? about Idle

Hey there, I don't know anything about idling so I have a few questions.

1. Is there an optimum idle rpm or is there any? (I drive a jeep wrangler :( so please don't respond with "depends, what kind'a car do you drive?" , this is all hypothetical)

2. what do drag racers have it set at before they take off? Is road race any different?

These next two don't have anything to do with what I talked about previously

3. what exactly does forged mean and how is it different from cast

4. What type (not style) of wheels are the lightest? strongest? best combination?
an ex. of an answer for this would be Magnesium forged or aluminum cast or alloy... etc.

5. what companies sell magnesium wheels besides OZ racing and BBS?

Thanks

1. Idle rpm should be a low rpm than the engine runs stable at, most cars have idle at around 800 rpm but for example a F1 engine idle at 4000 rpm and a large diesel can idle at 200 rpm or maybe even lower so this really depends on the engine.

2. Drag or road racing cars does of course don't take off from idle but at a rpm which is as high as possible without losing traction. Often Launch control is used.

3. Cast - a melted metal (or other material) is poured into a mold.
Forged - we increase the pressure on a metal (or other material) so it deforms to a shape we want. This can be done at room temperature but mostly at elevated temperature. When engineparts like conrods and crankshafts are forged this is usually done with a die in two parts, one upper and one lower. We place the heated metal above the lower one and the upper one is pressed downwards with a force that can be as high as several hundreds of metric tons so that the metalpart will take shape in the dies. There are some info about forging here http://www.hejarsmide.se/e_index.htm

4. Forged magnesium is the strongest of the common types of wheels. There are however other materials that can be used, carbon fibre as one example, which could make them even stronger. I think that aluminum matrix composite or AlBe also could make a really strong wheel, but there are also cost issues (an AlBe wheel could cost around $15,000).

5. There aren't that many manufacturers for high performance forged magnesium wheels. Speedline is together with OZ and BBS some of the few manufacturers, but these wheels cost.

thanks for the reply. I wondered something else - I know that pro drag cars do not obviously start in idle so are they in first? If so do they have a clutch or is it like that tiptronic/f1 style transmition? (excluding of course the pro drags with automatic 3 speeds).

Most dragracers use a clutch, with automatics they can use a clutch or a torque converter (turbine). Top Fuel engines are using a centrifugal clutch which can slip. F1 are using an electrohydraulic actuated clutch. However, many racing gearboxes aren't using the clutch for gearchanges.