When I turn on my car, stop at a light, or just have it in park it hovers around 750 rpm (my older car sat at like 1-1.2k rpm). But why? It’s not moving the car or anything. I know some modern cars turn off the engine if it idles for too long but that doesn’t really explain why. Also when I coast on the highway it will idle at even higher rpm’s. I would have expected the automatic transmission to shift down when it’s not applying any acceleration.
Furthermore, do electric engines idle at a rpm? If not does this make electric cars more energy efficient?
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Inline 4 cylinder motor has to spin the crankshaft using only 2 cylinders per revolution (the other 2 are sucking a new fuel-air mixture in the meantime). That means they can only “kick” the crankshaft only once per 180 degrees of spin cycle. It is efficient enough if you are spinning at 1000RPM rate. If you have more cylinders (let’s say inline 6 cylinder) you have 3 pistons that work every cycle , so you push the crankshaft once per 120 degrees- it’s easier so engine doesn’t have to run so fast- it idles at 800RPM. Old tractors idle at ~100- 200RPM because they have a huge and heavy flywheel connected to crankshaft which keeps the spinning going without stalling at such RPMs.
Inline 4 cylinder motor has to spin the crankshaft using only 2 cylinders per revolution (the other 2 are sucking a new fuel-air mixture in the meantime). That means they can only “kick” the crankshaft only once per 180 degrees of spin cycle. It is efficient enough if you are spinning at 1000RPM rate. If you have more cylinders (let’s say inline 6 cylinder) you have 3 pistons that work every cycle , so you push the crankshaft once per 120 degrees- it’s easier so engine doesn’t have to run so fast- it idles at 800RPM. Old tractors idle at ~100- 200RPM because they have a huge and heavy flywheel connected to crankshaft which keeps the spinning going without stalling at such RPMs.
> Furthermore, do electric engines idle at a rpm?
Do you understand *why* a gasoline engine idles?
> Furthermore, do electric engines idle at a rpm?
Do you understand *why* a gasoline engine idles?
Kind op counterintuitive, but a car engine runs cleaner and leaner on a bit higher RPM. The combustion simply isn’t as complete at a lower RPM.
It also depends on the weather. If it is cold, before the engine is warm, it will stall if you let the RPM drop.
Kind op counterintuitive, but a car engine runs cleaner and leaner on a bit higher RPM. The combustion simply isn’t as complete at a lower RPM.
It also depends on the weather. If it is cold, before the engine is warm, it will stall if you let the RPM drop.
Theres a minimum rpm needed to keep the alternator running. Depending on the type of vehicle you have, the alternator output may be different than another vehicle…truck with a tow package vs a sedan. Of course if you’re cruising on the highway the rpm is going to be higher…cause you’re telling the engine to spin faster. Even if you take your foot off the gas, the engine is physically connected to the wheels via the transmission. The inertia of the car is keeping the wheels spinning and thus the engine to spin. Heres an experiment for you to do…find a hill in the town. Get up to speed and notice the rpm, then put the transmission in neutral and watch the rpm drop. Thats because you’ve physically disconnected the wheels from the engine and now there’s no load on the engine.
Theres a minimum rpm needed to keep the alternator running. Depending on the type of vehicle you have, the alternator output may be different than another vehicle…truck with a tow package vs a sedan. Of course if you’re cruising on the highway the rpm is going to be higher…cause you’re telling the engine to spin faster. Even if you take your foot off the gas, the engine is physically connected to the wheels via the transmission. The inertia of the car is keeping the wheels spinning and thus the engine to spin. Heres an experiment for you to do…find a hill in the town. Get up to speed and notice the rpm, then put the transmission in neutral and watch the rpm drop. Thats because you’ve physically disconnected the wheels from the engine and now there’s no load on the engine.
I’ve always had gas cars and they have all had an idle RPM at around 750-800.
Older cars idle higher at startup because the engine is warming up; once the engine temperature is optimal, they return to under 1000.
Unless the car is modified (camshafts, timing, etc), a high idle RPM is an indication that something could be wrong with the car. It could be a sensor, a fuse, or even a torn gasket or vacuum line.
I’ve always had gas cars and they have all had an idle RPM at around 750-800.
Older cars idle higher at startup because the engine is warming up; once the engine temperature is optimal, they return to under 1000.
Unless the car is modified (camshafts, timing, etc), a high idle RPM is an indication that something could be wrong with the car. It could be a sensor, a fuse, or even a torn gasket or vacuum line.
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