Motor Vehicle Maintenance & Repair Stack Exchange
Motor Vehicle Maintenance & Repair Stack Exchange

Questions tagged [power]

Practical questions related to engine power – or the loss thereof. Questions about electrical power and electrically-powered accessories should use the [electrical] tag.

Practical questions related to engine power, or the loss thereof. Questions about electrical power and electrically-powered accessories should use the tag.

215 questions
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7 answers

When is a cold air intake system beneficial?

Cold air intake must be one of the popular mods there is, and one subject to the most controversy as well. Manufacturers of such systems advertise 5-20 HP gains, yet there are claims that this mod does nothing and may even hurt performance (even…
I have no idea what I'm doing
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What does the 'cc' mean on a motorcycle?

I'm relatively new to motorcycles, my flat mate taught me how to drive his two Royal Enfields around New Delhi, and for the past year and a half I've been taking care of them as they break down ;) Was just curious what the 'cc' actually means when…
Garrett Simpson
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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 than Car 2 because it's at lower rpm? Or does the rpm…
user3041058
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9 answers

Why do car starter motors draw so much current?

I understand that most car starter motors' power is rated between 0.5kw to 1.5kw. Doesn't that mean that they are supposed to draw 40-120 amps? (500 w / 12 volts etc.. )? Yet when they start, they draw hundreads of amps for the split second they…
Andrei Grigore
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6 answers

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 found two different answers. Will using a higher octane…
James Jenkins
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Does accelerating faster worsen fuel efficiency?

I've often heard that accelerating harder makes for bad fuel efficiency, but have yet to be given a sound explanation of why. Naturally this makes me question this advice. Now obviously when you accelerate harder, more fuel is being pumped into…
andrewb
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6 answers

What is the difference between torque and horsepower?

A very basic question - what is the difference between torque and horsepower? Its all over Google, but I am really confused and can't get any satisfactory answers. I'll tell you my confusion: Torque is an indication of acceleration, right? So, to…
Soumya Sen
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How does intake manifold runner length effect the power curve of a car?

Recently I learned that a number of things such as the cam profile, compression ratio and the intake manifold runner length and volume can all effect the power curve of the engine. Here is an example of one. What exactly is the intake manifold…
Max Goodridge
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How do these similar engines differ so much in power output?

I have a question that is bugging me for a long time. I will take a BMW E46 (3-Series) as an example so that it's easier to ask. Comparing M3 and E46 330 engines: S54B32 and M54B30, they are both petrol inline six engines where the M3 engine has a…
Max Urbanowicz
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7 answers

How many amps should my car pull while it is turned off?

I've recently started having a bit of trouble with my car. I typically drive my car to and from work each day. A couple weeks ago I went on vacation and when I returned, my car battery was as dead as could be. The battery was already a couple…
RLH
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4 answers

how fast does the alternator charge the battery?

It would appear that the common word of wisdom is that car alternators provide 50A of output. I actually looked at the supposed specs for my 2008 Jetta 2.5L on the internet -- a compact car -- and it would appear that it might be rated for 140A 14V…
cnst
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The battery is fine but my car will not start not even a clicking sound

When I turn the key in to start all the lights on the dashboard go out completely and when I turn it back to the off position the dash lights back up. What could the problem be if the battery is okay?
karl
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How does cylinder deactivation work?

I am still grinning from picking up a 2007 Chevy Silverado 1500 LT 4x4 with the extended cab. 146,000 miles on the clock and 5.3 liter V8 engine. It has displays for everything the engine is doing in normal operation, one of which is the mode it's…
cdunn
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Why does the power output peak and then drop as engine speed increases?

I have been looking at the power bands for my car (2000 Opel Agila 1.2) recently, as I want to work out when it is best to change gear and stuff, as I have no life! This is the approximate graph I made up in Excel comparing power and torque: Why…
George
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500 hp from a naturally-aspirated Honda K-24?

This video showcases a naturally-aspirated 2.7 L Honda K-series engine that revs up to 10,000 RPM and claims to produce 500 hp. I understand that this is for a motorcycle FWD drag racing application, but a specific power output of 185 hp/l seems…
Zaid
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