The BJR FD RX-7 radiator has a large surface area and is substantially thicker than most radiator options on the market. However, airflow is the key component for any heat exchanger. It does not matter how efficient a radiator is, if air is not going through the core, it cannot do its job. At low speeds (~<40-50mph) the radiator fan and shrouding are the primary source of airflow through a radiator. At higher speeds, any form of ducting or fans actually become a restriction to flow and hurt the cooling ability of the radiator.
To achieve a good balance of low and high-speed cooling, we decided to use (2) 11-inch 1,190 CFM High Performance Puller Fans from GC Cooling. This gives us 2,380 CFM of airflow at 16.8 amps per fan. The shroud is minimal, which will help the fans pull from more of the radiator, while rectangular openings allow for more airflow at higher speeds. The bottom opening feeds the power steering cooler from Hayden Automotive.
GC Cooling might not be as well known in the cooling fan world as SPAL, but GC has an interesting background. GC is an Italian manufacturer that started in 1982 and was the original electric motor supplier for Spal for many years. The two companies eventually parted ways and continue to make (albeit similar looking) cooling fans to this day. SPAL’s product line is derived from their OEM applications, whereas GC has taken a more boutique approach and is more flexible with creating combinations of fan blade, size, depth, motor size, etc.. to dial in the packaging and cooling requirements for any application. For example, there could be packaging limitations in the fan shroud depth but not the motor height. In order to maximize cooling performance, the combination of a very tall motor can be put on a thin fan shroud to maximize the packaging limitations where this combination might not be an off-the-shelf offering from SPAL. If you have any cooling fan needs, custom or off the shelf, reach out to GC Cooling.
We chose the 7-row, 4.4” x 13” Hayden Automotive (776) “HD COOL” Heavy Duty Engine/Transmission cooler for the RX-7’s power steering system.
The Hayden Automotive “HD COOL” oil coolers are 37mm thick heavy-duty plate/fin heat exchangers that are ideal for transmission and engine oil cooling requiring higher flow range and increased heat transfer capacity in a compact space. Their patented internal turbulation increases heat transfer and provides minimal pressure drop and use 37* JIC male flare (-12) fittings
Hayden Automotive has been around since 1961 when founder Perry Hayden invented the automotive transmission cooler after modifying a refrigerator condenser to extend the life of his tow vehicle’s transmission. Over the past 60 years, Hayden has become powertrain cooling experts serving OEM manufacturers with engine, transmission, and power steering coolers, as well as radiator fan clutches. Hayden holds multiple patents in how coolers operate that help maximize efficiency without sacrificing flow, along with many radiator clutch fan design patents.
Due to Hayden’s decades of experience manufacturing these types of heat exchangers, and due to their very affordable price points, the Hayden oil coolers are a no-brainer when it comes to cooling engine, transmissions, differentials, and power steering systems.
We mounted the Hayden (776) Power Steering Cooler directly to the shroud, behind the coolest part of the radiator’s dual-pass flow. We have had success with mounting power steering coolers of this size behind radiators in Pro-Touring style resto-modded muscle cars and trucks that compete on road courses, so given the significantly larger capacity and cooler efficiency, we have a lot of confidence in this setup keeping our power steering cool. We had to cut off the side mounting plate for clearance to the fans.
By comparison, the stock power steering cooler is this metal hard line that zig-zags in front of the radiator. There is very little surface area to this cooler, which is known to be insufficient and the cause of boiled power steering fluid in extreme conditions.
5 comments
Fantastic update and all the custom work on the cooling system is so cool to read about. I am patiently waiting to see this thing finally unleash some HP!
Technically, you should have a ‘blade’ that bifurcates upper, and lower flows at the start of the duct. If you modeled this in CFD, there would be obvious turbulence that could easily be avoided.
Cheers.
Was about to comment the same thing.
Also, the air out of the IC needs to go somewhere… I don’t remember what the hood looks like for this project, but a proper vent with gurney flap and ducting would do wonders at speed.
Can’t wait to read the next articles.
It’s not that crucial to bifurcate the ducting. Many morern OEM cars don’t separate the inlet ducting of a common duct/plenum that feeds multiple heat exchangers because airflow is not laminar in the ducting and the important aspect here is creating a pressure differential across the heat exchangers. Proper ducting that seals the air from the front bumper to the heat exchanger creates a high pressure area on the front side of heat exchangers in the V-mount setup (or “L”-mount in many OEM applications) when using a common plenum (or air box, or radiator ducting).
I am currently in my FD build and would love to have one of these radiators, could y’all please guide me in the right direction to purchase one if they are available. I left a message on the BJR site to no avail. HELP…..someone??