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Idle Rpm...

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I have a Ritz vxi.

I would like to know the idle RPM of the 1.2 k series engine.

i found it to be around 650 rpm.

but not immediately after cranking . RPM just after cranking is 1000 rpm. its after a few minutes that it settles to 650 rpm. Is this normal? I hope so .

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hi,

Once you crank the engine, the driveshaft rotates at higher RPM initially, and settles down quickly to the relaxed levels.

These levels are different for different vehicles.

650RPM is way too low, and there is absolutely nothing to worry about.

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Not only in k series but in every MPFI engine you will notice this in both hot & cold condition (whereas carb engine starting was silent & quick). When we start the engine ecu deliver slightly richer mix and after few seconds it becomes normal. Idle RPM are different for different vehicle and mentioned in manual.

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There is nothing to worry about this behavior.

 

The engine ECU keeps the rpm at the higher level inorder to make the engine warm. You could notice this behaviour especially when the engine is cold.

 

The catalytic converter (used for pollution control) needs a min temperature after which it starts clearing out the harmful gases. Inroder to achieve the operating temperature fast, engine rpm is held at 1000rpm intially.

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@carispassion, and everyone else.

The startup RPM is higher not because the engine has to be warmed up, it is because the alternator has to be spun at a higher RPM than idle first so that it initiates its charging circuit. This is evident in the older cars like the Fiats. In the Fiats case, when you start the car without revving her at all, the engine check light remains on, but when you give the throttle a slight tap, the RPM increases resulting in initiating the Alternator's charging circuit, and then the check light goes away if you leave the throttle.

Hope that was satisfactory.

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Hello cyrus,

I think the point you have mentioend is very much valid.

 

However, could you kindly double check regarding the information about moden ECU controlled vehicles.

 

If I haven't went wrong, the high Engine rpm during warm-up was present for first generation MPFI vehicles onwards (Including my 2000 model Baleno).

 

Kindly refer the below link:

 

Says that, (Kindly refer to the information in Bold)

 

"

Control of fuel mixture

For an engine with fuel injection, an engine control unit (ECU) will determine the quantity of fuel to inject based on a number of parameters. If the throttle pedal is pressed further down, this will open the throttle body and allow more air to be pulled into the engine. The ECU will inject more fuel according to how much air is passing into the engine. If the engine has not warmed up yet, more fuel will be injected (causing the engine to run slightly 'rich' until the engine warms up)."

 

Posts merged.
BornFree2010-07-13 17:41:45

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Idle speed

From Wikipedia, the free encyclopedia

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Idle speed is the rotational speed the engine runs on when

the engine is uncoupled to the drivetrain and the throttle pedal isnt

depressed (generally measured in revolutions per minute, or rpm, of the crankshaft)

of a combustion engine. At

idle speed, the engine generates enough power to run reasonably smoothly and operate its

ancillaries (water pump, alternator,

and, if equipped, other accessories such as power steering), but usually not enough to perform useful

work, such as moving an automobile.

For a passenger-car engine, idle speed is customarily between 600 rpm and 1,000 rpm.

If the engine is operating a large number of accessories,

particularly air conditioning, the idle speed must be

raised to ensure that the engine generates enough power to run smoothly

and operate the accessories. Most air conditioning-equipped engines have

an automatic adjustment feature in the carburetor

or fuel injection system that raises the idle when the air

conditioning is running.

Engines modified for power at high engine speeds, such as auto

racing engines, tend to have very rough idle unless the idle speed

is raised significantly.

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Take it as equivalent of a 'light choke' from the carb days. Fast idle on start was standard even in the good ol' beetle in the late 60's, it had an automatic choke. One reason is also that a car pollutes most when cold, so warming up the engine asap is highly desirable.

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Due to Auto-Choke like phenomenon the MPFi car's engine Revs initially higher, reason as told by CYRUS & sg sir(i.e: to build Current strength & Optimum Engine temp)

& 650-700 Rpm for Ritz petrol is 100% alrite..smiley20.gif

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At idle speed' date=' the engine generates enough power to run reasonably smoothly and operate its ancillaries (water pump, alternator, and, if equipped, other accessories such as power steering), but usually not enough to perform useful work, such as moving an automobile.[/quote']

Idle rpm for my figo tdci is around 800rpm.And my automobile does move at this rpm merrily in 1st, 2nd and even 3rd gear :-P

I take advantage of this: instead of idling stationary for 2mins before and after the daily long drive, I move along in 1st and 2nd gear at the idling(800) rpm for first & last 500mts. It will smoothen the engine equally well smiley2.gif

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The reason engine idle speed is increased when the engine is cold is to overcome the increase in friction encountered due to lower than optimal operating temperature not to kick start the alternator or to warm the engine up faster. The reason you can start of and drive in most/all gears is due to the higher low end torque of a diesel engine, and as long as you dont rev it too high you do not have to run at idle for any length of time and can drive off as soon as you start we seem to have a lot of myths and incorrect things advised and passed down from generation to generation. As far as normal idle rpm the more cylinders the engine has the lower it is kept ie a 3cyl idles 800-900 4cyl 650-750.

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