lugging a Porsche engine

[javadog]

Originally posted by Paul Ferradas
Ah yes, that weird sound that it makes, almost like a rattle. I always wondered what that was. The PO warned me not to be alarmed and most Porsche's make this sound.

Most 911 gearboxes will make a rattling sound at low revs. You might also hear what sounds like a rattling noise from detonation. Either of these may be what you are hearing, not necessarily the sound of the engine being lugged.

JR

[snowman]

That rattle is not lugging, its detonation, very, very bad for your engine. It is only one bad result of lugging. Detonation can also occur under other conditions. If you start out from a stop in say 4th gear, you will lug down your engine, i.e. it will not spin freely but struggle to keep turning. That rattle is common for a high compression engine when it is lugged down. Lugging down an engine will not always result in that rattle. My M635 will start out from a dead stop in 3rd gear almost as easily as it does in first gear.

[real550A]

As others have stated here, lugging is being in too high of a gear
for the rpm/power range of the engine.
It's easy to equate with an automatic transmission equipped vehicle. They are designed to select the proper gear for you, thus
the downshift before lugging occurs on a hill, or when approaching
a stoplight.
Also, low rpm's = lower oil pressure. Your gauge will verify that one.

[timc]

I just always try to keep the rpm's above 2500, actually I try to stay right around 3k, unless I am idling or coasting.

[nabilious]

Its Detonation pure and simple. The "pop" happens before top-Dead-center and its spinning too slow to over come it so the piston rattles in its bore with a full, wide open throttle charge and it therefore wrecks the pistons, bores, and crank. The weakest of which snaps first (Crank in the 4cyl case) kinda up in the air on which snaps first on the 6 cyl example, but if I had to guess, it would be the cyl bores on the six as the cranks are really tough.
Thanks,
Nabil