RPMs when driving

theholycow · **Posted:** Wed Mar 31, 2010 9:34 am

fa22raptorf22 wrote:

Also, it is very inefficient to climb a hill in high gear at low speed (IE 6th gear at 30mph)

That is very dependent on the car. My car climbs hills most efficiently in 5th gear at 30mph. If it had a 6th gear it would probably climb hills fine in 6th gear at 35.

kanine wrote:

I just wanted to make sure running RPMs low isn't the same as lugging the engine or would cost any harm. I get no shuddering or notice any problems when I drive that low in the RPMs.

Let's define a few things, then:
Low RPM - A subjective and relative term. As a concept, no problem.
Shuddering - Engine can't keep a steady RPM or car bucks/jerks.
Lugging - Severe ping/predetonation that can happen in antique engines run with heavy load at low RPM:
http://www.standardshift.com/forum/view ... 271#p91271

Quote:

I'm pretty sure that most people who think they have been lugging their engine really have not been lugging it at all. I'm not even sure that modern ECUs and knock sensors would let the engine lug. My experience with the Jetta so far has been that it either runs or stalls. I have not heared it lug (even when I accidentally took a corner in 4th instead of 2nd).

Putting a load on an engine at low RPM will make it growl, but growling is not lugging. Lugging is irregular. If it growls and goes it is not lugging (at least in my understanding of the matter).

http://www.standardshift.com/forum/view ... 10#p172612

Quote:

It isn't lugging. You'll never forget the sound of lugging once you do it. Sounds like a bunch of metal sh*t exploding under your hood. Or like a jackhammer.

Low RPM: OK. Enjoy.
Growling/groaning/rumbling: OK, but not recommended.
Shuddering: Don't panic, but try to avoid it and try to end it if it happens.
Lugging: It won't happen. If it does, stomp the clutch immediately.

fa22raptorf22 · **Posted:** Wed Mar 31, 2010 1:23 pm

Also, I just want to add...

For all MODERN ECU's ->
->You CAN NOT lug the engine, what so ever.
The ecu regulates all engine functions including monitoring the knock sensor, fuel input and rev limit.

Also to note, is that whenever you go under idle, regardless of throttle input, the ecu adds fuel to compensate and avoid stalling. This is good to note for "no gas" launches. As you let the clutch up and begin to stall the car...the ecu will compensate and add some power.

Also, if you floor it in 6th at like 20mph, if many cars you would lug....but with the ecu it regulates fuel input and just allows you to accelerate veeeery sloooowly.

theholycow · **Posted:** Wed Mar 31, 2010 2:16 pm

fa22raptorf22 wrote:

Also to note, is that whenever you go under idle, regardless of throttle input, the ecu adds fuel to compensate and avoid stalling. This is good to note for "no gas" launches. As you let the clutch up and begin to stall the car...the ecu will compensate and add some power.

To clarify: It will open the throttle and/or the IAC. It's not just going to go rich and dump in fuel that won't be burned, it lets in more air. Even without DBW it still may have a throttle actuator, or the IAC may flow enough to do the job.

Quote:

Also, if you floor it in 6th at like 20mph, in many non-computerized cars you would lug....but with the ecu it regulates fuel input and just allows you to accelerate veeeery sloooowly without lugging.

Added a little bit to that quote.

LHOswald · **Posted:** Wed Mar 31, 2010 3:04 pm

theholycow wrote:

fa22raptorf22 wrote:

Also to note, is that whenever you go under idle, regardless of throttle input, the ecu adds fuel to compensate and avoid stalling. This is good to note for "no gas" launches. As you let the clutch up and begin to stall the car...the ecu will compensate and add some power.

To clarify: It will open the throttle and/or the IAC. It's not just going to go rich and dump in fuel that won't be burned, it lets in more air. Even without DBW it still may have a throttle actuator, or the IAC may flow enough to do the job.

Quote:

Also, if you floor it in 6th at like 20mph, in many non-computerized cars you would lug....but with the ecu it regulates fuel input and just allows you to accelerate veeeery sloooowly without lugging.

Added a little bit to that quote.

tru fax

fa22raptorf22 · **Posted:** Wed Mar 31, 2010 6:47 pm

Gracias to you both. I was at work and having brain farts :lol:

Shadow · **Posted:** Wed Mar 30, 2011 1:15 pm

Okay, so the last post to this thread was nearly a year ago....shoot me for reviving it. But I had to add my two cents after reading some of the inaccurate comments.

Lugging an engine and ping/detonation/pre-ignition are not the same thing. Most people equate "lugging" with forcing the engine to operate at an RPM that is too low (usually below idle speed) and then attempting to accelerate from that RPM. This is possible on any car with a manual transmission. If anyone doubts this, just try driving your car up a hill with the RPM somewhere around 500 RPM (under normal idle RPM) in top gear. Trust me, you'll be lugging the engine. This is NOT good for your engine.

LHOswald · **Posted:** Wed Mar 30, 2011 1:23 pm

RPMs when driving? Over 9000

theholycow · **Posted:** Wed Mar 30, 2011 1:24 pm

The vague definition of "lugging" that is now in the vernacular, as you described, is not harmful. Taken to an extreme all the time I suppose it could produce abnormal wear, just as lots of other bad habits could.

The reputation for harm is from when "lugging" meant load-induced ping/detonation/pre-ignition.

Shadow · **Posted:** Wed Mar 30, 2011 4:08 pm

theholycow wrote:

The vague definition of "lugging" that is now in the vernacular, as you described, is not harmful. Taken to an extreme all the time I suppose it could produce abnormal wear, just as lots of other bad habits could.

The reputation for harm is from when "lugging" meant load-induced ping/detonation/pre-ignition.

Until now, I've never heard anyone refer to ping/detonation as lugging.

The definition of lugging as it applies to the rest of the world (not much sarcasm there) is indeed harmful to the engine. Anyone who drives a manual transmission should understand what is happening when he/she lugs the engine. There is a plethora of information available out there on the subject. A simple Google search will return hundreds of results!

paul34 · **Joined:** Fri Aug 11, 2006 1:10 pm **Posts:** 16784

Maybe, but modern engines really do not lug unless something is very, very wrong. I don't know what a lugging engine truly sounds like, although I'm sure I'd recognize it if it happened.

LHOswald · **Posted:** Thu Mar 31, 2011 1:47 pm

i think i told this story before but i've seen a chevelle stall and it was f*cking louuud. no idea what it really was until THC brought it up.

Shadow · **Posted:** Fri Apr 01, 2011 4:58 pm

paul34 wrote:

Maybe, but modern engines really do not lug unless something is very, very wrong. I don't know what a lugging engine truly sounds like, although I'm sure I'd recognize it if it happened.

With a manual transmission, you can lug the engine very easily. I don't think it is possible to lug an engine with an automatic transmission, at least I can't think of a way to do it.

RITmusic2k · **Posted:** Fri Apr 01, 2011 5:33 pm

Shadow, you and theholycow are using the same word to define two different phenomena, so you can't just keep going back and forth saying "no you can't / yes you can". You're not on the same page as each other.

Shadow · **Posted:** Sat Apr 02, 2011 8:28 am

RITmusic2k wrote:

Shadow, you and theholycow are using the same word to define two different phenomena, so you can't just keep going back and forth saying "no you can't / yes you can". You're not on the same page as each other.

That's what I said in the beginning. Go to Google and search on "lugging engine". I've yet to find a single site that uses the term "lugging" to refer to ping/detonation/pre-ignition etc... Everyone else in the world defines lugging as a general way to describe operating the engine at too low RPMs.

theholycow · **Posted:** Sat Apr 02, 2011 10:35 am

I have avoided taking the bait for at least these reasons:
- It looks like an invitation to a pissing match. I don't think anybody will be educated.
- It seems to be focused on a semantic issue but that issue cannot be put to bed without completing the technical discussion first.

Can this discussion be educational for others?
Would this discussion address the complete technical discussion first?

If the answer to both of those questions is yes
I believe the technical conditions that would need to be discussed and assessed for potential damage are these:

Did I miss any? How would we define "low RPM" and how would we define "heavy throttle"?

RPMs when driving

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