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Originally Posted by LNK 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.
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Originally Posted by nukeblitz 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.
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Originally Posted by sanagg1 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!
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Originally Posted by clevermax 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.