Go Back   Team-BHP > Under the Hood > Technical Stuff


Reply
 
Thread Tools Search this Thread
Old 14th July 2008, 12:54   #1
BHPian
 
Join Date: Jun 2007
Location: Kanpur
Posts: 32
Thanked: 0 Times
Default Ford Fiesta : What speed with respect to gear & rpm?

I purchased new fiesta 1.6 zxi petrol on 15th May. I just want to cross check my car's speed - gear - rpm match with a perfectly normal running
fiesta 1.6 petrol, or if it doesnt matter any car of similar spec.

In my car with Gear 4, and rpm 2000, the speed stays at abt 50~55km/hr.
If I remember well, it used to reach 60km/hr with rpm reaching 2000 for its first month of driving.

I am wondering why its there a drop in speed with respect to gear and rpm. Is it a normal behaviour for a new car when it is approaching its first service? or there is something wrong somewhere.
variozin is offline   Reply With Quote
Old 14th July 2008, 19:03   #2
BHPian
 
Join Date: Mar 2007
Location: Delhi
Posts: 254
Thanked: 2 Times
Default

Look in owners manual, for correct RPM to change gears for economic driving.

Second question is quite confusing me: earlier 4th gear @2000RPM was = 60km/hr

now 4th gear @2000RPM = 50-55Kmph.......

See Tacho reading (RPM reading) is taken from engine's crankshaft, Gear ratio for 4th will remain same as it was, no matter how old a car is.

that means engine running at same speed, but less speed at wheel in same gear, this means:

1: Clutch slipping, which is highly unlikely with a new car.
2: Some thing wrong with Speedo. Generall speedos have error( but error is constant, dont change with time).
3: Faulty Tachometer (usually accompnied with electronic surges), most likely to happen with tachometer, even with small surges or leakage.

Remedy: Drive another fiesta petrol in 4th gear @2000 RPM it should be in same range.

Dont think something serious has happened wit hyou new car, Just drive & enjoy it.
Me too have a new fiesta diesel back at home & I must say, it is a refined vehicle.
arunforu1 is offline   Reply With Quote
Old 14th July 2008, 22:10   #3
BHPian
 
Join Date: Jun 2007
Location: Kanpur
Posts: 32
Thanked: 0 Times
Default

thanks for your informative reply. I will try another fiesta 1.6. BTW its mostly advised not to drive with clutch half pressed while accelerating. But I think its not possible in backing and a little used in bringing the car into motion from stand still in 1st gear. So, I dont see any remarkable cause of clutch wear.
what do you say ? should I get my car raised on the hydraulic lifter for clutch examination?
variozin is offline   Reply With Quote
Old 15th July 2008, 00:11   #4
Senior - BHPian
 
Shan2nu's Avatar
 
Join Date: Feb 2004
Location: Hubli - Karnata
Posts: 5,525
Thanked: 87 Times
Default

To calcualte the right speed you need to know the gear ratio, final drive ratio and wheel size.

I think the FD is 4.25:1, not sure about wheel size and 4th gear ratio though.

Shan2nu

Last edited by Shan2nu : 15th July 2008 at 00:13.
Shan2nu is offline   Reply With Quote
Old 28th December 2008, 20:41   #5
BHPian
 
ariendj's Avatar
 
Join Date: Feb 2008
Location: Massachusetts
Posts: 503
Thanked: 79 Times
Default

i got my fiesta 1.6 ZXi two days back..
i had a doubt about my tachometer reading!!i didnt want to start a new thread and so asking it hear..
when idling the car at traffic signals or bumper to bumper trafiic with ac on(blower at speed 2 and inside air recirculation on) i find the rpm at 1000 and not going down.
btw,the clutch is fully pressed
ariendj is offline   Reply With Quote
Old 28th December 2008, 20:50   #6
Senior - BHPian
 
abhinav.gupta88's Avatar
 
Join Date: Sep 2007
Location: Delhi , India
Posts: 4,087
Thanked: 308 Times
Default

The clutch being full pressed does not change the car's rpm at idle.

Is it that the engine is cold at the time you are checking this reading?
abhinav.gupta88 is offline   Reply With Quote
Old 28th December 2008, 21:19   #7
Senior - BHPian
 
vnabhi's Avatar
 
Join Date: May 2007
Location: DC -> DC
Posts: 5,264
Thanked: 1,233 Times
Default

Quote:
Originally Posted by ariendj View Post
i got my fiesta 1.6 ZXi two days back..
i had a doubt about my tachometer reading!!i didnt want to start a new thread and so asking it hear..
when idling the car at traffic signals or bumper to bumper trafiic with ac on(blower at speed 2 and inside air recirculation on) i find the rpm at 1000 and not going down.
btw,the clutch is fully pressed
That is the normal rpm at idling with AC on. It is generally 900 rpm without AC. So relax and enjoy the car.
vnabhi is offline   Reply With Quote
Old 28th December 2008, 21:25   #8
BHPian
 
ariendj's Avatar
 
Join Date: Feb 2008
Location: Massachusetts
Posts: 503
Thanked: 79 Times
Default

Quote:
Originally Posted by vnabhi View Post
That is the normal rpm at idling with AC on. It is generally 900 rpm without AC. So relax and enjoy the car.
thanks now its peace of mind for me!!
ariendj is offline   Reply With Quote
Old 29th December 2008, 01:53   #9
BHPian
 
ascertain's Avatar
 
Join Date: Dec 2008
Location: Cannanore
Posts: 155
Thanked: 32 Times
Default

No effect of stepping on clutch on the RPM mate!. Idle RPM values you mentioned are pretty ok.No worries.
You can always get a tacho check if not satisfied.
ascertain is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Is Fuel efficiency strictly a function of RPM or is it speed+gear+RPM? Astleviz Technical Stuff 54 25th November 2011 09:22
changes in Euro-3 cars with respect to Euro2 speedsatya The Indian Car Scene 13 12th October 2009 11:24
Respect to All Ali G Introduce yourself 6 24th August 2007 03:57
Team Mclaren just lost a whole lot of respect. Rtech Int'l Motorsport 62 10th October 2005 21:42


All times are GMT +5.5. The time now is 17:58.

Copyright 2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks