- #1
thender
- 39
- 0
What is the definition of "Engine Load"
A lot of things I have read make reference to engine load but it is not clear if there are different meanings.
One definition seems to be that the engine load is the amount of air flowing through the engine as a percentage of the theoretical maximum.
So if I had a vehicle running in neutral with the throttle wide open I would be very close to the maximum of that type of "engine load". But the engine wouldn't really be doing any work. So if work was the type of load that we are talking about then it's different.
Like towing a trailer up a grade is another type of engine load, and it has more to do with how much resistance there is to turning the crankshaft.
I think perhaps the actual power output is what's different, the amount of WORK being performed.
And from what I can tell running an engine under a heavy work load produces different conditions like higher cylinder temperatures and peak pressures.
Engine Load is an OBD-II standard parameter but I still don't understand how to interpret it properly.
I almost forgot to mention it but the amount of vacuum in the intake manifold is often said to indicate the engine loading. I'm not really sure why. From what I know manifold vacuum is affected by the engine speed, the atmospheric pressure, and the throttle position mainly (in naturally aspirated engines).
High vacuum may indicate a high rate of air consumption by the engine, or high restriction from the throttle. Low vacuum could indicate lower consumption by the engine or highly open throttle conditions.
Vacuum is complicated by the engine characteristics that affect cylinder filling like valve timing lift and duration, engine speed, tuned ports etc.
I see that these things are all correlated to the concept of engine load but don't fully understand the rationale. Fuel pressure regulators are controlled using manifold vacuum for example.
One other thing, engine load seems closely tied to how the engine utilized, in a passenger car the engine probably operates at very light loads the vast majority of the time, putting out only enough power to maintain the current speed. Load would be higher when accelerating the vehicle quickly such as driving onto a highway via an on ramp, but would generally be low, with a correspondingly low throttle opening. Heavier vehicles towing heavy loads may operate at higher sustained engine loading. Lastly from what I've heard aircraft engines typically operate at a high load with little fluctuation.
It strikes me that the transmission gearing is as significant the throttle position and other items when considering engine load and total power output.
Thanks,
-Andrew
A lot of things I have read make reference to engine load but it is not clear if there are different meanings.
One definition seems to be that the engine load is the amount of air flowing through the engine as a percentage of the theoretical maximum.
So if I had a vehicle running in neutral with the throttle wide open I would be very close to the maximum of that type of "engine load". But the engine wouldn't really be doing any work. So if work was the type of load that we are talking about then it's different.
Like towing a trailer up a grade is another type of engine load, and it has more to do with how much resistance there is to turning the crankshaft.
I think perhaps the actual power output is what's different, the amount of WORK being performed.
And from what I can tell running an engine under a heavy work load produces different conditions like higher cylinder temperatures and peak pressures.
Engine Load is an OBD-II standard parameter but I still don't understand how to interpret it properly.
I almost forgot to mention it but the amount of vacuum in the intake manifold is often said to indicate the engine loading. I'm not really sure why. From what I know manifold vacuum is affected by the engine speed, the atmospheric pressure, and the throttle position mainly (in naturally aspirated engines).
High vacuum may indicate a high rate of air consumption by the engine, or high restriction from the throttle. Low vacuum could indicate lower consumption by the engine or highly open throttle conditions.
Vacuum is complicated by the engine characteristics that affect cylinder filling like valve timing lift and duration, engine speed, tuned ports etc.
I see that these things are all correlated to the concept of engine load but don't fully understand the rationale. Fuel pressure regulators are controlled using manifold vacuum for example.
One other thing, engine load seems closely tied to how the engine utilized, in a passenger car the engine probably operates at very light loads the vast majority of the time, putting out only enough power to maintain the current speed. Load would be higher when accelerating the vehicle quickly such as driving onto a highway via an on ramp, but would generally be low, with a correspondingly low throttle opening. Heavier vehicles towing heavy loads may operate at higher sustained engine loading. Lastly from what I've heard aircraft engines typically operate at a high load with little fluctuation.
It strikes me that the transmission gearing is as significant the throttle position and other items when considering engine load and total power output.
Thanks,
-Andrew
Last edited: