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jusdreamin
Member Posts: 63
in General
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!!!
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!!!
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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! ;-)
Pocahontas
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Hatchbacks / Station Wagons / Women's Auto Center Boards
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. :-)
Mary
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?
Perhaps someone else has more to add.... ;-)
Pocahontas
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Hatchbacks / Station Wagons / Women's Auto Center Boards
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.
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.
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.
Steve
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Vans, SUVs and Aftermarket & Accessories Message Boards
Does anybody know what curb weight is and why is it important?
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!
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.
Very rough estimate. Did I mention that it is very rough? :~)
I found that out the hard way...:)
Hmm...Would "under ideal conditions" be more appropriate?
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.
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. ;-)
Pocahontas
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Hatchbacks / Station Wagons / Women's Auto Center Boards
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?
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.
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!
http://www.edmunds.com/townhall/chat/freewaychat.html
PF Flyer
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Pickups & News & Views Message Boards
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.
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!
"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!
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.
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.)
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.
"I have had some bad experiences with 4-cylinder engines in the past. Part of it was my fault because I wasn't as diligent with oil changes and maintainance as I should have been (but I learned my lesson, so I am a stickler about it now). Part of it was the condition that the cars were in when I bought them used. At any rate, it left me with the impression that 4 cylinder engines were more fragile and more likely to break down than 6 cylinder engines. Throwing the unknown (to me, at least) turbo factor in there just made me even more nervous, which is why I never considered it until recently."
Perhaps I can ask this question in this forum as well. How does a turbo engine work? What is different in maintaining and operating it from a "non-turbo" engine? Does "turbo lag" mean that the car is slower on takeoff, but then blasts off enough to make up for it later? What is the "cool-down" period that is often mentioned with the turbo? Any and all input is greatly appreciated as I struggle to understand the turbo concept to decide which is better for me. Please keep in mind that although I love cars, I am not very mechanically inclined, so please give me the "for dummies" explanation. :-) Thanks so much.
SilverCrown
A turbocharger is pretty simple in concept. It's just an air pump that is driven by the energy from the exhaust gases leaving the engine.
The combustion process produces energy. About 1/3 goes to the crankshaft for engine power, about 1/3 into the cooling system, and 1/3 into the exhaust.
So on a 300 hp engine, 100 hp is going out the tailpipe.
You often hear that turbo power is "free" power, but this is not correct. There is power loss from driving the turbo (back pressure) and from heat...heat is the worst thing you want in the intake mixture going into your engine.
Turbo "lag" (the time it takes your turbo to "spool up" or get up to a speed where it's actually doing something, varies a lot depending on turbo design. Using twin turbos and/or turbos of very clever internal design is often claimed to greatly reduce most turbo lag., but really the best turbo is a large one. Twin turbos are efficient for certain types of engines (V-types) and for heat dissipation but don't necessary mean "more power" or "less lag"---all in all, you can't expect too much from any turbo if the engine isn't spinning very fast.
Water cooled bearings are a design feature that greatly enhances turbo life, and these designs are not so susceptible to "coking", which is a another term for excessive heat cooking and clogging up the lubrication lines and the bearing oil.
Last of all, (well, there's a lot more to say) many people want to know if a turbo decreases engine life.
Well, of course it does. You can't make that much extra power without paying a price. How much life is "lost"? Experts think maybe 10% would be a fair guess.
All things considered, turbos, if designed expertly, are a great way to make a car fun, fast and exciting with only modest drawbacks regarding reliability and fuel economy.
However, I'm still leaning toward the V6 model Passat as long as I can afford it. I like the idea of a quieter, smoother ride and more power (especially at takeoff). I'm intrigued enough to test drive them both and see what differences I notice and I wasn't willing to do that before.
Thanks so much.
SilverCrown
How does it relate to the initial acceleration? I'm assuming that it has something to do with the engine "twisting".
Please bear with me. School taught me theory, not practicality.
In the interest of preserving the last shred of sanity in our illustrious Host, I'll withdraw my question and place this in it's stead:
What's the difference between disc and drum brakes?
(the shoes are inside this drum and push out toward the rim.
IN disc brakes, instead of a drum we have a rotor, and a caliper with brake pads inside actually squeezes the rotor to a stop.
(You can see the caliper clamping down on the upper right of the rotor. The pads are inside.
A good way to see the superiority of disc brakes over drums is to grab ahold of a quarter.
First of all, hold the quarter with George's head in front of you, and your thumb on the bottom edge and your forefinger on the top edge. Now pull the quarter away with your other hand. Easy, huh?
Now, grab the quarter so your thumb covers George's face and your forefinger covers the eagle on the back. NOW try to pull it away. A lot harder, huh.
So essentially with disc brakes you get more surface area to grab, and because the caliper is in the airstream, and not enclosed by a drum, you getting better cooling, too.
Mr. Shiftright
The best way I can explain measurement torque is if you were to put a 1 ft long wrench on a bolt and put a 1 lb weight on the end of the wrench you are putting 1 ft-lb of turning force, or torque, on that bolt.
I take it Shifty that the disc brakes are more cost effective as well, not to mention easier to repair. Thanks for the pics and putting it in english!!
dpl: I think I finally got it now. I needed that refresher on the explanation of torque.
I think that's what was confusing everybody. You have to explain that the twisting motion is in the ENGINE.
P= is bmep, or brake mean effective pressure. It's the average pressure pushing the piston down the bore of the engine\
L = length of the stroke, or how far the pressure is going to push the piston down.
A = the area of the bore of the cylinder
So you can see how a turbo boosts the value of P, and how real POWER is actually torque x rmp.
HP = (P*L*A*N)/33,000
P = BMEP (Brake Mean Effective Pressure)
L = length of stroke
A = Area of piston
N = number of cylinders
According to Donna Wagner, president of the Car Care Council, "with the newer technologies on vehicles, people are starting to head more to repair shops to have work done." Other quotes in the article assert "the complications of trying to fix and diagnose..." and that most people "can't afford to buy a $3,000-$4,000 scanner to work on the car on weekends."
So here are a couple questions:
I'm curious to know what kinds of things some of you still do yourself, or not do anymore..., given all this new technology? Also, do you think this computer driven technology is creating a completely new breed of mechanics? After all, if diagnosing/fixing a problem is as simple as hooking something up to a machine, how much knowledge does one really need to have?
Okay, given that one still does have to have the mechanical know how to put something together and take it apart, it does seem like computer diagnosis/scanning eliminates the need for the kind intuitive knowledge that yesterday's mechanics used to require. Yes/no?
Thanks for your comments/responses to either one of these questions. ;-)
Revka
(formerly "pocahontas")
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Hatchbacks / Station Wagons / Women's Auto Center Boards
I had to comment on this one, I am not in total agreement with the article. I will expalin why and I'll try to be a short as I can.
The tips for finding a good shop;
People put too much emphasis on the certifications, that tells you very little except that a mechanic has passed a written test. I would be more concerned about what training the mechanic has had. Most countries do not use the certifications, some have govt licensing and others have manufacturer certifications.
I have seen certified Master techs that I wouldn't have change a lightbulb, let alone fix a car.
Friends, relatives and co-workers are going to be one of the best sources of recommendations. Remember, cheaper is not better.
Ask questions, lots of them of the shop you are going to think about dealing with. If they are willing to take the time to give you an answer that you understand, that will give you a fair idea of their capabilities. If they give you short curt answers, then you may want to look elsewhere.
The advent of the computer age has definitely brought a new breed of mechanics (some are offended by mechanics, they prefer techs)
I am a mechanic, some newer techs are lost without plugging into the computer and the push has been more toward replacing parts and not enough emphasis on diagnosis.
Also, the industry is having a tougher time getting new mechanics into the industry, as most younger folk prefer to go into the high tech industry and not get their hands dirty.
I know alot of shops that are having a tough time getting mechanics.
While they may have surveyed a number of people and places to see if folks were still doing their own work, I have found that if they can obtain the info, there are still a large percnetage of people that will do their own work. Some can't afford to take it to a shop. Some prefer not to take it to a shop, because of bad experiences, having to travel a long distance to a shop or because they like the feeling of the accomplishment.
The scanners. There are many quality scanner programs available and handhelds that will do a sufficient job with a good manual or systems information. This is all available at a reasonable cost. There is an on-line automotive information system - cost, $24.95/year per vehicle. Scanner program for laptop - cost $199.
Handheld scanner with monitoring capabilities - cost $199 to $389.
There seems to be a misconception among the mechanics cerifications and scanners.
People think that because a mechanic has the certifications, he knows what he is doing or that he is good. The certifications are written tests, they only prove that the person has read a book, prepared for the test and is good at taking tests. I have seen some of the best mechanics I've known repeatedly fail the tests, not because they were bad mechanics, but because they had problems with written tests.
The scanners and diagnostic tools, some shops and "techs" would like people to believe that they have to have the top notch expensive dianostic equipment to do basic repairs, that isn't so. There are techs, who firmly believe that no one but them are capable of repairs, these are some of the techs who tout their "Master" status every chance they get.
Ok, I rambled too long, just hit an area that I feel strongly about. I have devoted alot of time and money to helping folks with their automotive problems and this is an area that I have strong views on. Sorry.
One of my favorite cartoons: Mechanic looking at screen of HUGE computer hooked up to car with about 500 wires coming out of it. Screen says:
"OUT OF GAS "