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john B. john B. is offline
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Default Volvo's supercharger + turbocharger

On Sun, 21 Jun 2015 21:09:37 -0400, "Jim Wilkins"
wrote:

"Ed Huntress" wrote in message
.. .
For the gearheads:

If you think that engines are getting too complicated, you'll want
to
take a look at Volvo's T6 engine. It has both a mechanical
supercharger and a turbocharger.

This has been in the press for around a year, but the engine is
available in two cars, is in production, and is getting some
reviews.
Apparently it's very nice to drive. I wonder how nice it is to
repair...

The Eaton supercharger is there for low-end boost, to make the
2-liter
4-cyl. feel like a V8, with no turbo lag. At around 3500 rpm, a
clutch
disingages the supercharger and the turbo, which is now fully
spooled
up, takes over. It produces 302 hp and 295 ft.-lb of torque.

It's impressive engineering but I think they just tipped over the
edge. With direct injection, variable cam timing, and two types of
superchargers, it has to make mechanics gulp. I hope they've given
as
much thought to maintenance and repair.

--
Ed Huntress


This afternoon I was listening to the crew of a machine of similar
complexity, the B-29 bomber "Fifi". They had removed the turbos and
replaced the direct mechanical injection with carbs to cut down the
enormous maintenance, since they don't need the original high
performance.
http://www.aviation-history.com/engines/r3350.htm

-jsw

I hate to tell you but the article you reference is a bunch of bull.

The first B-29's, if I am not mistaken, were equipped with carbureted
engines and the change to fuel injection was a move to increase power
and reliability. The B-29's were equipped with twin turbos and an
internal supercharger and with the waste-gates open you could get
about 30" at full throttle stationary on the ground at just a bit over
sea level.

The engines ran perfectly well in summer temperatures on the ground in
Japan during the Korean "Police Action" and in fact the cowl flaps
were partially closed at take off as full open cowl flaps would over
cool the engine on take off as well as adding drag.

No pilot or flight engineer would have even considered doing a mag
check on take off roll. Take off was with the turbo waste gates
partially closed so manifold pressure was probably 10 or 15" over 30
inches and God only knows what switching off half the spark plugs
would do.

In addition the brakes on a B-29 were famously poor and if you had a
bad mag check aborting while on takeoff roll with a bomb load and max
fuel aboard would result in running off the end of the runway. Not a
recommended practice although exactly that did happen at Yokota AB in
about 1952 or maybe 53 for exactly that reason. An engine backfired on
take off roll and an inexperienced pilot pulled the throttles back.
The airplane went through the fence, sheered the landing gear off, the
center wing fuel tank ruptured and it caught fire. With a full load of
bombs aboard.

The compound engines that they talk about were a later version of the
R-3350 and added three small power recovery turbines to the engine.
Not used on the B-29 but were used on at least one version of the
Lockheed Constellation. I did talk to some of the mechanics that
maintained those airplanes and they cursed the engines but none of
them had worked on the B-29 :-)

How do I know all this? Because I worked on the things for nearly 5
years both at Randolph Field in Texas and Yokota AB in Japan during
the Korean set to and after that was settled in a reconnaissance
squadron at the same base.
--
cheers,

John B.