to open. When a pushrod engine can turn 9K+ rpm. so where is the need ?
In other words "Get a horse?"
This is one of the bigger developmental progressions of the internal combustion engine since they began.
iceracer wrote: so where is the need ?
Increased efficiency and the need to meet fuel economy and emissions targets.
Having total control over valve events will do that for you.
iceracer wrote: VVT. Most modern engines have it. My point was that engines are still getting along with a simple spring to close and a cam to open. When a pushrod engine can turn 9K+ rpm. so where is the need ?
VVT only does so much. You are still using cams. They open valves progressively rather than snapping them near-instantly between full open and full closed. You can adjust the timing of when they open and close, but you can not make them stay open for longer. Most variable cams are still step systems. They bump timing at certain RPMs. Each profile bump will still be most efficient at one particular speed.
This system gives you the power to optimize what the valves are doing for every possible RPM and load.
Does the current system work? Sure. Valve timing worked fine before VVT. VVT is not necessary, but it is definitely an improvement. If they iron the bugs out of this, it will be an even bigger jump in engine efficiency (which can mean saving fuel and/or raising output) than what that gave.
Go back and re-listen to the part where he talks about the valve opening profile. At that point he also talks about the limitations of VVT.
iceracer wrote: VVT. Most modern engines have it. My point was that engines are still getting along with a simple spring to close and a cam to open. When a pushrod engine can turn 9K+ rpm. so where is the need ?
VVT is only a very small part of what this is all about. VVT doesn't control lift and duration, ramp rates, timing events between cylinders, and even timing events between individual valves within a cylinder. It only controls the cam phasing in relation to the crank, and on dohc engines, the cam phasing between the cams, in relation to each other, and the crank position.
This would enable complete control of all aspects of all valve events at all times. To grossly oversimplify, you could have very short duration, low lift valve events with very fast ramp speeds, very high efficiency. and excellent fuel economy at low speeds, then completely the opposite with the push of the accelerator pedal.
Zomby Woof wrote: This would enable complete control of all aspects of all valve events at all times. To grossly oversimplify, you could have very short duration, low lift valve events with very fast ramp speeds, very high efficiency. and excellent fuel economy at low speeds, then completely the opposite with the push of the accelerator pedal.
The improvement in effiencey or cleanliness isn't as clear cut as you imply. Especially calling it "very high efficiency"- one still needs to throttle the air to restrict the power output- these are not diesels, they are air metering controleld devices. No real way around that. VVT systems with decent cam timings already can deliver combustion where throttling losses are very very low.
Second, low engine speed does not always mean good combustion efficiency. At low speeds, the actual combustion physics slow down enough that it starts to cause measureable physics problems in combustion.
The real measure for a technolgy like this is the ACTUAL impriovement compared to the cost and complexity that is being introduced.
Beer Baron wrote: Most variable cams are still step systems. They bump timing at certain RPMs. Each profile bump will still be most efficient at one particular speed.
Most are not- most VCT systems are continously variable set ups. The one hold out is Honda's VTEC system, which is the choice between two sets of lobes. Timing is always in motion depending on the speed, load, and desired operation that the driver wants.
I've been working with VCT systems that let me continously set the advance degree for quite a while now. Probably 3-4 years on systems where it's totally independant intake and exhayst timings. And note that we are not exactly on the leading edge of hardware technology in terms of timing.
Systems we seem to easily get have 60 deg range.
It seems to me that at least you would reduce your pumping losses. You wouldn't need throttle plates.
I think some BMWs are already throttle plate-less. I may be wrong on that.
Rob R.
In reply to alfadriver:
Please note phrase "to grossly oversimplify".
It's comparative. I was referencing the huge efficiency losses at low RPM required to enable big power at high RPM with what we currently have.
In reply to Zomby Woof:
Grossly oversimplity = grossly overestimate the problem?
There are not really huge efficiency losses at the low end, so there's not that much to gain. Again, VCT can enable better low speed combustion and get high speed efficiency. How much more can this get- who knows?
wvumtnbkr wrote: It seems to me that at least you would reduce your pumping losses. You wouldn't need throttle plates. I think some BMWs are already throttle plate-less. I may be wrong on that. Rob R.
That's already being done with VCT. BMW adds variable lift to eliminate the throttle. although without vacuum to power things, it brings in a new set of problems. Solveable, but many here seem to not like electric boosted stuff.
Pumping losses are already a small part of the game. It's an easy target, though.
I'm not saying that a system like this can't be good, I'm wondering what the benefits actually will be, not theoretically. Measureable.
We have had prototypes with the electric version of this, and, well... Not even BMW has tried to put that into production. That's not even thinking about the full range operation that is needed for production cars.
They need to publish some SAE papers, not videos on youtube.
Tell me about a naturally aspirated application that makes big power at high RPM, and excellent fuel economy on the bottom.
I think this idea is pie in the sky anyway, but if it did work, it would blow away anything we have now.
alfadriver wrote:wvumtnbkr wrote: It seems to me that at least you would reduce your pumping losses. You wouldn't need throttle plates. I think some BMWs are already throttle plate-less. I may be wrong on that. Rob R.That's already being done with VCT. Pumping losses are already a small part of the game. It's an easy target, though.
Taking out the throttle plate doesn't necessarily reduce the pumping losses. It can, based on the shape of things, but there is still an intake restriction - in the case of BMW its the valve.
In this engine it would be the valve as well. What I think is interesting is you could run the faux atkinson cycle for economy and switch to otto cycle when power is needed.
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