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How it Works! Welcome to Auto 101

This is for newbies and experts alike. If you don't know the basics about cars (or forgotten them) this is the place to find out. Even if you have more technical questions, post it here!

This topic is meant to run the technical gamut. Anything from how to change a flat to how to rebuild an engine. From what tire treads are for to what the heck a k-body type car is.

Just remember that there are non-engineers and newbies (like me) out there, so please try to use plain ol' English whenever possible (especially for the lurkers out there ;>). Thanks!!!


  • pocahontaspocahontas Posts: 802
    Hi jusdreamin- Good topic! Thanks for starting up this new disscussion.

    To everyone- As I mentioned above, this discussion is linked to both the Women's Auto Center and the Maintenance & Repair message boards. This means you have the option to access this discussion from either one of these message boards.

    Hope you enjoy discussing this subject with the participants from both of these message boards. Thanks for your participation! ;-)

    Hatchbacks / Station Wagons / Women's Auto Center Boards

  • mfarmer2mfarmer2 Posts: 67
    I just bought a front wheel drive Buick Rendezvous with the "full range" traction control option. Not really sure what that means, except for that it helps control the vehicle better. Can someone explain to me how "full range" traction control works?

    Also how does traction control differ from all wheel drive? Please use the simplest terms; I tried reading an article on the subject and was still did not quite get it. Thanks ahead of time for any feedback. :-)

  • What are the differences between AWD, FWD, RWD, and 4WD? Why would someone want one over the others?
  • I think traction control transfers the power from the wheels that slip to the wheels that grip.

    AWD is similar to 4WD. The difference is that you can turn off 4WD if you don't need it.

    I think the best way to put it is that both AWD and 4WD have all four wheels "gripping" the road. I'm rephrasing what I said earlier to clarify here: AWD has all four wheels constantly "gripping" the road.

    AWD tends to get worse mileage and wear out tires quicker.

    I didn't realize that there was "full range" TC. Could that be a marketing ploy?
  • pocahontaspocahontas Posts: 802
    In addition to the feedback here, you may also want to check out these articles from Edmunds Ownership Section: What Wheel Drive?, By Karl Bruer and Traction Control, by Scott Memmer. Do these help to answer some of your questions?

    Perhaps someone else has more to add.... ;-)

    Hatchbacks / Station Wagons / Women's Auto Center Boards
  • 0patience0patience Oregon CoastPosts: 1,578
    AWD (All Wheel Drive) - All wheels are powered fulltime, There are good and bad points to all wheel drive.

    RWD (Rear Wheel Drive) - Up until the 70s, was pretty much the exclusive design, with exception of the Tornado and a few imports. Control can suffer becasue of the "push" that it has on the vehicle. But it is my personal preferance.

    FWD (Front Wheel Drive) - Has been said that it has better control over rear wheel drive, because the power is pulling the vehicle in the directions that the tires are pointed.

    4x4 - 4 Wheel srive, comes in full time (Some are a partial part time) or part time.
    Full time, is setup where the hubs are locked constantly, and the 4 wheel drive is engaged. Some full time, have the hubs locked and you still have control over whether it is in 2WD or 4x4. Part time has hubs that can be locked or unlocked and usually have 4 Low, 4 high and 2 high capabilities.

    Full range traction control - Is not really any of them. Designed to put the power to the wheels that the computer sees that needs it. If one tire starts to lose traction, the computer (loosely termed) will sense the traction loss and shift the power to another tire. While this is a pretty good system, it can be extremely expensive should a problem come about.

    jusdreamin, You wrote;
    has all four wheels constantly "gripping" the road.
    That is not accurate. Any of the drives put power to the wheels, it cares less if the are gripping or not and often at least one of them are NOT gripping the road. Esecially 4x4 and AWD. At any time in a corner or turn, under power or acceleration, there is at least one tire not "gripping" the road.
  • Thanks. Well, at least in essence I got the traction control right.

    I thought the WD's did have something to do with power, I just couldn't remember it. Yeah... that's it... I couldn't remember. :)
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 57,338
    Also keep in mind that "grip" is related solely and ONLY to the tires, as Opatience implies. You can have 40 wheel-drive, or even tank treads, and you'll go off the road if there is no "grip".

    Many an AWD or 4X4 driver has learned the hard way not to be overconfident in an "all-wheel drive" vehicle.

    Your car or truck stays on the road only because of those 4 little tire footprints, amounting to only a handful of square inches of tire patch.

    MODERATOR --Need help with anything? Click on my name!

  • steverstever Posts: 52,572
    The 4WD & AWD systems explained discussion may also be of interest.

    Vans, SUVs and Aftermarket & Accessories Message Boards

  • Thanks!!

    Does anybody know what curb weight is and why is it important?
  • Curb weight is the net weight of the vehicle. The car with a full fuel tank and no passengers or cargo.
  • zueslewiszueslewis Posts: 2,353
    the way I've always explained traction control is that it is just the opposite of anti-lock braking and frequently uses the same sensors to control the system.

    With ABS, sensors "sense" pending lock up of your wheels during hard braking and you get the best braking ability when the wheels are turning slowly instead of skidding. That's why you can steer (and actually have it work) when "panic" braking with an ABS-equipped car.

    With traction control, the sensors keep your wheels from spinning, slowing things down so your tires can work with a slippery surface instead of sliding over it.

    Curb weight - very important when adding weight of your cargo to make sure you don't exceed "gross vehicle weight" or GVW. Also good to know if you're driving over old wooden bridges!
  • I know that this is an oversimplification, but I use this in conjunction with horsepower (or torque) to get a very rough estimate of the (relative) acceleration power of a vehicle.

    As an example take a 01 Honda Acccord LX V6 automatic (curb weight/hp)
    3274/200 ~ 16.4
    vs. a 01 Acura 3.2 TL w/nav automatic
    3508/225 ~ 15.6

    I would (very) roughly expect the vehicle with the lower amount of weight per horsepower to have the better acceleration.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 57,338
    All other things being equal, probably that's true. But if there were variances in tires, differential/transaxle gearing or even (at higher speeds) aerodynamics, your formula might not hold true.

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  • Mr Shiftright, I agree that there are many other factors are not considered such as hp vs rpm, load distribution (e.g. FWD with 60% of weight on front axle), addition of driver/passenger weight, etc. Also, actual vs rated.

    Very rough estimate. Did I mention that it is very rough? :~)
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 57,338
    Oh, okay, this is THEORETICAL physics we are talking it!

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  • That's NOT theoretical physics!! Theoretical physists don't beleive in numbers, therefore theoretical physics DOESN'T involve them!!!

    I found that out the hard way...:)

    Hmm...Would "under ideal conditions" be more appropriate?
  • What components are covered under the "Power Train Warranty"? What should I know about this type of warranty when shopping for a new car? Is a 10yr/100,000mi much more desirable than a 3yr/36,000mi? Or will I ever really need it?
  • zueslewiszueslewis Posts: 2,353
    The powertrain warranty USUALLY (very few exceptions) describes defects with the INTERNAL portions of the engine, transmission/transaxle and the axle shafts. The powertrain warranty does not cover adjacent components like all the electronic control devices that tell the powertrain how to act. There are at least three major control modules, two major wiring harnesses and gillions of sensors involved in the powertrain that are NOT covered by most powertrain warranties. Only the basic warranty covers these items, but the 5 year/5000 or 10 year/10000 mile P/T warranties sound good as a sales technique. 5 years roadside assistance? Why should a manufacturer feel compelled to make these promises if they weren't NECESSARY? Scary, huh?

    My main point is that the electrical components that may fail at 50,000 miles are very expensive and not covered by the P/T warranty.
  • You may also want to read this Edmunds' article about Warranty and Roadside Assistance Coverage. As mentioned here, the Drive Train (a.k.a. power train) warranty "takes care of most of the parts that make the car move, like the engine, transmission, drive axles and driveshaft."

    These are major components than can be can be very expensive to repair. So imo, a 10 year powertrain may certainly come in handy, especially with certain makes/models (I won't mention specifics); you can refer to Edmunds' new and used car guides for basic overview and reliability information.

    Zueslewis also makes a good point about adjacent components (i.e control modules/major wiring) not being covered on many manufacturer's power train warranties, only on the basic warranty. Not a bad idea to check with the specific manufacturer or dealer to find out exactly what is covered in their basic & power train warranty. Good luck. ;-)

    Hatchbacks / Station Wagons / Women's Auto Center Boards
  • I was told recently by a mechanic I trust that I have the wrong sized spark plugs in my van. I returned the van to the dealer to have them replaced with the correct ones and the service tech said "Well if you want to..."
    I had been under the impression that spark plugs were sorta important to get right. What is the long term of not replacing the plugs? Should I have it done?
  • mrdetailermrdetailer Posts: 1,118
    spark plugs run hotter or colder depending on the type. Generally follow the maufacturer's recommendations.

    I wonder what he means by wrong size. If the diameter is truly wrong, it shouldn't even be able to fit in the socket. If he means that the spark plug gap is incorrect that can affect firing ability. Most spark plugs these days have a correct gap set already. Otherwise it has to be set using a spark plug wrench.
  • PF_FlyerPF_Flyer Pennsylvania Furnace, PAPosts: 7,716
    Maybe we'll have an Auto101 themed trivia one of these weeks to test some basic knowledge of you guys... but in the meantime...


    Hey, it's Friday! Just a reminder that the Friday Freeway Chat & Trivia Game chat is on tonight (5-6pm Pacific/8-9 pm Eastern). Hope to see you there!

    PF Flyer


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  • landru2landru2 Posts: 638
    does not transfer power between wheels. It controls the traction of each wheel independently. Anyone that lives where it snows has had the experience of trying to pull away from a stop sign and just spinning your wheels on the ice. Traction control stops each wheel from spinning by using the braking system to slow the wheel down so that when you step on the gas the wheels just roll forward rather than spinning. At higher speeds (say if you step on the gas to pass a truck) instead of using the braking system, the Traction Control will cut the engine power slightly to keep the wheels from spinning.
  • 0patience0patience Oregon CoastPosts: 1,578
    Ok, let's assume what you are saying is correct.
    You have four wheels, unless you have some way to transfer the power from one side to the other, the differential will supply the power to the path of least resistance. So, you end up with one wheel that may have traction and the other that doesn't. As long as it is slipping, even if you cut power to it, the power stays to that wheel.
  • flootfloot Posts: 22
    1) Does it matter what brand of air filter I put in my 1996 Corolla? I buy them from an auto parts store and I noticed last time I changed it that the new filter had fewer pleats in the paper than the old one. Does that matter?

    2) Can anyone point me to a good explanation of what "125hp @ 5,800rpm; 125 lb.-ft. @ 4,000rpm"
    translates into as far as engine performance is concerned? The HP number makes sense, but I am really fuzzy on what torque means.

    Thanks for your help -- these forums are awesome!
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 57,338
    Traction Control can be a misnomer, depending on how you look at it.

    "Traction Assist" might be more accurate, since ultimately traction is ultimately dependent solely on your tires.

    On sheer ice, there is no traction for the tires, no matter what mechanism is driving them. They can spin fast or they can spin slow. On really bad ice, your car will skid even with the engine off and brakes on and you not in the car!

    MODERATOR --Need help with anything? Click on my name!

  • zueslewiszueslewis Posts: 2,353
    You can use any major-brand air filter in your Corolla. There are a few differences between aftermarket (versus original equipment) filters, but the overall design is pretty much the same.

    The most important factor is that you ARE changing the filter. In my years in the service business, I was shocked each time people would not change the air filter, or equally, if not more important, change the fuel filter regularly. I had an 88 Toyota Corolla FX-16 GTS (fun car, raced autocross with it) and I changed the fuel filter every 10,000 miles. Those things clog easily with the convenience store gas most of us use.

    On the horsepower/torque subject, the 128 hp @ 5800 rpms is the peak power output of your car. Its "torque" peak at 4000 rpm means the engine produces the most "twisting effect" at that engine speed. Torque and HP are similar, but different. (Clear as mud, huh?) To simplify, torque is the twisting motion that makes your car move initially and HP is the force that sustains the speed. Torque and HP have some radical effects as used in high-performance applications and you see some strange things happen. Like when a powerful front-drive car breaks an axle when launching at a drag race - thats torque. When a NASCAR stock car accelerates from 180 to 200 mph, that's horsepower.
  • flootfloot Posts: 22 if I take two different cars such as
    Toyota Corolla 125 ft.-lbs.@ 4000rpm
    Nissan Sentra XE 129 ft.-lbs @ 2400rpm

    Does this mean the Sentra will have more ooommph
    in the early stage of accelerating? (Thanks for the air filter info.)
  • 0patience0patience Oregon CoastPosts: 1,578
    Does this mean the Sentra will have more ooommph
    in the early stage of accelerating?

    Well, yes.
    Think of it this way,
    We will use your legs for sake of simplicity.
    Ok, let's say you can lift 100 lbs with your legs, plus your physical weight of say, 150 lbs over a certain period of time. This would be rated as horsepower.

    Now, say you can jump with that hundred pounds,
    that would be rated as torque.

    This is extremely over simplified, but hopefully it helps distinguish the difference.
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