Low RPM load limits? Lugging?
 

What load limits do you use when you are at low rpms? I find that below 1500 rpm, operating at too high a load makes the engine sound and feel rough, which I assume is nearing the lugging point.

idle-1300: 40% load(sometimes a little more)

1300-1400: 50% load

1500-infinity and beyond: No limits

Below 1500 is probably always too low for flooring it for any purpose at all. But above that, in a naturally aspirated and relatively low-power engine that is also in good working order, there is not much chance of damage. ECUs will adjust timing and AFR as needed to avoid pre-detonation. Nonetheless, 1500 is my absolute bottom for relatively high load (75%, which is a long way from WOT). But generally I am at 1700 or higher as I accelerate. Been doing this for years all the time and have 248,000 miles on the original engine now. ;)

Great video here: https://www.youtube.com/watch?v=soJe...ature=youtu.be

In my Insight, the engine feels fine wide open down to maybe 1200rpm. At those low revs, even barely touching the pedal is enough to give it 100% load, because it needs so little air.

Edit: Recently passed 220k and it still runs like a brand new engine.

Drive by wire throttle won't let you do anything that's bad for the engine, IMO.

For my 8L engine build I would like to cruse along at 70mph turning 1,400rpm. If the engine doesn't like that I will have to change rear end gears.

Not nearing . It is the indicator of lugging. Roughness is lugging beyond what the computer is able to maintain smooth operation.

Number of cylinders and/or displacement count, imo.

My 3 cylinder Geo isn't much good under 2000rpm at heavy load, whereas my wife's V6 happily chuggs down the the highway at 1500rpm. My Miata (read: DOHC/high-revving) is a turd below about 2500 rpm.

That guy does such great tutorials. My head feels funny, did I just learned something?!!

Have I missed something here? All the BSFC graphs I see seem to show that the engine is less efficient at low RPM & higher load.

Here's mine:

https://i.imgur.com/aijThJR.jpg