Audi is working on a new bi-turbo engine which uses an electrically-driven turbocharger to completely eliminate turbo lag and markedly increase standing-start performance.
The prototype is based on Audi’s new 3.0-litre V6 TDI Bi-turbo engine, and is described by the company as being in the ‘development phase’. This experimental V6 diesel uses a conventional exhaust-driven main turbocharger with the small motor-driven turbocharger being used exclusively at low speeds.
Reducing turbo lag - the gap between the driver pressing the accelerator and the effect of the turbo’s boost - has been the subject of engineer’s efforts for three decades. The fundamental problem is the need for a sufficient volume of exhaust gasses to be generated by the engine and then directed at the turbocharger, in order to get it running at high speed.
However, when the engine is running at lower speeds, the volume of gas isn’t enough to spool the turbocharger up to its operating speed. Current turbocharged engines get around this problem by using two turbos. The smaller turbo can be brought into action with smaller volumes of exhaust gas and bridges the gap until the bigger turbo can be brought into play.
Audi’s new system, however, totally eliminates lag, greatly boosts low-speed performance and is fundamentally simpler than the twin-turbo and triple turbo set-ups used by the likes of BMW.
Audi’s electric turbocharger sits in the induction system, downstream of the conventional turbo and the intercooler and is normally not operative. However, at very low speeds - particularly from standstill - the air charged by the main turbo is re-directed through the electric turbocharger, which is already spinning at high speed, and pushed with much greater force into the engine.
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TegTypeR
At last, I may enjoy driving
At last, I may enjoy driving a blown engine!
RPrior
Turbo Lag is only a memory.................
Strange comment.
My experience of Turbo diesel installations is that the turbo is on song well under 200rpm, and the low speed torque characteristics of these engines is significantly boosted by Turbo installations.
BMW's amazing new 381 bhp 740 Nm 45 mpg triple turbo diesel, must be considered as one of the performance engines of all time.
We are an eon away from the early turbo petrol units with huge turbo lag.
jer
Interesting, suprised it
Interesting, suprised it has'nt been done before. Not as though it would take much electricity to spin up a small low friction turbo?
Is'nt the induction system upstream of a conventional exhaust turbo?
mike_d_dunn
Vorsprung durch technik
First the Audi e petrol & diesel production and now this, seems the engineers at Audi have woken up!
marineboy
Nothing new under the Sun.
So, 70 years after low speed electric induction charging became the norm in marine diesel engines, the penny has finally dropped at Audi. Vorsprung durch alt technik!
skiwi
Yes, the great degree of similarity between marine
and automotive engines explains the considerable use of marine units, and their technology, in the automotive sector....
takumiuk
What's the Difference??
Okay, not a tech head AT ALL. But whats the difference / benefits from this system (elec & conventional turbos) to the VW Groups supercharged & turbo charged engine, apart from ones diesel and one's petrol.
Supercharger runing off the crank = no lag then turbo kicks in when the pressure's up. Tried and tested and same result.
Is there a cost implecation or further fuel savings although don't the latest efficency programs (BMW ED, Merc Bluemotion) deactivate electrically driven ancilliaries to lower the drain on the system so the alternator doesn't rob a chunk of power / strain on engine, increase in MPG
Je ne comprenda pas
kcrally
An electric turbocharger
An electric turbocharger should be cheaper all round, than a supercharger. Alot less complicated as well.
A34
Its an electric supercharger!
... as "turbocharger" is used for exhaust driven inlet charging, "supercharger" for non-exhaust driven inlet charging. By popluar convention in English, anyway. I guess in German the terminology is different, and thence the translation mistake!
LP in Brighton
Why not have a single electric turbocharger?
I wounder if the Audi engineers considered using just a single electric turbocharger? I know that on its own this would be less efficient than the current system, however would it not be possible to use an exhaust driven generator (basically half a conventional turbo, but with an alternator in lieu of the compressor)?
Such an arrangement could I believe deliver the best performance and efficiency. Then again, maybe it would not be easy to make a generator work at the kind of rotational speeds that turbochargers work at...
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