[SPIKE ARRESTOR]

Originally Posted by tsk1979

What has 4x4 got to do with all this.

4x4 has nothing to do directly, what I meant was how will a user see all this gadgetry / electronic paraphernalia if the application is more abusive.

Originally Posted by SS-Traveller

How would one be able to change the stroke of an IC engine at will? AFAIK the stroke is invariably related to the crankshaft offset. What has camless valve actuation got to do with it?

+1

Spike

PS- Wonder why 4WD enthusiasts / purists prefer the good old Mechanical shift transfer case.

[Sutripta]

Originally Posted by SS-Traveller

How would one be able to change the stroke of an IC engine at will? AFAIK the stroke is invariably related to the crankshaft offset. What has camless valve actuation got to do with it?

OT, but there were a few proposed mechanisms. And IIRC, either Saab or Volvo had even made a working prototype.

What I think Tanveer is referring to (and has been pointed out by Pranav) one can change dynamic compression ratios. In fact play around with different CR and ER. Can be used to advantage.

Regards
Sutripta

[SS-Traveller]

Originally Posted by Sutripta

OT, but there were a few proposed mechanisms. And IIRC, either Saab or Volvo had even made a working prototype.

I see.

Originally Posted by Sutripta

What I think Tanveer is referring to (and has been pointed out by Pranav) one can change dynamic compression ratios. In fact play around with different CR and ER. Can be used to advantage.

That is quite possible with solenoid actuated valves - it's the change in stroke length that confused me.

[tsk1979]

Sutripta understood what I meant. Yes, thinking of it now, to change stroke length the piston rod will have to change length. This is quite bit more complicated.

[pranavt]

I believe the working prototypes involved moving the mains up/down depending on what you wanted to do to the compression. Mains meaning the main bearing supports on which the crank rotates.

[vina]

Originally Posted by tsk1979

In modern engines, many jobs earlier done by mechanical parts are now done by electronic ones. For example, now you have electronic fuel pumps, ECU to control fuel and air mixture etc.,
However, in one area, its still all mechanical. There have been experiments, but nothing concrete has come out.
That is the area of Cams and Valve timing.

I tried searching the net, and most articles are pretty old, and list several disadvantages of using solenoid valves, controlled by a ECU for timing etc.,

The drawbacks are listed as difficulty of operation at speed, high fuel consumption etc.,

However, these articles are from 2007 or older.
ECU technology has come a long way, and today for the same price you get much faster and more durable processors.

So why is the technology not picking up. It will definitely remove lots of components like timing chains/belts, cams etc.,

All you will have is a set of solenoids controlling the valves, and a dedicated ECU. No more timing belt nonsense.

Even high speed engines going 10,000 rpm, its no big deal for todays processors. We are in the era of Giga flops.

Even solenoids are a lot better and faster than what used to be in the market 5 years from now.

So while lots of companies like BMW, Renault, Mercedes are apparently experimenting, this is one area where there is no "buzz" or excitement in the auto world.

When MPFI and CRDI came out, despite of many naysayers who swore by the carburettors and how ECUs will fry in those extreme temperatures, there was lot of excitement, and engine technology grew leaps and bounds.

However, replacing this mechanical domain with electronic, there is more smoke than fire.

As an electronics guy, I would prefer everything which can be made electronic to be made electronic.
Reasons are simple
1. Hardware is cheap and can last 10-15 years before failure, if proper quality control is used
2. Will reduce the weight as well as cost
3. With an ECU, no more complex circus required for variable valve timing. you can literally advance and retard timing as per need on the fly.
4. It will enable simpler variable compression engines.
5. Theoratically, it will enable you to create a variable stroke engine. I am not sure about this, but looking at how an otto engine works, if you could operate valves at will, you could change length of the con-rods on fly and have your engine long or short stroke.

As for disadvantages, wikipedia will give you a list, but does not tell you why. Nor do the internet links tell you the "why" of those disadvantages.

Any engine experts care to comment?

I don't know about engine experts, but I'm an electronics expert and here are my comments:

1. solenoid actuated valves have to be magnetic. and most magnetic materials lose the magnetism at high temperatures (the few that don't are expensive) - so exhaust valves are likely to be tricky.
2. While solenoid will probably NOT take more power by itself, based on the stiffness of the springs in the valves large currents will be required to turn on/off the valves. Again large current by itself is not a problem, the problem is that in the presence of inductance sudden changes in current are very hard to achieve (harder still if the current in question is large to begin with). And better solenoid = larger inductance. Thus overall system will be highly complicated and probably power hungry.
3. The above will also increase the cost along with another reason: Electronics reliability sucks (sorry tsk1979 - this is true and this is coming from a guy who wins his bread by designing high reliability electronics). As an electronics designer myself I would try NOT to do anything electronically unless there is a very good reason. Let me explain:
   1. ICs for consumer systems are designed to work from 0C to 85C. Industrial systems for -20C to 85C and military grade is -40C to 125C. As you can see except for the military grade stuff nothing else suffices near an engine (ECU is kept inside the driver cabin - it never looks at such temperatures).
   2. The "giga-flops" stuff is especially fragile, though you may not need it anyway.
   3. Boards get corroded very easily under hostile environments - making them immune is immensely expensive. Even dust is a killer and stuff such as sulfides are deadly.
   4. Slightest vibration can make circuits malfunction - silicon is a weak peizoelectric by itself and under stress generates voltage differences. For most applications this is not a problem - ICs in your cellphone hardly see much vibration. for engine compartment it wouldn't work.
   5. Fossil fuels being what they are, they come from deep down the earth and invariably carry some radioactivity. This will not even shorten the lifetime of an ant, but the alpha particles can cause modern day digital circuits to malfunction (nuclear-cable aircraft and missiles use especially designed chips with high amount of redundancy for this reason. All avionics also uses radiation tolerant chips)
4. On top of that things are not what they seem to be:
   1. while 6000rpm is merely 100Hz, assuming you want to control valve timing with a precision of 5degrees (very routine in mechanical design I guess) you are actually dealing with a time resolution that you can get only with 720Hz (100* 360deg/5deg. Next something called Nyquist theorem will require sampling at at least double that much and then some (for relatively simple implementation) so it goes 2kHz. So the solenoids have to be actuated by a high current driver that has a bandwidth of at least 2kHz (and probably more). This is like having a good audio amplifier with very high output current rating (imagine 100W or more of continuous power - equivalent to 1kW PMPO), and you know how much those costs.
   2. If you are going orgasmic over multi-event per cycle valves - increase the bandwidth requirements in the above and have fun with the cost.
   3. The control system for this will be complex - ECU that controls your air/fuel injection etc. in MPFI and CRDI is a very low bandwidth system compared to what you just read. It also doesn't do much in calculation (most of its work is picking up best points from a table). This works normally because when you press the pedal if the ECU takes time to change the fuel amount to be injected and misses a few shaft resolutions (it'll miss a lot many more than a few) - that is not a problem. But a fully electrical (better description than electronic - there are solenoids after all) system would have to work faster than the engine itself. Such complex control systems are entirely possible but they are not cheap and non trivial (this kind of stuff is not windows programming - this one requires advanced maths)
   4. I'm not sure why wikipedia mentions noise - though given that we enter the realm of audio frequencies and very high currents, I wouldn't be surprised if the magnetic fields cause other stuff to vibrate and cause noise (you can hear high power transformers making hummin sound even though there are supposedly no moving parts - and I'm not talking about the fans in their cooling systems here).

Frankly I don't think this is ever going to happen. If you decide to fix your rpm to a narrow range then cams can, I guess, be optimised very well (they'll work well only in a narrow range, but that's all you would need). And once you do that then for less complexity and far-better reliability you can have an engine-generator-electric motor setup with electric motors running each wheel independently - no axle at all 4x4 vehicle with much reduced transmission losses, far better efficiency in the internal combustion engine itself, and easier more optimised suspension. Even if you don't do the each-wheel-to-its-own-motor bid and keep the axles etc. this is still a better solution.

[vina]

Originally Posted by SS-Traveller

Point taken. But then the operational parameters of a marine engine are vastly different (and 100x bigger) than any engine in automotive use. Again, marine engines have moved on from using fossil fuels to nuclear - probably another scary scenario for us right now, but in the future one can expect the world to run out of fossil fuels and switch over to alternate (read: nuclear) power sources.

If camless technology is not running in F1 engines now, we don't expect to see them implemented in road-going cars even 10 years into the future. But the IC engine has been partially replaced by the electric motor quite successfully, and I expect to see the IC engine missing from under the bonnet of my car completely before the camshaft makes itself scarce.

Ships will not go nuclear any time soon except for naval applications (submarines are already going back to diesel - nuclears are much more easy to detect due to vibrations and stealth matter more these days) however your comment on IC engine disappearing may be bang on except perhaps for long distance and heavy duty vehicles (where the engines are already very efficient)

[vina]

Originally Posted by sindabad.sailor

Hello all,

Apologies as I am an automotive novice tryping to peek into the subject.

However I currently am sailing on an absoloutely electronically controlled engine driven huuu...ge ship.

This engine 6S60ME-c meaning 6 cylinder, S-superlong stroke, 60 cm bore, electronically controlled marine engine is designed by MAN B&W built at Doosan Korea is doing great service to worlds most talked about hyper sized LNG ships on which I am sailing for over 2 years now.
In fact the ship is a twin screw ship meaning sails on two propellers (which work on the screw principle) and hence there are two eninges in the ship each of 18500KW capacity.

Having worked for some time on conventional cammed engines, this camless engine is a gem amongst all engines I have sailed so far.

I haven't experienced any of the proposed fears translating into reality in these years except a typical problem which was more due to faulty design than engine's being camless.

The exhaust valves have a capacitance type probe that measures the stroke. Earlier generation probes had comparatively slow response time and hence I often used to get Exhasut Valve Low stroke Alarm and eventually engines used to slow down automatically as a safety. However the manufacturers supplied improved probes and this problem is no more recurring.

Apart from this I did not have any single issue.

Advantages:

Marine fuel oils can have sulphur content upto 4% (allowed 5%) This upon combustion can cause generation of sulphuric acid vapours within the cylinder corroding it severely. To encounter the same the lubrication for the liner is supplied by injecting alkaline Cylinder Lube OIl of TBN 70. This oil costs fortunes and with ME-C engines specific LO consumption is substantially lower. Since ships are run for upto 30 years, the economics tilts in favour of electronically controlled engines.

Another big advantage is that shipping industry too is pressed hard for environmental norms under discussions. Since these norms are coming in succession to meet these norms a normal engine would require extensive hardware change. However with electroniclly controlled engines just a change in logarithm can change the injection characteristics and patterns hence would sure rule the marine engines of future.

Apologies if my explanations are bit OT. But I thought it could be relevent.
What I wanted to stress is that the fear about all electronically controlled engines is uncalled for.

Rgds and many thanks.

Very good comments from an actual application, however as SS-traveller wrote, your engine is very different from an automotive engine:

1. The rpm you deal with should be very very low (I would be surprised with 200rpm). As you can see this means
   1. the springs on the valves need to be comparatively much less stiff than in an automobile engine that'll do at least 4000rpm - reducing the requirements on solenoid (in proportion to engine size).
   2. Also lower rpm means that your frequencies of interest are in the range of 1-3 Hz, very low indeed and the processors can easily compute whatever they need.
2. Your systems are large so even a huge electrical control system will seem very small to you. Now an electronic control system's size will be determined entirely by that of the signals fed to it and the response desired - not by who (or what) is feeding those signals and what is being controlled - on that note the size of your control system will most likely be smaller than that of a car with similar reliability etc. The actuators will surely be bigger (because the valves will be bigger) but due to the reasons mentioned above, the actuators will still be smaller, when engine size is taken into account, compared to a car engine.
3. In your application even high-reliability expensive and highly redundant electronics will not cost much (as a fraction of total engine cost)
4. changing the algorithm (I think that's what you meant, instead of logarithm) of timings etc. is much easier in your engine - low rpm means low piston velocity and much more predictable heat and mass flow - than in an automobile engine running at high rpm. Also even if you know what new algorithm to use, implementing it requires even more complex actuators and control systems as I mentioned earlier.

[SPIKE ARRESTOR]

Originally Posted by vina

I don't know about engine experts, but I'm an electronics expert and here are my comments:

Vina good to have you here. Reading a very informative post after a very LONG time indeed! Being a Mechanical guy, I thoroughly enjoyed reading this post of yours.

solenoid actuated valves have to be magnetic. and most magnetic materials lose the magnetism at high temperatures (the few that don't are expensive) - so exhaust valves are likely to be tricky.

Which are those few? Would like to know.

The above will also increase the cost along with another reason: Electronics reliability sucks (sorry tsk1979 - this is true and this is coming from a guy who wins his bread by designing high reliability electronics). As an electronics designer myself I would try NOT to do anything electronically unless there is a very good reason.

+100 couldn't have agreed further, being from Automotive background, I happen to see this very frequently. This is precisely the reason for my post regarding 4x4 / abusive application in automobiles.

Boards get corroded very easily under hostile environments - making them immune is immensely expensive. Even dust is a killer and stuff such as sulfides are deadly.

Agree.

Slightest vibration can make circuits malfunction - silicon is a weak peizoelectric by itself and under stress generates voltage differences. For most applications this is not a problem - ICs in your cellphone hardly see much vibration. for engine compartment it wouldn't work.

Agree again.

Fossil fuels being what they are, they come from deep down the earth and invariably carry some radioactivity. This will not even shorten the lifetime of an ant, but the alpha particles can cause modern day digital circuits to malfunction (nuclear-cable aircraft and missiles use especially designed chips with high amount of redundancy for this reason. All avionics also uses radiation tolerant chips)

Interesting info.

And once you do that then for less complexity and far-better reliability you can have an engine-generator-electric motor setup with electric motors running each wheel independently - no axle at all 4x4 vehicle with much reduced transmission losses, far better efficiency in the internal combustion engine itself, and easier more optimised suspension.

Well said Sir!

Originally Posted by vina

Very good comments from an actual application, however as SS-traveller wrote, your engine is very different from an automotive engine:
--------

Useful info!

Spike

[julupani]

@pranavt

True, the only place you can think of changing out half the engine to change CR is in racing, but racing doesnt need to change the CR in the first place.

There have been a few prototypes made for variable CR, most of which have used two ideas. One is to have sort of two sets of MB on a crank, allowing for the a change in stroke length. But this means the maximum angle between the piston and the conrod will change, and thus risk the con hitting the cylinder walls, unless done very carefully. The other more common idea, is to use a completely movable cylinder head. The complete head with the whole valvetrain and injection systems, has a couple of positions offering two separate CRs. Both kinds of ideas require highly complicated designs, not yet very reliable.

[vina]

Originally Posted by SPIKE ARRESTOR

...
Which are those few? Would like to know.

...

Spike

You can search for "high-temperature magnets" The relevant material here will be Samarium (alloyed with cobalt) and Neodymium magnets may do on the intake valve.

Both come mainly from China. In fact China has been controlling supplies for months (after the incident last year in which a Chinese fishing boat rammed Japanese naval vessels China effectively stopped supply to Japan and had not resumed until the earthquake - I don't know the status now) for everyone else in the world.

An upcoming rare-earths factory in Malaysia may relieve the situation in a few years.

I automotive space, companies are steering clear of permanent magnets as a result wherever they can - Tesla and others use induction motors with excited core (although this may have to do with controllability of motor too, their stated aim is to not rely on permanent magnets)

[sudev]

@tsk1979 : You started a storm in tea cup. Very interesting discussion. I need to punch a thanks button on you for that right after this.

OT: Why is every one assuming engines have to run high RPM's?? Lower RPM engines are more efficient. So why not run them in the band where efficiency lies? Use gearing to take care of speeds. Or my assumption of low RPM = better efficiency wrong?

Only problem I see is engine area/volume to output multiplier. (Smaller engine @higher RPM --> More power per volume vis larger engine at lower RPM).

[vina]

Originally Posted by sudev

@tsk1979 : You started a storm in tea cup. Very interesting discussion. I need to punch a thanks button on you for that right after this.

OT: Why is every one assuming engines have to run high RPM's?? Lower RPM engines are more efficient. So why not run them in the band where efficiency lies? Use gearing to take care of speeds. Or my assumption of low RPM = better efficiency wrong?

Only problem I see is engine area/volume to output multiplier. (Smaller engine @higher RPM --> More power per volume vis larger engine at lower RPM).

Nobody is assuming engine has to be run at high rpm - tsk1979 mentioned it as an advantage of the electronic control ("... 10000 rpm ...")

For automotive engines (indeed in almost every application of internal combustion) power/weight ratio and compactness are important.

For any given efficiency number state of the art of material science and fuel properties limit how much energy you can generate from one full 4-stroke (or 2-stroke) cycle from an engine of a given volume. So for a given size/volume of the engine if you want more power, your option is pretty much limited to higher rpm.

Lower rpm, large size, higher compression engines (as is the case with the marine engine in the threads above) are indeed more efficient - but impractical for automobiles, though rpm by itself doesn't imply high efficiency.

[cranky]

@vina: Extremely useful post. Nice to have someone here who can help improve my electronic knowledge, as it's an area of interest for me.

There is also the problem of an inductor needing quick saturation with high startup current.

There is the second issue that 6000rpm you are dealing with 100Hz for a single valve - but with 8 of them that is 8 streams of high power control system - electrically this is difficult to meet given that a typical 12V battery will not power that kind of array for very long.

One more issue is that the valve head actuators are typically lubricated. An actuating solenoid itself will need to mechanically or electrically be in a sealed system, which further complicates the coupling design.

I'm guessing F1 can afford the costs of developing technology like this and at 20k rpm things change significantly enough. I wonder how they power the array though - I think it's primarily a hydraulic system, with only control input from electronics.

[tsk1979]

Originally Posted by vina

Nobody is assuming engine has to be run at high rpm - tsk1979 mentioned it as an advantage of the electronic control ("... 10000 rpm ...")
.

I was simply referring to articles which said high speed applications have trouble with electronic valve timing.
Low speed engine do not have those problems.

That said, won't using electromagnets solve the rare earth problem to a degree?

About reliability of electronics, I would disagree. Its more of a QC issue than a design issue. Military grade electronics and chips are still manufactured and can run in adverse conditions.
Even normal chips are taped out with an aim of 125-130 degree operational parameters. However to cut costs the casings are cheap quality which cannot withstand those temperatures.
In an expensive automobile a few dollars/chip will be acceptable.

Already we have components like cam sensor and sensors in the exhaust circuit. Exhaust circuit sensors run at much higher temperatures.

The biggest drawback i could see is the magnetic valves, as you mentioned. I am not well versed with electrical engineering, so you are right, there may be many problems in those areas. However, as far as ICs are concerned, its easy in current tech to manufacture chips which can survive 200 degree C temperatures without skipping a heartbeat.
Even consumer grade hardware like GPUs touches 100-110 degree C before thermal shutdown algos kick in.