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Inside VW’s New “Twincharger” TSI Engine

Tsi_exploded
The TSI Twincharging systems

VW’s goal for its new dual-charged (“Twincharger” in VW marketing-parlance) engine (earlier post) was to combine the low-end power boost provided by a mechanically-driven compressor (supercharging) with the higher-end increase provided by an exhaust turbocharger (turbocharging) to enable the downsizing of the engine for a given application while maintaining the driving experience for consumers.

Put another way, downsizing delivers comparable (or better) performance with lowered fuel consumption and emissions.

The first instance of this new Twincharged TSI engine family is a 90-kW (121-hp) 1.4-liter model that delivers a torque corresponding to a 2.3-liter engine, but with 20% less fuel consumption. Compared to the 2.0-liter FSI engine in the Golf, the power and torque gains are clear, although the decrease in fuel consumption is more modest. (See chart below.)

FSI vs. TSI
Golf GT 2.0 FSIGolf GT 1.4 TSITSI %
Displacement 1,984 cc 1,390 cc -30%
Cylinders 4 4
Compression 11.5:1 10:1
Boost Pressure 2.5 bar
Power 110 kW (148 hp) 125 kW (168 hp) +14%
Torque 200 Nm 240 Nm +20%
0–100 km/h 8.8 s 7.9 s -10%
Maximum speed 209 km/h (130 mph) 220 km/h (136 mph) +5%
Fuel consumption 7.6 l/100km 7.2 l/100km -5%
Fuel economy 31 mpg US 32.7 mpg US +5%
CO2 182 g/km 173 g/km -5%

Super-and turbo-charging systems are designed to force more air into the cylinder, thereby enabling more combustion and delivering more power—but also consuming more fuel than a comparable naturally-aspirated engine. However, the increase in fuel consumption of a charged engine is more than offset by the overall decrease in fuel consumption resulting from using a smaller engine.

For example, the 1.4-liter TSI is 39% smaller than the 2.3-liter FSI, but consumes 20% less fuel. As long as a downsized TSI is used to replace a larger FSI, there is a net gain in efficiency.

As a starting point for developing the Twincharged family, VW selected the direct-injection FSI from its EA 111 engine series as used in the Golf.

The basic FSI 1.4-liter engine (1,390 cc) is a 66-kW (88-hp), four-valve, four-cylinder engine. Note that the Twincharger 1.4-liter TSI offers 36% more power than its FSI cousin of the same displacement: 90 kW vs 66 kW.

To support the twincharging concept, VW engineers had to deliver a new, highly-resilient gray cast-iron cylinder crankcase to withstand the higher pressures, a coolant pump with an integrated magnetic clutch and supercharging technology.

VW also modified the injection system, introducing its first multiple-hole, high-pressure injection valve with six fuel outlet elements.

The injector, like that in the naturally-aspirated (non-charged) FSI engines, is arranged on the intake side between the intake port and cylinder head seal level.

To support the wider variability in the quantity of fuel needed across the range of operation (from idling speed to the 90-kW peak power output) to optimize the twincharging, VW increased the maximum injection pressure to 150 bar.

For the compressor, Volkswagen engineers chose a Roots-type supercharger (also known as a “blower”). Unlike some other types of supercharger, a Roots supercharger doesn’t actually compress air within the device. With two counter-rotating lobes, it moves a fixed volume of air per rotation (“fixed displacement”). Compression occurs in the intake manifold.

Roots superchargers can deliver a large amount of boost even at low engine speed. The main disadvantage is that they create a lot of heat.

Tsi_airflow
Air flow through the VW Twincharged TSI. Click to enlarge.

The compressor and the turbocharger are connected in series. A control valve ensures that the fresh air required for a given operating state can get through either to the exhaust turbocharger or the compressor.

The control valve is open when the exhaust turbocharger is operating alone. In this case, the air follows the normal path as in conventional turbo engines, via the front charge-air cooler and the throttle valve into the induction manifold.

The compressor is operated by a magnetic clutch integrated in a module inside the water pump. Under turbocharging conditions, the clutch disengages the compressor.

The maximum boost pressure of the Twincharger is approximately 2.5 bar at 1,500 rpm, with the exhaust turbocharger and the mechanical supercharger being operated with about the same pressure ratio (approx. 1.53). The compressor alone delivers a boost pressure of 1.8 bar even just above idling speed.

A conventional exhaust turbocharged engine without compressor assistance would achieve only a pressure ratio of about 1.3 bar.

The more rapid response of the turbocharger enables the compressor to be depressurized earlier by continuous opening of the bypass valve. Compressor operation is restricted to a narrow engine map area with predominantly low pressure ratios and, therefore, low power consumption.

In practice, this means the compressor is only required for generating the required boost pressure in the engine speed range up to 2,400 rpm. The exhaust turbocharger is designed for optimum efficiency in the upper power range and provides adequate boost pressure even in the medium speed range.

For acceleration, an automatic boost pressure control decides if the compressor needs to be switched on to deliver the tractive power required, or if the turbocharger alone can handle the situation.

The compressor is switched on again if the speed drops to the lower range and then power is demanded again. The turbocharger alone delivers adequate boost pressure above 3,500 rpm.

Comments

brent

To the guy who said consumers don't care about complexity:

Complexity == $$$$$$$$$$

increasing complexity in a machine increases initial cost, maintenance cost, repair cost, and repair time. If you don't care about any of those things, then you probably have too much time and money, and shouldn't worry about VW's economy segment.

GTI or Die

Doods and Bros, wake up. This tech has been around a long time, especially on deisels. Superchargers are parasitic eating tiny amounts of power but power none the less. Most deisels require boost to operate. Although this is a gasoline engine there are so many advantages of being blown and boosted. Fuel is one. I guarantee the power band on this new engine is going to be tremendous. Peak HP from idle to redline. Superchargers charge period you get your boost at idle through the efficiency range of the blower once the turbo spools the blower disengages "aka no more parasitic drag" = smaller more effiecient turbo. Both units will outlast other turbos and blowers that are not coupled. Simply by design they will require less maintence the workload is shared, they wont work as hard for equal output on a single turbocharged or supercharged engine. Since youre boosting early you have more breathability more flow of gases not volumetric but pressure,= faster turbo spool. No Lag!! you push the gas and the car goes. In reality youre only adding three additional components so you guys bitchin about complexity go cry yourself to sleep. Super charger, magnetic clutch, and a valve big woop. When you think about the fact that your turbo no longer has to do the work on it's own youre talking greater life expectancy. Awesome job VW keep it going... oh and it my country.. USA its all about ponies, in the end the guy with the biggest output with the smallest engine smiles longer especially when you roll up on a civic Si that some douche thinks is untouchable, you look at him he says Vtec.. they put vtec on the side of the car, volkswagen puts their initials on the back for a reason, that's where the guys gonna be when the light turns green otherwise he'd never know what beat him.
Peace

raymond

When does the TSI engine work without supercharging

Sebastian

One question, I got my GTI MKV 2009 w/TSI engine, but the tech spec sheet says 2.0L T, so is a 1.4L TSI or 2.0L TSI? thanks!

onward

Last time I checked with VW sales here in Hong Kong. The The Mk5 GTI is still a 2.0 FSI with Turbo producing about 200 horsepower.

I just placed my order for a 1.4 TSI 170bhp Golf GT a couple of weeks ago. When I testdrove it, it has similar performance as my old 2.6 V6 Audi which I am retiring with the Golf. So as far as I am concerned, it was an easy decision. Here, the difference between 14.l and 2.6l is actually a two-class difference in licencing, to the $$$ also made sense.

Personally, I think VW got it right with the TSI. The technology is not brand new, but the application of it is innovative. Given my driving pattern (few passengers, up and down hill over 50% of the time), getting the torque at low revs made all the difference. Within my family, we have a Toyota 2.0L, a Mazda 1.5L, and the Audi 2.6L. The Audi has better driving performance and better fuel consumption than the Toyota 2.0L, DESPITE both claiming a mere 150bhp. I've put the difference down to the torque. The Audi gives me max torque at 2250rpm, but the Toyota needs 3000+ rpm for the same torque, and guess what, it changes gear at a little over 3000rpm.

Few of us will ever take our cars to 5000+rpm for any length of time, so lower rev performance is more the deciding factor for us city folks.

Anyway. VW, Well Done! with the TSI.

Just one extra comment. I reckon the Golf GT 1.4 TSI with 170 bhp (VW also sells a 140bhp model with the same 1.4 TSI engine - it's all in the tuning I think) is the most expensive 1.4L here in Hong Kong at something close to double of some Japanese models; but for a European designed (not built) 170bhp, it is quite competitive.

Warren2

To all Oke that's VW

But What about the Antonov dualspeed supercharger

See this site and the results (see pictures) at the links.

Give your oppinion please.

http://www.antonov-clubsite.nl/000000962f000d411/00000098800138a0e/0000009880013d910/d006.html

http://www.antonov-clubsite.nl/000000962f0009a09/000000962f000c30f/index.html

Dan M

I've got Toyota Corolla 04 VVTi and the VW Jetta 08 TSI. Both 1.4 Engines, both petrol manual. What can I say? VW slightly economical-about 2 MPG more. However, I love the power. It's fast, etc.

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APT TURBO

Cool idea, one beneficial thing about turbo is that it can significantly boost an engine’s horsepower without significantly increasing its weight. With turbocharger, it is possible for smaller engines to behave like bigger engines with the introduction of more air into the engines.

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