driving on Low RPM

[henry33]

is driving on rpm lower than 2000 hurting the engine or damaging something ?
I have 6 speed manual trans.
thanks

[Pingouin]

I'd like to know as well. With my focus, I could happily move along at 1500RPM ish or lower, but my Yaris feels like it's struggling. I could also change gear at 2000RPM on the Focus, but the Yaris feels unhappy unless I hit 3000RPM.
I should try harder as I'm not going to save on petrol if I always have to rev higher :(

[henry33]

I was accustomed to do the same but have read somewhere that it is not good for Yaris engine:help:

[Yaris Hilton]

No, it won't hurt a thing.

[henry33]

glad to hear that thanks hilton

[tidus1203]

What's important is it does not lug, you know the engine vibrates due to lack of power on a given gear... If it does not lug then you're fine...

[henry33]

no the engine is able to run at 1500 rpm very smoothly and have enough power to accelerate without shifting down so it should be ok ;)

[why?]

No, it won't hurt a thing.

+ a bajillion. It will take time getting use to the Yaris, especially coming from a high torque car, but the Yaris runs fine in the low rpm ranges. I shift at 2000 rpm's and try not to ever go higher, and my car runs fine.

[TLyttle]

4-holers don't like to lug, and what is lugging is unique to every engine. I never push my Yaris below 2 grand, and it cruises fine at 1500. RPM isn't that big a problem for fuel economy, it is throttle opening that hurts...

[Pingouin]

I can confirm that my Yaris coasts fine at 1500RPM (in fact isn't it when the eco thingy that cuts off the petrol to save it goes off?) and I can change speeds at 2000RPM alright. It's just that coming from a 1.6L petrol car, the Yaris lacks serious punch when doing so. But I guess I can't have both that and high MPG! :D
Mind you, I leave in town, so I don't really ever need to floor it! Can't go much faster than the car in front of me, can I?

[henry33]

Tlyttle : how do you know when the throttle is opening ?

PIngouin : the same situation I am living in the city and when you have car in front it is hard to floor it down :D usually I am cruising at 50-60 km/h :)

[bankrobber]

Tlyttle : how do you know when the throttle is opening ?

PIngouin : the same situation I am living in the city and when you have car in front it is hard to floor it down :D usually I am cruising at 50-60 km/h :)

Throttle is open when gas pedal is pushed. Not a mechanic here but I dont think fuel injection has a throttle. It's all electronic right?

[Yaris Hilton]

If you don't hear knocking and the car doesn't shudder, you're not "lugging" an engine.

[RedRide]

A little common sense can go a long way. How low you should go on the RPMs is dependant on the gear and if you are going uphill etc.
Understanding this is part of driving.

One can get a feel if you are "luging" an enging and then, shift acordingly.

Lugging an engine can put more stress on the wrist pins, con rod bearings etc. It just simple, basic physics that it does. I'm not going to debate any one who says it doesn't.
The only thing that is debatable is at what point you are indeed lugging the engine and that point can only be determind by the imediate driving conditions, not by some sort of chart or table etc. :smile:

[detroiter]

You'll know your lugging the vehicle just as Hilton stated, you'll have next to no power/pull, car will be shuddering and feel like it's gagging to stay alive. As long as the car is running and pullin smooth, your smooth sailin

[RedRide]

You'll know your lugging the vehicle just as Hilton stated, you'll have next to no power/pull, car will be shuddering and feel like it's gagging to stay alive. As long as the car is running and pullin smooth, your smooth sailin
It's not a question of the enging running "smooth". Modern ECUs will always adjust things (timing fuel,etc) to make the enging run smooth.
The issue is subjecting the wrist pins, con rod bearings etc, to extra stress. Like I said, it's simple, elementry physics. :smile:

[detroiter]

Modern ecu or not, a car on the verge of stalling due to being lugged is going to happen regardless. So if what your saying is true, then your car would be running smooth at 200 rpms while it's choking to death going down the road. I don't see that happening.

[RedRide]

Modern ecu or not, a car on the verge of stalling due to being lugged is going to happen regardless. So if what your saying is true, then your car would be running smooth at 200 rpms while it's choking to death going down the road. I don't see that happening.

Well, of course you are going to stall the engine sooner or later. That is not the issue at hand.
I assume we are all "smarter than a fith grader". :smile:

[detroiter]

Agreed :D

But you would be surprised at how many are not as smart as a fifth grader lol. (not talking about anyone of us on YW heh)



Was their any particular reason anyone knows of as to why Toyota cheaped out on giving us a tach on the manual, yet the Sedan S comes with one? I mean even a base model Mazda 2 comes with a small, yet functional tach.

[bkrownd]

I pretty much cruise between 1600-2000 rpm all the time, where it has plenty of (gentle) acceleration on modest hills and never complains. (1.5 liter 5 speed manual)

My old FX usually has to stay above 2000 because there's no torque left at lower RPM.

[Yaris Hilton]

It's not a question of the enging running "smooth". Modern ECUs will always adjust things (timing fuel,etc) to make the enging run smooth.
The issue is subjecting the wrist pins, con rod bearings etc, to extra stress. Like I said, it's simple, elementry physics. :smile:

Simple, elementary physics says that what you are describing has nothing to do with lugging, but with throttle opening. The pressure on the wrist pins, con rod bearings, etc. is proportional to the pressure in the combustion chamber, IF you neglect the pressures due to centrifugal force and acceleration and deceleration of the reciprocating pistons. (That force is proportional to the square of the engine speed, so becomes less as the engine is slowed down.) The peak combustion pressure is closely related to the filling pressure of the cylinder with fuel-air mixture, and at low speeds you won't get the "ram" effect of a tuned intake manifold working with the cam timing that can fill a cylinder above atmospheric pressure at higher engine speeds. In normal combustion conditions, you will always have far more strain on the above mentioned parts with the engine turning at high speed than in the range where people worry about "lugging." The problem comes in when you get combustion knock or detonation in low speed, high throttle operation. That sudden spike of high pressure can overload the above named parts, and can crack pistons, rings and spark plugs as well. If the ECU can adjust timing and prevent excessive knocking, no damage results.

The other thing that most people have forgotten about now is that crankshafts have torsional vibrations with resonant frequencies. A couple of generations ago, it was common for inline 6 and 8 cylinder engines, with their very long, slender crankshafts often supported only by 3 main bearings, to have "critical speeds" in the low operating speed range. There was a fundamental torsional resonant frequency that could be excited by the power pulsations of the engine at a certain, usually rather low speed. Pushing the engine hard at that speed would cause rapidly increasing vibrations that could quickly result in a broken crankshaft. Sometimes there were similar resonant torsional vibrations in driveshafts, and either could cause the violent shuddering of the car I mentioned. Engineers tried to keep the critical speeds below where most people would drive and drivers were warned not to lug the engine. Modern engines have much stiffer crankshafts, better main bearing support, often are equipped with harmonic balancers to damp crankshaft vibrations, and typically don't have critical speeds in their operating range. It's of historical interest only, but the old warnings about damage from "lugging" go on like people still slow down on the highway to see what the problem was hours after the wreck has been cleared away.

[RedRide]

.............The pressure on the wrist pins, con rod bearings, etc. is proportional to the pressure in the combustion chamber,...............

You are failing to factor in the added resistance of the trans input shaft (to turn) on the crank when you are lugging the engine. All this added resistance is transfered to the WPs and crank.
It's basic physics my friend. :smile:

[Yaris Hilton]

There is no such added resistance of the trans input shaft. You're right, it is basic physics.

[RedRide]

There is no such added resistance of the trans input shaft. You're right, it is basic physics.

Perhaps in an alternate universe.
If there was no added resistance, there would be no need for different gears. The sole prupose of the various gears is to overcome the added resistance at the input shaft when needed.

I'm too old to argue that 1+1=2 :wink:

[RedRide]

Agreed :D

But you would be surprised at how many are not as smart as a fifth grader lol. (not talking about anyone of us on YW heh)



Was their any particular reason anyone knows of as to why Toyota cheaped out on giving us a tach on the manual, yet the Sedan S comes with one? I mean even a base model Mazda 2 comes with a small, yet functional tach.

Many auto manufactures often do strange and nonsensical things like that.
It can most likely be originally be traced to cost cutting measures.
Coporate accountants live in an esosteric, alternate reality.:wink:

[nick.dollimount]

The Canadian manual versions have a tach.