whats worse for a cold engine?

[XR06T]

well, do people think that revs or load is worse for a cold engine. just interested as i have to pull onto a highway before my engine is at normal operating temp

cheers

[Steffo]

Both. I never move my car until the temp gauge jumps a bit off stone cold. And even then, its nice and slow until everything gets normal. 2-3 min of sitting there in the morning doesn't bother me.

[savagE]

According to the SMH it is actually bad to leave your car idleing when you are trying to warm it up because aparently it produces more carbon on your cyclinder heads.
When I warm it up, I just go about 1200-1300 RPM.

[madmelon]

Load: Bad because applying higher cylinder pressures to a cold engine will result in more blow-by and increases the possibility of gases creeping past the head gasket, causing it to fail. Older english cars are notorious for blowing head gaskets with even a slight thrash when they're cold. As the engine warms up, the pistons expand as does the block and head, which reduces the clearance around the piston and increases the clamping force on the head (dependant on materials- an all iron engine may actually lose clamping force due to the lower coefficient of expansion of irons compared to high tensile steels.)

RPM: Bad because the oil is not warm and so is still thick. Giving an engine high revs when it's cold will greatly increase the stress on the oil pump gears and drive, possibly causing premature failure. If the the oil can flow into the pump sufficiently at that temperature, the high oil pressure created may blow out seals etc (again thinking about clamping forces) but if it can't suck the oil it wants, it may cavitate, causing pump damage and possibly causing starvation at the bearings. Another thing is how long it takes to run back to the sump- if all the oil is up the top, then say goodbye to bottom end bearings.

The thicker oil generally puts more stress on all engine components as it takes more torque or force to move them. Also, oil consumption is not helped either as the thick oil is more likely to stick to the bores as the scraper ring comes past. This plus greater cold clearances is why you get blue (oil) smoke when you give it to a cold engine.

[madmelon]

One more thing- High RPM is also bad when cold due to higher clearances. Bigger clearances mean more freedom and so more chance of scuffing, flogging out holes/slots, etc.

[XA Coupsta]

the whole warming car up thing has been done on here plenty.....

[|||]

i just drive normally

by the time any damage is done some other sucker will own it lolz

[Steffo]

Originally Posted by savagE

According to the SMH it is actually bad to leave your car idleing when you are trying to warm it up because aparently it produces more carbon on your cyclinder heads.
When I warm it up, I just go about 1200-1300 RPM.

According to the SMH?

[vztrt]

Originally Posted by Steffo

According to the SMH?

Also according to the cars manual, that you shouldn't let your car idle to long. New cars are designed to be driven from cold, so if you dont thrash it nothing bad will happen.

[poolkeeper]

Originally Posted by XR06T

well, do people think that revs or load is worse for a cold engine. just interested as i have to pull onto a highway before my engine is at normal operating temp

cheers

I do the same thing, 1 min drive to motorway, then drive at 100 clicks for 30mins or so...

[AUXRVIII]

I knew a guy who has a VN SS and it would see 4000+ RPM daily within 30 sec's of start up and it still doesn't show any signs of something failing.
With todays thinner oils there would be less instance of oil pump stress, modern metal technologies and tighter engine tolerances also take care of the engine wear, potentially there would be no noticeable issues showing up if you like to flog a cold engine.
Don't take this as something I support, I'm on the fence here, technology changes quickly.

[XR6BF24V]

Older english cars are notorious for blowing head gaskets with even a slight thrash
Not suprised English cars are crap
The trick is to warm the engine as quick as possible
eg.no prolonged periods of idling and no caining it either just drive "normal" thats all u need to do and yes leave the thermostat in

[Bossxr8]

I used to work with this guy who claimed that fuel injected cars were great because, I quote, "you can just start them up and thrash them straight away, you don't even need to warm them up". But I guess he drove a VN Aero so that sort of makes sense. :

[RIPGMH]

All this "new engine" stuff is crap, metal is still metal and oil is still oil. Yes they are better designed and cope with a wider range of operating temperatures, but that doesn't exclude simple physics.

[atec77]

Originally Posted by XR06T

well, do people think that revs or load is worse for a cold engine. just interested as i have to pull onto a highway before my engine is at normal operating temp

cheers

Start it and if you MUST move do it gently , until the temp gauge is close to normal you don't mash the pedal , if you do it will byte you badly in short time

[351@GT]

And whats the go with forged pistons in this respect? i was told to warm it up fully.....

[burnz]

Originally Posted by 351@GT

And whats the go with forged pistons in this respect? i was told to warm it up fully.....

anything that is forged will die from thermal shock
simply short shift the gear's at quarter thottle until warm

[andrewts]

Well I don't go to too much trouble, I'm not going to let it sit and idle for a minute just to "warm up", but at the same time I'm not going to bounce off the limiter up the hill. I just take it easy.

[gz1]

The absolute worst thing you can do to a cold engine is ...
turn on the ignition.
Seriously leave off the ignition and then you get no wear at all.

[ebxr8240]

The nut is the worst thing on an engine..
Excessive rpm as clearances are still loose etc..
Some slight load won't hurt as it helps engine warm MUCH quicker...
I had a 3 series BMW and in its tech section it says to warm the engine
As quick as possible with light load...
But really if you have to ask??
I'm sure common sense prevails ???

[MITCHAY]

Can't say with this car, I've really ever let it idle to warm up. I just short shift with as little boost as possible.

It's a bit hard to get reasonable speed from my car with out a decent amount of RPM. No problems so far!

[5.4 GT]

Originally Posted by XR6BF24V

Not suprised English cars are crap

Yeh I reckon just look at these:









Anyway back on topic just drive the car normally, keeping the load light and revs low, for the first 15-20 mins (dont let it sit there idling for too long).

[savagE]

I would LOVE an E type or a DB9 (or is that a vantage?).

The Range Rover.... Aids thank you.

[Steffo]

Originally Posted by vztrt

Also according to the cars manual, that you shouldn't let your car idle to long. New cars are designed to be driven from cold, so if you dont thrash it nothing bad will happen.

To what car? My car's manual doesn't say that.

No car is designed to be driven from cold.

I'll quote a post I always do in threads like these, from the 'Warming GT,' thread in the FPV section of this forum from a while ago... snipping the bits that were irrelevant to the post (aimed at someone else in the paticular thread).

Originally Posted by Chris

**snip**

Down to business.

Oil viscosity, fluid dynamics.

Oil's are weighted to change their visocity with regard to temperature. People familliar with physics will understand thermal dynamics with fluids. Oil will adjust its viscosity in an exponential level, not a linear one.

You will notice a 600 hp race engine will be approx 20% inefficient in making its power until the oil reaches the correct temp to control clearances and windage. Once the oil temp hits the sweet spot, you will see a power increase.

Back on thermals, it does take a while for the oil to get to a point where the main tunnel clearances are consistent. When the oil is dead cold, the crank will wear "on bottom" of its clearance. Once the engine gets to temp (oil) it works its way more to the side. A main bearing will ALWAYS wear to the side of rotation, the warmer the oil gets, the further up the side of the bearing the main pin will travel. This goes for mains and big ends.

If you drive straight away, you are loading the mains and b/ends in the "cold" or centred and bottom part of the clearance. any wear will occur in this spot. The "running" wear area is further up the side of the bearing, as just stated.

I have noticed this on several of the competition engines we maintain, right down to the least powerful being an 18 degree chev making a mite over 700hp.

Street engines are just the same, its just that the clearances are usually smaller, depending upon make and model.

Driving the car with a crank running on the bottom will wear it prematurely because the load of the complete drivetrain is on the bearings.

Valve/seat coentricity

As people are aware, we have coolant flow through our cylinder heads. We have round valves, and round seats. There are specific thicknesses and widths and angles for the cutting of these seats. Some are designed around low lift flow and efficiency, mostly they are durable to promote coencentricity.

As the engine changes water temp from dead cold to operating temp (manufacturers spec) the valve seats start out round, as are the valves. But, the seats do distort and go slightly oval, whilst the valves stay round, pariculary the inlet valve.

Driving the car everyday will help the valves to seat and make their own "match". Leaning on an engine when cold could see valve seat failure, as a slight shape change with same seat pressure in the spring can soften the area around the seat, and the seat can fall out.

I have seen evidence of this with the Boss and the windsor, one an alloy head, one a cast item.

Lastly, letting a car idle and bore glazing with a steel billet cam is rubbish. The reason why we have been brought up to not let these cars idle is because past times, induction hardened cast camshafts need rpm to get oil between the lifters and camshaft (think about cam run-in - low seat pressure and rpms above 2000)

Billet steel roller camshafts have SFA wear. The wear you get with the older cast style is perfect for destroying rings, as the fine carbon particles (the ones that come out in oil first, and harder than the other components) are the cause of this. (which is why you change you oil immediatly after running in a cast iron camshaft. even though induction hardened, its still cast.)

Im happy to walk around my workshop and point out examples - I dont post on here because I have plenty of time on my hands - 12 years of street, strip and circuit endurance engine experience on hand to help anytime you guys need it.

For those of you who read too many magazines, hop into my world, where I do this every day, not as a hobby, as a profession.

**snip**

Also, here's a link to the post http://www.fordforums.com.au/showpos...3&postcount=33

And the thread itself... http://www.fordforums.com.au/showthr...ght=warming+GT

[AUIII XR8 MAN]

I been told by a number of a few mechanics is that the best way to warn you car up is to start the car up & let it idle for about 30sec then drive off normal. This is what i've been doing for years & never had a problem with any of my cars.

[madmelon]

Originally Posted by XR6BF24V

Not suprised English cars are crap

Myesss that's a genius comment. For two years I owned an 87 XJ40 Jag. Was originally a Caltex company car, had quite obviously been relentlessly thrashed its entire life. By the time I got rid of it (sold to wrecker, his daughter n wife now drive it) I had seen the oil pressure gauge hit 0 countles times at idle when it was hot yet it still pushed on...HARD. Might have been a bit slow initially, but it gave some VR/VS commodores a big surprise when it got to the midrange. Sounded a damn site better too. Not too bad for a car that had 230k km, was like...10 years older, weighed in some 300kg more and had an engine 200cc smaller. A reputation for bad reliability doesn't mean a car is weak or "crap"...just the same a reputation for good reliability doesn't mean a car is strong or at all "good". :

Something else worth considering- when combustion gases move past the piston and rings (when the car is cold or worn out) the oil deteriorates and loses its ability to effectively lubricate. Compounds may also develop which can attack some materials. This can be minimized by...minimizing cylinder pressures...ie load.

It's also worth noting that combustion gases moving past piston rings and ring grooves are bound to leave deposits (though tiny) and over time these may build up and cause a ring to jam, which would cause some serious problems.

It's fairly obvious both are a problem and combined they would serve to magnify each others negative effects... "more than the sum of its parts" or whatever. So be gentle...

[kempster1]

Originally Posted by madmelon

Load: Bad because applying higher cylinder pressures to a cold engine will result in more blow-by and increases the possibility of gases creeping past the head gasket, causing it to fail. Older english cars are notorious for blowing head gaskets with even a slight thrash when they're cold. As the engine warms up, the pistons expand as does the block and head, which reduces the clearance around the piston and increases the clamping force on the head (dependant on materials- an all iron engine may actually lose clamping force due to the lower coefficient of expansion of irons compared to high tensile steels.)

RPM: Bad because the oil is not warm and so is still thick. Giving an engine high revs when it's cold will greatly increase the stress on the oil pump gears and drive, possibly causing premature failure. If the the oil can flow into the pump sufficiently at that temperature, the high oil pressure created may blow out seals etc (again thinking about clamping forces) but if it can't suck the oil it wants, it may cavitate, causing pump damage and possibly causing starvation at the bearings. Another thing is how long it takes to run back to the sump- if all the oil is up the top, then say goodbye to bottom end bearings.

The thicker oil generally puts more stress on all engine components as it takes more torque or force to move them. Also, oil consumption is not helped either as the thick oil is more likely to stick to the bores as the scraper ring comes past. This plus greater cold clearances is why you get blue (oil) smoke when you give it to a cold engine.

This is like reading a fairly tale, I am guessing you do not have a mechanical trade

[madmelon]

Originally Posted by kempster1

This is like reading a fairly tale, I am guessing you do not have a mechanical trade

Uhh...not sure if that's supposed to be an insult or a compliment.
1 subject off being a mechanical engineer, with a huge bias towards automotive things. Just about aced the engine tech subject I took...

[kempster1]

All mechanical and electrical engineers should be made to do a trade prior to studying engineering.

[TEaaron]

I warm mine up for 5mins before driving off at around 1000-2000rpm

Simply because it won't idle when cold and will not move at low rpm's when cold.