What'd you guys do, cut up the core support and then buy second hand NASCAR takeoff radiators?

 

Definitely not a turn key solution. It's an aftermarket Ford "race radiator" (Northern brand but there are many others, all priced similarly). It's the smallest version- 22" wide, including end tanks. Single pass cross flow- but you can upgrade all the way to triple pass. I had a double the first time around and wanted to move the inlet so went single this time around. What I didn't consider was the fill boss was moved and this interfered with a hood support - but was easily remedied with some cutting. The prior double pass arrangement worked without hood mods, but would not accommodate this large oil cooler. The oil cooler is from a Mercedes W123 diesel (BEHR) which were selling on eBay clean/used for around $40. But prices indicate they have been discovered. Metric fittings were swapped out for AN. Factory "loop" brackets on the oil cooler were used to mount it to the radiator end tank. The assembly was mounted as one- similar to the stock rad using rubber isolated hangers and studs. Radiator is designed with fore/aft mounting flanges top/bottom - so it's quite easy to adapt a mounting solution that does not require a welder (how I did it the last time). It fits without any mods to the Miata except for any bracketry. Mount it with the base at the stock under tray and it will poke over the core support by about 3" and the hood shuts fine (19" tall). You do need to consider inlet/outlet options and how to interface with Miata parts. The first unit I purchased from a circle track shop and they allowed me to specify the inlet/outlet sizes when ordering- still wasn't much over $150 delivered.

Radiator example (cheaper on eBay): https://www.amazon.com/Speedway-Moto...T6/ref=sr_1_10

 

hows the hood clearance on it?

 

In my case the filler cap/boss interfered with the hood rib. I opted to cut the rib, but could have also removed the filler, sealed it shut and put a filler inline with the hose. Otherwise no interference. The double pass has the filler on the other end tank and it did not interfere with the hood at all.

 

Mine didn't require hood alteration. I got a really thick triple pass. Inlet and outlet on correct sides but I didn't special order them Miata size. I was originally thinking I would adapt them or something. I'm tight with a guy who welds aluminum for a living so he fixed them and put mounting wings on it. Then I paid too much to have somebody at a circle track race shop build a good fan shroud for my giant Spal. It's also yuuuge. It sucks up dogs and small children if they get too close. You'll love it. It's great. Everyone thinks so. It was made in America and I made Mexico pay for it. They did. It's true.

 

That top oil connector is a sharp bend - just on principle I would've used a more curved connector.

 

That's the exact brand I used on my build, the Mopar application has the outlets in the correct location. The outlets are the wrong size so you do need to come up with adapters or cut and weld. I went with a wider version (27" I think) that just slipped between the frame rails. Like what was said it's a tall MF'r, I went full retard and laid it down but there were a ton of other reasons why I did that.

 

This is a good point. Those machined 90°'s have 4x the restriction of a tube-style 90° bend fitting . If 90° is needed, go tube-style.

 

I used that 90 as a holdover while the car was being built. Now that the intake tubing is sorted/completed, I have a tube 45° to use there.



This was the prior double pass radiator install that did not have any interference with the hood. The problem was the filler "bump out" that blocked the oil cooler from being mounted at a proper height.

 

I am new tracking my miata and recently just got back from Road Atlanta. After reviewing some footage and data, I would like to address a slight temp issue. With ambient temps being mid 60's F the highest coolant temp I repeatedly recorded was 212 F, but mostly operated between 208-210 during hot laps. I am not too alarmed at this but would like to see is about 10 degrees lower. I was pushing coolant into the reservoir, but once it cooled back down it would return. This is a 99 1.8l N/A car, 01+ header, gutted exhaust, nothing crazy. Stock radiator, stock routing.

After reading through this thread I have come up with a plan of action.

-work on ducting between bodywork and stock radiator to seal it off (check temps)

-perform flush and replace with 80% distilled water mixture, possibly replace tstat and cap (check temps)

-perform reroute (check temps)

-crossflow radiator (check temps)

If temps haven't dropped by now, just burn it.. Does this seem like the most sane path to approach?

 

After the crossflow radiator you can add an external oil cooler if you still need cooling capacity.

 

.

 

Reroute prevents uneven cooling and hotspots. I would definitely do a reroute.

 

I would honestly start with the reroute and ducting and give it a try before you replace the radiator. The temps you're seeing weren't that bad in fact I would argue the factory thermostat was just getting opened up all the way at 210. If you want to run at 200 it might be as simple as running a 180deg thermostat so it's wide open by 200. The reroute is just a good idea no matter what.

 

^All of this

 

Someone will tell me why im a retard im sure, but here goes..

The reroute doesnt change the temperature distribution in the engine by much at all, quite a few people have run sensors front and rear on stock setups and found no more than a couple of degrees difference, the real key is that water which travels right through the engine past all of the cylinders and exhaust ports in the heads water galleries enters the radiator MUCH hotter.
Since heat transfer rate is a function of the Delta T (the difference in temperature) the bigger the difference you can get between 2 transfer mediums the better. In this case were talking about the water entering the radiator, and the ambient airflow through the radiator. the bigger the temp difference the higher the rate of heat transfer. This is actually why your car stays cool easier on a colder day, because the ambient air has a larger Delta T when its cold because your cooling system temperature is relatively fixed but ambient isnt.

The other way to get hotter water out is to underdrive the water pump. While this makes the water hotter when it hits the radiator it quickly cools down and then spends a bunch of time in the radiator with a low Delta T because its being pumped slowly. So the right way is to have the water flow fast, through the engine straight past ALL of the hot stuff.

Dann

 

I'm having a hard time understanding how the water could be any hotter leaving the engine and the rear temp be within a few degrees of the front.

I'll share that quite a few times when a piston is cooked it's #4 that lets go first. Mazda also saw it worth their while to redesign the head gasket in 01' up engines to redirect water to the rear cylinders.

 

Do you have this data?

I'll gladly be proven wrong

 

Thanks for the advice guys, I'll go forward with replacing the tstat, full fluid flush, and work on ducting and see where that gets my temps to.

 

I have to disagree with that assessment. Higher radiator flow will decrease coolant temp. Generally, the higher the coolant flow (in a forced convection heat exchanger), the better the heat transfer. In a worst case low flow situation, the coolant leaves the engine in thermal equilibrium. Meaning is can no longer accept any more heat, as heat transfers from a hotter source to a cooler source. Once you increase flow to a point past thermal equilibrium, your engine outlet coolant temp will be cooler than the internal engine temp, meaning the coolant is capable of accepting more heat. This trend will continue until you reach the radiator's limit to reject heat or your water pump begins cavitating. Between engine thermal equilibrium and radiator thermal equilibrium, as engine flow increases your engine outlet coolant temp will decrease.