On Sun, 21 Jun 2015 20:46:28 -0500, Ignoramus11174
wrote:

On 2015-06-22, John B wrote:
On Sun, 21 Jun 2015 17:40:11 -0400, Ed Huntress
wrote:

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.

The Detroit Diesel engine had both roots blower and turbo, in some
instances. And yes, I know what it as for but the roots "blower" did
give an intake pressure higher than atmospheric, thus was a
"supercharger" by definition :-)

And didn't VW market a car that had this system? Called the GT TSI, or
some such name. Back in 2005, or thereabouts.

Add variable valve timing (which is old hat now-a-days_) and Viola! A
NEW Design :-)

John B.


I have a forklift with a 2 stroke detroit engine with a roots blower.

They need to be supercharged, because of the nature of two stroke
diesel.

i

I should let John explain that, but the blower on a two-stroke diesel
is not there to supercharge the engine. Basically, it's just there to
"blow" air into the cylinders, at normal atmospheric pressure,
because the engine can't aspirate itself without the blower. This is
inherent in the engine design.

But, as he hinted, in can do a little supercharging while it's at it.
It's first a matter of port timing.

--
Ed Huntress