Incompatibility with upgraded Koyo radiator and PRL High Volume Intake

[Kamikaze5PDR]

I am no longer able to properly mount my PRL High Volume Intake after upgrading to a thicker radiator.

I recently decided to get a Koyo High flow radiator. Although I don’t have heat issues, because I am moving to a hotter climate (desert), I was thinking about ways to help my Integra’s longevity since I’ve been pushing the car more and more with bolt ons.

Before starting work, this is what the engine bay looked like:

I heard mixed reviews on the CSF radiator so I decided to go with a Koyo radiator with a Koyo radiator cap (OEM not compatible). Specs are scarce on Koyo’s website. The link they reference is dead.

The new radiator is about 50% thicker and very well built. Sorry no side shots between the two, but take my word for it.

Install was a pain due to the limited accessibility to the mounting, particularly the bottom 8 (4 on each side) that have a 2”x3” access port to unbolt the 10mm bolts. Fan and shroud were straight forward, same for the disconnect and drain.

When everything was put back in (some rework was required which I will go over some pointers at the end), I looked down and only then realized how much bulk the new radiator added.

The ramp from the high volume intake going to the new box no longer sits flush. This results in the intake duct no longer lining up with box and potentially starving the engine of air (not completely, but but the stock design had a seamless connection from the grill to the filter). I reached out to PRL to see what they recommend but I am not hopeful.

in the meantime, I am thinking about installing a PRL stage 1 Short Ram Intake (SRI). I am fully committed to PRL at this point because of the turbo I let pipe. Not a fan of the SRI because you’ll get more suction noise that mutes turbo spool.

Some lessons learned if you want to upgrade your radiator on your Integra:
1) Radiator and high volume intake are not compatible. Stock air box and SRI okay.
2) You will need to remove intercooler and additional panel forward of the lower engine cover (plus bumper) to remove/install radiator. If you’re unbolting the subframe, you’re taking apart too much stuff and does not improve accessibility. Install is different from a Civic Si.
3) Stock coolant capacity is just under a gallon. You will need about 1.5 gallons (6 quarts/2 bottles of coolant) to fill up.
4) Your radiator fans will automatically switch on when you turn on your heater and will not be a good indicator for when your thermostat opens up to burp the coolant system.

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[Last_ICE]

What is the negative buzz on the CSF radiator?

 

[Kamikaze5PDR]

What is the negative buzz on the CSF radiator?

I’ll compare specs then go into the reviews.

On CSF’s website, they make comparisons between what they are selling vs a CTR in the write up. The claim is that since their product is an improvement for CTRs, their radiator will be an even bigger improvement for FL1/DE4. This is what they show for CSF vs OEM:

The Koyo Rad link worked for me today, but their information is scant but shows this:

I connected the dots by referencing Koyo Rad’s Japan website which describes their F-type 48mm radiator which corresponds to the picture above which reads:
“軽量化することに成功。ラインナップ中最高の性能を誇るKOYORADレーシングのフラッグシップモデルです。・アルミコア　２層タイプ　オールアルミタイプ
・コア厚み　48mm　幅　採用”
-or- translated in English to:
“Succeeded in reducing weight. This is KOYORAD Racing's flagship model that boasts the highest performance in the lineup.・Aluminum core 2 layer type All aluminum type
・Core thickness 48mm width adopted”

Bottom line: It is hard to compare Koyo and CSF spec for spec due to lack of data. Koyo has a 48mm core vs CSF’s 42mm. Koyo radiator seems to be built more robustly from the ground up.

Going back your original question about negative buzz. I found very few objective product reviews for the 5th gen Integra/11th gen Civics. The majority of what I found was regarding other model cars. For people that CSF radiator well for, they rate 5 stars. However there is a large number that have complained about fitment issues and premature failure (hence the 1-2 stars).

In CSF’s defense, they to pay attention to these reviews and has reached out to each person that wrote a negative comment.

Price wise, they seemed to be priced the same ranging from $500-$700 dollars.

The radiator is a pain to remove and install for the Integra because of all the mounting points. When I bought Koyo, I bought based on reputation because this I knew I did not want to chance rework.

 

[Last_ICE]

Thanks for such a cogent reply!

 

[creaturemachine]

This is some good info. I wonder if you could simply cut out the part of the intake where it touches the rad. It all before the filter so it shouldn't affect much. Does the stock intake have clearance?

 

[Baozzer]

This is some good info. I wonder if you could simply cut out the part of the intake where it touches the rad. It all before the filter so it shouldn't affect much. Does the stock intake have clearance?

it would take more engine bay/hotter air though

 

[Kamikaze5PDR]

This is some good info. I wonder if you could simply cut out the part of the intake where it touches the rad. It all before the filter so it shouldn't affect much. Does the stock intake have clearance?

The stock intake clears no problem. The issue is ultimately due to the bracket from PRL being as compact as possible and the scoop sloping down too aggressively. I should have took pictures on how sketchy it look when I tried shoehorning the PRL HVI, but didn’t.

 

[Kamikaze5PDR]

So an update. I sent PRL photos of the issue with the HVI. They reminded me that an upgraded radiator is not a common mod. They recommended I install the HVI without the front bracket. The clips that hold the scoop and HVI keep breaking/popping out with the suggested mod. I went ahead and reinstalled the SRI.
Way ahead is to go to a machine shop to make a bracket or modify/rebrand my current one. I reached out to 27Won to see how far out they are from releasing their HVI/cold air intake.
-or-
I ca double down and get the cold air duct and see if adding a mounting point at the bottom of the box will stabilize the box.

After the clips broke, I have been replacing them with ones from a local hardware store. Getting new clips from PRL directly may help.

 

[Kamikaze5PDR]

I reached own to 27Won to see if they have a solution to my dilemma. They are in process of developing a HVI due out later this year (Q3/Q4). They said 50/50 chance of the larger radiator clearing.
What impressed me more is their professional and sincere response. I looked into the specs of their HVI and it’s impressive and has the potential to be the best of its kind for the L15CA equipped Integras/Civic Si. I envy everyone that bought the 27Won intercooler/charge pipes and turbo inlet pipe. Check out their HVI.
https://www.27won.com/blog/11th-gen-civic5th-gen-integra-intake-system-design-blog-pt-3

 

[creaturemachine]

What impressed me more is their professional and sincere response.

I like that they are willing to make their products work with other aftermarket pieces, such as adapting their turbo inlet to PRL and K&N intakes. PRL's Ti piece looks the business but only works with their airbox.

 

[Kamikaze5PDR]

Update on how I resolved the HVI issue:
I reached out to PRL but have not heard back. The issue stems from the bracket that attaches the HVI box being at a 45 degree angle. I sent PRL the recommended fix and asked that they do not blow off enthusiasts that install aftermarket radiators. I told them people. who want that peace of mind and track their cars need love too.
The long term fix involves making a new bracket. Make sure you use both bracket bolts or your box will twist under heavy winds (snapped my HVI plenum clips).
The cheap fix is taking two zip ties so the box stops shifting.
Another Integra owner pointed out that two-step performance offers titanium fittings for the DE4/Si PRL HVI box. It is listed under 22+ Si parts but fits the Integra perfectly. I would be very suprised if the titanium parts break as easily as the plastic ones provided by PRL.
Of note, the 27Won snorkel marries up beautifully to the PRL HVI.
I hope this update helps and I hope everyone else doesn’t run into the issues I’ve had to deal with.

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