Multipoint topic with optional questions and a blog link for added interest.
1) What are your views on Electronic solenoids operating valves, now that they are about to be used on affordable cars?
2) Technology of the future? and the extra efficiency of Solenoid petrol engines narrowing the gap, consigning Common Rail diesel, with all its reported woes to the dustbin of history?
3) Would you be among the first users of the technology? or will you stand back for a couple of years and see if there are significant problems?
4) Petrol or diesel with this new development?
tinyurl.com/54s3lj
Regards
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This will be fun! No cambelts to break. Just imagine a minor ECU glitch lunching all 16valves at one go!
Hit a pothole, disturb a dirty earth contact or even turn on the headlights at the same time as turning the steering wheel - (see the thread re Fiat power steering pump problems with headlamp flicker). That will be £5000 sir for a new engine. No the warranty does not cover it, because you drove over a road hump too fast. (All details recorded from the onboard accelerometers).
pmh
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I'm somewhat on the fence on this.
I think new technology is great, and I'll be following the development of this idea with interest. We'd still have atmospheric inlet valves if we left it to the luddites.
I wouldn't want it on my car now, or for the foreseeable future without cast-iron guarantees, or years of proven reliability.
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I think it's a muscle twitch from a decaying corpse. The petrol engine is doomed - diesels are more relaxing to drive and still offer better economy than these diddy petrols.
Not poking fingers but oilrag in particular has a very poor opinion of modern diesel reliability... well, I'd hate to be the person diagnosing a glitch in this. It seems to be massively-overcomplicating the engine for a mediocre benefit.
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...although saying that I think it's a very interesting idea and I'm happy to be proved wrong.
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Reply from HJ in the Telegraph:
"Unfortunately, the amount of technology added to diesel cars over the past eight years has made them increasingly unreliable. Dual mass flywheels employed to dampen the excessive vibrations of common rail injection are failing regularly after only 35,000 miles and the cost of rectification is usually the wrong side of £1,000. My information, gleaned from more than 400,000 emails, is that diesels are now potentially so costly to repair that any potential fuel and tax savings are wiped out. Against your anti-hybrid argument I can present the Lexus RX400h, a large SUV that offers V8 petrol performance and about 33mpg economy."
Still think diesels are the future?
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"400,000 emails"
That's what I call a survey!
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Electric solenoids offer great potential as a replacement over camshafts. Variable valve timing to suit engine load and conditions would be a simple enhancement. You could also disable individual cylinders to improve economy under low load conditions - just open valves slightly to reduce pumping losses and stop injecting fuel.
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"open valves slightly to reduce pumping losses"
Wouldn't keeping them shut work better?
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It's a great idea, and in theory should give engines with completely flat torque curve across the rev range and drastically improved economy.
However, any failure is going to be both very spectacular and very expensive. Even if the solenoid sticks slightly rather than outright fails, you're looking at mechancial catastrophe. There's not exactly much leeway on an engine running at 6000RPM.
Cheers
DP
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"diesels are more relaxing to drive"
Only if you're deaf and have no sense of smell! :-)
I had the idea of solenoid valves some years ago (not the first, I don't suppose, but before it was mainstream) and it seems eminently sensible to me. You get desmodromic action built-in, as much variable timing as you want and no worries about adjustment. However, it does depend on rather well-sorted electronics and, preferably, non-interference engine design (like my Mazda). A few early expensive engine replacements could kill it dead!
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Does F1 technology use pneumatic operation? I vaguely recall seeing something about it.
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"open valves slightly to reduce pumping losses"
Wouldn't keeping them shut work better?
I was thinking about reducing the compression load of a pumping cylinder that wasn't being fuelled.
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"reducing the compression load"
Sounds reasonable. I simply don't know what the optimum setting would be, and I imagine that solenoid valves will only have two positions!
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The real question must be whether the improvements in efficiency from the greater control obtained, can obviate the need for interference designs. This could be a good starting point. However we all know that organisations have no (or very little) corporate memory and it will only be a matter of time before interference designs are back on the drawing board, driven by accountants and a need for even greater efficiency.
pmh
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"driven by accountants"
That's all right then. I don't mind them getting stranded.. :-)
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The reason that valves are wrecked with conventional cams is that the valve CANNOT move when it's hit by the piston. If the valve is opened by a solenoid, then it CAN move when hit by the piston - and the ECU should be able to detect this and react accordingly. Damage should be much less, and probably not significant.
Personally, I think this technology could work well in both petrol and diesel engines. We are still a very long way from efficient engines - especially in low speed traffic when the engine is powering auxillary equipment rather than the road wheels.
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"Not poking fingers but oilrag in particular has a very poor opinion of modern diesel reliability"
I Don`t know about that David. Concerns about mis-fueling and buying used, yes. But I`m a big fan of Fiats 1.3 Multijet and own one.
That said, If I could buy a new car today with a Perkins Prima, as it was in 1991... I could accept the slow pace for that rock solid mechanical injection system.
However you all know I dislike cambelts..But thinking of Electronic solenoids is giving me a U turn ;)
Regards
Edited by oilrag on 28/04/2008 at 14:20
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On the same subject, I've always thought that poppet valves are not a very elegant solution in internal combustion engines. This link illustrates a rotary valve which would work very nicely :
www.coatesengine.com/rotary_motor.html
Combine that with electrical actuation to make rotational speed independent of crank speed (to achieve different inlet/exhaust timing) and you'd have a very neat design solution. It would also eliminate any risk of pistons hitting valves.
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I would imagine that if the valves were solenoid driven instead of by a camshaft, the direction of travel no longer needs to be parallel to the cylinder stroke, they could also make them so that they don't protrude so far into the cylinder, if at all. For example a slider opening a port. Don't forget, this will allow valves to open and close much quicker and for a shorter duration than the almost sinusoidal way they do now.
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Speaking as a non-engineer, my intuition is that the Coates engine would be unhappy at high revs, indeed unable to attain them, and that wear and leakages, not to say overheating, on the exhaust side would soon constitute a problem.
Poppet valves opened by a cam and closed by a spring are tried, tested and highly developed. The only recent developments of any value are hydraulic tappets (to reduce the need for routine adjustment in cooking engines, although they can cause problems in very highly tuned ones) and variable valve timing. Neither is essential for reasonable efficiency. VVT like any desmodromic system of positive valve closure - theoretically useful in very high-revving applications - is going to cause maintenance headaches sooner rather than later I would say, unless you see an engine as a throwaway unit only good for 100,000 miles or so. Of course owners of cars with these features may wish to correct me.
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I wonder what current is needed to open a valve?
To operate it quickly the number of coil turns has to be restricted. Otherwise there is too slow a build up of current in the coil, due to inductive lag. Less turns means more current for the same magnetic force.
Presumably the spring pressures for electrical use will be much the same as when using a cam because of the need to close the valve quickly.
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Presumably the spring pressures for electrical use will be much the same as when using a cam because of the need to close the valve quickly.
wouldnt it be possible to use reverse current in the solenoid to close the valve instead of relying on a spring to do it? just a suggestion...
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i can vision it now... removing the rocker box cover to reveal nothing more than banks of solenoids and some wiring, No cams or lifters or black oily tar or tappett clearence to fluff about with.....heaven, or has it already been done and kept locked away by the big car companies?.... while were on the issue of failing cam belts why didnt desmodronic valve technology catch on?
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"a rotary valve"
That's elegant, although the valvegear would be rather large and require some heavy-duty seals, I imagine. One of the advantages of poppet valves is that the major force they have to resist (ignition) works to keep them shut! The Wankel engine is a neater solution than either, IMHO, as the rotor is both the piston and the valve(s).
www.myrctoys.com/engines/wankel.swf
Then there's the Wolfhart engine...
saturn.spaceports.com/~wolfhart/motorus.htm
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"diesels are more relaxing to drive" Only if you're deaf and have no sense of smell! :-)
My sentiments exactly. I was standing near a brand new BMW 335d recently when it started up and idled for a while and it was much noisier than my 2.0 petrol Focus.
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surely a V6 petrol auto is far more relaxing and rewarding to drive than any diesel, as long as you don't let your mind wander to the cost...:-)
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This has been asked before a couple of years ago there are a few large marine diesels around that are camless using solenoids
As ive said time and time again, large plant engines get it first, Then the technology is put in cars and called "new"
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but don't large marine diesels run at just a few hundred rpm? When I say "large" I mean "LARGE", supertanker stuff.
JH
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but don't large marine diesels run at just a few hundred rpm?
The one I was on peaked at 112 RPM - it almost self destructed at 93 RPM and had to pass through that quickly (relatively speaking).
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This one only manages 102 rpm....
people.bath.ac.uk/ccsshb/12cyl/
... but does produce 108,000 horsepower in the process - without any valves at all.
Edited by Screwloose on 28/04/2008 at 21:37
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How do you start it?
Compressed air timed & injected into cylinders
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but don't large marine diesels run at just a few hundred rpm? When I say "large" I mean "LARGE" supertanker stuff. JH
So what if they do. If they go wrong in a force 10 and your a couple of miles off land your in deep trouble
If your solenoid system went wrong on your car whats the consiquences? late for work?
There are some solenoid valve & injection system on higher speed diesels
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Re: Screwloose's link, those figures are just mind boggling.
A 300 ton crankshaft, and 5,608,312 lb/ft of torque - in a word, wow!
Cheers
DP
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What about the tools and machinery used to make it?
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......... lb/ft of torque ..........
lb.ft or lb ft or lb-ft
I prefer lb.ft as the full stop indicates (correctly) that the lb component is multiplied by the ft component. See tinyurl.com/5jyp9l for further information on units.
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>> ......... lb/ft of torque .......... lb.ft or lb ft or lb-ft
Makes perfect sense, but in my defence, this was a straight copy/paste from the website.
Cheers
DP
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"5,608,312 lb.ft"
If true, that roughly equates to the leverage you would get by applying half a ton of force to a mile-long spanner. I wonder what they do up the propellors with..?
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