Please answer some car questions?

[bensonhedges]

I can drive (after a fashion) but don't know anything about what goes on under the bonnet (ok, I know where the screenwash goes), but I got to wondering:

 

What, in really simple terms, is brake horse power?

 

I know that my car is a two litre model, but two litres of what?

 

What is torque?

 

How, if the battery is just a box of acid, does it produce electricity?

 

Thanks.

[stackmonkey]

In simplified terms, and there will be plenty who can phrase it better than I can, but here goes

1) a battery doesn't produce electricity, it stores it using the charged particles that make up the acid as the means to do so.

 

2) 'two litres' is the nominal air/water capacity of the inside of the engine.

e.g.a 2 litre, 4 cylinder engine has four pistons of 0.5 litres each (500cc). that 500cc is the volume of gas that the piston moves through as it moves up and down within the engine.

 

3) brake horse power is the unit used to measure the maximum amount of energy created by the engine (it can be measured in Watts). all other factors being equal, the more power you have, the faster the car (top speed).

 

4) torque describes the force produced by the engine to turn the wheels.

again, all factors being equal, the more torque you have the quicker you will accelerate.

Torque is what actually gets measured and the horsepower is calculated from a standard formula.

 

extreme examples;

power - F1 car

torque - HGV truck

both - large engine'd sports and luxury cars

 

boring example...

a 2 litre petrol mondeo has about 140bhp and 140lbs.ft of torque and will do 132mph and 0-60 mph in 9.9 seconds

the 2 litre diesel has 128bhp, but has 244lbs.ft torque and will do 124mph and 0-60 mph in 9.9 secs.

On a race track, the petrol may be slightly quicker, but on the road the diesel will generally be quicker because of better acceleration through the gears at more normal speeds.

[Ginner]

Wouldn't want to stop people putting up answers (always interesting to read), but you might find How Stuff Works useful.

[artisan]

Brake horsepower is the power emmitted by the engine, not taking into account losses in the drive train. It is the ammount of power required to 'brake' (stall) the engine when running at full power.

 

Torque is the turning effect of that power, maximum torque is given out in a narrow band of the engine revs. It is kept within that range by the use of the gears. We tend to think of it more when pulling under load, starting off, going uphill etc.

 

The capacity of the engine is measued in litres, it is the swept volume of the cylinders per rev. That is, for 2 litres every rev takes in 2 litres of fuel/air mixture. The larger the capacity the more powerful the engine. But not necessarily more efficient.

 

The battery is a series of lead plates immerced in sulphuric acid. It is comprised of 6 cells each producing 2 volts, together these give out 12 volts.

I tis used for turning the starter motor, and for supplying small auxilliaries when the engine is off.

As soon as the engine fires, its function is taken over by the alternator and it has no further part in operating the engine (except as part of the charging circuit which is not really to do with the operation)

 

Hope that is of some use

[artisan]

The reason BTW that it is important to make sure your battery is good in winter, is that the alternator has little reserve power for charging in winter conditions.

We are using lights, heaters, demisters, wipers etc.

If the battery is not top notch, you will find it as flat a fart in the morning,a fter a long slow drive in foul weather the night before.

[fuzzy]

Can anyone tell me please.

 

I've just been out in my car to pick up my son, the car was juddering a bit but it does that sometimes. Stoppped to egt some food on the way back and parked almost near my house and turned it and the lights off. I decided i could park it a bit better and when i turn the key there is nothing.

 

The battery appears dead. It was only replaced last summer so it is not old and still under gaurenttee.

 

The question is Can i jump start it??

 

My son says its not good for the alarm and immobiliser.

[Guest]

You can jump start it. Have you had the alternator checked? Maybe the battery isn't charging properly?

 

Also immobilisers can do odd things sometimes causing your car not to start.

[fluffystuff]

Wouldn't want to stop people putting up answers (always interesting to read), but you might find How Stuff Works useful.

 

This is a great website:thumbsup:

[Skatiechik]

The question is Can i jump start it??

 

My son says its not good for the alarm and immobiliser.

 

If it is a new car you risk frying your ECU and other electrics. Up to you, but it can end up being quite expensive.

[SupraSteve]

If it is a new car you risk frying your ECU and other electrics. Up to you, but it can end up being quite expensive.

Care to explain that one to me - why will supplying standard battery voltage & current to a car, upset it? All you are doing is connecting up another car battery in parallel to help start the car as it's battery isn't up to teh job for wahtever reason. There is no increase in votage/current and there can't be any spikes caused.