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Ricardo’s “deep” Miller cycle concept: Magma

In its new report on downsized and boosted gasoline engine technologies (earlier post) the ICCT highlighted Ricardo’s work on an “extreme” Miller cycle concept with high (13:1) compression ratio (CR) and central direct injection in a downsized boosted engine.

The basic architecture of “Magma” concept is a boosted four-stroke gasoline engine with four valves per cylinder. The Magma concept architecture closes the inlet valve early to reduce pumping losses. A mechanical supercharger and fixed-geometry turbocharger fill cylinders effectively. A long exhaust stroke then extracts maximum efficiency.

Magma boost system layout. The mechanical supercharger is in the low-pressure position and the fixed-geometry turbocharger is in the high-pressure position. The system provides the required boost pressures across the engine speed range. Source: Lewin (2016). Click to enlarge.

There is no component in the engine which isn’t proven in production already, said Trevor Downes, chief engineer, engines, at Ricardo Innovations.

Under most conditions, Magma closes the intake valve at least 30 degrees before bottom dead center (BDC). The in-cylinder gases are thus expanded and cooled as the piston descends, before being re-compressed as the piston rises again. The compressed gases in Magma are lower in temperature than in a conventional engine as the spark plug fires, thereby helping reduce knocking and potentially allowing more advanced ignition timing for better efficiency.

In the ICCT report, the authors (including David Boggs from Ricardo), noted that in Pendlebury et al. (2016), the Ricardo team showed that increasing the CR from 10.2:1 in the baseline engine to 13.0:1 without any change to intake valve cam (IVC) timing resulted in a significant increase in knock amplitude, even with very retarded combustion phasing. Electronically controlled IVC reduced knock back to the baseline level. This supports the hypothesis that the unburned gas temperatures are lower in the Magma case than the baseline engine, compensating for the higher cylinder pressures. Source: ICCT, Pendlebury et al. (2016) Click to enlarge.

The expansion ratio on the exhaust stroke is much higher than the effective compression ratio; the longer expansion provides extra power to the crankshaft and extracts more energy from the combusted fuel. There is also less work expended during the pre-combustion compression stroke.

Magma’s valve timing enables the geometric compression ratio to be pushed up to 13:1 but keeps the effective compression ratio to around 9.5:1. All this benefits thermodynamic efficiency.

The concept places particular demands on the boosting system. Early closure of the inlet valves leaves a smaller window for the charge fill the cylinder. Magma, which uses a mechanical supercharger and a turbocharger as well as two stages of intercooling to ensure the charge air is as cold and dense as possible as it enters the cylinder, runs on higher boost pressures than have been the norm.

In an article in Ricardo Quarterly Review, Trevor Downes explained that Magma compounds the pressure ratios across both boosting devices all the way across the full-load speed range and in the steady state, allowing for effective interstage cooling.

The ICCT report stated that the Magma engine shows a full-load ISFC benefit of nearly 8% compared with the baseline. Testing also found an 18% reduction in fuel consumption at the low speed light load condition of 2000 rpm/2 bar BMEP and an 8% reduction at a moderate load of 8 bar, over the baseline engine.

Ricardo continues to develop the concept.


  • C Rouaud, R Osborne, K Pendlebury, J Stokes, J Dalby (2015) “The Magma Engine concept - A downsized turbocharged gasoline engine with high compression ratio” 2015 JSAE Annual Congress (Spring)

  • Ken Pendlebury, Richard Osborne, Trevor Downes, Simon O’Brien (2016) “Development of the Magma Combustion System” 2016 JSAE Annual Congress (Spring)

  • Tony Lewin “Transformative Technology”, Ricardo Quarterly Review Q3 2016


Account Deleted

Another shameful planet destroyer tech. We do not need it. It will destroy life on our planet. We need zero pollution tech from now on.

Thomas Pedersen


It's pretty clear by now that you would like everybody to drive BEV within the next month or so. Sadly, this is not possible.

Even with aggressive growth of manufacturing capability for all BEV components, it will take quite a while before enough BEVs can even be made to saturate the demand for new cars.

In fact, most technology changes take 30 years, give or take as a function of replacement of equipment, engineers, technology acceptance, etc. 'Gearbox-oil-film-velocity-gradient-specialist' do not just become experts in vehicle electronics overnight.

Therefore, it is quite warranted to improve on the technology that will still be relevant for at least one product generation.

However, I predict that ICEs will get more simple with BSG/ISG e-motors will pick up the slack from gasoline engines and allow more and more electrification. The latest swath of 48V-related news seem to suggest this technology is picking up momentum.

Trevor Carlson

Cool down there Henrik. Every step forward gets us closer to the end goal which is 100% sustainability.

On the other hand you need to also consider that "Zero pollution" solutions that are economically competitive now may actually be a step backwards in regards to sustainability and product lifetime pollution impacts on average. Locally there are places that minimize the worst of those impacts but we must consider global populations and their access to economically competitive sustainable energy.


@ Thomas

One could make that argument about this technology as well.

Ricardo continues to develop the concept.

While the internal combustion engine is old tech that may take 30 years to replace this concept is such a radical change to the old tech it may take years to get it off the lab bench and decades for it to replace the older tech in any meaningful numbers. Meanwhile, BEVs are already in the showrooms and on the streets.


I agree with ai_vin and Henrik. The world should aim for a much faster switch to electrified vehicles (BEVs/FCEVs).

Since the majority (54+% in EU and up to 70+% in some countries) wants affordable electrified vehicles, the proper incentives should be put in place today and let the fossil, bio fuel and ICEV lovers/producers scream.

Subsidies should cover most of the initial cost of batteries and/or FCs. Sales and road taxes and parking fees should be temporarily removed on all electrified vehicles.

Subsidies could be revenue neutral with much higher progressive pollution taxes on fossil/bio fuels.

Account Deleted

Thomas I have no illusions we will all drive BEVs within the next month. However, a zero emission mandate could do it by 2030 for sure. It could start with 5% of all vehicles sold by each automaker to be zero emission by 2017. For each year the percentage will be regulated up until in 2030 where the zero emission mandate is 100% of all vehicles sold must be zero emission. Non-compliance with the zero emission mandates should be punished with fines equal to the average selling price of the vehicles that are in non-compliance times the number of non-compliance vehicles sold. Automakers that are in over compliance like Tesla that already is a 100% zero emission automaker can sell of credits for each vehicle they are in over compliance for 15.000 USD per vehicle.

We only need to build about 100 of those giga factories that Tesla is making to make enough batteries to produce all the worlds’ cars as as BEVs well as all the battery backup needed for renewable energy. See

We can do that by 2030. With driverless BEVs we actually only need 20 million BEVs per year to replace a production of 140 million non-driverless cars per year. So 2030 is very realistic for all new vehicles made to be zero emission.


Some people have very rosy visions of how fast we can scale up production of things like lithium.

Even the objections miss the point.  The real threat is Jevons' paradox:  the more efficient the consumption machinery, the more you can afford to pay for fuel and the more gets extracted and burned.  This calls for a carbon tax to offset it.  An 18% improvement is a great thing when most of the fuel is e.g. derived from waste.

The Lurking Jerk

Even Engineer-Poet, who has posted a very insightful comment, misses the point. The more humanity learns to use fuel efficiently (and grow food, and desalinate water, etc.) the more crowded the planet will become- and most of that planet will likely be unregulated. No one in any poor place cares about zero-emission vehicles. By far the easiest end-run around pollution of all kinds is to gradually lower the earth's population. Perhaps allowing one birth per urban mother and three births per rural would do it gently.
In the meantime, remember that govt will mismanage battery recycling, battery manufacture and regulation, and these batteries will be recharged by coal, gas, oil and nuclear plants. Migrating to renewable electricity production would be an astronomical expense which definitely can't be paid for by 2030, and don't forget the electrical distribution infrastructure would have to be totally rebuilt. Places like California will fight every single change that this all would entail- they already have opposed every significant solar farm, desalination plant, power transmission line, and wind farm. Next, modern government is completely saddled with debt because of social spending. There is nothing left to spend.


"will take quite a while before enough BEVs can even be made"
It is not supply, it is demand. They could make twice as many but they would sit on the lots, there is no waiting list.


World [dominated by US] government and non government military spending is intimately related to propping up the fossil fuel economy and the self perpetuating military industrial complex, in turn leading to more political instability, wear and poverty. This gigantic wasteful crisis could be contained by a rapid change to a renewable energy economy. This could starve the military industry in a virtuous cycle and save the planet's population by stopping global warming. The economic benefits to the developing world would likely curtail population growth as it tends to do in developed nations. Small distributed renewable energy systems may take political control away from the greedy megalomaniacs now dominating the world. The sooner the better.


In addition to bryoz's comment about economic benefits curtailing population growth I would like to point out education does the same. Better educated people make smarter decisions about the resources they have available to them. Energy supply and use is obvious to this forum, a less obvious resource is manpower, or as they say in third world countries - 'family size.' [This is especially true when those being educated are girls.]

Never shortchange education.

Account Deleted

@SJC you are right about old-automakers being demand constrained with regard to their plug-in offerings. Fx the Leaf only sells 50k units per year and they planned to make 250k units per year.

However, Tesla is the exception. They are supply constrained and they are selling every vehicle they can make. They have a half year wait list for the Model X and more than one year wait list for the Model 3 measured from the day production of that car starts.

IMO the difference between Tesla and the old automakers is that Tesla is all in on BEVs and can focus to make cars that people and companies want. The old automakers do BEVs as a side business they do it halfhearted. So their BEVs suck. They should do it wholeheartedly diverting all R&D resources to the development and production of BEVs and just let their old combustion business use existing factories and already developed tech. No need to invest more in a tech that is doomed anyway.

@L Jerk I did not say all fossil fuel burning with end by 2030. There will still be lots of old power plants and gassers out there. However, no >new< fossil or biomass burning cars or power plants should be allowed to be made after 2030 and that is clearly realistic. Give it 20 more years and in 2050 we can ban all cars and power plants that operate on bio-fuels or fossils apart from some cars that for historical and cultural reasons should be preserved to educate about how it was in the old days.


It will be a very long time before the grid is powered up with efficient non polluting generators. It may not happen at all, given the enormous investment required. So, for now that thinking is pie in the sky dreamer status.

What Chevy did with the volt and the Japanese e-energy system is a good compromise, but costly for the benefit.

First ethanol fuel can do more now and in the future upon GW concerns. Better to utilize solar and wind to green up ethanol and farm operations. Same benefit just cheaper and more convenient transportation.

Ethanol is also a superior fuel for emissions and power generation. Compression ratio's need not be limited to fuel character. They have run the fuel 30:1 ratio with no problem. Consider an optimum ethanol engine. First, because the technology is achieving higher efficiency via high boost pressure, the two cycle engine may be the engine of choice, given the dramatic loss of friction per power stroke. Consider the opposed piston engine that can maximize compression with low crank angle. The engine doubles the compression ratio with half the stroke. This minimizes the biggest problem of high compression engines, the high sidewall scuffing of pistons per high crank angle. Consider that ethanol has a much higher cooling effect to improve DI efficiency. Double that benefit with hydrous ethanol. Note that the two cycle would have port system of valving, but intake can be timed per circular slide valve, probably powered by continuous revolution. These valves have proven themselves to be very reliable. Not restricted to ethanol engine, but, should engineers be utilizing waste heat exhaust to absorption chill intake air. A liquid to air plate chiller would remove a lot of intake air heat.


Many configurations can be used as a range extender.

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