a note to all concerning engine warm up time

[cryptokid]

being the mechanicly inclined person that i am, i often wondered exactly how long it takes my engine to warm up to operating tempature. according to the oem water tempature guage, this is approximatly 3 minutes. i found this kind of odd that an engine can warm up this quickly.
when my engine is warmed up according to the oem guage, it runs at 191F.
i bought a aftermarket engine temp guage for an aircooled porsche and installed it by drilling a hole in the side of the cylinder head and using thermal epoxy to enclose the sending unit into the aluminum head. according to the cylinder head tempature guage, which measures the alumimum tempature, NOT the water, it takes approximatly 15 minutes of idleing to get to the fully operational tempature of 200F. i suspect this tempature is higher than my water temp of 191F because the radiator fluid is not 100% efficent at removing heat, so the physical engine tempature is awalys going to be hotter than the radiator fluid.

when driving around town the water temp remains pegged at 191F while the physical metal tempature fluxuates between 200F and 215F.

when under power at 85mph with the radio blasting and the a/c on max with my headlights on (to load the engine as much as possible) the water temp still stays pegged at 191F while the cylinder head temp climbed to 235F.

so, this has made me re-think the warm-up time it takes before you can punch an engine hard. most people drive their engine easy for the first 5 minutes before they drive hard, or redline and such. i would suggest waiting a bit longer, say 15-20 minutes of easy driving before you go out and run through the gears.

it takes amlost 5 minutes just to get the cylinder head over 100F, although the water temp is already at 191.

 

[nick778]

Interesting. And it certainly matches my experience. Ever run to a store and back for all of 5 minutes of driving and then do some work under the hood? The engine is warm but not hot but the water temp gauge was in the normal run area before shutdown. Your post got me thinking that indeed more warm-up/driving easy time (especially in the Winter) may be advisable.

 

[cryptokid]

yes, espically in the winter!
my research was done at south florida tempatures, 70-90F ambient.
id imagine in the dead of winder upnorth, it may take twice as long, as the engine has to warm up through perhaps double or triple the tempature offset that i have.

and of course, it probably varies a bit from engine design to engine design.

 

[TheTanSedan]

Warm-up all fluids, greases, not just coolant!

My rule of thumb is 15 miles, minimum, at 45+ mph before this period is reached. Then another 10 miles to burn off the water and associated crud.

Warm-up just means that one is now starting to rectify the cold start problems.

 

[Spector]

Further, what I believe we are really interested in is the oil temp as that is critical to burning off condesations etc. and it certainly is behind the coolant temp in terms of time, much longer to get the oil to operating temp.

 

[MolaKule]

On my Nissan Frontier, it takes approx. 90 seconds for the oil temp to get to 175 F.

 

[Schmoe]

Originally posted by cryptokid:
[QB] i bought a aftermarket engine temp guage for an aircooled porsche and installed it by drilling a hole in the side of the cylinder head and using thermal epoxy to enclose the sending unit into the aluminum head.


Dude, I'm worried about you.

Where did you get the idea to do that? I hope this wasn't an expensive engine. Would the epoxy have the same thermodynamic properties as that of aluminum??

 

[JohnBrowning]

The best way to warm up the car is to drive it gently. Prolonged idleing is not the best way to warm an engine up. I have seen some vechiles that took more then 1/2 hour of idleing to even come off the cold mark for coolant let alone warm the oil or reach thermodynamic effecincy. The bigest danger to driveing a cold engine hard is ring's and pistons. It is very easy to crack a ring. This idea is so well known in fact that BMW's new 3 series has a redline that adjusts to the engine tempature. The redline is like 3000 RPMs when cold and the digital redline slowly moves up to 9000+ RPM redline as temp comes up. IDealy your engine should be in a good enough state of tune that after 60 seconds of idleing it is ready to be driven. You should drive it easy until all the fluids are warmed up. I know some of you guys can not do this. I am able to do this on my way to work because I live ing a small city and have alot of city to cross to get to expressway. My workplace is 300 yards from the freeway so once I leave work I have drive more agressively then I would like on a cold engine.

 

[jason07-1zzfe]

quote:

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Originally posted by MolaKule:
On my Nissan Frontier, it takes approx. 90 seconds for the oil temp to get to 175 F.

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what ambient temp though? Either way I couldn't heat my oil that fast if I parked my car in an incinerator!

 

[cryptokid]

you cant heat oil that fast on a frying pan!

 

[cryptokid]

hi, the engine is fine, the place i drilled a hole is in a casting boss (i think thats what it is called) on the side of the head.

the epoxy is the kind used to thermaly bond heatsinks to computer components. so i think its pretty good stuff.

i no longer even look at the water tempature guage, this is basically useless to me now. i think the cylinder head temp is the only heat related guage one needs.

 

[nicrfe1370]

I forgot to add, what you found using the head temp. sensor was really interesting, and will probably alter the way I warm up my car. If I get on it too early in my WRX (which is turbocharged) I think it's possible that the quick heat shock could stress parts subject to wide variations in temperature.

 

[Tim]

quote:

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Originally posted by JohnBrowning:
The best way to warm up the car is to drive it gently.

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I like my way best...I installed a 1000w Zerostart coolant heater in my TDi when it was about a week old. Soon as I turn the key, the gauge reads 190 degrees. And you can't hold your hand on the valve cover (two hour plug-in at 30-40F).

I even plug it in when ambient is what most folks consider warm. 90 degrees is still 100 shy of operating temp!

Tim

 

[Michael SR]

the location of that temp sensor in the head might be on the opposite side of the water passages. that's besides the point, since i think oil temp is a better indicator anyhow.

an old racer's trick is also to put a 5psi switch on the outlet side of the coolant thermostat, before the radiator. regardless of the coolant temps inside the engine, the overall heat won't be enough to open the thermostat a lot for a while. by the time you see 5psi in the external cooling loop, the engine is ready to race.

i use oil temps, although i don't let cold temps stop me. i've been caught asleep (figuratively) and had to start an auto-x run with less than 100° F oil temps. what am i gonna do, refuse to take my run?

"hey, could we wait another five minutes? my oil isn't warm yet."

-michael

 

[Michael SR]

quote:

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"hey, could we wait another five minutes? my oil isn't warm yet."

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i just remembered something some of you might find humorous...

i used to work in a performance shop. we regularly hosted dyno days, saturdays where clubs would receive discounted runs, and we might strap down 25 cars in a few hours.

this college kid with a porsche 968 asked me, as i was strapping his car down, to please warm the oil before making the run(s). i asked how much temperature was acceptable, and he started on this long procedure... i stopped him short, and simply asked him to do it, and then hand the car over when it was ready.

he sat in the car, started it, and proceeded to just sit there and hold the (cold) engine at redline for about 90 seconds. just screaming. then he said, "ok."

gee, good thing he warmed it up before making a dyno pull...

for the record, i never made pulls unless there were obvious signs the engine was at least warm.

on a related note, some (unscrupulous) dyno operators use temps to bias results. whenever i was doing research, or tuning, i took great pains to insure all variables were held within the same range.

customers would comment all the time on how they saw X part gain Z hp at Y shop, why would that only gain D hp when i did it? why indeed...

-michael

 

[nicrfe1370]

cryptokid,
Interesting stuff, but I think there may be a problem. For coolant temp you were basing your readings on the oem gauge, which doesn't have numbers I assume, just a low range, normal range, and hot range. These gauges are deliberately, notoriously, and woefully inadequate. I read an article where a legitimate coolant temp. gauge with numbers and all (

) was installed and compared to the oem one. I forget the exact mechanics behind the oem gauge, but at a certain point when warming up it will read happily in the normal range, and won't budge a millimeter even though the legitimate gauge was showing temperature differences of 20 or 30 degrees. The oem gauge is there to just make you feel as though everything is hunky-dory, unless there is a major problem, at which point the needle will sweep into the red.
I did a similar check on my own car, comparing the oem gauge to a measurement taken from the OBDII port. The oem needle reads the same temp when the computer readout through the port read from about 150 to 200. Ouch.

 

[Parker Dean]

Actually, for emissions control reasons the manufacturers AIM for coolant to be at operating temp in under three minutes. There's a spec for this somewhere...

Anyway, I'm with TheTanSedan in that best protection occurs when all fluids are at operating temp. Consider the difference in a multigrade oil at close to room temp and operating temp. They don't run high-power piston engines in aircraft hard until the oil is up to temp for a reason.

Now if you gotta race, you gotta race, but it would be better for the cars durability if you had the oil ready first.

 

[Patman]

quote:

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Originally posted by Parker Dean:
Actually, for emissions control reasons the manufacturers AIM for coolant to be at operating temp in under three minutes. There's a spec for this somewhere...

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I wish that were true in my Firebird. Even on a hot summer day it takes at least double that time before my coolant hits 190F.

 

[Greaser]

On my straight six Jeep engine's...fire em' up..idle for a minute or so..then I'm off...they are at 100 degrees C by the time I'm two blocks from home...with gobs of heat in the winter

 

[RussellA]

quote:

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Actually, for emissions control reasons the manufacturers AIM for coolant to be at operating temp in under three minutes. There's a spec for this somewhere...

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I can believe it. I ran my cold v6 Toyota for 90 seconds maybe less to check an O2 sensor. Then accidently touched the exhaust manifold with the back of my hand and the skin quick fried and curled up like a piece of bacon. A nasty second degree burn. Have an ugly mark 4 months later and expect it will still be there in 4 years . If you told me that exhaust manifold was 500 degrees, I would believe it. I have never seen an engine get so hot so quick. These are not like old cast iron v8s.