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View Poll Results: Is above 4k rpm useless for regular driving?
Agree 76 54.68%
Disgree 22 15.83%
Depends on the situation 39 28.06%
Dont know 2 1.44%
Voters: 139. You may not vote on this poll

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Old 14th March 2011, 10:19   #16
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

Yes. I strongly agree to that one.
I remember TD of the Beat when it was launched(for a friend).
I knew that the max power came in around 6.5k with the max torque around 4.5k rpms. Asked the sales guy if I could rev the car, he nodded and I did. The result was my co-passenger (the tentative buyer) gave a scream, the SAs were ash faced because we were redlining on Bannerghatta Road(Dairy Circle) at 5 pm. What is the use of having the push and the power so high up that a regular guy will never be able to use it without scaring the bejesus out of people!
The Fabia felt much more easier to drive with the torque peaking at 3k rpm which is ideal for a city puttering.
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Old 14th March 2011, 10:34   #17
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

This is the one point that I always wanted to discuss,

Peak Torque coming in 4.5K makes no common sense.

I guess for all the new potential buyers, they should be looking at at what RPM peak torque is delivered and at what RPM all the horses are unleashed.

Look at the Diesel figures all the diesel cars have peak torques in the region of 1500 - 2500 RPM which makes the in gear acceleration really nice and fun to drive.

For petrol cars look at these figures:

Santro - Peak torque at 3000 RPM - best in city driving, the in gear acceleation is far better than my Swift P.

Etios - Again peak torque at 3000 RPM, stunning in gear timings.

Fiesta P - Peak torque at 3400 RPM - Fun to drive car.

Basically, peak torques and peak BHP being delivered at highish RPM makes no sense because they are not achievable.

I guess no one here has touched 5500 RPM mark on the highest gear.

Happy Motoring.
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Old 14th March 2011, 10:48   #18
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

Quote:
Originally Posted by DicKy View Post
Looked up at wikipedia.
Looks like my WagonR deserves it as it's being used sparingly and that too at low speeds.
Also read in a ' car maintenance ' that came with an old ACI that one had to make the car stretch it's legs once in a while.
But one doubt 'gurus'- does mpfi engines need this treatment?
It is highly recommended to drive your car at high revs at least once a month. It will free up your engine and you can notice that your engine will respond better to throttle inputs. There is no need to drive for hundreds of KMs for this. Just a short round of 20 to 30 KMs of high speed driving reaching the higher revs in all gears is sufficient.
It is even more important in an MPFi engines as the ECM will adjust itself for a relaxed nature of driving and when you need the power to overtake, you will find yourself struggling.

I make a occasional high speed run between Bangalore and Mysore whenever I feel my car has lost its response. After the run one can notice the difference in engine smoothness and sound.

I recall driving my friend's Punto MJD which had around 13K on the ODO. My friend has never revved past the 3K rpm mark and the car feels so sluggish and slow. I tested it on the highway and it took ages to reach 100 and it struggled to go past 120Kmph.
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Old 14th March 2011, 12:53   #19
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

Thanks @speedmeister for the advice. So the ECU adapts itself to the driving style.?
No wonder the engine doesn't respond freely whenever the situation demands.
Now know the reason (as well as the solution.)
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Old 14th March 2011, 13:33   #20
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Even i have experienced this phenomenon in my i20.when the car was a week old we took it on a long trip and it used to touch 140 easily.but after a month or two of sedate b2b traffic i tried to push it again and it had lost all the punch it had previously.so redlining once in a week is like a tonic to the cars.alternatively you could disconnect the battery terminals for 15 minutes.this will reset the ecu settings and the car will be good as before
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Old 14th March 2011, 14:11   #21
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

I drive my i10 irde and my colleague's i10 kappa on alternate weeks (because of car pooling). My colleague doesn't drive, hence I get the opportunity to drive her car too.

The irde engine was a very good bottom end and delivers good torque at low RPMs. On the other hand, the kappa engine is dead below 1700 RPM and needs to be revved hard to extract its power.

My colleague doesn't know much about cars. I am sure that she feels that I drive my car (i10 irde) in a sedate manner (low RPMs) and her car (i10 kappa) like a maniac (high RPMs).

Again, while performing an overtaking, irde feels so much better as it doesn't require any downshifting - just press the gas pedal and enjoy the acceleration. Whereas in the kappa engine, one has to be in the right gear at all times and always keep the engine on boil.

For city driving, I vote for engines with better bottom range and mid range.

Rohan
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Old 14th March 2011, 14:24   #22
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

Quote:
Originally Posted by gemithomas View Post
You should drive a FIAT 1.6 Engine to know what it really feels to be at >4K RPM.
I'm sure you'll never settle for anything less
You said it Gemi! What an addictive thing it is.

I agree with threadstarter - even a lot of fast drivers don't use (enjoy) the upper 4K band. Their style is to achieve a high speed by lugging engine through the gears and then keep up the speed! This is something which is done by bus drivers, come on!

But in regular driving, you can drive a whole lot better if you start using the upper band of ~4K in situations like overtaking, get ahead of the slow pile of bikers and other cars from a traffic signal, gain speed after entering a highway in order not to disturb the vehicles coming behind you etc.

I'll put it in a general way: Indian drivers (well , most of them) don't know how to accelerate properly & Don't know how to overtake safely. All are unnecessarily worried about the fuel consumption. They drive as if there's an egg kept under the gas pedal.

I often exceed 4K rpms in my car. Not all the time, but when situation demands it. I get an FE of 13+ kmpl in city with my 5 year old 1.2L petrol engine pulling a 1 ton car.

City cars like Santro are not gonna give you a good FE if you often peek to the other side of 4K rpm. They are tuned to the lower band, and they will give you good FE ONLY if you drive in that region, by shifting ever before the engine has some decent revs that it deserves!

Last edited by clevermax : 14th March 2011 at 14:39.
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Old 14th March 2011, 15:20   #23
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

Quote:
my dumb phone browser is being cranky
You called?

I've never had a car that has not been revved. I consider 4k a decent rev range for urban driving - with 3K being where the car is mostly driven. If you have a newer car with an instantaneous FE reading, the car does not worse at steady 4K than it does at steady 2K with the engine just ticking over. The only thing that really drops the FE drastically is acceleration, once the engine is at a constant speed the consumption is similar. Unfortunately in a city like Gurgaon with a short hop between work and home means I can't put some figures down for you.

Consider that I have a brand new car, and have already hit 4K twice or so (less than 150 kms on odo). The difference is that I don't use it for more than a few seconds to knock the slower bits into shape. My Opel lived a large part of its life above 5K, and I loved the sound. One of my favorite tracks
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Old 14th March 2011, 15:24   #24
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

One query in my mind to share with mates

If an engine is running at 2500 RPM (say) and for a given engine the C.C is fixed and more or less the air/fuel ratio is also constant (to a large extent) implies that for each cyle it consume a fixed amount of fuel.

So, can we deduce for the constant RPM (say 2500) the engine shall consume equal amount of fuel irrespective of the gear engaged ? per hour.

Can we ??

please clear my doubts
thanx

Cheers
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Old 14th March 2011, 16:45   #25
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

It's not that simple. You have to factor in the position of the has pedal. Fuel consumption works in this way AFAIK. Disclaimer is that i'm not an expert and that an expect correction/addition would be most appreciated.

1. The throttle, in other words, the accelerator pedal or gas pedal. Everything depends on this. In a gasoline engine, the throttle controlls the amount of airflow into the engine and that's all it does. You do not directly influence the fuel consumption using the throttle. That's the job of the ecu.

2. The ecu.
In a modern ecu controlled engine, the ecu has control over the amount of fuel injected into the engine. It does this according to the airflow into the engine. This is important as there as two ingredients required for fuel to burn - oxygen (from air) and fuel. This is a crucial step as if amount of fuel injected is much higher than the available oxygen, then you get black smoke from the exhaust full of carbon, carbon dioxide and carbon monoxide. And if there's too much air, pollutants like the oxides of nitrogen go up. So, how exactly does the ecu do this?
There are sensors called O2 sensors in the engine. They measure the amount of oxygen flowing into the engine. They feed this information to the ecu which then calculates the requisite amount of fuel and feeds that much into the engine.

So, the sequence of events is as follows-
1. You depress the throttle.
2. The airflow into the engine increases.
3. The o2 sensors detect this and feed the information to the ecu.
4. The ecu calculates the requisite amount of fuel and feeds that much.
5. Stronger combustion causes the cylinders to move faster and increases the rpm.
6. The increased rpm is transmitted as torque through the gearbox which multiplies torque depending on the gear ratio.

So, does rpm play a part? I honestly don't know. I've heard some opinions on this but as long as i don't understand the physics behind the opinions, it's hard for me to believe the theory.

So, the fe you get depends on a lot of factors. This also explains why fe drops suddenly when you accelerate but climbs up again when you are moving at a constant speed. All in the pedal position.
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Old 14th March 2011, 16:52   #26
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

Quote:
Originally Posted by AVR View Post
I read somewhere that its advisable to rev it hard every few weeks just to keep the engine in good shape. Google "Italian tuneup"
Thanks AVR, Yup, I've come across that earlier here in team-bhp. Now my question is, will it harm my engine if I haven't done it often in the past ,say for years, but suddenly now decide to revv hard henceforth? Like the other posts suggest, will the ECU adapt itself to the new driving style, maybe after a few hundred kilometers?


Can all cars' ECU be re-tuned to have more lower and mid grunt (at the cost of top-end) ? If so, why don't we see people (who drive mainly in the city) going for that re-tune? Why don't manufacturers provide a stock option to switch between the two styles on the fly? Is it impractical?
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Old 14th March 2011, 16:57   #27
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

@ nukeblitz

I know it can not be that simple that is why i am in doubts.

But still to understand it better

The moment you step on gas pedal >airflow increase >etc. > > increase in RPM

so to maintain the constant RPM gas pedal is relieved. so the net net is back to square one

T-Bhp mates help us know more

Cheers
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Old 14th March 2011, 17:09   #28
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

Quote:
Originally Posted by sanagg1 View Post
so to maintain the constant RPM gas pedal is relieved. so the net net is back to square one
Gas pedal can be at different positions when engine rpm is the same in the same gear.

Example:

- You are driving on a horizontal surface in 4th gear with a light foot on gas, engine relaxing at 2500 rpm.
- You are driving up on a slight incline with heavy load in 4th gear, gas pedal pushed to the floor, engine lugging at 2500 rpm.

The second case will waste more fuel than the first. Hence, same gear, same rpm, no constant fuel consumption!


Quote:
Originally Posted by sanagg1 View Post
The moment you step on gas pedal >airflow increase >etc. > > increase in RPM
It can happen mostly when you are in neutral gear, but not in another gear under load. It will take some time for the rpm to climb up depending upon the load & power band of the engine.

Last edited by clevermax : 14th March 2011 at 17:15.
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Old 14th March 2011, 18:13   #29
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

Enjoy!

Horsepower vs torque

Torque and Power
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Old 14th March 2011, 18:30   #30
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Default Re: Debate: >4k rpm band useless for regular driving and for regular joe drivers

Quote:
Originally Posted by LNK View Post
Alright, here's a mildly related question I have. I'd posted it elsewhere but no response.

If an engine is not revved high for a long time, say for years, does the engine lose its potential by an amount? Like, if the car's always been driven around at <3.5k rpm, will it be an issue if all of a sudden I push it and maintain it at 4.5k or higher? In short, do engines get lazy like humans?
If the engine is driven sedately for a long time the following happens as the engine does not heat up to its optimum temparature
1. Carbon deposits on the valves and exhaust
2. Deposits on the injector
3. Acids in the engine oil.

Once the engine is revved up and driven for some time, the deposits normally burn up and the acids in the engine oil evaporate. That is why after a longish trip of say 100km+, or after spirited driving at 120+ for 20km the engine feels different with an aggressive growl as well as excellent throttle response.

Quote:
Originally Posted by nukeblitz View Post
Exactly, in the city low end torque is god. Even on the highway, it's midrange that's used by most people. Very few people use the high end even on the highways. Now we know that revving to the redline (post run in, of course) is usually the way to go to extract the most out of the engine and even if we don't do it all the time, situations like overtaking with incoming traffic might call for something like that and we wouldn't be afraid to do so.
I use the engine RPM to the hilt while overtaking. In city I often do 100 in second for that fast overtaking and then back to fourth or fifth. Similarly on highways, especially on crowded ones, you have extremely short window for overtaking. Take the car to second at fifty/sixty, rev it to 100 and you have completed the maneuver in a jiffy. On advantage of overtaking in second is that there is enough engine braking power to abort without excessive braking. I have been doing this in my Estem MPFI in past and now in the Alto K10.

Quote:
Originally Posted by sanagg1 View Post
One query in my mind to share with mates

If an engine is running at 2500 RPM (say) and for a given engine the C.C is fixed and more or less the air/fuel ratio is also constant (to a large extent) implies that for each cyle it consume a fixed amount of fuel.

So, can we deduce for the constant RPM (say 2500) the engine shall consume equal amount of fuel irrespective of the gear engaged ? per hour.

Can we ??

please clear my doubts
thanx

Cheers
As I understand it you are saying that for the same CC at the same RPM the FE should be same?

Well it is not that at all. All engines are designed for a specific power output and consume fuel accordingly. Thus one 1000 cc engine may be designed for pottering around, so it will have lower power hence lower fuel consumption at all RPM. Contrast this to a high performance engine, again of 1000cc but designed to give three times the power compared to the other engine. This engine would consume more fuel at all the RPM, apart from being higher revving unit, it may deliver more torque also.

The air-to-fuel ration may be constant, but the sheer quantity of air gulped by a performance engine is much more compared to a normal engine. In carburetor days you could see the large throat of performance carbs and the oversized air filters to appreciate the quantum of air gulped!

Quote:
Originally Posted by clevermax View Post
Gas pedal can be at different positions when engine rpm is the same in the same gear.

Example:

- You are driving on a horizontal surface in 4th gear with a light foot on gas, engine relaxing at 2500 rpm.
- You are driving up on a slight incline with heavy load in 4th gear, gas pedal pushed to the floor, engine lugging at 2500 rpm.

The second case will waste more fuel than the first. Hence, same gear, same rpm, no constant fuel consumption!

It can happen mostly when you are in neutral gear, but not in another gear under load. It will take some time for the rpm to climb up depending upon the load & power band of the engine.
The position of the gas pedal normally indicates how much fuel you are allowing the engine to use. Under light load you require less fuel to keep a particular speed (RPM), while under heavy load the engine requires more fuel to maintain the same speed. I think that with more fuel you are increasing the torque; which is required to move the load; while with less load, as in the case of coming down the hill, you need less torque, hence less fuel, to maintain the same speed.
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