For questions about words, phrases and definitions that are specific to maintenance and repair of motor vehicles.
Questions tagged [terminology]
29 questions
21
votes
3 answers
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 follow the closure phase of the cam lobe profile. This…
Zaid
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19
votes
3 answers
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 say it's not likely to be a burnt valve. These…
Zaid
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15
votes
1 answer
How come full throttle is meaning full speed instead of the opposite?
I am stumbling about full throttle. To throttle usually means to brake down or slowing down. Technically it is a flap which is reducing the air delivery which is important for the combustion process.
So my natural understanding of full throttle…
Thomas
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15
votes
1 answer
What exactly are fuel trims?
What is meant by the term "fuel trim"?
Why are they so important in diagnosing engine operation issues?
How do short-term fuel trims differ from long-term fuel trims?
Zaid
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14
votes
2 answers
Is there a difference between a sunroof and a moonroof?
The sunroof tag here states:
The opening in the roof of a car. Usually a glass panel that opens by sliding down and back.
However, the owner's manual of my 2006 Mazda 6 refers to the opening only as a moonroof, and never mentions a sunroof. I've…
Tas
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13
votes
4 answers
What are the "1" and "2" or "L" gears used for on an automatic?
In a car with an automatic transmission, we are normally greeted by the acronym PRNDL, or in some cases (older cars) PRND21.
I know that the L, 1, or 2 will cause the transmission to stay in a (L)ow gear and not upshift, but I've heard various…
JPhi1618
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12
votes
4 answers
What is the large metal bar that sits behind the bumper?
I've seen a few vehicles with their plastic bumpers off recently. They all seem to have a large metal crossbar sitting in front of the radiator. What is this called?
Update:
And a sideview of the metal crossbar to impact absorber to chassis rail on…
timbo
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12
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3 answers
What's the meaning of a "lean" vs "rich" air fuel mixture
I'm learning about vacuum leaks on engine intakes and I'm hearing this terminology of lean air fuel mixture. I thought I heard of a rich mixture before too. What's a normal mixture referred to as? A balanced mixture?
Also just for clarity, this…
jxramos
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11
votes
3 answers
What exactly is a jackshaft?
The Wikipedia entry for the Ford Cologne 4.0L SOHC describes the use of a "jackshaft":
It uses a jackshaft in place of a camshaft to drive a timing chain to each cylinder head. Three timing chains are used, one from the crank to the jackshaft, one…
Zaid
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9
votes
2 answers
Crank vs turn over vs start vs whatever
I see conversations like the following a lot:
A: My car won't start.
B: Does it crank?
A: Yes but it won't turn over.
B: Wait, I'm confused. So, it tries?
A: Well it makes a sound.
B: Like whir whir whir or just the clicks?
A: Yes.
…
Jason C
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8
votes
1 answer
Which side of the engine is the "front"?
Maybe this is a silly question, but what is the technical definition of the "front" vs. the "rear" of the engine?
On my vehicle, from the context of part names, the "front" is the side with the timing belt and the other belts, the alternator,…
Jason C
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6
votes
2 answers
Term to indicate how much force one needs to exert to steer the wheels of a car
What is the proper term to indicate how much force the driver needs to exert to steer the wheels of a car?
Franck Dernoncourt
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6
votes
2 answers
What does NM@rpm mean in car's spec sheet?
I checked my car's specs sheet this morning and in it I noticed:
Torque NM@rpm: 145@4600
What does NM@rpm mean?
Jomar Sevillejo
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5
votes
5 answers
What do you call the distance driven on a vehicle?
In the US (and I suppose other places where distances are still measured in miles) the term is mileage. But what about the rest of the world? Is there an SI term for mileage? Or is mileage still the term used in English speaking countries – but…
dlu
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4
votes
2 answers
Renewed brake pads
I am new to the automotive world and especially in services. I did some research on some things, but others I cannot find definite answer.
I bought a car which has had "renewed brake pads and discs" but I do not really
understand the word…
David Kasabji
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