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Old 14th May 2006, 09:45   #1
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Default Help with Rpm vs Speedo Speed

Hi Guys,

Have encountered a wierd problem(if you call it that) in my Getz which has clocked approx 7000kms and is 6 months old. Just took it for the 2nd free service and I got a report saying my clutch is slipping and needs to be replaced. I asked him how he arrived at this diagnosis as I had no clutch related complaint.

He said that at the speed of 60kmph in 5th gear the car should be doing approx 1600RPM whereas my car was doing approx 1900RPM. I confirmed this by driving 4 others Getz cars from their workshop and they all showed approx 1600RPM.

There is no indication of slippage under any style of driving as per me. I had made a complaint of drop in FE and pickup after filling suspected adulterated fuel a week before service as follwing that my car was not performing the way it used to.

Can any of you guys come out with why my RPM is giving a higher reading. I dont think the mods I have to the car will cause this problem. Also they threw the old fuel, cleaned tank, lines,throttle body and injectors, reset the ECM. The FE has come back I feel as per my guage reading have done approx 200km after service and have only gone down 1/4 tank from full. Pick up is not how it used to be and car feels very sluggish.

Please help as I desperately want the car to get back into the original condition.

Viper

BTW - they said that the clutch would not be replaced under warranty.
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Old 14th May 2006, 10:10   #2
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Quote:
[viper]
He said that at the speed of 60kmph in 5th gear the car should be doing approx 1600RPM whereas my car was doing approx 1900RPM. I confirmed this by driving 4 others Getz cars from their workshop and they all showed approx 1600RPM.
[/quote]

Have you checked with tyre size of other 4 getz were they same as yours?

Last edited by Ford Rocam : 14th May 2006 at 10:11.
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Old 14th May 2006, 10:14   #3
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Hi,

Yes they were all 14". My car is 195/60/14 and those were 175/60/14 or 185/60/14. I dont think larger tyres will cause this problem smaller ones maybe.

Viper
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Old 14th May 2006, 11:09   #4
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Well, tyre size has nothing to do with it. I thought i'd made it clear that nothing can change the speedo/tacho relation, unless tampered with or due to a faulty speedo cable.

Moreover, even if the clutch is slipping, it usually shows slip in the first 2 gears. When in 5th, there's hardly any load on the clutch since the engine rpm is relatively less at any give vehicle speed (compared to the other gears).

According to my formula, the Getz should be doing 62kmph (-2%) at 1900rpm in 5th. 1900 / 0.825 / 4.056 * 72.8 * 2.54 / 100000 * 60 = 62.99kmph.

At 1600rpm, the car is actually doing 53kmph (-2%).

I'd say your car's speedo is bang on, and there's no chance of a clutch slip.

Here are the ratios and the true speed registered by Vbox at 1000rpm in every gear (figures taken from Overdrive's road test)

Gear -- Gear Ratio -- Overall Ratio -- kmph/1000rpm
1st -- 3.615 -- 14.66 -- 7.37
2nd -- 1.950 -- 7.90 -- 13.67
3rd --1.370 -- 5.55 -- 19.46
4th --1.061 -- 4.30 -- 25.12
5th --0.825 -- 3.34 -- 32.34

Final Drive Ratio: 4.056

If the car is doing 32.34kmph at 1000rpm in 5th, at 1900rpm it shud be doing 32.34 * 1.900 = 61.44kmph (this is the actual speed recorded by Vbox)

So, you go and tell that guy, to get those other cars checked.

Shan2nu

Last edited by Shan2nu : 14th May 2006 at 11:15.
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Old 14th May 2006, 11:09   #5
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hi viper.....
i have had similar problems with adulterated fuel from gujarat when my car was there.....
as soon as i tanked up the engine noise changed....the ride became rough, and the response became sluggish.....fuel efficiency was not too affected and the entire running of the car was played havoc with....
once the dirty bugger enters the engine it takes a really long time to get rid of regardless of how many times you flush the engine or the injectors and even the throttle body......
it took me about 15 tankfulls(might be more) and almost about 8 months to the car back to normal and harness the same accleration and smoothness from the engine as new....
the problem is DEFINITELY NOT THE CLUTCH.....even if you drive like an absolute lunatic NO CAR CLUTCH FAILS OR SLIPS AT 7000km.....Hyundai is taking you for a ride and better not get fooled....what ARE they thinking...
i think you must show this same problem to a very reputed car garage in mumbai(where u stay) like chagganmittha at metro etc and speak to them about this.....let them check the car and if they diagnose anything other than the clutch(i bet my money on that) you must go hyundai and threaten to sue those imbeciles.....
my solution to this problem is an expensive one albeit one which is the fraction of the cost of the replacement of a clutch(frivolous!) that is the use of speed 97/power 97(any premium petrol with the highest octane rating) for at least 10 tankfuls(ouch.........you better exercise your foot........cos if its gonna be heavy your acountant might just kill you) and change the settings of your performance module to the least performance(the engine is very young and whats important is to relax the guy and not stress it too much with absolute wear and tear).....
one more thing.....STP makes something called a system purge.....make sure you add that to your fuel tank every 6 months to keep the tank and injectors all clean and healthy
then post your reports on this thread....
i think my solution even though a simple one is more logical and less far fetched than those korean fools....
plz correct me if i am wrong anyone who reads this....
KEEP REVVING
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Old 14th May 2006, 11:12   #6
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besides i just remembered that you have made some mods to the engine and manifold and that might be affecting the rpm(hyundai off course sets benchmarks for stock cars) and yours is modified
but i still stress......no clutch
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Old 14th May 2006, 12:30   #7
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Hi Frank,

To start with I am not someone you can fool or mess with. I know the clutch is not the culprit but want to isolate the fault. FYI I use Speed 97 for 80% of the times and mix of Speed 97 and 91 rest of the times.

The car is going back to the hyundai workshop tomorrow as the senior technician from Chennai wants to address the problem. Will keep you guys posted.

Viper
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Old 14th May 2006, 14:23   #8
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What seems to me that the engine is not producing enough torque and power as per specification.

It is producing the torque necessary to pull the car at 60 km/h at 5th gear in 1900 RPM instead of 1600 RPM.

I heard that using dynamometer, one can see exactly what power-torque the engine is producing at any RPM.

Poor fuel qualify may cause engine to perform poorly.
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Old 14th May 2006, 17:16   #9
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The first question to ask is ... Is the the RPM meter and the Speedo Meter Cable-driven or By-wire (Electronic)...
Becoz there might also be a problem with the electronics section where the engine pulse is used for the RPM meter..
Cheersss
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Old 14th May 2006, 17:55   #10
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If it helps viper, my indica tacho used to read 2000rpm at times, even though i knew the engine was just above idle. Get the wiring checked.

Drifter
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Old 14th May 2006, 22:47   #11
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Quote:
Originally Posted by viper

BTW - they said that the clutch would not be replaced under warranty.
Howcome ?!..does the User Manual specify clutch isn't considered as free replacement if at all there is some defect within the Manufacturers Warranty Period?
-sr
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Old 15th May 2006, 08:34   #12
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Hi,

He said clutch slippage does not come under warranty as it could be linked to driving style. Anyways they have not yet opened the clutch to check.

Viper
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Old 20th May 2006, 15:32   #13
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Hi Guys,

Update : The car is finally back from the service centre after 4 days. The funny part is the problem is solved but they do not know what caused it. They have changed the following

1> New Clutch/Pressure Plate Release Brg.
2> All new sensors - IAT, O2 MAP,TPS, etc
3> Fuel pump & filter.
4> ECM

All this was done absolutely free of cost inspite of my car being modded and kitted with 195/60/14 tyres, free flow exhaust, Iridium plug sand MSD wires, ported/polished head, enlarged throttle body and Tri-Phase Module as I proved to them that none of these mods caused my problem by swapping with OE parts.


Viper

Last edited by viper : 20th May 2006 at 15:33.
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Old 20th May 2006, 17:56   #14
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Viper, I am sure you are feeling a little discontented with not being able to find out the cause, but the fact that the car is now fine, is surely an effective pacifier.
Now you can go back to enjoying your driving in peace.
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Old 6th August 2009, 17:20   #15
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Default Engine RPM For Honda city zx

Hello There,
Well just two days back I have graduated from 2004 esteem lxi to Pre owned 2006 Honda city ZX GXI. I would like to know what is the actual rpm when we do 120 kmph in a Honda city. In my esteem when I used to do 120kmph the rpm was around 3000 rpm. In Honda city at 120kmph the rpm is 3600. Is it because gear ratios are different or could it be the clutch slip. The vehicle has done 31000 kms now. I would appreciate if some one show some light on the RPM of different cars at different speed say at 80,100,120 so that we can cross check if there is a clutch problem. Most of the manuals or the technical data only let us know about the torque at the rpm and not the speed and the rpm sync.

Last edited by Jaggu : 6th August 2009 at 17:58. Reason: Please use search before opening a new thread, Thanks
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