Q1:
In video #5 above, ...
he says "the lever arm of the crankshaft is one foot...". Could you please help me with it?
That video had my head spinning and I know what he is talking about!
All that he is trying to say, in a very round about way, is
that he has a pulley on the end of the crankshaft,
the pulley is 1ft in diameter,
there is a rope over the pulley,
so, the distance between the rope and the centre of the crankshaft is 1 foot.
Q2:
In
this video from the article at #4 above, from 1:33 to 2:13, it says something like 'so what other things they might exclude from the engine horsepower, well if it has power steering they are not going to account for power required in order to steer the car, they may also not include the power if you have air conditioner on, other things which drain power from your engine which might not be included in what the manufacturer claiming is the horsepower are alternator, water pump, restrictive exhaust'.
I do believe that wheel horsepower and wheel torque are affected to great extent by the operation of an air conditioner and I'm sure that other things also affect but I don't think that their effect is that much. Do you agree with me?
All to do with making specifications look better to help salesmen.
It used to be that some manufacturers would quote the "Gross BHP" figure for an engine. This would be the power at the flywheel for the bare engine.
No cooling fan
No water pump
No Alternator.
No air filter
No silencer (muffler)
No anything else that you can think of which uses power from the engine.
The "Net BHP" figure would include the losses for everything needed for a practical vehicle.
The aircon can be a big load on the engine, especially for a small car with a small engine.
Q3:
I have never been through the manual of any automobile but I do think that the manufacturers should show torque-BHP-RMP curve for every model. In video #6 above, at 2:42 it is shown that 2011 Mercedes-Benz S63 AMG has maximum torque over an extended range of RMP which is a good thing, in my opinion. What do you think?
Less than 1% of owners would have any idea what it was telling them.
A broad torque range is a good thing.
An example form my own experience.
At one time I owned a Mk2 VW Golf GTI, quite a fast little car with a 1.8 litre engine.
There was good low-down torque, it would pull well from about 1500rpm.
I replace that car with a Mk3 VW Golf GTI which had a 2 litre engine and was more powerfull 150 BHP instead of 120BHP for the Mk2.
But on my daily commute to/from work it was slower!
Why, because below 3000RPM there was not as much torque as there was with the older car with the smaller engine.
It would be a bad isea to try and drive at 80MPH on the little back roads which I used on my way to work.
I would have been in 2nd/3rd gear all the way! No good for the fuel economy, not good for the nerves!
Q4:
I have always thought that the rating for volume of engine or engine displacement really tells you about how power an engine is. In my opinion, engine torque is mostly related to engine displacement. Do you agree? Thank you.
Engine displacement has a big effect on power and torque.
But there are many factors in the design of an engine which affect the power torque curves.
Cylinder bore and stroke.
Valve timing.
Ignition timing.
Length and diameter of inlet manifold.
Length and diameter of exhaust manifold.
For any basic engine, you can get good low down torque but poor (?) peak power, or, good high top end power and poor low down torque by varying these factors.
Example, I once had a Suzuki Vitara, a cheap almost crude 4x4, with a 1.6 litre engine. But it did exactly what it said on the tin!
If I drove the thing at 60MPH it scared me stiff!
But, put it in low ratio 1st gear and it would go anywhere. If you could get suitable tyres, it would climb the North Face of the Eiger* at about 2000RPM.
* A steep mountain somewhere in Europe, the basis for one of Clint Eastwoods worst films.
JimB
