Archive for the ‘Car Engines’ Category
Before you sell, find out the approximate correct value of your used car-
Are you thinking of buying a new or a second hand used car? But if you already have an old car, you can try trading it for a new or used car now. Avoid unnecessary troubles of selling it all on your own. But whatever you do, firstly it is vital to know the accurate value of your car before you go ahead and sell it.
What are the three different values of a used car?
There are basically three values of a second hand used car-the private party price, which is the price which two dealers might negotiate to buy the car; the trade in price which is the least amount which the dealer might be willing to pay for the car and last the retail price in which the dealer might sell to another potential buyer. The trade in and the private party values are the ones which is all you should worry about.
Check the condition of your car in order to price it well-
The most vital step while selling your car is finding out the condition of your car as that is what will determine the cost of your car. You can then easily expect to know how much the retail price will be. Be straightforward with yourself and pursue the minimum guiding principles. By understanding the needs and conditions of your car, by following the rules and guidelines, you can now price your car. Ask a mechanic to check out your car so that you can know the damages and problem areas of the car. You can not buy or sell a used car without knowing how much damage is there. If you do not trust a mechanic ask a friend or relative who is well informed about cars or its parts. You can also always check online for details about car parts and second hand cars’ pricing.
No matter how old it is your car, which you are about to sell should be in great shape. It shouldn’t look shabby or ridiculously damaged or broken from the outside. It is very vital to remember that a good impression is made by the first look itself. Make sure that the tires have no uneven patterns and all four are matching! The paint should be more or less flawless with the least amount of scratches or chips. It will be better if your car has no dents at all. Your car should also clear all state and local car inspections. Do some minor touch ups if needed. The interior of your car is also very important. It should be clean, it should not smell damp or bad, the seats and seat covers should not be torn and rattled. Have your maintenance bills, records, etc ready at hand. The more paper work you have the higher will be the value of your used car. If you are sure that all this is alright, then your car can easily pass the examination.
Car Engine Modification
In order to get every last bit of performance and horsepower from your vehicle, you’ll require investing in some modifications. As modifications like wing spoilers, body kits, aftermarket breaks, and performance wheels all of these gives performance benefits to your car; merely setting up your car engine to the fullest will assist you to produce the horsepower required to increase your car over the rivalry down the strip or the street. The following are several well-known ways in how to modify the engine of your car and obtain the performance that you want badly:
• High Performance Radiators – An engine with high performance gives added power, and, as a result, added warmth. This radiator will be required to maintain its coolness. These radiators are made to manage a lot of pressure ranges and higher temperatures compared to OEM radiators. These will assist in keeping your engine performance protected from running smoothly and overheating regardless of anywhere you run your vehicle.
• Cold Air Intake – This can increase and boost the performance of your car engine by a considerable amount. OEM intakes pull in warm air from just about the engine bay, which reduces the capabilities of the performance of your car engine. By supplying a cold stable stream of thick air, the intake of cold air can provide you improved ignition, which provides additional power per stroke, zooming you down the street with superior pleasure.
Turbos and Superchargers -These could boost the performance of your car’s engine to a deliberately superior level. Each method provides unlike benefits, and so it will require choosing the one that is right for your requirements. For example, a supercharger provides enhancements in the performance across a broad array of the power band. A turbo, alternatively, offers a performance greater at superior ranges on the RPM (on the whole, a supercharger is immense for the street, while a turbocharger is perfect for the track).
• Custom Ignition System – This can work wonders for your engine. High-tension wires and spark plugs performance could put in horsepower into your engine. Additionally, timing that is advanced could also give you a push that is greater. Performance wires and plugs give more sparks; this is what drives the pistons and ignites the fuel inside your engine. When put together with the intake of cold air benefits, this system of custom ignition will provide you enormous boost in performance.
These are only a small number of car engine modifications that you’ll be capable of doing consecutively to make the most of performance and power. Having the exact tools and a bit of assistance, you can increase the performance of your engine to unbelievable heights.
Crage Engine – Muscle Car Engines
Muscle cars hearken back to a simpler time when automobiles were big and bad. They still attract a following of automobile aficionados and enthusiasts who love these sorts of cars. Unfortunately, the parts on these cars fall into disrepair. Even more unfortunately, the models of engines eventually fall from favor. But fortunately, these engines are reproduced by companies. These are known as known as a crate engine.
These engines are sold as standalone units sold without the car. They are commonly used to replace the engine in classic cars that are still being driven and kept up by car enthusiasts. Crate engines can also be used to make an older car more fuel efficient and drivable on a day-to-day basis. As many of the manufacturers of these cars have gone out of business or no longer make them regularly, oftentimes smaller boutique firms have stepped in and make the replacement engines.
Usually one built with different materials than the original. An engine made of aluminum rather than the original iron can be a lot less heavy and will cost less than what an authentic model would run. Still, replacements are not cheap. They start out at the $4500 range and go upwards from there. The fact that some classic cars can sell for upwards of 6 figures puts the price in some context. Needless to say, classic car rebuilding is not a hobby that is taken up on the cheap.
Crate engines are not something that a person will pick up at the local Wal-Mart or even GM Good wrench. This is something that is going to be specially ordered, oftentimes through a store that specializes in these motors. A quick search of the Internet will reveal a number of these stores online. Also automobile clubs can be another great source of information for those willing to sit back and listen to rebuilding tales. Of course, people who are into classic cars enough to invest in a crate engine are the same types that enjoy the building of the car in the first place.
These replacement engines can help to keep alive the memory of a simpler time in automobile history. Though not inexpensive by any means they can be ferreted out for a muscle car that has languished in auto purgatory and is waiting for the chance to roam the highways as it did so many years ago.
Maintaining New Car’s Engine Compartment
Your new car’s engine compartment is as important as the smooth appearance of your exterior. Make sure to regularly maintain the engine compartment to avoid costly repairs and replacements, and be assured of a longer engine life and an excellent performing car.
Modern cars have cooling system components that are being forced to do more than the older ones. This is because of the trend to downsize car parts in order to minimize space and weight. To maintain your cooling system’s peak of efficiency, the most appropriate thing to do is to alter the coolant once every two years. Remember that anti-freeze does not wear out. Also, by altering the coolant, you are ensured that the corrosion inhibitors are fresh and doing the job they are supposed to. By maintaining your car’s cooling system, you are assured of less scale and corrosion that builds up inside the radiator when coolant is left in too long. Of course, you can also definitely avoid the high cost of radiator repair or replacement.
The brake fluid is the most important engine component. It is not a petroleum-based product; as a matter of fact, it is made up of cashew shells. They absorb moisture from the air. As a result, it minimizes braking performance. A substance also builds up over a period of time. In effect, this blocks the valves inside ABS units. The end result is no less than costly repairs or replacement. This blocking substance also causes calipers and wheel cylinders to leak. Thus, it results in repairs or replacement. So better flush the brake fluid and have it refilled every two years or 60,000 miles. Power steering fluid also needs to be flushed and refilled once every two years or 60,000 miles.
Another fluid, the transmission fluid, requires regular replacement so that it is kept in a tip top shape. Lack of maintenance is the main cause of transmission failures. To prevent costly repair and replacement, make you work done regularly.
Air and fuel filters prevent dirt from your engine. But their function does not mean they do not require cleaning anymore. Junky air and fuel filters result to several driving problems such as hesitation and rough idle stem. To avoid problems like those, replace the filter every 15,000 miles. The carbon canister filter, which is a very vital component of the emission control system and filters the in coming air, should be replaced. The emission controls are integral parts of modern engine management system. Keep in mind that a blocked canister filter will also result to drivability problems.
A PVC filter is only common to some cars. It is also known as a breather element. The air for the PCV system is filtered by this engine part. The dirt from the engine crankcase is also kept out by this PVC filter. It needs to be replaced at 15,000 mile intervals.
While checking your PCV filter, also check the PCV valve and replace it regularly. When a new PCV filter is installed, a new PCV valve must also be installed.
Also include the oxygen sensor in maintenance. It measures the proportion of oxygen (O2) in the gas or liquid being analyzed. Usually made with zirconium ceramic bulb coated on both sides with a thin layer of platinum, this sensing element comes in both heated and unheated forms. Its main task is to measure the performance of internal combustion engines in automobiles and other modes of transportation. If you see any damage in your Dodge car’s Dodge oxygen sensor, consult the owner’s manual to prevent further vehicle damage.
The spark plugs together with the other ignition parts are engine components have become much more reliable since the age of high technology began. Most modern engines use a DIS or Direct Ignition System. This system mounts one ignition coil on each spark plug. This minimizes the need of a distributor. Also, the PCM controls the firing of each coil.
Nonetheless, distributors still exist in some engines. On engines that still use a distributor, replace the distributor cap, distributor rotor and ignition wires every 30,000 miles.
On a regular basis, replace the spark plugs. In the auto shops are platinum plugs, split fire plugs, multi-electrode plugs, red ones, green ones and blue ones. But you must only opt for the recommended one of your manufacturer. Usually, spark plug information is located on the engine decal under the hood.
The most crucial part of the engine is the timing belt. It is so crucial that it needs to be replaced before it breaks. If your vehicle has an engine whose valves and pistons are located in the same place in the combustion chamber at different times, it implies engine damage. If your car uses a non-interference engine, you might experience a car breakdown. So to avoid this, replace the timing belt every 60,000 miles.
Each engine part is essential for your engine, in particular, and your car, in general. Never take even one part for granted. This is to avoid untoward car breakdown. Moreover, the engine is the one that makes you car work. Your new car’s engine compartment is must at all times work properly because that is the heart of your vehicle. Well maintained engine parts will give you your desired car performance.
Build Hydrogen And Water Engines – How To Run Your Car on Water
Are you interested to find out more about hydrogen and water engines, and how you can have your own too? I know that till today, many people are skeptical about the idea of cars being able to run on water, and it is no surprise because this technology is almost unheard of.
It seems almost impossible that water can generate enough energy to power a car. So why are there rumors of people running their cars with water?
1. Can Cars Really Run On Water Or Hydrogen?
Because I was skeptical yet curious at the same time about this water fuel technology, I went ahead to buy one of the more reputable water powered car guides on the internet, and how I wished I had discovered this technology earlier.
It is not true that an automobile can be fully powered by water. That is a myth because you will need huge volumes if you want to power your car 100% with water. However, you can certainly run your car with a mixture of gasoline AND water. Even better, this system can be created at your own home without having to buy a brand new hybrid car or an expensive hydrogen car kit.
With this technology, drivers can finally escape from the huge burden of rapid rising fuel costs, and save up on the amount of gasoline they have to purchase over and over again.
2. Why Are So Many People Using Water To Run Their Cars?
The gas that is extracted from water called Brown Gas (HHO), burns much cleaner and has less damaging effects on your car engine. Using gasoline in your vehicle engine wears down the mechanics and engine parts in your car quickly. Users who have tried this system also reported an increase in engine life due to less wear and tear.
3. How Does This System Work?
For this system to work, water needs to be split by electrolysis to obtain the HHO gas. Since water is made up of H2O, it has the necessary elements of this gas. Brown Gas has been proven to be three times more powerful than gasoline and also burns more cleanly.
4. Conclusion
If you wish to use this hydrogen water technology, you should download an instruction manual from the internet to learn the exact steps and see diagrams of the setup process. Hopefully you have got a new perspective on water engines, and understand why people are choosing to use water over gasoline.
Car Engine Tune Up and Maintenance That You Can Do by Yourself
Treating your car to both regular and major tune ups will certainly improve its performance, prolong the life of its engine and dramatically increase fuel efficiency. With today’s constantly increasing fuel prices, it pays to keep your engine in top condition to minimize gas consumption.
Major engine tune ups can be pretty expensive when done by the dealer. It will be more practical to get to know a mechanic who owns a garage to ensure you won’t get ripped off. Or you can perform a do it yourself tune up and maintenance of your car’s engine. Here are some basic tips.
Ignition and electrical systems
Inspect your car battery levels four times a year at the very least, at each season change. Top off low levels with distilled water. Remove corrosion from cable clamps and terminals by using a wire brush and a little baking soda. This practice will extend battery life.
Spark plugs should be replaced every 35,000 miles, or if they’re platinum, replacements are required every 65,000 miles. Check the spark plug for cracks and corrosion and change them if damaged. Get high quality cables for added durability and reliable performance.
Get a new distributor cap with each major tune up, if the cap is not attached permanently to the spark plug cables. Also replace the rotor of your distributor, if it has one, as some new model cars don’t have either a distributor cap or a rotor.
If your car is a 1978 model or older, replace the contact points and condenser. Newer car models have electronic ignitions and don’t require condensers or contact points. Contact points should be aligned or replaced two times a year.
Oil and fuel systems
Unless your car has hydraulic valves, adjustment of valve covers is a necessity. While you’re at it, also replace the valve cover gasket. If done properly, this will prevent oil from leaking out on top of the car engine.
Inspect the timing belt and readjust or replace it if needed. Electronic ignition-equipped cars don’t often come with timing belts, while some do, so you have to be certain.
Inspect the fan belt and other belts. If they are cracked, frazzled or worn out, consider replacing them at once.
If your car has a fuel injector, you don’t need to clean it regularly. Clean it only if it gets clogged and use only clean fuel bought at a gas station. The fuel filter needs to be changed every 35,000 miles.
The air filter has to be replaced every 15,000 miles, or if it is already covered with dirt. Keeping your air filter clean ensures a more efficient fuel burn, thus minimizing gas consumption.
Brakes and clutch
If your car has a manual transmission, the clutch will require certain adjustments. Newer model cars are now equipped with adjustable clutch. Consult you manufacturer’s manual to be certain.
Oil, brake and transmission fluids should have their levels checked every week, or before and after long drives. Have an oil change and oil filter replacement every 3,000 miles as having clean engine oil prolongs the engine’s life.
You can do your own tune ups to increase fuel efficiency, gain better engine performance and offer a smoother ride. This is not an assurance that you won’t run into any car troubles, but do it yourself car tune ups will save you a lot of money in maintenance and repairs.
Understanding Your Car’s Engine Control Unit (ECU)
These days, you will find new cars with the latest incorporated engine technology. The engine of a car has undergone a massive change, right from the age old carburetor to the Engine Control Unit (ECU). In the 19th century, when the first single-cylinder petrol engine driver car came into force, it was the “Carburetor” that came into existence. Later on, multi cylinder engines were considered as a new thing. Finally, in the early 80’s we got a new car system, consisting of controlled – feeding of fuel, air and ignition spark to the ICE cylinders. It was the fuel-injection system that was born, which replaced the century old carburetors. In a multi point fuel injection system, it injects fuel into individual cylinders. The injection of the fuel takes place on the basis of the commands from the “on board engine management system” computer. This computer is known as the engine control unit or the ECU.
The main process based job of an engine control unit (ECU) is to control the various features of an internal combustion engine’s operation. Earlier, the ECU that was fitted in most of the cars and had their engine parameters fixed. Also, the carburetor would determine the required quantity of fuel per cylinder/per engine cycle. In other words, the simple version of the ECU’S would control only the quantity of fuel injected into each cylinder, at each engine cycle. The advanced types of engine control unit (ECU), which are fitted on most modern cars, are capable of controlling the ignition timing, variable value timing (VVT) and other peripherals.
The ECU’S (Engine control unit) monitors the engine by using sensors so that it can gather information about the cars quantity of fuel, ignition timing and other such parameters. The ECU works according to the input data that it gets from the various sensors that are located within the engine. The various types of sensors that are fitted all over the engine are MAP sensor, throttle position sensor, air temperature sensor, oxygen sensor and many more. The sensors incorporated within the engine, are basically used to determine the various “operating states of the engine and its performance. These sensors monitor’s various aspects such as the ambient air temperature, engine/coolant temperature, exhaust /main fold temp, exhaust O2 content, throttle position, the rpm of the engine, the vehicle road speed and crankshaft position. The ECU (Engine Control Unit) uses the closed -loop control method, where it monitors the output of a system in order to control the inputs to a system. Since, the ECU (Engine Control Unit) gathers data from various different sensors, it knows all about the coolant temperature to the amount of oxygen in the exhaust. On the basis of this available data, the ECU (Engine Control Unit) starts performing huge calculations every second. On the bases of the programmed interpretation of all the available input data, the ECU ( Engine Control Unit) will deliver the required commands to the engine’s fuel intake and spark ignition timings system and thus help in bringing out a satisfactory performance of the car’s engine.
Restoring a Car Engine? Use an Ultrasonic Cleaner
There’s something magnificent about a beautifully restored antique classic automobile. One look under the hood of a 1930 Model 734 Packard Rumble Seat Roadster or something like Amelia Earharts’ 1931 Reo and you have to think, “They sure don’t build them like that anymore!”
While many of us can’t afford the classic cars of the 1920s or 30s there are those who like to work on old engines, coaxing new life into a recalcitrant block of 4, 6 or 8 cylinders as part of our own auto restoration project. Since it has to run to have worth, an automobile engine is usually first to be tackled. An ultrasonic cleaner is the best friend a restoration fanatic can have for a project like this.
Ultrasonic cleaners are widely used to clean engines of most any size and shape. They replace the old-fashioned solvent degreasers used in neighborhood garages of yesteryear. Perhaps you recall seeing mechanics holding engine parts under a faucet and manually scrubbing away grit, grease and grime as the solvent is re-circulated through a filter-equipped holding tank.
Now mechanics place disassembled engine parts in an ultrasonic bath. Yes, we’re talking carburetors, fuel pumps, oil pumps, pistons, connecting rods, crankshafts, camshafts, bearings, all the various gears, chains and components that together comprise an internal combustion engine and for that matter, transmissions and differentials too. The magic of cavitation does the work faster, much more efficiently and safely than any amount of hand scrubbing in a volatile solvent.
Why an Ultrasonic Cleaner Cleans so Clean
Like the old solvent cleaning system an ultrasonic cleaning system consists of a tank that holds the ultrasonic cleaning solution. Biodegradable and safe, the solutions usually come in concentrated form and are diluted to manufacturers’ specifications. Along with the tank an ultrasonic cleaner consists of an ultrasonic generator and ultrasonic transducers that are firmly attached to the bottom or sides of the tank.
When the unit is turned on the ultrasonic transducers create billions of microscopic bubbles in the cleaning solution. Engine parts are placed in a mesh basket, on a rack, or otherwise suspended in the solution and the cleaning cycle begins as the bubbles implode with tremendous force upon contacting the parts. Dirt, grime, grease, carbon deposits – all contaminants are stripped off of the parts without damaging them.
So tiny are the cavitation bubbles that they penetrate cracks, crevices and blind holes – areas impossible to reach by manual scrubbing.
At the end of the cleaning cycle parts are removed, rinsed and dried. A rust inhibitor is applied and the parts are ready for reassembly.
Operating Tips
Because it contains air, fresh ultrasonic cleaning solution should be degassed by letting the cleaner operate in a degas mode for at least 10 minutes before immersing the parts into the solution. This is because air bubbles interfere with cavitation action and slow the cleaning process.
Oils and residues that rise to the surface should be skimmed off and safely recycled. Filters can trap other contaminants and should likewise be safely disposed of. Used biodegradable solutions can be disposed of in sanitary drains. The tank itself should be periodically cleaned according to manufacturers’ recommendations.
Car Engine Does Not Crank Over – Auto Repair Tips
I remember years ago a customer of mine called because she was stranded at McDonalds. Her car wouldn’t start, it wouldn’t even crank over. Luckily I was only about five minutes away and was able to drop by to check her car for her. The battery terminals were after-market, the type that has two 7/16″ bolts that clamp over the bare cable end. These are a quick easy repair for the battery cable but sometimes they do loosen over time. That was exactly what had happened in this case. I was able to just tighten the terminals where they clamped to the bare cable ends and she was on her way.
A car that doesn’t turn over at all, usually has a battery related problem. Many cars are towed to auto repair shops every year due to loose or corroded battery terminals. If the car engine doesn’t crank over at all, the first thing to check is the battery and terminal connections. Here’s a quick auto repair tip, turn the lights on and try the horn. If the battery is any good at all this will be a quick preliminary check. If there’s no horn and no lights, try wiggling the battery connections. I leave the lights on while trying this so I can tell if I’m making a better connection when moving the battery terminals.
Still no luck? A load test with a battery tester is the next step after checking the connections at the battery. Many times a battery will show signs of failure by turning the engine over slowly when it’s beginning to fail, this is an early warning to have the battery tested. Unfortunately other times batteries will just fail with no prior warning. Temperature changes can sometimes reveal a problem with a battery that otherwise may go unnoticed. An increase or decrease of temperature will typically send cars in droves to the repair shop or parts stores with sluggishly starting cars. Batteries will need to have a good charge before they can be properly tested. Modern battery testers will indicate if the battery has a sufficient charge to be checked.
Alternators that are not charging properly can cause a car to have similar symptoms. It’s always a good idea to check the alternator to make sure the output is within the manufacturer’s specifications. The parts store or auto repair shops have the test equipment to check the alternator output for you. They will check the amperage, volts, diode pattern and check to see if the alternator has a draw or short that may be excessively draining the battery.
Starters can draw excessive amps or have an open circuit completely. After checking to make sure a good battery is installed, check the big cable connection at the starter which is the 12v one that comes directly from the battery. Then check at the starter solenoid (the small wire) to see if it is getting power when the ignition is turned to the start position. If power is going to the starter solenoid but the starter is not engaging, more than likely the starter has an open circuit or is binding. Sometimes the starter can be tapped with a hammer while the ignition is in the start position to get the car to start. This is basically to get the car into the shop for starter replacement. I’ve used this trick many times over the years to keep from having to push the car into my service bay. The starter can also be tested to see if it is creating too much of a draw on the battery. This can happen when the starter begins to to drag or bind and puts too much of a toll on the battery. The amp draw is measured with a battery and electrical system tester to see if it is excessive.
My tips and tricks have been picked up over the years with real hands on experience. Many auto techs don’t like to share their techniques, but I’ve been selling tools since 2005 and it’s time to share what I’ve learned during my time as a Master Automotive Technician. I hope my article helps many people to figure out what’s going on with their car and just maybe help prevent them from being stranded.
How to Inspect an Engine When Used Car Shopping
When shopping for a used car you should make an appointment to view a car for sale and specifically request that they do not have the car started or warmed up until you get there. When you arrive you can pop the hood and feel the engine temperature by placing your hand on or near the block which is the main component of the bulk of the engine. This large piece of metal will retain heat for hours after warming up. If the engine is still warm consider coming back another time or moving on to the next prospective car.
Starting a car from a cold start is critical in helping to gauge the condition of the motor. Difficulties in starting, or weak cranking or funny noises are all indications of systems in the engine which are no longer running optimally. Still, before you even want to start the car you need to do a complete inspection of the fluids in the engine.
The first thing to check is the engine oil. To get an accurate level reading the car must be parked on a flat and level surface and it is best if the car has been parked overnight and not running. The oil that is on the dipstick when you remove it should be amber in color and mostly translucent. The darker and more gritty the oil the worse the vehicle has been maintained. The level of the oil is also important as this will tell you if the car is leaking or burning oil as well as tell you a little about the maintenance history of the car. Ideally the oil level should be to the full line indicator on the dipstick.
You should check for oil leaks by inspecting visually the underside of the engine. If there is an oil leak it will be very apparent in the caked on grease and road debris stuck to the underside of the car. If there is not you will need to watch for burning oil. If the oil level is low it has to be going somewhere.
Another fluid to check is the radiator fluid. For safety, the car must be completely cold before you attempt to open the radiator cap. The fluid in the radiator should be clean and clear despite usually being green. What you do not want to see is oil, debris or nothing. If you are comfortable working around cars and radiators you can start and run the car with the radiator cap off. If you have bubbles like a rolling boil when you rev up the engine then the car likely has internal failure in the form of lost compression in the engine escaping through the usually isolated cooling system.
There will likely be a brake fluid reservoir mounted to the firewall of the engine compartment. This would be the brake assist system and also may be utilized for hydraulic clutch assist in some vehicles. This fluid should be clear and mostly transparent. A leak in the braking master cylinder will manifest itself as a loss of brakes eventually but will start by visual fluid loss from the master cylinder.
All belts and pulleys should be in good physical condition free of cracking or worn edges. The wiring in the engine compartment should look clean and neat. Any signs of random wiring or messy wires is an indication that under-qualified hands have been working on the engine.
When you start the engine it should crank over, fire, and find a smooth and steady idle easily. Any hesitations, backfires or irregular idling are a sign of engine problems. Not all engine problems are serious and many can be simple such as a vacuum leak. Still it would be preferable to find a car with a great sounding and looking engine.
Smoke from the tailpipe will be burning oil, burning coolant or unburnt gasoline in some cases. Coolant burns white and smells like burning maple syrup. Oil burns blue/white/grey and can also be visible coming from the engine oil dipstick if you remove the dipstick while the engine is running. The term for this is “blow-by” which refers to engine oil blowing by piston rings which have become worn with age, heat and friction.