rpm below idle rpm

tortoise · 23rd February 2007, 21:11

Experts!

Is it normal to have the rpm go below the idle rpm. I have observed in my fiesta 1.6 , after negotiating humps while the car picks up from low revs, the rpm needle touching 600 while the usual idling rpm is 800+.

I can experience low power (obviously.. it is almost as if the engine is about to shutoff) when this happens.

-tortoise

mail4ajo · 23rd February 2007, 22:11

Quote:

Originally Posted by tortoise

Experts!
Isthe rpm needle touching 600 while the usual idling rpm is 800+.
-tortoise

Correct me if I am wrong, isn't idling RPM usually set at +-1400?

Vid6639 · 23rd February 2007, 22:21

nope it's around 800rpm when warm. around 1200-1400 when cold.

revtech · 23rd February 2007, 22:22

thats on bikes....most cars have their idil RPM set at 800-1100 RPM.

Rev

sreenivass · 23rd February 2007, 22:27

my RPM on cold start is about 1400 and after warming up it goes some where between 600 and 800 RPM. I never had this feeling that it may shut off while idling at 600 RPM or 600+ RPM.

mail4ajo · 23rd February 2007, 22:40

Quote:

Originally Posted by vid6639

nope it's around 800rpm when warm. around 1200-1400 when cold.

Is it same for Carb type cars also? On my car, the idling increases on starting and gradually reduces. Since I dont have a tacho, cant say the RPM figure.

Vid6639 · 23rd February 2007, 22:43

nope not for carb only mpfi since it's controlled by the ECU. thats why you need to give throttle while starting in the morning for a carb engine.

theMAG · 23rd February 2007, 22:54

tortoise,

Its perfectly normal for the rpm to blip below warm-idling rpm. This is the engine directed by the ECU to a minimum rpm for fuel efficiency. The emphasis however is on the word blip.

gemithomas · 31st March 2007, 16:11

Was just thinking if its good to keep the RPM as low as possible while driving. I mean if you car can slowly pull up in 4th gear from 1000RPM onwards is it good to do this or would we be putting too much load on the engine. Will this affect the F.E figures.

mclaren1885 · 31st March 2007, 19:03

If the revvs are going lower than the idle range then check if your IAT sensor is fine .. It maybe loose at times ..

spatafarose · 1st April 2007, 11:30

Just increase your idle rpm and that will help

chetanhanda · 2nd April 2007, 00:01

Quote:

Originally Posted by spatafarose

Just increase your idle rpm and that will help

1n the 1st place stock car's idle rpm shouldn't be altered for such a reason, he hasn't altered his cams or fuelling system etc...

secondly, are you sure what you are talkin abt before giving such advice ?
how can you alter the RPM anyway ? are you aware of the basics of how a car engine works ?

shineshine · 2nd April 2007, 00:51

Quote:

Originally Posted by spatafarose

Just increase your idle rpm and that will help

Your answer is logically correct. But seems to be useless.
The idle RPM for carburated engines can be adjusted by turning a screw in most cases. But it not that simple in ECU controlled engines. It needs sophisticated connections and a good knowledge in ECU programming.

23rd February 2007, 21:11	#1
tortoise BHPian Join Date: Sep 2006 Location: Bangalore Posts: 170 Thanked: 69 Times	rpm below idle rpm Experts! Is it normal to have the rpm go below the idle rpm. I have observed in my fiesta 1.6 , after negotiating humps while the car picks up from low revs, the rpm needle touching 600 while the usual idling rpm is 800+. I can experience low power (obviously.. it is almost as if the engine is about to shutoff) when this happens. -tortoise
	() Thanks

23rd February 2007, 22:21	#3
Vid6639 Team-BHP Support Join Date: Jul 2006 Location: Bangalore Posts: 17,757 Thanked: 43,812 Times View My Garage	nope it's around 800rpm when warm. around 1200-1400 when cold.
	() Thanks

23rd February 2007, 22:22	#4
revtech Senior - BHPian Join Date: Nov 2004 Location: Bombay Posts: 1,992 Thanked: 39 Times View My Garage	thats on bikes....most cars have their idil RPM set at 800-1100 RPM. Rev
	() Thanks

23rd February 2007, 22:27	#5
sreenivass BHPian Join Date: Oct 2006 Location: Bangalore India Posts: 932 Thanked: 44 Times View My Garage	my RPM on cold start is about 1400 and after warming up it goes some where between 600 and 800 RPM. I never had this feeling that it may shut off while idling at 600 RPM or 600+ RPM.
	() Thanks

23rd February 2007, 22:43	#7
Vid6639 Team-BHP Support Join Date: Jul 2006 Location: Bangalore Posts: 17,757 Thanked: 43,812 Times View My Garage	nope not for carb only mpfi since it's controlled by the ECU. thats why you need to give throttle while starting in the morning for a carb engine.
	() Thanks

23rd February 2007, 22:54	#8
theMAG Distinguished - BHPian Join Date: May 2006 Location: Avon, CT Posts: 7,217 Thanked: 1,811 Times View My Garage	tortoise, Its perfectly normal for the rpm to blip below warm-idling rpm. This is the engine directed by the ECU to a minimum rpm for fuel efficiency. The emphasis however is on the word blip.
	() Thanks

31st March 2007, 16:11	#9
gemithomas Senior - BHPian Join Date: Jan 2007 Location: Trivandrum Posts: 2,366 Thanked: 143 Times View My Garage	Was just thinking if its good to keep the RPM as low as possible while driving. I mean if you car can slowly pull up in 4th gear from 1000RPM onwards is it good to do this or would we be putting too much load on the engine. Will this affect the F.E figures.
	() Thanks

31st March 2007, 19:03	#10
mclaren1885 BANNED Join Date: Jul 2005 Location: Bangalore (the city of modded cars) !! Posts: 4,820 Thanked: 46 Times View My Garage Infractions: 0/1 (10)	If the revvs are going lower than the idle range then check if your IAT sensor is fine .. It maybe loose at times ..
	() Thanks

1st April 2007, 11:30	#11
spatafarose BHPian Join Date: Mar 2007 Location: Cochin Posts: 32 Thanked: 0 Times	Just increase your idle rpm and that will help
	() Thanks