Car's speed and RPM value discrepancy!

lordofgondor · 17th September 2010, 13:45

Hey fellow BHPians!

This may (or may not) sound like paranoia to you, but I have been noticing some discrepancy with the speed of the car and the value in the tachometer. The car in question is Maruti Esteem MPFI, 2007 model.

Till a few months back, in 3rd gear the speed and RPM unflinchingly used to be 40Km/1500 respectively and in 4th gear, they were 60Km/1500 respectively. Now the RPM has increased for the same speeds. Instead of 1500, it sometimes goes to 1800

and very few times stays at 1500. I've watched this very closely, and the figures are correct. My driving style hasn't changed wee bit and the car get serviced at regular intervals.

Now my question: Is there something wrong with the gearbox? Or anything going wrong somewhere else? Or is it simply my paranoia?

suman · 17th September 2010, 13:56

Abhinav, this could be a sign of clutch slippage.

aroop · 17th September 2010, 14:08

Even I think its a case of slipping clutch.

My wagon R had this problem till I got the clutch changed.

427Cubes · 17th September 2010, 14:26

Seems like a worn out clutch. How may KMs has your car done so far? Another test you could do is to floor the gas pedal in 4th or 5 th gear at around 30-40 kmph speed and see if your RPM spikes up without corresponding acceleration of the car. Please do this only on a road that does not have traffic. If you are not sure visit your car mechanic.

lordofgondor · 17th September 2010, 14:31

Quote:

Originally Posted by suman

Abhinav, this could be a sign of clutch slippage.

Quote:

Originally Posted by aroop

Even I think its a case of slipping clutch.

My wagon R had this problem till I got the clutch changed.

Thanks Suman Da and aroop! So I guess it's time to get the pressure plate & clutch checked.

One curious thing though, I'd done the slippage test (handbrake on, 2nd gear engaged and slowly lift the clutch) and the engine got killed immediately.

lordofgondor · 17th September 2010, 14:44

Quote:

Originally Posted by 427Cubes

Seems like a worn out clutch. How may KMs has your car done so far? Another test you could do is to floor the gas pedal in 4th or 5 th gear at around 30-40 kmph speed and see if your RPM spikes up without corresponding acceleration of the car. Please do this only on a road that does not have traffic. If you are not sure visit your car mechanic.

The car's only done ~40K Km, but it's been through lotta rough & tough places in HP, UK & Ladakh. Also I had to get the clutch plate changed due to a misadventure in Ladakh.

I'll do the test that you've suggested tonight on an empty road and will let you know the results.

Shan2nu · 17th September 2010, 14:45

It could also be a tacho or speedo error due to wear.

If a clutch reaches a point where it slips at 1500rpm while cruising, you would prob have a really tough time getting the car to move from a standing start.

So get the tacho/speedo checked first.

Shan2nu

lordofgondor · 17th September 2010, 15:17

Quote:

Originally Posted by Shan2nu

It could also be a tacho or speedo error due to wear.

If a clutch reaches a point where it slips at 1500rpm while cruising, you would prob have a really tough time getting the car to move from a standing start.

So get the tacho/speedo checked first.

Shan2nu

Interesting! All the more, cause I have never had any problems with a standing start, even on the steep inclines of Jalori Jot. So would a competent mechanic be able to check them, or a visit to MASS is warranted?

Shan2nu · 17th September 2010, 16:07

Quote:

Interesting! All the more, cause I have never had any problems with a standing start, even on the steep inclines of Jalori Jot. So would a competent mechanic be able to check them, or a visit to MASS is warranted?

Take you car to MASS and get an OBD check done. They will compare the actual engine revvs to the one shown on the tacho meter. If you get an accurate reading, then take the car for a spin and do the same for the speedo.

YouTube - Tachometer Inaccuracy

Shan2nu

lordofgondor · 21st September 2010, 20:50

Quote:

Originally Posted by Shan2nu

Take you car to MASS and get an OBD check done. They will compare the actual engine revvs to the one shown on the tacho meter. If you get an accurate reading, then take the car for a spin and do the same for the speedo.

Shan2nu

Thanks for the info buddy!

The video depicts exactly what I am seeing with my car. Time to fix up a timing with the MASS folks.

17th September 2010, 13:45	#1
lordofgondor BHPian Join Date: May 2007 Location: UP 16 Posts: 936 Thanked: 159 Times	Car's speed and RPM value discrepancy! Hey fellow BHPians! This may (or may not) sound like paranoia to you, but I have been noticing some discrepancy with the speed of the car and the value in the tachometer. The car in question is Maruti Esteem MPFI, 2007 model. Till a few months back, in 3rd gear the speed and RPM unflinchingly used to be 40Km/1500 respectively and in 4th gear, they were 60Km/1500 respectively. Now the RPM has increased for the same speeds. Instead of 1500, it sometimes goes to 1800 and very few times stays at 1500. I've watched this very closely, and the figures are correct. My driving style hasn't changed wee bit and the car get serviced at regular intervals. Now my question: Is there something wrong with the gearbox? Or anything going wrong somewhere else? Or is it simply my paranoia?
	() Thanks

17th September 2010, 13:56	#2
suman Senior - BHPian Join Date: Sep 2005 Location: Kolkata Posts: 4,589 Thanked: 279 Times View My Garage	Abhinav, this could be a sign of clutch slippage.
	() Thanks

17th September 2010, 14:08	#3
aroop BHPian Join Date: Mar 2008 Location: Kolkata Posts: 128 Thanked: 23 Times	Even I think its a case of slipping clutch. My wagon R had this problem till I got the clutch changed. Last edited by aroop : 17th September 2010 at 14:10.
	() Thanks

17th September 2010, 14:26	#4
427Cubes Newbie Join Date: Jan 2010 Location: Ghaziabad Posts: 24 Thanked: 9 Times	Seems like a worn out clutch. How may KMs has your car done so far? Another test you could do is to floor the gas pedal in 4th or 5 th gear at around 30-40 kmph speed and see if your RPM spikes up without corresponding acceleration of the car. Please do this only on a road that does not have traffic. If you are not sure visit your car mechanic.
	() Thanks

17th September 2010, 14:45	#7
Shan2nu Senior - BHPian Join Date: Feb 2004 Location: Hubli - Karnata Posts: 5,533 Thanked: 125 Times View My Garage	It could also be a tacho or speedo error due to wear. If a clutch reaches a point where it slips at 1500rpm while cruising, you would prob have a really tough time getting the car to move from a standing start. So get the tacho/speedo checked first. Shan2nu Last edited by Shan2nu : 17th September 2010 at 14:48.
	() Thanks