FL5 Track Cooling Experiment: Portable Water Misting the Condenser/Radiator & Intercooler (Data from 99°F Texas HPDE)

[johnloov]

FL5 Track Cooling Project – Water Misting the Condenser/Radiator & Intercooler/ (Let's See If We Can Improve the Stock Cooling System)

I've been chasing one goal since buying my FL5:

Can a completely stock FL5 Type R reliably survive repeated summer HPDE sessions without requiring expensive aftermarket cooling upgrades?

Rather than immediately replacing the radiator, intercooler, oil cooler, etc., I wanted to first understand how Honda engineered the cooling system and see how far the stock package could be pushed using basic engineering and physics.

The mister is an amazing $59 dollar solution, that not only kept my temps in check on one of the hottest days, it also instantly made my A/C run Ice cold right after coming off track it used to take many minutes to get cold, and it was able to get my A/C blowing Ice cold in about 30 seconds. I also tried it on the way home on the highway. I would toggle it on and off, and I could feel the noticeable difference.

Without - Mister OFF - Water Temp 235F

With - Mister On - Water Temp 213F - Same exact hottest location on track

My Track Experience on Stock FL5 ( -3 Negative camber, Castrol SRF Fluid, Endless Endurance Circuit CC43 (N35S) brake pads )

No overheating

So far I've completed:

• 20+ HPDE days at WeatherTech Raceway Laguna Seca
• 6 HPDE days at Circuit of the Americas (COTA)
• 2 HPDE days at G2 Motorsports Park (Dallas)

That's more than 28 track days on the factory cooling system.

The car still has:

• OEM radiator
• OEM intercooler
• OEM condenser
• OEM coolant-to-oil heat exchanger
• OEM transmission cooling

No aftermarket cooling components.

For oil I've consistently run:

• Honda Ultimate OW-20 & Pennzoil Ultra Platinum 0W-20 ( circulates faster, lower engine temps )
• Oil changes every 2–4 track days (~2,000 miles)

Oil Analysis
Instead of guessing, I've also been sending oil samples to Blackstone Laboratories after track use.

My latest report was after:

• 2,111 miles
• 3 track days

The report came back extremely clean.

Blackstone's comments were:

"This is a spotless report... Wear metals are all steady... Fuel wasn't a concern... Moisture, coolant, and excess dirt stayed away... Nice addition to the file."

Wear metals remained very low, and there was no evidence of coolant contamination or abnormal engine wear during this interval.

Obviously this doesn't prove a cooling strategy works by itself, but it has given me confidence that the engine has been handling repeated track use well with my maintenance schedule.

My Heater Procedure
One thing I've done since my very first HPDE is run the heater.

For anyone unfamiliar:

The heater core is simply another heat exchanger.

My procedure has always been:

• A/C OFF
• Temperature set to maximum heat
• Driver vent closed
• Center vents pointed toward the passenger window
• Passenger vent pointed toward the passenger window
• Blower fan OFF
• Recirculate ON

Even with the blower OFF, coolant still circulates through the heater core when the temperature is set to HOT, allowing it to reject some heat.

It's not comfortable, but it has become part of my normal track routine.

Using this method, I have never experienced limp mode or an overheating shutdown.

Understanding the FL5 Cooling Stack
One thing I don't think gets discussed enough is how Honda arranged the FL5 cooling system.

From front to back:

1. Intercooler
2. A/C condenser
3. Engine radiator

The condenser sits directly in front of the radiator.

The radiator doesn't just control coolant temperature.

Because of Honda's coolant-to-oil heat exchanger and the transmission's thermal relationship with the engine cooling system, radiator performance also affects:

• Engine coolant
• Engine oil temperature
• Transmission temperature

Everything ultimately depends on how efficiently the radiator can reject heat.

My Observation
I've noticed a trend while reading various FL5 build threads.

Many people install:

• Larger radiators
• Auxiliary oil coolers
• Bigger intercoolers

Yet many of those systems are still stacked in the same airflow path.

Some owners are still reporting coolant temperatures similar to—or even higher than—what I'm seeing with my completely stock cooling system while running the heater.

That got me thinking:

Instead of only increasing cooling capacity, can we improve the efficiency of the existing heat exchangers?

My Water Misting Experiment
That led me to evaporative cooling.

Using a removable battery-powered mister:

https://www.amazon.com/dp/B0GRTJ4CJW

I installed:

• 4 fine-mist nozzles aimed at the condenser/radiator stack
• 2 fine-mist nozzles aimed at the intercooler

Everything is removable.

No permanent modifications.

First Track Test
Location:

G2 Motorsports Park

Date:

Saturday, July 11, 2026

Weather:

• Ambient approximately 99°F
• Heat index approximately 103°F

Configuration:

• Heater ON
• A/C OFF
• Water mister ON

Results
I completed repeated 30-minute sessions.

I never entered limp mode.

I never experienced an overheating shutdown.

The limiting factor for me became tire performance, not coolant temperature.

After the sessions, I also checked for water leakage and did not observe water dripping onto the racing surface. The water appeared to evaporate very quickly as it contacted the hot condenser/radiator stack.

One interesting observation:

While testing the system on the highway, turning the mister on made the A/C noticeably colder almost immediately, suggesting the condenser was definitely being cooled.

This Is NOT Me Claiming I've Solved FL5 Cooling
I don't think we're there yet.

This is simply an engineering experiment that I'd love to see more people help develop.

Questions I'd like to answer include:

• Is a finer mist better than larger droplets?
• Where is the best locations to spray
• Is there a way to spray between the condenser and radiator?
• Is condenser-only spraying better than condenser plus intercooler?
• What nozzle pressure is ideal?
• What flow rate is ideal?
• Does a higher-pressure pump improve evaporative cooling?
• How much coolant temperature reduction is actually achievable?
• How much can charge-air temperatures be reduced?
• Can we mist the brake as some race cars do to cool brakes including brake ducting.

I'd Love Community Input
If you're tracking an FL5, I'd love to see your:

• Coolant temperatures
• Oil temperatures
• Intake air temperatures
• Ambient temperatures
• Cooling modifications
• Data logs
• Photos
• Ideas

Maybe this experiment goes nowhere.

Maybe we discover that a simple removable water mist system can make the stock cooling package more effective during extreme HPDE conditions.

Either way, I'd rather answer the question with data than assumptions.

Let's see what we can learn together.

Anyone else tried a water misting solution to cool their cars?

 

[Sooner1]

Where do you have the water reservoir mounted?

Off topic question: with so many track days what are you doing for brakes?

 

[johnloov]

The mister came with 4 gallon water reservoir and it is behind passenger seat and I put ice in it also but need to replace it with a more water tight cooler.

Brakes are stock, paragon titanium shims, Castrol SRF Fluid.
I've gone through 3 OEM rotors in front an 1 in rear.

Pads - Paragon are trash compared to Endless Endurance Circuit CC43 (N35S) brake pads. Paragon R5's wore inconsistently, always warped {tapered wear - never level wear } terrible squeal, extreme heat, ate the rotors. They were actually the biggest piece of Trash I was using on my car. And I went through several of them, until I ordered the Endless Endurance Circuit pads that last 2x longer, wear extremely consistent - perfect. They are superior day and night difference. They are easier on the rotors, have actually a higher temperature rating than paragon, and after the first braking corner, they are absolutely 100% consistent on every lap after.

You can order them from Japan Blackhawk website, but they do take 1.5 months to make, and are like only $175 dollar or so. The Front pads last about 2-3x longer than rear pads.

I will soon add ducting, to reduce the brake caliper temps by another 100F degrees and will also try misting it in the center of the brake rotor and as it spins and air flows from the duct, it will cool the rotors instantly and constantly from the center out.

Spoon uses a similar duct - I'll try this next, take readings then add water misting also if it's not enough.

Wow - I just ordered another 3 sets of brake pads on sale $129 from Japan. Also - to complete the picture - I am running with Type R mode on and traction control reduced - not completely off - I've spun out twice with everything off and have seen too many type R's in the wall. I am heating the brakes and still they are excellent. I will probably rebuild them soon with new rings and boots.

I am totally curious if misting the rotors from the inside also will help keep them cooler as well and reduce cracking of the brake rubber boots.

https://www.blackhawkjapan.com/prod...Yjn86FEVmua8jThcIanPAPr6yufyv-yonJXUNEYInbEu0

 

[nomtimesthree]

Love the idea and thanks for sharing. Is there anything preventing a cleaner/more permanent install where all the components are in the engine bay or maybe the trunk? Older STIs had an intercooler water sprayer with the reservoir in the trunk, roughly where the sub is in the FL5. Or even the windshield fluid reservoir could be tapped into.

 

[johnloov]

The misting works well - but you need like 2-3 gallons for a 20 minute track session - for sure you can mount something more permanent - my current setup is for track days - just run the hose and then keep the 4 gallon tank behind seat

 

[marcusm86]

I will soon add ducting, to reduce the brake caliper temps by another 100F degrees and will also try misting it in the center of the brake rotor and as it spins and air flows from the duct, it will cool the rotors instantly and constantly from the center out.

Spoon uses a similar duct - I'll try this next, take readings then add water misting also if it's not enough.

I would suggest you consider warpage when thinking about misting the brake rotor.. i would suspect it would trash the rotor pretty easily

 

[Cueyo]

Maybe this is a question that misses the mark, but if the intent is to keep the engine performing optimally on hot lap 3 or 4 of a track day, then would it also be possible that the added sprung mass from the water would undo any gains? Have you seen any changes on your lap time? I actually really like this idea since it screams backyard engineer to me, but I gotta Wonder if my skills are to the point where weight changes would impact my times.

 

[Xmetal]

Maybe this is a question that misses the mark, but if the intent is to keep the engine performing optimally on hot lap 3 or 4 of a track day, then would it also be possible that the added sprung mass from the water would undo any gains? Have you seen any changes on your lap time? I actually really like this idea since it screams backyard engineer to me, but I gotta Wonder if my skills are to the point where weight changes would impact my times.

4 gallons of water weighs about 33lbs, which most of it can be offset with a light weight battery. But I think the intent of it is to not only to keep the engine performing optimally, but also to be able to stay on track, longer without overheating?

 

[nomtimesthree]

that’s a LOT of water. I wonder if similar, significant cooling results can be achieved with less water. The STI reservoir is < 1 gal IIRC, but only for the intercooler, and intermittent spraying not continuous like your setup.

The misting works well - but you need like 2-3 gallons for a 20 minute track session - for sure you can mount something more permanent - my current setup is for track days - just run the hose and then keep the 4 gallon tank behind seat

 

[Cueyo]

I was thinking that there could be potential to offset that 4 gallons if you were to repurpose the washer fluid reservoir. Won't have as much water but depending on where the drain/output of the reservoir is, it could be pretty easy to swap it back to normal after a track day (assuming you have the fittings).

 

[Two Step Performance]

Very cool out of the box solution.

 

[johnloov]

On track, you are not loosing much speed with 30 lbs - if anything. I almost set the stock production car front wheel drive lap record at laguna secs with 165lbs of extra sound deading. Only the Elantra N with and Automatic and professional driver was faster. Adding some weight to your car is no issue, unless you are racing professionally. Trying to keep your engine from cooking, is more important and having tires that can last consistently, and brakes that last consistently lap after lap is the most important.

 

[nttran98]

Similar to home AC units, probably should used distilled water and distilled water ice. Else the carbon build up eventually gonna mess with your rads and stuffs.

 

[kjechel]

My procedure has always been:

• A/C OFF
• Temperature set to maximum heat
• Driver vent closed
• Center vents pointed toward the passenger window
• Passenger vent pointed toward the passenger window
• Blower fan OFF
• Recirculate ON

Awesome idea and writeup. Why Recirculate ON? Doesn't that pull hot air from inside the cabin as opposed to using outside air? Or do you think your cabin air is cooler than outside?

 

[johnloov]

Recirculate on for me - no brake dust pulled into interior cabin during hard track laps - fan off, still it's working, and not cooking even more the interior

Regarding distilled or not - no difference as it's the same as driving in the rain - nozzles may builtd up calcium deposits - it's an experiment so far

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