Questions tagged [engine-theory]
Use this tag when asking questions about the theory of engines. Do NOT use for practical problems, only theoretical questions
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Can you identify this part? [closed]
I have just had the cam belt and water pump changed at my local VW dealership on my 2004 VW Passat B5 and on the technical report they were kind enough to point out everything else they wanted to ...
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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 ...
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Why are the blades of car radiator fans unevenly spaced?
Fans that look like this:
Is it to somehow help the balance of the engine?
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How does Valve Overlap affect emissions?
In this question, it is suggested that valve overlap can affect emissions. In what way can valve overlap affect emissions?
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Why do Formula 1 cars use engines with many volumetrically small cylinders?
What's the benefit to Formula 1 using engines like a 3.0L V8 or a 2.4L V8?
I read this Reddit discussion on why it's not practical to put small many-cylindered engines into production cars. Cost ...
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Two-Stroke Diesel Engine - Do they use forced induction on them?
As I have indicated before, I'm very diesel ignorant. I just know the basics, very basics.
In a two-stroke diesel engine using forced induction seems necessary but at the same time I see challenges. ...
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Two-Stroke vs. Four-Stroke Diesel Engines - What is most commonly used in heavy vehicles?
I am not well versed in diesel engines. To prove my point, I've learned in the last month that a two-stroke diesel engine actually exists.
My Question.
What kind of diesel engine (four-stroke or ...
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What is Lobe Separation Angle (LSA)?
What is Lobe Separation Angle (LSA) and how is it used in camshaft design?
How is it measured?
What difference does a long or short LSA make?
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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 ...
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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 ...
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What is DEF and how is it used?
I keep hearing about DEF ... what is it and why is it used in conjunction with diesel engines? I know it is a more recent thing (last decade), but don't know much about it.
- 157k
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Why don't all diesel engines have throttle plates?
I learned recently that many older and some newer diesels don't have throttle plates to control airflow. I was also quite shocked to learn about a condition called diesel engine runaway. Apparently ...
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Scatter Camshafts - What are they and why do I want one?
It seems in the world on mini's as in Mini Cooper, there is a camshaft called a scatter cam. It changes the timing for cylinders 2 and 3. I've heard of changing the timing to have 1 and 4 firing at ...
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What's involved in getting a piston engine to spin the other way?
I've been thinking about this problem ever since I had to slightly crank my BMW's engine the opposite way to insert a crank-locking pin.
What are the fundamental changes required to make an engine ...
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Interference vs non-interference engines
What do people mean when they say that an engine has an interference design? How does it differ from a non-interference engine?
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What actually happens when the engine approaches redline and the rev-limiter is reached? [duplicate]
When the rev counter approaches the red zone, the power seems to stop and nothing seems to happen after this (even if your foot is flat to the floor)
What actually happens inside the engine when the ...
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Should I give a little throttle after my car starts?
When I start up my 2003 petrol car, as soon as it fires I often give it a dab of the throttle, so the battery recovers. It's fuel injected, no carburetor or anything.
I've been told this is pointless....
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Can 100% calculated load be reached in neutral?
While searching for information about how is engine load calculated I came across this question which contains an equation for the ECU load calculations.
As I understand it under fixed atmospheric ...
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Should I avoid full throttle when driving with a cold engine?
Apparently I should avoid full throttle until my engine temperature is warmed up fully (to 90 degrees on the gauge)
Normally I just get in and drive normally after about 10 seconds, and then after ...
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What is the Lovell Factor?
What is the Lovell Factor and how does it apply to engines and engine design?
EDIT: How is it calculated and what do the calculated numbers indicate? How is it useful in engine design? (I'm looking ...
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What is overboost?
I've heard the term overboost quite a lot.
What is "bad" overboost?
What is an overboost problem?
What will happen to my turbo engine if I don't fix it?
Edit: apparently there is a good type ...
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Fuel consumption at same speed of different engine
I am wondering why two car running at 100 km/h for example with a 100 hp consume less fuel that an engine of 300hp.
Even if I take a supercar lighter and more aerodynamics it will consume more.
But ...
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Diesel Engine Power
Let's say we have a 6 cylinder diesel engine having 385 KW power. Now I am running this engine at high idle of 1900 rpm. What will be power produced by this engine? Is it equal to max power or less ...
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Does revving a car when cold make it warm up faster?
As winter comes along, I've always thought that revving the car would make it warm up faster, so the heating works better to clear the icy/steamed up windows.
Does revving my car at idle to about 2-...
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What are swirl flaps?
I've heard a lot of talk about "swirl flaps" recently.
What do they do?
What are they for?
Are they only found on petrol or diesel cars, or both?
I've also heard they can be ingested by the ...
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How do the bore and stroke affect the characteristics of an engine?
How do the lengths of the bore and stroke affect the performance (power and torque), and general running characteristics (e.g. redline, noise etc) of a 4 cylinder engine?
Note: When asking this ...
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Why do engines run badly below the normal idle speed?
When the engine speed in my petrol car drops below about 650-700 RPM - the normal idle speed - it starts to shake and judder. This could be because say, I didn't give enough gas when pulling away.
...
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Does stalling damage my car?
I sometimes stall my car, as I have a new one and the biting point is so high.
Anyway, someone told me stalling damages my car, but all it does is force the engine to a complete stop...
Does constant ...
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What exactly is a "burnt valve" and what causes it?
I've come across this term a couple of times in the context of diagnosing engine-related issues, but don't know what it refers to. Here is an example from an automotive forum I frequent:
I gotta ...
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Why not have drive chains instead of drive (serpentine) belts?
My drive (serpentine) belt was recently chewed down to about half the width and I had to replace it.
Which brings the question: if the automotive industry has been gradually replacing timing belts ...
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Does Mazda's Skyactiv-G engine avoid EGR altogether?
It looks like Mazda sees high compression-ratio engines as the way forward to boost fuel economy and specific power on their midsize gasoline engine lineup (13:1 is an impressive achievement).
...
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Why does diesel engine have redline much lower than petrol engine redline?
Why do diesel automotive engines redline at around 4500 rpm whereas petrol ones go to 6500-8000 rpm?
Does this have something to do with the compression ratio?
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Why doesn't my rev limiter bounce?
I have a BMW 630i Steptronic from 2007.
If I floor the pedal in neutral the RPM is of course limited, but it doesn't "bounce" like regular rev limiters. Instead it keeps a constant and "clean" RPM.
...
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How is engine load determined?
I'm struggling to find information on how engine load is defined. Is it really just a fancy word for torque demand?
There are three parts to this question:
Is there a theoretical equation that is ...
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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 cylinder?...
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2.5L four-cylinder able to tow 2,700lbs?
My wife and I are looking at purchasing a new Subaru Outback. In the manufacturer's specifications, it states that for the 2.5L (four-cyl), that the towing package allows us to tow up to 2,700lbs.
In ...
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What happens to a car engine when giving max throttle while not in gear
I was driving (well standing still actually) during rush hour, and I was suddenly wondering what would happen to a car engine when I would push the accelerator pedal all the way down while the engine ...
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Does the size of engine cylinder affect the efficiency?
I mean that, if cylinder have a design in which piston can change its working area alternate. Is there any chance to affect the burning ratio in loss or profit to efficiency?
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Why are gears designed in this pattern in motorcycles? [duplicate]
On motorcycles with manual transmissions, the shifting gears goes (down to up) like this:
1st Gear (all down)
Neutral (half up)
2nd (full up)
3rd
(so on)
What is the logic behind this? Wouldn't it ...
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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 road racing in the 1990's to hear 4 Cylinder engines that ...
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Turbo gain level
I have a question - do you have any idea about potential
power level of 132 kW (180 HP), 700 Nm MAN truck (TGL)
4.5 litre engine with damaged (not working) turbo?
Would it accelerate to 55 km/h with ...
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What are the problems in building 2 stroke engines with a large displacement?
I understand (from preliminary research) that when engine gets bigger, with a higher displacement that it is practically not possible to have a two stroke engine.
What are the implications in ...
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Engine power specification at different rpm?
Car companies advertise the 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 ...
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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 ...
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Why do you need to change gears in car?
I'm trying to understand why cars have transmissions – why is it necessary to change from gear to gear as you're driving. I've heard the rule of thumb, "the higher your speed the higher your gear, the ...
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Does the a gasoline or diesel engine supply fuel at high speeds when not pressing the pedal and more
Let say I directly connect a small engine to my bicycle, and that I'm superman who can overcome any force.
Then I start cycling (using my legs...) - the engine starts to rotate, even though I haven't "...
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Brake Specific Fuel Consumption of 2-stroke vs 4-stroke
How much fuel do various types of engines burn per power output? I'm especially interested in naturally aspirated piston engines, and comparing two-stroke to four-stroke.
The wikipedia article gives ...
user3092
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What is the function of a blow-off valve vs a wastegate?
I am waiting for a 2013 STI and have been looking into upping the performance, but before I go down that road I would like to thoroughly understand the components in a forced induction vehicle.
I've ...
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Performance Exhaust -- what, how, why?
I've seen performance exhaust pipes on sale for cars and motorcycles, and my questions are these:
What does it do? (better performance [and how so?]? better mileage? cooler sounds?) Is/how is it ...
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Why does a Turbocharger only produce boost when the engine is under load?
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 valve mechanism that ...
