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Integral Powertrain Developing New Variable Ratio Drive B-ISG System for Stop-Start Applications

VR-Pulley iso section
A variable ratio pulley allows improvements in cost and functionality. Click to enlarge.

UK-based engineering consultancy Integral Powertrain has developed a new generation of belt-integrated starter generator (B-ISG systems) for stop-start applications using a new multi-mode, variable ratio drive pulley. The company anticipates that the total CO2 reduction achieved by the system will be greater than that possible with current B-ISG systems.

The core of the new system is the Variable Ratio Pulley, which packages a two-ratio epicyclic gearbox into the belt drive pulley hub. To start the engine, the high ratio (3.1:1 in the development system) is engaged to substantially reduce the torque requirement, allowing a medium-sized diesel engine to be cranked without the need for a high belt tension and the associated friction and wear.

Existing B-ISG systems provide refined stop-start operation, but they have significant disadvantages. This is mainly due to the requirement to generate very high torque and transmit it through the accessory belt, which impacts cost, packaging, weight and efficiency. A further issue is that engine-off comfort is compromised unless an expensive electrical air conditioning pump is fitted.

—Integral Powertrain technical director Luke Barker

Tests have shown that engine start with the Integral system occurs in less than 0.3 seconds. When the engine is running, the ancillary drive ratio returns smoothly to 1:1 or can be maintained at the high ratio during low engine speed operation if accessory loading is high. The ability to maintain an efficient drive speed enables lighter, more compact ancillaries resulting in further efficiency improvements.

The Variable Ratio Crank Pulley also provides cost savings for vehicles that have an electric drive capability, Integral says. When the engine is off, the freewheel facility allows the ancillary drive belt to be powered by the motor, allowing belt-driven ancillaries such as hydraulic power steering, air conditioning and coolant pumps to continue to function in the normal way. This eliminates the need to specify electrically-driven ancillaries and provides the additional comfort and safety of continuous operation of these systems during engine-off operation.

Traditional systems also need a substantial electrical machine and inverter, with a battery or ultracapacitor system to provide a high current for fast starting in cold conditions.

The new B-ISG system allows the use of permanent magnet machines where previously the combination of high stall torque and high maximum speed has made this type of machine impractical for stop-start, Barker said. Integral Powertrain is developing a new high-efficiency permanent magnet motor specifically for this application.

With a diameter of 150mm and integrated low-cost, water cooled power electronics, the new machine can directly replace a standard alternator. As well as starting, the machine (rated at 5-10kW) will provide efficient regenerative braking and torque enhancement at a price that will make it affordable in volume sectors.



Great, an impressive advance in the technology of buggy whips.


If this could help cars get 20% better mileage and be affordable for millions of owners, I think it would save a significant amount of fuel.


Start/Stop is a "shovel ready" stimulus that should be mandatory on all new car.

Nick Lyons

It appears that this could make conversion of existing models to start/stop simple and inexpensive. I'd say this is a good idea--getting an immediate 5 - 15% fuel savings on a large fleet of new cars/trucks while more thorough (and expensive) solutions are in development.


We could make FFV and start/stop mandatory. The political will is not their for start/stop, but maybe FFV is, which would allow 10 million cars per year to run cellulose E85. If we could then supply most of those cars with cellulose E85, we could reach the goal of no imported oil from the middle east easily within 10 years.

We would need to leverage private investment with public investment because this is in the people's interest, tax dollars could be used. The investment would be paid back with the profits. No one ever said that the government could not run a profit and do the right things for the country at the same time. It might lower taxes and provide much more energy security.


If you want to get better mileage most effective component change you can do to your car is to moddify the nut that holds the wheel. The first thing that should be made mandatory is a minute by minute mpg gauge placed within the drivers line of sight. [A Scangauge cost ~$120 and works on any car build in the last 10 years.]

After that I'd have self-inflating tires put on every car- http://www.selfinflatingtire.com/ -


The right wing in the U.S. would call that "nannyism". The idea that the government knows best, even if the people don't. We can give incentives to install items like this one mentioned in the article. We can give incentives for buying an FFV or hybrid, but mileage meters would not fly.

Oregon had a plan to install GPS gadgets in cars to monitor how many miles driven by large vehicles, it did not meet with loud approval. Having to report annual odometer readings to the DMV might work, but even that would have resistance. Independence is a core value in the U.S. even if it means waste and inefficiency.


This looks to me like Antonov's 2 speed alternator/starter, plus an electric clutch. Reliability and price are an issue.
They say 5-10kW starter/generator with a belt drive. Currently all such systems in passenger cars that use belt, are rated up to 4 kW. A chain would probably be a better option, but chains need lubrication, which increases complexity and price.
No wonder that for electric motors above 5 kW, in hybrids, leading car makers (Honda, Toyota, Mercedes, Hyundai) use pancake motors as a direct drive.
Chevy Maliby used 5 HP belt system (BAS) and it's being dropped - apparently inferior by design.

self inflating systems have many military vehicles. Likely to be expensive. It also requires a compressor and extra hoses.
A simpler option is to rise fuel prices, people will learn quickly many tricks to save fuel. Proven many times everywhere.


You may have misunderstood what I meant. All I'm talking about is a trip computer. It doesn't report to the state it just gives the drive more information, like the dashboard on the Prius. A scangauge will connect to a vehicle's onboard computer, read the real-time information, and calculate and display the instantaneous fuel economy. This information assists the driver by displaying the fuel consumption. This provides a general indicator to the driver who can then infer in real-time how driving techniques affect gas mileage. This can help the astute driver to learn how to drive more efficiently faster.


"mandatory is a minute by minute mpg gauge placed within the drivers line of sight."

I understood what you said, the key word is mandatory, Americans don't like that much. If it costs them money and they don't need it or want it, they will not put up with someone forcing them to do it. The legislators that made them will be defeated in the next election. This is just the way the U.S. is IMO.


This VR (variable ratio) pulley might be robust, and not very expensive.
We can hope.
If so, it should provide lower cost, better performing mild hybrids.
The ability to drive accessories at two speeds provides added efficiency and driving the AC compressor while the engine is stopped seems consistent with a small battery pack and possibly a real advantage.
Since the VR pulley is on the crank, the ordinary serpentine belt should be adequate.

I think we should let the marketplace determine this value of this.
Making things mandatory implies they are not popular – except, of course, with those who want to make them mandatory.
It is obvious why we strive to preserve freedoms, not look to mandate.
This is just the way the U.S. is, and should stay.

“Driving green” is NOT as simple as some imply.
And I am not sure Scangauges would be much help.
Better mileage on the highway is simple – slow down, be late, spend an extra night in a motel.
Better mileage in the city is complex and a Scangauge is not much help.
In the city, the biggest gain is to avoid braking.
But a Scangauge shows great MPG while breaking.
“Avoiding braking” actually is more complex; it means plan ahead, coast instead of accelerate, lay back and let the light change and the traffic ahead clear. Then try to ignore the rage of the drivers behind you while you accelerate barely enough to make the light - "Hey, excess speed will just require braking".
I suspect that if 50% of the drivers did this and other were left to cope with them we would have synergistic chaos. I am not against driving green, I do it (reasonably), but it is oversold.
Slow acceleration from stop is also good for MPG, but early upshifts is the real goal and the Scangauge is not much help here either.


"self inflating systems have many military vehicles. Likely to be expensive. It also requires a compressor and extra hoses."

That's true for those systems, but the guys at the link I gave have hit on another way. It's simple and should be a lot cheaper.
Not only will it save gas but keeping your tires properly inflated could save lives so they'd be easier to justify making them mandatory - just like seatbelts. "Properly inflated tires increase car stability and reduce the danger of blowouts. They also ensure a car's proper braking distance."


The system looks safe, ai_vin but durability/life could be a problem.
But it also looks fail safe, so this might be OK.
A TPMS (tire pressure monitoring system) is still required, I believe, so there is also a backup.
Tire manufacturers oppose the present TPMS law, I believe, because typical settings are so low (to avoid nuisance warnings) as to be marginally dangerous, but auto makers seem to be OK with them.
A TPMS that takes load or tire deflection into consideration would be better - it could raise the limit when the SUV is loaded with kids.

Low oil pressure (LOP) lights also come on at very low pressure, yet seem to get the job done - so maybe we're OK.
In any event higher tire pressure improves safety, mileage, handling, tire life – a 4-win,
- but make the ride noisier, Oooo - :<(.

I don’t like "mandatory" but it’s probably justified for TPMS, and probably should be expanded to require minimum tire pressures to include max vehicle load PLUS 25% - then the TPMS could warn when AT min recommended pressure, not 25% below - where I think they are now.

Direct reading TPMS are fine, but most are not going pull up the numbers, they’ll wait for the warning, at 25% low :<(

Oh, and I still like the 2 speed pulley :<)

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