Green Car Congress: Inside VWs New Twincharger TSI Engine

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Inside VW’s New “Twincharger” TSI Engine

31 August 2005

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 FSI	Golf GT 1.4 TSI	TSI %
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.

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.

August 31, 2005 in Engines, Europe, Fuel Efficiency, Vehicle Systems | Permalink | Comments (28) | TrackBack (1)

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Comments

This is one complex system for such negligible gains. I was expecting more. Seeing the improvements in economy is just disappointing. This engine has a performance orientation rather than an economy. Just simply turbocharging the 1.4 FSi engine like they did the 2.0 TFSi would provide similar performance to the 2.0 with reduced consumption without the cost complexity and weight gain from swicthing to an iron block to support supercharger pressures. I am guessing this engine would be even more expensive than a 2.0L diesel.

The automotive industry is so blind that they have to show increase in performance acompanied by fuel economy improvements to prove a point. If this engine was geared towards just increasing the fuel economy of the 2.0 FSi, the gains would have been far greater.

Posted by: Tman | Sep 1, 2005 10:31:13 AM

This engine configuration isn't new in the automobile industry, allthough it's previous use of a combined volumetric compressor with a turbo charger was in the middle 80's supercar Lancia Delta S4, and only about 200 of them were built to comply with FIA's group B homologation rules.

Obviously, at the time, power and torque under all ranges were the main goal, being this the model that Lancia took on the world rally scene.
In VW's case, while some fuel improvements are achieved, the real gains are in power and torque. This kind of technologie makes sense in some european markets like mine (Portugal) were taxes over new cars are calculatted on a displacement basis, but in other countries, the extra complexity of this system may prove itself a little bit to much for the ordinary driver.

Posted by: Pedro Amaral | Sep 7, 2005 6:54:36 AM

Guys.... the timing and boost is entirely set by software. Do you really think that it will come out with all that performance given the current state of fuel costs - or do you think maybe VW has something up their corporate sleeve that they aren't sharing yet?

Think Think THINK

They realize that they don't need all that power. What if they backed it down to current performance levels????

Ol Vdub Guy

Posted by: aL e. | Sep 17, 2005 5:45:04 PM

It would be nice to hear if this car can be run on E85. Even better if can take advantage of E85 octane rating by turning up the boast, ie. Saab Biopower

Posted by: Tom | Oct 24, 2005 1:23:03 PM

For the last few years now, almost every diesel car sold in Euope has had a turbo (the only exception I can think of, ironically, is the VW SDI), and I've been wondering why on earth turbos haven't appeared on small petrol engines too.

170 hp from a 1.4 makes people sit up and take notice, but drivers looking for sheer horsepower will now be wondering what a 2.0 would be capable of.

What will make a difference to many buyers is the implications for smaller engines:
a 1.0 with around 90 hp and 50+ mpg ?
a 1.2 with 100-110hp and close to 50mpg.

Engines like this could convince me to switch away from diesels, but then I wonder what a 1.4TDI would be like with a twin turbo?

Posted by: Nick | Nov 1, 2005 3:49:50 AM

Some may say that the gains are disappointing, but in some parts of the world, Trinidad for example, the government taxes the car partially based on the size engine it has. There would be a significant price difference between a 1.4 and a 2.3 naturally aspirated(which this engine is being compared with).

Posted by: Kevin | Nov 6, 2005 10:24:47 AM

Hello, I am french and I do a school work... I ask you if you can explain me just in two or three lines the ecologic interest of the TSI technology... Thanks for your answer... Best regards...

Posted by: rouland | Nov 23, 2005 12:44:25 AM

31 Dec 2005

Has anyone attempted to convert VW's Twincharged 1.4 TSI engine to LPG gas?
What were the results?

Seems to me like the perfect combination
to improve fuel economy and reduce engine wear.

leon akselrad

Posted by: leon akselrad | Dec 31, 2005 10:59:52 AM

31 Dec 2005

Has anyone attempted to convert VW's Twincharged 1.4 TSI engine to LPG gas?
What were the results?

Seems to me like the perfect combination
to improve fuel economy while reducing
engine wear and emissions.

leon akselrad

Posted by: leon akselrad | Dec 31, 2005 11:10:11 AM

In it's most basic form what you have is a 1.4 liter engine pumping out almost 170 hp and getting 32 mpg. These numbers are better than the optional 2.0 liter engine in every respect, but all I hear is complaining. It's too complex? What? With variable valve timing, cylinder shut down and every conceivable aspect of an engine being controlled by computers these days and this engine is too complex. Get real. I say bring it on. I'll take 170 hp from a 1.4 liter any day. Thank you VW.

Posted by: Russell | Jan 18, 2006 12:05:12 PM

What is TSi?? I bought a vehicle from a guy. He told me that the engine is TSi. I would like to have soeone to explane TSi to me
Thank you

Posted by: Doumbia | May 17, 2006 12:06:14 PM

Doumbia,

There is no consistency in car acronyms. They are entirely arbitrary and mostly selected by marketing people to help sell the car. Your TSi probably has nothing to do with this TSi.

Posted by: shaun | May 22, 2006 2:28:09 AM

This system is NOT that complex!! For the person who made the comment above... the average driver will not even notice that the turbo charger and supercharger are collaboratively working. This is NOT too complex for consumers, how can I make this clearer, the average driver does not care that the engine is smaller. Drivers will only notice the slight increase in power over the standard fsi engines and will also notice the comparative fuel savings. The car industry is a place where small gains are the order of the day, there has been no true revolution in engine design and its economy resulted in resent years. The TSI engine is a perfect example of vw thinking outside the "box".
With many people looking to hybrid cars as the answer for environmental benefits it is obvious to see that car manufacturers are stimulated to build higher efficiency cars which perform well. Hybrids are not the answer for the future of automobiles, they pollute way too much, mostly in its afterlife when all the electronics and gigantic battery systems have to decompose. VW among other companies realizes this and is striving for more economic fuel consumption gains in creative ways. I personally am very impressed with vw and am hoping this technology will make it to the USA as soon as possible.

Posted by: Peter | Jun 20, 2006 8:10:37 AM

I'm very impressed with the engine design on the TSI, although I can't help but think; why would you buy the TSI when the latest TDI is also 170PS output with a fuel return 10MPG better? I would imagine the emissions are fairly similar also, or is this the reason for the TSI?? (ultra low emissions)

Posted by: Gregg | Jul 17, 2006 3:07:54 PM

Gregg, personally petrol engines are a lot more fun to drive than diesel engines, so I would love to see the new TSI engine make it into a VW Polo!

Posted by: Eric | Aug 4, 2006 3:24:35 PM

Coming from a country where the tax for the same cubic centimeter engine is 500% higher for diesel than it is for petrol, i'd say i'm very much interested. The only way diesel can win the fight in my country (Malaysia) is if the fuel savings can actually counter the extra road tax for diesel. Besides, there's too much sulphur content in malaysian diesel, it'll wreck the engine in the long run.

Posted by: ammar | Aug 7, 2006 12:53:11 AM

This seems to be an over-complicated way to do it - this way would be much better, simplistic but clever design! ;o)

have a look here:- http://www.integralp.com/SuperGenArticles.aspx

Posted by: Jim | Aug 16, 2006 7:49:10 AM

I want to know about dual charger engine information,like thermal efficiency,output,machanical efficiency,strength and so on.

Posted by: Tsou Jih Yen | Oct 29, 2006 6:51:48 AM

for the guy that bitched about the iron block, 99% of vw's blocks are iron. Always has been that way.

Posted by: kris | Dec 26, 2006 12:40:25 PM

The TSI technology seems very impressing and tempting. The only thing that worries me is durability. I know bigger engines last longer and am wondering how much less will this 1,4 litre engine last than let's say the normal 2,0 litre engine? I surely don't want an engine break at 100 000 kilometres.

Thanks for your answers.

Posted by: Allu | Jan 14, 2007 4:18:52 AM

I wonder if Twincharger is made of; Combining Supercharger and Turbocharger by cuoplong them with RACHET gear transmision. It is like a bicycle, in low RPM, power is get from pedal (SC). But when riding down hill, when wheel is faster, the pedal can be free. So asume wheel is a TC, it powered wihout drag from SC anymore to the engine. Is it going to work?

Posted by: herbid | Apr 4, 2007 11:17:28 PM

Posted by: yovitadiah | Apr 8, 2007 8:45:14 PM

I'm planning to implement the "twin turbo" technology into my 2002 A6 2.5 TDI. Is anyone can suggest a suitable supercharger? I'm thinking about an Eaton / GM M62.

Posted by: Balazs | May 24, 2007 2:26:23 AM

32.7 MPG seems like disappointment, but that's way better than the cars they 've been importing into the USA. My 96 Jetta 2.0 gets better fuel economy than VW's current crop of USA cars. In the US the base model Golf comes with a 2.5L 5cyl. Only 22MPG!!!

Simply Horrible.

I'm not impressed with the Twincharger. Too costly and complex to implement accoss the board. This is little more than a hyped PR stunt. What happened to the "People's Car"?

I challange VW to reverse it's downward trend in efficiency before 2010.

Posted by: Nomad | Jun 15, 2007 10:58:16 PM

I'have a Touran with 1.4 TSi 140 bhp. With DSG gearbox.
it's magnificant!
No question about durability.
It's all tested thourably. Running life will be exeeding 250.000 km.

John

Posted by: John Judd | Oct 4, 2007 12:06:27 PM

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.

Posted by: brent | Nov 14, 2007 10:04:01 AM

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

Posted by: GTI or Die | Jan 9, 2008 10:57:36 AM

When does the TSI engine work without supercharging

Posted by: raymond | May 6, 2008 6:24:56 AM