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New Bosch start-stop system with coasting mode can reduce fuel consumption by up to another 10%

Bosch has developed a new start-stop system with coasting mode; the system stops the engine when the vehicle is traveling at speed, helping to reduce fuel consumption by up to 10%. The function can be combined with any type of combustion engine.

First generation start-stop systems stop an engine only when the vehicle is completely stationary; enhanced versions of this start-stop system cut the engine as soon as the vehicle is coasting to a halt—e.g., at a red light. In contrast, as soon as the driver’s foot is off both the gas and the brake pedal, vehicles equipped with the new start-stop coasting function stop the engine while the vehicle is in motion. Because the engine is disengaged, the vehicle can coast for longer than it could with an overrun fuel cutoff system, for example.

Whenever the vehicle can maintain its speed simply by rolling—for example, on a gentle incline—the engine is stopped. As soon as the driver touches the gas or brake pedal, the engine starts up again. Tests carried out by Bosch have shown that the combustion engines runs needlessly about 30% of the time, meaning that the vehicle could simply coast for about a third of every journey.

Although these phases are not taken into account in the New European Driving Cycle (NEDC), under real traffic conditions the function will give drivers a roughly 10% fuel saving.

Much of what enables the system innovative is its enhanced software and the use this makes of existing sensor data. Furthermore, the start-stop starter has been configured to cope with greater loads and to deliver faster restarts.

With double-clutch transmissions, Bosch noted, some vehicles already have a “light” version of the coasting system on board. As soon as the drivers take their foot off the gas pedal, the system switches the engine to idle. While this means the vehicle is doing no more than rolling, it is still consuming fuel in order to keep the engine ticking over.

Bosch is confident that start-stop coasting will soon become an everyday feature in cars—just like air conditioning.

—Dr. Rolf Bulander, member of the board of management of Robert Bosch GmbH

Bosch is embedding fuel-saving functionality in many of its products. One example is eClutch, which makes it possible to offer the coasting function even in vehicles with manual transmissions. As soon as a coasting phase is possible, eClutch decouples automatically and the engine is stopped.

The coasting function is also available as an add-on for the Bosch entry-level hybrid, the boost recuperation system, to help it save even more fuel. Equipped with a more powerful generator and a compact lithium-ion battery, the 48-volt hybrid saves around 15% of fuel through electrification alone. In real traffic conditions, and fitted with the coasting function that shuts down the engine, the hybrid can achieve fuel savings of an additional 10%, or 25% overall.



Im interrested to buy.


The Camry HEV does that very well.


Sure, Harvey but the margin that Camry HEV has shrinks considerably. When also second generation, e.g. 9-speed, double-clutch transmissions and the “entry level” hybrid systems, as mentioned by Bosch, are introduced on a large scale, then the additional advantage of a full hybrid will be minimal. How could the very high incremental cost of the full hybrid be motivated then? In addition, we have limited supply of rare elements needed in HEVs and EVs. If we use less in each car, we will have enough rare elements for all cars. In that context, EVs seem as the most stupid of all options.


I always believed that there could be interesting "tie in's" to GPS technology. For example, if you are lifting off the throttle and there is a known stop sign ahead, the GPS, coupled with the stop/start system would assist the system in cutting the engine at the first sign of "lift throttle". Same goes for regular commute patterns, and, of course rates of acceleration. I'd love to see an optional or selectable preset "most efficient" reasonable "acceleration rate" based on location on the road. 35MPH zone, vs highway on ramp. Even if it's just a tactile, detectable throttle detent that can be easily ignored if necessary.

Systems like this could work for electric cars as well as conventional.


@Peter XX ...we paid no extra for our Camry XLE Hybrid over the regular ICE Camry XLE. Ford's Lincoln MKZ offers the same deal.

However, I agree with you that fine tuned ICEVs will eventually challenge HEVs by using many of the same technologies.

The real race (by 2020 or so) may be between BEVs and PHEVs (with ICE or FC range extenders).


Start-stop micro hybrids require less in the way of batteries than anything else, so can cut total fuel demand more so long as battery manufacturing is a constraint.

There's also the detail that 48V electrical systems can electrify accessories that a 12V vehicle needs to drive with belts.  Moving the A/C compressor, power steering and even superchargers off the engine makes packaging more flexible, power demand easier to manage and enables further efficiencies.

Nick Lyons

Micro-hybrid technologies like this are the near-term future for the vehicle mass market, IMHO. Meeting fleet fuel economy mandates will require cost-effective efficiency improvements to the whole fleet.


I do not know what kind of a deal you can get in Canada but we both know that full hybrids are more expensive to produce than conventional ICEs. This is true for all of the few models in Sweden where we can find comparable full HEV and ICE options. When a dealer announces that a hybrid version (or BEV?) is cheaper, I will send my congratulations to you. I might even consider buying…

In contrast, “simpler” parallel HEVs (micro/mild hybrids) might become cost competitive in a foreseeable future. As we can see in this article, they acquire more and more of the features previously only associated with full hybrids. Actually, I cannot see the breakthrough of full hybrids in the near future – at least not in Europe, simply due to the cost penalty. The potential for substantial market penetration seems much greater for micro/mild hybrids. Thus, I fully agree with Nick.

Liviu Giurca

Unfortunately, in the most countries the electric energy from the grid is not enough green to supply a large pure electric vehicle market. So, for the moment (and ten years far) is not recommended for environment to produce them in a large number.

On the other hand, if an usual electric vehicle has limited performances and can be accepted by client, why we can not manufacture and sell a Micro Hybrid Vehicle with limited performances, avoiding range anxiety, being cheaper and more friendly with the environment? I think this will be also accepted by clients

Let’s define the Micro Hybrid Vehicle specification with limited performances.

Vehicle performances:
1.Maximum speed - 140 km/h.
2.Acceleration - 11 - 14 s to 100 km/h.
3.Four persons and 50 kg charge.
4.Climbing constant speed - 90 km/h in highway at 7% slope with four persons and 50 kg charge.
5.Cx = 0.3
6.S=2 m²
6.Four stars at Euroncap (because of weight issue).
7.Vehicle weight (no charge): 750 – 800 kg.
8. Fuel type can be: gasoline, Diesel fuel, biofuel, LPG, CNG or hydrogen.

Powertrain type:
1. Electric Micro Hybrid: This technology has a starter-generator system coupled to a conventional engine. An electric motor provides stop-start operation of the engine, plus regenerative braking to charge the single battery. Compared to conventional vehicles, returns fuel savings of up to 10% in city driving.
2. Mechanical Micro Hybrid: the transmission or the engine is coupled with a small flywheel which provides stop-start operation and regenerative braking. Compared to conventional vehicles, returns fuel savings of up to 18% in city driving and improve accelerations.
3. Pneumatic Micro Hybrid: The engine is transformed in a compressor during braking, charging an air tank (regenerative braking). The compressed air is used later (in acceleration) to supercharge the engine. Can provide also stop-start operation. Compared to conventional vehicles, returns fuel savings of up to 20% in city driving and improve accelerations.

Engine type: Opposed Piston Engine four-stroke or two-stroke which can be fully balanced even with a single cylinder (and two pistons) – see . This has high effective efficiency of around 50% (because of the extended expansion stroke and the missing of the cylinder head) and big power density (some of them offer 2.5 kW/kg). The Variable Compression Ratio adapted at this engine is cheap, reliable and increase the range of the optimum efficiency. Necessary power around 37 kW (50 hp). The downsized engine capacity between 0.2 – 0.5 l with one cylinder (and two pistons). Engine weight: 15 – 30 kg. Specific fuel consumption around 170 – 200 g/kWh.

Transmission type: 5 or 6 speed gearbox simple or dual clutch automatic. Gear box weight 15-20 kg.

Which will be the medium fuel consumption in this case? Exactly 2 l /100 km or even below.
Around 2 l /100 km or less, respectively 50 gCO2/km.
Which will be the price of this vehicle? Maximum 10.000 $.


The problem with most current 'micro hybrids' is the very low efficiency gain and very low braking energy recovery.

1. Yes, a mechanical flywheel or a few up-to-date ultra caps or high energy density quick charge batteries could recover more braking energy and increase overall vehicle efficiency.

2. Yes, a small more efficient ICE or range extender would certainly help.

3. Yes, improved vehicles design with smaller more efficient ICE and less weight would also help.

For total vehicle price, a small three-wheeler may be a valuable compromise @ $10K if built in the right place.


"This puts pre-incentive prices for the base-model Prius Plug-in Hybrid at $29,990"

So, four of four full hybrid Prius models start under the US new car $32,700 average price.

Historically, mechanical power progress and value can't begin to compare with electric system advances.

in the most countries the electric energy from the grid is not enough green to supply a large pure electric vehicle market.

That's not a problem.  There are synergies between EVs and improvments to the electrical grid, such as dynamic charging, DSM and V2G.  Most places have enough excess grid capacity for EVs to go at several percent of sales for some time before any change is necessary, and if the groundwork is established beforehand those EVs can support de-carbonizing changes in the grid mix that would be harder to do without them.

Micro hybrids have very limited energy regeneration capability.  Hydraulic hybrids are superior to electric for some applications, such as city taxis; they have lower round-trip losses and higher power/weight.


We missed the small government incentive for HEVs by a few months but we did better with the manufacturer + local retailer incentives of $4.5+K and free winter wheels, caps and tires, for a cash purchase without trade-in. The total price was the same as the regular price for the non hybrid equivalent model.

After 3+ months and 5,000+ Km, fuel consumption has stabilized very close to Toyota's claim. Urban and highway fuel consumption is the same, as claimed.

Hybrid production cost must have come down at Toyota (Camry-Hybrid) and Lincoln (MKZ-Hybrid)?

Roger Pham

Not surprising, since Toyota's HSD is very simple with far fewer moving parts than a 6-speed automatic transmission. The gear-shift transmission is eliminated, along with the alternator, starter, and lead-acid battery, as well as accessory belts. There is no belt at all in new HEV's, which will reflect higher level of reliability and lower maintenance cost. Accessory belts have been source of aggravation with noise, slippage, and a common cause of car breakdown on the road.

The cost premium for HEV til now may reflect recoupment of development cost and cost of new assembly lines and factories. As batteries and power electronics will get cheaper, we will see that HEV's cost will get closer to the cost of an equivalent ICEV. Plus, gear-shift transmission is getting more complex with more and more gears and dual clutches...etc.

Roger Pham

Not to mention that alternator, starter, and lead-acid battery are also sources of frequent aggravation. Transmission repair or replacement is quite expensive. The brake pads in HEV will never need replacement due to infrequent use.

Richard C Burton

ah, but don't forget that the Prius has a transmission to wear out too-my brother's 2006 tranny went out at about 160,000 miles and it was going to be a $4000 repair when Toyota decided to cover it for him(far beyond normal warranty, with the admonition that he was lucky they covered it...)and he had to replace his "special" lead acid battery at the same time to the tune of about $300!

Roger Pham

The Prius only has a single-stage planetary power split gear set, not a gear-change transmission. As such, there are no bands, no wet clutches, no actuator to wear out or to burn out. The planetary set cannot wear out prematurely unless the oil leaked out or oil level not checked. This is maintenance issue, and very rare to happen. The lead acid battery is very small and cheap to replace, and one should not go to the dealer to get price gouged!


"Coasting"??? What a concept! Except the majority of J@ck@$$e$ out there in their over-powered
FUmobiles will still race you to every red light or do anything to pass you in heavy traffic. All the technology in the world is worthless with a loose nut behind the wheel.


fred....most future vehicles with autonomous drive will fix that problem by identifying and evaluating the human driver and possibly 'shock' the loose nuts (5% to 10% of current drivers) to the back seat or freeze the vehicle.

Most traffic cops could be doing something else, like fighting other crimes?


Harvey, I wish that future vehicles with autonomous drive (or autonomous vehicles with future drive?) would really do that. Better to have better highway planning. The UK has "kill speed" signs that simply change the speed limit when traffic density changes. Traffic pulsing involves putting a stoplight at on-ramps to gently insert traffic wherever there is a space on the main highway. How aboutbi-directional traffic lanes, now an absolut necessity in Cali? Leadfoot syndrome can be eliminated with proper driver training, but as with other things, everyone will be asking "What's in it for me?"


'What's in it for me' could be:

1. 50% to 75% less road accidents
2. 50% to 75% less property damages.
3. less traffic jams and reduced travel times.
4. much lower car insurances.
5. 50% to 75% less road injuries and fatalities.
6. 10+% less fuel consumption.
7. 10% less harmful emissions.
8. lower GHG and reduced climate change rate.

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