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Mahle Highlights Downsized Engine Concept

The Mahle downsized engine concept. Click to enlarge.

Mahle, an automotive supplier headquartered in Stuttgart, Germany, showed a new 1.2-liter engine downsizing concept as a technology demonstrator at the Frankfurt Motor Show. Mahle presented the unit in two different supercharging models (single and double).

In its variant with double supercharging, the 3-cylinder power unit developed by Mahle Powertrain achieves 120 kW, or 163 hp/liter. By cutting the displacement in half compared to a 2.5-liter displacement engine commonly used to power a mid-range car, fuel consumption is lowered by more than 20%.

A further advantage of downsizing is that small-displacement engines are operated mainly in upper load ranges, where the engine’s efficiency is higher.

In addition to the charging technology, the engine uses forged pistons, two overhead composite camshafts, four valves per cylinder, direct injection, air-water charge cooling, exhaust gas recirculation cooling, injector tip cooling, dual camshaft adjustment, and cooled lightweight valves. Another technological highlight is the fully integrated intake module, which accommodates the oil mist separator, air filter, noise damping, and exhaust gas recirculation.

To consistently minimize fuel consumption, frictional loss was also drastically reduced. The engine concept, for example, uses DLC-coated (DiamondLikeCarbon) piston pins, cylinder running surfaces coated with NIKASIL, and PVD coated (Physical Vapor Deposition) piston rings.

Mahle exhaust gas turbocharger.

New exhaust gas turbochargers. Mahle will begin series production of a line of exhaust gas turbochargers for gasoline and diesel engines in 2010. Mahle is presently developing wastegate exhaust gas turbochargers in the engine power class up to 200 kW for gasoline engines and Variable Flow Turbine (VFT) turbochargers for diesel engines with a maximum engine power up to 150 kW.

Mahle SLV-R EGR valve.

New EGR. Mahle is also introducing a new EGR technology based on a rotating fast-switching charge air valve (SLV-R). In this system, an electromagnetic valve with rotating flap movement is positioned in the fresh air line upstream of the EGR inlet point. By briefly closing the valve, a temporary vacuum is generated on the charge air side, which creates the necessary pressure gradient for exhaust gas recirculation. An advantage over conventional EGR valves is that the charge air valve is installed in the fresh air path and is consequently not directly exposed to the recirculated exhaust gas. This minimizes thermal stress as well as pollution of the valve. In addition, the continuously rotating movement of the flap ensures simple control and a long service life.



This is the direction we need to be going.

No excuse for those big noisy monsters. US car companies and automotive magazines have brainwashed the American public.


Additional tweaks for the ICE can not change the basic design faults of a reciprocating engine. Small gains in efficient are possible but an ICE that is economical to build for the mass market in general waste 70 to 75% of the potential energy contained in the fuel.

There are lots of examples of these kinds of modifications and they are damn interesting. But, the modifications are often too expensive or too complicated to prove acceptable for market use.

Still we are stuck with the ICE for some time to come and anything that reduces our use of oil is a positive step.

Rafael Seidl

This is the first time Mahle has gone beyond core components such as pistons and delivered a complete engine. The main reasons they chose a three-cylinder design may have been heat loss to the coolant and, the fact that the lower size limit for twin-scroll turbos is presently above the diameter needed for the high-pressure unit in a sequentially charged engine of this power rating. In a four-stroke engine, three cylinder is the most you can combine in a single scroll if you want to avoid crosstalk in the exhaust manifold unless you also implement HCCI (as Mercedes did in their sequentially turbocharged DiesOtto).

Ricardo recently published research on I3 gasoline engines featuring low-pressure EGR, which permits rates of 20-30% at all but the lowest engine speeds. That means the air-fuel mixture does not need to be enriched near rated power merely to protect the turbocharger(s) against damage. Mahle may be doing much the same thing with the help of its new EGR valve, in which case there may not even be a water jacket around the turbine volute - high temperature resistance is the primary reason turbos for gasoline cars are usually much more expensive than those for diesels.

The small package size of an I3 relative to an I4 does make it a lot easier to fit a larger/extra battery or supercap pack for micro- or mild hybrid variants. However, I expect this Mahle engine also includes an inertial compensation shaft, as inline threes run unacceptably rough without them - especially for vehicles in this power range. Such shafts are usually placed in the oil carter, with a special oil grade containing an anti-foaming agent. With inertial compensation, the manufacturing cost of a small I3 is almost the same as that of an I4 of the same displacement which is doesn't need one.

The torque curve of a sequentially charged engine is typically flat over much of the engine speed range. The ECU imposes an artificial limit near the theoretical maximum, to keep mechanical stresses manageable with the amount of material permitted by weight and cost targets. Full torque is probably available at speeds as low as ~1600RPM, which means you can use early shift points and long gear ratios in the transmission to deliver the required power at relatively high efficiency (moderate throttling). Only in combination with such downspeeding can drivetrain designers maximize the fuel economy benefits.

Even so, any manufacturer interested in leveraging Mahle's effort will need to convince customers that a small engine packing a lot of punch is at least as good and will last at least as long as a larger, conventional power plant. Over the decades, European car brands have invested a lot of marketing funds to persuade buyers that more cylinders and more displacement are always better - or at least more prestigious. Now, looming CO2 limits are forcing them to begin reversing that message.

gavin walsh

the Greenpeace Smile concept car (which was designed with mass production in mind) used a small supercharged engine as a way to reduce fuel consumption over 10 years ago. It is sad to see how long these ideas take to enter the mainstream.


The small package size of an I3 relative to an I4 does make it a lot easier to fit a larger/extra battery or supercap pack for micro- or mild hybrid variants. However, I expect this Mahle engine also includes an inertial compensation shaft,

Can't you drop the intertial comp in mild hybrid applications and use the motor to smooth things out, a la Honda Insight?



10 years ago most manufacturers put a hold on their small engine turbocharged gasoline engines in the US while they came to grips with the LEV emission requirements. Now they can easily have a turbo gasoline engine meet emissions requirements so we may be more likely to see more of them here now.

Rafael Seidl

@ doggydogworld -

afaik, the Honda Insight was a parallel hybrid with integrated motor assist (IMA), essentially an electric machine mounted directly in-between the engine and the transmission. In such a configuration, the electric machine can - at best - be used to dampen out torsional vibrations. In a conventional drivetrain, a torsion damper is generally used instead.

In an I3, what you are compensating is for is a free moment of the first engine order, perpendicular to the plane of the cranktrain. There is also a moment of the second order, but given the low displacement of most I3 engines, it is not compensated for.

The compensation system has to rotate at the same speed as the crankshaft but in the opposite direction. This is why an IMA cannot do anything about the free inertial moment.

BAS systems cannot track crankshaft angle accurately enough over time, so they cannot be used either - even if you add a pair of spur gears to reverse the direction of rotation. To maintain the mounting position to the side of the engine, you'd have to use a chain instead and expose the rotor to the full torsional vibrations of the crankshaft. The chain would be loaded twice as heavily. Moreover, compensating for the free inertial moment in a plane parallel to that of the cranktrain means you'd be exacerbating the crankshaft's torsional vibrations.

Note, however, that AVL List recently published research on an I3 design that achieved inertial compensation with just a set of spur gears at either end of the engine, located in the plane of the cranktrain. Attached to these four gears were unbalanced masses. This solution is lighter and avoids the usual spinning shaft in the oil carter but it requires four gears instead of two. Gears are more expensive than shafts and bearings.

Roger Pham

For all the above reasons that Rafael discussed, I think that the Fiat 2-cylinder turbocharged engine as featured recently is more cost-effective, and if it's scaled up slightly, will deliver the power of this 3-cylinder engine.

Rafael Seidl

@ Gavin Walsh -

the SmILE concept was indeed far ahead of its time. Based on two-cylinder gasoline engine with just 300cc, it is arguably still ahead of its time today.

Note that it featured a single-stage pressure wave supercharger (aka wave rotors in the US) rather than sequential turbos. PWSCs very briefly bring exhaust gas and fresh air into direct contact in short channels located parallel to the axis of rotation of the rotor they are in. The system exploits the fact that pressure waves travel at the local speed of sound, much faster than diffusion processes. With careful design, the efficiently compressed air is pushed into the downstream intake manifold port just before the diffusion zone gets there. The motion of the rotor then causes the port to close, so the wave bounces off the casing and travels backward toward the downstream exhaust manifold port. As it escapes there, it creates a partial vacuum in the cell, which is used to refill it with fresh air from the upstream intake pipe. In addition, some air is pulled right through, which is why the exhaust gas downstream of a PWSC is always lean even if the engine operates at lambda=1.

Note that a PWSC exploits exhaust pressure directly and does not depend on high mass flow. A single stage can therefore deliver boost levels of 2.5-5 even at low engine RPM. For passenger car applications, 2.5-3 is about the limit, as higher levels imply lower efficiency, higher temperature loading and severe NVH problems.

In the late 80s/early 90s, control strategies for PWSCs were still inadequate, leading to significant levels of transient hot EGR if the throttle was opened too quickly. If you depressed the gas pedal too quickly, engine torque would drop before it rose to the desired level. This was generally considered unacceptable for mass production, though with a few tweaks industry maverick Mazda did install them in about 150,000 626 Capella diesels for the Japanese market. Opel abandoned the concept for its Senator diesel model rather more quickly.

Now, several dissertations later, ETH Zurich and SwissAuto Wenko AG (both in Switzerland) claim to have solved the control issues related to EGR and, to have optimized other aspects peculiar to PWSCs, such as effectiveness over a wide engine speed range and NVH issues.

They address the emissions issue for gasoline applications by positioning the three-way catalyst upstream of the PWSC rotor, with an optional additional two-way catalyst downstream of it. As explained above, PWSCs are far less sensitive to low exhaust temperatures than turbos are.

In terms of high-volume manufacturing cost, a PWSC should compare favorably to sequential turbos delivering the same aggregate boost level and similar response dynamics. With just a single stage, intercooling also becomes easier. Finally, PWSCs can be applied to inline fours, whereas small-diameter single-scroll turbos for the high pressure stage are limited to three cylinders each (unless you also implement HCCI).

The main reasons PWSCs remain so exotic are:
a) most engine developers are unfamiliar with the technology incl. the power and emissions control strategies
b) those that are had a generally negative experience 15-20 years ago
c) the car industry loathes being told how to build cars by environmental pressure groups like Greenpeace
d) the boost levels produced by PWSCs and sequential turbos were not considered necessary until very recently

I would not be surprised if someone were to give PWSCs a second chance sometime soon.


Rafael, you're the man! Thank you for your informed commentaries...


I appreciate the information on power trains found in the postings and find then very interesting. Enough so that given you need an ICE generator for a serial hybrid, I have wondered for some time what engine configuration would be the correct one to use to maximize the efficiency of the engine and minimize the space and vibration. Would a radial engine fill the need? a two cylinder boxer? I think that GM is planning an I3 for their car.

gavin walsh

huge thanks for that very educational and informative potted history of PWSCs in automotive applications; it seems like there aren't any showstoppers for this technology on the technical side any longer. However I wanted to comment on bullet point c):
"the car industry loathes being told how to build cars by environmental pressure groups like Greenpeace"

I understand that NGO's can sometimes make loopy suggestions and not realise the cost and logistics implications of their suggestions (for instance, suggesting all car bodies be made of magnesium would be a hypothetical example) but in the case of the Smile car it seems like Greenpeace really came up with something innovative that the car companies should have come up with themselves; apart from the PWSC there is no rocket science in their suggestions, such as cutting structural weight and improving aerodynamics while not compromising crashworthiness. Frankly if they had taken on board Greenpeace's suggestions at the time they were made we might already have 100mpg cars in showrooms.

gavin walsh

"what engine configuration would be the correct one to use to maximize the efficiency of the engine and minimize the space and vibration. Would a radial engine fill the need? a two cylinder boxer?"

IIRC the Greenpeace Smile car used a 2cyl boxer arrangement.


I remember Ferrari tried once with a PSWC in a F1 car, it was licensed from Brown Bovery.
Perhaps they try again with their Millechilli prototype where the idea is less weight, less cylinders, less CO2.


The Ferrari unit was manufactured by Comprex (part of ABB).

With modern model based control strategies and electronic control of the pressure wave reflection pockets, it ought to be very simple to start to make serious progress with PWS once more. Perhaps with the re-introduction of turbos in F1 (exhaust energy recovery systems are mooted for >2010), then perhaps we will see further progress being made in this area.

Since we're talking of boosting systems, I wonder if I should write an article about our SuperGen device Raph?

Rafael Seidl

@ Gavin Walsh -

in pure engineering terms, the SmILE concept was very innovative. But you have to keep in mind not only that engine designers have egos and careers, but also that the suits are looking at maximizing revenue and profit per vehicle sold. That combination proved to be a lethal case of "not invented here" for the SmILE.

Rafael Seidl

@ Lad -

the whole point of a series hybrid with a large battery buffer, i.e. a PHEV once the energy ingested from the grid is used up, is that the engine does not need to deliver the response dynamics nor the speed and torque range of a regular ICE. Indeed, since we're talking about a genset, the output of the combo is electricity, not shaft power.

The focus can therefore be on mechanical simplicity, low emissions, low noise, multi-fuel capability and high thermodynamic efficiency.

A hermetically sealed Stirling engine with four free pistons and linear generators on the cold side would fit the bill. In a Siemens/Rinia alpha-type Stirling, the hot pole of each cylinder is connected to the cold pole of the next via a recuperator, forming a circular topology. The motion of each piston is phase-shifted 90 degrees relative to its neighbors.

Ironically, hydrogen would be used not as fuel but rather, as the working medium. That implies using materials such as austenitic steels and special elastomers that are not prone to hydrogen embrittling. Helium, which is compatible with cheaper materials, only has half the specific heat capacity. The only way to compensate is to increase the mass of the working medium, i.e. doubling the working pressure. That increases the weight of the device, not something you want in a mobile application.

Instead of the usual swash plate linkage (cp. United Stirling 4-95 or WhisperTech WhisperGen), the phase angles of the pistons would be managed by the power electronics.

By using the linear alternators as motors during short intervals in the cycle (negative damping), fourth order harmonics can be superimposed on the natural resonance of the core mass-spring system. This would permit a much better approximation of the ideal thermodynamic cycle, raising efficiency. Such negative damping would probably require fast supercaps to shield the battery from rapid shallow cycling.

With or without this optimization, output from such a genset would be two-phase AC. This gets rectified by the power converter before the inverter stage produces three-phase AC of the desired frequency.

Hermetic sealing eliminates the biggest headaches of Stirling designs: leakage of the working medium, lubrication of moving parts and, contamination of the working medium by lubrication oil. That should bring both the weight and the price down substantially. Infinia produces low-power single free-piston Stirlings, see this animation:

The hot and cold poles of the machine are at the right and in the center, respectively. The linear alternator is on the left. Note the use of leaf rather than spiral springs in this particular design.

Unfortunately, the solution I have proposed does not yet exist on the market. Free piston design are fairly new because the control systems technology required did not exists until recently. Stirling engines in the 20-50kW power range are very rare, because with shaft output they cost 2-3 times as much as a diesel engine and only achieve comparable thermodynamic efficiency in the real world. PHEV applications could conceivably create a market for hermetically sealed designs in this power range.

Rafael Seidl

@ Ruaraidh -

I'm sure we all would appreciate a short write-up about it, especially if you point out how the device can be used to improve emissions and/or fuel economy. Which engine types would benefit most: petrol, diesel, rotary?Which other fuel saving concepts (stop/start, hybrids, plug-in hybrids) is or isn't it a good match for? You may also want to talk a little bit about how it compares to alternate boost strategies, e.g. electrically assisted turbos.

I found this related article on the web:


You can also look on our microsite.

Essentially, SuperGen combines the best bits of a power split trans driven radial flow compressor ie variable compressor drive ratio with stop start and mild hybridisation.

This means that you can have full boost at very low speeds with extremely quick (<0.2s to full boost)response which allows both downspeeding ie higher gear ratios and downsizing.

Hope I don't get a ticking off for commercial use of the blog or something as I think it's something that readers would enjoy.

I'll write something up for the site.

willem hunter

I am looking for specs on a eng 587n4 or aw14 mahle i doo not know hoo buld it can jou help place Willem Hunter


Can anyone tell me what is difference between hotside and coldside EGR valves? What are the plus and negative sides of both?

Wheel two Wheel Car Tuner Company in the US introduction movie of the Antonv dual-speed supercharger for the Hummer H3.

Homepage of Antonov Technology fansite:


Demonstation movie of the Antonov dual-speed supercharger: (Chevrolet Lacetti).
Owner of a IS200 Lexus with the antonov dual-speed supercharger.


Dear sir.

I read a lot of technologies for downsizing engines/Co2 reductins with the use of a superchager.
Last year the Antonov company invented a supurb duals-speed supercharging system.

They claimed that cars have a very great boost (more then 58% boost/torque) then a normal supercharger system. This technology is a great help for downsizing of engines and Co2 reductions.

In herwith I have enclosed some links about this new supercharger technology.
Question: Can you give an opinion or your thoughts about this dual speed supercharger technology.

Antonov company website concerning the dual speed supercharger system:
Homepage Antonov company:

Demonstation movie of the Antonov dual-speed supercharger: (Ford Mustang and pitures dual-speed supercharger).

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