Here  are some shots of a variable vane turbo I took at the
LA Auto Show last week. These are on a new Porsche motor. Looks ideal
for our use as one can control the turbo RPM and HP directly.
I think they are Borg Warner turbo's. They will also be real good
for a turbo compound application.

Note how the CAT is mounted directly on the output of the turbine.

Paul Lamar ...No rotor no motor.

I think the turbo on the 5 cylinder diesel in the Mercedes (Dodge,
Freightliner) van is also variable vane.

Chris Cosman

Here is some more info on variable van turbo's.

Paul Lamar

Yes, the Dodge Sprinter's Mercedes-Benz 3.0L diesel has the variable
geometry turbo giving 240 FT/lbs of torque from 1200 - 2400 rpm.
http://www.worldcarfans.com/2050506.005/dodge-sprinter-in-line-five-cylinder-turbo-diesel

Also the new Dodge 6.7L Cummins diesel has the variable geometry turbo -
http://www.dodge.com/en/2007/chassis_cab/powertrain/cummins_diesel/

-dave

Well the big problem with the diesel engine is acceleration.
They have no air throttle. The intake manifold is wide open all
of the time. At low loads the diesel can run very lean indeed.
The way to get a diesel engine to accelerate is pump in more fuel
and make it momentarily richer. If taken too far black smoke is
emitted which is carcinogenic. You will see whole clouds  of black
smoke emitted in diesel tractor pull contests.

Do you want to tow or do you want to go? :)

A way is needed to pump more air and fuel simultaneously keeping the mixture
in the right range and out of the smoke range. That is why the variable vane turbo
is used with diesels. Other types of assisted turbos were tried in the past.
A few years ago I thought the electric assisted turbo was going to
catch on. Apparently that did not happen. Garret even developed a hydraulic
motor assisted turbo years ago.