Questions tagged [theory]

Use this tag when the question is **primarily** about the underlying ideas behind how something works. This tag should be used in conjunction with another tag for the area of interest, for example [electrical] or [suspension]. It should not be used "stand alone." Please use the [engine-theory] tag for those questions.

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1answer
35 views

Can inline plunger mechanical injection pumps pull through the fuel?

I know that they have lift pumps that bring the fuel towards the plungers so that the plungers can push and pressurize the fuel towards the injectors but i was wondering if lets say we removed the ...
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1answer
36 views

Bolt torque estimation based on angle and material

Is there a valid generic formula to roughly estimate a bolt's tightening torque similar to the "tighten by hand until seated, tighten XXX degrees more with your wrench"? I have used for many ...
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1answer
711 views

What are Wheel ticks and Wheel impulses?

I have some Odometry data taken from a Volkswagen Passat which gives the position. This is calculated using wheel ticks and in addition, I also have data which gives me the number of wheel impulses at ...
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6answers
17k views

Is it possible to have a manual transmission electric car?

Reading about the new supercar from VW, I distinctly noticed when the author specifically mentioned shifting to "drive". I know the car in article is an automatic, but it got me thinking. Is it ...
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1answer
23k views

What is surface charge and how does it affect battery testing?

I've read in numerous places that "surface charge" can give false positives when testing a battery, and you need to remove the said surface charge to get an accurate result. I've also read various ...
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1answer
204 views

Idling a cold engine before driving away: contradictory advice

With modern combustion engines it is common advice that idling before driving away for more than a few seconds (to build up oil pressure) does more harm than good, even in "arctic" winter conditions (...
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1answer
63 views

Does a diameter of a brake line affect braking pressure

I am currently building a brake system for a vehicle ground up and I know that the diameter of the master cylinder would affect the braking force proportionally to the area of the master cylinder. But ...
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2answers
210 views

Dual brake calipers with one brake line?

A comment at the end of this ChrisFix video (at about 14:42): https://youtu.be/gjqeFEyaUxc?t=882 raised my eyebrows a tiny bit. Chris says that you can run two brake calipers (two calipers on each of ...
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2answers
4k views

Why do the brakes "freeze" the suspension?

Last week I was driving a motorcycle. When I stopped at a traffic light I noticed the rear suspension dropped a little when I released the rear brake. Later I noticed my car did the same thing. When ...
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2answers
48 views

Questions about the clutch pilot bearing

I understand how the clutch system works in a manual transmission, but I'm struggling to get a proper image of what the pilot bearing does into my head. Does the input shaft always rest inside it, ...
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1answer
173 views

How can a DCT be so fast and smooth during hard acceleration and high rpm shifting?

I know how a DCT works and what parts it has, but I've always wondered how it manages to shift very fast and still be smooth, while having little torque drop during shifts.In a manual transmission, ...
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1answer
206 views

Can car alternator be used to save fuel by using it as a regenerative system at the same time?

Car alternators are 3 phase DC excited synchronous electric machines. They can be used as a motor by a proper 3 phase motor driver. Let's think that we connected a 200Ah Lithium based (eg. LiFePO4) ...
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1answer
96 views

Why doesn't polarity matter for fuel injectors?

Why doesn't polarity matter for fuel injectors? If they are essentially a solenoid, then it seems it would matter; swapping polarity would change the direction the electromagnet pulls or pushes.
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3answers
1k views

Why do electric motors produce peak torque instantly vs gasoline engines

On a separate forum, someone had asked why electric cars do not have transmissions. The simple answer was that electric cars produce peak torque at any RPM but the gasoline engine needs to rev up to ...
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2answers
267 views

Dry motorcycle clutch vs Wet motorcycle clutch discs material

I was wondering if the wet clutch discs on a motorcycle would be made out of the same friction material to the dry clutch discs. I understand this is probably not true, but does anyone know the exact ...
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1answer
165 views

How is automatic gliding realized with an automatic transmission?

It is generally accepted wisdom that it is a bad idea to coast or glide a car equipped with a conventional hydraulic automatic transmission. Coasting (running with an idling engine that is ...
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3answers
595 views

What are diamond cut alloy wheels?

I'm thinking of buying a new car, and one of the options it has is diamond cut alloy wheels. What's the difference between normal and diamond cut alloys?
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5answers
119k views

How to convert Amp Hours to CCA?

Is there a formula for converting a battery amp hour rating, which is used in much of Europe and Asia, to an Cold Cranking Amps (CCA) rating?
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0answers
181 views

Why ambient temperature used to measure pressure for car ac system

Since the ac system is located mostly inside a car engine and the car is warmed up prior to adding freon, and the temp/humidity in engine bay is different from ambient temperature//humidity, and all ...
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1answer
19k views

How do electric car transmission systems work?

How do electric car transmission systems work? Does it have an auto or manual gear concept like gasoline vehicles? As an electric motor can run in any speed (slow), is it necessary to have a clutch?
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1answer
4k views

Can a lightning strike cause your car to not run?

If lightning strikes a tree in your yard and your car is close by, can this cause your car to not work properly? I had an employee call in stating that lightning struck a tree beside their mobile ...
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4answers
249 views

What does the hybrid engine do with surplus energy?

This question is based on Toyota Hybrid flyers / experience but I suppose it's meant to be general for hybrids? The concept is to use electric motor for braking (therefore often the power of electric ...
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3answers
3k views

How does a timing light detect the electricity in the plug wire?

I assume that a timing light functions by some kind of inductive pickup and the signal is amplified by power from the battery and turned into a flash at the bulb. But I was wondering, is it picking ...
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0answers
127 views

Do all cars rust eventually even with repeated proper rustproofing methods?

My understanding is that rustproofing works and lasts when done properly, but once the coating used to rustproof wears off I'm guessing the process to rustproof needs to be done all over again. With ...
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4answers
128 views

Work over time; humans versus automobiles

I've been doing some research lately on torque and horsepower to understand how they are connected to one another. Take my car, a 2.0 TDI, outputs 390 Nm torque. 390 Nm alone without considering an ...
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1answer
87 views

How is fuel pressure maintained when the pump isn't running?

Pretty simple question, if liquids are incompressible then how is fuel pressure "stored" when the fuel pump isn't running, i.e. after turning to run and waiting a few seconds, but not turning to start?...
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1answer
352 views

Does a dual-clutch transmission require synchronizer cones?

When you shift in a traditional manual transmission, the clutch is disengaged and a sleeve is shifted from one gear to another. The teeth of the sleeve must align with the teeth of the target gear. ...
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1answer
736 views

Triangular/Parallel four-link suspension system, how it works

I've been really interested at car suspensions lately and this particular system confuses me the most... Are they simple hinges or do they also move other ways than that the angle they're placed ...
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0answers
147 views

Can a Battery Conductance Test tell the difference between damaged plates and sulfation?

I'm just going to lay out my assumptions, or what I think I know, so that there's a better context for the question. I understand that there are basically four main situations in which a standard ...
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3answers
514 views

How would a car handle differently if it had independent brake controls, like a pedal bike?

Facts - Cars have one brake pedal. Bikes have two brake levers. So a cyclist can brake fully with the front or the rear, or some combination of both, or alternate between the brakes. If a car had ...
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2answers
648 views

What is torque steer?

I saw an old Top Gear episode, and I think it was Jeremy who said something along the lines of The torque steer is terrible What is torque steer though? Is it a bad thing? Why does it happen? ...
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3answers
124 views

Multiple Batteries Charging

I have multiple batteries off from motorcycles, and each of them has it's own charge level (12-13 Volt measured at rest). Assuming I have only one 12 Volt charger, can I charge them in parallel until ...
3
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1answer
1k views

Why do hybrids have the aesthetic wheel cover on the body?

I've noticed that the manufacturers tend to cover the rear and/or front wheels on the hybrid models more often than the regular vehicles. Are there practical or functional reasons for the covers? Is ...
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6answers
6k views

Turbo equivalent on electric motors

Is there anything functionally equivalent to a turbo for electric motors? Obviously, I am not asking for something that reuses exhaust gases to force in more air, because there are no exhaust gases ...