VW's Twincharger System Overview

Thought I'd just put this together for anyone looking into twin-charging. It's based on the newer 136kw/182hp engine found in vehicles like the Audi A1.

This engine is a combination of a roots type blower couple with exhaust gas driven turbocharger ensuring a quick throttle response and power at all engine speeds.

The roots blower on this engine cuts in at approx. 1500rpm and in most situations cuts back out again at 2400rpms and is quite a large size for high efficiency.
At the latest 3500rpm the turbocharger then takes over with sufficient exhaust gases being sent through the manifold. This set up enables a higher compression ratio of 10.0:1 for increased efficiency and better fuel consumption.

THE TWINCHARGER SYSTEM:
Fresh air is drawn in through the air filter. The position of the control flap determines whether or not the air is drawn in through the supercharger and/or directly to the turbocharger. The air from the turbocharger then flows through a charge air cooler and throttle valve control unit and into the inlet maniold.

OPERATING RANGES:
This diagramme shows the operational ranges of the roots type supercharger, turbocharger and cross over points incorporating the two. Depending on torque requirements, the ECU decides whether, and if so how the required charge pressure is to be produced.
The turbo operates throughout the green range and note how the turbocharger alone cannot produce the desired charge at low engine speeds. The supercharger operates in the lower area (dark grey) and a combination thereof in-between.


DARK GREY: Continuous charging via roots blower activated from the minimum torque range (approx 1500rpm) to change over point at 2500rpm.Pressure is regulated from the control flap unit.
LIGHT GREY: The supercharger is activated in response to demand up to a maximum speed of 3500rpm. This is needed, as an example; if the vehicle is driven at a constant speed and then a sudden burst of acceleration is added via throttle input. This also overcomes the lag associated via low inertia at low exhaust gas speeds with solely turbochargers.
GREEN: The exhaust gas is now up to speed and flow so the supercharger is disengaged and the turbo takes over. Charge presure is regulated by charge pressure limitation solenoid valve N75.

 

IMPLEMENTATION OF OPERATING RANGES:
The engine load and speed range allows the ECU to determine how the air flows into the cylinders for the desired torque. The ECU also decides whether or not the turbo alone can generate what is required or the supercharger is needed.


NATURALLY ASPIRATED OPERATION AT LOW ENGINE LOAD:
In NA mode the control flap is fully open and flows directly to the turbo. Although the turbo is driven by exhaust gas the energy of the exhaust gas is so low that only a small charge pressure is produced. The throttle valve is opened in accordance with the drivers input and a vacuum is produced inside the inlet manifold.


SUPERCHARGER AND TURBO OPERATION AT HIGH ENGINE LOAD AND SPEEDS UP TO 2400RPM
During this period the control flap is closed or partially open to regulate the charge pressure. The supercharger is operated by a solenoid coupling and driven by the superchargers belt drive. The supercharger induces the air and compresses it before pumping it to the turbocharger. The air is then compressed further within the turbocharger. The charge pressure of the supercharger is measured by the inlet manifold pressure sender G583 and regulated by the control flap unit J808. The total charge pressure is measured by charge pressure sender G31. The throttle valve fully open an absolute charge pressure of 2.5bar is present in the inlet manifold.


As it approches 3500rpm for the change-over


EXHAUST GAS TURBOCHARGER OPERATION:
Above approximately 3500rpm the turbo alone can produce the required gas pressure at any point. The control flap is fully open and the air is induced directly to the turbocharger and the turbo can produce enough energy required for the charge pressure. The throttle valve is fully open and an absolute pressure of 2.0 bar can be found in the inlet manifold. Charge pressure sender G31 measures the charge pressure and is regulated via the N75 valve.



ROOTS TYPE SUPERCHARGER
Advantages: Quick charge pressure build up, high torque at low engine speeds, no external oil and lubrication necessary, activated on demand only.
Disadvantages: Consumes engine power due to pulley system, charge pressure is generated depending on engine speed and then regulated, with the result that some of the energy is again then lost.
EXHAUST GAS TURBOCHARGER
Advantages: Very high efficiency through the use of exhaust gas energy.
Disadvantages: In a small engine like the 1.4 the charge pressure generated at low engine speeds may not be enough to produce a decent amount of torque. High thermal load.

EDIT: My bad, left a pic out, sorted now

 

DRIVE SYSTEM:
The supercharger is activated when required and driven via the coolant pump via an auxiliary drive. This drive is activated by a maintenance free solenoid coupling on the coolant pump module. If the solenoid coupling is deactivated, three lead springs pull the friction plate back into its initial position and due to the high forces involved clicking is normal. Due to the ratios from thecrankshaft pulley to the roots supercharger pulley, as well as the internal ratio of the supercharger, the supercharger rotates at five times the crank speed. Maximum speed of the supercharger is 17500rpm.





SOLENOID COUPLING:
In addition to supplying coolant, the coolant pump has an integrated solenoid coupling for activating the supercharger. The coolant pump, alternator and AC air compressor are driven by the six groove main pulley. The five groove poly V belt of the secondary pulley drives the air compressor of the coolant pump.

The compressor solenoid coupling N421 establishes a frictional connection with the supercharger drive. The pulley of the coolant pump is bolted to the drive shaft of the coolant pump. The pulley for driving the supercharger rotates on the ball bearings. The solenoid coil is firmly connected to the coolant pump housing.


COMPRESSOR SOLENOID COUPLING NOT ACTUATED
The electrical circuit of the coil is not closed, as a result, a frictional connection is not established (X) due to the spring force between the friction plate and the friction lining. The stationary pulley runs freely on the ball bearings.


COMPRESSOR SOLENOID COUPLING ACTUATED:
The electrical circuit of the solenoid coupling is closed by the ECU. The magnetic force pulls the friction plate against the coupling lining. The coolant pump pulley is now frictionally connected to the supercharger pulley.




Hopefully this gives a better understanding of the system to some

 

Very informative, great write up. Looks like a clever system but lots of expensive bits to go wrong would scare me away.

 

Great.. But i agree when these things are out of warrenty going to be some big probs and big bills

 

Awesome reference info - thanks for posting it up.


Now we don't have an excuse for not doing a home brew version with a mini-charger and a GT2554R on all our own cars....

 

I think you mean R36 twincharged mk1 Golf with GT45R don't you?

 

The original VW self study here

The new 180ps engine as found on Fabia VR5, Polo GTI, Seat and Audi A1 now EU5 compliant and sub 139g/km CO2. This a typcial example of engine downsizing where fuel consumption is reduced, without sacrificing customer engine response time or manimum available torque, from a usually much larger displacement engine.

 

That's the one, took me ages to find info on how the twincharger system worked. Gotta love the way they did it, much better use of parts than the turbo feeding supercharger that many do.

 

as much as i like this system, i do wonder why there is no diversion around the turbo, as it's only going to be a restriction around low engine rpms, you could even effectively piggy back off the previous solenoid control in reverse if you were to fit one surely?

 

not a nice engine to work on, no room in the engine bay - it's one of those you strip it down, have a huge pile of stuff and still a complete engine to strip down!!

main issues have been the pully for the charger squeeking, and pistons breaking up or valves sticking/poor seating
software update should of fixed the pistions, not seen many since it was implimented

goes like stink, so smooth on the power - not sure if I'd want to own one!

 

There is a diverter valve bolted to the turbo /pipe which also has plastic dipharm which gives up/cracks

 

Excellent post, but dont ever want to own one. God help anyone trying to repair one of these in 15yrs time,

Brian,

 

Super write up and information.

Lol, the charger spins at 17500rpm when the engine is at 2400rpm! lol So every time you drive a car with this engine the charger will be revving its nuts off!

To put it in perspective an eaton charger is rated at maximum 16000 rpm in OEM applications at peak engine rpm of say 7200rpm and these things do sometimes go wrong even though they hardly see peak revs, also the oil is never often changed but fit for life, this is not a good thing. Do these VW chargers have their own service intervals? I think they will need them, probably as often as long life oil...

 

Stuck.

 

I had put 14000rpm or so I thought! Thanks for the info, good link.

 

M45/M62 run 14,000 max con but can peak 16,000 rpm, those eaton's that vw use are smaller than m45(750cc) m62(1000cc), they are m23(500cc) Eaton's. Smaller mass less load so higher rpm rating. At a guess 16,000+ easy.

 

http://www.capa.com.au/eaton_mp62_4th.htm

 

thread revival!

whats the latest thinking on these twincharger 1.4s?

 

As a conversion or for motorsport?