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17

What does the power at different rpm mean? Does it mean Car 1 has better power than Car 2 because it is at lower rpm? It depends. Or does the rpm not affect the power comparison? tl;dr: The rpm of the power peak affects the engine's usability for different applications. The "peak power" number is just one point on the power band of the engine. ...


15

Ok, let's start from the same picture so we're on the same page: These engines are four stroke engines, which means the piston goes up and down a total of 4 times, twice up, and twice down for each cycle. So to answer your questions: Of course I do realize it stands for revolutions per minute, but revolutions of what? As you stated later, it's ...


14

While i'm not sure if there are mechanical tachometers like speedometers electronic tachometers are quite simple. An electronic tachometer works like an old analog volt meter. The speed of the engine is converted to a voltage. The voltage is fed to the moving coil. The coil creates a magnetic field. That field of the coil tries to align itself with the ...


10

It all depends on your definition of high. In my car, the red line is at 7500 rpm, and that indicates that driving with the revs over this line for anything other than brief periods is expected to cause damage, either through overheating, increased wear, increased loading on bearings, lack of sufficient oil/fluid flow etc. When driving I have to keep my ...


10

Traditional rev limiters work by controlling the ignition and/or fuel. Ignition Control Retarding the spark (smoother) Completely cutting the spark (more aggressive) Fuel Control - Amount of fuel thrown in is controlled. This is used very carefully as effects of running lean at such high RPM can be detrimental to the engine health. In fact, lot ...


10

In Short its based on low burn rate of diesel plus the longer stroke of the diesel engine. First you must understand the difference between these engines, the diesel works on purely compression of fuel , heating and generating bang to produce power, the gasoline on the other hand is natively twitchy and needs a spark to explode and produce power on its own. ...


9

You have a few options out there. There are meters that clip onto the ignition system that show the engine RPMs that are quite simple and cheap: Tach meter at Amazon for example... You can also pick up a "timing light" that has a tachometer function. Either of these tools have other purposes for a shade tree mechanic, so find one that you think you ...


8

Although automated manuals are becoming more popular, the 2012 Civic (from my 2 seconds of searching) appears to be a normal automatic. Even still, I'm guessing your vehicle may have the sensors and programming necessary to determine that it's descending an incline and is employing engine braking to help you slow down. What it sounds like it's doing is ...


7

Idle speed is limited by the weight of the flywheel. A heavier flywheel allows for lower RPM idling and vice versa. If the flywheel is too light, it doesn't have enough inertia to keep the engine turning when you're not using the accelerator pedal. But if the flywheel is too heavy, the car won't accelerate fast enough. At 540 to 1000RPM idle speeds, you can ...


7

To answer your question, no it isn't bad for your car to keep it in as high a gear as you can while still maintaining speed. As long as you are above idle in RPM and your engine isn't lugging, you aren't doing any damage. See this link for more information about lugging. You mentioned that you might do this to be quieter and for fuel efficiency. Your car ...


7

Background I would be primarily concerned with the i-VTEC cam related mechanisms. I do not see that this engine is an interference engine. If it were an interference engine and you floated your valves, you would have more than likely had valve to piston contact and that would have immediate effect on your motor as well as your driving experience, you ...


7

This is a math-only question, and no one has explained the formulas. Also I like the idea of this simple question having multiple answers so... RPM is Revolutions Per Minute, but we want a time in seconds. When you hear that word "per" it means division. So, what we have is 4000 revolutions / 1 minute (where / is the division symbol). This easily ...


6

I'm working on developing an automatic bicycle (mostly microcontroller based) and I'd presume I'd be shifting in a similar way to a car. Well, you're in for a shock: it's going to be pretty different. So my question is, what factors does the transmission take into consideration when shifting? ... So is it concerned more with speed, rpm, some ...


6

There are 3 key factors to work on when uprating for higher revs: Moving parts Spinning a rod, cam or flywheel faster than it is rated for will result in it destroying itself, often spectacularly, as the stresses become too much. Moving linkages and pistons back and forth also takes a lot of energy - Kinetic energy = 1/2 m v squared, and it is that ...


6

To expand on Anarach's excellent answer; the burn rate of diesel is slower than petrol and at higher RPM you would risk the exhaust valve opening whist the mixture in the cylinder was still burning. Increase the RPM higher, especially on engines designed with some overlap so that inlet and exhaust valves are open at the same time and if you still have a ...


6

It's very hard to say what damage, if any, will have occurred. All I can tell you is from my own personal experience. I once went from the red line in 3rd gear with a wide open throttle to 4th at approximately 90mph on a 1983 Golf and accidentally selected 2nd (and managed to get the clutch up). The instantaneous effect was that all of the dials gave ...


6

To get us on the same footing, I'm going to assume by saying "clutch pressed halfway" you are suggesting the clutch be halfway engaged (meaning, you are still getting power from the engine, but it's not fully engaged). What you are talking about is called slipping the clutch. It is a process whereby you can get the engine within the power/torque band ...


6

In addition to what JPhi1618 said... You can set any standard tach up with clips. I did this with a cheap tach when tuning my truck. They have 4 wires - positive, ground, signal, light. Positive and light go to the positive side of the battery with a fuse. Ground goes to the negative side of the battery or an unpainted part of the engine/body. Signal ...


5

The rev limiter would have to be removed. This would be involved in a custom DME. With the limiter removed then you'd be able to blow it up if you wanted to. To support the higher revs, the vehicle would need the engine internals worked on. Stronger camshaft(s), valves, valve springs. (Head work). Depending on the strength of the rotating assembly at the ...


5

As you said the crux of the issue has to do with getting every last amount of energy out of a unit of fuel. You can consider this your total fuel efficiency. Accelerating your vehicle from rest to 60mph or 100km/h will require a fixed amount of energy based on the weight of the vehicle. (excluding wind, friction and rolling resistance). So you need to ...


5

Paulster2 is right, varying the injection timing with respect to the engine crank angle timing is the main way to control the combustion process in a diesel engine. In a conventional gasoline engine (PFI or SIDI) fuel and air are largely pre-mixed before the spark event (which controls the start of the combustion process) which then leads to a fast ...


5

Engines are designed to withstand a certain amount of stress. When you exceed that threshold, longevity will start to deteriorate. I stated something to that effect in this answer. The engine has a redline where you shouldn't take its speed past. This redline is not the maximum speed which the engine can run, but more correctly the threshold which you ...


5

Doesn't it suck up only as much as engine speed and throttle position allows? No, throttle position and engine load determine the quantity of air consumed. It can be quite hard to understand at first how a naturally-aspirated engine can ingest different quantities of air at the same RPM. Here's what the Engine Management Fundamentals chapter of the ...


5

I am presuming this is a gasoline engine. If so, the symptoms sound very much like the throttle internals are dirty. If gunge builds up on the butterfly valve, it can restrict the air required for a smooth idle when the butterfly is closed, so the engine ECU needs to open the Idle Air Valve more that it thinks it should have to and you get into a cycle of ...


5

It depends what you're trying to optimize. If you're looking for optimal acceleration, more RPMs are better. Most engines today produce peak power at redline. As for optimal efficiency, there's two parts to that as well: Turning fuel into mechanical energy as efficiently as possible, and using the least amount of fuel to cover a distance. The engine ...


4

This sounds like a clutch problem. If it is nearing end of life opening the throttle can break its friction, which is why the speed drops and revs increase. Get it along to the garage before it finally gives up the ghost.


4

Within a certain range, of course more RPMs mean more wear. Especially if your maintenance is based on time or miles. Consider a bearing that has a lifetime of 1,000,000 revolutions. If you drive at 5,000 RPM, that bearing is going to use up its lifetime twice as fast as if you were driving at 2,500 RPM. On the other hand, "lugging" an engine at too low an ...


4

Alternators aren't built for one engine so the manufacturer can't possibly know the gearing / ratio between the alternator and the engine. Therefore the RPM listed in the spec will be the RPM for the alternator. To calculate the alternators RPM you will need to find the diameter of the alternator pully [a] and the one connected to (presumably) the ...


4

It's just another word for Rev limiter. It means that when you reach 4,400 RPM, the ECU starts to limit the amount of injected fuel and air, in order not to let the engine rev any further, because revving it any further may cause severe damage to it.


4

The issue with low idle is more significant when viewed from the perspective of oil pressure. Reducing the idle, albeit a noble cause of saving the planet, reduces overall emissions insignificantly when compared to the implosion of an engine. The carbon footprint related to throwing a rod and having processed oil spill out over an open uncontrolled surface ...



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