So I'm trying to get my parts in order and learn what I don't know before I get started. I am putting a roughly 250 horse Turbo motor in my 99 Miata. It currently has a stock cooling system with a new mishimoto radiator. At the very least it needs all new hoses and a water pump when I do the timing belt. I'm thinking that due to the heat of the turbo it would probably be in my best interest to upgrade to silicone hoses wouldn't it? I also see a lot of back and forth about coolant reroutes, with no definitive answer on whether or not it would be a good idea. Living in the south where surface temps are often 100 plus degrees and building the car for being used hard with the air conditioning on I want to have an Overkill cooling system. What do I look for and what do I need to know? This is also going to be done on a challenge budget, however the good stuff is the goal.
The coolant reroute is definitely a good idea, the stock Miata coolant routing is just bad and the only downside of the reroute is cost. Silicone hoses stand up to heat better but have some downsides too (like coolant slowly escaping THROUGH the hose over time) so you may only want to upgrade hoses that are near the turbo or other hot parts. Adding heat shielding to the turbo is always a good idea too.
Also IIRC the NA/NB Mishimoto rad is the 2-row that they somehow managed to make less effective than the stock 1-row radiator, so don't expect that to be a cooling power upgrade.
In reply to Dusterbd13-michael :
I ran my old supercharged NB on a fairly new stock radiator. It was only making 6 PSI, so was under 200HP though.
Get a quality coolant reroute AND a crossflow radiator, so the radiator inlet is in the right place. I've had both the supermiata and the FM crossflow, they are both really nice and you can't really go wrong. But yeah you want the coolant inlet all the way on the right side of the radiator, and the crossflow has the end tanks on the, well, ends of the radiator, so that's where the coolant inlet is. Yay. Otherwise the coolant hose doesn't line up.
I'm going to say, personally, I needed more. I've had a reroute for ages and it just hasn't been enough for the severest duty. I do run the car pretty hard. What has really helped has been injecting straight water or mostly water with a small amount of ethanol/methanol, and adding an oil cooler. I have the track dog racing kit, I like how it's really tucked out of the way. I use the AEM 1.5 gallon water injection system, and it's been way less hassle than one might think.
Aside from the obvious "good radiator" and "coolant reroute", optimizing a Miata cooling system is about airflow. You want every scrap of air that comes through the nose to go through the radiator, so building good ducting up front is critical. OEM ducting won't work with a front mount intercooler. You also need the OEM bellypan or something equivalent, this is important for keeping the pressure behind the radiator from rising and blocking airflow through it.
If you have an AC condensor it becomes much harder.
Some people swear by hood vents, but I did not need them even running 340 rwhp at the track.
Fans and shrouds are really about optimizing cooling at low speeds and do very little when going faster than 25 mph or so.
Mishimoto products in general are junk, IME. The best radiator made for a turbo Miata was the trackspeed cross-flow one, but AFAIK they are no longer available.
How to do a coolant re-route on the cheap:
KIA Sephia water neck, paired with the $100 machined part from Moss, and a stock Miata thermostat. There are various hoses from the FLAPS that will work with some trimming. You can make the block offs for the front of the block with flat stock easily.
I've been thinking about machining the block myself out of a chunk of aluminum to adapt the Miata head to the Sephia water neck.
Also on the cheap, I understand the auto Miata is an upgrade from the standard. Of course, the suggestions above are better.
There's only one reroute that is actually designed to work with a turbo. Most of them dump the hot water from the turbo straight back into the block, and it's a significant percentage of the total heat load in the system. The FM reroute makes sure it goes through the radiator before being fed back into the system. There are some other attributes as well, but that one's huge.
Remember, you're trying to get heat from the engine into the coolant (part of the intent of the reroute), get the hot water to the radiator (water pump, proper plumbing for the turbo water) and then transfer the heat to the air. The solution for each is different. To transfer heat to the air, you need an efficient core and you need lots of airflow across it. Making sure the high pressure side of the airflow everyone understands, that's all the ducting in the nose and maybe a splitter. But to really pump air across it, you want air extraction as well. The good thing is that holes in a hood are pretty cheap :)
codrus, you'd be surprised at how slow the airflow is across the radiator core even at speed. NASCARs run fans, and they're sure not going under 25 mph at any point. I had a Miata with cooling problems on the interstate and I tried a bunch of different things on it. The one that made the difference was a fan upgrade. Proper hood venting would probably have done the trick, but that's a one way street.
Trackspeed has indeed shut down, but I will point out that it was an FM crossflow that won the 25hrs of Thunderhill with Trackspeed's owner driving ;)
When you change all the hoses don't forget the heater hoses and the small hoses to the oil cooler and intake manifold.
One of these blows out and you have big trouble.
Ask me how I know.
