23
votes
3answers
3k 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 ...
23
votes
3answers
5k 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 ...
23
votes
3answers
4k 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 ...
23
votes
8answers
151k views

Running with straight water as coolant in the summer. Is it fine?

I grew up flushing the coolant twice yearly. In the Spring, you drain the antifreeze and fill with straight water for the summer. In the Fall, you drain the water and put in a 50/50 antifreeze/water ...
23
votes
2answers
3k 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 and causes better handling. Why dont ...
23
votes
8answers
3k views

Static electric shock as I leave the car

Now this has started to "interfere with concentration". It is happening when i am getting out and trying to close the door. I feel a static shock as i touch the metal part of the door as my foot ...
23
votes
1answer
562 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?
22
votes
8answers
6k 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 ...
22
votes
11answers
168k views

What happens if a single spark plug unexpectedly goes down in a multi-cylinder engine?

AFAIK vehicle manuals say owner must replace spark plugs every N miles. Suppose he fails to do so and a single spark plug unexpectedly dies in an engine with multiple cylinders right in a freeway. ...
22
votes
4answers
4k 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 ...
22
votes
9answers
80k 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.. its got a 14mm head and its just plain STUCK. I've tried soaking it overnight ...
22
votes
3answers
2k views

What are these loops in the brake line for?

I was watching a show on the Velocity network about truck modifications, and I saw the following closeup of the trucks master cylinder and booster. What I don't know is why the designers put the ...
22
votes
9answers
152k 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 ...
22
votes
10answers
371k 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 ...
22
votes
4answers
9k views

Can a vehicle be harmed with bad inputs via an OBD-2 port?

I bought a cheap (sub $10) ELM 327 Bluetooth clone OBD-2 diagnostic adapter on a local "ebay-style" market where the seller specializes in car diagnostics and has several thousand positive reviews (...
22
votes
4answers
1k views

Are there requirements for building a car-PC and it's software?

I am currently rebuilding a car as a hobby. As a part of it I am planning on building in a car PC with custom software for some multimedia usage, navigation and some diagnose usage. I know there are ...
22
votes
6answers
26k 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 ...
21
votes
7answers
6k views

What's the point of servicing a car?

As you can probably tell from the question, I know almost nothing about motor vehicles. So apologies for my ignorance but I wasn't sure where else I might get this question answered impartially. ...
21
votes
4answers
4k views

Why do tyres go flat after a few weeks of non-usage?

My car is a 2007 model FIAT Albea 1.3 liter 4-door saloon. I think it might be the "fire" version. Made (assembled) in Turkey. I use it 6 months a year but 4-5 weeks at a time. When it's stored/parked ...
21
votes
4answers
2k views

How do you un-seize an engine?

I have an older engine that is seized. It is a 1953 Desoto Hemi. How can I un-seize it? I have sprayed Sea Foam Deep Creep down the plugs and let sit for weeks. As well as transmission fluid. To no ...
21
votes
3answers
1k views

Does a carburettor engine apply fuel at high speeds when the pedal is no longer depressed?

There's a question that is pretty similar to this one except the existing question satisfies EFI engines. EFI question Let's say I roll down a hill at a considerable speed I let go of the gas. Say ...
21
votes
2answers
1k views

Difference between OBDII and CAN

What is CAN (controller area network)? What are the differences between an OBD-II protocol and a CAN setup?` How do I use an OBD-II scanner on a vehicle with CAN?
21
votes
2answers
999 views

How To Read Car Tires

On my VW Passat B5 tires, there is a marking that reads "195/65R15 91 V". What does this mean? Do I have to get replacement tires with this exact marking on the side of the tire in the future or not? ...
21
votes
7answers
92k 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. ...
21
votes
4answers
229k 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 ...
21
votes
3answers
39k views

Is starting your car with the A/C on bad?

I was always yelled at by my father when I was first starting to drive when I left the A/C on when I turned off the car, and then later turned it back on, with the reasoning that I was ruining / ...
20
votes
11answers
58k 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 ...
20
votes
4answers
1k views

What are the benefits of a dry sump?

I've heard references to dry sumps, usually in reference to racing engines. But more recently I came across an article about a 'supercar' which stated that it had a dry sump. What are the benefits of ...
20
votes
3answers
2k views

Is it ok to use a scissor jack instead of a floor jack?

I need to jack up my car to take out the front driver side tire and change the p/s and alternator belt. I don't own a floor jack but I do have a scissor jack. I was wondering could I just use the ...
20
votes
6answers
1k views

Will higher octane fuel improve towing power?

According to Will higher octane fuel improve gas mileage? higher octane fuel does NOT notably improve fuel efficiency. Will higher octane fuel, increase power while towing? I looked online and ...
20
votes
3answers
1k views

How do I roll my 4x4 vehicle back onto its wheels?

I go 4-Wheeling A LOT with groups in Arizona. A slow speed rollover is a relatively frequent event. You just get a bit to much lean on the vehicle trying to navigate a difficult section of a trail ...
20
votes
2answers
2k views

Why do we need to cool air after it leaves a turbocharger?

When we are using a turbocharger to compress the incoming air, the air gets hotter. Usually this hot air is cooled by using intercooler before it is passed to the engine. But what is the reason ...
20
votes
2answers
1k views

What possible causes for the “check engine” light can I check for myself?

The "Service Engine Soon" light came on yesterday and isn't going away on its own. The car drives fine, no weird noises, smells, or other symptoms. The manual is not very helpful, just directing me to ...
20
votes
1answer
632 views

What does pie cut exhaust mean?

As the title says, when looking at building a custom exhaust system I've heard the reference called pie cut exhaust but I was unable to find any definition or terminology so I was curious to know what ...
20
votes
2answers
1k views

How exactly does a differential work?

I understand that the differential (or "diff") is the thing that allows the drive shaft to transfer its rotational velocity to the front or rear axle in order to move the car. As far as I know, the ...
20
votes
9answers
207k views

When do brake rotors really need to be replaced?

I need to replace my rear brake pads. A mechanic suggested I also replace my rotors because they are rusted around the edges. The rotors are in fact quite rusted, however, there is no rust on the ...
20
votes
4answers
22k 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 ...
20
votes
7answers
23k 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 ...
20
votes
3answers
56k views

Must I Replace All 4 Tires on an All Wheel Drive (AWD) vehicle?

I have a 2005 Subaru Legacy 2.5i Wagon. I just destroyed the passenger-side rear tire. The tires have approx. 6/32" tread remaining, per an informal measurement with a coin (I used this guideline ...
20
votes
2answers
184 views

Does (forcefully) overriding the self-canceling damage my indicator levers?

Sometimes I don't want my indicators to self cancel, so I hold the indicator on while turning the wheel, and it makes a cracking/clicking noise. Am I damaging anything if I do this? EDIT: To clarify,...
19
votes
9answers
50k views

Battery drains by itself when vehicle is parked (parasitic draw)

A 1998 Jeep Grand Cherokee has gone through 3 batteries in the last 3 months. While they have all been replaced by warranties, it'd be nice to get the problem solved permanently. I've tested the ...
19
votes
2answers
11k views

Why doesn't the engine stall out when you come to a stop with an automatic transmission?

When you come to a stop with a manual transmission you have to push the clutch in or take it out of gear to keep the engine from stalling out. What keeps the engine from stalling in an automatic ...
19
votes
11answers
188k views

How do I loosen stuck lug nuts in order to change a tire?

How do I loosen car tire lug nuts (so that I can change a tire) when they are really really stuck? I have tried turning the provided wrench, even standing and jumping on it. This worked for 4 of the ...
19
votes
7answers
3k views

Are manual transmission cars disappearing? [closed]

You don't have to be an expert to notice that over time, the percentage of manual transmission cars has lowered. Automatic cars are not only more popular, but more comfortable, easier to use and ...
19
votes
3answers
2k views

Should I replace fuses as a part of regular maintenance?

I've been having a few problems that might be electrical in my car. Seeing as mechanics always want to replace parts first, I'm having to diagnose this problem myself. It seems like replacing all ...
19
votes
7answers
62k 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 ...
19
votes
7answers
125k views

Is idling bad for your engine?

If I sit in my car for 30-40 minutes with the AC and the car idling, does that "hurt" the engine, or does it simply waste gas and pollute the air? Would it be better if I turned off the car? A ...
19
votes
4answers
2k views

Why would I want to measure torque while loosening a bolt or nut?

An answer to a question asking about torque wrench maintenance mentions to not use a particular kind of torque wrench for loosening bolts. This got me thinking. I would think it'd be preferable to ...
19
votes
3answers
1k views

What does under-square and over-square mean?

When building an engine, the terms over-square and under-square come up. What do these terms mean? How do they apply to engine building? Which is better for what purpose? Can you give examples ...
19
votes
6answers
15k views

What damage does a car suffer if not regularly used?

Sometimes I use the car on daily basis, but there are months when I don't use it at all, and it sits parked outside for 5+ weeks, with the battery disconnected. (Main reasons: working from home that ...

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