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Temperature Compensation Archives - Page 2 of 3 - STS Switzerland (EN)
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Pressure sensors in motorsport: Where a fraction of a horsepower is decisive

Pressure sensors in motorsport: Where a fraction of a horsepower is decisive

by | Wednesday, 1 July, 2020 | Automotive

“The winner takes it all!” The world of motor racing is divided into winners and losers, with the successful driver enjoying the champagne shower. The preliminary outcome, however, takes place on the engine development test bed, with high-performance pressure sensors representing the decisive competitive advantage.

STS supplies pressure sensors to customers from the world of motorsport, including participants in Formula 1 and NASCAR. Both of these racing series, despite all their differences, have one thing in common. Every horsepower counts and embodies the decisive advantage on the track. When every tenth of a horsepower is to be wrestled from extensive analysis on engine testbeds, the end results have to be absolutely reliable down to last decimal place.

Pressure measurement technology in Formula 1 engine development

The current engine regulations in Formula 1 were introduced in 2014. V-layout engines of six cylinders, 1.6 liters displacement and a single turbocharger are driven. The rev speeds reach up to 15,000 min−1. The Kinetic Energy Recovery System (KERS), an electrical system for recovering energy under braking first introduced in 2009, has now been replaced by the Energy Recovery System (ERS). In modern Formula 1, the engines involved are thus of a hybrid type. The future of Formula 1, for this reason, has long since become the present. The perhaps most successful racing series worldwide is also a testing laboratory for the road. From disc brakes to computer diagnostics, many technologies now found in everyday road traffic have their origins in the development centers of Formula 1.

The prevailing engine regulations, which evenly delineate the parameters for all teams, make thorough research on the testbed essential to carving out the decisive advantage. Every single horsepower counts. In comparison to tests for vehicles in normal road traffic, different requirements, to some extent, are applied. Oil and water pressures are higher, as are their arising temperatures. When improved fuel economy and increased performance is the aim, then extensive testing under racing conditions is essential. Furthermore, the precision of measured results across the required temperature range is of great significance. In Formula 1, major leaps in terms of horsepower are often not the case – improvements even in the decimal regions are a reason for celebration at this elevated performance level.

In light of these challenges, a well known racing team from Formula 1 approached STS, since the hitherto employed sensor technology failed to meet their high requirements. The measuring instruments used were too big and too heavy. Even more serious, however, was the problem that additional cooling technology had to be built into the testbed, since the sensor temperatures would otherwise rapidly escalate above the maximum. Measured results under this scenario would thus be worthless.

The aim of the developers was to acquire pressure sensors that permit standardization and make additional cooling elements obsolete. The topics of weight and size also play a role, since these factors influence the performance of the speeding car.

STS provided the racing team with a new sensor from the ATM series, available on the market from the fall of this year. This sensor scored not only in its desired precision across the required temperature range, but also delivered a further decisive advantage which could enduringly optimize engine development. With the previously used sensors from another manufacturer, there were malfunctions when switching to the hybrid systems employed since 2014. The results were that the testbed would shut itself down and longer term measurements were practically impossible. The ATM sensors from STS are fail-safe and thus allow for extensive testing on the road to the victory podium.

Pressure measurement technology in NASCAR engine development

Although hybrid engines are not built into NASCAR stock cars, extensive testing is still required to attain the optimum in performance. In this sport also, a well known engine manufacturer has opted for the pressure measurement technology from STS. During extensive tests, some 200 ATM.1ST pressure transmitters have been keeping an eye on oil, water, fuel and air pressures. From air pressures reaching the engine right through to improvements in oil flow, the aim is to precisely examine various factors to attain even the slightest increase in performance (involved here is ca. 900 PS). As with Formula 1, the highest of precision is required. The scope here amounts to just a tenth of a horsepower!

The manufacturer choice went to the ATM.1ST pressure transmitter, since it is largely unrivalled in its required performance characteristics.

  • The modularity of STS sensors also allows the manufacturer to connect a special pressure adapter.
  • A total error of ≤ ± 0.30 % FS permits meaningful analyses for improving engine performance.
  • Long-term stability considerably minimizes the need for calibration.
  • The pressure measuring range from 100 mbar…1,000 bar is well suited to those pressures arising during engine development.
  • Outstanding temperature compensation allows for precise results across a broad temperature range – a decisive criteria for the sharply rising temperatures during performance testing at these highest levels.

Whether in Formula 1 or NASCAR, the path to the victory podium leads through engine testbeds. In the high-performance motorsport field in particular, high-precision sensors are required for monitoring all of the important data from oil and water pressures to fuel and air pressures. Besides precision, fail-safe capability also plays an important role in being able to conduct essential long-term testing that yields reliable results.

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GDI engines come under pressure to reduce particulate emissions and improve performance

GDI engines come under pressure to reduce particulate emissions and improve performance

by | Wednesday, 1 July, 2020 | Automotive

With some 40 million gasoline direct-injection (GDI) engines expected to be sold by 2025, it may be surprising to learn that these units emit more hazardous fine particulate matter than a port fuel-injected engine (PFI), or even the latest heavy-duty diesels equipped with a particulate filter.

The potential increase in the market means that GDI particulate emissions, though low compared to those of an unfiltered diesel, are now coming under scrutiny from regulators and manufacturers alike.

To reduce these emissions and improve overall performance engineers are studying new combustion designs and engineering concepts, including increasing the fuel pressure, alternate fuels and exhaust emissions control.

According to Matti Maricq, technical leader in chemical engineering and emissions after treatment at Ford’s Research and Innovation Center in Dearborn, injecting fuel directly into the cylinder enables a clean-burning explosion that wastes little fuel and delivers greater power.

During this process gasoline is sprayed directly where the combustion chamber is the hottest (rather than in the air intake), allowing for a more thorough, even and leaner burn.

Cleaner burning GDIs emit harmful particulates.

But because of incomplete fuel volatilization, partially fuel-rich zones and the “wetting” of piston and cylinder surfaces, GDI engines produce unwanted particulate matter. Most emissions typically occur during cold start and high load transient conditions during the warm-up phase, but this can vary according to load, drive-cycle phase and driver demands.

While “green” critics remain sceptical about so-called “engine management” methods, believing them to be unreliable compared to exhaust filters, most OEMs and component suppliers expect that combustion design and engineering changes will prove more cost-efficient and eventually equally effective.

Current development indicates that higher fuel pressure, possibly touching on 40MPa,together with new ultra-precision injectors will greatly improve future GDI systems. To further optimise the system engineers will also continue to improve injector timing, targeting, metering and atomization.

In a recent study, published by the SAE, it was established that an increase in fuel system pressure improved the homogeneity of the mixture and reduced the tip diffusion flame thereby significantly reducing particulate emissions under homogenous combustion in a GDi engine.

Furthermore, as a result of the enhanced intake charge motion at fuel pressures of between 20 MPa to 40 MPa a further reduction of particulate emissions was achieved.

As indicated by the combustion data, an increase in fuel pressure has a significant impact on the reduction of combustion emissions as well as improving fuel consumption.

However for a GDi system to operate optimally it’s important that, during the design and testing phase the pressure of the fuel in the common rail (CR) is correctly measured so that the ECU can be mapped accordingly.

Measurement of CR fuel pressure is key to lower particulate emissions.

Direct injection pressure is measured with sensors, and the signals are used to determine pump speed and/or volume.

Most direct injection systems use piezo-resistive pressure sensors on the low side of the system. The silicone chip element generates a measurable electrical voltage when pressure is applied, increasing as pressure increases.

On the high-pressure side sensors usually use a metallic membrane on a resistance bridge. When pressure is applied, the bridge generates a change in resistance that results in a change in the applied voltage. The Electronic Control Module (ECM) transforms the voltage into a calculated pressure, generally to within a ±2% accuracy.

To maintain the correct pressure, the ECM pulses the low-pressure pump. The system typically has a regulator and no return lines. Some systems even have integrated temperature sensors in the lines that are used to calculate the density of the fuel so that the fuel trim can be tuned to the amount of energy in the fuel.

To ensure accurate measurement of the line pressure it’s important that high precision pressure transmitters are used to map the pressure within the CR under all engine and load conditions. Any errors in this process can result in incorrect modulation of CR pressure which in turn can result in serious abnormalities, such as cylinder wash which can occur if the CR mean pressure exceeds the injector design pressure when fuel delivery is increased at high loads.

Additionally, with the introduction of the harmonized driving cycle OEMs will be under renewed pressure to meet emissions targets set by regulators, and GDI spark ignition engines will be at the forefront of a new generation of green technologies. However, for this technology to meet upcoming legislation particulate emissions need to be reduced, largely through the accurate control of the CR fuel pressure.

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The turbocharger succumbs to the pressures of energy conservation

The turbocharger succumbs to the pressures of energy conservation

by | Wednesday, 1 July, 2020 | Automotive

For many years turbochargers were only found on expensive sports cars and diesel powered engines, but emissions regulations changed the way the world viewed forced induction. Although at the core was still the quest to improve performance, now manufacturers were looking at restoring performance and driveability to downsized fuel-sippingengines. So in the 21stCentury, almost everything from the little 999 cm3 Ford Ecoboost to the latest Ferrari’s all gained shiny new turbo technology.

But almost as soon as the tech came into its own it seems set to become redundant, upstaged by the new eCharger. Already Audi’s fitted this to the series production SQ7 and will be rolling out the technology to future production vehicles as 48 Volt electrification gains traction.

The key advantage to the electrically driven supercharger is that, as with turbochargers, there are no parasitic losses; but unlike most turbo’s there’s no turbo lag either and no need for a wastegate. The powerful electric motor can spool up the impeller to 70,000 rpm in less than a second, which eliminates turbo lag.

This naturally improves driveability and reduces consumption and emissions by between 7 and 20 percent when the device is used on a vehicle equipped with regenerative braking, which captures the car’s kinetic energy and turns it into electricity.

Pressure is key to unlocking the eCharger’s performance

Electronically controlled, the eCharger can be mapped to optimize engine performance while maximizing the energy recovered from the exhaust gas, but in order to achieve this Utopia, engineers need to create a map of the boost the engine requires by measuring manifold pressures at various engine loads and speeds. This can only be done with the aid of top quality pressure sensors.

As with any super/ turbo-charger, it’s important that the unit is matched to the engine’s requirements: Failing to do this, will either starve the engine or result in unnecessary electrical power consumption.

Being a maturing technology, not much research and testing data is available to engineers wishing to explore the boundaries of eCharge superchargers. Although fluid dynamics and electrical engineering can provide good foundations from which to build, it’s still vital that theories are validated under real-world test conditions.

In order to qualify the performance, once the baseline eCharger has been selected, the vehicle is equipped with extremely accurate pressure sensors that are readily calibrated and provide precise readings over a wide range of manifold boost pressures and temperatures. These sensors must also be resistant to vibration and chemical degradation.

Both on the engine dynamometer as well as road testing, throttle position/ engine speed/ Manifold air Pressure and temperatures are continuously recorded to ascertain the interrelationship of these key inputs.

From this information, engineers are able to verify that the correct eCharger configuration has been selected whilst at the same time ensuring that the closed loop engine management controls are able to correctly respond to the key variables.

The result of getting this right delivers a vehicle, such as the SQ7, which has stunning performance, drive ability and fuel consumption whilst still meeting future global emissions regulations.

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Accurate pressure measurement is critical to safe, cost-effective, motor vehicle development

Accurate pressure measurement is critical to safe, cost-effective, motor vehicle development

by | Wednesday, 1 July, 2020 | Automotive

The principle of hydraulic power to carry out work has been around since ancient Egyptian times, but as systems have evolved, so too have the tools required to design and develop these sophisticated, often critical circuits.

From the earliest manometer invented by Evangelista Torricelli in the 1600’s to the mechanical Bourdon gauge and finally today, the piezoresistive pressure transducer, developers have always sought the best equipment to measure pressures and optimize the design. And in recent times automotive engineers, in particular, have come to rely on these high-quality, accurate pressure sensors when carrying out vehicle testing and development.

These current pressure transducers are typically capable of recording full-scale deflections from about 350 mbar to 700 bar under sustained temperatures ranging from -40OC to 150°C; and best of all, quality sensors such as those produced by STS, are capable of a hysteresis and repeatability of typically around 0.001%!

Image 1: High precision pressure transmitter ATM.1ST with accuracy of up to 0.05% FS

High-quality pressure sensors are used in the development of key automotive systems.

This level of repeatability is critical in the design and development of cooling and fuel delivery systems, amongst others. During development, designers rely on stable pressure measuring equipment to accurately record information so that the effect of even the smallest of design changes can be documented without concerns that the sensor is incapable of repeatable results.

In a recent redesign of an engine cooling system to take advantage of the reduced parasitic losses made possible through electrification, the engineering team at a luxury OEM was initially faced with a pressure drop across the pump of around 250kPa. Before a redesign of the new electric pump was possible, accurate pressure measurements had to be recorded allowing engineers the opportunity to identify the problem. After studying the results logged by the array of pressure sensors the design was modified, reducing the drop to less than 100kPa and cutting the parasitic losses by 500W.

And although electrification and electronic controls are playing increasingly significant roles in vehicle systems, hydraulic pressure is still relied upon to guarantee smooth operation of many critical circuits.

By way of example, during the development of an automatic transmission, port line pressures have to be measured in real time and then compared to design norms to confirm that design parameters are being met. At the same time, shift times and quality are measured and subjectively evaluated to ensure drivability and performance meet customer requirements.

Notwithstanding the value of high-quality pressure sensors in recording valuable data during testing and development, in industrializing future technologies these tools can also significantly reduce design costs.

Pressure sensors make sure future technologies measure up to expectations.

In an attempt to improve the performance of severely downsized engines, manufacturers are taking advantage of the additional power 48V electrification offers, by replacing the turbocharger with an electrical supercharger.

Being a maturing technology, not much research and testing data are available to engineers wishing to optimize eCharge superchargers. Although fluid dynamics and electrical engineering provide a sound platform from which to build, it’s still vital that theories are validated under real-world test conditions.

To achieve this, manifold pressures must be mapped to optimize engine performance while maximizing the energy recovered from the exhaust gas. For this, extremely accurate pressure sensors that provide precise readings over a wide range of manifold boost pressures and temperatures are required. These sensors must also be resistant to vibration and chemical degradation.

And while manufacturers around the world continue to carry out research into electric vehicles, several groups are considering ways to harness hydrogen to generate electricity instead of relying on storage batteries.

Hydrogen fuel cells employing proton exchange membranes, also known as polymer electrolyte membrane (PEM) fuel cells (PEMFC), have already seen limited series production in vehicles such as Toyota’s Mirai.

Although small PEM fuel cells commonly operate at normal air pressure, higher powered fuel cells, of 10kW or more, usually run at elevated pressures. As with conventional Internal Combustion Engines, the purpose of increasing the pressure in a fuel stack is to increase the specific power by extracting more power out of the same size cell.

Typically the PEM fuel cell operates at pressures ranging from near atmospheric to about 3Bar, and at temperatures between 50 and 90°C. While higher power densities made possible by increasing the operating pressure, the net system efficiency may be lower due to the power needed to compress the air; hence the importance of balancing the pressure to the requirements of the particular fuel cell.

As with ICE boost pressures, this can only be done by taking accurate pressure measurements using high-quality pressure sensors. These measurements are then compared to the fuel stack outputs to minimize the parasitic losses while optimizing the gains in electrical output.

So, irrespective of the course the automotive industry chooses for future technologies, accurate pressure sensors will remain key to the development of safe and efficient vehicles.

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Manufacturers are feeling the pressure

Manufacturers are feeling the pressure

by | Wednesday, 1 July, 2020 | Automotive

With emissions regulations set to ratchet up a notch in China, Europe and North America, manufacturers are hard-pressed to optimize every engine component and function to cost effectively meet the new demands.

Although engines that are under development have always been tested to ensure they meet the most stringent quality requirements in terms of materials, emissions and efficiency, there’s a renewed focus on detailed development to unlock performance that may have previously been overlooked.

In order to do this, every time an engine is run on a test bench all the variables influencing emissions and performance have to be monitored and measured to understand their individual performance as well as how they function as part of the overall system.

This requires highly dependable, precise measuring equipment that delivers accurate readings under the extreme conditions encountered in and around the engine. Sensors of this quality and accuracy are manufactured by only a handful of suppliers around the world, which are standing out for the ability to customize quality pressure sensors to the customer’s requirements.

Pressure sensors are key to eliminating inefficiencies

STS have developed pressure sensors that meet OEM, first tier and specialist engine designers’ requirements in engine development. Using these sensors customers carry out development and design work that focuses primarily on reducing exhaust emissions and achieving a high power density, low fuel consumption, long service life and maximum reliability.

Because an engine’s efficiency depends largely on airflow and charge density into the combustion chamber and how the exhaust gases are either used to enhance the engine’s torque, by way of a turbocharger, or are able to be discharged efficiently, accurately mapping key pressure regions is critical. These pressures are often of the order of millibars, requiring extremely accurate and highly dynamic measurement.

Furthermore to obtain a reliable analysis of pressure distribution within the inlet manifold, it is important to take inlet pressure measurements as close as possible to each inlet valve. This is to accommodate the varying geometry of the manifold which often results in each cylinder being supplied with a different amount of air, which negatively impacts both performance and emissions.

When determining the performance of the exhaust system, pressure measurement becomes quite complex, as not only does the performance of the exhaust rely on pressure but also the interaction of the exhaust-gas pulses due to the engine’s firing order. STS pressure sensors are capable of measuring these processes on both the inlet and outlet sides with a high level of accuracy.

Robust sensors must remain accurate in a hostile environment

In the test environment the sensors must be resistant to the chemicals and oils associated with engines, and be able to accurately measure pressures in extreme temperatures. Moreover, the sensors need to operate reliably and not be affected by vibration or voltage fluctuations.

STS’ range of sensors also allows customers to take measurements in critical systems such as oil, fuel and water pumps, injector lines, intercoolers, and heat exchangers. All of which are vital in optimizing engine efficiency.

So although customers and regulators are increasing the demands for cleaner and better performing engines, OEMs and suppliers are well equipped to stretch the envelope and even exceed expectations.

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