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Results Of MUSIC Engine In-Vehicle Demonstration To Be Presented 17 December

MUSIC system schematic. Click to enlarge.

A one-day seminar, hosted by Coventry University (UK) on 17 December 2007, will present the results of an experimental project to develop the MUSIC (Merritt Unthrottled Spark Ignition Combustion) gasoline engine to an in-vehicle demonstration stage.

The MUSIC gasoline engine promises to match or to improve on the fuel efficiency of the diesel engine at part load, providing an approximate 20% increase in fuel economy over conventional gasoline engines. MUSIC is an un-throttled, high thermal efficiency, lean-burn, spark ignition system that uses an indirect combustion chamber to produce charge stratification by means of controlled air management.

The MUSIC project has been part funded since 2006 by the UK Department of Transport under the Low Carbon Research and Development Programme, which is managed by the Energy Saving Trust. UK firm Powertrain Technologies Ltd. (PTech) is undertaking the development work, with support from Ford, BP Castrol and Coventry University. Knibb, Gormezano & Partners (KGP) is responsible for managing commercialisation of the technology.

The recently patented MUSIC engine was invented and developed by Dr. Dan Merritt while working at Coventry University.

Until now Diesel engines have given far superior fuel efficiency at part load when compared with gasoline engines but gasoline engines delivered more power for a given size. The MUSIC gasoline engine has now demonstrated part load efficiencies as good as the diesel engine but at a lower cost. For most vehicles, the greater part of operating life is spent at part load and idling.

The MUSIC technology affects only the layout of the combustion chamber in the cylinder head and does not impact the bottom end of the engine.

—Dan Merritt
Stratification by helical swirl. Red indicates stoichiometric air:fuel mixture, green indicates air only. Click to enlarge.

Implementing MUSIC requires a modified cylinder head and a direct injection fuel system. The indirect combustion chamber features an inbuilt helical swirl that can not only run successfully at air/fuel ratios of more than 100:1 but also reduces HC and NOx emissions significantly. The developers earlier estimated that up to 80% reduction in NOx and HC is possible. Load and speed control is achieved by the precise control of injection timing and duration.

At the Stuttgart Engine Expo 2007 earlier this year, the team presented results of their work on a single-cylinder test engine, which included:

  • Effective ignition at air/fuel ratios of 140:1

  • Self sustained running at AFRs out to 105:1. (The probable limit of AFR at which useful work is done is around 85:1)

  • Apparent freedom from detonation (no hot spots exposed to air/fuel mixture)

  • Smooth idling at 700 rpm

  • Unthrottled start up

  • Very low to almost zero NOx under lean burn at AFR’s beyond 35:1

MUSIC Single Cylinder Part Load Thermal Efficiency
rpm 1000 2000 2000 3000 3000
IMEP (bar) 1.4 2.9 3.2 3.1 3.6
Indicated Thermal Eff (%) 38.2 36.4 43.2 46.9 41.6
AFR 135.0 36.4 43.2 46.9 41.6
Volumetric Eff (%) 92.5 98.1 97.0 76.0 80.0
Pmax (bar) 24.7 34.9 32.6 24.5 35.6
BMEP (bar) 0.3 1.7 2.0 1.6 2.1
Brake Thermal Eff (%) 7.9 21.2 26.8 23.7 23.9

The 4-cylinder prototype built for the in-vehicle demonstration is based on a Ford 2.0-liter engine.



Rafael Seidl

This isn't a wholly new concept, indirect combustion was standard on diesels in the 1980s. The difference here is that you use a lower compression ratio and a spark plug.

As with any lean burn concept, the real issue is emissions. If you lean down by using more fresh air, you have surplus oxygen in the exhaust gas so you have to use an expensive NOx aftertreatment system. If you lean down using EGR, you need to cool it down externally to avoid engine knock.

Ricardo combines turbocharging with low-pressure cooled EGR in an SI engine concept they call Lean Boost Direct Injection (LBDI). Engine-out temps are low enough to support a regular VGT turbo, which substantially reduces turbo lag. More here (for-fee technical paper):;do=show/site=a4e/lng=en/alloc=3/id=6744


I'm curious as to why we haven't seen more EGR cooling since it seems to be relatively mature based on use in diesel engines and naively, I don't think it would be as expensive or complex as the different systems designed to deal w/ higher engine out NOx in lean burn engines.


Huh, Rafal Diesel. Last name begins with an S?

gary davies

Rafael, you said:

"As with any lean burn concept, the real issue is emissions. If you lean down by using more fresh air, you have surplus oxygen in the exhaust gas so you have to use an expensive NOx aftertreatment system."

the article states:

"Very low to almost zero NOx under lean burn at AFR’s beyond 35:1"

so doesn't that imply they have addressed this problem?


It is true that NOX is the main problem with lean burn due to the fact that the excess heat can easily burn the nitrogen in the air.

One solution is to limit the Oxygen by mixing with exhaust gas (EGR), thus excess O2 means no reaction of N2 to O2. This also decreases the max combustion temp.

The MUSIC approach is similar to a prechamber of a diesel engine in which the chamber's temp can easily be controlled by the engine's cooling system, thus avoiding unwanted NOX. The spiral architecture actually provides maximum surface area for a much better cooling capacity of the combustion chamber resulting to low NOX emission.

I think this is a real promise that can be applied RIGHT NOW.

Roger Pham

"I'm curious as to why we haven't seen more EGR cooling since it seems to be relatively mature based on use in diesel engines and naively, I don't think it would be as expensive or complex as the different systems designed to deal w/ higher engine out NOx in lean burn engines."


Cooled EGR cannot be used in stoichiometric combustion at below certain charge density (load level) because it will inhibit flame propagation leading to roughness and engine flameout. Ergo, we see cooled EGR mostly on diesel engine at above certain load level. At low load, there is no need for EGR in diesel, as the combustion temp is already way cool.

Ah ha, what if in a gasoline SI engine, you this MUSIC scheme for part-load low enough to keep peak combustion temp cool enough to prevent any significant NOx formation above regulated limit, and bypass the 3-way catalytic converter altogether.
AND at higher load, run the engine at stoichiometric with a maximum amount of cooled EGR that would still support smooth running, while route the exhaust thru the conventional 3-way cat to avoid expensive NOx post combustion treatment?

A little bit more plumbing, but can save a lot of expenses on post combustion NOx treatment, and gasoline engine is still cheaper than diesel, even with DI.


Not quite to this topic but not so far off. About three months ago there was an article about Ford funding development of H2 injection in quite small amounts to improve gasoline ICE burn. Some guys PHD work in Australia led to it.

His thesis looked very promising (don't they all?) One advantage was that if the H2 ran out the engine just ran with less power.

My thought at the time was maybe CNG could be injected instead of H2 and produce similar results. CNG being readily available and much simpler to handle.


It appears this technology would have the same trade-offs as gasoline HCCI. Certainly, the higher efficiency is welcome, but it still uses a very volatile fuel - gasoline.

In my opinion (I've worked in the air quality field for nearly 25 years, mostly as an air pollution meteorologist/air quality forecaster), lower NOx emissions at the expense of higher VOC emissions is NOT a good thing. We need to continue to reduce anthropogenic VOC emissions to as great of a degree as possible if the goal is truly cleaner ambient air.

This is why I tend to favor diesel engines, at least in the ICE realm, since they can use fuels that are virtually non-volatile, and are arguably the best platform for biofuels.

At stoichiometric ratio, the fuel takes priority over atmospheric nitrogen to react with oxygen . In this case, there is no need for EGR. Besides, the high amount of fuel also cools the combustion chamber prior to ignition.

At lean burn, there is too much oxygen for the amount of fuel. The excess air may have a cooling effect but not enought to reduce NOX at the flame front. Diesel engines (also petrol engines) realistically operates most of the time at part load / lean ratio. Diesel engines has a bad rap for high NOX since it is capable of very lean ratio. No wonder it runs economically plus, the energy density of diesel is higher than petrol.

MUSIC has a unique combustion chamber in which fuel can be sprayed in a timed manner to produce a stratified stoichiometric ratio at all time at the tip of the spark plug. It just varies the volume the air with stoichiometeric fuel near the spark plug. I think this is the maximum potential for internal combustion engine efficiency without sacrifing NOX emission.


It seems to be that you are an insider in European auto-industry. Maybe you could give me an answer to a question I just have got reading in different papers presented at
Could it be that Hybrid technology in Europe is not promeoted due to strategical reasons (e.g. support of agricluture) but also due to the absecne of European exelence in electrical engineering?
It seems to be that in promoting Diesel, "old-technology" orientated companies are able to work as ever. Old structures, old habitus survies. Motto: "Bizzness" as usual?
If Europe would promote Hybridisation, the European "Grosswirtschaftsraum" would not benefit as much as he does under the current conditions. With Hybridisation Asian battery and electrical companies would benefit but no Franco-German company.
What do you think?

John Schreiber

@ K
H2 ignites at extremely lean mixtures, promoting combustion of other fuels at ratios where they would normally flame out prior to complete combustion. NG will not provide this benefit, though H2 does improve NG combustion also at ultra lean ratios.

As far as the MUSIC thing goes, it has a lots of merit!
I think that this can work in a production environment without excessive cost. There may also be thermal efficiency gains available for exploitation.


I like your report on the said topic. it is very much impressive

gary davies

Carl, you submitted that you favour diesel over gasoline SI engines for air quality reasons, but surely the PM emissions of diesels are just as harmful to human health as the VOC's from gasoline?

Rafael Seidl

@ yesplease - not sure what you are driving at.

@ Gary Davies - the NOx production rate near the spark plug is as high as ever, but the concentration is diluted by the high AFR during the power stroke. Unfortunately, such extreme AFRs are only feasible at very lower power, e.g. when idling. At elevated power levels, AFRs need to be much lower. You then have to either deal with excess oxygen plus NOx aftertreatment, a complex EGR system or, throttling of the intake.

@ Mark - as I understand it, the spiral merely indicates the flow pattern of the gas in a cylindrical chamber with a tangential port.

@ Roger - the Ricardo approach involves mixing the cooled EGR with fresh air prior to compression in a turbocharger and subsequent intercooling. There are therefore multiple degrees of freedom for controlling the final temperature of the fresh charge as it enters the cylinder. This permits fine-tuning of the combustion rate and engine-out temperatures.

Ricardo claim - credibly, IMHO - that their system supports 20-30% EGR across the entire speed band of their engine. In particular, they do not need to enrich the mixture at high load and near rated power in order to protect the turbo and three-way catalyst.

@ michel - an absence of electrical engineering excellence? Bosch, Siemens VDO, Valeo, Hella, Continental etc. are all European companies with large market share in automotive electrical and electronic systems. No, there are IMHO four reasons for the general reluctance regarding hybrids:

(a) the Audi Duo flopped badly in the 1990s

(b) hybrids are no better than diesels in terms of fuel economy or performance. European emissions regs permit affordable diesels and, European car makers have a home advantage in that technology.

(c) Toyota has managed to monopolize hybrid technology in the public's perception. Even Honda is considered merely a distant second. Most others have encountered limited demand for their full hybrid offerings, partly because many are merely variants of existing SUVs rather than out-and-out fuel saver machines. Unlike Toyota, hybrid technology does little to burnish their brand credentials.

(d) Full hybrid systems remain very costly. Since European consumers already face much higher vehicle prices than their counterparts in the US, interest in full hybrids is muted. A few years ago, the German supply chain made a big push to upgrade the on-board gird voltage to 42V, but car makers decided against it due to cost and concerns about reliability.

However, there is currently a lot of momentum towards the widespread application of micro- and very mild hybrids. BMW calls this Efficient Dynamics and is including it in virtually every new model and model refresh. Citroen has offered a start-stop feature for longer but not on every model. Others, notably M-B, Audi, VW and Opel are following suit, mostly because of the EU's looming CO2 regulations. Look for similar features in their model ranges over the coming 12-24 months. The other major European brands won't be far behind. Electric hybrids are coming in Europe, but they will be less ambitious, cheaper and more ubiquitous than the flashy full hybrids favored in the US.

Also, remember that every turbocharged engine - including every one of the ~8.5 million diesel LDVs sold in Europe this year - is technically a hybrid, just not an *electric* hybrid. After all, what is a TC if not a very small singe-stage gas turbine with pneumatic power delivery?


Rafael, they claim their superior stratification eliminates NOx at high AFR and reduces it 80% over the drive cycle. Two things I don't understand:

1. Is the indirect combusion chamber actually a helix, or do their drawings simply show helical air movement inside a cylinder? I thought it was actually a helix, but their presentation seems to show the injector directly wetting the end wall, implying it's a cylinder.

2. How do they exhaust combustion products from the indirect chamber?


Of all the ICE innovations, this is the most promising and can be applied right away without significant increase in cost.

The combustion chamber is long and helical but does not necessarily be helical. It is mentioned about the advantage of tangential outlet. The injector is sprayed at the start of compression stage, pushing the mixture all the way to the dead end of the chamber where the spark plug is. The mixture is pushed inward by the further motion of the compression cycle. The fuel ratio is varied by varying the the duration of fuel injection.


"(a) the Audi Duo flopped badly in the 1990s"

They tried to make it work with lead-acid! Fair play to them for trying, but things could be different today with a couple of Altair batts and a 1.2L Lupo-derived genset.


@ Gary Davies – I’m approaching this from a U.S. perspective. Since all highway diesel vehicles sold in the U.S. since January 2007 (including all large over-the-road trucks) have been equipped with particulate filters (DPF), diesel PM emissions with respect to new vehicles are really no longer an issue, if they ever were.

All speciated ambient PM monitoring data that I’ve seen show that EC (elemental carbon – diesel PM averages about 75% EC) typically makes up only about 10% - 15% of the ambient PM2.5 mass, and there are a lot of sources of EC other than diesel engines (gasoline exhaust PM is about 25% EC by mass, electric generation plants, wildfires, etc.). OC (organic carbon) typically makes up the largest percentage of ambient PM2.5 mass.

Which bring up another issue regarding anthropogenic VOCs – the production of secondary organic aerosols (SOA). VOCs oxidize in the atmosphere to increasingly low vapor pressure products which in turn increasingly partition to the particle phase by homogeneous nucleation (nanoparticles) or condensation on other ambient particles (heterogeneous nucleation - mostly ultrafine PM). These SOA form primarily from gas-phase hydrocarbons with carbon number greater than or equal to six. Since gasoline is largely made up of hydrocarbons with a carbon number greater than or equal to six (I think, someone please correct me if I’m wrong), evaporative gasoline emissions are potentially responsible for significant contribution to the ambient PM2.5 inventory.

SOA yields of 5% - 10% have been estimated for reactive VOCs (ROG) like gasoline, with aromatics on the high end of that scale. According to the USEPA, in 2002 there were over one million tons of evaporative gasoline vapor emissions in the U.S. from the distribution, refueling, and storage of gasoline, meaning that at least 50,000 tons of organic PM2.5 (as SOA) potentially were produced in 2002. For comparison, there were 99,000 tons of direct PM2.5 mass emissions from highway diesel vehicles in 2002 according to the same USEPA report, but that is expected to be reduced to about 10,000 tons/year by 2030 just from emission controls on highway diesel engines currently in place, according to the USEPA, meaning that SOA from gasoline evaporative emissions will potentially be a much larger source of ambient PM2.5 than highway diesel engines by then (and that’s not including the direct PM emissions from gasoline vehicles, which will continue to climb unless particulate filters are required on them too sometime in the future).

Granted, there is a cost penalty associated with these clean diesel engines, but they now have less of an environmental impact than even the latest equivalent versions of gasoline engines based on consideration of all associated emissions (again in my opinion).

Indirect combustion chambers are less efficient than direct injection due to thermal and pressure loses, more in this case with a refrigerated spiral path.
¿Do the gains from lean burn and unthrottle compensate those loses?.
¿Is it possible to have an scheme of unthrottled GDI?

Roger Pham

"Indirect combustion chambers are less efficient than direct injection due to thermal and pressure loses, more in this case with a refrigerated spiral path.
¿Do the gains from lean burn and unthrottle compensate those loses?.
¿Is it possible to have an scheme of unthrottled GDI?"

The answer to your two questions are stated in the article: "The MUSIC engine has demonstrated part-load efficiency equal to diesel...", or ~20% gain over conventional stoichiometric-combustion engine." Apparently the efficiency loss in the indirect combustion chamber is minor in comparison to the efficiency gain.

Have ye no faith in EPA and CARB? Apparently, they had all your concerns figured out already, IMHO. Annual car inspection involve a test of the gas tank cap for leakage. All cars have system for preventing evaporative gasoline emission into the air. Summer gasoline batch has much less vapor pressure than winter batch. The fuel filling spigot at the gas station has a system for absorbing the evaporative emission resulting from gasoline filling.


I am a bit confused about that you wrote. Is it technical correct to call electrical generation and storges system in a car for purposes other than propeling the car Hybrid technology? That BMW ( and the supply industry named in your statement) and other did is just having improved the electric generator. In my view it is inadequate to call this Micro Hybrid.
The electrical energy is not used to drive a electrical motor that propels the car. The energy is just used to start the IC-engine. This is not new.

Than AUDI worked on the Hybrid in the 90s, they depended on Pb-batteries. Maybe VARTA? As a matter of fact, modern batteries in Hybrid cars are made in Asia. The batteries a one of the most expensive parts in a Hybrid car. So, in the value-added chain the battery is out of "Grosswirtschaftsraum". This is bad.

There is another factor. I think it is not very important wheather a car costs 2500$ more in the 30.000-100.000$ range. Especial in a certian segment: Premium and Lux. So, to put more technology in a car is very good. It is value adding. Industry as supply industry can suck in the money wealthy people have accumulated. Who knows that these people would do with this money? Building bigger houses that wast more energy? As long as the get clean cars for the money, it is good for everyone. In production and in finace. And it is good the money is used to improve air quality in cities within the current discourse. People spent 3000$ for SatNav. Why not also spending the money on clean technology that actuelly propels the car since SatNav is down to 200$ now.
Clean air: The most important matter? Or not. Oh yes, for car industry it is easier to implement a touchscreen from supply industry in the dash bord. But to change the architecture of a car and production is another story.
Only Toyota had the courage to do that.

John Schreiber

@ Carl

My sources in the US new truck industry tell me that the new clean diesel trucks are not selling. It is believed that many fleet operators will rebuild their chassis rather than buy new. 2007 is possibly the worst sales year ever.


@ John – that’s also my understanding. However, the point of my first paragraph in the preceding post is that even before any of these new diesel trucks were marketed, diesel PM (DPM) made up a relatively small portion of ambient PM2.5. Plus there are programs to retrofit older trucks with DPF. Just the switch to ULSD has cut DPM by 10% according to EPA and cut emissions of nanoparticles (the smallest particles) by a factor of four, from the existing fleet. So DPM will apparently become a smaller and smaller portion of the total ambient PM2.5.

@ Roger – I have faith in the EPA (for the most part), not so much in CARB. The evaporative emissions that I’m referring to are in addition to the evaporative emissions from the vehicle itself (“upstream” emissions), so even gasoline cars certified as PZEV are indirectly responsible for these emissions. These are the evaporative emissions from bulk storage tanks, filling and transporting a load of gasoline by tanker truck to a gas station, unloading the tanker load of gasoline, storing the gasoline in tanks at the gas station, and finally, refueling a car at the gas station.

Are you familiar with EPA’s AP-42? It has emission factors for virtually everything imaginable. Chapter 5 deals with “Transportation And Marketing Of Petroleum Liquids” and has emission factors for each of the steps I outlined above. If my math is correct, there are approximately 9.6 pounds of evaporative gasoline emissions per 1000 gallons of gasoline handled during these steps. That’s assuming the latest and greatest in vapor emission control, e.g., Stage 1 and Stage 2 emission controls at gas stations.

According to that same source, evaporative emissions for diesel fuel under the same conditions amount to 0.0464 pounds per 1000 gallons of diesel fuel, i.e. a reduction of over 99.5% by mass.

According to the USEIA, current gasoline consumption in the U.S. is something like 140.5 BILLION gallons. In my opinion, this is a significant source because of the reactivity of gasoline vapors with respect to ozone (smog) production, and the secondary formation of formaldehyde and SOA.

Rafael Seidl

@ Michel -

BMW actually avoids using the term hybrid in connection with its Efficient Dynamics package, because so many people have their own pet definition of it. Valeo does call stop-start functionality a micro-hybrid, so I suppose you can play the definitions game until you're blue in the face.

The BMW system does indeed not directly boost engine torque. It does, however, remove parasitic loads from the engine, so a few extra hp make it to where the rubber meets the road. It also recuperates energy during coasting and braking.


Amazing. Dr. Merritt rediscovers the stratified charge engine concept. Based on his tech papers and patents, it appears that he will be as equally successful as the dozens of others who have previously discovered the stratified charge engine.

Someone should explain to him that a pre-chamber engine has more drawbacks than benefits. That's why diesel engine designers avoid them.

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