Perfect gear changes - Team-BHP

satish_appasani · 19th July 2005, 01:06

Today while driving home from work, I was wondering how people use tachometer for perfect gear changes and decided to give it a try.

BTW, my car is Palio D and trying to use it's great torque at low rpm to move around in city. I really did not understand how to use tacho but got a little bit in sync with the speedo. Start in 1st and them immediately move to second. Just when reaching 20 KMPH move to third and after 30 KMPH, it's 4th gear. As soon as speedo crosses 40KMPH and nobody is blocking in the front, move to fifth. This almost worked for me including when down shifting. When I followed these speeds to shift the gears, i felt a very smooth gear change.

Now, i don't understand how to make use of RPM during gear changes. when shifting towards higher gear, i acclerate to between 2000-3000 and shift the gear. My car keeps running in 4th gear even at 1000 RPM. Well, I think the car is supposed to run in low rpm when in top gear, right?

Can the pros please throw some light on my poor knowledge?

v1p3r · 19th July 2005, 02:08

Palio D, I suppose you could shift up at even slightly less than 1000rpm. The inherent low-end torque of a diesel engine would help there.

The easiest way to use the tacho is to notice what rpm you're shifting up at, when you shift according to the speedo. Normally, it would be a similar value from any one lower gear to the next higher gear.

In the Baleno, it is possible to shift up at 1500rpm, which is pretty low for a petrol car. It actually goes lower, to 1200 or so, but I use 1500 as a benchmark. This is possible because, for a petrol, the Baleno has useful torque low down.

Shifting up at speedo intervals will never paint as clear a picture as shifting up at tacho intervals. But please take care not to shift down at high tacho speeds, or you may have an over-rev and cause major damage.

turbo_lover · 19th July 2005, 02:30

Quote:

Now, i don't understand how to make use of RPM during gear changes. when shifting towards higher gear, i acclerate to between 2000-3000 and shift the gear. My car keeps running in 4th gear even at 1000 RPM. Well, I think the car is supposed to run in low rpm when in top gear, right?

each time you shift up your engine speed falls by 900 to 1200rpm per shift ...each time you shift down your revs increase by the same amount ...hence downshifting 2 gears at 3000RPM will pull your revs to somewhere in the 5000rom region..

v1p3r · 19th July 2005, 10:05

Hey turbo, where did you arrive at the rpm loss/gain figure? It increases or decreases substantially, depending on initial rpm. eg if I shift into 5th from 4th, at 2000rpm, I may lose only 5000 rpm. But from 2nd to 3rd at 6500rpm, I lose a full 2500rpm. Same applies to downshifts as well.

RX135 · 19th July 2005, 12:38

There can be no fixed rule about which RPM you should shift. It would depend on your car *and* on the gear ratios. For lower gears (1 to 2 and 2 to 3), you can shift in between 1000 rpm-1500 rpm, for 4-5, it would be 1500-2000 rpm band. You will be the best judge for your car. Basically try to find an RPM for each gear, such that *after* shifting to higher gear, RPM does not drop to the level of knocking/stalling.

turbo_lover · 19th July 2005, 12:41

Quote:

Hey turbo, where did you arrive at the rpm loss/gain figure? It increases or decreases substantially

yeah dude..

but looking at the range satish shifts at i.e 2000-3000 one would expect 900 to 1200 change in rpm wouldnt he?
if he shifts from 1000 rpm in 4th down to 2nd gear his rev's will hit atleast 3500 rpm on the tacho,the case is different if he is shifting up/down at higher revs ..this is what i have noticed ...
correct me if i am wrong ...
cheers

turbo_lover · 19th July 2005, 12:44

Quote:

Originally Posted by RX135

, RPM does not drop to the level of knocking/stalling.

which Satish for your knowledge should be when the tacho falls a bit below 1000rpm...in which case you shift down to increase the engine speed which should rise up by 500 aproxx per downshift ...

RX135 · 19th July 2005, 12:50

Quote:

Originally Posted by turbo_lover

for your knowledge should be when the tacho falls a bit below 1000rpm.

Roughly yes, but not that I fully agree. It *may* stall at higher RPM as well if you are in 5th gear, since the torque at wheels would be lesser than if you are in 2nd. (Normally wont happen since you would downshift, but in case of sharp braking, it may be distinct possibility).

GTO · 19th July 2005, 12:55

Quote:

Now, i don't understand how to make use of RPM during gear changes. when shifting towards higher gear, i acclerate to between 2000-3000 and shift the gear. My car keeps running in 4th gear even at 1000 RPM. Well, I think the car is supposed to run in low rpm when in top gear, right?
Can the pros please throw some light on my poor knowledge?

Theres only one way to shift, and its redlining all the way!

Just kidding. As RX said, the ideal shift point would vary from car to car. But do make sure not to stress the engine by running in a higher gear at an extremely low rpm.

GTO

turbo_lover · 19th July 2005, 13:29

Quote:

Originally Posted by RX135

(Normally wont happen since you would downshift, but in case of sharp braking, it may be distinct possibility).

yeap..in which case you downshift or engage the clutch to prevent the car from stalling ..

vivaid · 19th July 2005, 14:15

Since on this topic.... is there something like an ideal RPM ..... I generally drive my car at an average of 2000 RPM... while i read of about redlining so frequently out here....

I also notice that the control over the car in an important factor at high rpms... as in the response from the engine to an accelaration or deceleration is higher than at lower rpms... (there cud be a better term to explain this....)

FE to i would assume would be impacted by high RPMs and a a lower RPM on higher gears could damage ur engine(as i read from the posts below)

Hence the question.. is there something called an ideal RPM also.. whats the average RPM that u guys generally drive at?

karthik247 · 19th July 2005, 15:58

Guys while doing really slow speeds in higher gears means u'll have to use the clutch very often, which will be bad for the car. Engine knocking is also a problem if it occurs often. Isn't it best to just downshift instead of waiting so long.

turbo_lover · 19th July 2005, 16:00

yes ofcourse ...
downshift the moment the speed is too low for the gear to pull the car ...

v1p3r · 19th July 2005, 20:34

turbo, ideally this would all depend on the gear ratios of the car in question. I'm afraid I don't know them for the Palio D, so I can't authoritatively comment as such. But you seem to be on the right track!

Xsailor · 19th July 2005, 23:39

By the way, this Engine knocking - the ghad-ghad which one hears if driving or picking-up in a high gear - why does it happen?

Is is that the car wheels are moving at a lower speed than the engine gear (or something similar - just like in a Diesel Genset if the revs get too low, the gene starts to motor i.e. the alternator drives the flywheel rather than the other way).

Pardon my ignorance on matter technical, this is just a wild guess - Please enlighten further.

Cheers

19th July 2005, 01:06	#1 (permalink)
satish_appasani BHPian Join Date: Jun 2004 Location: Hyderabad Posts: 918 View My Garage	Perfect gear changes Today while driving home from work, I was wondering how people use tachometer for perfect gear changes and decided to give it a try. BTW, my car is Palio D and trying to use it's great torque at low rpm to move around in city. I really did not understand how to use tacho but got a little bit in sync with the speedo. Start in 1st and them immediately move to second. Just when reaching 20 KMPH move to third and after 30 KMPH, it's 4th gear. As soon as speedo crosses 40KMPH and nobody is blocking in the front, move to fifth. This almost worked for me including when down shifting. When I followed these speeds to shift the gears, i felt a very smooth gear change. Now, i don't understand how to make use of RPM during gear changes. when shifting towards higher gear, i acclerate to between 2000-3000 and shift the gear. My car keeps running in 4th gear even at 1000 RPM. Well, I think the car is supposed to run in low rpm when in top gear, right? Can the pros please throw some light on my poor knowledge?

19th July 2005, 02:08	#2 (permalink)
v1p3r Senior - BHPian Join Date: Feb 2005 Location: BLR - chasing cars... Posts: 4,056 View My Garage	Palio D, I suppose you could shift up at even slightly less than 1000rpm. The inherent low-end torque of a diesel engine would help there. The easiest way to use the tacho is to notice what rpm you're shifting up at, when you shift according to the speedo. Normally, it would be a similar value from any one lower gear to the next higher gear. In the Baleno, it is possible to shift up at 1500rpm, which is pretty low for a petrol car. It actually goes lower, to 1200 or so, but I use 1500 as a benchmark. This is possible because, for a petrol, the Baleno has useful torque low down. Shifting up at speedo intervals will never paint as clear a picture as shifting up at tacho intervals. But please take care not to shift down at high tacho speeds, or you may have an over-rev and cause major damage. __________________ *Singh is king?! He's a bloody baadshah!*

19th July 2005, 10:05	#4 (permalink)
v1p3r Senior - BHPian Join Date: Feb 2005 Location: BLR - chasing cars... Posts: 4,056 View My Garage	Hey turbo, where did you arrive at the rpm loss/gain figure? It increases or decreases substantially, depending on initial rpm. eg if I shift into 5th from 4th, at 2000rpm, I may lose only 5000 rpm. But from 2nd to 3rd at 6500rpm, I lose a full 2500rpm. Same applies to downshifts as well. __________________ *Singh is king?! He's a bloody baadshah!*

19th July 2005, 12:38	#5 (permalink)
RX135 Senior - BHPian Join Date: Dec 2004 Location: pune Posts: 1,557	There can be no fixed rule about which RPM you should shift. It would depend on your car and on the gear ratios. For lower gears (1 to 2 and 2 to 3), you can shift in between 1000 rpm-1500 rpm, for 4-5, it would be 1500-2000 rpm band. You will be the best judge for your car. Basically try to find an RPM for each gear, such that after shifting to higher gear, RPM does not drop to the level of knocking/stalling. __________________ Drive fast, but drive safe.

19th July 2005, 15:58	#12 (permalink)
karthik247 Senior - BHPian Join Date: Feb 2005 Location: TVM Posts: 2,290 View My Garage	Guys while doing really slow speeds in higher gears means u'll have to use the clutch very often, which will be bad for the car. Engine knocking is also a problem if it occurs often. Isn't it best to just downshift instead of waiting so long. __________________ Slow and steady wins the race... But there is nothing like a 300kmph dash to the line!!

19th July 2005, 14:15	#11 (permalink)
vivaid BHPian Join Date: Dec 2004 Location: Mumbai Posts: 67	Since on this topic.... is there something like an ideal RPM ..... I generally drive my car at an average of 2000 RPM... while i read of about redlining so frequently out here.... I also notice that the control over the car in an important factor at high rpms... as in the response from the engine to an accelaration or deceleration is higher than at lower rpms... (there cud be a better term to explain this....) FE to i would assume would be impacted by high RPMs and a a lower RPM on higher gears could damage ur engine(as i read from the posts below) Hence the question.. is there something called an ideal RPM also.. whats the average RPM that u guys generally drive at?

19th July 2005, 16:00	#13 (permalink)
turbo_lover Senior - BHPian Join Date: Dec 2004 Location: Windsor Posts: 1,339	yes ofcourse ... downshift the moment the speed is too low for the gear to pull the car ... __________________ Every weapon needs a master

19th July 2005, 20:34	#14 (permalink)
v1p3r Senior - BHPian Join Date: Feb 2005 Location: BLR - chasing cars... Posts: 4,056 View My Garage	turbo, ideally this would all depend on the gear ratios of the car in question. I'm afraid I don't know them for the Palio D, so I can't authoritatively comment as such. But you seem to be on the right track! __________________ *Singh is king?! He's a bloody baadshah!*

19th July 2005, 23:39	#15 (permalink)
Xsailor BHPian Join Date: Jun 2005 Location: Noida Posts: 122	By the way, this Engine knocking - the ghad-ghad which one hears if driving or picking-up in a high gear - why does it happen? Is is that the car wheels are moving at a lower speed than the engine gear (or something similar - just like in a Diesel Genset if the revs get too low, the gene starts to motor i.e. the alternator drives the flywheel rather than the other way). Pardon my ignorance on matter technical, this is just a wild guess - Please enlighten further. Cheers __________________ Lt.Col.Frank Slade: You're in no position disagree with me, boy. I got a loaded .45 here. You got pimples.

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