How long do you let your car warm up for on startup and why?
12-19-2002, 02:17 PM
#16
Addict
Rennlist Member
Rennlist Member
Join Date: May 2001
Location: A suburb of Silicon Valley, CA
Posts: 2,099
Likes: 0
Received 7 Likes
on
3 Posts
[quote]How long do you let your car warm up after startup <hr></blockquote>
I try to let my car warm up to operating temp (water temp gauge to normal postition). Usually takes 2-3 minutes. If this is not possible I definately drive gingerly and will not get into the "Boost" until the water temp is up.
[quote]And Why? <hr></blockquote>
Two reasons.
1. Aluminum engines expand at twice the rate as cast iron. To compensate, the Factory had to make the "cold" critical tolarances tighter (Cylinder bores/Pistons, etc.). As the engine expands the "tight" clearances open up to operating specifications. If the engine is overly stressed during this warm up period, excessive wear can occur. Cylinder walls can be scuffed. Excessive piston ring wear.
Conversly to tight clearances, until the engine is fully expanded, critical tensions are "Loose". Until the head and block have expanded the head bolt torque is not to spec. Boost a cold engine and risk blowing a head gasket. Until the block and head have expanded the cam and balance shaft belts are not to the correct tension (note, make sure that the engine is "dead cold" before tensioning the belts. you would be amazed how much change occurs in tension as the engine temp changes). Spin a timing belt and bend valves.
2. Oil is thicker when cold and is not as viscous. Given that the "cold" tolarances are already tight, thicker oil adds to the clearance issue and there is more friction. Bearings are at their greatest risk to spin during this period. Cam lobes can be flattened. Spool a turbo with cold oil to 150,000 rpm.....plan on many early rebuilds.
Given the high cost of parts for our wonderful 944's, if the above reasons don't make you give up 2 or 3 minutes..............you are on a collision course with father time.
And you won't win this battle.
[quote]orig posted by: porsche 5050:
I have heard many theorys <hr></blockquote>
The above principles are not theorys, just physics.
I try to let my car warm up to operating temp (water temp gauge to normal postition). Usually takes 2-3 minutes. If this is not possible I definately drive gingerly and will not get into the "Boost" until the water temp is up.
[quote]And Why? <hr></blockquote>
Two reasons.
1. Aluminum engines expand at twice the rate as cast iron. To compensate, the Factory had to make the "cold" critical tolarances tighter (Cylinder bores/Pistons, etc.). As the engine expands the "tight" clearances open up to operating specifications. If the engine is overly stressed during this warm up period, excessive wear can occur. Cylinder walls can be scuffed. Excessive piston ring wear.
Conversly to tight clearances, until the engine is fully expanded, critical tensions are "Loose". Until the head and block have expanded the head bolt torque is not to spec. Boost a cold engine and risk blowing a head gasket. Until the block and head have expanded the cam and balance shaft belts are not to the correct tension (note, make sure that the engine is "dead cold" before tensioning the belts. you would be amazed how much change occurs in tension as the engine temp changes). Spin a timing belt and bend valves.
2. Oil is thicker when cold and is not as viscous. Given that the "cold" tolarances are already tight, thicker oil adds to the clearance issue and there is more friction. Bearings are at their greatest risk to spin during this period. Cam lobes can be flattened. Spool a turbo with cold oil to 150,000 rpm.....plan on many early rebuilds.
Given the high cost of parts for our wonderful 944's, if the above reasons don't make you give up 2 or 3 minutes..............you are on a collision course with father time.
And you won't win this battle.
[quote]orig posted by: porsche 5050:
I have heard many theorys <hr></blockquote>
The above principles are not theorys, just physics.
12-19-2002, 07:40 PM
#17
Race Car
Join Date: Feb 2002
Location: Long Island, NY
Posts: 3,784
Likes: 0
Received 0 Likes
on
0 Posts
No matter how cold or hot warm, I let the car warm up to operating temperature. Why? Mainly the reasons that Bill and 944 S Boyeee stated. It just feels so much better at operating temp. PLus, it's better for the car.
12-19-2002, 08:21 PM
#18
Instructor
Join Date: Jul 2001
Location: Beautiful Grand Rapids, Ohio
Posts: 121
Likes: 0
Received 0 Likes
on
0 Posts
When mine is cold, I let it warm up until the gas milage gauge reads above 20 @1800rpm. This usually takes a few minutes. When it reads above 20 it feels pretty free and smooth, and runs nicer when I do take off. The aluminum <+> theory keeps me out of it until it warms up.
12-19-2002, 08:46 PM
#19
Advanced
Join Date: Jun 2002
Location: Brunswick, ME
Posts: 56
Likes: 0
Received 0 Likes
on
0 Posts
The owner's manual says to drive it right away. I start it and let it idle for about 20 seconds to get the oil flowing then I try to stay below 2000 rpm until warm. I live in a neighborhood where I can drive 25 for about a mile and a half which makes the warmup easy.
12-19-2002, 09:08 PM
#20
Race Car
Warming an engine at idle does nothing but give a false sense of security.
A)You might as well throw an hourmeter on it because your odometer is no longer an accurate way to gauge maintanence intervals.
B)Even if an idling engine suffered no wear and tear, this waste of time and natural resources has no benifit for the car's many other systems.
The wheel bearings, CV joints, differential, shocks/struts etc. are no warmer than they were before you started the car, but you have a fully warmed engine and are ready to have some fun with it <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" /> . The only time any vehicle (in good condition) ever needed to be warmed up was back in the days of carborators with manual chokes. I also find it pretty poor that in this point in history, anybody would find it socially acceptable to burn a few extra tanks of fuel over the course of a winter so that they can take their coat off when they get in the car. Maybe if our fuel prices weren't kept artificially low...Hey Sami and 944 Boyeee, what are you paying for 93 octane? 'round here the prices just jumped about $.07/liter over the last couple months, were up to $.41/liter ($1.58/gal), 89 octane is ~$.36/liter, up from $.31.
A)You might as well throw an hourmeter on it because your odometer is no longer an accurate way to gauge maintanence intervals.
B)Even if an idling engine suffered no wear and tear, this waste of time and natural resources has no benifit for the car's many other systems.
The wheel bearings, CV joints, differential, shocks/struts etc. are no warmer than they were before you started the car, but you have a fully warmed engine and are ready to have some fun with it <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" /> . The only time any vehicle (in good condition) ever needed to be warmed up was back in the days of carborators with manual chokes. I also find it pretty poor that in this point in history, anybody would find it socially acceptable to burn a few extra tanks of fuel over the course of a winter so that they can take their coat off when they get in the car. Maybe if our fuel prices weren't kept artificially low...Hey Sami and 944 Boyeee, what are you paying for 93 octane? 'round here the prices just jumped about $.07/liter over the last couple months, were up to $.41/liter ($1.58/gal), 89 octane is ~$.36/liter, up from $.31.
12-19-2002, 09:23 PM
#21
Racer
Join Date: Feb 2002
Location: n.c
Posts: 368
Likes: 0
Received 0 Likes
on
0 Posts
If we follow BMW's way of thinking,the M3 has lights around the tack to indicate when the engine is warm and ready for FULL throtle.Then again it also depends on the oil we use.BMW uses 0-40 Mobil 1.Some mechanic's that work on the air cooled 911's say never idle for more than 30 second's,but then again what about traffic jams.I say change the oil every 3333 miles and drive the **** out of it!It's a porsche!
12-19-2002, 09:49 PM
#22
Instructor
Join Date: Jul 2001
Location: Beautiful Grand Rapids, Ohio
Posts: 121
Likes: 0
Received 0 Likes
on
0 Posts
[quote]I also find it pretty poor that in this point in history, anybody would find it socially acceptable to burn a few extra tanks of fuel over the course of a winter so that they can take their coat off when they get in the car. <hr></blockquote>
Man I hope you didn't step in any of that. That boat of yours uses way more getting away from the dock than my 944 uses all year to warm up!
Man I hope you didn't step in any of that. That boat of yours uses way more getting away from the dock than my 944 uses all year to warm up!
12-19-2002, 10:02 PM
#23
Nordschleife Master
I usually idle for 30 secs and drive away, in the winter I double clutch the first few shifts.
In the winter when the car hasn't been driven in a week or more I'll let it idle for 2 or 3 mins and then drive away gently.
I keep it below 3000 and above 2000 (except for starting out in first of course) until the temp comes up, and below 3500 until the oil pressure comes down to 3bar at idle.
Of note...last time I drove the car (3 weeks ago, thanksgiving)...I drove around for 30 mins before the oil came up to temp...and even then the temp gauge was barely above the big block at the bottom. Oil pressure rules over temp gauge though
Even after a boost run or two... 
In the winter when the car hasn't been driven in a week or more I'll let it idle for 2 or 3 mins and then drive away gently.
I keep it below 3000 and above 2000 (except for starting out in first of course) until the temp comes up, and below 3500 until the oil pressure comes down to 3bar at idle.
Of note...last time I drove the car (3 weeks ago, thanksgiving)...I drove around for 30 mins before the oil came up to temp...and even then the temp gauge was barely above the big block at the bottom. Oil pressure rules over temp gauge though
Even after a boost run or two...
12-19-2002, 10:29 PM
#24
Race Car
[quote]Originally posted by Gerald Allgire:
<strong>
Man I hope you didn't step in any of that. That boat of yours uses way more getting away from the dock than my 944 uses all year to warm up!</strong><hr></blockquote>
Maybe I wasn't clear, or maybe my line of thinking is flawed (it is after all just my own opinion), but I don't recall having mentioned a problem with use in general, just waste. Keep your foot on the floor on the track for a few hours for all I care, Accelerate hard and brake hard, use whatever fuel you want but get some use out of it. My only complaint is when someone does something wasteful and then tries some lame excuse to justify it. I read the other day that some jackass came out of 7-11 to find thier car gone, maybe if they had taken their keys...It would be a shame if the insurance company paid for that one.
If it makes you feel any better, the boat has burned about 25-30 gallons in the last 3 years
<strong>
Man I hope you didn't step in any of that. That boat of yours uses way more getting away from the dock than my 944 uses all year to warm up!</strong><hr></blockquote>
Maybe I wasn't clear, or maybe my line of thinking is flawed (it is after all just my own opinion), but I don't recall having mentioned a problem with use in general, just waste. Keep your foot on the floor on the track for a few hours for all I care, Accelerate hard and brake hard, use whatever fuel you want but get some use out of it. My only complaint is when someone does something wasteful and then tries some lame excuse to justify it. I read the other day that some jackass came out of 7-11 to find thier car gone, maybe if they had taken their keys...It would be a shame if the insurance company paid for that one.
If it makes you feel any better, the boat has burned about 25-30 gallons in the last 3 years
