RPMs when driving

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Shadow
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Re: RPMs when driving

Post by Shadow »

theholycow wrote: How would we define "low RPM" and how would we define "heavy throttle"?
Lets just use "under normal Idle RPM" as the low RPM definition and a "wide open throttle" as the heavy throttle definition. And of course lets add in top gear operation (normally 5th or 6th on most modern cars with a manual transmission). That's really all it will take to lug an engine in a big way.

Under those circumstances, you'll definitely lug the engine until the RPMs rise. But you might not experience any ping/detonation/pre-ignition at all.
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Re: RPMs when driving

Post by theholycow »

I read the bit about connecting rods and bearings in some of the google results. Failures in those parts are extremely rare and I've never heard of such a failure attributed to driving habits.

I also read this in the BITOG thread that is the first google result:
"Before the days of electronic ignition and knock control, this advice made a lot of sense as pulling the vehicle in too high a gear for the speed generally will result in engine knock. This doesn't happen (well, almost never) in cars with knock control."

As for oil pressure...a light will come on when oil pressure is not within the optimal range. One should definitely do something about seeing that light. People equipped with a gauge can look up normal operating range and make sure not to approach its extremes. Anyway, I don't think this is an issue for anyone driving within the guidelines I describe below (based on an extension of the conditions you defined).

I do not want to shrug it off as semantics; I merely want to wait to address the semantic issue until after the technical issues are settled. I do not believe it is possible to put the semantic issue to bed until the technical issues are fully explored.
Shadow wrote:I'd just point you to hundreds of sites where they talk about lugging as I've described.
All I found were other forum discussions, no more authoritative than anything posted here. The variety of definitions was staggering and any one person would disagree with at least 50% of them (but not the same 50% as another person).
Shadow wrote:Lets just use "under normal Idle RPM" as the low RPM definition and a "wide open throttle" as the heavy throttle definition. And of course lets add in top gear operation (normally 5th or 6th on most modern cars with a manual transmission). That's really all it will take to lug an engine in a big way.
I believe that most people using the word "lugging" on this site are not in conditions anywhere near as severe as you describe. On this site it seems most commonly used to describe a marked change in engine noise pitch, which does indicate that you should downshift but does not indicate that you have done damage.

I can definitely 100% agree that you should not go below idle RPM (except during a gentle launch), not at any throttle level (let alone heavy or wide-open).

How about a few minimum guidelines?
  • - Do not go below idle RPM except during a no-gas or low-gas launch (and maybe some other situations I've forgotten). How far above idle RPM you need to be varies by car and situation.
    - If you are above idle RPM, maintaining speed/accelerating at part throttle or accelerating at WOT and not experiencing abnormal noise, you don't need to downshift just for the car's sake.
    - If you are experiencing what I call "growling" where there is a marked change in engine noise pitch/volume, you really should downshift.
    - If you're at/near WOT and not accelerating, at any RPM, you should downshift (even if you're not in a hurry).
    - If your gear choice is causing a warning light, you need to immediately downshift.
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Re: RPMs when driving

Post by Shadow »

theholycow wrote:I read the bit about connecting rods and bearings in some of the google results. Failures in those parts are extremely rare and I've never heard of such a failure attributed to driving habits.
It's not so much an ultimate failure that is the concern....simply because it would take a lot of "abuse" by the driver to cause such a failure. The real concern is damage over time. I've rebuilt many engines with rod bearing damage. Oil pressure is absolutely vital to the survival of rod bearings. Lugging the engine is one way to slowly destroy the rod bearings.

I also read this in the BITOG thread that is the first google result:
"Before the days of electronic ignition and knock control, this advice made a lot of sense as pulling the vehicle in too high a gear for the speed generally will result in engine knock. This doesn't happen (well, almost never) in cars with knock control."
No argument there....Again, I'm not talking about knock (aka ping/detonation/pre-igition etc...) I'm talking about the negative effects of lugging.

All I found were other forum discussions, no more authoritative than anything posted here. The variety of definitions was staggering and any one person would disagree with at least 50% of them (but not the same 50% as another person).
I didn't pay much attention to message forums. There are plenty of good technical articles to be found if you look for them. I also have a few tech books at home that address lugging. They are written for engineers though...

I believe that most people using the word "lugging" on this site are not in conditions anywhere near as severe as you describe. On this site it seems most commonly used to describe a marked change in engine noise pitch, which does indicate that you should downshift but does not indicate that you have done damage.
Right...and that's what I said earlier. I've only seen the term used as you have defined it on this site. The rest of the world seems to have a completely different definition of lugging. The reason I described it in such a severe manner was to illustrate a point. Most cars don't need such severe operating conditions to lug, but it does vary from car to car. Gearing plays a big role. The conditions I listed would cause lugging probably in any car imaginable.

How about a few minimum guidelines?
  • - Do not go below idle RPM except during a no-gas or low-gas launch (and maybe some other situations I've forgotten). How far above idle RPM you need to be varies by car and situation.
    - If you are above idle RPM, maintaining speed/accelerating at part throttle or accelerating at WOT and not experiencing abnormal noise, you don't need to downshift just for the car's sake.
    - If you are experiencing what I call "growling" where there is a marked change in engine noise pitch/volume, you really should downshift.
    - If you're at/near WOT and not accelerating, at any RPM, you should downshift (even if you're not in a hurry).
    - If your gear choice is causing a warning light, you need to immediately downshift.
Those are pretty good guidelines...I don't have a problem with any of them. But I still avoid hard acceleration (in any overdrive gears) at or near idle RPM.
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Re: RPMs when driving

Post by theholycow »

Continued from viewtopic.php?p=351691#p351691
Shadow wrote:To be fair, I'd say that 99.9% of the Internet agrees on engine lugging and exactly what it is.
Incorrect. The definitions from your google search (I hope you don't mind that I didn't wait around for your obnoxious LMGTFY) are even more varied and vague. Further, we cannot assume that any given user means the same thing when he uses the word, as they never do. For example, in that thread rml605 meant "vibrates and my rpms bounce below 1K", which does not match your first posted example of it on StandardShift.com ("under idle RPM", which you used twice more in this thread).

Any random user may mean any of a million things by it, it is not a standardized term no matter how much you tell us that it is. You always say to do a google search but I don't think you've ever looked at the results. You said "I didn't pay much attention to message forums. ", yet ALL of your recommended search results are forums.

This is exactly why I recommend describing the observed condition instead.

Why do you believe that we can assume that every user means the same thing when your own google search proves otherwise?
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Re: RPMs when driving

Post by Shadow »

theholycow wrote: Incorrect. The definitions from your google search (I hope you don't mind that I didn't wait around for your obnoxious LMGTFY) are even more varied and vague.
Actually, they aren't varied at all. The vast majority agree exactly what lugging is and how it happens.
Further, we cannot assume that any given user means the same thing when he uses the word, as they never do.
That's because people like you spread misinformation. You even have a link in your signature that points to your opinion that lugging isn't what you think it is and it's not happening to your engine (or some silly garbage like that!). Don't quote me because I'm not quoting you. I'm not going to look for your exact words again because it would be a waste of time.
For example, in that thread rml605 meant "vibrates and my rpms bounce below 1K", which does not match your first posted example of it on StandardShift.com ("under idle RPM", which you used twice more in this thread).
What rml605 is describing definitely seems like lugging. If his engine is vibrating and the needle on his tach is bouncing below 1K RPM, I think it's safe to say that he's lugging his engine. Oh, but I guess you disagree because you think it's impossible to lug an engine. Sorry kiddo, but you're 100% wrong there. ANY manual transmission car can be lugged quite easily.

Any random user may mean any of a million things by it, it is not a standardized term no matter how much you tell us that it is. You always say to do a google search but I don't think you've ever looked at the results. You said "I didn't pay much attention to message forums. ", yet ALL of your recommended search results are forums.
And I also said that I have engineering books with tech articles on lugging. Sorry, but I can't just zap them into your computer screen, so I'm just saying that ANYONE can do research via the Internet fairly easily. The reason I don't pay much attention to people on forums is because I have tech books written by experts. It should be clear by now forums can be a source of good information, but this thread proves that one should understand how to separate fact from fiction and/or opinion.

This is exactly why I recommend describing the observed condition instead.

Why do you believe that we can assume that every user means the same thing when your own google search proves otherwise?
I never said that every user means the same thing. Someone might say that he thinks he's lugging his engine, but when he describes what he's doing/what's happening, it's not lugging at all. Conversely, when someone describes what he's doing and what is happening with his engine as a result, it can usually be clearly determined if he's lugging his engine or not.

No matter what you say, it can be proven beyond a shadow of a doubt that a modern engine can be lugged.
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Re: RPMs when driving

Post by Shadow »

I also find it quite ironic that you're a moderator over at gassavers.org and you don't really get involved in many of the "engine lugging" threads on the forum. I browsed at least 20 threads that came up in a forum search over there, and I think you responded to maybe 2 of them. Hmm....could that be because just about everyone on that forum disagrees with your definition of lugging and why it is bad for your engine? :lol:
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Re: RPMs when driving

Post by kayubassist »

I think I lugged my car's engine once when I first started driving manual.
I took a right turn really fast at 4th gear and then there was an uphill. I couldn't downshift quick enough the engine made a horrible sound like someone banging on the hood of my car with a hammer, and the car stalled.
scary moment. lol
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Re: RPMs when driving

Post by SonicHKS »

Lugging? Yesterday I started off at 5 mph in 4th gear in my Fiero. Something like 500-600RPM (about 400RPM below idle). It just accelerated, I was so proud :mrgreen:.

I was turning right at an intersection and kinda forgot to downshift (long day), then when I was accelerating and realized it was 4th I almost downshifted but then realized it wasn't doing too bad.

Not bad for just about taking off from a stop in an overdrive gear :mrgreen:. Torque ftw
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Re: RPMs when driving

Post by noob5,000,000 »

Due to my FC's loud exhaust and my non-asshole nature, I regularly drove through neighborhoods at night at 600 rpm in 5th gear. Due to the ridiculously short gearing, that only got me like 20 mph.
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Re: RPMs when driving

Post by fr4n »

noob5,000,000 wrote:Due to my FC's loud exhaust and my non-asshole nature, I regularly drove through neighborhoods at night at 600 rpm in 5th gear. Due to the ridiculously short gearing, that only got me like 20 mph.
i can relate. except i dont have the torque at 600rpm to drive at 5th gear unless it was perffectly flat or downhill
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Re: RPMs when driving

Post by noob5,000,000 »

fr4n wrote:
noob5,000,000 wrote:Due to my FC's loud exhaust and my non-asshole nature, I regularly drove through neighborhoods at night at 600 rpm in 5th gear. Due to the ridiculously short gearing, that only got me like 20 mph.
i can relate. except i dont have the torque at 600rpm to drive at 5th gear unless it was perffectly flat or downhill
Yeah I never encountered an uphill in that condition. I don't know what would have happened :lol:.
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Re: RPMs when driving

Post by Shadow »

noob5,000,000 wrote: Yeah I never encountered an uphill in that condition. I don't know what would have happened :lol:.
Lug city. :lol:

BTW, what's the idle RPM on your car?
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Re: RPMs when driving

Post by noob5,000,000 »

Shadow wrote:
noob5,000,000 wrote: Yeah I never encountered an uphill in that condition. I don't know what would have happened :lol:.
Lug city. :lol:

BTW, what's the idle RPM on your car?
Factory spec is 750, mine was more like 800-850.
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