Overheating & What You Can Do To Stop It

Lust

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As we all know, the FK8 struggles when driven hard on track. It seems like everyone has the same story of "I overheated today and the ambient temps were 75F+" or "car cut power and I had to pull into the pits" or something along those lines. There are several things that can put the car into limp mode and those being, hot coolant temps, hot oil temps, or fuel starving. Unfortunately Honda did not adequately design the coolers on our car to handle heavy track use. In comparison, the FK8 radiator is half of the size of other hot hatches. Another thing to note is that the intregreated head design and outdated/inefficient turbo do no favors for cooling.

Related Threads:

C&R Radiator
C&R Oil Cooler
C&R Intercooler

Common Misconceptions:

Most people that try to address overheating will slap on a larger intercooler thinking that it will help. In most cases this will actually make the car more likely to overheat. Let me explain. By increasing the size of your intercooler, you restrict the amount of airflow that travels through the intercooler and into the radiator. The radiator can't do its job without having the appropriate amount of airflow. The job of the intercooler is to cool the charge air and not to cool the water. By consistently making more power due to lower intake air temps (IAT), you increase the thermal load. It can get to a certain point, especially on track, where those benefits actually become useless. Essentially what has now happened is you lowered IATs, great. Coolant temps now rise as a result and the car cuts your power anyways. At this point the car is in double jeopardy. You lost power that you wanted to gain through a larger intercooler and your coolant temps are also suffering because of it. If you feel like you need to upgrade your intercooler, stick with a tube and fin design. C&R makes the best intercooler in this category and I have a thread on that as well. You’ll want to avoid a bar and plate intercooler if your car sees serious track duty. Reason being is that they restrict too much airflow and are much heavier compared to tube and fin units. Once a bar and plate unit gets heat soaked, it becomes very hard to shed this heat. On track where the car consistently sees WOT, it’s more beneficial to have a tube and fin intercooler that will consistently shed that heat .

Another thing to avoid would be inefficient base tunes. By increasing the power through tuning, you increase the thermal load on the car exponentially. The car already struggles with its current setup stock and this is a common mistake people make. From experience, KTuner runs the coolest out of all the base tunes available. I HIGHLY recommend against ANY Hondata base tune. For reference, we had two owners running Hondata basetunes on their car here at Laguna Seca. Both cars overheated quite easily with a decent driver. Another owner and I advised them to revert to the stock tune. The temp gauge didn't budge the rest of the day and their times didn't suffer much at all. I'm not picking on Hondata but this proves how inefficient their base tunes are especially for track work.

Some owners make the mistake of switching oil viscosity to something excessively thick thinking it will help reduce temps. In fact, thicker oil INCREASES heat. The engine now has to work harder because the thicker oil creates more friction. In extreme cases you can lose a bit of power. These engines are built to very fine tolerances and perform very well with modern synthetic oils. A thinner oil can travel faster and dissipate heat easier than thicker oil. 0w-20 to 5w-30 should be enough for most people depending on driver and car setup. It is important to monitor your oil pressures to determine which weight is suitable for you. The rule of thumb is 10 psi for every 1,000 rpm. At high load for the FK8, you should see 55-65 psi. If your pressures are low, there is an issue with your setup and/or you need to move to a thicker oil. For serious track use it is very important to use an oil that will not sheer under high load or high temp. What can end up happening is a low grade 5w-30 oil sheering down to 0w-20 under high temp without you even knowing it. I’ve used Motul 300v 0w-20 on track and on the street with excellent results. I’m not guessing on this either. I sent my oil for analysis over at Blackstone and even with track use they recommend up to a 10,000 mile oil change interval.

Solutions:

The first thing we want to address is increasing the thermal capacity of your radiator and oil cooler. The stock radiator is so small it's laughable. Well why don't we just stuff the largest radiator possible? Unfortunately if the radiator core is too thick, it will decrease cooling efficiency. Finding the right core size to cool the car and also be efficient is extremely tricky. Most options on the market have been tried without any success. This includes: 2020 OEM, Koyorad, MASIV, CSF, and Spoon. Luckily for us there's one option, C&R/PWR. I've picked their brain's on almost everything cooling and have come to find that they can provide a radiator sufficient for serious track work. I won't harp on it too much on this thread but initial testing seems extremely promising from other owners and myself included. Essentially the C&R can shed heat like no other and is truly unique compared to everything else on the market currently. The coolant mixture can also be played around with depending on your climate. I live in California and can get away with the majority of my coolant being water with water wetter and some Honda coolant mixed in.

To help reduce the strain on the radiator, an oil cooler is necessary. The radiator design on our car is tasked with cooling not only the water but also the oil. By adding an auxiliary oil cooler, we can help reduce both ECT and OilT. The best designs currently available are ones mounted behind the driver side fog light. This way you can cut holes in the grill to allow air to pass through the oil cooler and the oil cooler only. There are some options that mount in the front of the radiator or require you to delete the brake duct. I HIGHLY recommend to stay away from these options. USR, GReddy, HKS, and C&R are all great options. Choose one that will suit your driving needs.

Radiator and oil cooler would be considered bare minimum and should be the first things you look into when tracking your car.

Now that we have a larger radiator, we want maximize the amount of air coming in. The more air that comes into contact with the radiator the better. When looking at the front bumper design, the only way to increase air into the radiator would be a larger grill. There are several options out there and even the 2020 models took note of this. If you can properly duct the air coming into the intercooler/radiator even better. Keep in mind, by increasing the opening, you will unfortunately increase drag/lift.

With more air coming into contact with the radiator you'll want to extract that heat as quickly as possible. The stock hood and even some vented hoods are not great at extracting heat and the air inside the engine bay becomes lazy. Poor airflow behind the radiator increase engine bay temps all across the board. You'l see higher IATs, ECTs, OilTs, etc. This is where a properly vented hood comes into play. My recommendation would be to have a vent right above the turbo. This will help the air escape the hottest parts, the radiator and turbo, as quickly as possible. Varis, Js, and Trackspec all have good options for this.

The icing on the cake will be isolating the heat sources in the car with thermal barriers. This includes: reflective tape, thermal wrap, thermal coatings, etc. A large source of heat will come from the factory downpipe/catalytic converter. The best solution here would be to run a catless downpipe with titanium wrap or an inconel shield. A good example would be the FK8 TCR where the downpipe has an inconel clam shell around it. I understand that not everyone wants to live that catless life, in which case I recommend a thermal coated catted downpipe like the RV6 Performance. Fair warning, it is not recommended to titanium wrap your cat. Wrapping the cat can lead to overheating and premature failure. To improve the hot air exiting the exhaust, a larger front pipe can help. This piece sits right below the oil pan and it is highly beneficial to titanium wrap this piece to minimize heat soaking into the oil pan. Thermal shielding on the intake parts can be beneficial too. If the intercooler doesn't need to work as hard, you wont have as much hot air exiting the intercooler as a result.

For those desperate enough, you can delete the AC condenser. This will allow a significant amount of air to flow through the radiator and also save weight. Not suitable IMO for a daily driver but definitely an option for a dedicated track car

My Personal Recommendations:

This is in order of importance.

Radiator: C&R street or track depending on your specific needs
Oil Cooler: C&R, HKS, GReddy, USR
Grills: Modified OEM, EVS, Js Racing, etc
Vented hoods: Varis, Js Racing, Trackspec hood vents
Catless Downpipes: RV6 ceramic coated, Dream Automotive with hard lagging, or PRL
Thermal barriers: DEI, Heatshield Products, Turbosource. You'll want to use reflective tapes, inconel shields, titanium wraps, etc where applicable.

There are some brute force ways of cooling the car like Ethanol, Meth injection, and upgraded turbo. I won't go into these options only because the average user probably doesn't want to dive that deep into the rabbit hole.

This is my basic recipe for solving the overheating problem. There's definitely multiple ways to solve it but I feel this is the most streamlined way of doing it. I'd love for this thread to be a place to discuss advanced ideas and theories to help further reduce temps. If you've done exactly everything above please share your experience with us.

I'll continue to update this post as more information becomes available or if I simply forgot to talk about something.
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remc86007

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Nice summary. I think far too many discussions on this forum are derailed by people confusing high IAT power reductions with the car actually overheating. You can have 175F intake temps and be running perfectly acceptable coolant and oil temps. Fixing IATs is easy; fixing the engine cooling problem is hard.

Also, this is only a problem for people driving hard on a hot, lower speed track. If you haven't experienced climbing ECTs in your use cases, don't waste your money on cooling mods. This car will not under any circumstances overheat in street driving.
 

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Great thread, Lust. I would also recommend against the base tunes for any heavy track work simply because every engine is different and needs that extra bit of love under those extreme conditions. They're not dangerous, but they can definitely be heavily improved on. Thats why theyre basemaps, though.

If you haven't experienced climbing ECTs in your use cases, don't waste your money on cooling mods. This car will not under any circumstances overheat in street driving.
I can confirm that it will NEVER overheat in street driving, even in the ridiculous summers of Florida. I don't even have heatshields installed and I can drive around the street and highway hard when it's 95 degrees out on my custom tune and my ECTs will still never go above 210F at worst, and only for a moment. I'm running no cooling mods other than a PRL intercooler. Never have I ever had my R to into limp mode. I'll heatsoak and eventually see IATs of 160F at idle, but I will only lose some boost, not go into limp mode.
 

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If memory serves, C&R had two radiator options: Street and Track. Is the Track option a bad idea for a car that sees a majority of street driving (with occasional track use)? Wondering if it will be too large for the typical street driving speeds to get air flow in.
 


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What are your thoughts on the Acuity coolant lines that swap the direction of flow through the radiator? From a thermodynamics and heat transfer perspective it makes sense. Curious if anyone has seen an improvement or reduction in performance.
 

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Great thread, Lust. I would also recommend against the base tunes for any heavy track work simply because every engine is different and needs that extra bit of love under those extreme conditions. They're not dangerous, but they can definitely be heavily improved on. Thats why theyre basemaps, though.


I can confirm that it will NEVER overheat in street driving, even in the ridiculous summers of Florida. I don't even have heatshields installed and I can drive around the street and highway hard when it's 95 degrees out on my custom tune and my ECTs will still never go above 210F at worst, and only for a moment. I'm running no cooling mods other than a PRL intercooler. Never have I ever had my R to into limp mode. I'll heatsoak and eventually see IATs of 160F at idle, but I will only lose some boost, not go into limp mode.
Lust & Kefi,
You guys are good.

I'm in NW FL and it gets over 95 here sometimes. I run Race Chip that you prolly aren’t familiar with yet. It adds up to 81whp and thus produces more heat obviously.

To offset that I added K’rad dual core aluminum radiator that at least one of you sees as a mistake as you say it can decrease efficiency. I haven’t had any overheat issues street driving and have yet to insulate anything. Temps are rock solid AOK this far on this ‘19 R.

This weekend though causes concern as an Autocross event on a low speed short track could cause issues, find the weakest or hottest point. Sessions are just 3 laps that take on average 50 seconds a lap and if not spending too much idle time prior, hoping it will be ok. Just 7k miles and running OEM coolant mix.

I thought the radiator would help and still think it can’t hurt. With no airflow improvements, are you confident this is worse than nothing, maybe helps shed heat a little faster? I always do couple minute warm up and at least one min of cool down at home with a directional blower aimed at radiator/intake inlet (on top of a chest freezer). I got some insul tape (roll) but I think that won’t do much even if I take out inlet pipe and wrap it. Any advice appreciated asit seems you might suggest RV6 DP and C&R street version of radiator instead, maybe grill upgrade to 2020?

Thanks for your time and feedback.
 
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Lust

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If memory serves, C&R had two radiator options: Street and Track. Is the Track option a bad idea for a car that sees a majority of street driving (with occasional track use)? Wondering if it will be too large for the typical street driving speeds to get air flow in.
I highly recommend the track version to anyone that does more than a couple events a year. I’m daily driving mine i

What are your thoughts on the Acuity coolant lines that swap the direction of flow through the radiator? From a thermodynamics and heat transfer perspective it makes sense. Curious if anyone has seen an improvement or reduction in performance.
The explanation makes sense to me but I honestly don’t think it helps much. I’d love to see some more real world data on it. I asked C&R/PWR and they also said it might help but probably

Do oem fans run at high speed or do they shut off over certain mph?
I know the fans kick in around 190F. The fans do become rather useless around 35-45 MPH since you have more air coming in at speed compared to the fans. My guess is that the fans actually turn off at this point? I’m not sure.

Lust & Kefi,
You guys are good.

I'm in NW FL and it gets over 95 here sometimes. I run Race Chip that you prolly aren’t familiar with yet. It adds up to 81whp and thus produces more heat obviously.

To offset that I added K’rad dual core aluminum radiator that at least one of you sees as a mistake as you say it can decrease efficiency. I haven’t had any overheat issues street driving and have yet to insulate anything. Temps are rock solid AOK this far on this ‘19 R.

This weekend though causes concern as an Autocross event on a low speed short track could cause issues, find the weakest or hottest point. Sessions are just 3 laps that take on average 50 seconds a lap and if not spending too much idle time prior, hoping it will be ok. Just 7k miles and running OEM coolant mix.

I thought the radiator would help and still think it can’t hurt. With no airflow improvements, are you confident this is worse than nothing, maybe helps shed heat a little faster? I always do couple minute warm up and at least one min of cool down at home with a directional blower aimed at radiator/intake inlet (on top of a chest freezer). I got some insul tape (roll) but I think that won’t do much even if I take out inlet pipe and wrap it. Any advice appreciated asit seems you might suggest RV6 DP and C&R street version of radiator instead, maybe grill upgrade to 2020?

Thanks for your time and feedback.
The Koyo is a decent radiator but unfortunately doesn’t have sufficient cooling capacity for serious track work. It’s thicker than OEM which is good so it can handle and dissipate more heat. The size isn’t the problem in this case, it’s their core and fin technology. It just isn’t able to shed as much heat as the C&R. For auto cross the C&R street version might be better suited
 

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In principal, I agree with everything you are saying. Do you have numbers that back up the various mods? I am not asking this to argue anything; I would like to know how effective each of these changes are. Not only for the mods that work, but also for the ones that fail. For example, 'properly hood venting results 10 additional minutes of aggressive track time.' Running in a spec class, I would like to improve cooling although I am very limited in allowed mods. Since the turbo and inlet seem to generate a lot of heat, I intended to focus on that. But, if I need to vent the hood to let the heat escape, then I am SOL.
Thanks
 


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Good write up! This looks like a recipe for success! Thanks for putting in your personal money and time to research then sharing the results with the community.
 
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Lust

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In principal, I agree with everything you are saying. Do you have numbers that back up the various mods? I am not asking this to argue anything; I would like to know how effective each of these changes are. Not only for the mods that work, but also for the ones that fail. For example, 'properly hood venting results 10 additional minutes of aggressive track time.' Running in a spec class, I would like to improve cooling although I am very limited in allowed mods. Since the turbo and inlet seem to generate a lot of heat, I intended to focus on that. But, if I need to vent the hood to let the heat escape, then I am SOL.
Thanks
That would be hard to quantify honestly. I personally don’t have all of these modifications to be able to test in a scientific fashion. My data is gathered from other users that I am friends with who attend track days. What modifications are you allowed? Maybe we can start there
 

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How about running a flex fuel setup tuned to stock power levels?
Run much less boost, generate less heat, produce OEM levels of hp and tq.
 
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Lust

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How about running a flex fuel setup tuned to stock power levels?
Run much less boost, generate less heat, produce OEM levels of hp and tq.
That certainly is a solid option. However you’ll need a whole lot to make ethanol viable. You’ll need bigger injectors, fuel pumps, an ethanol content analyzer, and tune.
 

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I think just a flex fuel kit and a tune. Would not run 100% E85, maybe 30% or so would suffice to drop the boost 3-4 psi and still be at 300hp/300tq.
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