Engine Cool-down Strategies for Autocross (Single Driver)

[nico_rsx]

Originally Posted by cjd

It's simply a way to force all the fans on. The load is negligible.

The load may be negligible, but the radiator will be drawing super hot air from the condenser. Wouldn't that affect the radiator capacity to remove heat?

[Ultramaroon]

Originally Posted by nico_rsx

The load may be negligible, but the radiator will be drawing super hot air from the condenser. Wouldn't that affect the radiator capacity to remove heat?

How hot do you think the condenser gets?

Pro-tip: Crank the blower up high pulling fresh air so the evaporator isn't able to get too cold.

Otherwise if the evaporator gets cold enough, like when the blower is turned down low, a thermostat will start cycling the compressor (and fan) to keep it from frosting up.

[cjd]

Originally Posted by strat61caster

I was under the impression that the 86 shut off the ac under load as well, is there any reason why you think it doesn't?

Don't get me wrong, I'm not advocating leaving the ac on, but I've felt it shut off when driving around and I put my foot in it, merging onto the freeway for example. Maybe the BRZs climate control overrides it on max cool? I've left it on for a run or two by accident and didn't even notice until after the fact, but I can tell when it's sapping power when driving around...

In any case, I'm in the 'hood open let it idle camp' right now, if the oil temp was really that dangerous on the stock system we'd see a lot more blown up 86s, I'm starting to think getting the engine up to temp before a run is the most critical. But as a daily driven car I'm interested in the Jackson racing combined radiator, idk it it's STX legal but I'm cheap and probably won't do it unless I start tracking again.

I suppose it may, not sure. I'm not sure I'd notice once on course. Maybe I should.

The Jackson radiator runs afoul of one of the "does nothing else" rules. Pity, its an attractive setup. Assume it passes on dimension and weight and mounting.

C

[cjd]

Originally Posted by nico_rsx

The load may be negligible, but the radiator will be drawing super hot air from the condenser. Wouldn't that affect the radiator capacity to remove heat?

Its not as hot as the engine/coolant, and air movement is the key. You need it to stabilize temps in grid. I think you could get an 86 nanny that had a fan switch... You can always spray the condenser/radiator down a bit.

C

[Somerandom18]

Get spray nozzles and hook them up to your wiper fluid. Have them spray the radiator. 😂

Sent from my Pixel XL using Tapatalk

[nico_rsx]

Originally Posted by Ultramaroon

How hot do you think the condenser gets?

I work in the HVAC industry, but we don't use the same refrigerant as cars. I'm guessing the air leaving the condenser could be around 115F.

[Ultramaroon]

Originally Posted by nico_rsx

I work in the HVAC industry, but we don't use the same refrigerant as cars. I'm guessing the air leaving the condenser could be around 115F.

Exact isn't important. We agree that there's at least 70-80F difference between condenser and engine coolant.

Also, we know that the heat transfer from condenser to air is limited, blah blah blah...

Forced induction through the cooler stack at slightly elevated temp will still be far more effective than letting it sit in stagnant air.

[Locust]

I thought installing oil coolers wasn't allowed in Street/Street Touring?

This has devolved into a discussion about air conditioning but there are still other things you can do to cool the car down.

1. Always pop the hood. Under hood temps get really high.
2. Spray your radiator, intake box, and engine cover with water.
3. Lay a bag of ice on top of your intake box.
4. Buy some high speed battery powered fans and point them at your engine, radiator, etc. (yes the legality of this has been checked).

[M0nk3y]

Originally Posted by Locust

I thought installing oil coolers wasn't allowed in Street/Street Touring?

This has devolved into a discussion about air conditioning but there are still other things you can do to cool the car down.

1. Always pop the hood. Under hood temps get really high.
2. Spray your radiator, intake box, and engine cover with water.
3. Lay a bag of ice on top of your intake box.
4. Buy some high speed battery powered fans and point them at your engine, radiator, etc. (yes the legality of this has been checked).

Oil Coolers are legal in ST trim

14.10.A

A. Oil pans, oil pickups, and differential covers may be modified or substituted. Addition or modification of windage trays or crankshaft scrapers is not allowed. Engine oil, transmission fluid, differential fluid, and power steering fluid coolers may be added or substituted (including oil to coolant heat exchangers) but may not serve any additional purpose.

[Brzzee]

Thanks for all the discussion in the different paths it has taken.

Refining the topic:

Is allowing the engine to continue running a better or worse solution than turning the engine off when parked then back on to make the run?

One point made was that other than more fuel burned, continuous running did not appear to make a difference.

Other thoughts?

[dattran86]

Originally Posted by Brzzee

Thanks for all the discussion in the different paths it has taken.

Refining the topic:

Is allowing the engine to continue running a better or worse solution than turning the engine off when parked then back on to make the run?

One point made was that other than more fuel burned, continuous running did not appear to make a difference.

Other thoughts?

i usually pit, let the engine run for about a minute or two. then shut it off, hood opened

[cjd]

Originally Posted by Brzzee

Thanks for all the discussion in the different paths it has taken.

Refining the topic:

Is allowing the engine to continue running a better or worse solution than turning the engine off when parked then back on to make the run?

One point made was that other than more fuel burned, continuous running did not appear to make a difference.

Other thoughts?

I was taught never shut it off immediately, that stops all circulation of oil and coolant. The question is how long to run it. Is the trip back to grid enough? I like to see temps stabilize as I've said, that may take a couple minutes.

C

[Spuds]

Get an IR thermometer. Try cooling it off one way, then point the thermometer at the engine block in various locations, recording the temps. Do another run. Try cooling a different way, then point the thermometer at the same locations, and record data. Repeat as many times as possible.

Then let us know what you found.

Notes:
Make sure you let it cool down for the same amount of time.
Take before and after measurements then look at the differences.
Average results for each method over as many runs (of the test) as possible. Sample size is important with this amount of uncertainty in the experiment.

[Wepeel]

If I'm single driving, I'll pull back into grid and let it idle while I shutoff camera/data and reset tire pressures (usually a few minutes), then I'll shut off engine. I've found oil temps drop more when shutting the engine off vs. leave it idling.

If codriving, we usually just let it idle, but if turnover is uncharacteristically slow we'll shutoff.

Hood up always.