• Oct 15th 2010 at 7:57AM
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Engine downsizing is considered an effective method to reduce emissions and improve fuel efficiency. The basic concept is simple: replace a larger engine with something that displaces less and, typically, packs a turbocharger to make up for any lost power. One impediment to engine downsizing is low-speed preignition (LSPI). Preignition occurs when the combustion chambers ignites prior to the spark event. This causes advanced combustion timing which can lead to heavy engine knock and catastrophic engine damage. By using cooled exhaust gas recirculation and advanced ignition systems, Southwest Research Institute (SWRI) has demonstrated that LSPI can be suppressed in downsized, turbo'd engines. That's not all, though: SWRI hopes to focus on fuels and lubricants to quell LSPI entirely.

SWRI will launch a consortium – the Preignition Prevention Program – focused on eliminating LSPI through advancements in fuels and lubricants. Joining the consortium comes at a cost, but it's open to a wide range of companies including, original equipment manufacturers ($225,000), engine component suppliers ($175,000) and those in the fuel and lubricants industries ($225,000). The consortium's initial meeting is scheduled for January 2011 and any patents developed throughout the course of the program will be accessible to all consortium members. Hit the jump for more on LSPI and its effect on engine downsizing.

[Source: Southwest Research Institute]


SwRI to launch Preignition Prevention Program (P3) Consortium

San Antonio - Oct. 6, 2010 - Southwest Research Institute (SwRI) will launch a new consortium focusing on fuels and lubricants to discover ways to suppress low-speed preignition (LSPI), a condition that causes heavy engine knock and can seriously damage engine parts or cause complete engine failure.

"The P3 Consortium will help us gain an understanding of fundamental issues of low-speed preignition. We are going to investigate interactions of fuels and lubricants to understand what role physical and chemical properties play in low-speed preignition," said Chris Chadwell, senior research engineer in the Advanced Combustion and Emissions Section in SwRI's Engine, Emissions and Vehicle Research Division. The consortium will develop control solutions and guidelines to prevent or reduce incidences of LSPI.

In LSPI, the fuel in the combustion chamber is ignited before the spark event, causing significantly advanced combustion phasing. Low-speed preignition events are random, infrequent occurrences that happen at low speed and high torque. Under these conditions, a preignition event leads to very heavy knock, which can cause catastrophic damage in only a few engine cycles. The consortium will study the interaction of fuels and lubricants and how they interact and contribute to LSPI.

"When you ignite the fuel too early, you have very high knock. These early ignition occurrences are very infrequent and random but can be quite destructive. The current solutions to get around the problem are very costly," Chadwell said. The consortium will look at the root causes and work to develop new lubricants and lubricant testing methods. The presence of low-speed preignition is considered a major impediment to automobile manufacturers' efforts to aggressively downsize engines to reduce carbon dioxide emissions.

As an independent R&D laboratory, SwRI has extensive experience in managing consortia. The HEDGE-II consortium is developing high efficiency spark ignition engine technologies, and the Clean Diesel V consortium, now in its 19th consecutive year of research, is developing efficiency and emissions solutions for future diesel engines.

Cost to join the P3 Consortium is $225,000 for original equipment manufacturers and those in the fuels and lubricants industry. For engine component suppliers the fee is $175,000.

An advantage of consortium membership is that the impact of the yearly contribution is multiplied by the number of participants, providing substantially more research than would be possible through funding from a single member. Additionally, consortium members will have the right to access any patents that are produced from the consortium's work.

The initial meeting for the Preignition Prevention Program Consortium is scheduled for January 2011.

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    • 1 Second Ago
      • 4 Years Ago
      What's their target and aren't they solving a solved problem?

      There are plenty of small ICE's in production, both in petrol and diesel versions. So what exactly do they mean as a "downsized" engine and why would anyone use anything smaller than 1.0l Diesel?
        • 4 Years Ago
        Hi nbs,
        Fiat at any rate seem to disagree, as they are producing in in a 900 cc size and specifically note it's suitability for use in a hybrid.
        • 4 Years Ago
        The Fiat multiair Twin Turbo gets excellent performance and economy from only 900cc:

        Downsizing and increased performance has nowhere near reached it' limits next.
        The multiair engine is particularly interesting as it's compact size makes it a great choice for hybrids:
        'With respect to a four-cylinder of equal performance and medium displacement, the new engine is significantly shorter (-23%) and lighter (-10%), opening the way to interesting further developments, such as natural gas fuel feed or hybrid technology combinations.

        In particular, a natural gas version of the Twin-Air will be available soon providing a further CO2 emission reduction; this is possible by adopting a pair of special injectors in addition to the gasoline injectors on the intake manifold rails. Fiat also notes that because of its small size, the Twin-Air is well suited to be applied in a hybrid system.'

        I'd much sooner use this as an RE than a Wankel engine.
        • 4 Years Ago
        Sorry, I meant 1.2l Diesel (like one from VW) or 1.0l petrol (Toyota).
        • 4 Years Ago
        That 900cc is a fine engine. As for a hybrid, it might be a good choice, although I'd prefer something much simpler, perhaps less powerful but slower turning and more efficient.

        I just don't think they can downsize that engine, the recent trend was to rather increase the displacement (due to increase in vehicle mass and performance expectations). 10 years ago they were still using 700cc engines.

        They will probably squeeze more power out of this engine but that alone may not be enough to keep up with growing requirements. And many of these optimizations are useless or even harmful for RE engines - they simply have a different set of requirements.
        • 4 Years Ago
        Small engine with a turbo isn't well suited to be use as a range extender. What matters in a RE is 1) size, 2) peak fuel efficiency, 3) noise, vibration etc. And, as gorr pointed out, there is a whole load of characteristics that are irrelevant in this scenario. We are probably better off using a simple and efficient ICE, without turbo and high RPM's that fits in and is quiet enough. That's not equivalent to one having lowest possible displacement, especially that power is not really a critical factor (if it's larger than needed the ICE will simply work shorter).

        OTOH, good thing about standard small engines with turbochargers is that they have better fuel efficiency at low loads and are still capable of delivering sufficient power when needed. That's a very different use case from a RE engine. Here the minimum displacement is limited by the required peak power, effectiveness of turbocharging and maximum RPM's. I don't think it makes sense to go below 1l unless we put such an engine in a very lightweight (by today's standards) car. Otherwise the engine would have to continuously work above its peak efficiency load.
      • 4 Years Ago
      Instead of making the engine more complex, just change to a fuel that naturally suppresses low-speed preignition due to it's high octane properties: E85.

      • 4 Years Ago
      "Low-speed preignition ... happen at low speed and high torque."
      This should happen only on a manual transmission in situation where you should have shifted to a lower gear.
      Any Automatic transmission (including Prius-like CVT etc.) will automatically gear down and increase rpm when hight torque is needed.
      Get rid of manual transmission -> problem solved.
      And yes, I know that manuals used to be more efficient than autos, but the difference is decreasing.
      • 4 Years Ago
      With their MultiAir / TwinAir system that operates according the "Ingoing Air Control", Fiat / Schaeffler-INA seem to be ahead the rest auto-makers.

      Yet the "Ingoing Air Control" is the wrong way.

      At http://www.pattakon.com/pattakonHydro.htm the correct control (the “Outgoing Air Control") is presented.

      And speaking for "aggressive engine downsizing", take also a look at the PatOP engine at http://www.pattakon.com/pattakonPatOP.htm .

      Manousos Pattakos
      • 4 Years Ago
      This doesn't sound like it's aimed at the large auto companies we know. They already seem to have a big leg up on preventing these problems.

      GM is running 11.4:1 compression ratios on regular gas, and I'm sure other large companies are going even higher, so I don't think they're being held back too badly at the moment.
        • 4 Years Ago
        11:1+ on pump gas is pretty normal for a direct injection motor.

        Yeah, i don't get how this is aimed at normal autos. I wonder how aggressive we're talking in terms of downsizing. I think you can only go so far because when a tiny engine is out of it's boost range, it will strain to move a large car from a stop...
      • 4 Years Ago
      We need a whole new type of internal combustion engines:

      Cam *driven* (rather than crankshaft driven)
      low loss valvetrains, like rotary or electric valves
      rotary combustion design (rather than reciprocating)
      heat recovery for a new type of hybrid


      Sincerely, neil
        • 4 Years Ago
        "+ Use the Atkinson valve timing, like the Prius does, which has a lot of overlap of the exhaust valve with the beginning of the intake downstroke (I think?) so that there is built in exhaust gas recirculation (aka EGR). This also effectively doubles the efficiency."

        Actually, an Atkinson cycle has overlap between the intake stroke and compression stroke. Effectively, it creates a longer power stroke than intake stroke- which also eliminates predetonation by not creating heat in the cylinder from compression. By comparison an EGR valve effectively cuts the amount of oxygen in the air to reduce pre-ignition. Because it is more thermally efficient, more of the energy is converted into motion and Atkinson cycle does not create enough exhaust pressure to power a turbocharger very well.

        A further advancement of the Atkinson cycle is the Miller cycle that has even more overlap, but compresses against a supercharger (where the compressed gasses have already cooled). This allows for forced induction engines that have 13:1 (or more) compression ratios and no predetonation problems on regular gas. If combined with a clutched supercharger, variable valve timing, direct injection etc., it has a superior power output to an Otto cycle of the same size and superior thermal efficiency to an Atkinson cycle.

        • 4 Years Ago
        Right, I'm with you on that! But, we need to greatly improve ICE's, as well.

        Sincerely, Neil
        • 4 Years Ago
        What are other ideas to improve ICE's?
        Throw all the crap out and replace with an e-motor.
        • 4 Years Ago
        This is a continuation/generalization/more organized version of my earlier blog post:


        There are a lot of improvements possible for internal combustion engines (aka ICE's). It helps to list the areas that are causing losses, to start:

        -- The geometry of the physical layout of the piston, connecting rod and the crankshaft is less than ideal. The connecting rod needs to be ~60 degrees past top dead center to get the best leverage on the crankpin; but the pressure from the fuel ignition occurs much earlier than this; when the connecting rod is essentially trying to bend the crankshaft sideways. The motion of the piston is necessarily sinusoidal.

        - The power stroke is only 25% of the full cycle, and there is a lot of mass that has to be accelerated, stopped and accelerated again.

        - The valvetrain has to physically resist being moved, and it has to work against the air flows.

        - The piston tends to scrape the sides of the cylinder, because it would "rather" twist that stay straight. The rings must exert friction on the cylinder.

        - The oil must be pumped through little tiny passageways.

        - Electricity must be generated.

        - An ICE is a self-powered air pump, in essence. Air flow and the pressures generated, and the cyclical nature of them cause resonances, and backpressures, and the gasses become spring-like.

        - Small volumes, like the space above the top ring and the top edge of the piston, trap unburned fuel because the flame cannot reach it.

        - Everything flexes and springs -- the crankshaft and the camshaft flex torsionally and longitudinally, the piston vibrates and distorts, as do the cylinders. Valves bounce and stretch and distort into potato chip shapes.

        The list goes on... The net result is a typical internal combustion engine that uses ~20% of the energy in the fuel for output motion at best, and requires a transmission to keep the torque of the engine relatively close to the speed of the vehicle.

        So, knowing all this, how can we make incremental or wholesale improvements?

        + Offsetting the crankshaft center away from the power downstroke gives the connecting rod some better mechanical leverage -- but is the compression stroke adversely affected?

        + Variable valve timing allows the torque to be available over a broader range of RPM's.

        + Valves can be electrically/hydraulically moved in both directions (opened and closed) to avoid fighting the springs. This also makes it easier to use subtle or more abrupt adjustments to the valve timing.

        + Use cams rather than the crankshaft, to gain a lot more mechanical leverage, and to allow the piston motion to be controlled by the designer; like the Revetec:


        This particular design also reduces piston scrape (but it introduces some tendency to spin the piston within the cylinder). It also avoid big changes in crankcase pressures (in configurations with even numbers of pistons). This design effectively doubles the efficiency.

        + Use the Atkinson valve timing, like the Prius does, which has a lot of overlap of the exhaust valve with the beginning of the intake downstroke (I think?) so that there is built in exhaust gas recirculation (aka EGR). This also effectively doubles the efficiency.
        Hmmm, how well would a 2-cylinder Revetec with Atkinson cycle and electrically activated valves work?

        + Use a rotary design that reduces the reciprocal motion.

        + Use a 2-stroke design to cut the parasitic losses in half.

        ++ Use a continuous burn design to further reduce the cyclical nature of the engine; or at least reduce the time between power cycles.

        + Figure out how to reduce waste heat from being produced, and then try to use the remaining excess heat to produce output.

        What are other ideas to improve ICE's?

        Sincerely, Neil
        • 4 Years Ago
        Thanks for the clarification! My parenthetic comment (I think) meant that I was not sure of the details. So, again, thanks for the correction.

        Sincerely, Neil
      • 4 Years Ago
      BMW has just in time fuel delivery, and so do Mercedes, Jaguar.
      Hyundai & GM have split stroke direct fuel injection, the really lean initial fuel:air mixture more/less can not pre-ignite.

      Without direct injection, BMW's Valvetronic, Nissan's VVEL, Toyota's Valvematic intake valve lift systems markedly reduce droplet size.
      • 4 Years Ago
      It's more easy tp downsize an engine if it's for connecting it as an electrical generator instead of pusching the entire car via a conventionnal transmission. No need to have lot of torque at slow rpm, so half the cost for manufacturing and better longivity, less stress on the parts like crankshaft, connecting rods, pistons, piston pins, lubrication, cooling, transmission, programmation, etc. A small one cylinder gasoline engine/generator of 200cc can power a small car the size of a ford focus or civic or corrolla or mazda 3 or cavalier or dodge neon or tesla, imiev. ithink, go kart, fit, yaris, fiesta, big rollerblades kit, 10 speeds bycicles, scooter, small motorcycle, home emergency electricity.
        • 4 Years Ago
        Don't worry it will come out. Manufacturers are still working for big oil to show that's it's impossible to go higher then 100 mpg with normal usable power. there even no hydraulic drive cars that should be better then electric. Nobody have made a small gasoline electric generator with heat recovery to power a second water-steam electric generator for 60% overall efficiency instead of the max efficiency of 23% for ice that do not have heat recovery. Heat recovery is just a basic technology, it's a shame that nobody have made a working prototype. The way that almost every car of today are just using minute power from their ice engine is very old outdated faschion, it even consume gasoline at idle and when compressing and breaking, LOL. But secret swiss bank accounts for ten of tousands folks in petrol/car manufacturers/governemental/
        journalists are impeding the way to a normal car mechanisms.
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