This would explain why engines slow down at idle when you switch on all the electrical accessories. A good example of parasitic loss
In the case of a race car, getting rid of the loss due to turning on accessories should be what I consider low hanging fruit. Most serious track car owners would remove AC, get rid of radios, redundant wiring and modules for electric seats/windows whatever, and not just for weight savings, but also to reduce all electric draw.
Any electrics drawing current (in my mind) would be items of necessity, and I wouldn't actually consider them "parasitic" in our context.
If it helps the car go faster, it is necessary, not (in my mind) parasitic. The parasitic losses, in my mind again, are losses that might be avoidable, and hopefully can be minimized without loss of reliability, or in the best of all worlds, costing too much.
In this context over-driving a water pump is wasted energy, and turning a hydraulic PS pump when driving in a straight line is wasted energy too.... so these two items are ripe for revision on a track car.
VR6Turbo wrote:On parasitic losses in general, is there much gain in knife edged cranks, windage trays etc etc?
I do not consider myself expert on all things related to crank design, but some of what goes into a crank is meant for harmonics, smoothness of operation, some of the weight is helpful in the sense of a gyroscope and momentum to preserve longevity etc etc etc... I'm speaking loosely, and not with complete authority.
I've seen examples of race engine builders preaching both sides of the crank lightening arguements, and I think its a very complex subject. Some say you shorten the life of the engine dramatically if you take off too much, but in the interim get many of the benefits of a light flywheel, others disagree and say its a matter of extent, and that you can safely remove quite a bit of weight without compromise blah blah blah. It would be about as useful I think to debate this broadly without reference to a specific engine and crank as debating belt vs direct drive turntables in the audio world. IE... do it right and you're probably OK, do it poorly, and its best not done.
VR6Turbo wrote:Out of interest, when OEMs dyno their engines, do they measure the power in full road trim, or do they just strap it to the bench tester with no alternator or pumps etc?
I'm not sure there are any standards. Similarly when a manufacturer posts a weight for an engine, it is not easy to determine if its got oil on board, ancillaries on board, air box, air filter, harness, DME, oil cooler etc etc etc... makes comparing numbers across generations or different competition difficult.