Warming down na car?

[4age8u]

Do NA cars need to warm down,Is it wise to let them warm down.As you would a turbo car?

[geeang]

Generally no, that's why they're called 'turbo' timers.

[dasicvtec]

I'm not sure on the specifics but i just cruise slowly or idle it for about a minute or so after a hard run.

[JDM.Power]

any car that i drive i give it a abit off a break before i shut it down.
its just a habit i guess. doesnt hurt waiting like 2-3mins

[markoJEK1]

Your best warm down for an NA car is to do a lap or so round the block coasting, letting it sit without any airflow in garage for a couple of minutes will only increase its temperature.

[Mugen Civic]

no, but usually if the radiator fan is on at idle, i wait till it finishes its job.

[JohnL]

Once the engine is shut down it ceases producing heat and the engine metal starts cooling immediately (it won't get any hotter). Note that it's the temperature of the engine itself (i.e. the metal bits) that is important here, not the coolant temp, but it's coolant temp that controls the fan(s).

The fans may well come on a few minutes after the engine has been shut down (giving the impression that the engine must have become hotter) but this actually isn't because the engine is getting hotter, it's because the coolant is getting hotter as the engine metal gets cooler (i.e. metal losing heat into the water jacket).

Note that even though the engine has been shut down the coolant is still circulating through the cooling system (just more slowly because the pump has stopped pumping). This is due to the 'thermo-syphon' effect, whereby hot water rises (as it picks up heat from the engine) and cold water falls (as heat dissipates from the rad core), resulting in a relatively slow coolant flow (many vintage cars used no water pump at all, relying solely on the thermo-siphon effect).

The reason why turbo charged engines need 'turbo-timers' (or some light duty running after heavy duty running), is to do with the turbocharger itself, not the engine. This is because the turbo itself gets very hot and as a result so do it's bearings. In use the turbo shaft bearings are cooled by the lubricant flow, i.e. 'cool' oil continuosly passes through the bearings picking up bearing heat and carrying it away (to be dissipated into the oil in the sump).

Immediately after heavy use the turbo charger (as a whole) will be very very hot, and if we shut it down while it's still very hot the oil flow to the turbo bearings will cease and the oil still in the bearings will sit there reaching a much higher temp than is normal and begin to burn. In time this will cause the bearings and / or the ports into / out of the bearings to become choked with deposits from the burnt oil, which will reduce oil flow and ultimately lead to bearing failure.

Turbo-timers and 'slow down laps' (or the road driving equivalent) just give time for the turbocharger to cool before shut down, reaching a temperature at which the oil isn't as likely to be frying. Note that the high temperatures seen in the turbo-bearings is the main reason why turbo-charged engines require oils with a relatively high flash point (and more frequent oil changing doesn't hurt).

[bennjamin]

.....so the consensus is , within normal driving limits ( IE anything on the street) you do not have to let your car "cool down".

Other parts of the car might need to dissipate heat also (such as tyres or brakes) so depending on those you may require a "cool down" lap or drive. (semi slick compounds or higher rate rotors or pads)

[JohnL]

.....so the consensus is , within normal driving limits ( IE anything on the street) you do not have to let your car "cool down".

If we're talking engines, then it's my understanding that even when racing it isn't an issue, except for turbchargers.


Other parts of the car might need to dissipate heat also (such as tyres or brakes) so depending on those you may require a "cool down" lap or drive. (semi slick compounds or higher rate rotors or pads)

Brakes do present a potential problem. If a brake rotor is very hot after hard useage, and you suddenly stop it from rotating, then it is partially shielded from the (cool) air by the pads.

What now happens is that the rotor will cool at different rates in different sections of the rotor, with those parts exposed to air cooling faster than those parts shielded by the pads. This can / may result in rotor warpage, or in extreme cases in rotor cracking.

[OMG.JAI xD]

Lol sometimes letting an N/A car cool down is worse than not letting it cool down.

You have to pay attention to the cooling fans.
If these go on, it basically means your engine has reached its cooling limits with the coolant it self. Those fans go on just to radiate the heat and cool down the coolant.

If you drive in the driveway and your fans havent come on. Just turn it off.
Cause if you "Cool it down" and the fan turns on and you turn the car off, youre actually turning the car off at a hotter temp than it was when it came in.


I dont know if all turbo timers are like this but my mates one turns the cooling fans when the timer is activated.
Also turbo timers let bigger turbos spool down slowly.

Even most factory turbo cars dont have timers.

[Mr_will]

Lol sometimes letting an N/A car cool down is worse than not letting it cool down.

You have to pay attention to the cooling fans.
If these go on, it basically means your engine has reached its cooling limits with the coolant it self. Those fans go on just to radiate the heat and cool down the coolant.

If you drive in the driveway and your fans havent come on. Just turn it off.
Cause if you "Cool it down" and the fan turns on and you turn the car off, youre actually turning the car off at a hotter temp than it was when it came in.


I dont know if all turbo timers are like this but my mates one turns the cooling fans when the timer is activated.
Also turbo timers let bigger turbos spool down slowly.

Even factory turbo cars dont have timers.

I agree with most of the post but not that part.

Many modern turbo cars ensure that the oil pump remains on for a period of time after the engine shuts down.

for example, on the twincharged golf, not only will the oil pump remain on, but the cooling fans may come on of their own accord even when the engine is shut down.

[OMG.JAI xD]

I agree with most of the post but not that part.

Many modern turbo cars ensure that the oil pump remains on for a period of time after the engine shuts down.

for example, on the twincharged golf, not only will the oil pump remain on, but the cooling fans may come on of their own accord even when the engine is shut down.

Maybe i should fix that up ay?

Fixed.

Most factory cars.

[mars_panas]

useful info here... thanks guys...

[4age8u]

churr

[EK1.6LCIV]

I have seen turbo timers that can be installed for NA applications, I lol'd at first then seen a few cars locally with them fitted

beat the christ thro it, coast and park up, seem to work for us, only the s13 we cool off for several minutes as the dump pipe is molten orange after a good spirited drive

and new factory turbo cars don't need a turbo timer as they have sophisticated turbochargers compared to the decade old JDM cars of the past in which they can be turned off with no damaged, have several xr6 BFs around work and we just turn them on and off and haven't had a problem

[JohnL]

I have seen turbo timers that can be installed for NA applications, I lol'd at first then seen a few cars locally with them fitted

Designed to part the unwise and wankers from their cash...


and new factory turbo cars don't need a turbo timer as they have sophisticated turbochargers compared to the decade old JDM cars of the past in which they can be turned off with no damaged, have several xr6 BFs around work and we just turn them on and off and haven't had a problem

I'll bet these turbos are water cooled...

[EK1.6LCIV]

sorry to spam John, but I couldn't resist but to post a pic of the item autobarn is flogging off, only noticed it when we placed an order for a unit for the s13, lol

I vaguely remember the sales person quoting that cooling down an NA car had benefits for the waterpump, lol

quoted from Apexi, lol


In Japan, the Auto Timer is frequently used in normally-aspirated cars. Like turbo engines, normally aspirated engines can benefit from cool-down idling after a hard run. Many have also found it useful for keeping the A/C running on a hot day.


http://www.eautorace.com/images/goods/ApexiTurboTimerBlack.jpg

[aaronng]

Says "can" benefit and not "will" benefit. Heheheheh. :p

[flipfire]

I know its pretty useless to put a Turbo timer on an NA car.

but after extreme driving/racing, couldnt the burnt oil issue apply to engines too?

[jords]

I know its pretty useless to put a Turbo timer on an NA car.

but after extreme driving/racing, couldnt the burnt oil issue apply to engines too?

Generally after tracking a car you will do a warm down lap, if not 2, and your oil temps will plateau out to a reasonable oil temp.

Your discs, pads and brake fluid take a little more to cool down. i.e. don't put the hand brake on after a session/race as this may warp the discs.

[JohnL]

Says "can" benefit and not "will" benefit. Heheheheh. :p

That will be that more esoteric definition of 'can', i.e. 'can' as in 'doesn't'...

[JohnL]

I vaguely remember the sales person quoting that cooling down an NA car had benefits for the waterpump,

Now, I just don't believe that...


quoted from Apexi, lol
Quote:
In Japan, the Auto Timer is frequently used in normally-aspirated cars.

Why is it that "in Japan" or 'JDM' are so often used like mantras to imply that something must be unarguably the best way to do something or the best product? It's just not true...


quoted from Apexi, lol
Quote:
Like turbo engines, normally aspirated engines can benefit from cool-down idling after a hard run.

It certainly won't hurt, but its's far from being needed, or at least it's far from needed to have a gizmo to do it for you. I wouldn't recommend shutting off any engine seconds after a very hard run, but by the time you've parked the car it's 'idled' down enough.


quoted from Apexi, lol
Quote:
Many have also found it useful for keeping the A/C running on a hot day.

Or, you could perhaps leave the engine running as in; don't turn the key to 'off'...

[JohnL]

I know its pretty useless to put a Turbo timer on an NA car.

but after extreme driving/racing, couldnt the burnt oil issue apply to engines too?

The hottest parts will be the exhaust valve, the pistons and the rings.

The exhaust valve won't be damaged by burnt oil unless quite a lot of oil is being deposited on the valve (suggesting a sick engine...) which can cause thick deposits that can interfere with gas flow, but don't really hurt the valve itself.

The rings and ring lands are the area most likely to be affected by burnt oil deposits (clagging up the rings in the grooves and causing 'stuck' rings), but they are cooled quite quickly by their proximity to the relatively cool bore wall, and will be much hotter while the engine is running hard anyway (i.e. they will start to cool immediately the engine is shut down).

The deal with ('uncooled') turbocharger bearings is that they are cooler when the engine / turbo is running due to the cooling effect of the oil flow through the bearings, but when the oil flow stops, the bearings don't start to cool down, nor even stay at the same temp, they get hotter still because of heat soak from the very hot turbo casing. That's when the oil left in the bearings start to burn.

[jords]

Why is it that "in Japan" or 'JDM' are so often used like mantras to imply that something must be unarguably the best way to do something or the best product? It's just not true...





I couldn't agree with you more.

There are plenty of JDM fanboys on here that will disagree......

[JohnL]

I couldn't agree with you more.

There are plenty of JDM fanboys on here that will disagree......

I've heard people say things like "so JDM", when they don't actually mean 'Japanese Domestic Market', just that something is in some way impressive. I suspect some people who use it don't know it's significance, 'JDM' may be (?) becoming a trendoid 'word' devoid of any real meaning...

[Riced_Civic]

i hardly warm down my car and im boosted, i just drive out of boost for the last couple minutes b4 i shut down.

[clutch]

Do NA cars need to warm down,Is it wise to let them warm down.As you would a turbo car?

i think yes generaly its good on a hot day, as when the engine is stopped, the water is not flowing through the engine anymore, so the engine oil is not being cooled and is sitting in the engine getting hotter infact.

my dad (very knowledgable with cars) set up thermo fans to run on the radiator to atleast cool the water down in the radiator, therefore cooling the water slowley toward the engine.

thats only on hot days though, he dosent realy worry about it on normal/cold days

[dtrang]

Generally after tracking a car you will do a warm down lap, if not 2, and your oil temps will plateau out to a reasonable oil temp.

Your discs, pads and brake fluid take a little more to cool down. i.e. don't put the hand brake on after a session/race as this may warp the discs.

put in gear and hand brake down. putting the hand brake up will transfer the rotor heat and may boil your brake fluid also

[JohnL]

...when the engine is stopped, the water is not flowing through the engine anymore,

Yes it is, just more slowly without the water pump operating. Even with the WP not operating, the 'thermo-siphon' effect creates significant coolant circulation through the cooling system.

As the coolant in the radiator cools (expecially with the fans on) it becomes denser and 'sinks' to the bottom of the system while the less dense hotter coolant rises. This creates a circulation in the system with hotter coolant entering the top of the radiator and cooler coolant exiting at the bottom. As a result the engine is still losing heat through the radiator even after it's stopped running.

Many vintage cars have no WP at all and rely soley on the thermo-siphon effect to circulate coolant through the system. This is why many vintage cars (those without water pumps) must have such tall radiators, as this increases the thermo-siphon effect.



so the engine oil is not being cooled and is sitting in the engine getting hotter infact.

Once the engine is stopped the oil will pick up very little (if any) heat from the still hot engine because the oil drops to the bottom of the sump away from the hot metal. Once there the oil immediately starts to lose heat through the sump walls.


my dad (very knowledgable with cars) set up thermo fans to run on the radiator to atleast cool the water down in the radiator, therefore cooling the water slowley toward the engine.

Most cars these days run electric thermo fans. When the coolant in the radiator is cooled by the fans the thermo-siphon effect increases, so it's not just the coolant in the radiator that is cooled by the running fans when the engine is not running.

Notice that the fans often come on a short while after the engine has been shut down, then run for a short time before switching off. What happens is that at the moment the engine stops running the coolant isn't hot enough to trigger the thermo-switch, but as coolant flow slows (after shut down) it picks up a bit more heat from the metal of the head and (to a lesser degree) the block. Note that the metal that forms the combustion chamber walls always runs a bit hotter than the coolant.

The thermo-siphon effect then causes the coolant flowing through the block to cool relatively quickly until the thermo-switch turns the fans off. If the thermo-siphon effect didn't exist then the fans would run for a much longer time...

[twing]

my dad (very knowledgable with cars) set up thermo fans to run on the radiator to atleast cool the water down in the radiator, therefore cooling the water slowley toward the engine.

My civic already does that. During the summer, when I stop my car, the radiator fan automatically switch on itself. First time I thought it was faulty. Imagine the fan switched on, but you had the car key in your pocket :).