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29
votes
7answers
9k views

We have fuel injection, why not air injection?

I'm finishing studying EFI systems, which set me thinking about induction more generally. We inject fuel from a high-pressure common rail for many good reasons. We're capable of making stratified ...
29
votes
8answers
7k views

Why is engine displacement frequently a few CCs below an exact number?

I've noticed that engines are rarely exactly 1.5 liters or exactly 4.0 liters, and I'm okay with that. It makes sense that engines would have some arbitrarily ideal size for specific applications, so ...
29
votes
4answers
6k views

Why use snow tires on all 4 wheels on 2-wheel-drive cars?

In a car without four-wheel drive—if the car provides drive power on only two wheels—why put snow tires on all four wheels when the freeze sets in? Would it not be sufficient to change just the drive ...
29
votes
9answers
430k views

What is the difference between normal, platinum, iridium plugs?

What is the difference (besides price) between normal, platinum, and iridium spark plugs?
29
votes
3answers
376k views

what is difference between DOHC and SOHC?

I want to know the SOHC and DOHC configurations. On what factors an engine manufacturer decides to go with SOHC or with DOHC, what should I choose? DOHC or SOHC?
29
votes
7answers
17k views

When is a cold air intake system beneficial?

Cold air intake must be one of the popular mods there is, and one subject to the most controversy as well. Manufacturers of such systems advertise 5-20 HP gains, yet there are claims that this mod ...
29
votes
1answer
29k views

Why does the reverse gear in manual transmission cars sound different

When I got a manual transmission car (2003 Kia Rio) I noticed that it makes a winding sound in the reverse gear. Here is an example video that I found that demonstrates the sound. http://www.youtube....
29
votes
3answers
12k views

Static vs. Effective compression: Why does higher effective compression not require higher octane gas?

Background I've been trying to do a lot of research on boost lately because I'm planning on running a moderate turbo setup on my daily/light-duty-autox car in the future. I'm trying to get into the ...
28
votes
6answers
10k views

Do cars consume less fuel when in Neutral? [duplicate]

Imagine we're going down a hill and we're driving a manual car. There are two situations: If I put my car in neutral it will go downhill without any need for the injector to squirt fuel into the ...
28
votes
9answers
118k views

Will higher octane fuel improve gas mileage?

I've heard from some people that high octane fuel will increase gas mileage. Around here, we have the basic unleaded(87), mid-grade(89), and premium(93 or 91). I've been using the basic 87 unleaded ...
28
votes
2answers
15k views

Do I have an oil leak if I have to add oil?

I don't change the oil all that often (maybe every 8000 miles) and on my 10 year old car the oil light comes on and I need to add a quart or two (and then I start thinking I practically changed the ...
28
votes
2answers
21k views

Why do two-stroke engine exhaust pipes look so strange?

Two stroke gasoline engine exhaust pipes are shaped strange. They expand into a wide diameter and then shrink down to a very small diameter where the exhaust gasses emerge into the environment. - ...
28
votes
4answers
501k views

What causes an engine to burn oil?

What are the different problems that can cause an engine to burn oil and in general how difficult / expensive is each one to repair? How do you diagnose each potential cause? I found this article ...
28
votes
1answer
3k views

5-Stroke Engines - What are these things?

What is a 5 stroke engine? Why aren't they using them in vehicles right now? Is this a new thing or has it been around for a while?
27
votes
10answers
10k views

Top off gas with old oil, is that bad?

When I change my oil I don't like going all the way back to the station to drop off the old oil and I don't want to pour it in the river, so I put 17 gals of premium in my 18 gal tank and then top off ...
27
votes
10answers
682k views

How should I remove a paint scuff on my vehicle?

The painted edge of a side mirror on another car recently scraped the side of my vehicle, leaving a scuff of paint about half a meter long. There is no indentation or scratch, but the other vehicle ...
27
votes
2answers
3k views

How to deal with rust

I accidentally drove my car over a curb a while back. As you probably already know, the car suffered from minor scratches and dents on the bottom side, near the rear tyre. Now, I've noticed that it's ...
26
votes
7answers
4k views

“Fill nitrogen in tires” poster - are the claims credible or just hot air?

I saw this poster at a tire shop earlier today As the image quality isn't great, I'll reproduce the advert's claims in writing: Take the lead! Ride smart! [Nitrogen] for your SAFETY & ECONOMY ...
26
votes
9answers
261k views

Is it okay to leave a car for 5 months without driving it?

I need to travel to the east coast and work from there for a duration of 5 months. I can leave my car in covered parking here and ask a friend to start the car for a few minutes every week. What ...
26
votes
4answers
80k views

What are the Advantages & Disadvantages of a Boxer engine?

I know that boxer engines are those which have pistons moving in the opposite direction. Also the fact that since they sit low, the center of gravity is lower which causes better handling. Why don't ...
26
votes
10answers
48k views

Manual transmission at stop: 1st with clutch in, or neutral with clutch out? -OR- Throwout Bearing wear

When sitting in traffic or at a long red light, is the Best Practice to have the car in 1st gear with your foot on the clutch, or in neutral with your foot off the clutch? Some say that you should be ...
26
votes
4answers
476k views

What actually happens when there is way too much oil in a car engine?

I saw the answers to a question I posted recently highlighting the disadvantages of having too little oil in an engine, but that got me wondering what if the complete opposite were to occur! I know ...
26
votes
6answers
41k views

Is Start & Stop technology good or bad for my car? (Alfa MiTO)

I was recently in the lucky position to obtain an (almost brand new) Alfa Romeo MiTo, Progression. Like many new cars coming out these days, it has "Start & Stop" technology that turns the engine ...
25
votes
5answers
39k views

Is it really impossible to fix a seized engine?

I had an engine seizure that happened while I was driving the car: it ran low on oil and suddenly the engine stopped working (with a bit of smoke). Now after being towed, I have left the car (and ...
25
votes
11answers
9k views

How to get rid of a decal on the rear window?

I've bought a car which has ugly label glued to its rear window. What are inexpensive and effective ways to remove it without residue? Edit: my car has it on the outside on the blank glass but it‘s ...
25
votes
7answers
266k views

Is it safe to drive a car that has a broken suspension spring?

Yesterday I was driving home from work and heard a loud noise which I can only really describe as a "clang". After looking at it today, it looks like the spring for the front left (passenger side) ...
25
votes
11answers
188k views

What is the best way to remove a stuck/rusted exhaust bolt?

I'm trying to disassemble the exhaust system on a 2000-2003 Nissan Maxima and I'm having trouble removing one last bolt. It's got a 14mm head and its just plain STUCK. I've tried soaking it overnight ...
25
votes
6answers
133k views

Pros/cons of higher capacity car battery?

I'm shopping for a new car battery for a 1998 Subaru Outback (2.5l). For the physical dimensions, the battery has to match. But I see some variance in capacity (Ah) rating, and in price too, of course....
25
votes
9answers
360k views

What's the point of the D3 gear in an automatic transmission?

My Honda Civic has a D gear and a D3, which apparently prevents it from going into 4th. Why would I want to do this? What is it good for? Does it make my fuel efficiency better or worse? Does it ...
25
votes
6answers
210k views

What are the risks of overfilling a small engine with oil?

I recently overfilled a 4 stroke lawnmower engine with oil. It has been run for about 1.5 hours while overfilled. It smokes a lot right after being started but after 30 seconds or so the smoke clears. ...
24
votes
8answers
8k views

What is my friend's wife not telling him (about this tire)?

So a friend of mine sent me this picture of a "blow out" that happened on his wife's car (some Infinity coupe). She said that it just happened all of a sudden with no warning. She says she pulled ...
24
votes
4answers
10k views

Is the driver's door supposed to unlock from inside?

I have a Toyota Corolla. The driver side door opens from inside even when the door is locked. The door doesn't open when opened from outside. Is it normal? The only possible explanation that I can ...
24
votes
7answers
9k views

Why could my vehicle be shaking around 60mph after hydroplaning?

Yesterday, I was driving home in a storm and I ended up hydroplaning. My car, Hyundai Elantra Coupe 2014, spun a 360 landing me in the dirt on the side of the road. Luckily, no one was driving by me ...
24
votes
2answers
6k views

Strange metallic stickers on rims after repair shop visit

These appeared on my rims after taking my bike to a repair shop. Does anyone know what these are and how to remove them?
24
votes
11answers
4k views

What emergency gear and tools should I keep in my vehicle?

Apart from the mandatory emergency gear that should be in cars (early warning devices, fire extinguishers, visibility vest, first aid kit) what other tools should I get? Flashlight Gas Container ...
24
votes
3answers
8k views

Why does a gas engines torque and horsepower curve always meet at 5252 RPM?

I'm watching a TV show called Tech Garage and they just made the claim that an engines torque and horsepower curves always meet at 5252 RPM. Assuming this is true, why does this happen? Is it ...
24
votes
5answers
140k views

Why should the fuel petcock valve be turned to “Off” position when not using the vehicle?

It’s mentioned in the user manual of my motorbike, that when not using the vehicle, I should turn the petrol tap (the one that has three positions “On”, “Off” and “Reserve”) to “Off” position. I don’t ...
24
votes
4answers
375k views

Symptoms of Lean or Rich carb settings on a motorcycle

I have a 1981 Yamaha XS650. I recently put in K&N stock replacement filter (ie, they are in the airbox and conform to the size of the original), however they may be leading to a leaner mixture ...
24
votes
4answers
7k views

Will engine braking damage my transmission? How can I tell?

I drive a manual transmission '08 Honda Fit. On my daily 17 mile commute to work, there are three long hills that I can coast down, each about a half mile long. Going down these hills, I've done two ...
24
votes
3answers
16k views

Why do pickups and large SUV's use 4x4 and generally not AWD?

In almost every case I can think of, the larger vehicles with four wheel power are 4x4, and the smaller ones AWD. As far as my experience goes, AWD is much more convenient, and also works at least as ...
24
votes
4answers
58k views

Why do cars die after removing jumper cables?

I work at an auction site where we have to move cars from one spot to another. Often, we get a car with a dead battery that we have to jump. I've noticed that if the jumper cables are removed a ...
24
votes
4answers
33k views

What are the benefits of low profile tires?

I have yet to find anyone that knows of any benefits of low-profile tires. All of the pros that I've asked have said there is no benefit. Naturally, the number of pros that I have available to ask is ...
24
votes
6answers
151k views

Clutch less shifting - why does it work? Is it bad?

I have been driving stick for 15 years and within the last year I learned I can shift gear without the clutch. Normally the transmission will not let me shift gears without using the clutch. However,...
24
votes
9answers
89k views

How old is too old for a new tire?

When shopping for new tires from tirerack.com, the production date of the tires is listed. I'm considering tires from a 2007 production run, which would make them around 5 years old today (after ...
23
votes
3answers
8k views

If I am just replacing the car engine, do I need to replace the odometer as well?

I am considering getting a new engine for one of my cars and I was wondering if I'll have to change the odometer too. Since the car already has 220,000 miles on it, it would become a huge number if I ...
23
votes
8answers
5k views

Are tyre repair kits a viable alternative for a spare wheel?

I would REALLY like to get rid of my spare wheel. The wheel is heavy and I need the spare wheel well for... other purposes. In my history of driving I never had to use the spare wheel, so it cost me a ...
23
votes
13answers
22k views

My car has moisture on the inside of the glass but other cars do not

During winter here in Canada, my 2011 Cruze seems like it has humidity on the inside of the windshields. When I take a look at other cars besides mine, there is moisture on the exterior, not interior. ...
23
votes
10answers
93k views

How can you tell the oil needs to be changed?

I know oil should be changed every 3000 or 6000 miles (depending on the car and conditions) but I'm not all that great at keeping track and I've let the car go for 10,000 miles before and it still ...
23
votes
4answers
9k views

Small amount of wrong fuel type put in the tank

The guy who works at a gas station was filling up for brief moment wrong fuel type in my car until he realized what he did. I own Citroen Xsara 1.9d, make year 2000. Before filling the tank which is ...
23
votes
4answers
12k views

How do I test my car battery?

My car still starts fine but when I turn off the car (just the motor . . the key is still in and "on") I noticed the headlights dim to almost off. It's and older car and the headlights don't turn off ...

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