[SLK]

Originally Posted by Technocrat

My conclusions are based on assumption that the switch off sensor is somewhere in cabin (i.e. its taking cabin temperature & not coil temperature). If the sensor is near coil then what you say holds true

Sensor is on the coil....
the sensor is there for another purpose... so that the coil doesn't get frosted/ frozen etc.

[SLK]

Originally Posted by esteem_lover

i feel that depends on the condition of your battery at that point of time.

Its a feature ... the cars are always supposed to cut off power to electronics.. to avoid spikes.
And.. the only reason the power would not cut off is...
1) either your cut off mechanism has gone faulty.. or
2) you turn the ignition key way too fast for the cut off to function properly.

[gd1418]

Originally Posted by Sideways

Heres some thing to think about - maximum engine damage takes place when cars are first started in the mornings or after a after a long time of inactivity where the oil from the engine settles down into the sump. Experts have estimated that starting an engine - cold start, dry start - whtever you want to call it ammounts to about 800 Kms of regular drving. so the folks who get into their cars and start the aircons before even starting their engines or to those who switch on their aircons immediately after startup - YOU SURE HAVE SOMETHING TO THINK ABOUT NOW. If you want your engine to last you will need to look after it. Switch it on, idle it, warm it up and then start driving. Just like we warm up or stretch before working out our engines need to do the same also.

Hi Sideways: this reminds of a fact of bygone era. My grandfather owned a Mercury Ford once upon a time and during winters the driver used to give the engine a couple of rotations the first thing in morning with the starting handle. Not many here may know about the starter handle. Around 10-15 yrs back the good old Amby used have one. When I asked the river as to why he did that, he replied - " Baba, tel baith jaata hai thand mein. Engine dheela kar raha hoon".

I never understood what he meant. But later understood the concept. So, an idle of 2 mins in the morning is advisable where the extremeties of the weather are there. And Ac should beswitched on after the car has run for about a km.

[viper]

Hi,

The safest would be is to wait till the temp starts registering on your instrument console.

Viper

[gd1418]

Good idea, but in places like Delhi, Gurgaon etc. where the temps are extreme, it takes quite a while to register on the console..

Originally Posted by viper

Hi,

The safest would be is to wait till the temp starts registering on your instrument console.

Viper

[adya33]

Originally Posted by Sideways

Heres some thing to think about - maximum engine damage takes place when cars are first started in the mornings or after a after a long time of inactivity where the oil from the engine settles down into the sump.
.................................
If you want your engine to last you will need to look after it. Switch it on, idle it, warm it up and then start driving. Just like we warm up or stretch before working out our engines need to do the same also.

In fuel injected cars the ECU revs the car at higher RPM than normal when engine is in cold condition.
Normally warm engine idles at 750 - 900 RPM; when engine is cold the idling is anywhere between 1250-1500RPM
AC adds about 300 RPMs.
And you are not supposed to rev hard your cold engine.
So lets say max RPM when engine is cold = 3000RPM (I follow 3000RPM)

Now when engine is warm
idling RPM = 750 - 900 RPM
idling with warm engine and AC switched ON
idling RPM = 1050 - 1200 RPM

which is still less than cold engine idling RPM.

So is one keeps the max RPM within 3000 RPM when engine is cold its fine, irrespective of whether AC is ON or OFF. Right ?

[viper]

Originally Posted by gd1418

Good idea, but in places like Delhi, Gurgaon etc. where the temps are extreme, it takes quite a while to register on the console..

Hi,

If you are referring to the winter then you would require the heater instead of AC right. If summer then it will still be the same. In any case after 1-2 kms of driving you wil get a temp registered on your dash.

Viper

[elf]

All this is getting quite confusing. Why don't you ladies simply start your engine, do not depress the throttle, let it idle for about 45 - 60 sec & then start driving?

That's what I do.

Hit your a/c switch after about 5-7 min of driving. If it's damn hot & you sweat, you sweat. It's upto you if you figure out whether your sweating is more important, or your engine life.

QED.

[esteem_lover]

Originally Posted by elf

All this is getting quite confusing. Why don't you ladies simply start your engine, do not depress the throttle, let it idle for about 45 - 60 sec & then start driving?

That's what I do.

Hit your a/c switch after about 5-7 min of driving. If it's damn hot & you sweat, you sweat. It's upto you if you figure out whether your sweating is more important, or your engine life.

QED.

"Ladies" ??? elf!! whats that mean ?

[elf]

Ladies:
noun: Humans of the opposite sex to men / non-men / female of human species.
colloquial usage: chicks / broads / gurlz.
noun: People who go for kitty party lunches & argue about air-conditioning.

[gd1418]

I knew I had goofed up. This was bound to come..

Originally Posted by viper

Hi,

If you are referring to the winter then you would require the heater instead of AC right. If summer then it will still be the same. In any case after 1-2 kms of driving you wil get a temp registered on your dash.

Viper

[narayan]

on highway drives, even if the weather is present, one ends up rolling up the windows bcos of the high speed wind getting in. has anyone got any data which suggests which is more fuel efficient

1) glasses rolled up with a/c on - resulting in less drag
2) glasses rolled down with a/c off - resuting in lesser load on engine

??

[vivekiny2k]

Originally Posted by adya33

So is one keeps the max RPM within 3000 RPM when engine is cold its fine, irrespective of whether AC is ON or OFF. Right ?

i think you are ignoring the load part. although the warm with AC RPM is lower than idling in cold engine, load may be much higher.

why to stress the engine if it is not warmed up yet....well also depends on how much stressed u get because of scorching heat.

[adya33]

Originally Posted by vivekiny2k

i think you are ignoring the load part. although the warm with AC RPM is lower than idling in cold engine, load may be much higher.

why to stress the engine if it is not warmed up yet....well also depends on how much stressed u get because of scorching heat.

How much load the AC puts on engine?
What if you are starting off your journey with 4 passengers and some luggage (w/o switching on AC), in such case you will be putting more load on engine.

[SLK]

Originally Posted by adya33

How much load the AC puts on engine?
What if you are starting off your journey with 4 passengers and some luggage (w/o switching on AC), in such case you will be putting more load on engine.

In my opinion AC puts more load than passengers.
I have no scientific backup for this.

Passengers maybe just a load when you first move the car... rest its all in momentum.... but the AC doesn't run on momentum... it needs continuous power.