BIG DAMAGE By Lugging at LOW RPM? Eco Driving Warning! (Manual Gears)

[Logic]

https://www.youtube.com/watch?v=ndtG6zxK_BM

One thing he does not mention is hydrodynamic, mixed and boundary lubrication:

https://www.youtube.com/watch?v=9tlWDW4BQGI

Because the piston has to change direction, it has to slow, stop and then accelerate in the opposite direction.
Atlow rpm there will be more mixed and boundary lubrication.

[Isaac Zachary]

I would like to point out that many automatic transmissions will keep the RPMs a lot lower than your average manual transmission driver, even at higher engine loads.

I'm not sure about other hypermilers, but I tend to stay within the manufacturer's specifications, and often those minimum RPMs are lower than what you'd think they be.

I do think this guy might not know as much as he claims. How many turbo-charged engines have problems with too much compression at low RPM's? I noticed today that the Kenworth I was driving, that has a redline of 1,700 RPM has peak turbo pressure at around 1,200 RPM.

[freebeard]

Something ate my post?

[Logic]

Originally Posted by Isaac Zachary

I would like to point out that many automatic transmissions will keep the RPMs a lot lower than your average manual transmission driver, even at higher engine loads.

I'm not sure about other hypermilers, but I tend to stay within the manufacturer's specifications, and often those minimum RPMs are lower than what you'd think they be.

I do think this guy might not know as much as he claims. How many turbo-charged engines have problems with too much compression at low RPM's? I noticed today that the Kenworth I was driving, that has a redline of 1,700 RPM has peak turbo pressure at around 1,200 RPM.

I think the "too much compression at low RPM's" thing is a simple way of saying:

The crankshaft is still too close to vertical when when the majority of the charge is (already) burned.
ie: The piston, via the conrod, is trying to push the crankshaft down, out of the engine, rather than rotate it.

With a bit more rpm the crank has rotated more before burn, so the burn is actually rotating the crank more, rather than just push it down against the bearings.

Ideally the angle between the crank and conrod would be around 90 degrees during 'max burn'. But that's impossible wit a stock crank.


The CV Engine is an attempt to do/solve this:

https://www.youtube.com/watch?v=SM-ij4MQN9M

There's a better explanation/animation here IIRC

https://www.youtube.com/watch?v=nT7Id5zuA3Q&t=347s

[redpoint5]

I didn't watch, but it makes sense that higher combustion pressures would create more wear. Maybe efficiency and engine wear are at odds with each other?

[freebeard]

Boxer four. I approve.

Will it bolt up to a Beetle tranny?

[freebeard]

At first I thought it was just a Scotch Yoke

Scotch yoke
The Scotch yoke is a reciprocating motion mechanism, converting the linear motion of a slider into rotational motion, or vice versa. The piston or other reciprocating part is directly coupled to a sliding yoke with a slot that engages a pin on the rotating part. The location of the piston versus time is simple harmonic motion, i.e., a sine wave having constant amplitude and constant frequency, given a constant rotational speed. Wikipedia

....but I see they've added the teeth and 'flower'. There was an assertion that the pistons don't touch the cylinder walls; surely, it's just the side forces?

[Isaac Zachary]

Originally Posted by Logic

I think the "too much compression at low RPM's" thing is a simple way of saying:

The crankshaft is still too close to vertical when when the majority of the charge is (already) burned.
ie: The piston, via the conrod, is trying to push the crankshaft down, out of the engine, rather than rotate it.[/url]

I believe I see what you're saying, and it seems that's already mentioned in the first video.

Still, I'm pretty sure he mentioned something about turbocharged engines at low RPMs that didn't make sense to me. However, I just tried to find that without listening to the whole video again and couldn't. Maybe I misunderstood.

However, I still don't see all that compression at TDC being a real problem. The problem isn't compression. Lots of engines have a lot of compession from both the compression ratio as well as the ignition. Yesterday I drove a Kenworth yesterday with a max RPM of 1,700 RPM and normal crusing RPM of 1,000 RPM (or even lower) and has somewhere in the realm of a 17:1 compression ratio and sometimes well over 30 PSI at those RPMs, and this is considered normal. You also have to factor in that the pressure isn't the only force, reciprocating forces are also very real in an engine.

The main cause of damage in a lugging engine is not enough speed to create an oil film on engine parts.

And again, I do not recommend using an engine under load below the RPMs the recommended by the manufacturer. But generally, that can be as low as 1,000 RPM, or even less. And this is the manufacturer speaking, not me.

[Logic]

Originally Posted by freebeard

Boxer four. I approve.

Will it bolt up to a Beetle tranny?

NB that ONE 'gear' tooth has barely engaged at around the time of max burn/pressure.

Now normally the force from the burn is spread out over a large area in the big end bearing
vs
A line (of force) between the teeth..!
P=F/A so WAY! more pressure!

IMHO too much for a single line of force to handle through std engine oil = failure at that interface. (for/with any stock oil)

There's a video somewhere of their test engine coming to a stop.
Not a gradual slowdown; a dead stop!

So IMHO: A great idea if only there were a lube that can that line of force... sssh!

[Logic]

Originally Posted by Isaac Zachary

I believe I see what you're saying, and it seems that's already mentioned in the first video.

Still, I'm pretty sure he mentioned something about turbocharged engines at low RPMs that didn't make sense to me. However, I just tried to find that without listening to the whole video again and couldn't. Maybe I misunderstood.

However, I still don't see all that compression at TDC being a real problem. The problem isn't compression. Lots of engines have a lot of compession from both the compression ratio as well as the ignition. Yesterday I drove a Kenworth yesterday with a max RPM of 1,700 RPM and normal crusing RPM of 1,000 RPM (or even lower) and has somewhere in the realm of a 17:1 compression ratio and sometimes well over 30 PSI at those RPMs, and this is considered normal. You also have to factor in that the pressure isn't the only force, reciprocating forces are also very real in an engine.

The main cause of damage in a lugging engine is not enough speed to create an oil film on engine parts.

And again, I do not recommend using an engine under load below the RPMs the recommended by the manufacturer. But generally, that can be as low as 1,000 RPM, or even less. And this is the manufacturer speaking, not me.

Yoh! There's a lot to write down here, but yes you are correct, till you 'floor it!' at low rpm:

Back to piston ~at TDC where the condrod and crank are all in at straight line.
At low load throttle opening there's very little Air/Fuel being ignited so little load trying to push the crank straight down.

Not enough to force the oil layer out of small end, big end and main bearings,
so no metal to metal contact.

The/a turbo is not spooled up and turbo engines have a low compression ratio by nature, till the turbo spools up at higher RPMs providing that extra pressure/compression...

With today's engines being 'clever' the spark is likely retarded so that combustion occurs at a more advantageous crank angle.

Also the oil pump is not ;producing all the oil pressure it does at higher rpm.

But 'floor it!' (without downchange) and all that changes and you get the wear/damage discussed.

ie: Low rpms are OK at low load and its only the; more mixed and boundary lubrication and less oil pressure that might increase wear some.
But apply enough pressure to the bearing surfaces by flooring it and the oil layer is squeezed out and that's where the problem/s is/are.

The 'knock' discussed is not really the normal knock which occurs from too much spark advance or compression or hotspot pre-ignition; It's more that the crank has not rotated enough.