Radiator Recommendations

Old 03-04-2018, 06:48 AM
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Default Radiator Recommendations

Hi Guys,

Im starting to pull together the parts for my next LS swap and Im looking for recommendations for a cooling system. My last build I used the FM kit and it worked well however the temp would rise in slow traffic. During my last build I lived in the Northeast but since then Iíve moved to the Deep South and Im a little concerned about overheating during the summer. For this swap Iíll be using a LS3/525 and this Miata will be a weekend cruiser no track time. Iíd be interested in hearing your thoughts on the best cooling system for this build.

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Old 03-04-2018, 09:16 AM
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I think FM's double pass radiator is about the best you'll find. Use a minimal amount of antifreeze; around 20-25%. Duct it well, including the hood, and put in a very large fan. Air flow is critical. If you can, try and run the engine on e-85 in the summer.
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Old 03-12-2018, 10:03 PM
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Overheating is one of the biggest problems that I wanted to not solve but conclusively smash when i did the design for my build. From all of the radiators I saw I was not entirely convinced that they would do the job effectively enough. In Australia it is quite common for ambient temperatures in summer to clear 40 deg Celcius (107 deg F) with very high humidity for a long part of the day. Air con in these instances is mandatory and the chance of getting the car to overheat is very high.

From all the reading I have done the majority of the low cost "summit racing style" aluminium radiators will be marginal ta best. The Flyin Miata radiator claims to be the best out there but even it could be improved from my observations (fan air flow and core construction) and for a Ford application as in my case the hose inlets needed modification.

In the end I built my own. the details are:
  1. 685mm wide or 26.96 in (you can't go any wider as it wont fit in between the frame rails). Even this is super tight 2-3 mm of clearance only
  2. Core thickness is 52 mm or 2 inches
  3. Height is 457mm or 18 Inches
  4. Material is Brass (This thing is HEAVY, but it will last forever )
  5. Fans are 2 x SPAL 11in SPU-IX-30102800 (combined air flow of 3200cfm)
  6. Custom shroud with air bypass flaps (all my own design)

The trick here is way the radiator is mounted and the fan setup. The radiator is mounted with the bottom being closer tot he front of the car than the top, which means that the radiator fans are pointing slightly down. These fans also are very heavy and the motors they use are high torque, which means that these fans will pull a lot of air through the core. Don't be fooled by air flow specs from some fan manufacturers that are at rated at zero resistance . The best indicator of a motor's strength is its current draw, these SPAL fans pull almost 20 amps EACH.

With the above setup I have been in idling traffic on 107F deg days for over 2 hours and the car's temp does not move. In addition, the fans only come on for a short burst and then turn off. This tells me that the radiator needs minimal airflow to maintain the car's temperature, thereby indicating it is indeed a very efficient unit. I am using the EECV to trigger the fans and there is a three relay twin speed setup that the EECV controls...i.e. slow speed at temp A and High speed at Temp B. The twin fans also make the job easier by pulling a lot of air across the majority of the core area. This is why twin fans are better than one. A single large would only pull 2000-2400 cfm which is OK but not enough when the going gets really hot

They were my learnings and am I am wrapped with the result. The cost of this setup was high..but an overheating car that cant handle temp is a waste as a daily driver. The car needs to be OEM levels in this department so research your setup and invest wisely

Also as a side note...I have not ducted anything or have any hood vents, I didn't need to !!

See my build thread for some pics...


Last edited by engineer; 03-12-2018 at 10:57 PM.
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