Car cooldown question
Discussion
Hi guys,
I had a question around car cool down after a session on the track...
I've only been on one track day previously and after I came off the track I had a little slow drive around the grounds to give the engine a bit of an extra chance to cool down (after a slower lap) - but then turned off the engine when parked up to enable me to leave it in first rather than applying the hand brake.
I'm sure leaving the engine running would be better for 10 minutes but then you obviously can't leave it in first.
What do you tend to do? The only option I can see would be to take some blocks but I'm rather untrusting of them!
Thanks in advance
Sean
I had a question around car cool down after a session on the track...
I've only been on one track day previously and after I came off the track I had a little slow drive around the grounds to give the engine a bit of an extra chance to cool down (after a slower lap) - but then turned off the engine when parked up to enable me to leave it in first rather than applying the hand brake.
I'm sure leaving the engine running would be better for 10 minutes but then you obviously can't leave it in first.
What do you tend to do? The only option I can see would be to take some blocks but I'm rather untrusting of them!
Thanks in advance
Sean
Imo the best way to cool the car is a steady lap before returning to the paddock. Fresh air flowing through the radiator at 60-70mph will be far more efficient than sitting letting the car idle with the fan spinning. Cool it down for a steady lap, no harsh accelerating or braking, come back into the paddock, park it up, turn off, 1st gear no handbrake.
Cars are a slightly different kettle of fish, I grant you - more metal to worry about I guess!
But our racing bikes had this: total max for however many laps of the race, cross the line...then one slow-down lap, followed by a gentle saunter back to the paddock. As it happens, they would cool down quite quickly on the slow-down lap (had race radiators and no thermostat) but warm up again quite significantly riding slowly through the paddock (no radiator fan and an idle speed of 2,000 rpm to help with eliminating rear wheel lockup into turns) so I'd want to get it parked and switched off pretty sharpish.
WRT cars I've done trackdays with - as said, heat soak is the main worry, and it also probably depends on whether you have a turbo or not?
For non-turbo cars, i've done just a warm-down lap at high gears / low revs and throttle, then a bimble back to the paddock, stop, allow to idle for maybe 60 seconds, and switch off...but then put into gear to park, and not use the handbrake.
For turbo cars...the same thing, but once stopped, I sit in the car and let the engine idle for a good 3 or 4 minutes. Then shut down, put into first gear, get out and lift the bonnet to allow heat to dissipate.
No idea if these are the right approaches - but it's what I have done!
But our racing bikes had this: total max for however many laps of the race, cross the line...then one slow-down lap, followed by a gentle saunter back to the paddock. As it happens, they would cool down quite quickly on the slow-down lap (had race radiators and no thermostat) but warm up again quite significantly riding slowly through the paddock (no radiator fan and an idle speed of 2,000 rpm to help with eliminating rear wheel lockup into turns) so I'd want to get it parked and switched off pretty sharpish.
WRT cars I've done trackdays with - as said, heat soak is the main worry, and it also probably depends on whether you have a turbo or not?
For non-turbo cars, i've done just a warm-down lap at high gears / low revs and throttle, then a bimble back to the paddock, stop, allow to idle for maybe 60 seconds, and switch off...but then put into gear to park, and not use the handbrake.
For turbo cars...the same thing, but once stopped, I sit in the car and let the engine idle for a good 3 or 4 minutes. Then shut down, put into first gear, get out and lift the bonnet to allow heat to dissipate.
No idea if these are the right approaches - but it's what I have done!
Ray Luxury-Yacht said:
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For turbo cars...the same thing, but once stopped, I sit in the car and let the engine idle for a good 3 or 4 minutes. Then shut down, put into first gear, get out and lift the bonnet to allow heat to dissipate.
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Turbo-timers are rightly popular for situations like this. I would also leave the air-con on to help cool things under the bonnet of my GTO while the engine was running.For turbo cars...the same thing, but once stopped, I sit in the car and let the engine idle for a good 3 or 4 minutes. Then shut down, put into first gear, get out and lift the bonnet to allow heat to dissipate.
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Many thanks for the feedback guys, sounds like I'm probably over thinking it!
Car is a E92 BMW 330i (I know, nice & heavy!) - so its N/A, no turbo.
I'll just do a nice cool down lap, little drive around the ground and park it up in 1st and possibly open the bonnet up!
Thanks for all the comments
Sean
Car is a E92 BMW 330i (I know, nice & heavy!) - so its N/A, no turbo.
I'll just do a nice cool down lap, little drive around the ground and park it up in 1st and possibly open the bonnet up!
Thanks for all the comments
Sean
Have you noticed the engine temp gauge go up much on track? Unless you have, I would say the cool down lap is of more benefit to the brakes than the engine.
That said, I always pop the bonnet when parked up as it's bound to let far more heat escape the engine bay, and I can't see any downside to doing so.
That said, I always pop the bonnet when parked up as it's bound to let far more heat escape the engine bay, and I can't see any downside to doing so.
You're maybe missing the point a bit braddo, it's all about heat from the engine vs cooling from the radiator.
He could have no temperature issues on track when pushing the engine hard but cooling is optimal then in the paddock the residual heat is still there but with minimal cooling...
Sean,
If you're worried at all about the temperature I'd recommend just extending your cooldown laps rather than trundling about the paddock. Just ease off halfway into your penultimate lap. Maybe think about the time needed to cool down relative to the specific circuit lap length.
Opening the bonnet can't hurt but nothing like the same benefit.
He could have no temperature issues on track when pushing the engine hard but cooling is optimal then in the paddock the residual heat is still there but with minimal cooling...
Sean,
If you're worried at all about the temperature I'd recommend just extending your cooldown laps rather than trundling about the paddock.
Just ease off halfway into your penultimate lap. Maybe think about the time needed to cool down relative to the specific circuit lap length.Opening the bonnet can't hurt but nothing like the same benefit.
Fair enough. Don't get me wrong, I'd never not do a cool down lap and my experience is VERY unscientific - just putting my hand in various areas around the engine bay feeling for unusual radiated heat.
I guess it's precisely because of the cool down laps that the engine bay has never seemed very hot on my cars at track days. Whereas when I took a similar size/weight car as the OP's on a track day (my C43), I think that in hindsight I should have extended the cool down periods for the brakes, which got quite grumbly on the day.
I'll still always pop the bonnet afterwards just in case, but that's probably more about paranoia of wiring melting than the actual engine itself overheating. Let's call it a hangover from doing track days in a 40 year old Italian car.
Don't get me wrong, I'd never not do a cool down lap and my experience is VERY unscientific - just putting my hand in various areas around the engine bay feeling for unusual radiated heat. I guess it's precisely because of the cool down laps that the engine bay has never seemed very hot on my cars at track days. Whereas when I took a similar size/weight car as the OP's on a track day (my C43), I think that in hindsight I should have extended the cool down periods for the brakes, which got quite grumbly on the day.
I'll still always pop the bonnet afterwards just in case, but that's probably more about paranoia of wiring melting than the actual engine itself overheating. Let's call it a hangover from doing track days in a 40 year old Italian car.
you're joking, right? i do two cool down laps! a bit ocd i know.
firstly i back off max revs and cruise round, but still corner quite fast and use some power to keep out of the way, what you might call a stealth cool down, followed by a full-on cool lap.
into the pits and engine off. That method really gives protection and i still enjoy a few corners of the penultimate lap.
firstly i back off max revs and cruise round, but still corner quite fast and use some power to keep out of the way, what you might call a stealth cool down, followed by a full-on cool lap.
into the pits and engine off. That method really gives protection and i still enjoy a few corners of the penultimate lap.
Many thanks again for the comments.
Running A/C is stupid, it'll obvioiusly generate more heat under the hood - I assume you mean to run the fans with hot air which would help a little... my car has a "rest" button so it can keep kicking out heat after the engine is off which could be useful... I use that sometimes after a spirited drive home!
Running A/C is stupid, it'll obvioiusly generate more heat under the hood - I assume you mean to run the fans with hot air which would help a little... my car has a "rest" button so it can keep kicking out heat after the engine is off which could be useful... I use that sometimes after a spirited drive home!
I certainly don't see any advantage in keeping it running. For turbo cars, you have a very specific case, namely the turbo which is *stupid* hot; if you just switch off, the oil is no longer circulating, so the stuff within the turbo gets cooked, and breaks down. You run the engine to keep the oil flowing until the turbo has cooled, that's all.
For a normally aspirated car, I really can't think of a bad hotspot scenario. If the heat is under control while driving (the cooling system is capable of dissipating what you put in), then there's no particular cooldown requirement. The thermostat opens and closes to take the rad in and out of the equation on the road, to keep the temp up (and down). On the track, you can assume the thermostat is open more/all of the time, but unless the car runs hotter, the system is still coping, and the engine temp is 'within design'. Of course the oil temp and water temp are different - the oil temp may be doing more interesting things.
However, once you switch the engine off, no more energy is being put into the system, so the temperature can only fall. Running the engine is putting energy in, and there's no real cooling flow, so the temperature will only rise. Unless there's a specific hot area that demands you keep oil/water flow (like a turbo), the fastest way to cool it is to switch it off!
As someone else said, the biggest cooling issues on most cars is likely to be the brakes.
For a normally aspirated car, I really can't think of a bad hotspot scenario. If the heat is under control while driving (the cooling system is capable of dissipating what you put in), then there's no particular cooldown requirement. The thermostat opens and closes to take the rad in and out of the equation on the road, to keep the temp up (and down). On the track, you can assume the thermostat is open more/all of the time, but unless the car runs hotter, the system is still coping, and the engine temp is 'within design'. Of course the oil temp and water temp are different - the oil temp may be doing more interesting things.
However, once you switch the engine off, no more energy is being put into the system, so the temperature can only fall. Running the engine is putting energy in, and there's no real cooling flow, so the temperature will only rise. Unless there's a specific hot area that demands you keep oil/water flow (like a turbo), the fastest way to cool it is to switch it off!
As someone else said, the biggest cooling issues on most cars is likely to be the brakes.
I track a 944 turbo and the coolant temperature never gets above the 2/3rds mark but I do have an oil temperature sensor in the sump plug and can see 120-125 degrees c after a session.
I do a cool down lap and then park up on a flat surface, engine running and bonnet open until the oil comes down under 100c, by then I figure that the turbo has cooled down sufficiently too.
I do a cool down lap and then park up on a flat surface, engine running and bonnet open until the oil comes down under 100c, by then I figure that the turbo has cooled down sufficiently too.
upsidedownmark said:
I certainly don't see any advantage in keeping it running. For turbo cars, you have a very specific case, namely the turbo which is *stupid* hot; if you just switch off, the oil is no longer circulating, so the stuff within the turbo gets cooked, and breaks down. You run the engine to keep the oil flowing until the turbo has cooled, that's all.
For a normally aspirated car, I really can't think of a bad hotspot scenario. If the heat is under control while driving (the cooling system is capable of dissipating what you put in), then there's no particular cooldown requirement. The thermostat opens and closes to take the rad in and out of the equation on the road, to keep the temp up (and down). On the track, you can assume the thermostat is open more/all of the time, but unless the car runs hotter, the system is still coping, and the engine temp is 'within design'. Of course the oil temp and water temp are different - the oil temp may be doing more interesting things.
However, once you switch the engine off, no more energy is being put into the system, so the temperature can only fall. Running the engine is putting energy in, and there's no real cooling flow, so the temperature will only rise. Unless there's a specific hot area that demands you keep oil/water flow (like a turbo), the fastest way to cool it is to switch it off!
As someone else said, the biggest cooling issues on most cars is likely to be the brakes.
On the majority of cars the waterpump will stop (assuming cambelt or aux belt driven).For a normally aspirated car, I really can't think of a bad hotspot scenario. If the heat is under control while driving (the cooling system is capable of dissipating what you put in), then there's no particular cooldown requirement. The thermostat opens and closes to take the rad in and out of the equation on the road, to keep the temp up (and down). On the track, you can assume the thermostat is open more/all of the time, but unless the car runs hotter, the system is still coping, and the engine temp is 'within design'. Of course the oil temp and water temp are different - the oil temp may be doing more interesting things.
However, once you switch the engine off, no more energy is being put into the system, so the temperature can only fall. Running the engine is putting energy in, and there's no real cooling flow, so the temperature will only rise. Unless there's a specific hot area that demands you keep oil/water flow (like a turbo), the fastest way to cool it is to switch it off!
As someone else said, the biggest cooling issues on most cars is likely to be the brakes.
So as soon as you turn off the water does not circulate. Hot Cylinder heads will happily get non circulating water pretty hot!
I actually tend to keep "higher revs" on during cool down, BUT ensuring the load is very low (light throttle). That way to my mind the water pump is effective as possible, whilst not adding significant heat into the engine due to the light load. "High revs" is circa 4500-5000rpm on a 7500rpm engine. Then leave it in the pits for around 5 minutes at idle.
Cool down lap, high gear, low revs Nd try not to use the brakes.
Pits, stop, 1st gear, job done. Pop the bonnet to reduce heat soak in your intake manifold and pipework for your next run.
Unless you cooling system isn't up to scratch then your engine will be plenty cool enough when you get in.
Certainly don't leave it running, all it will do is reach its peak, fan controlled temp while it's idling.
As many have said it's more about cooling your brakes, trains and diff and if you have one your turbo as once you stop these will not see any cooling air at all.
Pits, stop, 1st gear, job done. Pop the bonnet to reduce heat soak in your intake manifold and pipework for your next run.
Unless you cooling system isn't up to scratch then your engine will be plenty cool enough when you get in.
Certainly don't leave it running, all it will do is reach its peak, fan controlled temp while it's idling.
As many have said it's more about cooling your brakes, trains and diff and if you have one your turbo as once you stop these will not see any cooling air at all.
True, the coolant will not circulate. However, the cylinder heads can only get cooler, and the coolant cannot get hotter than the cylinder heads (fundamental physics), whereas when you leave it running, you're putting energy(heat) into a closed system that has lost any ability to sink/reject that heat due to there being no airflow - it will *all* get hotter. Switched off, the worst case is that it boils the water, which is unlikely - CHT should be <200c, more likely <150c in use, and will reduce quickly on the cooldown lap. Also, the coolant is pressurised so it can run hotter than 100c without boiling, and even if it does, it's not going to hurt, unlike cooking oil in a turbo.
Switching it on for a few seconds could have some merit, but really, I think we're over-complicating things. These are mass market cars, not finely tuned race engines living on the edge of killing themselves. That said, when was the last time you saw a F1 car come into parc-ferme and sit with the engine idling? They switch them off pretty much straight away (interesting to see if that changes with the turbo era..)
Switching it on for a few seconds could have some merit, but really, I think we're over-complicating things. These are mass market cars, not finely tuned race engines living on the edge of killing themselves. That said, when was the last time you saw a F1 car come into parc-ferme and sit with the engine idling? They switch them off pretty much straight away (interesting to see if that changes with the turbo era..)
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