Your Opinion Wanted - RPMs vs Engine Load

[BuickGN]

Originally Posted By: AEHaas
I think this is an easy one. Wear is both load and RPM dependent. The load is exactly the same in both cases. You are pushing the car at the same speed. You will have less wear with lower RPM.

We all talk about lugging an engine. I have never seen any data to suggest this condition increases wear and in your event I do not think you are lugging it anyway.

aehaas


When I think of lugging a motor, I think of people who can't drive a manual and won't downshift until rpms are below 500rpm. I have friends that will slow down in top gear and then try and accelerate away from 500rpm or less. That's when lubrication becomes marginal and you hurt things. Spinning a motor at 2,400rpm is not lugging it. It might be gutless and out of it's powerband but it's not lugging or hurting anything.

I think higher load, less rpms would be better to a point. You reduce pumping losses and have less power strokes per mile traveled. Granted each power stroke is more powerful. All in all, it probably works out about the same.

 

[OriginHacker21]

Originally Posted By: BarkerMan


Is this the grade near Temecula?



This is north of the I-210 and the I-10 - north of Fontana. I go north on the I-15 for 10 minutes and right before Victorville you have that hill.

Yeah Temecula is south - bout an hour and a half.

 

[OriginHacker21]

Re: Rationull

Thanks for your big post showing the two results of driving each way. Your post was very informative - I didn't know bout that till now. Thanks for taking the time to write it. I agree 100%.

 

[OriginHacker21]

Originally Posted By: BuickGN
Originally Posted By: AEHaas
I think this is an easy one. Wear is both load and RPM dependent. The load is exactly the same in both cases. You are pushing the car at the same speed. You will have less wear with lower RPM.

We all talk about lugging an engine. I have never seen any data to suggest this condition increases wear and in your event I do not think you are lugging it anyway.

aehaas


When I think of lugging a motor, I think of people who can't drive a manual and won't downshift until rpms are below 500rpm. I have friends that will slow down in top gear and then try and accelerate away from 500rpm or less. That's when lubrication becomes marginal and you hurt things. Spinning a motor at 2,400rpm is not lugging it. It might be gutless and out of it's powerband but it's not lugging or hurting anything.

I think higher load, less rpms would be better to a point. You reduce pumping losses and have less power strokes per mile traveled. Granted each power stroke is more powerful. All in all, it probably works out about the same.



Yeah, I've seen people like that where they lug the [censored] out of their manual transmission cars. Some of my relatives do that - where they start out in second gear because "its less shifting" but it sounds like you're listening to a rap song with the bass all the way up.

I never operate my car below 2000 rpms if I can help it because theres basically 0 power there (only if I'm off the gas).

At 2400 rpms the engine does have sufficient power to keep the engine LOD below 90% and keep a 70mph speed.

I do approach the hill at 85mph - but I keep the engine LOD under 90% - and by the time I get to the top of the hill I'm going 65mph.

Thanks for the info!

 

[biomed_eng_2000]

Power losses due to friction are nearly proportional to engine RPM. Thus, the higher the RPM, the more losses. The more losses you have equals more heat. More heat means more oil degradation.

Bottom line...keep the rpm's lower if you desire less oil wear.

 

[eljefino]

I did some scantool.net software scanning of my 96 saturn some time ago, and also noticed about a 30% load at idle, 10% on decelleration. Scanner ran on an ELM3xx chip.

My belief, and it's all it can be, as I'm not privy to "insider" PCM programming information, is that the "load" as reported, unencrypted over the OBD-II bus, is basically a "bias" kind of like block learn. It is internal information useful only for the PCM to set spark advance, EGR use, fuel enrichment, auto trans shifting. It is not a linear measurement of engine output.

Personally, I would take the hill a little slower, so aero drag, which increases exponentially, will not add to your problems. Probably means 4th gear.

 

[swalve]

Originally Posted By: rationull
For everyone voting option 1, doesn't it seem like heading uphill at 2400 RPM would lug the engine? I've never driven an ecotec, but that just seems a little low for a hill climb.


Sweet [censored], 2400 rpm isn't anywhere near lugging the engine. My car does 2000 rpm at 70mph.

 

[swalve]

I didn't know the Christian savior's name gets censored?

 

[XS650]

Originally Posted By: swalve
I didn't know the Christian savior's name gets censored?


Huckabee

Nope, not censored.

 

[rationull]

Originally Posted By: swalve

Sweet [censored], 2400 rpm isn't anywhere near lugging the engine. My car does 2000 rpm at 70mph.


What's the displacement of your engine, though? How much torque is it putting out at 2000 RPM?

 

[Duffman77]

Option 2 vs option 1,

The only advantage to option 2 would be less bearing wear (& maybe ring wear, not sure)

Option 2 will have more wear on everything that is not load dependent such as the entire valvetrain, all external engine accessories and possibly the rings due to additional revolutions.

I have always believed in option #1 as long as the engine isnt pinging. I think of it in terms of Motorcycles and semis, one goes about 40,000 before rebuild and the other goes half a million, one redlines around 13K and the other around 2.5K.

Little four cylinder engines have a safety built into them. A lot make thier peak torque at 3000rpm or higher, so you cant load an engine higher at 2400 than you can at 3000 because the engine is designed to flow more air at its peak torque and carry more load at that rpm.

 

[swalve]

Originally Posted By: XS650
Originally Posted By: swalve
I didn't know the Christian savior's name gets censored?


Huckabee

Nope, not censored.
Ha! Good one.



Originally Posted By: rationull
Originally Posted By: swalve

Sweet [censored], 2400 rpm isn't anywhere near lugging the engine. My car does 2000 rpm at 70mph.


What's the displacement of your engine, though? How much torque is it putting out at 2000 RPM?
Well, it IS a supercharged 3800. But still, if the theory is that the bearings get smashed, does it matter?

 

[rationull]

Originally Posted By: Duffman77

Little four cylinder engines have a safety built into them. A lot make thier peak torque at 3000rpm or higher, so you cant load an engine higher at 2400 than you can at 3000 because the engine is designed to flow more air at its peak torque and carry more load at that rpm.


I'm not quite sure what you're saying here, but I'm curious. My civic, for example, makes its meager peak torque at 4300 RPM. You're saying it's impossible for me to load the engine more at 2400 RPM than at 4300 RPM why exactly? If I'm at 4300 RPM at 1/4 throttle or at 2400 RPM at WOT to maintain the same vehicle speed against and incline, each power-stroke has to support more load at 2400 RPM. Doesn't that count as a higher engine load?


Originally Posted By: swalve
Originally Posted By: rationull

What's the displacement of your engine, though? How much torque is it putting out at 2000 RPM?
Well, it IS a supercharged 3800. But still, if the theory is that the bearings get smashed, does it matter?


My thought was that it would matter because the 3800 might be putting out enough torque to keep the car moving despite the lower engine speed, and presumably the engine would be built to handle that torque at that speed. But I don't necessarily claim to know what I'm talking about here.

Take an example situation: a 4-cylinder car going up a hill at 2400 RPM (or whatever). To go up this hill at that engine speed and maintain vehicle speed (or perhaps to lose speed very slowly), this particular example engine requires the throttle to be wide open. Will running the engine against a load (because of the incline) that requires the throttle to be fully open and the engine to supply as much power as it can not be much harder on the bearings/internals than running it at a higher speed where less throttle opening is required? (With the acknowledgement that there's higher friction-related wear at the higher engine speed).

I'm not trying to be dense here, I'm really interested in this. I've always thought that if you had to go WOT or close to it just to maintain speed that you were putting too much stress on the engine internals. It sounds like this conversation is going in the direction of saying that's not true (barring cases where your engine speed is too low to provide adequate lubrication, which probably varies between engines).