Re: New VW 122 PS TSI Engine In Detail
Wolfsburg, 29 May 2007
Effective actions taken to reduce fuel consumption and improve driving dynamics are direct gasoline injection, engine charging and reduction of engine displacement. Volkswagen is taking precisely this approach in its TSI engines: Reducing engine displacement, and thereby lowering friction and throttle adjustment losses, results in lower specific fuel consumption and a higher level of efficiency. Depending on the performance class, this is done either by a combination of turbocharger and supercharger, or simply with a specially developed turbocharger as on the new TSI.
The TSI – which is 90 kW strong over a wide range from 5,000 to 6,400 rpm and offers a very high specific torque of 144 Newton-meter per liter – delivers exceptionally agile response even from very low engine speeds without the addition of a supercharger. There is no turbo hole here. When it comes to forming the charge mixture, Volkswagen implements – and this is the case in its TDI engines as well as the TSI – a combination of engine charging and direct injection. Here too it is clearly evident that gasoline direct injection and engine charging complement one another ideally and together enable an unprecedented increase in efficiency.
The basic layout
The 1.4-liter TSI is an in-line 16V four-cylinder engine of the new EA111 engine generation with 1,390 cm3 displacement, cylinder spacing of 82 millimeters, a bore/stroke ratio of 76.5 to 75.6 millimeters, electronic gasoline direct injection, electronic-mapped ignition with cylinder-selective anti-knock control, turbocharger and intercooling. The TSI exhibits 10:1 compression, which is relatively high for a turbocharged engine and is fueled with more economical super (95 ROZ) fuel. A new generation of pumps ensures optimal buildup of high pressure in the injection system.
A primary focus in the development of the third TSI was to reduce friction losses even further. Advanced development of the combustion process and a redesign of the intake port made it possible to do without charge movement flaps in the intake port. Simultaneously, an absolute requirement set forth in the specification was that the car must be able to achieve a level of agility similar to that of the twincharged TSI engines. And that was not all that was required: The TSI also had to be able to serve as a mass-produced engine for model series ranging up to the Passat.
The 90-kW engine shares the following components with its two stronger brothers:
-Gray cast iron cylinder crankcase in open deck construction (ensures optimal cooling in the upper cylinder area).
-Timing case that integrates the oil filler, crankcase venting and oil filter module.
-Valves are driven by a robust and practical, hydraulically-tensioned toothed chain.
-Steel crankshaft.
-Connecting rod.
The hunt for every gram
The 140 PS and 170 PS TSI engines are already lightweight. Yet, standing still is really a step backwards. So consistent efforts were made to reduce the weight of the new TSI even more. Its pistons and valve reliefs were designed as lightweight castings, and the geometries of the asymmetrical stem and wall thicknesses were also optimized to handle their loads. That is how weight was trimmed gram for gram. On the cylinder head, whose fundamental concept is also based on the stronger TSIs, it was possible to reduce weight by about 600 grams with a structure-optimized design.
The Volkswagen engineers also reconfigured the intake port. Based on the large TSI, it was further developed with the goal of achieving a level of swirl or tumble that would not require charge movement flaps, as already mentioned. In addition, the new intake port was substantially modified. The advantage: Over broad sections of the engine’s operating range, it was possible to achieve quicker and even more efficient combustion with better fuel economy and a smoother engine characteristic.
Valves on the TSI are actuated by two camshafts – also further optimized – with inlet-side adjustment. Various modifications enabled weight savings here too: The camshafts each weigh 304 grams less. Every gram counts. That is why even the cylinder head cover is 150 grams lighter. Overall, the 90-kW TSI is 14,000 grams or 14 kilograms lighter than a TSI with 125 kW.
Turbocharger and intercooling
The turbochargers are compact and therefore weight-optimized in design too. In keeping with the overall concept, the best dynamics and lowest fuel consumption were top priorities. The very quickly responding turbocharger and very narrow intake and exhaust cams together with intake camshaft adjuster, are also responsible for making 80 percent of the 200 Newton-meter maximum torque available at a low 1,250 rpm. The refined flow optimization of the integral exhaust manifold and a very carefully optimized exhaust turbine also deliver excellent, low-loss engine charger operation, even at high speeds. The maximum speed of the turbocharger is 220,000 rpm.
Integrated directly in the charger’s compressor housing is the electrically-controlled divert-air valve. Its advantage compared to a pneumatic valve: Its construction is more compact and less complex. In addition, it produces significantly shorter switching response times, so that the turbocharger always operates optimally, even with abrupt throttle adjustments. An electrically-controlled divert-air valve was introduced for the first time on the turbo engine of the current Golf GTI.
An innovation on the new TSI is its water-flow intercooler, which is positioned right in the intake port. It is part of a low-temperature circulation loop that is independent of engine cooling. The advantage here: The charge air system exhibits a lower volume than in conventional approaches that utilize a front intercooler. Numerically speaking, it was possible to reduce the volume from about 11.0 to 4.8 liters. This significantly shortens the time required to reach a charge pressure of 1,700 millibar in the intake port. The results: Improved dynamics due to minimal delays in filling the combustion chamber to its maximum. And the driver of a Volkswagen equipped with the 122-PS TSI can experience this dynamic gain.
Modified injection technology
Electronic direct injection is marked by a newly developed high-pressure injection valve with six fuel spray holes. Background: A multi-hole high-pressure injection valve of this type was first used on the "large" TSI engines. However, on the "small" TSI the spray behavior was significantly modified. The fuel mixture is distributed more efficiently in the combustion chamber thanks to a new design of the six injection jets that are adapted to the specific needs of this engine. This enabled ignition timing adjustment, and one result of this was significantly lower HC emissions (hydrocarbons). The injector itself is arranged on the intake side between the intake port and the cylinder head gasket level; the maximum injection pressure is 110 bar.
