Engine Cool-down Strategies for Autocross (Single Driver)

[Brzzee]

During autocross events that allow for pauses (approx. 5—8 minutes) in the grid between runs, I have noticed most drivers in single-driver cars turn-off their engines. Some drivers raise their hoods, some do not.

I have been allowing my engine to idle with the hood up. This allows me to do the pedal dance once. And maintain coolant flow through the engine during my heat of four to six runs.

What cooling strategies might be preferred over what I’m using with my engine?

Findings:
My coolant temperatures measured with OBDII sensors via iPad III w/DashCmd are 192F at idle, 215F at the end of the last run of the day with an oil temperature peak reaching between 240—245F. Idle oil temperatures tend to range 212—218F. Ambient temperatures in the afternoons peak in the high 90s-low 100s with heat index over 100F in our North Texas summers.

Configuration:
I run AMSOIL products. 0/20W Signature during the Spring and early summer, and I now will change to a 5W30 equivalent (product to be used is 0W30) in July-September (see GSpeed Viscosity analysis). Above temperatures were measured in 2016 while using 0W20.

I do not have an oil cooler, though I’m looking to install a water-to-oil cooler of my own design. OEM radiator and fans used with Subaru coolant. APR radiator carbon fiber top shroud installed configured for the OEM air box.

Appreciate any suggestions you might have.

[cjd]

If I need to cool things down (2 driver car for half the events I run, and the last 2 events I'm not convinced it was even 5 minutes between runs) I crank the AC to max. Turn it to the floor vent and toss your helmet under the airflow to help it dry and cool it down. On particularly hot days I pop the hood as well. We typically have 40-60 second courses, most of them toward the longer end of things and dabbling in 3rd gear here and there too.

I always give it a few minutes running to cool down and stabilize before shutting it off at the end of the day - as far as I understand things, this is really the crucial point anywhere through the day though - stable temps. Idling through or shutting down isn't changing a whole lot beyond the amount of gas you burn. I don't think it changes peak temps a whole lot either way.

We've only had one day over 90 so far, so ambient temps play a role here too - the oil cooler wouldn't be much value for me, but I could see it being helpful in your case (assuming average temps are higher for you). Tire temps have been the bigger challenge on such short intervals. I don't mind a 9 run day that wraps up around 2 though.

C

[Brzzee]

Thanks for the helmet cooling idea.

I run the AC while staging and in the grid on particularly hot days. Just need to be careful to turn the AC off --- not hit the BRZ limited start-stop button when you're next in-line to go. ;-) Just once was enough to train my finger.

Already had two days this year that AC refreshed the driver.

Your events similar in time to North Texas region, though the number of cars (165 plus) limits us to four heats with five runs. Rare third gear comes into play.

Several of the STX twins have air-to-oil coolers and at least one a CSP radiator also.

I've got a thermal coated, Koyo radiator, and an after market shroud ready to install.

I've had limited success adapting a Boss Mustang oil cooler kit (water-to-oil) as I've yet to find a location and make a bracket that allows for a remote filter location that is NOT underneath the front bumper.

Good Luck with your season.

[cjd]

Originally Posted by Brzzee

Thanks for the helmet cooling idea.

I run the AC while staging and in the grid on particularly hot days. Just need to be careful to turn the AC off --- not hit the BRZ limited start-stop button when you're next in-line to go. ;-) Just once was enough to train my finger.

Already had two days this year that AC refreshed the driver.

Your events similar in time to North Texas region, though the number of cars (165 plus) limits us to four heats with five runs. Rare third gear comes into play.

Several of the STX twins have air-to-oil coolers and at least one a CSP radiator also.

I've got a thermal coated, Koyo radiator, and an after market shroud ready to install.

I've had limited success adapting a Boss Mustang oil cooler kit (water-to-oil) as I've yet to find a location and make a bracket that allows for a remote filter location that is NOT underneath the front bumper.

Good Luck with your season.

Any reason you're not going with one of the tried and effective oil cooling solutions? The adapted subaru unit that taps into the cooling system doesn't require a remote filter either... I have an air/oil cooler but won't be installing it I think - just not seeing the sustained oil temps to make me concerned, and it's another potential failure point I don't think I need. I suppose I'll discover maybe it would be a good idea the day I sell it...

I've forgotten to turn off the A/C. One thing I liked about my last car is it always shut off A/C at WOT (by design).

9 runs is 90 drivers. Local SCCA limits to 170 this year and we've been getting a consistent 6 runs, though I'm packed up closer to 5. If I drive the other direction (and I sometimes do) I run a different SCCA club where we've done 220... though that may have been 5 runs, memory says it was 6. How fast they could reset the slalom (not far from the start) limited the pace. Always 4 heats where I run, usually split on working as long as we can get proper coverage.

Shroud is interesting, I could see it helping a touch (it obviously doesn't at all for tracked cars, where it can actually hurt). I know cooling stuff has some weird rules on legality, but local I suspect anything to make the car last longer will be OK with folks. Haven't looked too far into it.

[Brzzee]

I have the air-to-oil cooler parts, if the water-to-oil install gets too hard/expensive.

What happened I challenged myself to an W-2-O off-the-shelf parts solution with perhaps a bracket out-sourced. Looked at the $130 shipped 5.0L Mustang cooler from Ford Performance and thought there's got to be a way to make this work, and provide more thermal removal capacity than the FA20DIT cooler. Engine compartment location with easy access to the oil filter has been the driving issue for fitment. Getting closer however.

I would have foregone the shroud I bought in 2013 had Eric at Velox been quicker posting his thoughts on shroud design ;-). Ah, the trials of early adopters. I'm having fun tinkering and learning, that's what matters in my seventh decade.

[Scrappydoo]

Does it need a strategy or would a method do?

[Scrappydoo]

Originally Posted by Brzzee

During autocross events that allow for pauses (approx. 5—8 minutes) in the grid between runs, I have noticed most drivers in single-driver cars turn-off their engines. Some drivers raise their hoods, some do not.

I have been allowing my engine to idle with the hood up. This allows me to do the pedal dance once. And maintain coolant flow through the engine during my heat of four to six runs.

What cooling strategies might be preferred over what I’m using with my engine?

Findings:
My coolant temperatures measured with OBDII sensors via iPad III w/DashCmd are 192F at idle, 215F at the end of the last run of the day with an oil temperature peak reaching between 240—245F. Idle oil temperatures tend to range 212—218F. Ambient temperatures in the afternoons peak in the high 90s-low 100s with heat index over 100F in our North Texas summers.

Configuration:
I run AMSOIL products. 0/20W Signature during the Spring and early summer, and I now will change to a 5W30 equivalent (product to be used is 0W30) in July-September (see GSpeed Viscosity analysis). Above temperatures were measured in 2016 while using 0W20.

I do not have an oil cooler, though I’m looking to install a water-to-oil cooler of my own design. OEM radiator and fans used with Subaru coolant. APR radiator carbon fiber top shroud installed configured for the OEM air box.

Appreciate any suggestions you might have.

Grammar, spelling and punctuation. Go lightly on the fevered sense of self importance?

Let us know how it goes.

Subbed.

[Scrappydoo]

I'm not really subbed. I was taking the piss.

[Spuds]

Maybe I'm confused about the topic or there's something I'm not thinking of, but wouldn't AC increase the temperature in the engine bay? If you are trying to cool down the engine bay in a small time window, then you should definitely leave the ac off. Not sure to what extent the effect would be though. If you want every last bit of engine bay cooling you can get, turning on the cabin heater and opening the windows would also help.

On the other hand, a heat soaked driver is probably worse than a heat soaked engine.

[Scrappydoo]

Baton picked up..

[Brzzee]

You bet.

[bslate3]

Probably easiest and cheapest to install the FA WRX/Forrester XT oil cooler. Also keep in mind DI engines like to run hot.

I don't run an oil coooler (yet, would like to get the factory FA20DIT oil cooler) I do use my tire sprayer occasionally in the highest heat of the summer to spray down the radiator thru the bumper. Haven't had any issues with just autocross. Track 20min+ sessions you'll probably need an oil cooler for sure in the Texas summers.

[cjd]

Originally Posted by Spuds

Maybe I'm confused about the topic or there's something I'm not thinking of, but wouldn't AC increase the temperature in the engine bay? If you are trying to cool down the engine bay in a small time window, then you should definitely leave the ac off. Not sure to what extent the effect would be though. If you want every last bit of engine bay cooling you can get, turning on the cabin heater and opening the windows would also help.

On the other hand, a heat soaked driver is probably worse than a heat soaked engine.

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

[strat61caster]

Originally Posted by cjd

I've forgotten to turn off the A/C. One thing I liked about my last car is it always shut off A/C at WOT (by design).

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.