Questions tagged [power]

Practical questions related to engine power – or the loss there off. Questions about electrical power and powered accessories should use [tag:electrical].

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18
votes
6answers
99k views

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 ...
16
votes
6answers
3k views

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 ...
29
votes
7answers
16k views

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 ...
7
votes
2answers
314 views

How much can sub-optimal octane affect efficiency or power?

Suppose a production fuel-injected engine is tuned for 93 octane fuel. As I understand it, the engine can still run on lower-octane (i.e., less knock-resistant) fuel, but it will pull timing to avoid ...
11
votes
3answers
33k views

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 ...
11
votes
1answer
30k views

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 ...
7
votes
1answer
332 views

how do i know if my lead-acid battery has been resurrected?

The OEM battery in my 2008 Jetta SE 2.5L has been nearly fully discharged one month back (had insufficient surface charge after a prolonged use without the engine running, but leaving it idle for 20 ...
5
votes
3answers
429 views

Need to source PD-pump for small engine dyno school project

I am making a dyno to measure go-kart engine torque for a high-school project. I would like to use a water brake by varying input/output through a water pump and have read that this should be a ...
3
votes
3answers
180k views

Possible reasons for loss of power, engine shaking, and smell of liquid fuel (not burning)?

The car (Renault Megane 1998 1.6e hatchback) lost power (about 500rpm in a bursty rhythm) after I re-ignited on a traffic light, the engine started shaking, and I could smell liquid fuel. There was no ...
14
votes
4answers
15k views

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 ...
6
votes
7answers
46k views

How does cold, dry weather affect horsepower?

It's now properly winter over here in Australia, and the butt dyno is very favourable of the cold, dry air. It's like a free cold air intake for everyone, right?? I can think of two scientific ...
4
votes
1answer
961 views

Battery high voltage

I measured my "cigar socket / outlet" with a multimeter. Instead of 12v it had 19v. Is this normal? Is it my voltage regulator, alternator, battery that has problems? Car: Peugeot 307, 2.0 XSI 2003 ...
4
votes
2answers
3k views

would a sulfated discharged 12V battery charge at 12.5V?

I got a Stanley FATMAX RE-CHAGEiT 8AMP Automatic Battery Charger & Maintainer from Walmart for 29,97 USD, which appears to have three states of charging the battery -- detecting the voltage, rapid ...
1
vote
1answer
90 views

Designing IC engine [closed]

I am trying to design a theoretical internal combustion (IC) engine. The ultimate goal is to achieve 3000 hp with this engine, for which I know I will need low bore x stroke ratio, high compression, ...