Electric motor assisted super- or turbocharger?

"Max Kallio" wrote in message
om...
2-stroke diesels need compressed air for starting the engine, so the
turbo (exhaust driven centrifugal supercharger) is out of a guestion
and it produces very little boost at low rpm anyhow.

Unfortunately, I avoided the opportunity to learn about these engines. My
father ran some
3 cylinder 2 stroke diesels in earth moving equipment some years ago and was
very happy with them. I believe they were turbocharged, but am not certain.
They may have started with a pony engine but again am not certain.

Can you fill me in on the details?

On Sun, 08 May 2005 22:17:29 GMT, wrote:


"Max Kallio" wrote in message
. com...
2-stroke diesels need compressed air for starting the engine, so the
turbo (exhaust driven centrifugal supercharger) is out of a guestion
and it produces very little boost at low rpm anyhow.

Unfortunately, I avoided the opportunity to learn about these engines. My
father ran some
3 cylinder 2 stroke diesels in earth moving equipment some years ago and was
very happy with them. I believe they were turbocharged, but am not certain.
They may have started with a pony engine but again am not certain.

Can you fill me in on the details?

Jimmy 371 - supercharged but not likely turboed.

wrote:

Jimmy 371 - supercharged but not likely turboed.

Actually the Jimmy 371 is a naturally aspirated engine. The piston
covers the intake opening in the cylinder wall before the exhaust valves
close. The Rootes Blower is there to improve exhaust scavenging not for
supercharging. The GMC 2 stroke cycle diesels generally are not
supercharged even though they have a Rootes Blower. If they also have a
Turbo then they are supped. I've probably missed something here. My
experience is with working on GM 2 stroke cycle diesels in power boats.

Gary Thomas

wrote:

"Max Kallio" wrote in message
om...

2-stroke diesels need compressed air for starting the engine, so the
turbo (exhaust driven centrifugal supercharger) is out of a guestion
and it produces very little boost at low rpm anyhow.


Unfortunately, I avoided the opportunity to learn about these engines. My
father ran some
3 cylinder 2 stroke diesels in earth moving equipment some years ago and was
very happy with them. I believe they were turbocharged, but am not certain.
They may have started with a pony engine but again am not certain.


Almost certainly Detroit Diesel 3-71 engines. There are millions of X-71
series engines still in use (X denotes the number of cylinders, and
there may also be a "V" in the designation: a V-12-71 denotes a V-12
with each cylinder displacing 71 cubic inches; a V-6-92 denotes a V6
with 92 cubic inch cylinders). Detroit Diesel is no longer producing any
of the 2-stroke series new, but they still support them and probably
will for another 20-30 years because there were so many built from ~1930
to ~2000.

In most earthmoving applications, the 3-71 was not turbocharged, but all
x-71 engines were supercharged with a roots blower (they won't run
without it, being 2-stroke engines). Pony engine start was common on
equipment made in the 40s and 50s, but electric start was almost
universal by the 60s, with compressed-air start being common on marine
and fixed engines.