Myths

fordel · 30-08-2007, 11:27 AM

I got this in a Ford email newsletter that I dont even remember subscribing too.

BUSTING THE CAR MYTHS

With car technology advancing in leaps and bounds since its humble beginnings, we thought it would be a good time to confirm or deny some of the many old mechanics tales that get passed around over the years.

MYTH 1: You can drive a long way on empty.

TRUTH: Each vehicle will vary, but you should be able to drive five-ten kilometers safely with an “empty” signal showing. It’s not a good idea to do this regularly as it starves your engine of fuel and increases the risk of vapour lock, particularly in the summer months.

MYTH 2: You should always warm up your car.

TRUTH: The days of leaving a car running for five minutes on a frosty morning are over thankfully, but it’s still a good idea to give your car some time to warm up. This allows the oil to circulate through the engine.

MYTH 3: It's best to shift an automatic transmission into neutral at red lights.

TRUTH: This myth stems from the idea that keeping the transmission in drive while stepping on the brake wastes fuel and causes unnecessary wear on the driveline. Actual engine wear and fuel loss are minimal.

melbzetec · 30-08-2007, 02:59 PM

Quote:

Originally Posted by fordel

This allows the oil to circulate through the engine.

This bit always amuses me, as I've read it in a few places. What?, the oil is not circulating for the first few minutes? Oil pump not working? Takes a good few minutes to get right around the engine does it? Oil just "sits there" 'til it can be bothered moving? LOL

zetec · 30-08-2007, 03:28 PM

The only real reason for a warm up period is not flogging the car when the oil is still warming up as it offers better protection when it's at operating temperature as we all know. The major area that suffers is gearbox, always good not to flog a car out of the parking lot straight away but just give it a few gearchanges to let everything warm up.

fordel · 30-08-2007, 03:40 PM

Quote:

Originally Posted by melbzetec

This bit always amuses me, as I've read it in a few places. What?, the oil is not circulating for the first few minutes? Oil pump not working? Takes a good few minutes to get right around the engine does it? Oil just "sits there" 'til it can be bothered moving? LOL

Yep it just sits there and yawns, doesnt want to move :P

I didnt write these, just copy and pasted from an email i got, so dont blame me

weenie · 30-08-2007, 03:47 PM

Have you ever started a 351 cleveland up & seen how long it takes idleing before the oil comes out the top of the rocker when cold starting????????

:

photn · 30-08-2007, 04:23 PM

Quote:

Originally Posted by weenie

Have you ever started a 351 cleveland up & seen how long it takes idleing before the oil comes out the top of the rocker when cold starting????????

:

if you read the post, we are talking about modern cars.

Quote:

With car technology advancing in leaps and bounds since its humble beginnings, we thought it would be a good time to confirm or deny some of the many old mechanics tales that get passed around over the years.

and most probably focusing on small cars. we dont care about v8's or 6's in here sorry.

We are not disputing that old cars may take longer to warm up, but simply, newer cars with technology dont needs as long.

:

melbzetec · 30-08-2007, 05:07 PM

Quote:

Originally Posted by zetec

The only real reason for a warm up period is not flogging the car when the oil is still warming up as it offers better protection when it's at operating temperature as we all know. The major area that suffers is gearbox, always good not to flog a car out of the parking lot straight away but just give it a few gearchanges to let everything warm up.

I read somewhere the other day, that the Zetec is designed to run with the oil at a minimum of 100 degrees C. Below that temperature creates greater wear.

ps Fordel...not having a go at you... just this "give time for the oil to circulate" amused me

And I do care about V8's!!

xbgs351 · 30-08-2007, 05:16 PM

Quote:

Originally Posted by photn

We are not disputing that old cars may take longer to warm up, but simply, newer cars with technology dont needs as long.

:

Do they warm up faster because they use newer laws of physics?

photn · 30-08-2007, 05:25 PM

Quote:

Originally Posted by xbgs351

Do they warm up faster because they use newer laws of physics?

No, they warm up quicker because of new technology. Also the size.

i doubt the New GT falcon Engines take as long to warm up as the old V8 engines in the XB falcon? or the XW/Y?

fordel · 30-08-2007, 05:48 PM

Quote:

Originally Posted by melbzetec

I read somewhere the other day, that the Zetec is designed to run with the oil at a minimum of 100 degrees C. Below that temperature creates greater wear.

ps Fordel...not having a go at you... just this "give time for the oil to circulate" amused me

And I do care about V8's!!

Yeah i know you aren't mate

I care about V8's too

and 6's for that matter ;)

Piotr · 31-08-2007, 12:11 AM

Quote:

Originally Posted by xbgs351

Do they warm up faster because they use newer laws of physics?

No, but we have aluminium blocks and better oil and coolant flow from better design

whippet_zetec · 31-08-2007, 09:57 AM

Quote:

Originally Posted by photn

and most probably focusing on small cars. we dont care about v8's or 6's in here sorry.

Am sure the email posted by Chris is a "general" email relating to ALL cars...and I suggest you speak for yourself about caring about V8's or 6's....you may not but like some others I sure do.

zetec · 31-08-2007, 10:42 AM

Before this turns into a slog fest, any car running a lower viscosity of oil, especially a fully synthetic will warm up quicker and more evenly and the better oil protects engine in this cooler stage. A Big V8 run on fully synth will be better protected, but then you have additional issues of the oil being too thin for the high pressure high rpm of a big engine and ;eaking out of the seals. The only reasons this has changed nowadays is due to better oils, nothing to do with the size of the engine! Each engine has a correct weight of oil that will protect it for life.

photn · 31-08-2007, 11:08 AM

Quote:

Originally Posted by whippet_zetec

Am sure the email posted by Chris is a "general" email relating to ALL cars...and I suggest you speak for yourself about caring about V8's or 6's....you may not but like some others I sure do.

sorry tod, was assuming that beeing in the small car segment we where only talking about 4cl cars, and didnt worry about the bigger V6's and V8's in here.

More revs · 31-08-2007, 12:03 PM

To avoid arguments I always avoid intangible words like 'better'....

Don't you agree it's a better position?

lol

photn · 31-08-2007, 12:06 PM

Quote:

Originally Posted by More revs

To avoid arguments I always avoid intangible words like 'better'....

Don't you agree it's a better position?

lol

LOL.... hehe

Ringo · 31-08-2007, 01:18 PM

Quote:

Originally Posted by xbgs351

Do they warm up faster because they use newer laws of physics?

I don't know that anyone actually understood your comment XBGS351...

Makes my top 10 posts of 2007....

Ringo · 31-08-2007, 01:21 PM

And has now become my signature.....

melbzetec · 31-08-2007, 04:48 PM

No...actually got it. Just ignored it.

xbgs351 · 14-09-2007, 07:42 PM

Quote:

Originally Posted by photn

No, they warm up quicker because of new technology. Also the size.

i doubt the New GT falcon Engines take as long to warm up as the old V8 engines in the XB falcon? or the XW/Y?

I wouldn't bet on it. The mod motors are on the porky side, they still have an iron block, and they still have a good volume of oil and water to heat up.

Now let us consider a Zetec vs a Kent. The Zetec is primarily made of aluminium and iron. The Kent is primarily made of iron. The Zetec weighs about 30% less than a Kent, mainly because of the use of aluminium in place of iron. Both motors have a similar volume of oil and coolant to heat. Now aluminium has a Specific Heat Capacity of 0.897 [J/gK)] compared to iron which has a Specific Heat Capacity of 0.450 [J/gK]. As Q = m c ΔT, where Q = heat, m = mass, c = Specific Heat Capacity and ΔT is the change in temperature, it is clear that aluminium takes twices as much heat to warm up a certain amount than iron does. With aluminium having a higher specific capacity than iron by 200%, there is no way that a reduction in engine weight of 30% is going to counteract it.

So why not face the facts? Newer technology does not make engines warm up faster, it just makes them less cantankerous to drive when they are not fully warmed up.

photn · 14-09-2007, 08:28 PM

Quote:

Originally Posted by xbgs351

I wouldn't bet on it. The mod motors are on the porky side, they still have an iron block, and they still have a good volume of oil and water to heat up.

Now let us consider a Zetec vs a Kent. The Zetec is primarily made of aluminium and iron. The Kent is primarily made of iron. The Zetec weighs about 30% less than a Kent, mainly because of the use of aluminium in place of iron. Both motors have a similar volume of oil and coolant to heat. Now aluminium has a Specific Heat Capacity of 0.897 [J/gK)] compared to iron which has a Specific Heat Capacity of 0.450 [J/gK]. As Q = m c ΔT, where Q = heat, m = mass, c = Specific Heat Capacity and ΔT is the change in temperature, it is clear that aluminium takes twices as much heat to warm up a certain amount than iron does. With aluminium having a higher specific capacity than iron by 200%, there is no way that a reduction in engine weight of 30% is going to counteract it.

So why not face the facts? Newer technology does not make engines warm up faster, it just makes them less cantankerous to drive when they are not fully warmed up.

How is it clear that alluminium takes longer to heat up??? i couldnt read your psycho bable..!!!!

Quote:

Originally Posted by Ringo

I don't know that anyone actually understood your comment XBGS351...

Makes my top 10 posts of 2007....

xbgs351 · 14-09-2007, 09:19 PM

Quote:

Originally Posted by photn

How is it clear that alluminium takes longer to heat up??? i couldnt read your psycho bable..!!!!

It's not psycho bable, it's plain and simple physics.

Here is the kindergarten version:

Starting with the basic formula
Q = m c ΔT

We want to calculate the change in temperature (ΔT), so we rearrange the formula to this:

ΔT = Q /m c

Heat = Q Lets assume that we add 1000 Joules of heat.
Mass = m Lets assume that the aluminium and iron weigh 100 grams.

Aluminium
Specific Heat Capacity = c = 0.897

ΔT = Q /m c = 1000/(100 x 0.897) = 11.15 degrees Celsius

Iron
Specific Heat Capacity = c = 0.450

ΔT = Q /m c = 1000/(100 x 0.457) = 21.89 degrees Celsius

Is that clear enough? Perhaps try wikipedia: http://en.wikipedia.org/wiki/Heat_ca...#Heat_capacity

photn · 14-09-2007, 09:45 PM

Quote:

Originally Posted by xbgs351

It's not psycho bable, it's plain and simple physics.

Here is the kindergarten version:

Starting with the basic formula
Q = m c ΔT

We want to calculate the change in temperature (ΔT), so we rearrange the formula to this:

ΔT = Q /m c

Heat = Q Lets assume that we add 1000 Joules of heat.
Mass = m Lets assume that the aluminium and iron weigh 100 grams.

Aluminium
Specific Heat Capacity = c = 0.897

ΔT = Q /m c = 1000/(100 x 0.897) = 11.15 degrees Celsius

Iron
Specific Heat Capacity = c = 0.450

ΔT = Q /m c = 1000/(100 x 0.457) = 21.89 degrees Celsius

Is that clear enough? Perhaps try wikipedia: http://en.wikipedia.org/wiki/Heat_ca...#Heat_capacity

Thank you!!!!

Much more clearer.. and im sorry that i didnt do Phsyics at school :P

xbgs351 · 14-09-2007, 09:49 PM

Quote:

Originally Posted by photn

Thank you!!!!

Much more clearer.. and im sorry that i didnt do Phsyics at school :P

Your welcome.

mudwaa · 15-09-2007, 07:56 AM

the only problem with the formula is the unequal mass.
cast iron is 7800kg per cubic metre
aluminium only 2700 per cubic metre

melbzetec · 15-09-2007, 01:27 PM

Woops!

xbgs351 · 17-09-2007, 09:41 PM

Quote:

Originally Posted by mudwaa

the only problem with the formula is the unequal mass.
cast iron is 7800kg per cubic metre
aluminium only 2700 per cubic metre

But you need more of it as it isn't as strong. Besides, I already covered the issue when I stated that a Zetec is around 30% lighter than a Kent.

mudwaa · 18-09-2007, 09:50 AM

yes i saw that but you didnt use that in the formula, nor did you take into account that the thermal conductivity of aluminium is .50 whilst that of iron is .163. In reality there are many things to consider. metal conductivity, area of material (engine block),
and barrier (wall thickness).Also consider that internal friction is the primary cause of heat and that you have coolant running between the inner and outer walls of the engine block acting to dissipate that heat.So really you have two formulas. One for conductivity arising from internal friction and the other for dissipation from the cooling system doing its job. On that note its completely bewildering to me and i think engine designers are absolute geniuses.

Piotr · 18-09-2007, 02:12 PM

Its pretty common knowledge that aluminium engine are faster to warm-up.