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Old 8th February 2011, 19:43   #1
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Default RPM shoots up when changing gears

On my recent trip along the Konkan coast, my friend noticed something while driving...

Whenever you shift gears, the rpm goes a bit high!

I mean:
You are at 1300 rpm and press clutch (to change,say, from 1st to 2nd), the rpm goes to 1400-1500 rpm while you are changing!

Advantage:
You don't loose torque while gear shifts. You have revved your car to 2000 rpm and you change gears so that you can achieve higher speeds. Howver, the engine looses rpm during change (say to 1500 rpm) and hence, you will have to again rev all the way up!

This means, you will have to wait for acceleration\power in the new gear.

Has any of the 1.6 S users noticed this?
How about the other Fiestas?

I'm not sure how much of a plus this is quantitatively, but it certainly it gives a good feeling while drive!
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Old 9th February 2011, 11:40   #2
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Default re: RPM shoots up when changing gears

lambdaplus - how many km your car has run? what is the year of your car and how old? Is it on cold start only or also after driving for some time?

STILL - I dont think this is an intended behaviour in any car.

Possibly the clutch could be culprit sometimes (potentially a symptom of clutch slipping)

Also read through the similar thread for other possibilities for this behaviour:
http://www.team-bhp.com/forum/techni...depressed.html (RPM shoots up when clutch depressed)

Mods - I would also request if this can merge with the above thread - if suitable!
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Old 9th February 2011, 12:01   #3
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Default re: RPM shoots up when changing gears

1300 RPM is very less (that too on a Petrol) to change gears. Maybe you were climbing a gradient when changing gear so the ECU had to step in to increase RPM so that the car does not stall.
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Old 9th February 2011, 12:47   #4
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Default re: RPM shoots up when changing gears

Why are you shifting at 1300 rpm. IIRC that is the idling rpm for a Fiesta 1.6S. The correct rpm for gear shifts in a Fiesta 1.6S is 3000 rpm. That way by the time you are finished changing gears, the rpm stays above 2000 rpm which is perfect for pulling away in any gear.
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Old 9th February 2011, 12:48   #5
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Default re: RPM shoots up when changing gears

Quote:
Originally Posted by DWind View Post
1300 RPM is very less (that too on a Petrol) to change gears. Maybe you were climbing a gradient when changing gear so the ECU had to step in to increase RPM so that the car does not stall.
I am curious to know what is the ideal RPM range to shift gears
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Old 9th February 2011, 13:02   #6
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Default re: RPM shoots up when changing gears

Quote:
Originally Posted by aravinrd View Post
I am curious to know what is the ideal RPM range to shift gears
IMO for the Fiesta 1,6S, it's between 2k - 3k, 3K being the ideal sweet spot to enjoy the torque and power band of the engine, and 2-2.5k for sedate driving. Rev it beyond 3k to really take-off with head-pinned-to-headrest kind of acceleration, if you know what I mean.

Of course, this is just my opinion after driving the Fiesta 1.6S daily for the last 4 months.
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Old 9th February 2011, 14:16   #7
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Default re: RPM shoots up when changing gears

Quote:
Originally Posted by lambdaplus View Post
I mean:
You are at 1300 rpm and press clutch (to change,say, from 1st to 2nd), the rpm goes to 1400-1500 rpm while you are changing!
Why would someone want to change gears at 1.3 k on a Fiesta S. .

On a serious note. I assume you were on a super relaxed mode. Well, sometimes on the highways, whist on a relaxed mode, some don't take their foot off the accelerator completely while changing gears. Even a slight pressure can increase the revs. Please check if this happens even when you take your foot completely off the throttle.

Quote:
Originally Posted by aravinrd View Post
I am curious to know what is the ideal RPM range to shift gears
The ideal RPM range cannot be generalized for all cars. It is car specific. However, for Fiesta, for sedate driving, 2.5 k should be perfect, may be 3k on the highways, to get moving.

If on a spirited mode, the ECU will take care of limiting the revvs.

Quote:
Originally Posted by Neilguy View Post
IIRC that is the idling rpm for a Fiesta 1.6S.
I doubt so. I believe its 900 +/- 20 .
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Old 9th February 2011, 14:44   #8
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Default re: RPM shoots up when changing gears

Quote:
Originally Posted by dhanushs View Post
I doubt so. I believe its 900 +/- 20 .
+1. It's 900 without a/c and 950-1k with ac. Idling at 1.3k is high. I think Dhanush might be right about the accelerator pedal being slightly depressed. It is not normal behaviour for the rpm to shoot up when the clutch is depressed.

Last edited by niranjanrvce : 9th February 2011 at 14:46.
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Old 9th February 2011, 14:45   #9
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Default re: RPM shoots up when changing gears

hydraulic clutch and the engine needs those 100 revs ? like in a hydraulic power steering at idle?
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Old 9th February 2011, 15:25   #10
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Default re: RPM shoots up when changing gears

Quote:
Originally Posted by paras211 View Post
hydraulic clutch and the engine needs those 100 revs ? like in a hydraulic power steering at idle?

Why would hydraulic clutch need revs from engine?
Power steering needs engine because it uses engine power to provide the assist. Hydraulic clutch is just a combination of two cylinders that transmit force from your leg to clutch bearing.it works just fine even when eng
ine is switched off.
And why would ecu increase rpm while gear change,there is just no logic to do so. As soon as higher gear is engaged ,rpm will be force to come to much lower value as compared to previous gear.
New rpm is governed by gear ratios between the two gears and speed of vehicle while gears are beeing changed.
Increasing rpm while shifting will only put more stress on clutch and waste fuel.
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Old 9th February 2011, 17:01   #11
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Default re: RPM shoots up when changing gears

This is a known side-effect of some cars with drive by wire accelerators; the Fiesta has one, correct? It's called "revv hang". You'll see it a lot more when the car is hot (explains why your friend noticed it on a long drive). Relax, just takes a little getting used to. Think of it as manual revv-matching
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Old 9th February 2011, 17:16   #12
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Smile re: RPM shoots up when changing gears

1300 is not the correct figure for changing the gears in a Fiesta atleast the normal variant. I generally find shifting gears at 1800 rpm the most ideal. For an S it should be higher than that since the engine is tuned different from normal variants.

I have never seen the rpm shoot up during the gear change, maybe your foot is on the accelarator pedal duing the gear shifting. If so you are damaging the clutch pads.
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Old 9th February 2011, 19:33   #13
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Default re: RPM shoots up when changing gears

I've noticed this in the Civic as well. I normally shift around 1900 rpm and while changing gears it rises to around 2000 rpm.
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Old 9th February 2011, 20:08   #14
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Default re: RPM shoots up when changing gears

Quote:
Why would hydraulic clutch need revs from engine?
Power steering needs engine because it uses engine power to provide the assist. Hydraulic clutch is just a combination of two cylinders that transmit force from your leg to clutch bearing.it works just fine even when eng
ine is switched off.
And why would ecu increase rpm while gear change,there is just no logic to do so. As soon as higher gear is engaged ,rpm will be force to come to much lower value as compared to previous gear.
New rpm is governed by gear ratios between the two gears and speed of vehicle while gears are beeing changed.
Increasing rpm while shifting will only put more stress on clutch and waste fuel\
ty it was just a wild guess, never really pondered over the workings of a clutch , now i know.
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Old 9th February 2011, 22:20   #15
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Default re: RPM shoots up when changing gears

Quote:
Originally Posted by GTO View Post
This is a known side-effect of some cars with drive by wire accelerators; the Fiesta has one, correct? It's called "revv hang". You'll see it a lot more when the car is hot (explains why your friend noticed it on a long drive). Relax, just takes a little getting used to. Think of it as manual revv-matching
Exactly.
Its a lag. You may pull the feet of the pedal but the throttle closes after a while. Maybe a faster microprocessor/ECU can rectify.
I have a feeling that this is not good for engine braking.
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