Archive-name: rec-autos/part4  [this article is one of a pair of articles containing commonly asked automotive questions; the other article contains questions of general consumer interest, and is broken out to facilitate crossposting to misc.consumers -- rpw]  [last change: 8 February 1993; CT now permits radar detector usage,     new tire-traction q&a -- rpw]                  Commonly Asked Questions  Radar Questions:  Q:  Where are radar detectors illegal?  A:  In the US, currently Virgina and the District of Columbia prohibit     all usage of radar detectors.  New York prohibits their use in     large trucks.  In Canada, they are illegal in Manitoba, Ontario,     Quebec, Newfoundland and PEI (Prince Edward Island).  They     are apparently are illegal through most, if not all, of Europe.     Legislation which would make them illegal is pending in many other     jurisdictions; chances of such legislation passing varies a great deal.  Q:  Where are Radar Detector Detectors used?  Do they really work?  A:  Usage is spreading rapidly; initially they were used only in Canada,     but now they are appearing in New York and Virginia.  It is unsafe     to assume that they are not in use in Connecticut and D.C.     They work by detecting a certain frequency radiated by many currently     available super Het radar detectors; some brands of detector radiate     more strongly than others, and are thus more likely to be spotted.     New radar detectors are becoming available which may not be detected     by the current generation of detector detectors.  Note that a     detector may only be spotted by one of these devices if it is turned     on.  Q:  What is VASCAR?  Is it some kind of Radar?  A:  VASCAR is nothing more than a fancy stopwatch and time-speed-distance     computer.  It depends on the operator pressing buttons as the target     vehicle passes landmarks.  No radar signals are emitted by a VASCAR     system.  Q:  What is Ka band radar?  Where is it used?  Should a radar detector be     able to handle it?   A:  Ka band has recently been made available by the FCC for use in the US     in so-called photo-radar installations.  In these installations, a     low-powered beam is aimed across the road at a 45 degree angle to the     direction of traffic, and a picture is taken of vehicles which the     radar unit determines to have been in violation of the speed limit.     Tickets are mailed to the owner of the vehicle.  Because of the low     power and the 45 degree angle, many people believe that a radar     detector cannot give reasonable warning of a Ka band radar unit,     although some manufacturers of radar detectors have added such     capability anyway.  The number of locales where photo-radar is in use     is limited, and some question the legality of such units.  Best advice:     learn what photo radar units look like, and keep track of where they     are used (or else, don't speed.)  Q:  Do radar jammers work?  Are they legal?  A:  Quick answer:  No, and Not in the USA.     Detailed answer:  Cheap radar jammers do not work well at all.     Jammers that work are expensive and usually the property of the     military.  Jammers are a major violation of the regulations of the     Federal Communications Commission of the USA.  Driving technique and Vehicle Dynamics Questions:  Q:  What are understeer and oversteer?  A:  Understeer and oversteer are terms describing the behaviour of a     car while cornering near the `limit' (limit of adhesion, that is.)     Most drivers do not normally drive hard enough for these terms to     be descriptive of the situations they encounter.  Simply put, they     tell whether the car wants to go straight in a corner (steer `less',     or `understeer') or it wants to turn more in a corner (`oversteer'.)     Understeer is commonly designed into most production cars so that     untrained drivers, inadvertantly traveling too fast, won't get into     trouble.  Understeer may also be induced by using too much throttle     in a corner.  Oversteer is designed into some more performance     oriented cars; it may be induced by lifting on the throttle (Trailing     throttle oversteer, or TTO).  In extreme cases, lifting on the throttle     may induce so much oversteer that the car reacts by fishtailing or     spinning.      Some technical details:  in a corner at speed, the tires on the car     will develop what are called `slip angles'; the slip angle is the     angular difference between the direction that the car is traveling     and the direction that the steering wheel is directing the car to     travel.  In understeer, the front wheels have a greater slip angle     than the rear wheels.  In oversteer, the rear wheels have a greater     slip angle than the front wheels.  Q: What is a rev-matched downshift?  A: When downshifting, the engine must be rotating faster in the lower gear    than it was in the higher gear.  However, during a downshift, normally    you declutch and lift your foot from the throttle, so the revs drop    rather than increase.  In rev-matched downshift, you blip the throttle    before re-engaging the clutch so that the engine will already be up to    the new speed.  This results in a much smoother and faster downshift.  Q: What does heel-and-toe mean?  A: Heel-and-toe is a technique used to do a rev-matched downshift while    braking.  This is normally challenging, because you need the right foot    for both the brake and throttle.  It is called heel-and-toe because you    use one end of the foot on the brake, and the other on the throttle to    match revs for the downshift.  In many modern cars this is a misnomer;    often you must use the ball of the foot on the brake and the right side    on the throttle.     Note that some race car drivers will skip the clutch, and just use the    left foot on the brake and the right foot on the throttle, accomplishing    the same thing.  Q: What is double-clutch downshifting?  A: While your right foot is doing the above, your left foot can do one of    three things:  nothing, declutch once, or declutch twice.  The reason for    declutching twice is to match the speeds of the two shafts in the    transmission to the speed of the engine.  This is usually coupled with    rev-matching, so that while the engine is in neutral and the clutch    engaged, the throttle is blipped and both shafts of the transmission    speed up.     The procedure is as follows:    (0) declutch    (1) move gearshift lever to neutral    (2) engage clutch    (3) match revs    (4) declutch    (5) move gearshift lever to next lower gear    (6) engage clutch     This sounds like a lot of work, but with practice it becomes natural.    The problem that double-clutching solves is normally the function of the    synchronizers within the gearbox.  In transmissions without synchros or    with very worn synchros, double-clutching makes it much easier to shift.    Basically, if you double-clutch well, you are not using the synchros at    all.  This is generally unnecessary on street cars with synchros in good    condition.  Q: What do the numbers for acceleration from 0-60, 1/4 mile, skidpad, and    slalom times in the Auto Magazines really mean?  May they be compared?  A: In short, 1) not as much as the magazines want you to believe, and    2) almost never.     In more detail:  the acceleration numbers (0-60mph and 1/4 mile times    in the US) may be vaguely compared as long as they all come from the    same source.  Testing procedures vary so much from magazine to magazine    that comparing a Road & Track number to a Car & Driver number is quite    pointless.  Keep in mind, too, that the same variation applies from    driver to driver on the street; the driver is a major (often *the*    major) part of the equation.     Skidpads vary, and even if they didn't, skidpad figures are really    only tests of the stickiness of the stock tires; they change radically    when tire compounds change.  DO NOT make any assumptions about the    comparative handling of, say, two sports sedans based on skidpad numbers.    This is not to suggest that skidpads are without value, however. Skidpads    are an excellent educational tool at driving schools.  They are simply    of limited value in the comparison of anything except tires.     Slalom times are slightly more useful; they test some small parts of the    automobile's transient response.  However, they are also heavily influenced    by the stock rubber on the car, and they do not test many corners of the    car's envelope.  They DO NOT tell you all you need to know before making    a buying decision.  For example, they don't tell you what the rear end    of the car will do on a road which suddenly goes off-camber.  When a car    has an adjustable suspension, these tests are usually done in the `sport'    setting, which may be quite unsuitable for daily driving.  The list of    caveats could go on for page after page.  Q: My buddy claims that wide tires don't make any difference, according    to his freshman physics textbook, and that you can't ever accelerate    or corner at more than 1.0G.  Does he know what he's talking about?  A: 1) in short:  he hasn't got a clue.     2) in more detail: the equations for friction used in freshman physics    textbooks presume that the surfaces are smooth,  dry and non-deformable,    none of which properly apply to tire traction except in the case of a    stone cold tire on dry pavement which is far below its proper operating    temperature.     Pavement is _never_ smooth; it is always irregular to a greater or lesser    extent.  Tires, which are not really dry and solid (as rubber is a    substance which in its natural form is liquid, and which has only been    coerced into a semblance of solidity by chemical magic), deform to match    the surface of the pavement which a vehicle is traveling over.  In a tire    at operating temperature, grip is actually generated by shear stresses    inside the deformed rubber, and not by anything even remotely resembling    friction in the freshman physics sense of the term.  The colder a tire    is relative to its operating temperature, the closer its behaviour will    be to the traditional concept of friction; if much hotter than the its    proper operating temperature, the more likely the possibility of some    part of the tire actually ``reverting'' to liquid, which is mostly like    to happen deep in the tread, causing characteristic blisters and chunking.    (This latter, though, is almost completely unlikely to happen in normal    street driving, so unless you're a competition driver or do a lot of    high speed track driving, don't worry about it.)     Because tire traction is completely out of the domain of simple friction,    it does not obey the freshman physics equation at all; thus dragsters    accelerate at more than 1.0G and race cars corner and brake at more than    1.0G.  Because simple friction does not apply, it is actually possible    for different sized contact patches to generate differing amounts of    grip.  An actual analysis of tire behavior would require techniques    such as Finite Element Analysis, due to the complexity of the mechanism.  Misc. Questions:  Q:  What does <name or acronym> stand for?  A:  Here is a list of some of the names which are commonly asked     about; be careful in soliciting the meanings of other names     as misinformation abounds on the net.  In particular, NEVER     ask in rec.humor if you want a useful result.      Saab:   Svenska Aeroplan A. B.,               or The Swedish Airplane Corporation      Alfa:   Societa Anonima Lombarda Fabbrica Automobili,               or The Lombardy Automobile Manufacturing Company      Fiat:   Fabbrica Italiana di Automobili Torino,               or The Italian Automobile Manufacturers of Turin      BMW:    Bayerische Motoren Werke,               or Bavarian Motor Works      MG:     Morris Garage   Q:  Does VW own Porsche?  A:  No.  Porsche is a publicly held company, controlled by the Porsche and     Piech families.  Porsche has extensive business dealings with VW/Audi,     which causes some confusion.  Since currently Porsche is in some     financial difficulty, there is a possibility that Mercedes or VW may     be interested in purchasing the company in the near future, but this     is only speculation at this time.