Help solve a debate - engine cooling and AC

[LostInTransit]

So I'm assuming that vented hoods are not allowed? and what about things like my 3D printed air ram setup? is one allowed to remove the skid plates?

 

[tri-pedaler]

So I'm assuming that vented hoods are not allowed? and what about things like my 3D printed air ram setup? is one allowed to remove the skid plates?

No x 3 - Street class means stock for these things. I do remove the engine cover (is that even allowed? Oh well).

 

[foodtruck]

Rules are strict in surprising ways, for example poly rear motor mount will send you to STH even tho it would realistically result in zero time improvement. You _can_ however change out rear shocks (and even make them adjustable!) which _may_ very well result in better handling

 

[M-Sport fan]

The more and more I hear these rules for AutoX makes me stick to road courses lol. Unless theres something I don't know, a radiator isn't going to give you a power advantage in AutoX. Unless you don't have time between sessions to cool down

Why I totally gave up on SCCA Autocross/Solo many many years ago.

Arcane, asinine, draconian rules which almost always favor the rides of those actually making said rules (yes, even with the supposedly considered 'member input' at the end of each season), or the majority of the 'go-to' cars running in a given class.

 

[M-Sport fan]

The real measure would be Fan On No AC vs Fan On w/ AC. You're running a heat pump and pulling cabin heat into the engine with the AC on, it's just a very bad idea to add that extra heat and then try to blow it away with a fan when the entire goal is to cool the engine.

Real question is whether you'd be allowed to run a box fan blowing at the radiator when you're off-track. Seems like that would be a cheap and (maybe, dunno) legal way to achieve the same thing without running the AC condenser pump

The fan will come on without the AC engaged eventually in hot enough weather, at idle or otherwise, but not until the coolant reaches a ridiculous temp, almost bordering on head gasket obliteration, and head warpage (like what 225*F or more??).
It comes on instantaneously as soon as the AC is engaged, at any coolant or ambient air temp, at least in my car.

Yeah, that over-ride switch would be a godsend.

 

[slopoke]

I'm assuming that you are running Redline Water Wetter or something similar? If not, try using some and see if it helps any. Also, I don't know if you are running a 50/50 mix of coolant or not. I'm assuming that you are not, since it's a competition. But if you are, try going to straight water with a Water Wetter chemical

. If you can afford it or have access to a 110vac plug, get a couple of box fans and place them under the car to help cool during pit breaks. Good luck.

I just read all of the prior posts and see that the box fan option was mentioned. Maybe you can borrow a small portable generator for power for the fans. If not, I did a quick check for rentals, Sunbelt charges $39.00 a day for a 1000 watt Honda inverter generator.

 

[SteveS]

For a fan: https://www.homedepot.com/p/Milwauk...bsite-Fan-Tool-Only-0886-20/205846390#overlay

Put it in front of the radiator you're spraying the water mist on. The cooling power of evaporation is much greater than just airflow.

 

[Williamson]

I can attest to running the heat to limp the car through sections that would overheat it. I was on the stock radiator until literally a couple days ago and have taken it just fine to the track in the summer. But I needed to run full heat during the session depending on how the heat was creeping up, and idling with it going helped drop it faster than not. However my sincere suggestion is to accept that you can't run in stock and replace the radiator so it doesn't overheat. Keeping the car running is more important to me than staying in a super strict stock class.

 

[M-Sport fan]

For a fan: https://www.homedepot.com/p/Milwauk...bsite-Fan-Tool-Only-0886-20/205846390#overlay

Put it in front of the radiator you're spraying the water mist on. The cooling power of evaporation is much greater than just airflow.

That's pretty cool (no pun intended).

I wonder how long each battery would last at the full 284 CFM setting?

 

[SteveS]

That's pretty cool (no pun intended).

I wonder how long each battery would last at the full 284 CFM setting?

Milwaukee says

17 hours with a M18™ REDLITHIUM™ XC 5.0 battery

when running on the low setting. It also comes with an AC adapter for longer running, which wouldn't help much at an autocross. But of course if you use Milwaukee tools like we do at the shop, you own many batteries. We have three big ones and two little ones.

But comments on Milwaukee's page for the fan indicate that a full workday on the high setting only took the battery down to 2 bars from 5.

 

[WannabeST]

Speaking out from personal experience;
With data from the street and canyons the AC on keeps my car at around 180-185 coolant temp (Note* base engine and stock cooling system) when cruising or in traffic. Having the AC on puts approx 25% more load on the engine based on obd2 data (ranges from 24-27% load- I haven't noticed anything to effect these loads, but the range is minimal for in my opinion).
When I was at gridlife running for 2 days straight I tried multiple combinations to try to edge out every ounce of my 90whp. I tried running with heater on to windshield, to feet, AC on, AC on in pits then after, etc. Every single session I basically tried a different combination.
Ultimately the fastest combination was the car turned off while sitting on grid and I didn't turn it back on until we were heading out, During the run I had the heat on full blast to my feet. My feet also get cold easy so maybe it was a driver comfort thing? but it got me to the podium so I will continue this method regardless.The fastest lap was done on the 3rd hottest session out of 8 for the weekend. So could have been better in a morning session.
Second fastest setup was leaving the car on in grid with heat to my toes full blast and driving that way also. This time was approx 4 tenths slower than the PB lap but this run was done on the second coldest session of the weekend.
The third fastest lap of the weekend was done when I had the car on max AC in the pits, the temps would occasionally drop to 177 degress and then I kept the AC on max on the out lap and 2 turns before starting my first hot lap I switched the car to max heat to my feet. This was 0.8 tenths off the PB lap and was done on the hottest session for the weekend.
There's multiple variables here with tire temp, ambient temp etc. but this info may help you out.
From what I felt, after putting heat to the windshield it felt slower for a while, maybe those motors stay on for a bit after?
AC cooling seemed most effective when put on max settings.
This is a track I have driven about 2 dozen times. And overall, my times for the entire weekend were within 1.2 seconds (Besides first session - I forgot to drop PSI from street psi)
Hope this helps you in some way

 

[Dialcaliper]

Thinking a bit harder about this, the A/C trick might work better than I was thinking. Typically older cars, the fan controlled by the A/C comes on high no matter the vent blower setting, but the A/C compressor cycles to maintain condenser pressure and evaporator pressure, so it’s not running 100% of the time. The A/C is most efficient with the condenser running at its coolest, so even our variable speed fan might be running on high.

It’s pretty clear that our ECU is programmed to use the variable speed fan “efficiently” in normal operation, and isn’t programmed to deal well with post-full-send heat soak. I even remember a mention about the Stratified tunes advertising that they use more aggressive cooling fan settings.

So what you want is to maximize fan and minimize compressor on-time. I’d suggest experimenting with one of the two following ideas:

- A/C on, cabin fan on LOW vs HIGH

- Defrost on HI - the defrost runs the A/C compressor to dry the cabin air, and should also be running the cooling fan at increased rate. The compressor will not be working as hard to bring the evaporator temperature down, as it’s just trying to condense it, and you have the added advantage that you’re also using the heater core to pull heat out of the engine.

Either way, worth a shot. It’s really just a question of whether the increased cooling fan settings outweigh the thermal and mechanical load from the A/C system. I can see it working on some cars and not others depending on how the A/C system and the cooling fan settings are set up.

“Stock Class” autocross rules are a best attempt at a concept doomed to fail - making a low cost “showroom” class while attempting to make multi-make classes “fair”. While they have to draw a line somewhere, ultimately anywhere they draw it will be stupid no matter what.

Multi-Make Classes can’t really be made with specific rules for every single one of hundreds (thousands?) of specific car models, and any rule needs to be made with a broad stroke that covers every car in the class

That basically means that despite the ever common situation where you want your car to be stock/class if not for “not even just the tip?” exceptions for specific flaws, it simply doesn’t work.

If you just want to autocross for fun, and don’t car, many local orgs will let you run in an inappropriate but “catch-all” class like the new “Street Extreme” classes. Because you’re not actually trying to compete for points right?

Sadly like any event that’s ultimately rule book racing, there will be “peer pressure” to be properly classed and also

 

[Dialcaliper]

Speaking out from personal experience;
With data from the street and canyons the AC on keeps my car at around 180-185 coolant temp (Note* base engine and stock cooling system) when cruising or in traffic. Having the AC on puts approx 25% more load on the engine based on obd2 data (ranges from 24-27% load- I haven't noticed anything to effect these loads, but the range is minimal for in my opinion).
When I was at gridlife running for 2 days straight I tried multiple combinations to try to edge out every ounce of my 90whp. I tried running with heater on to windshield, to feet, AC on, AC on in pits then after, etc. Every single session I basically tried a different combination.
Ultimately the fastest combination was the car turned off while sitting on grid and I didn't turn it back on until we were heading out, During the run I had the heat on full blast to my feet. My feet also get cold easy so maybe it was a driver comfort thing? but it got me to the podium so I will continue this method regardless.The fastest lap was done on the 3rd hottest session out of 8 for the weekend. So could have been better in a morning session.
Second fastest setup was leaving the car on in grid with heat to my toes full blast and driving that way also. This time was approx 4 tenths slower than the PB lap but this run was done on the second coldest session of the weekend.
The third fastest lap of the weekend was done when I had the car on max AC in the pits, the temps would occasionally drop to 177 degress and then I kept the AC on max on the out lap and 2 turns before starting my first hot lap I switched the car to max heat to my feet. This was 0.8 tenths off the PB lap and was done on the hottest session for the weekend.
There's multiple variables here with tire temp, ambient temp etc. but this info may help you out.
From what I felt, after putting heat to the windshield it felt slower for a while, maybe those motors stay on for a bit after?
AC cooling seemed most effective when put on max settings.
This is a track I have driven about 2 dozen times. And overall, my times for the entire weekend were within 1.2 seconds (Besides first session - I forgot to drop PSI from street psi)
Hope this helps you in some way

I’d be careful with shutting the car off hot. While it might cool down the coolant inside the radiator and temperature sensor (which is on the exterior of the engine, intake side) faster, the core of the block itself (which is the actually really important part) will stay hot and cooling unevenly can be a bad thing. Not only that, but while the metal is still hot, the heat from the cylinders and head like the exhaust manifold and valves (which are quite a bit hotter than the coolant) will continue to heat the coolant that’s not being carried away. The coolant and important areas slightly away from the chamber (like head gasket) can potentially get *hotter* before it begins cooling down. In addition, the uneven cooling that happens when coolant is not flowing can potentially cause thermal stresses and warping.

Might be occasionally okay on an N/A engine that’s not under all that much stress but it’s still not a good idea, but a on a turbo motor with an uncooled exhaust manifold that’s running at 600C++, the block and the little turbo itself that’s just been wrung within an inch of its life may not be so happy.

TL;DR - lots of heat stored in nearby metal, especially on the exhaust manifold side. Be aware of where the sensor is vs where the heat actually is without the coolant circulating.

 

[WannabeST]

I’d be careful with shutting the car off hot. While it might cool down the coolant inside the radiator and temperature sensor (which is on the exterior of the engine, intake side) faster, the core of the block itself (which is the actually really important part) will stay hot and cooling unevenly can be a bad thing. Not only that, but while the metal is still hot, the heat from the cylinders and head like the exhaust manifold and valves (which are quite a bit hotter than the coolant) will continue to heat the coolant that’s not being carried away. The coolant and important areas slightly away from the chamber (like head gasket) can potentially get *hotter* before it begins cooling down. In addition, the uneven cooling that happens when coolant is not flowing can potentially cause thermal stresses and warping.

Might be occasionally okay on an N/A engine that’s not under all that much stress but it’s still not a good idea, but a on a turbo motor with an uncooled exhaust manifold that’s running at 600C++, the block and the little turbo itself that’s just been wrung within an inch of its life may not be so happy.

TL;DR - lots of heat stored in nearby metal, especially on the exhaust manifold side. Be aware of where the sensor is vs where the heat actually is without the coolant circulating.

The turning the car off is only a pre session thing. When we grid before hand. When it’s the end of a session I always do a cool down lap and still drive around the pits a little. I wouldn’t just shut it off after 20 mins of abuse lol.
I leave the hood propped open to let it cool too.

 

[tri-pedaler]

Why I totally gave up on SCCA Autocross/Solo many many years ago.

Arcane, asinine, draconian rules which almost always favor the rides of those actually making said rules (yes, even with the supposedly considered 'member input' at the end of each season), or the majority of the 'go-to' cars running in a given class.

Locally people don’t care much if your off the rules a little. Nationally is another story, rightly. But I try to be a straight shooter regardless

 

[tri-pedaler]

Thinking a bit harder about this, the A/C trick might work better than I was thinking. Typically older cars, the fan controlled by the A/C comes on high no matter the vent blower setting, but the A/C compressor cycles to maintain condenser pressure and evaporator pressure, so it’s not running 100% of the time. The A/C is most efficient with the condenser running at its coolest, so even our variable speed fan might be running on high.

It’s pretty clear that our ECU is programmed to use the variable speed fan “efficiently” in normal operation, and isn’t programmed to deal well with post-full-send heat soak. I even remember a mention about the Stratified tunes advertising that they use more aggressive cooling fan settings.

So what you want is to maximize fan and minimize compressor on-time. I’d suggest experimenting with one of the two following ideas:

- A/C on, cabin fan on LOW vs HIGH

- Defrost on HI - the defrost runs the A/C compressor to dry the cabin air, and should also be running the cooling fan at increased rate. The compressor will not be working as hard to bring the evaporator temperature down, as it’s just trying to condense it, and you have the added advantage that you’re also using the heater core to pull heat out of the engine.

Either way, worth a shot. It’s really just a question of whether the increased cooling fan settings outweigh the thermal and mechanical load from the A/C system. I can see it working on some cars and not others depending on how the A/C system and the cooling fan settings are set up.

“Stock Class” autocross rules are a best attempt at a concept doomed to fail - making a low cost “showroom” class while attempting to make multi-make classes “fair”. While they have to draw a line somewhere, ultimately anywhere they draw it will be stupid no matter what.

Multi-Make Classes can’t really be made with specific rules for every single one of hundreds (thousands?) of specific car models, and any rule needs to be made with a broad stroke that covers every car in the class

That basically means that despite the ever common situation where you want your car to be stock/class if not for “not even just the tip?” exceptions for specific flaws, it simply doesn’t work.

If you just want to autocross for fun, and don’t car, many local orgs will let you run in an inappropriate but “catch-all” class like the new “Street Extreme” classes. Because you’re not actually trying to compete for points right?

Sadly like any event that’s ultimately rule book racing, there will be “peer pressure” to be properly classed and also

I’ll give defrost a try. I don’t have an AP or other device I measure temps, so I unfortunately this won’t be as scientific as I’d like.
I always keep the car idling between runs and pop the hood, so that’s out of the way.
I should also probably do a coolant flush in the off season. My car still has Motorcraft Orange 😳

 

[M-Sport fan]

“Stock Class” autocross rules are a best attempt at a concept doomed to fail - making a low cost “showroom” class while attempting to make multi-make classes “fair”. While they have to draw a line somewhere, ultimately anywhere they draw it will be stupid no matter what.

Multi-Make Classes can’t really be made with specific rules for every single one of hundreds (thousands?) of specific car models, and any rule needs to be made with a broad stroke that covers every car in the class

That basically means that despite the ever common situation where you want your car to be stock/class if not for “not even just the tip?” exceptions for specific flaws, it simply doesn’t work.

If you just want to autocross for fun, and don’t car, many local orgs will let you run in an inappropriate but “catch-all” class like the new “Street Extreme” classes. Because you’re not actually trying to compete for points right?

Sadly like any event that’s ultimately rule book racing, there will be “peer pressure” to be properly classed and also

If the SCCA really wanted to keep costs down in the Street/Stock class, they would require full factory suspension, and 300 tread wear or greater tires (unless the car is new, and came with sub 300 tread wear donuts right from the factory).

Of course then both they, and the competitors would lose all of those contingency/sponsorship buck$ from all of the tire manufacturers.

There are still tons of coin spent, even in that class with it's current rules, at a Nationals level of competition.

 

[scooter123]

The only option you have is to run with your heater set on MAX and the heater fans running full blast. Yeah the interior will get hot, so freakin what. When my Monte Carlo SS was still relatively new I used to run the heater at max when towing my 24 foot boat. That was a 720 mile drive from north of Detroit to Lake George, NY and back every summer. Back around 1996 I said it was time for an upgrade to So I built up a .060 over 350 with 6 inch rods and all the goodies, including a 700 dollar 2 pass BeCool radiator sized for NASCAR. No more need to run the heater, that radiator kept that engine dead on at 180 degrees no matter what the temps were, even while idling in Buffalo waiting for an hour for traffic to clear.

I'll also note that this particular ruling is specifically intended to keep the WRX in the winners circle. Which is absolute total BS. If it weren't for this crap rule the Fiesta ST would still be the HS class leader. This isn't the first time SCCA has pulled this crap and won't be the last.

 

[tri-pedaler]

The only option you have is to run with your heater set on MAX and the heater fans running full blast. Yeah the interior will get hot, so freakin what. When my Monte Carlo SS was still relatively new I used to run the heater at max when towing my 24 foot boat. That was a 720 mile drive from north of Detroit to Lake George, NY and back every summer. Back around 1996 I said it was time for an upgrade to So I built up a .060 over 350 with 6 inch rods and all the goodies, including a 700 dollar 2 pass BeCool radiator sized for NASCAR. No more need to run the heater, that radiator kept that engine dead on at 180 degrees no matter what the temps were, even while idling in Buffalo waiting for an hour for traffic to clear.

I'll also note that this particular ruling is specifically intended to keep the WRX in the winners circle. Which is absolute total BS. If it weren't for this crap rule the Fiesta ST would still be the HS class leader. This isn't the first time SCCA has pulled this crap and won't be the last.

Feeling some things toward the SCCA! I’m fine with the organization l, and the WRX doesn’t compete in HS - it is the top dog in STH though, so perhaps that’s what you’re thinking?
I’d encourage anyone who hasn’t to come out to a local event - it’s a good community, and the SCCA rules are pretty out of sight and mind until you’re at a national event from what I understand.
But a radiator upgrade would be nice…

 

[Williamson]

Feeling some things toward the SCCA! I’m fine with the organization l, and the WRX doesn’t compete in HS - it is the top dog in STH though, so perhaps that’s what you’re thinking?
I’d encourage anyone who hasn’t to come out to a local event - it’s a good community, and the SCCA rules are pretty out of sight and mind until you’re at a national event from what I understand.
But a radiator upgrade would be nice…

Believe me, it's worth it. The car is great stock but those weak points really kill it for hard use. I'm not sure what all you could do to keep it in a reasonable class if you upgrade the radiator but I'd say if you do you may as well take it to that class limit