[burly]

I'll see if I can help you out a bit here. I do know that whatever I say, there will be some distibuting the facts with other members of the forum, since you are talking about a fairly broad range of topics, and you can get really technical about them. However, hopefully I can provide you with a basic understanding.

Let's start with brakes. It takes several hundred horsepower to get your vehicle to 60 MPH in 120 feet, yet those little brakes can stop you in as short a distance. So, what makes good brakes? Well, first of all, area. The larger the "swept" area of the brakes, the more contact there is between the pads and the rotors/drums. The more contact area for a given abrasiveness (or bite) of a pad, the more stopping power. Now, while you cannot put anymore braking power to the ground then your tires have traction, it isn't quite as simple as "as long as you can lock them up, they are as good as they can be". One big factor, is brake fade. Fade is caused when the rotor/drum and the pads heat up so much that a glazing occurs on the pads, drastically limiting the stopping power. Larger brakes have more swept area and thus more surface area and mass for heat dissipation. It has a double effect, since there is more swept area and thus stopping power, it requires a lower application of force to apply the same amount of stopping power as a smaller brake system, and with less pressure per square inch, less heat is generated. So while the stock brakes on your vehicle may be able to lock up the wheels on the highway to stop you in an emergency, they would not be good for racing. After such a hard stop, if you were to have to do it again soon afterwards, your stopping distance would likely be much greater. At the track, this translates into massive brake fade and pad wear when driven hard.

On to engines. High revving engines, everything else equal, do generally wear out faster (other things like torque, application, and engine type play roles as well amonst other things). This is because at increased engine speeds, there is increased heat production, increased valvetrain stress, the crank is spinning faster and harder, and all and all, more parts are closer to their limit. Heat is probably the number one issue. At higher speeds, the friction on the parts increases (its like rubbing your hands together - the faster you move them together, the hotter they get). This has a dual effect. As the parts heat up, they generally expand, lowering the tolerances in many key areas, and thus introducing even more friction ( this is like pushing your hands together harder as you rub them together).. There are many other more technical reasons, depending on application and engine type, but basically, increased heat and friction along with increase strain due to acceleration levels on various parts (like the valve springs and pistons) is a major concern in all engines.

High revving versus high torque engines is going to be a hot topic area. There are many other variables going on here but I'll try and keep it as basic and untechnical as possible. First of all, they don't necessarily use the same amount of gas. That is dependant on the type of engine and its efficiency. However, there is only a certain amount of energy in a given volume of fuel, and there is an ideal air/fuel ratio, yes. High revving engines do allow you to stay in one gear for a longer time, allow more acceleration and speed, as any time the transmission is not in gear, the engine is not working to move the vehicle. Another issue is horspower. It is easier to keep an engine in its powerband if that powerband is wider and the time it takes to shift into another gear won't drop the engine out of its powerband. This is also why close ratio transmissions with more gears (6 or 7) are used in performance applications - to keep the engine in its power band while maintaining both acceleration and top end. High torque low revving engines can move a car quickly also, but since the high torque motors usually have larger displacements and therefore more massive moving mass, the engine cannot build up speed as quickly has a high revving engine, since the high revving engine usually has lighter moving parts and revs quicker.
Hopefully, someone will clear that last part up a bit. I don't think I put that very well.

On a dyno chart you usually have two graphs, torque and horsepower. Horsepower is a mathematical product of RPM and torque. Therefore, if torque numbers begin falling off faster than RPMs are climbing, horsepower begins falling as well. The reason you get more horsepower at more RPMs is because of this mathematical relatation between RPM and torque to horsepower. Therefore, max HP is not simply at max RPM.

TIming has a lot to due with efficiency of the engine. By advancing the timing, you allow more of the power of the combustion to be transfer into the mechanical system. However, you also run a greater risk of detonation or preignition - a topic all of its own. This is why if your engine detects "knocking" - usually due to poor octane gas - it retards the timing to prevent damage to the engine. Since less power is transferred to the engine less stress is placed on it. The timing, btw, has to due with the relation of the spark to the location of the piston in the cylinder. Since this is a distance (actually, its measured in degrees, but it translates into a distance for a given engine) as RPM s increase, the time it takes the piston to traverse the distance decreases. This gives the combustion less time to take place before the piston head reaches it. By giving the timing an advance, you ignite it later in time and therefore when the piston is closer to Top Dead Center. At slower engine speeds this increases torque. However, as engine RPMs build, power is lost since the combustion cannot happen quick enough to transfer power to the engine. The problem with advancing the timing too far, is that if the octane rating on the gasoline is too low, the heat from the compression of the air/fuel mixture will become sufficient to ignite it without the spark at all, and this could lead to detonation and can melt the pistons. In a gasoline engine, this ignition due to compression is not desired at all. However, in diesel engines, thats exactly how they work. They use the compression to ignite the air/fuel mixture. Diesel burns cooler and the engines are built to withstand higher compressions, so they can withstand this. They generally produce more torque, however due in part to the larger moving mass required to make them strong enough, they are limited in RPM ranges.


I hope this starts you off well. THere are a lot of online resources that can help you understand each of these topics better in depth. One of them is this forum! Many of these topics you've brought up here have pages and pages, threads and threads of conversation on the topic in this forum. Searching through them is a good place to start. Someone else jump in and clean up my mess please.