Discussion
I may have to answer this question in an exam in jan so hopefully nobody minds if I indulge in a little revision.
Power is the rate at which energy is transfered. Brake power is the actual power that leaves the engine after frictional losses, can be measured at the flywheel or the wheels.
Mathematically it's brake torque multiplied by revs
Power is the rate at which energy is transfered. Brake power is the actual power that leaves the engine after frictional losses, can be measured at the flywheel or the wheels.
Mathematically it's brake torque multiplied by revs
xRIEx said:
I thought it was before frictional losses, is that wrong?
Depends, bhp is very imprecise. If you're talking power at the flywheel then this includes frictional losses from the engine but not the gearbox. Power before any frictional losses is called indicated power and is obtained by integrating the P-V diagram, in a way this is the energy it was possible to extract from the fuel minus volumetric (air flow restrictions through the engine) and thermal (heat dumped into the cooling system and exhaust) losses. Perhaps it's the gearbox frictional losses you're thinking of?
Benrad said:
xRIEx said:
I thought it was before frictional losses, is that wrong?
Depends, bhp is very imprecise. If you're talking power at the flywheel then this includes frictional losses from the engine but not the gearbox. Power before any frictional losses is called indicated power and is obtained by integrating the P-V diagram, in a way this is the energy it was possible to extract from the fuel minus volumetric (air flow restrictions through the engine) and thermal (heat dumped into the cooling system and exhaust) losses. Perhaps it's the gearbox frictional losses you're thinking of?
*[pedant]Torque is measured by the dyno[/pedant]
xRIEx said:
Benrad said:
xRIEx said:
I thought it was before frictional losses, is that wrong?
Depends, bhp is very imprecise. If you're talking power at the flywheel then this includes frictional losses from the engine but not the gearbox. Power before any frictional losses is called indicated power and is obtained by integrating the P-V diagram, in a way this is the energy it was possible to extract from the fuel minus volumetric (air flow restrictions through the engine) and thermal (heat dumped into the cooling system and exhaust) losses. Perhaps it's the gearbox frictional losses you're thinking of?
*[pedant]Torque is measured by the dyno[/pedant]
Benrad said:
Depends, bhp is very imprecise.
BHP is very precise according to SAE/DIN specifications. How it is measured is where the imprecision lies. As stated, OEM BHP is measured at the engine flywheel with ancillaries attached. What some rolling roads do is measure the wheel torque, do some maths (lb/ft*rmp/5252) and come up with wheel power. They also measure some of the losses and add the two together to come up with flywheel power. This is not so precise.The term horse power was brought about by James Watt who, when trying to convince coal mine owners that a steam engine was better than a horse, compared the amount of work done by his steam engines to the amount of work done by the horses. He measured the work done by several horses and came up with a figure of 1hp=550lb raised 10ft in 10 seconds. The modern metric equivalent is 75kg 10 metres in 10 seconds, stated in PS or CV. This also has an ISO metric of 1000N (or 98.1kg) raised 10metres in 10 seconds and this is a KW.
The brake reference is to the method used to measure power which is more convenient than lifting a weight up. The brake applies a load to the engine and the torque is measured, torque being a unit of rotational force as opposed to vertical force i.e our 550lb weight. All we need to calculate the horse power is the speed which is the engine speed in rpm. lb/ft*rmp/5252.
https://www.tdi-plc.com/files/Rototest_white_paper...
Zad said:
It is 298.3 kiloWatts.
Or 2983 100-Watt lightbulbs.
Or 298 1-bar electric fires.
Or 119 2.5kW kettles
Or... VROOMMM VROOM WHEEEEEEEEEEEEEEEE
That is 400bhp.Or 2983 100-Watt lightbulbs.
Or 298 1-bar electric fires.
Or 119 2.5kW kettles
Or... VROOMMM VROOM WHEEEEEEEEEEEEEEEE
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