back to article Lasers set to replace spark plugs in car engines

Spark plugs in petrol engines are set to be replaced by laser ignition systems, following development of new manufacturing techniques by Japanese boffins. The new research is to be presented to the world at an optics conference in Baltimore next month by Takunori Taira of Japan's National Institutes of Natural Sciences and his …


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  1. TeeCee Gold badge

    " in years to come..."

    Not good enough!

    I want my car with frikkin' lasers on it NOW!

  2. Alister Silver badge

    Enquiring minds want to know...

    as these new "frikkin' lazoors" are deemed hardy enough for automotive use, are they now small enough and tough enough for reliable piscene cranial applications?

  3. hplasm Silver badge

    Diesel is only dearer than petrol

    Because the taxman makes it so.

    I want some of these sparkplug lasers though.... for er, my central heating, yes.

    (Not the shark tank...)

    1. Andy H

      Surely you mean

      Selachian cranial applications?

    2. fridaynightsmoke


      Diesel and petrol are taxed at the same rate as each other in the UK, diesel is more expensive because there is much higher demand for diesel (think >1/2 of all cars, and all vans & lorries) than petrol, and a given barrel of oil produces more petrol than diesel (without additional expensive refinery gubbins thrown at it). The UK currently exports petrol, and imports diesel.

      Thats why.

      /flames for fuel, not for you :)

      1. Alister Silver badge

        Budget cuts

        Can't afford Capex for sharks, so we're looking at pike or barracuda instead to populate our new, efficient "dangerous swimmy thing" tank in the Fortress OF Doom...

      2. Dom 1

        Another Factor

        There is another factor too, as to the price difference.

        Diesel is (nowadays) much more polluting than petrol. The levels of PM10's and PM2.5's created by diesel engines are huge - even with particulate filters in the exhaust. The PM's are [mainly] hydrocarbons made of Benzine rings (a known carconagen).

        Hence the EU decided (in the clean air/pollution laws) that because of the pollution created by diesels, the tax levied should be higher [than petrol]. Alas, only the UK abides to this (other EU countries ignore the law because diesels are much more popular on the continent than in the UK).

        If you follow the history of diesel vs petrol prices, you will note that after the EU laws kicked in at the turn of the century (2001 to be precise, and coincided with VED - Road Tax - changes), diesel cost has overtaken petrol.

        1. Anonymous Coward

          This is true !

          By taxing the car that is 'more polluting' it will become much cleaner. You should apply for a seat in the Euro parliament forthwith. We need more people like you !

        2. Anonymous Coward
          Anonymous Coward

          Shark downsizing

          Plus sharks are on the endangered species list... the paperwork to get them would be insane. Instead we have... sea bass.

          They are ill-tempered, though.

        3. Anonymous Coward
          Anonymous Coward

          Benzene not Benzine

          That is all

          1. Alister Silver badge

            Middle Management

            will soon have us down from

            "The Shark Tank of Fear"


            "The Goldfish Bowl of Mild irritation"

            Doesn't have quite the same ring to it...

            Mind you, Goldfish with LEDs on their heads... Hmmm...

          2. Mike Richards Silver badge


            Is a mixture of hydrocarbons obtained by distilling crude oil. It also goes by the names petroleum ether, petroleum spirits or naphtha.

            Benzene may be a minor consituent of benzine, though for all sorts of reasons you'd prefer if it wasn't.

        4. Olafthemighty

          @ Alister

          Nice escape!

        5. ToddRundgren

          There is only one Benzene compound

          You suggest that all molecules which are derived from Benzene, e.g. Phenol, Toluene/Methylbenzene, TCP are carcinogenic, but only Benzene, with no additional molecular sub-group, is carcinogenic as far as I know. It's like saying oygen and water are very similar because they both have oxygen atoms present?

          1. Nigel 11

            Polycyclic Aromatic Hydrocarbons are mostly bad

            True, a benzene ring with a substitution isn't carcinogenic in the same way as benzene. However, most of the polycyclics are evil carcinogens, with the notable exception of Naphthalene (C10H8, two rings), otherwise known as mothballs.

            1. Captain Thyratron

              So don't eat it.

              Does any of this matter, as long as you've burned the stuff and you aren't standing in a sealed garage running the engine for twelve hours (granted, the CO will get you long before trace unburned aromatics or aromatic partial combustion products)? I fail to see the evil, unless somebody is sneaking spoonfuls of polycyclic aromatics into boxes of breakfast cereal.

          2. Chemist

            They all contain

            benzene rings but as you say there's a wealth of variation in their properties and hence carcinogenicity.

    3. Stoneshop Silver badge

      And only in the UK

      In most of continental Europe, diesel is still markedly cheaper, up to 10..15%, than petrol. The price difference is decreasing, though.

      (glass of milk, rather, which is cheaper still per litre. Engines don't run that well on it, unfortunately)

      1. Manas Straw

        And over here in India ...

        The situation is similar to continentatl Europe in that diesel is markedly cheaper than petrol. At one point in the past, diesel was priced at 50% of petrol.

        Milk is cheaper than petrol, but not as much compared to diesel.

      2. hplasm Silver badge


        My point being that Diesel was cheaper than Petrol, and the cost differential made it popular. This woke the sleeping pig (qv chancellor - he who kills the goose that lays the golden eggs) who increased the tax on Diesel to match.

        The increased demand then led to a price rise, making it dearer still than petrol.

        Flames for the rosy glow of a warm trough...

        1. Anonymous Coward
          Anonymous Coward

          Diesel Duty

          Diesel and petrol do indeed attract the same level of Duty. The reason that diesel used to be cheaper than petrol was because the duty was lower than that on petrol. I've been told two reasons for this. The more credible version was that diesel duty was lower than petrol because it was mostly used by the transport industry and therefore the industry got a tax break, as diesel cars became more common the treasury realised that they were losing out on potential revenue and equalized the duty. The less credible reason was that diesel was thought to be less harmful to the environment than petrol and the duty was raised when it was realized that diesel exhaust was every bit as nasty as petrol exhaust.

          I don't buy the latter for the simple reason that the disparity in duty dated to long before governments used green issues to justify fuel duty.

          1. Nigel 11

            Stupid taxation rules

            It's stupid (utterly, completely pig-headedly stupid) to tax a fuel by volume, or to compare distance-per-volume. Diesel is a denser fuel. One liter contains more carbon (hence more CO2 when burned) and more energy (hence better mpg for cars of similar weight and power).

            Fuel should be taxed as energy, so the tax per volume on diesel *should* be considerably higher than on petrol per unit volume. Not equal, definitely not less! This would allow motorists to select the best vehicle for their needs, on a taxation system that doesn't discriminate.

            Diesels have a small thermodynamic efficiency advantage because of the higher compression ratio. This is more significant for big engines (HGVs) than for small ones (cars). Therefore for the best use of our crude oil imports, the majority of cars should use petrol. We can't do all-diesel: an oil refinery creates both petrol and diesel and has limited ability to adjust the proportions.

            BTW I drive a diesel. The distorted tax system made that make sense. In a sane world I'd have chosen petrol (quieter engine, less pollution, with sane tax a lower running cost, after the expensive fully-synth oil and shorter service intervals that a diesel needs is allowed for).

            Also BTW - there's a trade in refined petroleum products across the Atlantic, driven by this same tax anomaly. USA car drivers hate diesels (low winter temperatures may have something to do with it). So we ship surplus petrol to the USA, and they ship their surplus diesel back.

            1. Tom 13

              US diesel use

              is driven mostly because of how long dirty diesel engines have been used in vehicles here. The popular perception is that you get billowing clouds of black smoke whenever a diesel accelerates away from a traffic light. Cold temps do have some affect of course, but the public perception is the larger issue.

              As to the laser ignition system, I think it is intriguing if for no other reason than it should be a part less prone to wearing out. The potential efficiency increases are just the cherry on top.

      3. Michael 28

        Got answer (tax again..vat, specifically)

        Here's my source.

        Similarly in Ireland, businesses are allowed to claim back the 100% of the VAT on diesel but nothing for normal petrol while in Portugal, the amounts are 50% for diesel and 0% for petrol.

        BTW .. Diesels don't need spark plugs... My mum used this once before when she got charged for points and plugs on a service once in Cork many years back . She let the guy go on explaining in a slightly patronising customer service way explaining the bill, and casually dropped that in at the end... She fecking LOVED it.!!!!MWahahahah!

    4. Charles Manning

      For illuminting cockpits

      Many governments are trying to crack down on those green lasers sued to dazzle pilots.

      These spark plug lasers must be pretty intense and will be stocked by every car parts outlet. Won't they make night flying a bit more fun?

  4. Neil Barnes Silver badge

    But do they work underwater?

    Not much point nailing them to a shark's head, else...

  5. LaeMing Silver badge
    Thumb Up

    Very nice work!

    I can think of several other applications for this tech too. Several dozen if I count the non-serious ones :-D

  6. Andrew Ducker


    Sorry to be a killjoy - but how much energy does it take to ignite with a laser (versus the energy for the electrical spark), and how much does the laser mounting cost (sparkplugs being dirt cheap).

    This does sound pretty awesome, but I'd like to know whether it's something that is actually worth doing this year, or whether it's on the distant horizon.

  7. Perpetual Cyclist

    Why is petrol cheaper?

    Petrol and diesel are two different fractions of the same barrel of oil. There is some overlap, and they have different additives. How much you get of each is a matter of the grade of oil, the complexity of the refining process, and the relative market prices. Europe uses more diesel then petrol, the US uses far more petrol. In Western Europe, which costs more at the pump is entirely decided by the tax man. In Turkey petrol is far more expensive.

    Unfortunately, the best oil grades for diesel included Libyan oil. That has caused a massive headache for European refiners, and almost stopped me buying a diesel car. Any technology that improves petrol efficiency is to be welcomed, on energy security as well as environmental grounds. Unfortunately the technology will come too late to prevent the end of the oil age.

    Saudi Arabia promised to make up any shortfall in Libyan oil from their spare capacity. However, far from increasing production by 1.6 million barrels per day, they have cut it, by 0.8 million barrels/day. Because the world is 'oversupplied' with oil. At $124/barrel.

    Production is finally collapsing at Ghawar, the largest oilfield in the world. Saudi Arabia is running short of oil.

    The price of oil will continue to rise until global demand is choked off. In 2008 most of the demand destruction was in the USA. Where will it fall this time?

  8. Zog The Undeniable


    Current multivalve heads already have the spark plug electrodes in a central position (the combustion chamber is very small at the time the spark fires, no not much protrusion is needed). Alfa Romeo have had twin sparks for decades.

    The biggest advantages of lasers here are going to be more accurate timing, although electronic ignition is already way better than points and a distributor, and the lack of the heat sink effect from a big metal spark plug.

    I don't think this is going to boost efficiency very much; in reality, petrol is closing the gap on diesel somewhat with the elimination of the throttle butterfly, improved compression ratios permitted by direct injection (cools the cylinder and reduces the chances of detonation) and a combination of small displacement and turbocharging, as in the latest VW engines. Diesel used to get 40% better mpg then petrol for an equivalent output engine and now it's more like 25%. Actually, when you allow for diesel fuel containing about 10% more energy per litre, the gap is already fairly small - but road fuel is sold in litres, not kilograms, so you get more MJ for your money from a diesel pump.

    1. James Hughes 1

      "...and almost stopped me buying a diesel car."

      What should stop you buying a diesel car is the very high price of replacing the DPF and /or the dual mass flywheel, which are almost guaranteed to need replacing during the lifetime of the car, making it much more expensive to maintain than a petrol equivalent, and costing more to run over the lifetime of the car, taking in to the higher cost of diesel and the better fuel economy.

      1. Anonymous Coward
        Anonymous Coward

        Oh gawd yes...

        The dual mass flywheels are a nightmare! A neighbour of mine is a delivery driver (white van man) and he's had countless flywheels and clutches replaced. It kills the starter motor too.

        When he spoke to Ford they said "It's not designed for start stop journeys"...

        It's a bl**dy van!

        I'll think I'll be sticking with my '96 oil burner for a while, certainly until they get over this idea of dual mass flywheels, or fix it!

        On the diesel upside, the good old fashioned ones like mine last forever. Mine is approaching 200K. Servicing consists of little more than filter and oil changes.

        And I can run it on old chip oil.

        The reliability of diesels started going down hill when they began all this high pressure common rail fuel injection and all that gubbins onto them. Far too much stuff to go wrong.

        As the old adage says, K.I.S.S.

      2. L.B
        Thumb Down

        @James Hughes 1

        Just like to say that: everything you just stated is complete and utter balls.

        Why do you think all London Taxis have been diesel since the day they got rid of the horses, its because its the cheapest way to run any car. Likewise for smaller trucks and vans, with the massive torque making them the only reliable engine for larger vehicles.

        The typical diesel car engine will cost less to maintain and work longer than any petrol engine. This is mostly due to the engines being built stronger to start with and the much lower rev's required to use them putting less strain on components.

        Plus there are no Spark plugs and pesky HT Leads the break down.

        1. Anonymous Coward

          do the maths...

          at the last bean counting session, the total cost of ownership of a diesel car over a petrol car only becomes more cost effective after the car has done over 230,000 miles (for the average family saloon).

          London "black" cabs have diesel engines for two reasons. The car is pretty much "over engineered" so that it will do close to a million miles in its life time. the extra weight of this means the extra torque of a diesel engine will come in handy.

          Back when the black cab was designed, the prices of diesel was so low that it made economic sense to install a diesel power plant in a car that is going to spend 20 out of 24 hours on the road.

          Also, the government encouraged people to buy diesel cars not too many years ago,,, bleating on about the lower cost, more mpg more environmentaly friendly etc... then as soon as the number of diesel cars on the road rose to significant levels, they increased duty !! bastards !!

      3. DRendar


        I have owned several diesels, and various members of my family have owned lots of them for many years and I've never heard of a DPF failure.

        However we all almost exclusively own VAG cars, so I don't know if that makes any difference.

        My current car ('03 Golf PD Tdi) has done nearly 150,000miles and still runs like new - show me a petrol car that can claim the same.

        Servicing Diesels is more expensive - granted, but even if you take into account the rediculous disparity in cost between petrol & diesel at the pump, the vastly higher efficiency still makes them far cheaper to run in the long run (so long as you do enough miles)

        1. 42

          Ok then

          My Ford AU Falcon has over 250,000 miles and still goes well. It runs on petrol, but mostly on LPG.

          Servicing is very cheap. A diesel would be more expensive to run. And it actually accelerates quickly, unlike disels.

          You can keep em!

    2. Stoneshop Silver badge

      (versus the energy for the electrical spark)

      First read that as "electrical shark"

    3. Funkster

      Centre 2D != centre 3D

      Although the plug is on the central axis of the cylinder in a 4-valve engine, it is at the very boundary of the fuel/air charge. This means the flame front can only propagate out in a hemisphere. If you can get the ignition point into the very centre of the charge (or better yet, two points within the charge with good spacing) then you get a bigger flame front and get a quicker overall controlled burn with less chance of detonation.

      This really will make quite a big difference especially on DI engines using stratified charge - enough to compete with diseasel even on a volume-of-fuel-per-mile basis. Add the much nicer exhaust emissions of delicious petrol into the equation and this is a winner!

      Wonder if I can retrofit this to a morris minor...

      1. John Angelico

        Wonder if I can retrofit this to a morris minor...

        ...only if you recognise the intellectual property rights of the late Lord Nuffield.

        You could try retro-fitting it to a mini-cooper S - straight after you take the brain surgery correspondence exam :-)

      2. John 62

        Re: Centre 2D != centre 3D -- or 4D :)

        When the spark is required, the piston is nearest the head of the cylinder, so the volume of the area to be ignited is small. Hence the 3D centre of the volume at that point can be reached by the spark plug. However, taking time as the 4th dimension, as the piston goes down, the flame front will have further to go on the piston side than the head side. I'm not sure how a laser would improve that.

        On the other hand, although spark plugs are quite light, here's hoping solid state lasers can be lighter and more easily controlled.

      3. Guy Smillie


        Upvote from me just for introducing me to a useful new word.

        Skull 'cause it sounds dangerous.

        1. Allan George Dyer Silver badge

          prior art

          Thomas the Tank Engine books.

    4. Stoneshop Silver badge

      Few engines have single-valve heads

      Anyway, I've read of ignitions that use a single-electrode spark plug with a matching protrusion on the piston dome, effectively putting the spark "inside" the fuel-air mixture instead of having it partly shielded by the ground electrode. There are also the triple- and quad-electrode plugs with the ground electrodes sideways respective to the central electrode, and surface-spark plugs, which attempt to achieve the same.

  9. fridaynightsmoke

    It makes me wonder about the reliability;

    not only of the lasers themselves (although I imagine that they could quite easily be made very reliable, at a price) but of the optical conditions between laser and combustion point.

    The inside of a combustion chamber isn't known for being optically pristine, and I can imagine that other engine problems (bad fuel? blown head gasket?) requiring a full set of new lasers for ££££ instead of a set of new plugs for £.

    1. There's a bee in my bot net

      I was wondering the same thing myself...

      Perhaps if the fuel/air mixture is really lean it will burn clean enough not to deposit by products on the laser aperture. The other possibility is using a YAG laser means that the point of ignition is a point in space away from the exit window (YAG are groovy in that they allow you to focus a large percentage of their energy on a small point at a given distance) meaning that deposits won't affect the laser output too much, in the same way that (some) CD laser(s) can read data through a moderate amount of crud as the focal point is beyond the crud. Or maybe they will be fitted with little wipers to clean the windows :-)

      1. lasersage


        can't most/all lasers be focused in this way? not sure why you think it makes YAGs so groovy.

        As for the deposits that was my first thought, although what appears opaque to you and I may well be relatively transparent to the infra red the YAG is likely to be putting out

        1. There's a bee in my bot net

          Focused pulse laser...

          Granted most/all lasers can be focused with optics, but AFAIR there is a way to mechanically focus YAG lasers without optics. I wish I could remember how it works but it was 20 years or so ago...

      2. Anonymous Coward
        Anonymous Coward

        @There's a bee in my bot net

        I believe that the lean mixture will be required for the lasers to remain clean. The leaner you get an engine to burn, the less "crud" you get build up in the engine. The more air you have in there the more oxygen you have to react with the elements that would become "crud".

        Crud = C (carbon, black solid)

        Crud+air = CO2 (carbon dioxide, Oooh, a gas... Pump it out the back!)

        Yes, I know, there are loads more elements in the fuel, but most will become gaseous at those temperatures when oxidised, although it might be a good idea to avoid allowing silicon to get in the fuel...

    2. TeeCee Gold badge

      Re: reliability.

      There are many transparent materials around that would laugh at the conditions in a combustion chamber. Deposit on the lens could be an issue I'll grant, but removing 'em at the annual service and cleaning the optical bit (a quick zap in the ultrasonic bath should do the job) wouldn't be too onerous a task.

      I suspect that they'll turn out to be rather more reliable than direct fuel injectors as there are no moving parts and the delicate bits will be insulated from the nasty stuff by a solid lens.

    3. Paul Crawford Silver badge

      Reliability and NOx products

      My concerns are the issue of reliability given the generally dirty-ish inside of a combustion chamber where one might expect a fair proportion of the energy is lost in the window's surface after some time.

      Of course, then the cost of the laser assembly.

      And the opportunity for idiots to play with them outside of the engine.

      Finally, I thought one problem with leaner burning engines was high NOx products? Can anyone knowledgeable comment on that aspect?


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