Internal Combustion Engine. Most engines in road going vehicles are 4-cycle internal combustion gasoline engines.

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29
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9answers
5k views

What actually happens when there is not enough oil in a car engine?

When a car is topped up with oil, it clear to most people that you are supposed to fill it to the recommended amount as specified by the manufacturer (normally on a dip stick). What exactly are all ...
26
votes
9answers
40k views

Is it necessary to 'burn in' or 'break in' a new car?

I've just bought a new 2011 plate car. I've heard stories of people 'burning in' engines for the first few hundred or couple thousand miles using methods such as: Not driving above 50 mph. Varying ...
23
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1answer
1k views

Why are the blades of old car radiator fans unevenly spaced?

Fans that look like this: Is it to somehow help the balance of the engine?
22
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1answer
2k views

Changing Firing Order in a 4 Cylinder Car

Backstory In motorcycling you can get cams that change the firing order and time from a traditional 1,3,4,2. It's was very common in American roadracing in the 1990's to hear 4 Cylinder engines that ...
21
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3answers
96k views

What does a water-like drop coming out of the exhaust of the car signify?

Sometimes while driving in the traffic, I come across a car or two which would be dripping water-like drop from it's exhaust steadily in a break of 4-5 seconds. I tried to ask a couple of people at ...
19
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3answers
6k 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 ...
19
votes
2answers
1k 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. Why ...
19
votes
6answers
21k 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 ...
18
votes
2answers
26k 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 / ...
17
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11answers
140k 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. ...
17
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 ...
17
votes
7answers
88k 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 ...
17
votes
7answers
64k 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. ...
16
votes
2answers
10k 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 ...
16
votes
2answers
937 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 ...
16
votes
4answers
25k views

Driving in second gear at 65+ mph

I accidentally drove my 2000 Grand Marquis on second gear on the highway. I was going 65 for like 5 minutes and tried to get it to 70mph but the car was shaking, when I realized I put it into regular ...
16
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1answer
187 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?
15
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1answer
342 views

What is the difference between a 180° V4 and a true boxer motor?

Reading this thread which talks about V4 motors, I am wondering what exactly is the difference between a 180° V4 motor you'd find in a Subaru and a true boxer (or horizontally opposed) flat 4 ...
15
votes
5answers
30k views

Is it OK to mix oil of different viscosity in a Wankel engine?

I have a Mazda RX-8 (with a Wankel rotary engine). Mazda advises North American owners to use 5W-20 oil. The engine was just replaced 200 miles ago by the dealer so it currently has 5W-20 in it. ...
14
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 ...
14
votes
4answers
809 views

When does it make sense to replace a camshaft?

Preamble (Rant) I was reviewing this question in which the OP presents a repair quotation that includes replacing the "intake camshaft" to fix an engine that had overheated. To me this ...
14
votes
8answers
25k views

My car's coolant temperature reaches almost 100 C / 212 F in a fast pace

Today, after a very hot day, I saw that my coolant was almost reaching 100C/212, I pulled over, stopped and took a look over the hood. The very little water that remained in the coolant tank was all ...
14
votes
4answers
35k views

Why does a Turbocharger only produce boost when the engine is under load

As per the Title. Why does a turbocharged car only produce significant boost whilst the engine is under load. Is is something to do with how much exhaust is being produced or is there some kind of ...
13
votes
4answers
27k 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?
13
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1answer
3k views

What is happening when a two-stroke engine is said to be “four-stroking”?

Many years ago, I was involved in a hobby of building and flying model aircraft. The aircraft used alcohol-fueled 2-stroke engines with glow plug ignitions. When these engines ran rich (and always at ...
13
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1answer
8k views

Is this what is making my car sound like a racecar?

Recently, my car (2000 Mercury Grand Marquis) started sounding like a racecar: the engine became very loud. There's clearly something going wrong with the exhaust system. I'm trying to understand ...
12
votes
6answers
2k views

Why or why not increase engine efficiency by running the car “fuel-lean” (using a turbo or supercharger)?

Everyone wants their cars to use less fuel, right? I read the following passage about running the car fuel lean from this website: Run the engine fuel-lean, that is, use excess air. It is well ...
12
votes
9answers
11k views

Diesel vs Petrol motorcars. Pro's and cons?

I realize this may be a silly question to those of you on here who are proper petrol-heads and this may even be a repeat question, but I could not find anything on it on here, so here goes: What are ...
12
votes
4answers
6k views

Car crash: when does a car catch fire?

Which kind of crash does it need for a car to catch fire? I'm asking because I was discussing about an accident where a car crashed into a full-grown brown bear. Is it realistic under normal ...
12
votes
2answers
687 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 ...
12
votes
3answers
139 views

What is regenerative braking and why don't we use it?

I know that many electric cars use regenerative braking to enable the car to become more efficient by converting what would otherwise be lost heat energy in to a more useful, reusable form of energy. ...
12
votes
2answers
215 views

Why do Harley Davidson engines suffer from such poor performance?

The modern Harley Davidson engine has very poor power output. Even when highly modified a 130HP engine can cost tens of thousands of US Dollars. Here are specs on one of the modern engines. ...
12
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3answers
9k views

Why (almost) all dirt bikes have single cylinder engine?

Every dirt bike i know has a single cylinder engine. I myself ride a Yamaha XT660Z which has a huge 660 cc cylinder. What are the characteristics of those engines? what are the benefits of such ...
12
votes
4answers
45k views

What would be the most likely cause of engine sputter?

Most of the time my 2001 Honda Civic sounds like this... Vrooooooom. But some times when I start driving it sounds like this... Vrooom putt pa putt pa putt pa vrooooom. When it's in the "putt pa ...
12
votes
1answer
85 views

Dynamometer Question - How is it operated and what are they doing?

When guys are doing dyno runs they to do it in a gear, interact with the keyboard and then do it again in another gear. It seems they do multiple runs in multiple gears. In this post Paulster ...
11
votes
2answers
395 views

What is valve float and how does it impact engines?

The Wikipedia entry is hard to grok: Valve float is an adverse condition which can occur at high engine speeds when the poppet valves in an internal combustion engine valvetrain do not properly ...
11
votes
2answers
824 views

Why is a W-16 called, well, W?

The term "W-16" seems to imply some sort of configuration that resembles the letter W, which implies three banks of cylinders with one sharing a common cylinder head. In fact, the Bugatti W-16 in the ...
11
votes
4answers
22k views

Engine power specification at different rpm?

Car companies advertise power of an engine at different rpms. Car 1: 80 PS at 6000 rpm Car 2: 85 PS at 6500 rpm What does the power at different rpm mean? Does it mean Car 1 has better power than ...
11
votes
7answers
10k views

Engine oil change and getting rid of old oil completely

After running the vehicle for a certain distance usually we will change the engine oil. This will not only give engine new life with the brand new oil but will also get sludge and other sediments out ...
11
votes
4answers
135 views

2000 VW Polo struggles to/won't start when engine warm

My 2000 1.4 petrol polo struggles to start when warm and sometimes will not start, until the engine has cooled down a bit, when the engine is on the hot side of warm. Embarrassingly, I have lived ...
11
votes
5answers
2k views

How to properly change out spark plugs?

I am looking into how to change out my spark plugs on my 4 cylinder 2005 Mazda 3. All I know to do is: 1: Open each cylinder. 2: Use a spark plug socket (with the rubber insert) to remove the old ...
11
votes
2answers
298 views

Why did Ducati decide to use the desmodromic valve train rather than a more tradition valve train?

Ducati's use a unique method to open and close their valves. It's called the desmodromic valve train. The desmodromic valve system does not use springs to close the valve, it uses the cam and has a ...
11
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1answer
2k views

Why does diesel engine need a warm-up before the start-up?

When starting up, diesel engine needs approximately 5s before turning the key for ignition. Why is this neccessary and what can be damaged if you don't do that?
11
votes
3answers
8k views

How to begin learning engine tuning?

Quite simply, I want to begin tuning and modifying automotive engines for hobby. I have always been fascinated with cars, and I want to become knowledgeable in as many aspects of car tuning as ...
11
votes
1answer
341 views

2005 Subaru 2.5 RS - Engine-wise, how damaging is burning oil?

Assuming that an engine always has enough oil to be lubricated properly but burns quite a bit of oil, can it cause any damage in the long-term because it doesn't belong in the combustion chamber? I ...
10
votes
2answers
107 views

Motorcycle Four Body Carburetor Synchronization Balancing

I would like to adjust four-body carbs by myself, in order to avoid spent money every time. What are the basic rules, tools and secrets of synchronizing multiple carburetor bodies?
10
votes
2answers
13k views

WHY does an engine stall? (manual transmission)

Before you write off my question as one that's been answered a million times already, I want to clarify. I understand that the engine needs to go a certain rpm and when you try to engage the clutch ...
10
votes
2answers
2k views

How does ambient temperature affect engine efficiency and fuel consumption?

I remember from my physics class that the ideal-gas Carnot engine is more efficient if the temperature difference between the heat source and the thermostat ("heat recipient") is larger ...
10
votes
2answers
83 views

What is meant by degreeing a cam?

In the hot rodding world, "degreeing the cam" is an often used term when installing an aftermarket camshaft. What does the term mean, what does it do for you, why should you do it, and what are the ...
10
votes
1answer
45 views

What is the efficiency delta between rotary and modern four-stroke engines

Background There is a lot of opinion out there regarding the efficiency delta between wankel rotary engines and four stroke engines of various configurations (forced induction, etc). This delta, ...