I've seen this mentioned a few times. What does that mean exactly? Will this be a hurdle or a benefit when it comes to aftermarket tuning?

 

if my memory is correct, it is meant to negate, or in large part, eliminate turbo spool-up lag. i believe it endeavors to pre-spool the turbines, thus, anticipating boost and enabling extremely responsive power. for example, the R33GT-R is known to have nearly laughable factory turbo lag.

insofar as aftermarket, that is anyone's guess. i am sure that kind of setup is already available in some form, somewhere, as it is probably an adaptation from racing. maybe somebody else will speak to this.....

 

from a car and driver article (dated 2003):

"Quattro and 4MATIC—Meet ATTESA: Infiniti will begin offering an all-wheel-drive version of its hot-selling G35 sedan, fitted with Nissan's ATTESA E-TS (electronic torque split) system, in early December. Now comes word that an upcoming G35 platform mate, the Skyline GT-R, will get not only ATTESA E-TS but also a twin-turbo V-6 tuned by Cosworth. Producing in the neighborhood of 480 horsepower, the new V-6 features twin-turbo motor assist, a technology employed during off-boost periods—say, when idling—that temporarily turns the GT-R into a naturally aspirated car. Here's how it works: When off boost, magnetic valves open to form a bypass that redirects exhaust gas around the turbos and directly into the precatalysts; when on boost, the valves close and channel exhaust gas into the turbos. The net effect is a car reportedly capable of meeting strict emissions regulations around the world. Don't expect to see the GT-R, likely labeled an Infiniti when it comes to America, till 2005 or 2006."

the article seems a bit confusing in that off-boost renders any turbo car "naturally-aspirated," in essence. in a passenger car, the turbo is not boosting constantly under normal driving conditions. i think the article here (as dated as it is) describes only one feature of the electric assist, ie, it does not only feature the opeing and closing of bypass valves.

as this article describes:

Originally Posted by My Car Magazine - June 19th, 2005
SUPER SPORT SCOOP!

(excerpt)
...Breaking news this time is that the Twin-turbo V6 configuration has had it's capacity increased to 3700cc. With the increased capacity, it further assists low down torque in conjunction with the electric motor assisted twin turbos, creating instant positive boost pressure when throttle is applied, giving a 'linear pick-up engine'. We expect the engine to produce in excess of 380hp, and although far higher figures have been quoted, we expect a conservative figure - in line with previous GT-R outputs from factory.
http://www.7tune.com/file_dump/Japan/Scan10003.jpg

 

as well, this technology, the electrically assisted turbos, has already been in use, apparently for years, in diesel engine technology. big rigs.