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Technical Overview

STT Emtec Develops Diesel and Petrol Engines One Step Further

STT Emtec´s Products Generates Increased Driving Pleasure
Driving pleasure is generated by the interaction between the driver and the car. The engine, brakes, suspension, chassis, tyres and steering all play a decisive role. STT Emtec´s primary task is to continue the development of engines in order to offer you the greatest driving experience. The improvements we make result in safer overtaking, better characteristics when towing a trailer and, in some cases, even improved fuel economy.

Our work in engine development both complies with and complements up and coming EU environmental regulations.

A modern combustion engine is, despite a vast amount of development work, based on a variety of compromises in a number of respects. A few examples:

  • Fuel quality varies from market to market.
  • Minimized production costs lead to minimal sizing of peripheral systems, e.g. the exhaust system.
At STT Emtec we take engine system development \"one step further\". Through carefully balanced modifications we improve the engine\'s built-in potential thereby improving engine characteristics.

When optimizing a petrol or diesel engine an analysis of the entire engine installation is undertaken for each vehicle. This analysis involves, for example, the intake, exhaust, electrical and cooling systems as well as the transmission. Areas of improvement are identified and new components are designed and manufactured.

The performance is optimized without jeopardizing engine durability and service life. Performance does not simply refer to maximum engine output, as the vehicle\'s operating characteristics under different conditions are also just as important as its performance properties. Acceleration during overtaking, fuel consumption and towing load are three examples of characteristics where further refinement is often possible.

Extensive testing is conducted, first in an engine test cell where performance and emissions are measured and documented. Thereafter test vehicles are built and tested in extreme heat, Arctic cold, at high altitude and with heavy trailers. Once the system has been fully developed it is then certified in accordance with the applicable regional standards, e.g. TÜV.

Examples where carefully balanced modifications improves the engine characteristics

Turbo Compressor Optimization
Increased boost pressure and greater fuel quantity would appear to be the simple way to increase the output of a turbo engine. However, success depends on understanding a number of subsystems. One example is the various characteristics of the turbo compressor. The diagram shows three different compressor curves (blue lines).

The difficulty lies in raising P2 (boost pressure = pressure at the compressor outlet) without sacrificing efficiency or exceeding limits that can result in damage to the compressor. At the same time, the ratio P2/P1 is to be as low as possible to minimize air heating. Therefore, it is often necessary to modify the inlet system to achieve an acceptable balance in the system.

Sound knowledge and extensive measurements are therefore a prerequisite for achieving the optimal turbo compressor operating conditions.

Similar demands exist on the turbine side (exhaust side). The turbine is optimized for peak output by, for example, installing a custom exhaust system. 

Gas Flow Optimization
The diagram illustrates the variation in compression during the four power strokes. Improving the inlet and exhaust systems reduces pump- and scavenging losses which results directly in increased efficiency (marked in grey).

The rise in efficiency can either be applied to cut fuel consumption with unchanged output or to increase output with unchanged fuel consumption.

A consequence of improved output is an increase in the cylinder peak pressure (Pmax) and consequently an increase in the load on the engine. The improved input and exhaust systems mean however that the percentage increase in cylinder peak pressure is lower than the percentage increase in output and this naturally spares the engine.

Typical values: Output increase = 20% results in an increase in a 15% increase in cylinder peak pressure.

STT Emtec´s Products Deliver Performance without Jeopardizing Engine Durability and Services

Long term reliability is preserved by making the full power increase available only when certain conditions are met. Specifically, extra power is being decreased according to the following strategy:

  • At increased coolant temperature levels fuel amount, ignition timing and boost pressure are continuously adjusted until the temperature stabilizes or drops below a predefined value again.
  • Short term over boost during acceleration is dynamically limited by a reduction in fuel delivery.
  • In the event of a prolonged over boost condition the system enters a fail safe mode where only standard power is available.
  • At high altitudes the system enters a fail safe mode to prevent turbocharger over speeding.
  • At excessive charge air temperatures the system enters a fail safe mode.
  • In the event of a sensor failure extra power is not available.
  • To avoid the engine from overheating during extreme conditions, fuel amount and boost pressure can be adjusted below the standard values to maintain a safe coolant temperature. For example: driving in sand with heavy load at low speed with an automatic geared vehicle.

© STT Emtec AB, Box 100, SE-851 02 Sundsvall, Sweden    Phone +46 60 64 10 40   info@sttemtec.com

Visiting address: Kontorsvägen 9, Sundsvall, Sweden. STT Emtec, engine and emission technology.