CSF FL5 Civic Type R High-Performance Dual Engine Oil Cooler Kit

Design & Engineering

The initial challenge when designing this engine oil cooler kit was two fold. Firstly, the K20C1 did not come with any type of external engine oil cooler provision. The second challenge was space in which to mount an external engine oil cooler(s). The front bumper opening already has the Intercooler, A/C Condenser, and Radiator stacked there and using most of the available air.

While mounting an additional cooler behind the grill is the simple option, that just adds more heat to the full system and takes away from the cooling capacity of the radiator. On top of that, most owners who track their cars will have an upgraded/larger intercooler which further compounds the issue. That means the sides of the bumper are the obvious and optimal placement. However, the FL5 does not have great airflow in that area. To improve airflow, CSF needed to design a ducting/inlet system that would allow proper airflow for optimal performance.

With proper airflow handled, CSF built the kit around our compact universal oil coolers (CSF #8119), using two of them to offer the greatest cooling capacity possible. Paired with Superstrasse CPE lined stainless steel braided lines and DYME Pro/Spec Quick Release Fittings, this kit is the most serviceable kit on the market.

Oil Coolers

The CSF kit is built around two 13" x 4.5" (33cm x 11.5cm) Dual-Pass Oil Coolers (CSF #8119) run in series. These High-Performance Coolers offer maximum heat dissipation with uncompromising durability. The Bar/Plate cores feature CSF's "Aero-Flow" Bar Design which reduces weight while offering impressive strength and flow. The rugged design of these cores means you won't need to worry about debris from the track puncturing the coolers like with tube and fin cores.

The 100% TIG welded construction with cast end tanks further increases the overall strength of the coolers. Every cooler is pressure tested to 120 PSI before leaving the factory so you can be confident you will never have one burst on you like some weaker designs used in other kits. The end tanks also feature specially designed 40-degree angle feed/return fittings for optimal flow and lower pressure drop.

Oil Cooler Key Features:

• Bar/Plate Core offers strength and durability
• 100% TIG Welded Construction tested to 120 PSI
• Smooth 40-degree feed/return fitting design
• Dual Pass flow for additional cooling
• Oil Capacity increased by over 2 Quarts (2 Liters)

The are the same coolers Honda Racing Corporation (HRC formerly HPD) uses on Honda's factory FK8 TCR Touring Car. Honda and many racing teams/drivers saw a lot of success with the FK8 Type R TC. CSF is already working with teams like Precision Racing LA for their FL5 Touring Race Car and in talks with other SRO teams and HRC themselves.

Pressure Drop

When adding an engine oil cooler to a car that did not come with one from the factory, there is always a concern with pressure drop. This is due to the back pressure imposed on the system from running the oil through lines and cooling channels of an oil cooler.

In testing, CSF observed a small drop in oil pressure after installing the kit. While not a concern for casual driving, it was enough of an issue to address for those tracking their FL5s. To resolve this issue, CSF and test vehicles switched to a higher weight oil (from OE Spec 0W-20 to 0/5W-30) and this relieved the potential pressure issues.

CSF recommends the following oil weights depending on application:

• Light Track Duty and/or High Performance Street: 0/5W-30
• Heavy Track Duty and/or Dedicated Race Builds: 0/5W-40

Lines, Fittings, and Thermostat

CSF partnered with DYME PSI again for their exceptional quality and innovative quick-release hose and fitting solutions. The DYME Pro/Spec Quick Release Fittings offer race-proven performance with the convenience of tool-free clamshell removal and capable of withstanding up to 10,000 PSI. Quick Release fittings make the installation of the CSF kit much faster than traditional threaded fittings. In addition, they make maintenance like fluid changes much less of a headache.

The DYME PSI fittings are hydraulically crimped to their motorsport quality Superstrasse CPE lined 304 stainless steel braided lines. DYME PSI manufactures these lines and fittings in house to CSF exact specifications with the highest level of quality and precision. These lines offer the best flexibility, flow, and chemical resistance possible.

Oil flow is managed by a Billet Aluminum thermostatic sandwich plate. This plate bolts in the factory oil filter location with a M20x1.5 adapter. The sandwich plate was designed to reuse the OE oil filter but can be fitted with a larger filter up to 70mm in diameter with a M20x1.5 thread (check height clearance when looking at filter options).

The thermostat is designed to start opening at 175°F (80°C) and be fully open at 195°F (90°C), great for motorsports and high-performance street applications. The sandwich plate also includes a pre-plugged 1/8 NPT port for aftermarket oil temperature sensors. This is a great addition for drivers looking for more accurate data/metrics.

Key Features:

• Fittings:

• • • Forged 6061-T6 Aluminum Body
    • 180° Swivel Adjustment
    • Dual FLUOROK™ FKM Seals
    • Chemical & Heat Resistance up to 401°F (205°C) continuous operation temperature
    • Secure & Permanent Crimp-On connection for high-pressure systems
  • Lines:
    • 304 Stainless Steel reinforcing braid and Polyethylene top braid
    • Burst pressure of over 2000 PSI
    • Suitable for up to 302°F (150°C) continuous operation temperature

• Sandwich Plate:

• • Billet Aluminum Construction
  • 175-195°F (80-90°C) Thermostat
  • Accommodates OE Filter or others up to 70mm in diameter with a M20x1.5 thread
  • 1/8 NPT Pre-plugged Port for Temperature Sensor

Ducting & Vents

The challenge of getting proper air flow to the oil coolers was straightforward but far from simple. While mounting an additional cooler behind the grill would be the easy choice, that just adds more heat to the rest of the cooling system. The optimal placement for the coolers was in the sides of the bumper outside of having no direct airflow. While technically some air does flow to this area as it leaks around the intercooler, it is not enough for significant cooling performance. While utilizing the brake cooling ducts is a potential option, that could negatively impact braking performance.

CSF designed and modeled vents for the bumper to provide the two oil coolers with ample airflow to keep engine oil temperatures in check. These vents were carefully designed with CFD software for airflow and aero dynamics. Made from pre-preg carbon fiber, these vents match the lines and style of the FL5 and give a very OEM+ look to the front bumper. To further improve airflow and cooling, the kit also includes louvered vents that allow airflow out of the bumper area and into the fender wells.

OE Fit and Finish

CSF leveraged many industry connections to find the best possible source for motorsport grade carbon fiber. The quality, fit, and finish of these parts are of the highest caliber and have been extensively track tested. Each vent bolts on without the use of double sided tape so they are very secure.

Cut out templates are included with the kit instructions to allow for easy installation and ensure proper alignment. CSF also designed templates for the international market with FL5s that come equipped with PDC sensors. The factory PDC sensors will still function perfectly and retain the OE look and feel.

While there may be kits available that do not require cutting the bumper, they cannot match the airflow and cooling performance of the CSF kit.

Air Duct Key Features:

• Motorsport Grade Pre-Preg 2x2 Carbon Fiber Construction
• OE level fitment and finish
• Provides optimal airflow to the Oil Coolers vs kits with air deflectors from the center opening
• Instruction include cut out templates for easy install with motorsport grade hardware (no tape)
• Laser Cut Louvered Vents for airflow into the wheel wells

*Note: Carbon fiber vents can be refinished as in matte clear or painted. CSF recommends using a qualified paint or body shop for best results.

Duct Development and Testing with Dustin Williams - dustiinw

CSF was fortunate enough to have Dustin Williams (@dustiinw) loan out his car to the engineering team for final testing and refinement on the bumper vents. CSF owner Ravi Dolwani delivered the final prototype kit with the final design of the vents in person and Dustin's reaction was great. He thought the vents match the style of the car so well that they should have come from the factory like that.

Replacement Windshield Washer Reservoir

To make room inside of the right hand side bumper for both the oil cooler and proper airflow, CSF designed a replacement windshield washer fluid reservoir. This low clearance reservoir/bottle works with the factory pump and filler neck. The engine bay retains a clean factory look while freeing up space in the bumper for the cooler.

Testing and Results

CSF spent over a year in testing and development of this kit working with R&D Partners and multiple drivers competing in Global Time Attack (GTA) and GridLife. Initial testing was performed in the controlled environment of a dyno. CSF then moved into aggressive real world testing and development on the track where most customers would be using these kits.

Dyno Testing

For initial testing, CSF turned to the automotive authorities and industry experts at MotoIQ for third party verified data collection. Mike and the team there developed the testing procedures for the prototype baseline data. Temperature readings were taken with two temperature sensors installed at the oil filter housing/sandwich plate for the most accurate readings. The FL5 was first run for 9 consecutive pulls on the dyno at World Motorsport to simulate hard driving and engine oil heat soak. The prototype CSF Oil Cooler Kit was then installed and the same test was conducted again. Average ambient temperature was only 0.5°F (0.3°C) higher on the test with the CSF kit.

You can see from the results the CSF prototype kit offered consistently cooler engine oil temperatures throughout the test. On average the engine oil temperatures were about 9°F (5°C) cooler with the CSF kit installed. While the max temperature seen was only 222°F (105.5°C), this gave the engineering team a great comparison data point. This test was performed before the addition of the fender liner vents.

While the dyno is a great place to begin testing, the track test results reveal dramatic reductions in engine oil cooler temperatures under extreme conditions.

Track Testing

GridZilla - Michael Baxi

CSF was also able to do some track testing with Michael Baxi (@GridZilla) at Laguna Seca. Here is a side by side comparison of a hot lap temperature with both laps being Michael's PB's for that day. Please note these temperature readings are from the onboard Honda monitoring system that does not use an actual Oil Temperatures sensor. The oil temperature on the dash display is calculated by combining data from actual sensors (coolant temp, load, engine speed) via the onboard computer.

Testing showed the CSF Oil Cooler kit provided a 17°F (10°C) average reduction in engine oil temperatures and 20°F (11°C) reduction in engine coolant temperatures during both PB hot laps. Michael said he saw as much as 30°F reductions in engine oil temperatures and 24°F lower coolant temps that day.

Test Notes:

• These tests were done before adding the fender liner louvered vents behind the oil coolers. The addition of these vents offers even more cooling capacity and heat soak resistance.
• These tests were also done with the first bumper vent prototypes which were smaller and less aerodynamically optimized.

I have been tracking on the Type R platform since 2019 (FK8) and more recently the FL5 for the last couple of years. Like many, I was struggling to get the Oil temps under control. Pushed hard enough, the FL5 just like the FK8 before it would overheat and pull power making days over 65F ambient temps impossible to track on. I tried the typical off the shelf "solutions" before eventually landing on the CSF kit and all that the other solutions did was delay the inevitable.

Now with this CSF Dual Oil Cooler kit I am seeing real results for the first time. My power levels are way up from the last time I tracked my car (372whp>470whp), it was a few degrees warmer outside than last time and I still saw a 24F drop in coolant temps and a 30F in oil temps! Not only is this the best solution I've come across for the FL5 platform but I'd say it's a necessity for anyone seriously looking to track their FL5 Type R!

Videos of both hot laps & a track map for reference:

OE Lap

CSF Lap

J5_FL5 – Johnny Hernandez

CSF's other main test car was Johnny Hernandez' (@j5_fl5) Time Attack build. Johnny has been competing in Global Time Attack (GTA) for years in the Street FWD and Street AWD classes. He purchased the FL5 early in 2024 and immediately began track testing it in stock configuration at Buttonwillow. It was very apparent that the car had major heat issues.

Johnny began his time attack build in the middle of 2024 where he reached out to CSF about cooling solutions. Because his car was getting a fully built motor, larger turbo, and a long list of upgrades (see build list here) to push the FL5 platform as much as possible, he wanted the best cooling solution available. Adding the CSF High-Performance Radiator (#7221) and PRL Intercooler (which uses a CSF core) were the easy answer for him. Timing worked out perfectly for CSF to get him the prototype Engine Oil Cooler kit that was still in development. He was eager to try out the kit and was a crucial part of the development and refinements you see today.

Johnny's FL5 produces 520 whp & 417 wtq.

Global Time Attack

The car debuted at the GTA Finals at Buttonwillow in November of 2024 finishing 7th overall in the Street Class and was the second fastest with FWD. Definitely not a bad showing for the first official race. The results and feedback from this race help the CSF engineers make some improvements to the kit and help prepare for the 2025 season.

With updates to the kit Johnny's 2025 season was very successful in GTA with him setting the Street FWD lap record at Circuit of the Americas (COTA) with a time of 02:25.025. Throughout the 2025 Season, Johnny has reported that he has no major issues with overheating.

I've been testing CSF's Dual Oil Cooler setup on my track-prepped 2024 Honda Civic Type R for most of 2025 now and it has performed flawlessly. Oil temps remain stable even after multiple hot laps, letting me focus on driving instead of watching gauges and worrying about temperature management. It's become a critical part of my track reliability setup when everything is pushed to the limit.

Johnny Hernandez

1fastvc - Nguyen Vo (Built by Evasive Motorsports)

CSF wanted to ensure there was ample test data from a variety of FL5 owners. Nguyen Vo (@1fastvc) was referred to CSF by our industry friends at Adro Inc. Nguyen is an avid track enthusiast that has built and tracked full blow race cars. However, with the FL5 he wanted to take a more balanced approach making his Civic Type R a very streetable track weapon. This build by Evasive Motorsport strikes a near perfect balance of show and go.

Nguyen tested the production version of the CSF Engine Oil Cooler Kit with fantastic results. When first tracking the car he recorded engine oil temperatures of 247-251°F (119-122°C) in stock configuration. With the CSF Kit, Full Bolt On (FBO) upgrades, and Tuning, Nguyen never saw oil temperatures above 240°F (115°C). The temperatures stayed in the 230°F (110°C) range for the majority of the time on track. Temperature data for all testing was collected through Hondata datalogging.

⚠ Fitment Notes

FL5: Installation of this kit requires modifications such as cutting/trimming the front bumper, fender liners, brake ducts, and installing rivet nuts on the crash beam rails.

DE5: Installation of this kit would require modifications such as cutting/trimming the factory bumper side grills, fender liners, brake ducts, installing rivet nuts on the crash beam rails. The CSF Bumper Vents are not designed for the DE5 and would require modifications to the factory front bumper side inserts for proper airflow to the coolers.